Filter material, filter pack, and filter unit

Abstract

Provided are a filter material, a filter pack, and a filter unit capable of suppressing pressure loss to a low level. A filter material (30) which is provided with a porous membrane (31), a support layer (32), and a fibrous adhesive (38) that bonds the porous membrane (31) and the support layer (32), and which satisfies the relationship that the average fiber diameter of the porous membrane (31): the average fiber diameter of the adhesive (38): the average fiber diameter of the support layer (32) = 1 / 2000-1 / 30: 1-6: 1, and in which a plurality of fibers of the adhesive (38) do not overlap with each other when viewed in the thickness direction of the filter material (30), and the average fiber diameter of the porous membrane (31): the average fiber diameter of the adhesive (38): the average fiber diameter of the support layer (32) is 1 / 2000-1 / 30: 1-6: 1. Alternatively, the number of intersections of each of the fibers is three or less.

Description

Technical Field

[0001] This disclosure relates to a filter media, a filter bag, and a filter unit. Background Technology

[0002] Traditionally, porous membranes made of, for example, polytetrafluoroethylene (hereinafter, sometimes referred to as PTFE) have been used as air filters. Compared to glass fiber filter media, PTFE porous membranes have a higher dust collection efficiency under the same pressure loss, and are therefore particularly suitable for use in HEPA filters (High Efficiency Particulate Air Filters) or ULPA filters (Ultra-Low Permeability Air Filters).

[0003] As such a filter, for example, an air filter material made of PTFE porous membrane and a breathable support member is proposed, as described in Patent Document 1 (Japanese Patent Application Publication No. 2009-297702). Summary of the Invention

[0004] The technical problem that the invention aims to solve

[0005] Here, the air filter media described in Patent Document 1 is manufactured by hot laminating a PTFE porous membrane and a ventilation support member together using a pair of heated rollers. In order to bond the PTFE porous membrane and the ventilation support member through this hot lamination, the material of the ventilation support member is limited to a material that can be hot-laminated.

[0006] To address this, PTFE porous membranes can be bonded to other permeable layers using adhesives. However, increasing the amount of adhesive to achieve a good bond will lead to increased pressure loss in the resulting filter media.

[0007] Technical solutions adopted to solve technical problems

[0008] The first viewpoint describes a filter media comprising a porous membrane, a support layer, and a fibrous binder that bonds the porous membrane to the support layer. The average fiber diameters of the porous membrane, the binder, and the support layer satisfy a relationship of: average fiber diameter of the porous membrane : average fiber diameter of the binder : average fiber diameter of the support layer = 1 / 2000 to 1 / 30 : 1 to 6 : 1. When viewed along the thickness direction of the filter media, the fibers of the binder do not overlap, or the number of intersections between each fiber is three or fewer.

[0009] In addition, the average length of the adhesive fibers can be, for example, more than 100 times the average fiber diameter of the adhesive.

[0010] Furthermore, as an adhesive, there are no particular limitations; it can be a hot melt adhesive.

[0011] In addition, the support layer is not particularly limited; for example, it can be non-woven fabric.

[0012] In this filter media, the overlap of adhesive fibers between the porous membrane and the support layer is minimized. This reduces the likelihood of localized increases in the distance between the porous membrane and the support layer due to adhesive overlap, resulting in good adhesion between the porous membrane and the support layer. Furthermore, the increase in pressure loss due to the presence of adhesive fibers is minimized. Additionally, areas where adhesive fibers become embedded between the fibers of the support layer, preventing the adhesive from functioning properly, are minimized. Consequently, the amount of adhesive required for bonding the porous membrane to the support layer is reduced, and the increase in pressure loss due to adhesive fibers is also minimized, thus reducing the overall pressure loss of the filter media.

[0013] The second viewpoint describes a filter media comprising a porous membrane, a support layer, and a fibrous binder that bonds the porous membrane to the support layer. When viewed along the thickness direction of the filter media, the length directions of the multiple fibers of the binder are predetermined and parallel to each other. When viewed along the thickness direction of the filter media, the multiple fibers of the binder are wavy, each having peaks and valleys.

[0014] In addition, it is preferable that, when viewed along the thickness direction of the filter media, the multiple fibers of the adhesive do not overlap each other, or the number of intersections of each fiber is three or fewer.

[0015] In addition, the average length of the adhesive fibers can be, for example, more than 100 times the average fiber diameter of the adhesive.

[0016] In addition, as an adhesive, although there are no particular limitations, it can be a hot melt adhesive.

[0017] In addition, the support layer is not particularly limited; for example, it can be non-woven fabric.

[0018] In this filter media, the adhesive is wavy, thus enabling efficient bonding of a larger area on the porous membrane to a larger area on the support layer. Furthermore, even with the wavy adhesive, the parallel longitudinal directions of the fibers prevent the fibers from overlapping. This suppression of fiber overlap minimizes areas where the adhesive cannot function effectively. Consequently, the amount of adhesive required for bonding the porous membrane to the support layer is reduced, resulting in less pressure loss in the filter media.

[0019] The third viewpoint of the filter media is based on the first viewpoint. When viewed along the thickness direction of the filter media, the length directions of the multiple fibers of the adhesive are predetermined and parallel to each other. When viewed along the thickness direction of the filter media, the multiple fibers of the adhesive are wavy with peaks and valleys.

[0020] In this filter media, the adhesive is wavy, thus enabling efficient bonding of a larger area on the porous membrane to a larger area on the support layer. Furthermore, even though the adhesive is wavy, the parallel longitudinal directions of the fibers prevent the fibers from overlapping.

[0021] The fourth viewpoint's filter media is based on any of the filter media from the first to the third viewpoints, with a binder content of 1 g / m³. 2 Above and 5g / m 2 the following.

[0022] In this filter material, the amount of adhesive can be suppressed while ensuring good adhesion between the porous membrane and the support layer, thereby suppressing the increase in pressure loss.

[0023] The fifth viewpoint is based on the filter media of any of the first to fourth viewpoints, with the average fiber diameter of the binder being 20 μm or more and 60 μm or less.

[0024] Furthermore, the average fiber diameter of the porous membrane can be, for example, 30 nm or more and 150 nm or less. The average fiber diameter of the support layer can be, for example, 5 μm or more and 30 μm or less.

[0025] This filter material can achieve good adhesion between the porous membrane and the support layer while suppressing pressure loss caused by the presence of fibers in the adhesive.

[0026] The sixth viewpoint is based on the filter media of any of the first to fifth viewpoints, with an imaginary line of 1 cm in length drawn out in a direction orthogonal to the length direction of any one of the multiple fibers of the adhesive, and the average number of adhesive fibers intersecting the imaginary line is more than two and less than three.

[0027] This filter material reduces the number of areas where the porous membrane separates from the support layer.

[0028] The filter media of the seventh viewpoint is based on the filter media of any of the first to sixth viewpoints, and the support layer is flame retardant.

[0029] In addition, as a support layer exhibiting flame retardancy, it is preferable, for example, to exhibit flame retardancy equivalent to HF-1 in the UL94-HF method.

[0030] The filter material inhibits combustion.

[0031] The filter material of the eighth viewpoint is based on the filter material of any of the first to seventh viewpoints, and the porous membrane is a polytetrafluoroethylene porous membrane.

[0032] When the porous membrane is made of polytetrafluoroethylene (PTFE), it tends to repel adhesives. If the amount of adhesive is increased simply to improve adhesion, the pressure loss will increase. However, in such cases, the increase in pressure loss can be kept relatively small.

[0033] The filter media of the ninth viewpoint is based on the filter media of any of the first to eighth viewpoints, and the binder includes at least one of polyolefin resin and polyamide resin.

[0034] In this filter material, while ensuring good adhesion between the polytetrafluoroethylene porous membrane and the adhesive, less organic matter is generated from the adhesive. Therefore, the amount of total organic carbon (TOC) in the filter material can be suppressed to a lower level.

[0035] The filter media of the tenth viewpoint is based on the filter media of any of the first to ninth viewpoints, and the adhesive is mainly composed of polyolefin resin.

[0036] Furthermore, it is preferable that the polyolefin resin accounts for the highest weight proportion of the adhesive components, and it is even more preferable that the adhesive is composed of only polyolefin resin.

[0037] In filter media, the amount of total organic carbon can be reduced to a lower level.

[0038] The filter media of the eleventh viewpoint is based on the filter media of any of the first to tenth viewpoints, wherein the support layer comprises one or more materials selected from the group consisting of polyethylene terephthalate (PET), polyethylene (PE), polyphenylene sulfide (PPS), polypropylene (PP), and polyamide (PA). When an inert gas is passed through the filter media heated to 40°C for 60 minutes, the amount of total organic carbon detached from the filter media per unit area is 1000 μg / m². 2 the following.

[0039] In this filter material, even when a material with properties that easily generate total organic carbon is used as the support layer, the porous membrane can be bonded to the support layer by using a fibrous adhesive, thus avoiding heating for bonding and suppressing the generation of total organic carbon from the support layer due to heat.

[0040] The filter media of the twelfth viewpoint is based on the filter media of any of the first to eleventh viewpoints, and is used as an air filter for treating gases.

[0041] This filter media can minimize pressure loss when used as an air filter.

[0042] The filter pack for the thirteenth viewpoint is the filter material for any of the first to twelfth viewpoints, and is folded into a shape with peak and valley folds.

[0043] Even when the filter pack is folded in a way that creates peaks and valleys, it can still suppress the peeling of the porous membrane from the support layer.

[0044] The filter unit of the fourteenth viewpoint includes: filter media or pleated filter media of any one of the first to twelfth viewpoints, wherein the pleated filter media is the filter media of any one of the first to twelfth viewpoints and is formed in a shape with folded peaks and valleys; and a frame. The frame holds the filter media or the pleated filter media. Attached Figure Description

[0045] Figure 1 This is a schematic cross-sectional view showing the layer structure of one of the filter media.

[0046] Figure 2 This is a schematic cross-sectional view showing the layer structure of the filter media (second one).

[0047] Figure 3 This is a schematic cross-sectional view showing the layer structure of the filter media (third type).

[0048] Figure 4 This is a 3D view of the approximate appearance of the filter pack.

[0049] Figure 5 This is a schematic three-dimensional view of the filter unit.

[0050] Figure 6 This is a schematic diagram of the adhesive coating process.

[0051] Figure 7 This is a diagram illustrating an example of the coating shape of the adhesive fibers.

[0052] Figure 8 This is another example of the coating shape of the adhesive fibers. Detailed Implementation

[0053] The following examples illustrate filter media, filter bags, and filter units.

[0054] (1) Filter media

[0055] The filter media includes: a porous membrane, a support layer, and a fibrous adhesive that bonds the porous membrane and the support layer together.

[0056] The average fiber diameter of the porous membrane, the average fiber diameter of the adhesive, and the average fiber diameter of the support layer satisfy the relationship of average fiber diameter of porous membrane: average fiber diameter of adhesive: average fiber diameter of support layer = 1 / 2000~1 / 30:1~6:1.

[0057] As an adhesive, an adhesive with an average fiber diameter more than one times that of the support layer is used to suppress the entry of adhesive fibers into the spaces between the fibers of the support layer. More preferably, the average fiber diameter of the adhesive is more than 2.0 times that of the support layer. As an adhesive, an adhesive with an average fiber diameter less than six times that of the support layer is used to minimize the increase in pressure loss caused by the adhesive fibers themselves. Furthermore, it is preferable that the proportion of adhesive fibers with a fiber diameter greater than the average fiber diameter of the support layer is more than 90% of the total number of fibers in the adhesive.

[0058] Furthermore, by using an adhesive with an average fiber diameter that is 30 times or more the average fiber diameter of the porous membrane, the influence of the adhesive fibers on the filter media performance of the porous membrane can be minimized. Additionally, by using an adhesive with an average fiber diameter that is, for example, 2000 times or less the average fiber diameter of the porous membrane, the increase in pressure loss caused by the adhesive fibers themselves can be easily minimized.

[0059] In addition, as a support layer, a support layer with an average fiber diameter that is more than 30 times the average fiber diameter of the adhesive is used. This makes it easy to support the porous membrane even when it is difficult for the porous membrane to stand on its own due to its thinness, thereby improving the rigidity of the filter material.

[0060] Furthermore, the average fiber diameter of the porous membrane can be calculated by randomly selecting 50 fibers from a scanning electron microscope image as the number average fiber diameter. Additionally, the average fiber diameter of the adhesive and the average fiber diameter of the support layer can be evaluated by considering fibers within a specified range observed using a microscope or similar instrument; for example, it can be calculated as the number average fiber diameter of 200 fibers.

[0061] From the viewpoint of suppressing the entry of adhesive fibers into the fibers of the support layer, the average fiber diameter of the adhesive is preferably 20 μm or more, and more preferably 30 μm or more. Furthermore, when the adhesive is used for bonding porous membranes with an average fiber diameter of 30 nm or more and 150 nm or less, from the viewpoint of suppressing the increase in pressure loss due to the presence of adhesive fibers, the average fiber diameter is preferably 60 μm or less, and may also be 55 μm or less.

[0062] The average length of the adhesive fibers is not particularly limited, but can be, for example, more than 100 times the average fiber diameter of the adhesive, and preferably more than 500 times the average fiber diameter of the adhesive.

[0063] When an imaginary line of 1 cm length is drawn in a direction orthogonal to the length direction of any one of the fibers of the adhesive, it is preferable that the average number of adhesive fibers intersecting the imaginary line is two or more and three or less. This average number can be, for example, an average calculated using any 200 fibers of the adhesive as an example. By arranging the multiple fibers of the adhesive in a mutually complementary manner, it is possible to suppress the overlap of the adhesive fibers and to ensure that the bonding areas between the porous membrane and the support layer are evenly distributed. Furthermore, since the average number of adhesive fibers intersecting the 1 cm imaginary line is two or more, when force is applied to the porous membrane or the support layer, stress concentration at specific bonding areas can be suppressed, making it easier to maintain a good bond. For example, when pleating the joint between the porous membrane and the support layer, it is possible to suppress the peeling of the porous membrane from the support layer during pleating. The average number of fibers in the adhesive that intersect with the imaginary line of 1 cm in length is three or less, thereby suppressing the increase in pressure loss of the filter media.

[0064] Furthermore, when the average number of fibers in the adhesive intersecting with an imaginary line of 1 cm in length is the same, the larger the average fiber diameter of the adhesive fibers, the greater the coating amount per unit area (g / m²) tends to be. However, as will be explained later, it is clear that the rate of increase in pressure loss due to the adhesive fibers covering the porous membrane tends to be significantly greater than the rate of increase in coating amount per unit area. Therefore, from the viewpoint of sufficiently suppressing the rate of increase in pressure loss, the average fiber diameter of the adhesive is more preferably 1000 times or less than the average fiber diameter of the porous membrane.

[0065] When viewed along the thickness direction of the filter media, the adhesive fibers 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 within any given area. More preferably, the number of intersections between adhesive fibers on each fiber is two or fewer. While overlapping areas of adhesive fibers when viewed along the thickness direction of the filter media allow for bonding between the porous membrane and the support layer, the gap between the porous membrane and the support layer widens at these overlapping areas. Therefore, it is difficult to achieve sufficient bonding between the porous membrane and the support layer around these overlapping areas. Consequently, areas where the porous membrane floats relative to the support layer may occur, making it difficult to ensure a uniform bonding state across the entire membrane. Therefore, it is preferable to have fewer overlapping areas of adhesive fibers. Furthermore, even in the case of overlapping fibers where adhesive has been generated, a good bond can be achieved by adequately distributing adhesive fibers around the overlapping area. However, in this case, the amount of adhesive required for bonding the porous membrane to the support layer will increase, which will lead to an increase in pressure loss of the filter media.

[0066] When viewed along the thickness direction of the 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.

[0067] When viewed along the thickness direction of the 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.

[0068] When viewed along the thickness direction of the filter material, it is preferable that the shape of the adhesive is a shape other than the shape that creates overlap between the fiber portions on a single adhesive, for example, preferably not spiral and not a random coating shape.

[0069] From the viewpoint of ensuring good adhesion between the porous membrane and the support layer, when viewed along the thickness direction of the filter media, the amount of adhesive between one porous membrane and one support layer is preferably 1 g / m² or more, more preferably 2 g / m² or more. Furthermore, from the viewpoint of minimizing the increase in pressure loss due to the presence of adhesive fibers, when viewed along the thickness direction of the filter media, the amount of adhesive between one porous membrane and one support layer is preferably 5 g / m² or less, more preferably 4 g / m² or less.

[0070] From the viewpoint of minimizing the total organic carbon (TOC) of the filter media, the adhesive preferably comprises at least one of polyolefin resins and polyamide resins, and is more preferably composed mainly of polyolefin resins. Furthermore, it is preferable that it is not a rubber-based or acrylic adhesive. The weight percentage of polyolefin resin in the adhesive is, for example, 70% or more, and preferably 90% or more. Moreover, from the viewpoint of suppressing the increase in pressure loss due to excessively large fiber diameters in the adhesive, the melt viscosity of the adhesive at 180°C is preferably 2500 mPa. Below s, more preferably 2200 mPa Below s. Furthermore, from the viewpoint of easily obtaining continuously extended fibers and easily controlling the coating position by preventing the discharged fibers from becoming cut midway, the melt viscosity of the adhesive at 180°C is preferably 1000 mPa. s or higher, more preferably 1500 mPa The temperature should be s or higher. Furthermore, from the viewpoint of suppressing adhesive degradation, the heating temperature at which the adhesive melts is preferably 250°C or lower, more preferably 200°C or lower.

[0071] Furthermore, when the adhesive is applied in a manner that ensures the peel strength between the porous membrane and the support layer in the filter media is 0.1 N / 35 mm or more, it is preferable that the increase rate of pressure loss, based on the pressure loss of a laminate obtained by laminating the porous membrane and the support layer without using the adhesive, and the pressure loss of a filter media obtained by bonding the porous membrane and the support layer with the adhesive, is 10% or less, more preferably 7% or less, and even more preferably 6% or less. Furthermore, when the adhesive is applied in a manner that ensures the peel strength between the porous membrane and the support layer in the filter media is 0.2 N / 35 mm or more, the increase rate of pressure loss is preferably 10% or less, more preferably 7% or less, and even more preferably 6% or less. Here, the increase rate of pressure loss is calculated by the following formula.

[0072] Increase rate of pressure loss (%) = (Pressure loss of filter media / Pressure loss of laminate) × 100 - 100

[0073] The porous membrane is preferably, for example, of an average fiber diameter of 30 nm or more and 150 nm or less. This improves the collection efficiency.

[0074] Porous membranes, for example, are primarily composed of fluororesin, and more preferably, are fluororesin porous membranes having a porous membrane structure, wherein the porous membrane structure has fibrils (fibers) and nodes (nodules) connected to the fibrils. Here, "primarily" means that, in the case of containing multiple components, the content of fluororesin is the highest. Fluororesin porous membranes may, for example, contain 50% by weight or more of fluororesin relative to the weight of the fluororesin porous membrane, preferably 80% by weight or more, more preferably 95% by weight or more of fluororesin, or may be composed solely of fluororesin. Thus, filter media with sufficient performance can be obtained.

[0075] As a component that differs from fluororesin in porous fluororesin membranes, inorganic fillers that are non-melt-processable components that do not undergo fibrosis can be cited as examples.

[0076] Fluororesin used in porous fluoropolymer membranes can consist of one component or two or more components. Furthermore, examples of fluoropolymers include those containing fibrous PTFE. Additionally, examples of fluoropolymers include mixtures of three components: fibrous PTFE, a non-fibrous, non-thermally melt-processable component, and a non-fibrous, thermally melt-processable component with a melting point below 320°C. The melting point is typically determined using DSC (Differential Scanning Calorimetry), where it appears as an endothermic peak. Furthermore, for amorphous materials where the melting point is not clearly defined, the softening point can be used instead. The softening point is determined using differential thermal analysis (DTA), specifically the temperature at which the slope of the DTA curve first changes.

[0077] Fiberizable PTFE is a high molecular weight PTFE obtained through emulsion polymerization or suspension polymerization of tetrafluoroethylene (TFE). Here, "high molecular weight" refers to a substance that readily fibrouses during the stretching process in porous membrane fabrication, resulting in long-length fibrils. This substance has a standard specific gravity (SSG) of 2.130–2.230 and high melt viscosity, meaning it has a molecular weight that does not substantially melt and flow. Fiberability can be determined by whether it can be extruded in paste form, a representative method for shaping high molecular weight PTFE powder made from TFE polymers. If the unfired molded body obtained through paste extrusion lacks substantial strength or elongation—for example, if the elongation is 0% and it breaks upon stretching—it can be considered non-fibrous. High molecular weight PTFE can also be modified polytetrafluoroethylene, homopolymer polytetrafluoroethylene, or a mixture of modified and homopolymer PTFE.

[0078] Examples of non-thermolyzable, non-fibrous, non-thermolyzable processable components include thermoplastic components such as low molecular weight PTFE, thermosetting resins, inorganic fillers, and mixtures thereof. Low molecular weight PTFE is defined as having an index-average molecular weight of less than 600,000, a melting point between 320°C and 335°C, and a melt viscosity of 100 Pa at 380°C. s~7.0×10 5 Pa PTFE of s.

[0079] Components with melting points below 320°C that do not undergo fibrosis and are suitable for hot melt processing preferably exhibit a Pa value of less than 10000 at 380°C. The melt viscosity of s. The melting point of the component that can be thermally melted without undergoing fibrosis is the peak of the following heat of fusion curve, which is obtained as follows: by heating to above the melting point using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min until it is completely melted once, cooling to below the melting point at 10°C / min, and then heating again at 10°C / min, the heat of fusion curve is obtained.

[0080] These fibrous PTFEs, non-fibrous non-thermally meltable components, and non-fibrous thermomeltable components with melting points below 320°C can be described in detail, for example, as described in International Publication No. 2020 / 067182.

[0081] Furthermore, in the manufacturing method of fluoropolymer porous membranes, fine powder obtained by coagulation and co-coagulation of TFE after emulsion polymerization is mixed with a liquid lubricant (extrusion aid) after dehydration and drying, and then extruded in a paste form to obtain a sheet extrudate. The sheet extrudate is then calendered using calendering rollers or the like to obtain an uncalcined membrane. The liquid lubricant is removed from the uncalcined membrane, and it is then stretched to obtain a fluoropolymer porous membrane.

[0082] The pressure loss of the fluoropolymer porous membrane obtained in this way is preferably less than 300 Pa when air flows through it at a velocity of 5.3 cm / s. However, while there is no particular limitation on the pressure loss of the fluoropolymer porous membrane, it can be 50 Pa or more.

[0083] The fluoropolymer porous membrane can achieve a particle capture efficiency of 99.00% or higher, and preferably 99.99% or higher, when air containing NaCl particles with a particle size of 0.1 μm passes through it at a flow rate of 5.3 cm / s.

[0084] Furthermore, the PF value of the fluoropolymer porous membrane is preferably 20 or higher. The PF value is a value determined by the pressure loss and collection efficiency controlled by NaCl particles with a particle size of 0.1 μm and the following formula: PF value = { - log((100 - collection efficiency (%)) / 100)} / (pressure loss (Pa) / 1000).

[0085] Furthermore, the thickness of the fluoropolymer porous membrane can be, for example, 1.0 μm or more, and preferably 3.0 μm or more. By increasing the thickness of the fluoropolymer porous membrane, the dust storage capacity can be increased. Additionally, the thickness of the fluoropolymer porous membrane is, for example, 300 μm or less, and preferably 200 μm or less. The thickness of the fluoropolymer porous membrane can be measured, for example, using a membrane thickness gauge (1D-110MH type, manufactured by Mitutoyo Co., Ltd.), by overlapping five sheets of the object to be measured and measuring the overall membrane thickness, then dividing that value by 5 to obtain the thickness of one sheet.

[0086] Furthermore, when the porous membrane is a fluoropolymer porous membrane, from the viewpoint that it has good adhesion to the fluoropolymer porous membrane and can suppress the amount of total organic carbon (TOC) of the filter material, the adhesive preferably includes at least one of polyolefin resin and polyamide resin.

[0087] The support layer preferably has an average fiber diameter of 5 μm or more and 30 μm or less, more preferably 10 μm or more and 25 μm or less. This ensures adequate support for the porous membrane while suppressing the increase in pressure loss caused by excessively large fiber diameters in the support layer.

[0088] The support layer may include one or more materials selected from the group consisting of polyethylene terephthalate (PET), polyethylene (PE), polyphenylene sulfide (PPS), polypropylene (PP), and polyamide (PA). This support layer may be meltblown nonwoven fabric, spunbond nonwoven fabric, etc. Furthermore, for filter media using this support layer, the total organic carbon (TOC) content per unit area of ​​the filter media, which is removed from the filter media by passing an inert gas through the filter media heated to 40°C for 60 minutes, is preferably 1000 μg / m² or less, more preferably 500 μg / m² or less. In addition, even if a support layer containing components that can generate organic gases at high temperatures is used, since the bonding between the porous membrane and the support layer is performed using an adhesive, and it is not necessary to heat the support layer until it becomes molten, the increase in total organic carbon content due to heating of the support layer is suppressed.

[0089] The support layer is preferably not a core-sheath structure fiber including a core and a sheath with a melting point lower than that of the core, but is composed of fibers with a uniform cross-sectional structure.

[0090] The support layer preferably has flame retardancy. Specifically, the support layer preferably exhibits flame retardancy equivalent to HF-1 in the UL94-HF test. In addition, since the filter media is obtained by bonding the porous membrane and the support layer using an adhesive, it is not necessary to melt the support layer before bonding. Therefore, it is easy to select a support layer that exhibits flame retardancy as the support layer of the filter media.

[0091] The pressure loss of the support layer when air flows through it at a velocity of 5.3 cm / s is preferably less than 10 Pa.

[0092] The support layer can achieve a particle capture efficiency of 10% or less, preferably 5% or less, when air containing NaCl particles with a particle size of 0.1 μm passes through it at a flow rate of 5.3 cm / s.

[0093] Furthermore, even when multiple support layers are used, the preferred physical properties of these support layers are the same for each support layer.

[0094] Furthermore, as mentioned above, since the porous membrane and the support layer are bonded by an adhesive, it is not necessary to partially melt either layer for bonding, and the choice of material for the porous membrane or the support layer is not easily restricted.

[0095] (2) Layer structure of filter media

[0096] There are no particular restrictions on the layer structure of the filter media.

[0097] For example, it can be like Figure 1 As shown in the filter material 30, a porous membrane 31 and a first support layer 32 are stacked in the airflow direction, and an adhesive 38 is located between the porous membrane 31 and the first support layer 32. Figure 1 As shown, the first support layer 32 can be disposed on the leeward side of the porous membrane 31, or as shown in the figure. Figure 2 As shown, it is disposed on the upwind side of the porous membrane 31. Alternatively, it can be disposed as follows: Figure 3 As shown, the filter material includes a first support layer 32 laminated in the airflow direction of the porous membrane 31 and a second support layer 33 laminated on the side opposite to the first support layer 32 of the porous membrane 31, which is supported from both the downwind and upwind sides. In this case, it is preferable that the adhesive 38 is located between the porous membrane 31 and the first support layer 32, and between the porous membrane 31 and the second support layer 33.

[0098] (3) Air filter media

[0099] The filter media is preferably used as an air filter media for capturing dust contained in the airflow.

[0100] The pressure loss of the air filter media can be, for example, 400 Pa or less, preferably 300 Pa or less. While there is no particular limitation on the pressure loss of the air filter media, it can be 50 Pa or more. The pressure loss of the air filter media can be measured as the pressure loss when air flows through it at a velocity of 5.3 cm / s.

[0101] The air filter media can achieve a particle capture efficiency of 99.00% or higher, preferably 99.99% or higher, when air containing NaCl particles with a particle size of 0.1 μm passes through it at a flow rate of 5.3 cm / s.

[0102] As an air filter media, the PF value is preferably 20 or higher, wherein the PF value is determined using the pressure loss and collection efficiency controlled by NaCl particles with a particle size of 0.1 μm and the following formula: PF value = {-log((100-Collection efficiency (%)) / 100)} / (Pressure loss (Pa) / 1000).

[0103] The thickness of the air filter media is preferably 350 μm or more, for example. Furthermore, when using the air filter media with folded sections, from the viewpoint of suppressing excessive thickness of the folded sections, the thickness of the air filter media is preferably 1000 μm or less, more preferably 750 μm or less. The thickness of the air filter media is the value of the thickness when a load of 0.3 N is applied to the object being measured in a specific measuring apparatus.

[0104] Furthermore, in the air filter media, it is preferred that the average fiber diameter of the porous membrane is 30 nm or more and 150 nm or less, the average fiber diameter of the adhesive is 20 μm or more and 60 μm or less, and the average fiber diameter of the support layer is 5 μm or more and 30 μm or less.

[0105] (4) Filter pack

[0106] Next, refer to Figure 4 The filter pack (pleated filter material) of this embodiment will be described.

[0107] Figure 4 This is a perspective view of the filter pack 20 in this embodiment.

[0108] Filter pack 20 includes the air filter media (e.g., filter media 30) described above. The air filter media of filter pack 20 is a finished filter media processed into a serrated shape (pleating) by repeatedly alternating outward and inward folds. Pleating can be performed, for example, by a rotary pleating machine. The pleating width of the filter media is not particularly limited, for example, it is between 25 mm and 280 mm. By implementing pleating, filter pack 20 can increase the pleated area of ​​the filter media when used in a filter unit, thereby obtaining a filter unit with higher capture efficiency.

[0109] In addition to the filter media, the filter pack 20 may further include spacers (not shown) for maintaining the pleat spacing when used in a filter unit. The material of the spacers is not particularly limited, but hot-melt resin is preferred. Furthermore, the filter media 30 may also have multiple embossed protrusions, which hold the pleat spacing in place.

[0110] (5) Filter unit

[0111] Next, refer to Figure 5 The filter unit 1 will be described below.

[0112] Figure 5 This is a perspective view of the filter unit 1 of this embodiment.

[0113] The filter unit 1 includes: the air filter media or filter bag described above; and a frame 25 for holding the air filter media or filter bag (pleated filter media). The filter unit 1 can be manufactured by holding the filter media without peak and valley folds in the frame, or by holding the filter bag 20 in the frame 25. Figure 5 The filter unit 1 shown is made using a filter bag 20 and a frame 25.

[0114] The frame 25 is made, for example, by assembling sheets or molding resin, and the filter bag 20 and the frame 25 are preferably sealed with a sealant. The sealant is used to prevent leakage between the filter bag 20 and the frame 25, and sealants made of resins such as epoxy, acrylic, and polyurethane can be used.

[0115] The filter unit 1, which includes a filter bag 20 and a frame 25, can be a micro-pleated air filter in which a single filter bag 20 extending in a flat shape is housed inside the frame 25, or it can be a V-shaped filter unit or a single-unit filter unit in which multiple filter bags extending in a flat shape are arranged in the frame.

[0116] (6) Examples of uses

[0117] The filter media, filter packs, and filter units of this embodiment are used for, for example, the following purposes.

[0118] ULPA filters (ultra-low permeability air filters) (for semiconductor manufacturing), HEPA filters (for hospitals and semiconductor manufacturing), cylindrical 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), catalyst filters (for exhaust gas treatment), filters with adsorbents (for HDD installation), ventilation filters with adsorbents (for HDD installation), ventilation filters (for HDD installation, etc.), vacuum cleaner filters (for vacuum cleaners), general-purpose multi-layer felt materials, cartridge filters for gas turbines (compatible products for gas turbines), cooling filters (for electronic equipment housings), and other fields.

[0119] Freeze-drying materials such as containers for freeze-drying, ventilation materials for automobiles for electronic circuits and lighting, container applications such as container caps, protective ventilation applications for electronic equipment, and ventilation applications for medical use, etc., in the field of ventilation / internal pressure regulation.

[0120] Flat, pleated, and three-dimensional masks (used to prevent dust, fumes, bacteria, viruses, etc. from entering the body through the mouth and nose).

[0121] (7) Bonding of porous membrane to support layer using adhesive

[0122] The following describes the bonding process between the porous membrane and the support layer.

[0123] For example, using a porous membrane roller 61 wound into a roll shape. Figure 6 The device shown is bonded to the support layer. Here, the case where the support layers 32 and 33 are bonded to the two surfaces of the porous membrane 31 via adhesive 38 is described as an example. Furthermore, the porous membrane 31 may be a fluoropolymer porous membrane extending in both the longitudinal and width directions.

[0124] exist Figure 6In 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 support layer 32, sequentially fed from a first support layer 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 support layer 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 support layer 32. The first support layer 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 intervening therebetween. The resulting sheet formed by the bonding of the first support layer 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 support layer 33, sequentially fed from the second support layer 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 support layer 33 that is bonded to the porous membrane 31. The temperature regulating roller 66 adjusts the temperature to maintain the adhesive force of the adhesive 38 applied to the second support layer 33. The second support layer 33 and the porous membrane 31 are bonded by passing between the temperature regulating roller 66 and the silicone rubber clamping roller 67 with adhesive 38 intervening therebetween. As described above, the sheet formed by bonding the first support layer 32, the porous membrane 31, and the second support layer 33 is processed into a product via rollers 81, 82, 83, 84, 85, 86, and 87 and wound onto the product roller 69.

[0125] Furthermore, the adhesive is preferably applied in a molten state. Here, to prevent the adhesive from hardening on the support layer, it is preferable to preheat the support layer. Even in this case, heating above the melting point of the support layer is not performed; for example, it is preferable to use temperature regulating rollers 65 and 66 with a temperature of 35°C or higher and 70°C or lower, more preferably 40°C or higher and 60°C or lower. This suppresses the melting of the support layer, thereby suppressing the deformation of the fibers in the support layer. In addition, even if the support layer contains components that may release organic gases due to heat, the release of organic gases from the support layer is also suppressed because the melting of the support layer is suppressed. Furthermore, from the same viewpoint, the support layer is preferably bonded to the porous membrane without becoming molten even when heated by the temperature regulating rollers 65 and 66.

[0126] Furthermore, although the adhesive is heated to a molten state during application, it is preferable not to reheat it after application. In this way, by minimizing the heating process of the adhesive, the generation of organic gases can be suppressed, even if the adhesive contains components that generate organic gases due to heat.

[0127] The adhesive is preferably applied using a coating machine. Preferably, the coating machine has multiple arranged discharge nozzles, from which molten resin discharged from each nozzle is extended by an airflow flowing around each nozzle in the discharge direction at a speed faster than the discharge velocity, thereby achieving the desired fiber diameter. Here, by reducing the melt viscosity of the molten resin, the adhesive becomes easier to extend, thus enabling a finer fiber diameter. Furthermore, by increasing the airflow velocity, the adhesive becomes easier to extend, thus enabling a finer fiber diameter.

[0128] There are no particular limitations on the application shape of the adhesive, but as... Figure 7 , Figure 8 As shown, in order to make the direction perpendicular to the transport direction of the support layer 32 the length direction of the adhesive fibers, it is preferable to coat the adhesive in a manner in which multiple adhesive fibers are arranged in a specific configuration. Figure 7 As shown, the adhesive coating shape can also be wavy, in which peak portions protruding in a direction intersecting the length direction of the adhesive fibers and valley portions protruding on the opposite side of the peaks in a direction intersecting the length direction of the adhesive fibers are alternately arranged. Furthermore, as... Figure 8 As shown, it can also be a wavy pattern in which peaks and valleys are alternately arranged, with portions extending in a direction that intersects the length direction of the adhesive fibers.

[0129] As described above, the support layers 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 filter material 30 is obtained by pressing the support layers 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 support layers 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 support layers 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. Additionally, the temperature of the clamping rollers 64 and 67 is preferably not heated above the melting point of the support layers 32 and 33.

[0130] Furthermore, in manufacturing methods where the extended porous membrane is directly transported and moved to the bonding support layer without being wound into a roll, the air filter media, including the support layer and having a thickness, needs to be formed into a roll for storage, thus occupying space. In contrast, as described above, if the porous membrane without the support layer is wound into a roll for storage, and a bonding process is performed when the filter media with the support layer needs to be bonded to obtain the filter media and then shipped, space saving can be achieved.

[0131] Furthermore, when the support layer is melted and bonded to the porous membrane, the heating process using heated rollers until the fibers of the support layer become molten takes a considerable amount of time. Therefore, bonding the support layer 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 to bond the porous membrane to the support layer 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 process of bonding the support layer without being wound into a roll, 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 support layer while feeding out the wound porous membrane, air filter media can be obtained quickly while saving space.

[0132] Example

[0133] The following examples and comparative examples are shown, and the contents of this disclosure are described in detail.

[0134] In Example 1, a fluoropolymer porous membrane obtained as described below was bonded to a support layer using an adhesive to obtain a filter material.

[0135] 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.

[0136] 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).

[0137] 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.

[0138] Then, while the fluoropolymer porous membrane is being fed out from the porous membrane roller, a support layer coated with adhesive is stacked on the downwind side of the fluoropolymer porous membrane in the direction of airflow. The support layer is then bonded to the fluoropolymer porous membrane by a clamping roller, thereby obtaining the filter material of Example 1.

[0139] In addition, the support layer 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). Furthermore, the ratio of the average fiber diameter of the porous membrane to the average fiber diameter of the support layer in Example 1 is 0.0063.

[0140] 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).

[0141] The adhesive was applied to the support layer using a coating machine manufactured by ITW Dynatec at a linear velocity of 30 m / min. The coating machine consisted of multiple nozzles with parallel discharge directions of the adhesive. 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 support layer. 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 average fiber diameter of the adhesive coated in this manner was 48.7 μm, and the adhesive coating amount was 3.2 g / m². In addition, the average fiber diameter of the adhesive in Example 1 is 4.43 times the average fiber diameter of the support layer.

[0142] 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 support layer is bonded to the fluoropolymer porous membrane by the clamping roller is 0.40 Pa.

[0143] For Example 1 above, the peel strength (N / 35mm) of the bonded porous membrane and support layer was measured to be 0.15 (N / 35mm). Furthermore, the peel strength was measured using the 180-degree peel test method of JIS Z 0237:2009, employing a precision universal testing machine manufactured by Shimadzu Corporation, with a test piece 35mm wide and a tensile speed of 100mm / min (the same applies below).

[0144] 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. Furthermore, the ratio of the average fiber diameter of the adhesive to the average fiber diameter of the support layer in Example 2 was 3.87. For Example 2 above, the peel strength (N / 35 mm) between the bonded porous membrane and the support layer was measured to be 0.15 (N / 35 mm).

[0145] Example 3 is the same as Example 2 except for the following: the material of the support layer is changed to PET material copolymerized with 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. Furthermore, the ratio of the average fiber diameter of the porous membrane to the average fiber diameter of the support layer in Example 3 is 0.0058. Additionally, the ratio of the average fiber diameter of the adhesive to the average fiber diameter of the support layer in Example 3 is 3.82. For Example 3 above, the peel strength (N / 35 mm) between the bonded porous membrane and the support layer was measured to be 0.15 (N / 35 mm).

[0146] 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 adhesive used was Tohmide 1310 manufactured by Fuji Chemical Industries (Fuji Chemical Industries), with an adhesive coating amount of 3.4 g / m² and a clamping pressure of 0.45 Pa. Furthermore, the average fiber diameter of the adhesive in Example 4 was 4.94 times the average fiber diameter of the support layer. For Example 4 above, the peel strength (N / 35 mm) between the bonded porous membrane and the support layer was measured to be 0.17 (N / 35 mm).

[0147] Comparative Example 1 is the same as Example 1 above except for the following: a melt viscosity of 4000 mPa at 180°C is used. The hot melt resin (manufactured by Henkel, product number: TECHNOMELT MP801) had an average fiber diameter of 71.6 μm, an adhesive application amount of 4.2 g / m², and a clamping pressure of 0.55 Pa. Furthermore, the ratio of the average fiber diameter of the adhesive to the average fiber diameter of the support layer in Comparative Example 1 was 6.51. For Comparative Example 1 above, the peel strength (N / 35 mm) between the bonded porous membrane and the support layer was measured to be 0.2 (N / 35 mm).

[0148] Comparative Example 2 is the same as Example 1 except for the following: a melt viscosity of 4100 mPa at 180°C is used. 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. Furthermore, in Comparative Example 2, the ratio of the average fiber diameter of the adhesive to the average fiber diameter of the support layer was 8.94. For Comparative Example 2 above, the peel strength (N / 35 mm) between the bonded porous membrane and the support layer was measured to be 0.25 (N / 35 mm).

[0149] In addition, for each of Examples 1-4 and Comparative Examples 1-2, the pressure loss of the laminated product in the state where the porous membrane and the support layer only overlap but are not joined together, and the pressure loss of the filter material after the porous membrane and the support layer are joined together by an adhesive, are measured, and the increase rate of pressure loss accompanying the joining is determined.

[0150] (Pressure loss of laminated products before bonding)

[0151] The test sample, in which only the support layer 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 using a compressor, and the air permeation flow rate is adjusted to 5.3 cm / s using a flow meter. Then, the pressure loss at this time is measured using a pressure gauge.

[0152] (Pressure loss of the filter media after assembly)

[0153] The test sample of the filter media, which consists of a porous membrane and a support layer bonded together with an adhesive, was placed on a filter holder with a diameter of 100 mm. The inlet side was pressurized using a compressor, and the air permeation flow rate was adjusted to 5.3 cm / s using a flow meter. The pressure loss at this point was then measured using a pressure gauge.

[0154] (Increase in pressure loss)

[0155] Based on the pressure loss of the laminated product and the pressure loss of the filter material measured in the above manner, the increase rate of pressure loss is calculated according to the following formula.

[0156] Increase rate of pressure loss (%) = (Pressure loss of filter media / Pressure loss of laminate) × 100 - 100

[0157] The following shows the measurement results of each embodiment and comparative example.

[0158] [Table 1]

[0159] Table 1 above confirms the following trend: as the average fiber diameter of the adhesive increases, the rate of increase in pressure loss due to the porous membrane covered by the adhesive fibers increases significantly. In particular, a comparison between Example 2 and Comparative Example 1, with the same clamping pressure, shows that the rate of increase in pressure loss increases significantly with the increase in the average fiber diameter of the adhesive.

[0160] Furthermore, as Comparative Example 3, a filter material identical to that of Example 1 was obtained 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 3 filter media, the increase in pressure loss was 43.1%.

[0161] Furthermore, Example 5 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 this Example 5, the increase in pressure loss was 23.1%.

[0162] Furthermore, Example 6 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 6, the increase in pressure loss was 50.8%.

[0163] In Examples 5 and 6 above, the rate of increase in pressure loss increased due to the increased clamping pressure.

[0164] In addition, as Reference Example 1, a filter material identical to that of Example 1 above 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 of the adhesive was 5 g / m². As the support layer, a PET material copolymerized with a phosphorus-based flame retardant (average fiber diameter 12 μm, unit area weight 50 g / m², thickness 260 μm) was used. For Reference Example 1 above, the peel strength (N / 35 mm) between the bonded porous membrane and the support layer was measured, and the result showed that the porous membrane could not be peeled from the support layer and the porous membrane broke.

[0165] In Reference Example 1 above, because the adhesive fibers were randomly coated, there was considerable overlap between the adhesive fibers. Specifically, in Reference Example 1, an average of 5 overlaps were found between the adhesive fibers on each fiber. In Reference Example 1, although the adhesion was relatively strong enough to cause membrane rupture during peel strength testing, the increase in pressure loss was 39.2%.

[0166] In addition, as Reference Example 2, a filter material identical to that of Example 1 was obtained except for the following: an EVA-based hot-melt adhesive was used as the adhesive, and the coating was performed by sintering the powdered adhesive onto the support layer and melting it in a furnace. As a concept corresponding to the average fiber diameter of the adhesive, the average diameter of the powdered particles was approximately 600 μm, calculated by approximating a circular cross-section. The adhesive coating amount was 10 g / m². As the support layer, a PET material copolymerized with a phosphorus-based flame retardant was used (average fiber diameter 12 μm, area weight 50 g / m², thickness 260 μm). For Reference Example 2, the peel strength (N / 35 mm) between the bonded porous membrane and the support layer was measured, and the porous membrane could not be peeled from the support layer, resulting in membrane breakage.

[0167] In Reference Example 2 above, the use of sintering often results in a higher amount of powdered adhesive, which tends to be embedded between the fibers of the support layer, thus increasing pressure loss. In Reference Example 2, although the adhesion was relatively strong enough to cause membrane rupture during peel strength testing, the increase in pressure loss was 37.5%.

[0168] Furthermore, for each filter material of Examples 1-6 and Comparative Examples 1-3 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, Comparative Example 1: 114 μg / m², Comparative Example 2: 68 μg / m², Comparative Example 3: 850 μg / m², Example 5: 60 μg / m², and Example 6: 105 μg / m². For Comparative Example 3, which used a synthetic rubber-based hot-melt adhesive as the binder, a particularly large increase in degassing was observed.

[0169] In addition, among the following conventional products 1 and 2, whose degassing amounts were measured under the same conditions, conventional product 1 had a degassing amount of 550 μg / m² and conventional product 2 had a degassing amount of 814 μg / m².

[0170] Previous product 1 was a filter material obtained by thermally laminating a fluoropolymer porous membrane with a core-sheath nonwoven fabric (PT MULTISPUNINDO JAYA manufactured imitation adhesive nonwoven fabric) with PE as the core and PET as the sheath.

[0171] The previous product 2 was a filter material obtained by thermally laminating a fluoropolymer porous membrane with a core-sheath nonwoven fabric (manufactured by Unitika, product number: Elves) with PE as the core and PET as the sheath.

[0172] In addition, for each filter material of Examples 1-4, Comparative Examples 1 and 2, and Conventional Products 1 and 2, a flammability test was conducted using 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, Comparative Example 1 was equivalent to HF-1, Comparative Example 2 was equivalent to HF-1, Conventional Product 1 was equivalent to HBF, and Conventional Product 2 was equivalent to HBF.

[0173] 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.

[0174] Symbol Explanation

[0175] 1. Filter unit; 20. Filter bags, pleated filter media; 25. Frame; 30 Filter media; 31 porous membrane; 32 First support layer (support layer); 33 Second support layer (support layer); 38. Adhesives.

[0176] Existing technical documents

[0177] Patent documents

[0178] Patent Document 1: Japanese Patent Application Publication No. 2009-297702

Claims

1. A filter material (30), said filter material comprising: The porous membrane (31), the support layer (32, 33), and the fibrous adhesive (38) for bonding the porous membrane to the support layer are 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 support layer satisfy the relationship of average fiber diameter of the porous membrane: average fiber diameter of the adhesive: average fiber diameter of the support layer = 1 / 2000~1 / 30:1~6:

1. When viewed along the thickness direction of the filter material, the multiple fibers of the adhesive do not overlap each other, or the number of intersections between each fiber is three or fewer.

2. A filter material (30), the filter material comprising: The porous membrane (31), the support layers (32, 33), and the fibrous adhesive (38) that binds them together are characterized in that... When viewed along the thickness direction of the filter material, the length directions of the multiple fibers of the adhesive are predetermined and parallel to each other. When viewed along the thickness direction of the filter material, the multiple fibers of the adhesive are wavy with peak and valley portions.

3. The filter material according to claim 1, characterized in that, When viewed along the thickness direction of the filter material, the length directions of the multiple fibers of the adhesive are predetermined and parallel to each other. When viewed along the thickness direction of the filter material, the multiple fibers of the adhesive are wavy with peak and valley portions.

4. The filter material according to any one of claims 1 to 3, characterized in that, The amount of adhesive is 1 g / m 2 Above and 5g / m 2 the following.

5. The filter material according to any one of claims 1 to 4, characterized in that, The adhesive has an average fiber diameter of 20 μm or more and 60 μm or less.

6. The filter material according to any one of claims 1 to 5, characterized in that, When an imaginary line of 1 cm in length is drawn in a direction orthogonal to the length direction of any one of the fibers of the adhesive, the average number of fibers of the adhesive intersecting the imaginary line is two or more and three or less.

7. The filter material according to any one of claims 1 to 6, characterized in that, The support layer is flame retardant.

8. The filter material according to any one of claims 1 to 7, characterized in that, The porous membrane is a polytetrafluoroethylene porous membrane.

9. The filter material according to any one of claims 1 to 8, characterized in that, The adhesive comprises at least one of polyolefin resins and polyamide resins.

10. The filter material according to any one of claims 1 to 9, characterized in that, The adhesive is mainly composed of polyolefin resins.

11. The filter material according to any one of claims 1 to 10, characterized in that, The support layer comprises one or more selected from the group consisting of polyethylene terephthalate, polyethylene, polyphenylene sulfide, and polyamide. When an inert gas is passed through a filter medium heated to 40°C for 60 minutes, the amount of total organic carbon released from the filter medium per unit area is 1000 μg / m². 2 the following.

12. The filter material according to any one of claims 1 to 11, characterized in that, The filter material is used as an air filter for processing gases.

13. A filter pack (20), characterized in that, The filter bag is the filter material according to any one of claims 1 to 12, and is formed in a shape with folded peaks and valleys.

14. A filter unit (1), characterized in that, include: The filter material (30) according to any one of claims 1 to 12 or the pleated filter material (20), wherein the pleated filter material is the filter material according to any one of claims 1 to 12 and is formed in a shape with folded peaks and valleys; and The frame (25) holds the filter material or the pleated filter material.

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