Method for manufacturing air filter material, air filter material, filter pack, and air filter unit

Abstract

Provided are a method for manufacturing an air filter material, an air filter material, a filter pack, and an air filter unit, whereby deterioration of functions during joining can be suppressed. A method for manufacturing a filter material for an air filter includes: a first step of preparing a porous membrane and an air-permeable membrane; and a second step in which the porous film and the air-permeable film are bonded using a hot-melt adhesive in a molten state, in which the temperature of the air-permeable film is lower than the temperature of the hot-melt adhesive in the molten state.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a method for manufacturing an air filter medium, an air filter medium, a filter pack, and an air filter unit. BACKGROUND

[0002] In the past, for example, a porous membrane (hereinafter, sometimes referred to as a PTFE porous membrane) made of polytetrafluoroethylene (hereinafter, sometimes referred to as PTFE) has been used as an air filter. The PTFE porous membrane has a high dust capturing efficiency at the same pressure loss as compared with a filter medium made of glass fiber, and thus is particularly suitable for use in a HEPA filter (high efficiency particulate air filter) or a ULPA filter (ultra low penetration air filter).

[0003] As such a filter, for example, an air filter medium in which a PTFE porous membrane and a gas permeable support are laminated has been proposed, as described in Patent Literature 1 (Japanese Patent Application Publication No. 2009-297702). SUMMARY

[0004] PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] Here, the air filter medium described in the above Patent Literature 1 is manufactured by heat laminating the PTFE porous membrane and the gas permeable support as a whole using a pair of heated rollers after heating.

[0006] However, in the heat lamination process in which the heated rollers are used as such, any function in the layer constituting the filter medium can be deteriorated by heat. Therefore, it is desirable to suppress the deterioration of the function at the time of joining to be small.

[0007] MEANS FOR SOLVING THE PROBLEMS

[0008] The method for manufacturing an air filter medium according to the first aspect includes a first step of preparing a porous membrane and a gas permeable membrane, and a second step of bonding the porous membrane and the gas permeable membrane using a hot melt adhesive in a molten state. In the second step, the temperature of the gas permeable membrane is lower than the temperature of the hot melt adhesive in the molten state.

[0009] In addition, the gas permeable membrane is not particularly limited, and for example, can be a nonwoven fabric.

[0010] According to the method for manufacturing an air filter medium, the porous membrane and the gas permeable membrane are joined while the temperature of the gas permeable membrane is lower than the temperature of the hot melt adhesive in the molten state, and thus the deterioration of the function of the gas permeable membrane is suppressed.

[0011] The manufacturing method of the air filter medium of the second viewpoint is the manufacturing method of the air filter medium of the first viewpoint, wherein either one of the porous membrane and the air permeable membrane is any one of a melt-blown nonwoven fabric, a spun-bond nonwoven fabric, or a membrane containing one or more than two selected from the group consisting of an antibody, an antibacterial agent, and a mildew preventive agent.

[0012] Here, in the case where either one of the porous membrane and the air permeable membrane contains the melt-blown nonwoven fabric or the spun-bond nonwoven fabric, wrinkles are likely to occur due to heat when the porous membrane and the air permeable membrane are laminated, and thus uniform bonding can be difficult. In contrast, according to the manufacturing method of the air filter medium, since heating of the melt-blown nonwoven fabric or the spun-bond nonwoven fabric is suppressed, uniform bonding of the porous membrane and the air permeable membrane is possible.

[0013] Further, in the case where either one of the porous membrane and the air permeable membrane contains the antibody such as a protein, the antibody such as a protein is likely to be modified due to heat, and thus the function of the antibody can be reduced or lost. However, according to the manufacturing method of the air filter medium, modification of the antibody due to heat is suppressed, and thus reduction in the function of the antibody is suppressed to a small extent.

[0014] Further, in the case where either one of the porous membrane and the air permeable membrane contains the antibacterial agent or the mildew preventive agent, the antibacterial agent or the mildew preventive agent is likely to be modified due to heat, and thus the function of the antibacterial agent or the mildew preventive agent can be reduced or lost. However, according to the manufacturing method of the air filter medium, modification of the antibacterial agent or the mildew preventive agent due to heat is suppressed, and thus reduction in the function of the antibacterial agent or the mildew preventive agent is suppressed to a small extent.

[0015] The manufacturing method of the air filter medium of the third viewpoint is the manufacturing method of the air filter medium of the first viewpoint or the second viewpoint, wherein the porous membrane is a polytetrafluoroethylene porous membrane.

[0016] In the manufacturing method of the air filter medium, a high-performance air filter medium can be manufactured.

[0017] The manufacturing method of the air filter medium of the fourth viewpoint is the manufacturing method of the air filter medium of any one of the first to third viewpoints, wherein the air permeable membrane contains one or more than two selected from the group consisting of polyethylene terephthalate (PET), polyethylene (PE), polyphenylene sulfide (PPS), polypropylene (PP), and polyamide (PA).

[0018] Further, for the air filter medium including the air permeable membrane, the amount of total organic carbon (TOC) of the air filter medium per unit area that is detached from the air filter medium by passing inert gas through the air filter medium heated to 40°C for 60 minutes is preferably 1000 pg / m2 The following.

[0019] The manufacturing method of the air filter medium of the fifth aspect is the manufacturing method of the air filter medium of any one of the first to fourth aspects, and the porous membrane and the air permeable membrane are adhered by the fibrous hot melt adhesive.

[0020] In the manufacturing method of the air filter medium, the hot melt adhesive is fibrous, and thus the pressure loss of the obtained air filter medium can be suppressed to be small.

[0021] The manufacturing method of the air filter medium of the sixth aspect is the manufacturing method of the air filter medium of the fifth aspect, and in the second process, the hot melt adhesive in a molten state is discharged from a nozzle, and air flow having a speed faster than the discharge speed of the hot melt adhesive from the nozzle is used to extend the hot melt adhesive, thereby fiberizing the hot melt adhesive.

[0022] In the manufacturing method of the air filter medium, fiberization of the hot melt adhesive becomes easy.

[0023] The manufacturing method of the air filter medium of the seventh aspect is the manufacturing method of the air filter medium of the fifth or sixth aspect, and a plurality of fibrous hot melt adhesives are arranged in a length direction common manner.

[0024] In addition, it is preferable that the plurality of fibers of the adhesive do not overlap each other, or the number of intersection points of each fiber is three or less.

[0025] In the manufacturing method of the air filter medium, the plurality of fibers of the hot melt adhesive are suppressed from overlapping each other. Thereby, the porous membrane and the air permeable membrane can be uniformly adhered, and occurrence of partial peeling is suppressed.

[0026] In addition, in the case where the air filter medium is subjected to pleat processing, peeling of the air permeable membrane from the porous membrane at the time of the pleat processing is suppressed.

[0027] The manufacturing method of the air filter medium of the eighth aspect is the manufacturing method of the air filter medium of any one of the first to seventh aspects, and the hot melt adhesive has a melt viscosity of 1000 mPa s or more and 2500 mPa s or less at 180°C.

[0028] In the manufacturing method of the air filter medium, coating in a molten state becomes easy.

[0029] The manufacturing method of the air filter medium of the ninth aspect is the manufacturing method of the air filter medium of any one of the first to eighth aspects, and the hot melt adhesive is one or two or more selected from the group consisting of a polyolefin-based resin and a polyamide-based resin.

[0030] Here, from the viewpoint of improving the adhesion, the one or two or more hot melt adhesives selected from the group consisting of a polyolefin-based resin and a polyamide-based resin are preferably used together with the fluororesin porous membrane.

[0031] In the manufacturing method of the air filter medium, the porous membrane and the air permeable membrane are favorably adhered.

[0032] The manufacturing method of the air filter medium of the tenth aspect is the manufacturing method of the air filter medium of any one of the first to ninth aspects, and the average fiber diameter of the porous membrane, the average fiber diameter of the adhesive, and the average fiber diameter of the air permeable membrane are represented by the average fiber diameter of the porous membrane: the average fiber diameter of the adhesive: the average fiber diameter of the air permeable membrane = 1 / 2000 to 1 / 30: 1 to 6: 1.

[0033] In addition, the average fiber diameter of the porous membrane may be, for example, 30 nm or more and 150 nm or less. Furthermore, the average fiber diameter of the adhesive may be, for example, 20 μm or more and 60 μm or less. Furthermore, the average fiber diameter of the air permeable membrane may be, for example, 5 μm or more and 30 μm or less.

[0034] In the manufacturing method of the air filter medium, the case where the fibers of the adhesive cannot intervene between the porous membrane and the air permeable membrane due to the fibers of the adhesive entering between the fibers of the air permeable membrane, resulting in a portion where the adhesive cannot function, is suppressed, and the air resistance of the fibers of the adhesive in the obtained air filter medium is suppressed to be small.

[0035] The manufacturing method of the air filter medium of the eleventh aspect is the manufacturing method of the air filter medium of any one of the first to tenth aspects, and after the second step, the sheet having the porous membrane, the hot melt adhesive, and the air permeable membrane is passed between a pair of rollers. When passing between the rollers, a pressure of 0.3 MPa or more and 0.6 MPa or less is applied to the sheet.

[0036] According to the manufacturing method of the air filter medium, the adhesion of the porous membrane and the air permeable membrane is improved.

[0037] The air filter medium of the twelfth aspect is the air filter medium manufactured by the manufacturing method of the air filter medium of any one of the first to eleventh aspects.

[0038] The deterioration of the function of the air filter medium is suppressed.

[0039] The filter pack of the thirteenth aspect is the air filter medium of the twelfth aspect and is formed in a shape in which the peak folds and the valley folds are folded out.

[0040] The air filter unit of the fourteenth aspect includes: the air filter medium or the pleated filter medium manufactured according to the manufacturing method of any one of the first aspect to the twelfth aspect, the pleated filter medium being the air filter medium manufactured according to the manufacturing method of any one of the first aspect to the twelfth aspect and formed in a shape in which the peak folds and the valley folds are folded out; and a frame. The frame holds the air filter medium or the pleated filter medium.

[0041] The air filter medium of the fifteenth aspect includes a porous membrane, a breathable membrane, and a hot melt adhesive. The hot melt adhesive bonds the porous membrane and the breathable membrane. In the breathable membrane, the degree of deformation of the fibers of the portion of the breathable membrane on the side opposite the porous membrane is smaller than the degree of deformation of the fibers of the portion of the breathable membrane on the side of the porous membrane due to heat.

[0042] In the air filter medium, the degree of functional deterioration of the fibers of the portion of the breathable membrane on the side opposite the porous membrane due to heat is suppressed. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 is a schematic cross-sectional view showing a layer structure of an air filter medium (one).

[0044] Figure 2 is a schematic cross-sectional view showing a layer structure of an air filter medium (two).

[0045] Figure 3 is a schematic cross-sectional view showing a layer structure of an air filter medium (three).

[0046] Figure 4 is a schematic appearance perspective view of a filter pack.

[0047] Figure 5 is a schematic appearance perspective view of an air filter unit.

[0048] Figure 6 is a schematic configuration view of an adhesive application process.

[0049] Figure 7 is a view showing an example of an application shape of fibers of an adhesive.

[0050] Figure 8 is a view showing another example of an application shape of fibers of an adhesive. DETAILED DESCRIPTION

[0051] Hereinafter, an air filter medium, a filter pack, an air filter unit, and a method for manufacturing the same will be described by way of example.

[0052] (1) Air filter medium

[0053] The air filter medium includes a porous membrane, a gas permeable membrane, and a fibrous adhesive that bonds the porous membrane and the gas permeable membrane.

[0054] The average fiber diameter of the porous membrane, the average fiber diameter of the adhesive, and the average fiber diameter of the gas permeable membrane preferably satisfy the relationship of the average fiber diameter of the porous membrane : the average fiber diameter of the adhesive : the average fiber diameter of the gas permeable membrane = 1 / 2000 to 1 / 30 : 1 to 6 : 1.

[0055] As the adhesive, an adhesive having an average fiber diameter that is more than one time the average fiber diameter of the gas permeable membrane is used, thereby suppressing the entry of the fibers of the adhesive into the fibers of the gas permeable membrane. More preferably, the average fiber diameter of the adhesive is more than 2.0 times the average fiber diameter of the gas permeable membrane. As the adhesive, an adhesive having an average fiber diameter that is less than six times the average fiber diameter of the gas permeable membrane is used, thereby suppressing the increase rate of the pressure loss due to the fibers of the adhesive itself to a small degree. In addition, preferably, in the adhesive, the weight ratio of the number of the adhesive having a fiber diameter that is more than the average fiber diameter of the gas permeable membrane to the total number of the fibers of the adhesive is more than 90% by weight.

[0056] Further, as the adhesive, an adhesive having an average fiber diameter that is more than 30 times the average fiber diameter of the porous membrane is used, thereby suppressing the influence of the fibers of the adhesive on the filter performance of the porous membrane to a small degree. Further, as the adhesive, an adhesive having an average fiber diameter that is less than, for example, 2000 times the average fiber diameter of the porous membrane is used, thereby easily suppressing the increase rate of the pressure loss due to the fibers of the adhesive itself to a small degree.

[0057] In addition, as the gas permeable membrane, a gas permeable membrane having an average fiber diameter that is more than 30 times the average fiber diameter of the adhesive is used, thereby easily supporting the porous membrane by the gas permeable membrane even in the case where the porous membrane is difficult to stand by itself due to thinness or the like, and the rigidity of the air filter medium can be improved.

[0058] In addition, the average fiber diameter of the porous membrane can be calculated as a number average fiber diameter by randomly selecting 50 fibers from the image of a scanning electron microscope photograph. Further, the average fiber diameter of the adhesive and the average fiber diameter of the gas permeable membrane can be evaluated by taking as an object the fibers present within a prescribed range of the image observed using a microscope or the like, for example, as a number average fiber diameter of 200 fibers.

[0059] From the viewpoint of suppressing the fibers of the adhesive from entering between the fibers of the air permeable film, the average fiber diameter of the adhesive is preferably 20 μm or more, and more preferably 30 μm or more. In addition, in the case where the adhesive is used for the adhesion of a porous film having an average fiber diameter of 30 nm or more and 150 nm or less, from the viewpoint of suppressing the increase rate of the pressure loss due to the presence of the fibers of the adhesive, the average fiber diameter is preferably 60 μm or less, and can be 55 μm or less.

[0060] The average length of the fibers of the adhesive is not particularly limited, but can be, for example, 100 times or more the average fiber diameter of the adhesive, and is preferably 500 times or more the average fiber diameter of the adhesive.

[0061] In the case where a virtual line of 1 cm in length is drawn in a direction orthogonal to the length direction of any one of the plurality of fibers of the adhesive, it is preferable that the average number of fibers of the adhesive intersecting the virtual line be two or more and three or less. The average number can be, for example, an average value calculated with any 200 fibers of the adhesive as the object. By arranging the plurality of fibers of the adhesive in a staggered manner, the fibers of the adhesive can be suppressed from overlapping each other, and the adhesion sites of the porous film and the air permeable film can be arranged uniformly. In addition, since the average number of fibers of the adhesive intersecting the virtual line of 1 cm in length is two or more, when a force is applied to the porous film or the air permeable film, stress can be suppressed from concentrating on a particular adhesion site, and the adhesion state can be easily maintained favorably. For example, in the case where the joint of the porous film and the air permeable film is subjected to pleat processing, the porous film and the air permeable film can be suppressed from peeling off during the pleat processing. The average number of fibers of the adhesive intersecting the virtual line of 1 cm in length is three or less, and thus the increase in the pressure loss of the air filter medium is suppressed.

[0062] In addition, in the case where the number of fibers of the adhesive is the same as in the case where the average number of fibers of the adhesive intersecting the virtual line of 1 cm in length is the same, the greater the average fiber diameter of the fibers of the adhesive, the greater the coating amount per unit area (g / m2) tends to be. However, as described later, it has been clarified that the increase rate of the pressure loss due to the fibers of the adhesive covering the porous film tends to increase significantly compared to the increase rate of the coating amount per unit area of the adhesive. Therefore, from the viewpoint of sufficiently suppressing the increase rate of the pressure loss, the average fiber diameter of the adhesive is more preferably 1000 times or less the average fiber diameter of the porous film.

[0063] When viewed along the thickness direction of the air filter media, the adhesive fibers preferably do not overlap, or the number of intersections between each fiber is three or fewer. Furthermore, the number of intersections between adhesive fibers refers to the average number of intersections between each adhesive fiber and its own fibers, as well as other adhesive fibers. While not specifically limited, this can be calculated as the average number of intersections on 100 adhesive fibers in any given area. More preferably, the number of intersections between adhesive fibers on each fiber is two or fewer. While it is possible to bond the porous membrane and the ventilated membrane at locations where adhesive fibers overlap when viewed along the thickness direction of the air filter media, the gap between the porous membrane and the ventilated membrane widens at these overlapping areas. Therefore, it is difficult to achieve sufficient bonding between the porous membrane and the ventilated membrane around these overlapping areas. Consequently, areas where the porous membrane floats relative to the ventilated membrane may occur, making it difficult to ensure a uniform bonding state across the entire membrane. Therefore, it is preferable to have fewer overlapping areas between the adhesive fibers. Furthermore, even in cases where overlapping areas of adhesive fibers occur, a good bond can be achieved by adequately distributing the adhesive fibers around these overlapping areas. However, in such cases, the amount of adhesive required for bonding the porous membrane to the breathable membrane increases, leading to increased pressure loss in the air filter media.

[0064] When viewed along the thickness direction of the air filter media, it is preferable that the length directions of the multiple fibers of the adhesive are each in a predetermined direction and parallel to each other. This prevents the fibers of the adhesive from easily overlapping.

[0065] When viewed along the thickness direction of the air filter media, it is preferable that the shape of the adhesive fibers is wavy, having both peaks and valleys. Furthermore, it is preferable that more than half of the adhesive fibers are wavy, having both peaks and valleys; more preferably, more than 90% are wavy, having both peaks and valleys.

[0066] When viewed along the thickness direction of the air filter media, it is preferable that the shape of the adhesive is a shape other than one that creates overlapping between the fiber portions on a single adhesive, for example, preferably not a spiral and not a random coating shape.

[0067] From the viewpoint of improving the adhesion between the porous membrane and the air permeable membrane, the amount of the adhesive between one porous membrane and one air permeable membrane is preferably 1 g / m2or more, and more preferably 2 g / m2or more, when viewed in the thickness direction of the air filter medium. In addition, from the viewpoint of suppressing an increase in pressure loss due to the presence of adhesive fibers, the amount of the adhesive between one porous membrane and one air permeable membrane is preferably 5 g / m2or less, and more preferably 4 g / m2or less, when viewed in the thickness direction of the air filter medium.

[0068] From the viewpoint of suppressing an increase in the total organic carbon (TOC) of the air filter medium, the adhesive preferably mainly includes at least either of a polyolefin-based resin and a polyamide-based resin, and preferably mainly consists of a polyolefin-based resin. In addition, it is preferably not a rubber-based adhesive or an acrylic adhesive. The weight ratio of the polyolefin-based resin in the adhesive is, for example, 70% or more, and preferably 90% or more. In addition, from the viewpoint of suppressing an increase in pressure loss due to an excessively large fiber diameter of the adhesive, the melt viscosity at 180°C of the adhesive is preferably 2500 mPa s or less, and more preferably 2200 mPa s or less. In addition, from the viewpoint of suppressing a state in which the discharged fibers are cut midway, thereby easily obtaining continuously extending fibers and easily controlling the coating position, the melt viscosity at 180°C of the adhesive is preferably 1000 mPa s or more, and more preferably 1500 mPa s or more. In addition, from the viewpoint of suppressing deterioration of the adhesive, the heating temperature at the time of melting the adhesive is preferably 250°C or less, and more preferably 200°C or less.

[0069] In addition, in the case where the adhesive is coated in a manner of ensuring a peeling strength of the porous membrane and the air permeable membrane in the air filter medium of 0.1 N / 35 mm or more, it is preferable that the increase rate of pressure loss obtained from the pressure loss of a laminate obtained by stacking the porous membrane and the air permeable membrane without using the adhesive, and the pressure loss of the air filter medium obtained by joining the porous membrane and the air permeable membrane using the adhesive, is 10% or less, and more preferably 7% or less, and further preferably 6% or less. Here, the increase rate of pressure loss is calculated by the following formula.

[0070] Increase rate of pressure loss (%) = (pressure loss of air filter medium / pressure loss of laminate) x 100 - 100

[0071] The porous membrane is, for example, preferably 30 nm or more and 150 nm or less in average fiber diameter. Thereby, it is possible to improve the collection efficiency of the air filter medium.

[0072] The porous membrane is not particularly limited, and can be a melt-blown nonwoven fabric, a spun-bond nonwoven fabric, a membrane including an antibody, or the like, but is mainly composed of a fluororesin, and is preferably a fluororesin porous membrane having a porous membrane structure in which fibrils (fibers) and nodes (nodal portions) connected to the fibrils are present. Here, "mainly" means that the fluororesin is present in the largest amount among the components. The fluororesin porous membrane can contain, for example, 50% by weight or more of the fluororesin, preferably 80% by weight or more of the fluororesin, and more preferably 95% by weight or more of the fluororesin, with respect to the weight of the fluororesin porous membrane, or can be composed only of the fluororesin. Thus, an air cleaner filter material having sufficient performance can be obtained. Furthermore, even in a use in which a high performance is required for the air cleaner filter material, such as a case in which the porous membrane is a fluororesin porous membrane, the amount of generation of TOC can be suppressed.

[0073] As the component other than the fluororesin included in the fluororesin porous membrane, for example, an inorganic filler, which is a non-melt-processable component that does not undergo fiberization, can be given.

[0074] The fluororesin for the fluororesin porous membrane can be composed of one component, or can be composed of two or more components. Furthermore, as the fluororesin, for example, a fluororesin containing PTFE that can undergo fiberization can be given. Furthermore, as the fluororesin, a mixture of three components, namely, PTFE that can undergo fiberization, a non-heat-melt-processable component that does not undergo fiberization, and a component that does not undergo fiberization and can be heat-melt-processed, which has a melting point lower than 320°C, can be given. In addition, the melting point can be measured using a DSC (differential scanning calorimeter), and is represented as an endothermic peak therein. Furthermore, in the case of a substance that is an amorphous structure and for which the melting point is not clear, a softening point can be used instead. The softening point is grasped as the temperature at which the slope of a DTA curve first changes using differential thermal analysis (DTA).

[0075] PTFE that can undergo fiberization is high-molecular-weight PTFE obtained by emulsion polymerization or suspension polymerization of tetrafluoroethylene (TFE). The high-molecular-weight, as used herein, means a substance that easily undergoes fiberization at the time of stretching at the time of production of the porous membrane, and that obtains fibrils having a long fiber length, and has a standard specific gravity (SSG) of 2.130 to 2.230 and a high melt viscosity, and thus means a molecular weight that is substantially non-melt-flowable. Whether or not the PTFE can undergo fiberization can be judged by whether or not paste extrusion can be performed, which is a representative method of molding high-molecular-weight PTFE powder produced from a polymer of TFE. In the case where the unmolded molded body obtained by the paste extrusion has no substantial strength or elongation, for example, in the case where the elongation is 0% and the molded body is broken if stretched, the PTFE can be regarded as having no fiberization. The high-molecular-weight PTFE can be a modified polytetrafluoroethylene, or a homopolymer polytetrafluoroethylene, or a mixture of a modified PTFE and a homopolymer PTFE.

[0076] As the non-heat-melt processable component that does not undergo fiberization, a component having thermoplasticity such as low-molecular-weight PTFE, a thermosetting resin, an inorganic filler, and a mixture thereof can be given. The low-molecular-weight PTFE is a component having an exponential 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~7.0x10 5 Pa s of PTFE.

[0077] The non-heat-melt processable component that does not undergo fiberization having a melting point of less than 320°C preferably exhibits a melt viscosity of less than 10,000 Pa s at 380°C. The melting point of the non-heat-melt processable component that does not undergo fiberization is the peak top of the following melting heat curve obtained by using a differential scanning calorimeter (DSC) to warm up to above the melting point at a rate of 10°C / min to completely melt once, and to cool down to below the melting point at a rate of 10°C / min, and then to warm up again at a rate of 10°C / min.

[0078] These PTFEs that can undergo fiberization, non-heat-melt processable components that do not undergo fiberization, and non-heat-melt processable components that do not undergo fiberization having a melting point of less than 320°C can be used, for example, as described in detail in International Publication No. 2020 / 067182 or the like.

[0079] Further, in the method for producing a fluororesin porous membrane, fine powder or the like obtained by coagulation, co-coagulation, or the like after emulsion polymerization of TFE is used, a liquid lubricant (extrusion aid) is mixed after dehydration and drying, and paste extrusion is performed, thereby obtaining an extrudate in a sheet shape. Then, the extrudate in a sheet shape is calendered by a calender roll or the like to obtain an un-baked membrane, the liquid lubricant is removed from the un-baked membrane, and stretching is performed, thereby enabling a fluororesin porous membrane to be obtained.

[0080] The fluororesin porous membrane thus obtained preferably has a pressure loss of 300 Pa or less when air is passed at a flow rate of 5.3 cm / sec. In addition, the pressure loss of the fluororesin porous membrane is not particularly limited, but can be 50 Pa or more.

[0081] The fluororesin porous membrane can have a particle capture efficiency of 99.00% or more, and preferably 99.99% or more, when air including NaCl particles having a particle diameter of 0.1 pm is passed at a flow rate of 5.3 cm / sec.

[0082] Further, the PF value of the fluororesin porous membrane is preferably 20 or more. The PF value is a value determined using the pressure loss and the trapping efficiency grasped by NaCl particles having a particle diameter of 0.1 μm and by the following formula: PF value = { -log((100 - trapping efficiency (%)) / 100)} / (pressure loss (Pa) / 1000).

[0083] Further, the thickness of the fluororesin porous membrane is, for example, 1.0 μm or more and preferably 3.0 μm or more. By increasing the film thickness of the fluororesin porous membrane, the dust storage amount can be increased. Further, the film thickness of the fluororesin porous membrane is, for example, 300 μm or less and preferably 200 μm or less. The thickness of the fluororesin porous membrane can be grasped by, for example, using a film thickness gauge (1D-110MH type, manufactured by Mitsutoyo Corporation), overlapping five of the measurement objects and measuring the entire film thickness, and dividing the value by 5 to obtain the film thickness of one sheet.

[0084] Further, in the case where the porous membrane is a fluororesin porous membrane, the adhesive preferably includes at least any one of a polyolefin-based resin and a polyamide-based resin from the viewpoint of good adhesion to the fluororesin porous membrane and the ability to suppress the amount of total organic carbon (TOC) of the air filter medium to a small amount.

[0085] The air permeable membrane is, for example, preferably a melt-blown nonwoven fabric, a spun-bond nonwoven fabric, or a membrane including one or two or more selected from the group consisting of an antibody, an antibacterial agent, and a mildew preventive agent.

[0086] Here, the melt-blown nonwoven fabric or the spun-bonded nonwoven fabric can support the porous membrane, or can function as a pre-capturing layer by being disposed on the upstream side of the porous membrane. Further, as the membrane including an antibody, for example, there can be a membrane carrying an antibody. As the antibody, it is preferable to capture at least one harmful substance selected from bacteria, molds, viruses, and allergens. As the bacteria, for example, there can be Staphylococcus (Staphylococcus aureus or Staphylococcus epidermidis), Micrococcus, Bacillus anthracis, Bacillus cereus, Bacillus subtilis, Propionibacterium acnes, or the like as Gram-positive bacteria, or Pseudomonas aeruginosa, Serratia marcescens, Burkholderia cepacia, Streptococcus pneumoniae, Legionella, Mycobacterium tuberculosis as Gram-negative bacteria. As the molds, for example, there can be Aspergillus, Penicillium, Cladosporium, Fusarium, Alternaria. As the viruses, there can be influenza virus, coronavirus (SARS virus), adenovirus, rhinovirus. As the allergens, there can be pollen, mite allergen, cat allergen. As the membrane including an antibacterial agent, for example, there can be a membrane carrying an antibacterial agent. As the antibacterial agent, there can be an organic antibacterial agent, for example, an interfacial active agent-based antibacterial agent, an alcohol-based antibacterial agent, an imidazole-based antibacterial agent, an antibacterial agent using a natural product-derived substance such as hinokitiol, and the like. As the membrane including a mold inhibitor, for example, there can be a membrane carrying a mold inhibitor. As the mold inhibitor, there can be an organic mold inhibitor, for example, an interfacial active agent-based mold inhibitor, an alcohol-based mold inhibitor, an imidazole-based mold inhibitor, a mold inhibitor using a natural product-derived substance such as hinokitiol, and the like.

[0087] Further, in the case of bonding the porous membrane and the air permeable membrane, the melt-blown nonwoven fabric or the spun-bonded nonwoven fabric shrinks due to heat, and thus wrinkles can easily occur, and uniform bonding can be difficult. In particular, in the case of bonding the porous membrane and the air permeable membrane by heating to a temperature exceeding the softening point of at least a part of the resin constituting the air permeable membrane, shrinkage or the occurrence of wrinkles due to heat becomes significant. In contrast, according to the method for manufacturing an air cleaner filter medium, since heating of the melt-blown nonwoven fabric or the spun-bonded nonwoven fabric is suppressed, uniform bonding of the porous membrane and the air permeable membrane can be performed. For example, even in the case of using an air permeable membrane that shrinks to 95% or less of the area due to heating at a temperature exceeding the softening point, uniform bonding can be performed according to the method for manufacturing an air cleaner filter medium. Further, in the case of wrinkles occurring due to heat in the case of bonding the porous membrane and the air permeable membrane, in the case of further processing the article obtained by bonding the porous membrane and the air permeable membrane into a pleated shape, it can be difficult to achieve a uniform pleated shape. In contrast, according to the method for manufacturing an air cleaner filter medium, reduction in uniformity in pleat processing is suppressed.

[0088] In addition, in the case where the melt-blown nonwoven fabric or the spun-bonded nonwoven fabric is subjected to heat lamination, the density of the fabric can change due to heat shrinkage, which can cause an increase in pressure loss. In contrast, according to the production method in which the melt-blown nonwoven fabric or the spun-bonded nonwoven fabric is not actively heated, the increase in pressure loss is suppressed.

[0089] In addition, in the case of a film including an antibody such as a protein, the antibody such as a protein is generally modified at a temperature exceeding 80°C, which can reduce or even eliminate the function of the antibody. In contrast, according to the production method in which the film including an antibody such as a protein is not actively heated, the reduction in the function of the antibody can be suppressed.

[0090] In addition, in the case of a film including an antibacterial agent or a mold-proof agent, particularly in the case where the film includes an organic antibacterial agent or an organic mold-proof agent, the antibacterial agent or the mold-proof agent is generally modified at a high temperature such as 80°C, which can reduce or even eliminate the function of the antibacterial agent or the mold-proof agent. In contrast, according to the production method in which the film is not actively heated, the reduction in the function of the antibacterial agent or the mold-proof agent can be suppressed. In addition, as the antibacterial agent or the mold-proof agent, a known antibacterial agent or mold-proof agent whose function is reduced or even eliminated by heating at a temperature exceeding 100°C, or a known antibacterial agent or mold-proof agent whose function is reduced or even eliminated by heating at a temperature exceeding 120°C can be used.

[0091] In the case where the air permeable film is used as a support layer for supporting a porous film, the average fiber diameter thereof is preferably 5 μm or more and 30 μm or less, and more preferably 10 μm or more and 25 μm or less. Thus, while the porous film is sufficiently supported, an increase in pressure loss due to an excessively large fiber diameter of the air permeable film is suppressed.

[0092] In the case where the air permeable film is used as a pre-capturing layer disposed on the upstream side of the air flow with respect to the porous film, the average fiber diameter thereof is preferably 0.5 μm or more and 10.0 μm or less. Thus, dust collection load on the porous film can be dispersed, and early clogging of the porous film is suppressed.

[0093] The air permeable film can include one or two or more selected from the group consisting of polyethylene terephthalate (PET), polyethylene (PE), polyphenylene sulfide (PPS), polypropylene (PP), and polyamide (PA). The air permeable film can be a melt-blown nonwoven fabric, a spun-bond nonwoven fabric, or the like. Also, for the air filter filter medium using the air permeable film, the amount of total organic carbon (TOC) per unit area of the air filter filter medium that is detached from the air filter filter medium by passing an inert gas through the air filter filter medium heated to 40°C for 60 minutes is preferably 1000 μg / m2or less, more preferably 500 μg / m2or less. In addition, even if the air permeable film containing a component that generates an organic gas in a high-temperature environment is used, since the joining of the porous film and the air permeable film is performed using an adhesive, and the air permeable film does not need to be heated to a molten state, an increase in the amount of total organic carbon due to heating of the air permeable film is suppressed.

[0094] The air permeable film is preferably not a core-sheath structure fiber including a core portion and a sheath portion having a lower melting point than the core portion, but is composed of fibers having a uniform cross-sectional structure.

[0095] The air permeable film preferably has flame retardancy. Specifically, the air permeable film preferably exhibits flame retardancy equivalent to HF-1 in the UL94-HF method. In addition, the air filter filter medium is obtained by joining the porous film and the air permeable film using an adhesive, and the air permeable film does not need to be brought to a molten state to be joined, so it is easy to select an air permeable film exhibiting flame retardancy as the air permeable film of the air filter filter medium.

[0096] The pressure loss of the air permeable film when air is passed at a flow rate of 5.3 cm / sec, for example, is preferably 10 Pa or less.

[0097] The particle collection efficiency of the air permeable film when air including NaCl particles having a particle diameter of 0.1 μm is passed at a flow rate of 5.3 cm / sec can be 10% or less, preferably 5% or less.

[0098] In addition, even if a plurality of air permeable films are used, the preferred physical properties of the air permeable films are the same for each air permeable film.

[0099] Further, as described above, since the porous film and the air permeable film are joined by an adhesive, either layer does not need to be partially molten to be joined, and the selection of the material of the porous film or the material of the air permeable film is not easily limited.

[0100] (2) Layer structure of air filter filter medium

[0101] The layer structure of the air filter filter medium is not particularly limited.

[0102] For example, the air filter filter medium can beFigure 1 As shown in the air filter element 30, the porous membrane 31 and the first air permeable membrane 32 are stacked in the air flow direction, and the adhesive 38 is located between the porous membrane 31 and the first air permeable membrane 32. As shown in the air filter element 30, the first air permeable membrane 32 can be provided on the lower wind side of the porous membrane 31, and as shown in the air filter element 30, the first air permeable membrane 32 can be provided on the upper wind side of the porous membrane 31. In addition, as shown in the air filter element 30, the air filter element can include the first air permeable membrane 32 stacked on the porous membrane 31 on the air flow direction side and the second air permeable membrane 33 stacked on the porous membrane 31 on the side opposite to the first air permeable membrane 32, and the porous membrane 31 is supported from both the lower wind side and the upper wind side. In this case, it is preferable that the adhesive 38 be located between the porous membrane 31 and the first air permeable membrane 32, and the adhesive 38 be located between the porous membrane 31 and the second air permeable membrane 33. Figure 1 As shown in the air filter element 30, the first air permeable membrane 32 can be provided on the lower wind side of the porous membrane 31, and as shown in the air filter element 30, the first air permeable membrane 32 can be provided on the upper wind side of the porous membrane 31. In addition, as shown in the air filter element 30, the air filter element can include the first air permeable membrane 32 stacked on the porous membrane 31 on the air flow direction side and the second air permeable membrane 33 stacked on the porous membrane 31 on the side opposite to the first air permeable membrane 32, and the porous membrane 31 is supported from both the lower wind side and the upper wind side. In this case, it is preferable that the adhesive 38 be located between the porous membrane 31 and the first air permeable membrane 32, and the adhesive 38 be located between the porous membrane 31 and the second air permeable membrane 33. Figure 2 As shown in the air filter element 30, the first air permeable membrane 32 can be provided on the lower wind side of the porous membrane 31, and as shown in the air filter element 30, the first air permeable membrane 32 can be provided on the upper wind side of the porous membrane 31. In addition, as shown in the air filter element 30, the air filter element can include the first air permeable membrane 32 stacked on the porous membrane 31 on the air flow direction side and the second air permeable membrane 33 stacked on the porous membrane 31 on the side opposite to the first air permeable membrane 32, and the porous membrane 31 is supported from both the lower wind side and the upper wind side. In this case, it is preferable that the adhesive 38 be located between the porous membrane 31 and the first air permeable membrane 32, and the adhesive 38 be located between the porous membrane 31 and the second air permeable membrane 33. Figure 3 As shown in the air filter element 30, the first air permeable membrane 32 can be provided on the lower wind side of the porous membrane 31, and as shown in the air filter element 30, the first air permeable membrane 32 can be provided on the upper wind side of the porous membrane 31. In addition, as shown in the air filter element 30, the air filter element can include the first air permeable membrane 32 stacked on the porous membrane 31 on the air flow direction side and the second air permeable membrane 33 stacked on the porous membrane 31 on the side opposite to the first air permeable membrane 32, and the porous membrane 31 is supported from both the lower wind side and the upper wind side. In this case, it is preferable that the adhesive 38 be located between the porous membrane 31 and the first air permeable membrane 32, and the adhesive 38 be located between the porous membrane 31 and the second air permeable membrane 33.

[0103] The air filter element can also be one in which the air permeable membrane is stacked on the lower wind side of the porous membrane, and a pre-capture layer as another example of the air permeable membrane is stacked on the upper wind side of the porous membrane. In this case, the pre-capture layer on the more upstream side is caused to bear the dust collection load acting on the porous membrane, and thus early clogging of the porous membrane can be suppressed.

[0104] (3) Physical properties of the air filter element

[0105] The pressure loss of the air filter element can be, for example, 400 Pa or less, and is preferably 300 Pa or less. In addition, the pressure loss of the air filter element is not particularly limited, but can be 50 Pa or more. The pressure loss of the air filter element can be measured as the pressure loss when air is passed at a flow rate of 5.3 cm / sec.

[0106] The particle collection efficiency of the air filter element when air including NaCl particles having a particle diameter of 0.1 μm is passed at a flow rate of 5.3 cm / sec can be 99.00% or more, and is preferably 99.99% or more.

[0107] As the air filter element, the PF value is preferably, for example, 20 or more, wherein the PF value is determined using the pressure loss and the collection efficiency of NaCl particles having a particle diameter of 0.1 μm and using the following formula: PF value = { -log((100 - collection efficiency (%)) / 100)} / (pressure loss (Pa) / 1000).

[0108] The thickness of the air cleaner filter material is preferably, for example, 350 μm or more. In addition, in the case where the air cleaner filter material is used in a state having a folding portion, the thickness of the air cleaner filter material is preferably, for example, 1000 μm or less, more preferably 750 μm or less, from the viewpoint of suppressing the thickness of the folding portion from being too large. The thickness of the air cleaner filter material is the value of the thickness when a load of 0.3 N is applied to the measurement object in a specific measurement device.

[0109] In addition, in the air cleaner filter material, it is preferable that the average fiber diameter of the porous membrane be 30 nm or more and 150 nm or less, the average fiber diameter of the adhesive be 20 μm or more and 60 μm or less, and the average fiber diameter of the air permeable membrane be 5 μm or more and 30 μm or less.

[0110] (4) Filter pack

[0111] Next, referring to Figure 4 , the filter pack (pleated filter material) of the present embodiment will be described.

[0112] Figure 4 is an external perspective view of the filter pack 20 of the present embodiment.

[0113] The filter pack 20 includes the air cleaner filter material (for example, the air cleaner filter material 30) described above. The air cleaner filter material of the filter pack 20 is a finished filter material obtained by processing into a zigzag shape (pleating processing) in which the outer fold and the inner fold are alternately repeated. The pleating processing can be performed, for example, by a rotary folding machine. The folding width of the air cleaner filter material is not particularly limited, and is, for example, 25 mm or more and 280 mm or less. By performing the pleating processing, the filter pack 20 can increase the folded area of the air cleaner filter material when used in the air cleaner unit, and thus, an air cleaner unit having a high trapping efficiency can be obtained.

[0114] The filter pack 20 can further include a spacer (not shown) for maintaining the pleat interval when used in the air cleaner unit, in addition to the air cleaner filter material. The material of the spacer is not particularly limited, but a hot melt resin can be preferably used. In addition, the air cleaner filter material 30 can have a plurality of embossed protrusions, and the pleat interval can be maintained by the embossed protrusions.

[0115] (5) Air cleaner unit

[0116] Next, referring to Figure 5 , the air cleaner unit 1 will be described.

[0117] Figure 5 is an external perspective view of the air cleaner unit 1 of the present embodiment.

[0118] The air cleaner unit 1 includes the air cleaner filter or filter pack described above, and a frame 25 that holds the air cleaner filter or filter pack (pleated filter). The air cleaner unit 1 can be produced by holding the air cleaner filter that has not been folded in the frame, or by holding the filter pack 20 in the frame 25. Figure 5 The air cleaner unit 1 shown is produced using the filter pack 20 and the frame 25.

[0119] The frame 25 is produced, for example, by combining sheets or by molding resin, and the filter pack 20 and the frame 25 are preferably sealed by a sealant. The sealant is used to prevent leakage between the filter pack 20 and the frame 25, and can be, for example, a sealant made of epoxy, acrylic, polyurethane, or the like.

[0120] The air cleaner unit 1 including the filter pack 20 and the frame 25 can be a micro-pleated air cleaner in which one filter pack 20 extending in a flat sheet shape is held inside the frame 25, or a V-bank air cleaner unit or a single-bank air cleaner unit in which a plurality of filter packs extending in flat sheet shapes are held in alignment in the frame.

[0121] (6) Examples of Use

[0122] The air cleaner filter, filter pack, and air cleaner unit of the present embodiment are used, for example, in the following uses.

[0123] ULPA filter (ultra-low penetration air filter) (for semiconductor manufacturing), HEPA filter (for hospitals, semiconductor manufacturing), cylindrical cartridge filter (for industry), bag filter (for industry), heat-resistant bag filter (for exhaust gas treatment), heat-resistant pleated filter (for exhaust gas treatment), SINBRAN (registered trademark) filter (for industry), catalyst filter (for exhaust gas treatment), filter with adsorbent (for HDD installation), ventilation filter with adsorbent (for HDD installation), ventilation filter (for HDD installation, etc.), filter for vacuum cleaner (for vacuum cleaner), general-purpose multi-layer felt material, cartridge filter for gas turbine (compatible product for gas turbine), cooling filter (for electronic device frame), and the like.

[0124] Freeze-drying materials such as containers for freeze-drying, automotive ventilation materials for electronic circuits and lamps, container applications for container lids and the like, protective ventilation applications for electronic devices and the like, medical ventilation applications, and the like in the field of ventilation / inner pressure adjustment.

[0125] Masks of flat, pleated, three-dimensional, and the like (for suppressing the intrusion of dust, oil smoke, bacteria, viruses, and the like into the body through the mouth and nose of a person).

[0126] (7) Method for manufacturing air filter medium

[0127] In the method for manufacturing an air filter medium, a first step of preparing a porous membrane and a gas permeable membrane; and a second step of bonding the porous membrane and the gas permeable membrane using a hot melt adhesive in a molten state, wherein the temperature of the gas permeable membrane is lower than the temperature of the hot melt adhesive in the molten state.

[0128] Thus, in the second step, the porous membrane and the gas permeable membrane are joined while the temperature of the gas permeable membrane is lower than the temperature of the hot melt adhesive in the molten state. Therefore, the gas permeable membrane is prevented from being exposed to high temperature, and thus, deformation of the gas permeable membrane is suppressed, and thus, deterioration of the function of the gas permeable membrane is suppressed.

[0129] For example, there is a joining method in which the porous membrane and the gas permeable membrane are joined, and the gas permeable membrane is melted by sandwiching both from the outside in the thickness direction with a hot roller, and thus, the porous membrane and the gas permeable membrane are joined. However, in this joining method, the surface of the gas permeable membrane on the side of the porous membrane needs to be melted, and thus, the surface of the gas permeable membrane on the side opposite to the side of the porous membrane, which is heated by the hot roller pressed against the surface on the side of the porous membrane, is brought to a further melted state. Thus, the function of the gas permeable membrane before the joining step can be lost. Specifically, the fiber diameter of the gas permeable membrane greatly changes, and thus, the pressure loss can increase. Further, the fiber diameter of the gas permeable membrane greatly changes, and thus, the supporting function of the porous membrane can decrease. Further, for the gas permeable membrane including an antibody or the like which loses the function at high temperature, the function of the antibody or the like can be deteriorated or lost.

[0130] In contrast, in the above-described method for manufacturing an air filter medium, in the second step, the temperature of the gas permeable membrane is maintained lower than the temperature of the hot melt adhesive in the molten state, and thus, deterioration of the function of the gas permeable membrane or the like is suppressed.

[0131] Further, since the hot melt adhesive in the molten state at a temperature higher than the temperature of the gas permeable membrane is applied to the gas permeable membrane, the fiber in the portion of the gas permeable membrane where the hot melt adhesive is applied can be deformed to some extent by the heat of the hot melt adhesive, but the deformation occurs only in the vicinity of the surface of the gas permeable membrane where the adhesive is applied, and the deformation of the fiber is suppressed in the inside of the gas permeable membrane or in the vicinity of the surface opposite to the surface where the adhesive is applied. Thus, the deformation of the fiber is suppressed in most of the thickness direction of the gas permeable membrane.

[0132] Furthermore, the same applies to porous membranes. Deformation may occur only near the surface on the side bonded to the adhesive due to contact with the molten hot-melt adhesive, but deformation is suppressed in the portion away from the adhesive. Additionally, in the case of porous membranes, such as those made of fluoropolymer porous membranes with a melting point higher than that of the adhesive, the effect of fiber deformation in the porous membrane is suppressed.

[0133] The above-mentioned combination of porous membranes and breathable membranes is, for example, as follows Figure 6 As shown, a porous membrane roller 61 wound into a roll shape can be used. Here, the case where the breathable membranes 32 and 33 are bonded to the two surfaces of the porous membrane 31 via an adhesive 38 is described as an example. In addition, the porous membrane 31 can be a fluoropolymer porous membrane extending in both the longitudinal and width directions.

[0134] exist Figure 6 In the illustrated apparatus, a porous membrane 31, sequentially fed from a porous membrane roller 61, is supplied to a silicone rubber clamping roller 64 via roller 74. Furthermore, a first breathable membrane 32, sequentially fed from a first breathable membrane roller 62, is supplied to a temperature regulating roller 65 via rollers 71, 72, and 73. After passing roller 73 and before reaching the temperature regulating roller 65, adhesive 38 discharged from a hot melt gun 68 is applied to the surface of the first breathable membrane 32 that is bonded to the porous membrane 31. The temperature regulating roller 65 adjusts the temperature to maintain the adhesive force of the adhesive 38 applied to the first breathable membrane 32. The first breathable membrane 32 and the porous membrane 31 are bonded by passing between the temperature regulating roller 65 and the silicone rubber clamping roller 64 with adhesive 38 in between. The resulting sheet formed by the bonding of the first breathable membrane 32 and the porous membrane 31 is then supplied to the silicone rubber clamping roller 67 via rollers 75, 76, and 77. Furthermore, the second breathable membrane 33, sequentially fed from the second breathable membrane roller 63, is supplied to the temperature regulating roller 66 via rollers 78, 79, and 80. After passing roller 80 and before reaching the temperature regulating roller 66, adhesive 38 discharged from the hot melt gun 68 is applied to the surface of the second breathable membrane 33 that is joined with the porous membrane 31. The temperature regulating roller 66 adjusts the temperature so that the adhesive 38 applied to the second breathable membrane 33 can maintain its adhesive strength. The second breathable membrane 33 and the porous membrane 31 are joined together by passing between the temperature regulating roller 66 and the silicone rubber clamping roller 67 with adhesive 38 in between. As described above, the sheet formed by joining the first breathable membrane 32, the porous membrane 31, and the second breathable membrane 33 is processed into a product via rollers 81, 82, 83, 84, 85, 86, and 87 and wound onto the product roller 69.

[0135] In addition, the adhesive is preferably applied in a molten state. Here, in order to suppress hardening of the adhesive on the breathable film, the breathable film is preferably warmed in advance. Even in this case, heating above the melting point of the breathable film is not performed, and, for example, the breathable film is preferably warmed using temperature-adjusting rollers 65, 66 at a temperature of 35°C or higher and 70°C or lower, more preferably 40°C or higher and 60°C or lower. Thus, melting of the breathable film is suppressed, and deformation of the fibers of the breathable film is suppressed. In addition, even if the breathable film includes a component that can emit an organic gas due to heat, since melting of the breathable film is suppressed, emission of the organic gas from the breathable film is suppressed. In addition, from the same viewpoint, the breathable film is preferably one that does not become a molten state even when heated by the temperature-adjusting rollers 65, 66 and is joined to the porous film.

[0136] In addition, although the hot-melt adhesive is heated to a molten state at the time of application, it is preferably not heated again after application. Thus, for the hot-melt adhesive, by suppressing the heating history to be small, even if the hot-melt adhesive includes a component that generates an organic gas due to heat, generation of the organic gas can be suppressed.

[0137] Application of the adhesive is preferably performed using an applicator. As the applicator, one having a plurality of aligned discharge nozzles, and the molten resin discharged from each discharge nozzle is extended by an air current that is conveyed at a speed faster than the discharge speed around each nozzle toward the discharge direction, thereby achieving a desired fiber diameter to perform application. Here, by lowering the melt viscosity of the molten resin, the adhesive becomes easy to extend, and thus, the fiber diameter can be made finer. In addition, by increasing the speed of the air current, the adhesive becomes easy to extend, and thus, the fiber diameter can be made finer.

[0138] The shape of the application of the adhesive is not particularly limited, but, as shown in Figs. 1 and 2, in order to make the direction perpendicular to the conveyance direction of the breathable film 32 the lengthwise direction of the fibers of the adhesive, the application is preferably performed in a manner such that a plurality of adhesive fibers are arranged. As shown in Fig. 3, the shape of the application of the adhesive can also be wavy, in which peak portions that project in a direction intersecting the lengthwise direction of the fibers of the adhesive and valley portions that project on the side opposite the peak side in the direction intersecting the lengthwise direction of the fibers of the adhesive are alternately arranged. In addition, as shown in Fig. 4, it can also be wavy in which peak portions and valley portions are alternately arranged in a manner having portions extending in a direction intersecting the lengthwise direction of the fibers of the adhesive. Figure 7 Figure 8 Figure 7 Figure 8

[0139] ​​​​As described above, the breathable membranes 32 and 33 coated with adhesive are overlapped with the porous membrane 31 and pressure is applied by the clamping rollers 64 and 67. At this time, the air filter material 30 is obtained by pressing the breathable membranes 32 and 33 against the porous membrane 31. Here, from the viewpoint of suppressing the increase in pressure loss due to pressure during lamination, the pressure applied by the clamping rollers 64 and 67 to the laminate of the porous membrane and the breathable membrane attached with adhesive is preferably, for example, 0.6 MPa or less. Furthermore, from the viewpoint of easily ensuring a good bonding state, the pressure applied by the clamping rollers 64 and 67 to the laminate of the porous membrane and the breathable membrane with adhesive is preferably, for example, 0.3 MPa or more. This pressure can be measured, for example, using a pressure measuring membrane (pressure-sensitive paper manufactured by Fujifilm Corporation) as the instantaneous pressure during passage between the rollers. In addition, it is preferable that the temperature of the clamping rollers 64 and 67 is not heated above the melting point of the breathable membranes 32 and 33.

[0140] Furthermore, in manufacturing methods where the porous membrane obtained by extension is directly transported and moved to the process of bonding the ventilating membrane without being rolled into a roll, the air filter media including the ventilating membrane, which has a thickness, needs to be formed into a roll for storage, thus occupying space. In contrast, as described above, if the porous membrane in its unbonded state is rolled into a roll for storage, and a bonding process is performed when the filter media with the ventilating membrane needs to be bonded to obtain the filter media and then shipped, space saving can be achieved.

[0141] Furthermore, when melting and bonding the breathable membrane to the porous membrane, the heating process using heated rollers until the fibers of the breathable membrane become molten takes a considerable amount of time. Therefore, bonding the breathable membrane to the porous membrane by applying an adhesive allows for a shorter bonding time. Here, during the manufacture of the porous membrane, when a predetermined time is spent stretching to obtain the porous membrane, the time required for bonding the porous membrane to the breathable membrane is sometimes shorter than the time required for stretching the porous membrane. Therefore, assuming a manufacturing method where the stretched porous membrane is directly transported to the bonding process of the breathable membrane without being wound into a roller, the stretching process of the porous membrane becomes a so-called speed-limiting step. In contrast, if a manufacturing method pre-prepares a large number of space-saving porous membrane rollers and performs the bonding process with the breathable membrane while feeding out the wound porous membrane, air filter media can be obtained quickly while saving space.

[0142] Example

[0143] The following examples and comparative examples are shown, and the contents of this disclosure are described in detail.

[0144] In Example 1, an adhesive was used to bond a fluoropolymer porous membrane obtained in the manner described below to a breathable membrane, thereby obtaining an air filter material.

[0145] First, 300g of hydrocarbon oil (IPSolvent2028 manufactured by Idemitsu Kosan Co., Ltd.) was added to 1kg of PTFE fine powder (Polyflon fine powder F106 manufactured by Daikin Industries, Ltd.) at 20°C as an extrusion liquid lubricant and mixed. Next, the mixture was extruded using a slurry extrusion apparatus to obtain a cylindrical molded body. This cylindrical molded body was then formed into a sheet using calendering rollers heated to 70°C, thus obtaining a fluoropolymer sheet. The fluoropolymer sheet was then passed through a hot air drying oven at 250°C to evaporate and remove the hydrocarbon oil, resulting in a strip-shaped unburned fluoropolymer sheet with an average thickness of 200μm and an average width of 150mm.

[0146] Next, the unfired fluoropolymer sheet is stretched along its length at a stretch ratio of 5. The stretching temperature in the length direction is 250°C. Here, the stretching ratio (% / s) along the length direction is 150 (% / s).

[0147] Next, using a tenter frame capable of continuous clamping, the unburnt fluoropolymer sheet was stretched along its width at a stretching ratio of 30 times at a stretching temperature of 350°C to obtain a fluoropolymer porous membrane. The fluoropolymer porous membrane was then wound onto a porous membrane roller. Here, the average fiber diameter of the obtained fluoropolymer porous membrane was 69 nm.

[0148] Then, while the fluoropolymer porous membrane is being fed out from the porous membrane roller, a breathable membrane coated with adhesive is stacked on the downwind side of the fluoropolymer porous membrane in the direction of airflow. The breathable membrane is then bonded to the fluoropolymer porous membrane by a clamping roller, thereby obtaining the air filter material of Example 1.

[0149] In addition, the breathable membrane used in Example 1 is a spunbond nonwoven fabric made of PET (average fiber diameter of 11 μm, unit area weight of 40 g / m², and thickness of 230 μm).

[0150] Furthermore, the adhesive used in Example 1 has a melt viscosity of 1600 (mPa) at 180°C. s) olefin hot melt resin (manufactured by Asahi Chemicals (Asahi Chemicals), product number: Asahi Melt FR921).

[0151] The adhesive was applied to the breathable membrane using an ITW Dynatec coating machine at a linear velocity of 30 m / min. The coating machine consisted of multiple nozzles with parallel nozzle directions for adhesive discharge. During coating, the airflow velocity was controlled to be faster than the adhesive discharge velocity, resulting in the extended adhesive fibers forming a wave pattern and being coated onto the breathable membrane. The nozzle tip opening size was 0.43 μm², the air outlet size was 0.64 μm², and the center-to-center distance between the nozzles was 1.6 mm. The pump speed for delivering the molten adhesive heated to 180°C was set to 6.4%, and air heated to 190°C was supplied at a flow rate of 3000 cm³ / min to extend the adhesive fibers after the molten adhesive was discharged from the nozzles. The adhesive coated in the above manner has an average fiber diameter of 48.7 μm and an adhesive coating amount of 3.2 g / m².

[0152] Furthermore, in Example 1, there are no locations where the fibers of the multiple adhesives substantially overlap each other. Additionally, in Example 1, when an imaginary line of 1 cm in length is drawn in a direction orthogonal to the length direction of any one of the multiple fibers of the adhesive, the average number of adhesive fibers intersecting the imaginary line is 2.5. Furthermore, in Example 1, the clamping pressure when the breathable membrane is bonded to the fluoropolymer porous membrane by the clamping roller is 0.40 Pa.

[0153] In addition, in Example 1, in order to prevent the adhesive from hardening before the breathable membrane and the fluoropolymer porous membrane are bonded, a temperature regulating roller is used to heat the breathable membrane to 40°C for adhesive coating.

[0154] For Example 1 above, the peel strength (N / 35mm) of the bonded porous membrane and the breathable membrane was measured to be 0.15 (N / 35mm). Furthermore, the peel strength was measured using the 180-degree peel test method according to JIS Z 0237:2009, employing a precision universal testing machine manufactured by Shimadzu Corporation, with a test piece of 35mm width and a tensile speed of 100mm / min (the same applies below). In addition, the increase rate of pressure loss accompanying the bonding of the porous membrane and the breathable membrane was calculated, and the result in Example 1 was 5.7%.

[0155] Example 2 is the same as Example 1 except for the following: a melt viscosity of 2050 mPa is used at 180°C. The hot melt resin (manufactured by Asahi Chemicals, product number: AsahiMeltFR530) had an average fiber diameter of 42.6 μm, an adhesive coating amount of 3.0 g / m², and a clamping pressure of 0.55 Pa. For Example 2 above, the peel strength (N / 35 mm) of the bonded porous membrane and breathable membrane was measured to be 0.15 (N / 35 mm). Furthermore, the increase in pressure loss in Example 2 was 1.5%.

[0156] Example 3 is identical to Example 2 except for the following: the material of the breathable membrane is changed to PET material copolymerized with a phosphorus flame retardant (average fiber diameter 12 μm, unit area weight 50 g / m², thickness 260 μm), the average fiber diameter of the adhesive is 45.8 μm, the adhesive coating amount is 3.1 g / m², and the clamping pressure is 0.45 Pa. For Example 3 above, the peel strength (N / 35 mm) of the bonded porous membrane and breathable membrane was measured to be 0.15 (N / 35 mm). Furthermore, the increase in pressure loss in Example 3 is 2.7%.

[0157] Example 4 is the same as Example 1 except for the following: Compared to Example 1, the hot melt resin of the adhesive is changed to one with a melt viscosity of 2500 mPa at 180°C. The Tohmide 1310 adhesive, manufactured by Fuji Chemical Industries (Fuji Chemical Industries), has an average fiber diameter of 54.3 μm, an adhesive coating amount of 3.4 g / m², and a clamping pressure of 0.45 Pa. For Example 4 above, the peel strength (N / 35 mm) of the bonded porous membrane and the breathable membrane was measured to be 0.17 (N / 35 mm). Furthermore, the increase in pressure loss in Example 4 was 7.7%.

[0158] Example 5 is the same as Example 1 except for the following: a melt viscosity of 4000 mPa is used at 180°C. The hot melt resin (manufactured by Henkel, product number: TECHNOMELT MP801) had an average fiber diameter of 71.6 μm, an adhesive coating amount of 4.2 g / m², and a clamping pressure of 0.55 Pa. For Example 5 above, the peel strength (N / 35 mm) of the bonded porous membrane and the breathable membrane was measured to be 0.2 (N / 35 mm). Furthermore, the increase in pressure loss in Example 5 was 15.8%.

[0159] Example 6 is the same as Example 1 except for the following: a melt viscosity of 4100 mPa is used at 180°C. The hot melt resin (manufactured by Asahi Chemicals, product number: AsahiMeltFR561) had an average fiber diameter of 98.3 μm, an adhesive coating amount of 4.8 g / m², and a clamping pressure of 0.50 Pa. For Example 6 above, the peel strength (N / 35 mm) of the bonded porous membrane and breathable membrane was measured to be 0.25 (N / 35 mm). Furthermore, the increase in pressure loss in Example 6 was 17.2%.

[0160] Furthermore, the above embodiments confirmed the following tendency: as the average fiber diameter of the adhesive increases, the rate of increase in pressure loss due to the adhesive fibers covering the porous membrane significantly increases. In particular, a comparison of Embodiments 2 and 5 with the same clamping pressure shows that the rate of increase in pressure loss significantly increases with the increase in the average fiber diameter of the adhesive.

[0161] Furthermore, as Example 7, the filter material obtained was the same as that in Example 1 above, except for the following: a melt viscosity of 2300 mPa at 180°C was used. The filter media used was a synthetic rubber-based hot melt resin (Sanyo Life Materials 939S), with an average fiber diameter of 102.2 μm, an adhesive coating amount of 4.7 g / m², and a clamping pressure of 0.55 Pa. In this Example 7 filter media, the increase in pressure loss was 43.1%.

[0162] Furthermore, Example 8 is the same as Example 1 except for the following: a melt viscosity of 1600 mPa is used at 180°C. The hot melt resin (manufactured by Asahi Chemicals, product number: AsahiMeltFR921) had an average fiber diameter of 45.3 μm, an adhesive coating amount of 3.1 g / m², and a clamping pressure of 0.75 Pa. In the filter media of Example 8, the increase in pressure loss was 23.1%.

[0163] Furthermore, Example 9 is the same as Example 1 except for the following: a melt viscosity of 2050 mPa is used at 180°C. The hot melt resin (manufactured by Asahi Chemicals, product number: AsahiMeltFR530) had an average fiber diameter of 43.7 μm, an adhesive coating amount of 3.0 g / m², and a clamping pressure of 0.90 Pa. In the filter media of Example 9, the increase in pressure loss was 50.8%.

[0164] In Example 10, an air filter material identical to that of Example 1 was obtained except for the following: a PP-based hot-melt adhesive was used as the adhesive, and the adhesive was applied using a coating machine with multiple nozzles discharging the adhesive in random directions. The average fiber diameter of the adhesive was 116 μm, and the coating amount was 5 g / m². As the support layer, a PET material copolymerized with a phosphorus-based flame retardant (average fiber diameter 12 μm, area weight 50 g / m², thickness 260 μm) was used. For Example 10, the peel strength (N / 35 mm) of the bonded porous membrane and the ventilated membrane was measured, and the porous membrane could not be peeled from the ventilated membrane, resulting in membrane breakage. In Example 10, because the adhesive fibers were randomly coated, there was significant overlap between the adhesive fibers. Specifically, in Example 10, an average of 5 overlaps were observed between the adhesive fibers on each individual adhesive fiber. In Example 10, although the adhesion was so strong that the membrane ruptured during the peel strength test, the increase in pressure loss was 39.2%.

[0165] According to Examples 1-10 above, when bonding the fluoropolymer porous membrane to the nonwoven fabric, direct heating of the fluoropolymer porous membrane and the nonwoven fabric by rollers can be avoided. Therefore, when the fluoropolymer porous membrane or the nonwoven fabric includes the specified functions, its functions are prevented from deteriorating due to heat.

[0166] Regarding the aforementioned increase rate of pressure loss, the increase rate of pressure loss associated with the bonding was determined by measuring the pressure loss of the laminated product in which the porous membrane and the ventilated membrane only overlap but are not bonded to each other, and the pressure loss of the air filter material after the porous membrane and the ventilated membrane are bonded by an adhesive.

[0167] (Pressure loss of laminated products before bonding)

[0168] The test sample, in which only the permeable membrane is stacked on the porous membrane without bonding them, is placed on a filter holder with a diameter of 100 mm. The inlet side is pressurized with a compressor, and the air permeation flow rate is adjusted to 5.3 cm / s using a flow meter. The pressure loss at this point is then measured using a pressure gauge.

[0169] (Pressure loss of the air filter media after assembly)

[0170] A test sample of air filter media, obtained by bonding a porous membrane and a breathable membrane with an adhesive, was placed on a filter holder with a diameter of 100 mm. The inlet side was pressurized with a compressor, and the air permeation flow rate was adjusted to 5.3 cm / s using a flow meter. Then, the pressure loss at this time was measured using a pressure gauge.

[0171] (Increase in pressure loss)

[0172] Based on the pressure loss of the laminated product and the pressure loss of the air filter media measured in the above manner, the increase rate of pressure loss is calculated according to the following formula.

[0173] Increase in pressure loss (%) = (Pressure loss of air filter media / Pressure loss of laminated products) × 100 - 100

[0174] In addition, as a comparative example 1, an air filter material was obtained by thermally laminating the same fluoropolymer porous membrane as in Example 1 with a core-sheath nonwoven fabric (spunbond nonwoven fabric manufactured by PT MULTI SPUNINDO JAYA) with PE as the core and PET as the sheath.

[0175] In addition, as a comparative example 2, an air filter material was obtained by thermally laminating the same fluoropolymer porous membrane as in Example 1 with a core-sheath nonwoven fabric (manufactured by Unitika, product number: Elves) with PE as the core and PET as the sheath.

[0176] For the air filter media of Comparative Examples 1 and 2, hot lamination was performed by pressing rollers onto the side of the fluoropolymer porous membrane opposite to the bonding surface of the nonwoven fabric and the side of the nonwoven fabric opposite to the bonding surface of the fluoropolymer porous membrane, respectively. The rollers were heated to 200°C, a temperature exceeding the melting point of the resin constituting the sheath of the nonwoven fabric. In Comparative Examples 1 and 2, since the portion opposite to the bonding surface was heated to the greatest extent, the degree of shape change on the surface of the nonwoven fabric opposite to the bonding surface was greater. Furthermore, in the air filter media of Comparative Examples 1 and 2, since the nonwoven fabric and the fluoropolymer porous membrane were exposed to high temperatures, even if the nonwoven fabric or the fluoropolymer porous membrane possessed the intended functions, those functions would deteriorate due to the heat.

[0177] Furthermore, for each air filter media of Examples 1-9 and Comparative Examples 1-2 described above, the degassing capacity was determined using the dynamic headspace method, as described below. The degassing capacity was determined by placing a 120mm × 40mm test specimen in a constant temperature bath at 40°C for 60 minutes to allow organic matter to detach from the specimen. High-purity helium gas (99.9999%) was introduced into the constant temperature bath, and the resulting gas was then passed to an adsorption tube to collect the generated organic matter. The collected organic matter was analyzed by gas chromatography-mass spectrometry (GC-MS). The degassing amounts were as follows: Example 1: 52 μg / m², Example 2: 112 μg / m², Example 3: 454 μg / m², Example 4: 150 μg / m², Example 5: 114 μg / m², Example 6: 68 μg / m², Example 7: 850 μg / m², Example 8: 60 μg / m², Example 9: 105 μg / m², Comparative Example 1: 550 μg / m², and Comparative Example 2: 814 μg / m². For Example 7, which used a synthetic rubber-based hot-melt adhesive as the binder, a particularly large increase in degassing was observed.

[0178] In addition, for each filter material of Examples 1-6 and Comparative Examples 1 and 2 above, a flammability test was conducted in the UL94-HF method. The results showed that Example 1 was equivalent to HF-1, Example 2 was equivalent to HF-1, Example 3 was equivalent to HF-1, Example 4 was equivalent to HF-1, Example 5 was equivalent to HF-1, Example 6 was equivalent to HF-1, Comparative Example 1 was equivalent to HBF, and Comparative Example 2 was equivalent to HBF.

[0179] Furthermore, as Example 11, an air filter material identical to that of Example 2 was obtained except for the following: As a breathable membrane, a spunbond nonwoven fabric (manufactured by PT MULTI SPUNINDO JAYA) with a PE core and PET sheath was coated with an antifungal agent. An organic synthetic antifungal agent (pyridine-based) was used as the antifungal agent.

[0180] Furthermore, as Comparative Example 3, an air filter material identical to that of Example 11 was obtained except for the following: While using the same fluoropolymer porous membrane and breathable membrane as in Example 11, the fluoropolymer porous membrane and breathable membrane were bonded by hot lamination without the use of an adhesive. The hot lamination of Comparative Example 3 was similar to that of Comparative Examples 1 and 2, performed by pressing rollers onto the side of the fluoropolymer porous membrane opposite to the bonding surface of the nonwoven fabric and the side of the nonwoven fabric opposite to the bonding surface of the fluoropolymer porous membrane, respectively. The rollers were heated to 200°C, a temperature exceeding the melting point of the resin constituting the sheath of the nonwoven fabric.

[0181] For Example 11 and Comparative Example 3 above, a simplified anti-mold test was conducted as part of the anti-mold test (JIS Z2911). In the simplified anti-mold test, the samples were cut into 20mm × 20mm pieces, and Cladosporium was used as the inoculum. The samples were placed on potato dextrose agar medium, and the spore suspension concentration was set at 1000 RLU (ATP was measured using Lumitester Smart manufactured by Kikkoman Biomifa Co., Ltd. as the standard for suspension concentration). The inoculum volume of the turbid liquid was set at 0.1 mL, and the samples were placed at room temperature for 8 days. The mold growth on the sample surface was observed with the naked eye.

[0182] In the simplified anti-mold test of Example 11, no mold growth was visually observed at the inoculation site. In the simplified anti-mold test of Comparative Example 3, mold growth at the inoculation site was also clearly visible to the naked eye. Furthermore, when the same anti-mold test was performed on a breathable membrane (without bonded fluoropolymer porous membrane) coated with the anti-mold agent, no mold growth at the inoculation site was visually observed in this case either.

[0183] Furthermore, as Example 12, the same air filter material as in Example 2 was obtained except for the following: as a breathable membrane, a meltblown nonwoven fabric (MPPW025 manufactured by HEIGEN) made of polypropylene (PP) was used.

[0184] Furthermore, as Comparative Example 4, an air filter material identical to that of Example 12 was obtained except for the following: the fluoropolymer porous membrane and the breathable membrane, identical to those of Example 12, were used, but the fluoropolymer porous membrane and the breathable membrane were bonded by hot lamination without the use of an adhesive. The hot lamination in Comparative Example 4 was performed by pressing a single-sided roller on the side of the nonwoven fabric opposite to the bonding surface of the fluoropolymer porous membrane, wherein the roller was heated to 150°C, a temperature exceeding the melting point of the resin constituting the sheath of the nonwoven fabric.

[0185] For Example 12, in which the breathable membrane was heated at 40°C by a temperature regulating roller, and Comparative Example 4, in which the breathable membrane was heated at 150°C by heat lamination, the size changes of samples with a specified area before and after bonding of the fluoropolymer porous membrane and the breathable membrane were measured. The results showed that no change was observed in Example 12, while in Comparative Example 4, the area shrank to about 95%, and wrinkles were formed in the air filter material obtained in Comparative Example 4.

[0186] The embodiments of this disclosure have been described above. However, it should be understood that various changes in form and detail can be made without departing from the spirit and scope of this disclosure as set forth in the claims.

[0187] Symbol Explanation

[0188] 1. Air filter unit; 20. Filter bags, pleated filter media; 25. Frame; 30. Air filter media; 31 porous membrane; 32 First ventilation membrane (ventilation membrane); 33 Secondary ventilation membrane (ventilation membrane); 38. Hot melt adhesive.

[0189] Existing technical documents

[0190] Patent documents

[0191] Patent Document 1: Japanese Patent Application Publication No. 2009-297702

Claims

1. A method for manufacturing an air filter media (30), characterized in that, include: The first step is to prepare the porous membrane (31) and the breathable membrane (32, 33); as well as The second step involves bonding the porous membrane to the breathable membrane using a molten hot melt adhesive (38). In the second process, the temperature of the breathable membrane is lower than the temperature of the molten hot melt adhesive.

2. The method for manufacturing air filter media according to claim 1, characterized in that, The porous membrane and the breathable membrane are either of the following: meltblown nonwoven fabric; spunbond nonwoven fabric; or a membrane comprising one or more of the following: antibodies, antibacterial agents, and antifungal agents.

3. The method for manufacturing air filter media according to claim 1 or 2, characterized in that, The porous membrane is a polytetrafluoroethylene porous membrane.

4. The method for manufacturing air filter media according to any one of claims 1 to 3, characterized in that, The breathable membrane comprises one or more selected from the group consisting of polyethylene terephthalate, polyethylene, polyphenylene sulfide, polypropylene, and polyamide.

5. The method for manufacturing air filter media according to any one of claims 1 to 4, characterized in that, The porous membrane is bonded to the breathable membrane using the fibrous hot-melt adhesive.

6. The method for manufacturing air filter media according to claim 5, characterized in that, In the second step, the molten hot melt adhesive is discharged from the nozzle, and an airflow with a speed faster than the discharge speed of the hot melt adhesive from the nozzle is used to extend the hot melt adhesive, thereby making the hot melt adhesive fibrous.

7. The method for manufacturing air filter media according to claim 5 or 6, characterized in that, The multiple fibrous hot melt adhesive fibers are arranged in a common manner along their length.

8. The method for manufacturing air filter media according to any one of claims 1 to 7, characterized in that, The hot melt adhesive has a melt viscosity of 1000 mPa at 180°C. s or more and 2500mPa Below s.

9. A method for manufacturing air filter media according to any one of claims 1 to 8, characterized in that, The hot melt adhesive is selected from one or more of the group consisting of polyolefin resins and polyamide resins.

10. A method for manufacturing air filter media according to any one of claims 1 to 9, characterized in that, The average fiber diameter of the porous membrane, the average fiber diameter of the adhesive, and the average fiber diameter of the breathable membrane are expressed as the ratio of average fiber diameter of the porous membrane to average fiber diameter of the adhesive to average fiber diameter of the breathable membrane = 1 / 2000 to 1 / 30: 1 to 6:

1.

11. A method for manufacturing air filter media according to any one of claims 1 to 10, characterized in that, After the second step, the sheet having the porous membrane, the hot melt adhesive, and the breathable membrane is passed between a pair of rollers. As the sheet passes between the rollers, a pressure of 0.3 Pa or more and 0.6 Pa or less is applied to the sheet.

12. An air filter media, characterized in that, The air filter media is manufactured by the manufacturing method according to any one of claims 1 to 11.

13. A filter pack (20), characterized in that, The filter pack is the air filter material of claim 12, and is formed in a shape with folded peaks and valleys.

14. An air filter unit (1), characterized in that, include: The air filter media or pleated filter media (20) manufactured by the manufacturing method according to any one of claims 1 to 12, wherein the pleated filter media is an air filter media manufactured by the manufacturing method according to any one of claims 1 to 12 and is formed into a shape with folded peaks and valleys; and The frame (25) holds the air filter media or the pleated filter media.

15. An air filter media (30), characterized in that, include: porous membrane (31); Ventilation membranes (32, 33); as well as A hot melt adhesive (38) is used to bond the porous membrane to the breathable membrane. Compared to the degree of heat-induced deformation of the fibers on the porous membrane side of the breathable membrane, the degree of heat-induced deformation of the fibers on the opposite side of the porous membrane side of the breathable membrane is smaller.

Images