Filter medium, filter pack, and filter unit

Abstract

The present invention provides: a filter medium which is capable of suppressing the pressure loss low; a filter pack; and a filter unit. Provided is a filter medium (30) which includes a porous membrane (31), a support layer (32), and a fibrous adhesive (38) that bonds the porous membrane (31) and the support layer (32) to each other, wherein the relational expression (average fiber diameter of porous membrane (31)):(average fiber diameter of adhesive (38)):(average fiber diameter of support layer (32)) = 1 / 2000-1 / 30:1-6:1 is satisfied, and when viewed in the thickness direction of the filter medium (30), a plurality of fibers of the adhesive (38) do not overlap with each other, or alternatively, the number of locations where the fibers intersect with each other is 3 or less per one fiber.

Description

Filter media, filter packs, and filter units

[0001] The present disclosure relates to filter media, filter packs, and filter units.

[0002] Conventionally, for example, the porous membrane (hereinafter sometimes referred to as PTFE) made of polytetrafluoroethylene (hereinafter sometimes referred to as PTFE porous membrane) is used as air filter.Compared with glass fiber filter material under the same pressure loss, PTFE porous membrane has high dust collection efficiency, so it is particularly suitable for HEPA filter (High Efficiency Particulate Air Filter) and ULPA filter (Ultra Low Penetration Air Filter).

[0003] As such a filter, for example, an air filter medium in which a PTFE porous film and an air-permeable support material are laminated, such as the air filter medium described in Patent Document 1 (JP 2009-297702 A), has been proposed.

[0004] Here, the air filter material described in Patent Document 1 is manufactured by using a pair of heated hot rolls to heat-laminated the entire PTFE porous membrane and the air-permeable supporting material.In order to use this heat-laminated process to bond the PTFE porous membrane and the air-permeable supporting material, the material of the air-permeable supporting material is limited to the material that can be heat-laminated.

[0005] On the other hand, PTFE porous membrane and other breathable layer can be bonded with adhesive, but if the amount of adhesive is increased in order to improve bonding state, the pressure loss of the obtained filter material will increase.

[0006] The filter material according to the first aspect is a filter material comprising a porous membrane, a support layer, and a fibrous adhesive that bonds the porous membrane and the support layer.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 the average fiber diameter of the porous membrane: the average fiber diameter of the adhesive: the average fiber diameter of the support layer = 1 / 2000 to 1 / 30: 1 to 6: 1.When viewed in the thickness direction of the filter material, the fibers of the adhesive do not overlap each other, or each fiber has three or less intersections.

[0007] The average length of the fibers of the adhesive may be, for example, 100 times or more the average fiber diameter of the adhesive.

[0008] The adhesive is not particularly limited, and may be a hot melt adhesive.

[0009] The support layer is not particularly limited and may be, for example, a nonwoven fabric.

[0010] In this filter material, the overlapping portion of adhesive fibers between porous membrane and support layer can be reduced, so that the overlapping portion of adhesive fibers between porous membrane and support layer can be reduced, and the distance between porous membrane and support layer can be prevented from increasing partially due to the overlapping portion of adhesive fibers, and the adhesion between porous membrane and support layer can be improved.Furthermore, the increase rate of pressure loss due to the existence of adhesive fibers can be reduced.In addition, the portion where adhesive fibers get into between the fibers of support layer and the function of adhesive cannot be achieved can be reduced.Therefore, the amount of adhesive required for bonding porous membrane and support layer can be reduced, and the increase rate of pressure loss due to adhesive fibers can also be reduced, so that the pressure loss of filter material can be reduced.

[0011] A filter medium according to a second aspect is the filter medium according to the first aspect, which comprises a porous membrane, a support layer, and a fibrous adhesive for bonding them together, and when viewed in the thickness direction of the filter medium, the longitudinal directions of the fibers of the adhesive are parallel to each other in a predetermined direction. When viewed in the thickness direction of the filter medium, the fibers of the adhesive are wavy, each having peaks and valleys.

[0012] It is preferable that the plurality of fibers of the adhesive do not overlap each other when viewed in the thickness direction of the filter medium, or that each fiber has three or fewer intersections.

[0013] The average length of the fibers of the adhesive may be, for example, 100 times or more the average fiber diameter of the adhesive.

[0014] The adhesive is not particularly limited, and may be a hot melt adhesive.

[0015] The support layer is not particularly limited and may be, for example, a nonwoven fabric.

[0016] In this filter material, because the adhesive is wavy, it can effectively bond the large area of ​​porous membrane and the large area of ​​support layer.And, even if the adhesive is wavy, because the longitudinal direction of each fiber is parallel, it can prevent the fibers of adhesive from being overlapped with each other.In this way, it can prevent the overlapping of the fibers of adhesive from being overlapped with each other, so it can reduce the place where the function of adhesive is not exerted.Therefore, it can reduce the amount of adhesive that is required to bond porous membrane and support layer, and it can reduce the pressure loss of filter material.

[0017] A filter medium according to a third aspect is the filter medium of the first aspect, wherein the longitudinal directions of the fibers of the adhesive are parallel to each other in a predetermined direction when viewed in the thickness direction of the filter medium, and the fibers of the adhesive are wavy with peaks and valleys when viewed in the thickness direction of the filter medium.

[0018] In this filter material, because the adhesive is wavy, it can effectively bond the large area of ​​the porous membrane and the large area of ​​the support layer.And even though the adhesive is wavy, because the longitudinal direction of each fiber is parallel, it is possible to prevent the fibers of the adhesive from overlapping with each other.

[0019] A filter medium according to a fourth aspect is the filter medium according to any one of the first aspect to the third aspect, wherein the amount of adhesive is 1 g / m ２ 5g / m or more ２ The following is the result.

[0020] This filter medium can improve the adhesiveness between the porous membrane and the support layer, while reducing the amount of adhesive used and suppressing an increase in pressure loss.

[0021] A filter medium according to a fifth aspect is the filter medium according to any one of the first aspect to the fourth aspect, wherein the average fiber diameter of the adhesive is 20 μm or more and 60 μm or less.

[0022] The average fiber diameter of the porous membrane may be, for example, 30 nm or more and 150 nm or less, and the average fiber diameter of the support layer may be, for example, 5 μm or more and 30 μm or less.

[0023] This filter medium can improve the adhesiveness between the porous membrane and the support layer, while suppressing pressure loss due to the presence of adhesive fibers.

[0024] The filter material according to the sixth aspect is a filter material according to any one of the first to fifth aspects, in which, when an imaginary line 1 cm long is drawn in a direction perpendicular to the longitudinal direction of any one of the plurality of fibers of the adhesive, the average number of fibers of the adhesive that intersect with the imaginary line is two or more and three or less.

[0025] This filter medium can reduce the number of places where the porous membrane and the support layer become separated.

[0026] A filter medium according to a seventh aspect is the filter medium according to any one of the first aspect to the sixth aspect, wherein the support layer is flame retardant.

[0027] The flame-retardant support layer preferably has flame retardancy equivalent to HF-1 according to the UL94-HF method.

[0028] This filter medium is inhibited from burning.

[0029] A filter medium according to an eighth aspect is the filter medium according to any one of the first aspect to the seventh aspect, in which the porous membrane is a polytetrafluoroethylene porous membrane.

[0030] When the porous membrane is a polytetrafluoroethylene porous membrane, it easily repels adhesive, and simply increasing the amount of adhesive to improve the adhesive state increases pressure loss. However, even in such a case, it is possible to keep the increase in pressure loss small.

[0031] A filter medium according to a ninth aspect is the filter medium according to any one of the first aspect to the eighth aspect, wherein the adhesive contains at least one of a polyolefin-based resin and a polyamide-based resin.

[0032] This filter material has good adhesion between the polytetrafluoroethylene porous film and the adhesive, and generates less organic matter from the adhesive, so the amount of total organic carbon (TOC: Total Organic Carbon) of the filter material can be reduced.

[0033] A filter medium according to a tenth aspect is the filter medium according to any one of the first to ninth aspects, in which the adhesive is mainly composed of a polyolefin resin.

[0034] Among the components of the adhesive, it is preferable that the polyolefin resin accounts for the largest proportion by weight, and it is preferable that the adhesive be composed solely of the polyolefin resin.

[0035] This filter medium can reduce the amount of total organic carbon (TOC) in the filter medium.

[0036] A filter medium according to an eleventh aspect is the filter medium according to any one of the first to tenth aspects, wherein the support layer comprises one or more selected from the group consisting of polyethylene terephthalate (PET), polyethylene (PE), polyphenylene sulfide (PPS), and polyamide (PA). The amount of total organic carbon per unit area of ​​the filter medium that is released from the filter medium by passing an inert gas through the filter medium heated to 40°C for 60 minutes is 1000 μg / m ２ The following is the result.

[0037] Even if this filter material uses the material that is easy to generate total organic carbon as support layer, by using fibrous adhesive to bond porous membrane and support layer, it can avoid heating for bonding, so that the generation of total organic carbon from support layer due to heat is suppressed.

[0038] A filter medium according to a twelfth aspect is the filter medium according to any one of the first to eleventh aspects, and is used as an air filter for treating gas.

[0039] This filter medium can reduce pressure loss when used as an air filter.

[0040] A filter pack according to a thirteenth aspect is the filter medium according to any one of the first to twelfth aspects, wherein the filter pack is folded so as to create mountain folds and valley folds.

[0041] This filter pack can prevent peeling between the porous membrane and the support layer even when folded to create mountain folds and valley folds.

[0042] A filter unit according to a fourteenth aspect includes the filter medium according to any one of the first to twelfth aspects, or a pleated filter medium according to any one of the first to twelfth aspects that is folded so as to form mountain folds and valley folds, and a frame. The frame holds the filter medium or the pleated filter medium.

[0043] 1 is a schematic cross-sectional view showing the layer structure of a filter medium (No. 1); FIG. 2 is a schematic cross-sectional view showing the layer structure of a filter medium (No. 2); FIG. 3 is a schematic cross-sectional view showing the layer structure of a filter medium (No. 3); FIG. 4 is a schematic perspective view of the appearance of a filter pack; FIG. 5 is a schematic perspective view of a filter unit; FIG. 6 is a schematic configuration diagram of an adhesive application step; FIG. 7 is a diagram showing an example of an application shape of adhesive fibers; FIG. 8 is a diagram showing another example of an application shape of adhesive fibers.

[0044] The filter media, filter packs, and filter units will be described below using examples.

[0045] (1) Filtering Medium The filtering medium includes a porous membrane, a support layer, and a fibrous adhesive that bonds the porous membrane and the support layer.

[0046] 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 to 1 / 30: 1 to 6: 1.

[0047] By using an adhesive having an average fiber diameter of at least 1 time the average fiber diameter of the support layer, the fibers of the adhesive are prevented from penetrating between the fibers of the support layer. It is more preferable that the average fiber diameter of the adhesive is at least 2.0 times the average fiber diameter of the support layer. By using an adhesive having an average fiber diameter of no more than 6 times the average fiber diameter of the support layer, the rate of increase in pressure loss caused by the adhesive fibers themselves can be kept low. It is preferable that the proportion of the number of adhesive fibers with a fiber diameter larger than the average fiber diameter of the support layer out of the total number of fibers in the adhesive is 90% or more.

[0048] In addition, by using adhesive that has average fiber diameter that is 30 times or more than the average fiber diameter of porous membrane, can minimize the influence that adhesive fiber has on the filter performance of porous membrane.In addition, by using adhesive that has average fiber diameter that is for example 2000 times or less than the average fiber diameter of porous membrane, can easily minimize the increase rate of the pressure loss that adhesive fiber itself causes.

[0049] In addition, by using the material that the average fiber diameter of the support layer is 30 times or more than the average fiber diameter of adhesive, even if porous membrane is thin and difficult to stand on its own, the support layer can easily support porous membrane, and can improve the rigidity of filter material.

[0050] The average fiber diameter of the porous membrane may be calculated as a number-average fiber diameter by randomly selecting 50 fibers from a scanning electron microscope image. The average fiber diameter of the adhesive and the average fiber diameter of the support layer can be evaluated based on fibers present within a predetermined range of an image observed using a microscope or the like, and may be calculated as a number-average fiber diameter of, for example, 200 fibers.

[0051] The adhesive preferably has an average fiber diameter of 20 μm or more, more preferably 30 μm or more, from the viewpoint of suppressing the penetration of the adhesive fibers between the fibers of the support layer. Furthermore, when the adhesive is used to bond a porous membrane having an average fiber diameter of 30 nm or more and 150 nm or less, the adhesive preferably has an average fiber diameter of 60 μm or less, and may have an average fiber diameter of 55 μm or less, from the viewpoint of suppressing the rate of increase in pressure loss due to the presence of the adhesive fibers.

[0052] The average length of the fibers of the adhesive is not particularly limited, but may be, for example, 100 times or more the average fiber diameter of the adhesive, and preferably 500 times or more the average fiber diameter of the adhesive.

[0053] When a 1 cm long imaginary line is drawn in a direction perpendicular to the longitudinal direction of any one of the plurality of adhesive fibers, the average number of adhesive fibers intersecting this imaginary line is preferably 2 to 3. This average number can be, for example, the average value counted for 200 arbitrary adhesive fibers. By arranging a plurality of adhesive fibers side by side, it is possible to prevent the adhesive fibers from overlapping with each other and to evenly arrange the adhesive points between the porous membrane and the support layer. And, since the average number of adhesive fibers intersecting the 1 cm long imaginary line is 2 or more, when a force is applied to the porous membrane or the support layer, stress is prevented from concentrating on a specific adhesive part, making it easier to maintain a good adhesive state. For example, when the bonded porous membrane and the support layer are pleated, it is possible to prevent the porous membrane and the support layer from peeling off during pleating. By making the average number of adhesive fibers intersecting the 1 cm long imaginary line 3 or less, the increase in pressure loss of the filter medium is suppressed.

[0054] In addition, when the number of adhesive fibers is approximately the same, such as when the average number of adhesive fibers intersecting an imaginary line of 1 cm in length is approximately the same, the adhesive with a larger average fiber diameter will have a higher coating amount per unit area (g / m ２ ) tends to increase. However, as will be described later, it has become clear that the rate of increase in pressure loss due to the fibers of the adhesive covering the porous membrane tends to be significantly larger than the rate of increase in the amount of adhesive applied per unit area. Therefore, from the viewpoint of sufficiently suppressing the rate of increase in pressure loss, it is more preferable that the average fiber diameter of the adhesive is 1000 times or less the average fiber diameter of the porous membrane.

[0055] When viewed in the thickness direction of the filter material, the plurality of adhesive fibers do not overlap with each other, or the number of intersections between each fiber is three or less. Note that the number of intersections between adhesive fibers refers to the average number of intersections between each adhesive fiber and its own fiber and the fibers of other adhesives. Although not particularly limited, it may be calculated as the average number of intersections between 100 adhesive fibers in any region. Furthermore, it is more preferable that the number of intersections between adhesive fibers per adhesive fiber is two or less. When viewed in the thickness direction of the filter material, the overlapping portions of the adhesive fibers can bond the porous membrane and the support layer, but the gap between the porous membrane and the support layer widens at the overlapping portions of the adhesive fibers, making it difficult to sufficiently bond the porous membrane and the support layer around the overlapping portions of the adhesive fibers. Therefore, there are some portions where the porous membrane floats relative to the support layer, making it difficult to ensure a uniform adhesion state throughout the membrane. Therefore, it is preferable to have few overlapping portions of the adhesive fibers. In addition, even if there are overlapping portions of adhesive fibers, it is possible to improve the adhesion state by arranging sufficient adhesive fibers around the overlapping portions, but in this case, the amount of adhesive required to bond the porous membrane and the support layer increases, which increases the pressure loss of the filter material.

[0056] It is preferable that the longitudinal directions of the adhesive fibers are parallel to each other in a predetermined direction when viewed in the thickness direction of the filter medium, which makes it possible to prevent the adhesive fibers from overlapping with each other.

[0057] The shape of the adhesive fiber is preferably wavy with peaks and valleys when viewed in the thickness direction of the filter material. It is preferable that more than half of the shape of the adhesive fiber is wavy with peaks and valleys, and more preferably that more than 90% is wavy with peaks and valleys.

[0058] It is preferable that the shape of the adhesive be a shape other than a shape that causes overlapping of fiber portions in a single adhesive when viewed in the thickness direction of the filter material, for example, a shape that is not spiral or a randomly applied shape.

[0059] The amount of adhesive is 1 g / m between one porous membrane and one support layer in the thickness direction of the filter medium from the viewpoint of improving the adhesion between the porous membrane and the support layer. ２ It is preferable that the content is 2 g / m or more. ２ In addition, the amount of adhesive is preferably 5 g / m between one porous membrane and one support layer in the thickness direction of the filter medium, from the viewpoint of suppressing the increase in pressure loss due to the presence of adhesive fibers. ２ Preferably, the amount is 4 g / m or less. ２ More preferably, it is:

[0060] From the viewpoint of minimizing the total organic carbon (TOC) of the filter material, the adhesive preferably contains at least one of a polyolefin resin and a polyamide resin, and preferably is composed mainly of a polyolefin resin. Furthermore, it is preferable that the adhesive is not a rubber-based adhesive or an acrylic-based adhesive. The weight ratio of the polyolefin resin in the adhesive is, for example, 70% or more, preferably 90% or more. Furthermore, from the viewpoint of suppressing an increase in pressure loss due to the adhesive fiber diameter becoming too large, the adhesive preferably has a melt viscosity of 2500 mPa·s or less at 180°C, more preferably 2200 mPa·s or less. Furthermore, from the viewpoint of suppressing the extruded fibers from being cut midway, making it easy to obtain continuously extending fibers and to easily control the application position, the adhesive preferably has a melt viscosity of 1000 mPa·s or more, more preferably 1500 mPa·s or more at 180°C. From the viewpoint of preventing deterioration of the adhesive, the heating temperature when melting the adhesive is preferably 250°C or lower, and more preferably 200°C or lower.

[0061] In addition, when adhesive is applied so that the peel strength of the porous membrane and the support layer in the filter material is ensured to be 0.1N / 35mm or more, the pressure loss of the laminated product that the porous membrane and the support layer are laminated without using adhesive, and the pressure loss of the filter material that the porous membrane and the support layer are bonded using adhesive, the increase rate of the pressure loss obtained from is preferably 10% or less, more preferably 7% or less, and even more preferably 6% or less.In addition, when adhesive is applied so that the peel strength of the porous membrane and the support layer in the filter material is ensured to be 0.2N / 35mm or more, the increase rate of the pressure loss is preferably 10% or less, more preferably 7% or less, and even more preferably 6% or less.Here, the increase rate of the pressure loss is calculated by the following formula.Increase rate of the pressure loss (%) = (pressure loss of the filter material / pressure loss of the laminated product) × 100-100

[0062] The porous membrane preferably has an average fiber diameter of, for example, 30 nm or more and 150 nm or less, which makes it possible to increase the collection efficiency.

[0063] For example, porous membrane is mainly composed of fluororesin, and more preferably is the fluororesin porous membrane with a porous membrane structure that has fibril (fiber) and the node (node) connected to fibril.Here, " mainly " means that when containing a plurality of kinds of components, fluororesin is contained in the largest amount.For example, fluororesin porous membrane can contain 50 wt% or more of fluororesin relative to the weight of fluororesin porous membrane, preferably contain 80 wt% or more of fluororesin, more preferably contain 95 wt% or more of fluororesin, and can be composed only of fluororesin.Therefore, can obtain a filter material with sufficient performance.

[0064] An example of a component different from the fluororesin contained in the fluororesin porous membrane is an inorganic filler, which is a non-melt-processable component that does not cause fibrosis.

[0065] The fluororesin used in the fluororesin porous membrane may consist of one kind of component, or may consist of two or more kinds of components. In addition, as the fluororesin, for example, one containing fibrous PTFE can be mentioned. In addition, as the fluororesin, a mixture of three components can be mentioned: fibrous PTFE, a non-fibrous non-thermal melt processable component, and a non-fibrous non-thermal melt processable component with a melting point of less than 320 ° C. In addition, the melting point can generally be measured by DSC (differential scanning calorimetry), and refers to the one that appears as an endothermic peak. In addition, for amorphous structures that do not clearly show a melting point, the softening point can be used instead. The softening point can be understood by differential thermal analysis (DTA) as the temperature at which the slope of the DTA graph first changes.

[0066] Fibrotic PTFE is high molecular weight PTFE obtained by emulsion polymerization or suspension polymerization of tetrafluoroethylene (TFE). Here, "high molecular weight" refers to a material that is easily fibrillated during stretching when producing a porous membrane, and produces long fibrils, with a standard specific gravity (SSG) of 2.130 to 2.230, and a molecular weight of a size that does not melt and flow due to high melt viscosity. Whether or not it can be fibrillated can be determined by whether or not paste extrusion, a typical method for molding high molecular weight PTFE powder made from TFE polymer, is possible. If the unsintered molded body obtained by paste extrusion has no substantial strength or elongation, for example, if the elongation is 0% and it breaks when pulled, it can be considered to have no fibrillogenicity. High molecular weight PTFE can be modified polytetrafluoroethylene, homopolytetrafluoroethylene, or a mixture of modified PTFE and homoPTFE.

[0067] Examples of non-thermal melt processable components that do not cause fibrosis include thermoplastic components such as low-molecular-weight PTFE, thermosetting resins, inorganic fillers, and mixtures thereof. Low-molecular-weight PTFE has a number-average molecular weight of 600,000 or less, a melting point of 320°C or more and 335°C or less, and a melt viscosity at 380°C of 100 Pa s to 7.0 x 10 ５ It is PTFE with a viscosity of Pa·s.

[0068] The melting point of the non-Fibrotic hot melt processable composition that is less than 320 DEG C is preferably less than 10,000 Pa s at 380 DEG C. The melting point of the non-Fibrotic hot melt processable composition is measured by using differential scanning calorimetry (DSC) to heat up to above melting point at a heating rate of 10 DEG C / min, melt completely once, then cool down to below melting point at a heating rate of 10 DEG C / min, and then heat up again at a heating rate of 10 DEG C / min, and obtain the peak top of the heat of fusion curve.

[0069] These fibrous PTFE, non-fibrous non-thermal melt processable components, and non-fibrous non-thermal melt processable components having a melting point of less than 320 ° C. can be those described in detail in, for example, International Publication No. 2020 / 067182.

[0070] In addition, in the manufacturing method of fluororesin porous membrane, use the fine powder obtained by coagulation, co-coagulation from emulsion polymerization of TFE, after dehydration and drying, mix with liquid lubricant (extrusion aid), carry out paste extrusion to obtain sheet-like extrudate.Then, by using calender roll etc. to roll out sheet-like extrudate to obtain the unsintered film, remove liquid lubricant, carry out stretching, can obtain fluororesin porous membrane.

[0071] The fluororesin porous membrane thus obtained preferably has a pressure loss of 300 Pa or less when air is passed through it at a flow rate of 5.3 cm / sec. The pressure loss of the fluororesin porous membrane is not particularly limited, but may be 50 Pa or more.

[0072] The fluororesin porous membrane may have a particle collection efficiency of 99.00% or more, preferably 99.99% or more, when air containing NaCl particles with a particle diameter of 0.1 μm is passed through it at a flow rate of 5.3 cm / sec.

[0073] The PF value of the fluororesin porous membrane is preferably not less than 20. The PF value is determined by the following formula using the pressure loss and collection efficiency determined using NaCl particles with a particle diameter of 0.1 μm: PF value={−log((100−collection efficiency (%)) / 100)} / (pressure loss (Pa) / 1000).

[0074] The thickness of the fluororesin porous film can be, for example, 1.0 μm or more, and preferably 3.0 μm or more. Increasing the film thickness of the fluororesin porous film makes it possible to increase the dust holding capacity. The film thickness of the fluororesin porous film is, for example, 300 μm or less, and preferably 200 μm or less. The thickness of the fluororesin porous film can be determined, for example, by using a film thickness meter (Model 1D-110MH, manufactured by Mitutoyo Corporation) to measure the total film thickness of five stacked measurement targets, and dividing this value by 5 to obtain the film thickness of one film.

[0075] In addition, when porous membrane is fluororesin porous membrane, the adhesiveness with fluororesin porous membrane is good, and from the viewpoint that can suppress the total organic carbon (TOC: Total Organic Carbon) amount of filter material to a small extent, preferably, adhesive agent comprises at least one of polyolefin resin and polyamide resin.

[0076] 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, for example, so that the porous membrane is sufficiently supported while the increase in pressure loss caused by the fiber diameter of the support layer becoming too large is suppressed.

[0077] The support layer may contain one or more materials selected from the group consisting of polyethylene terephthalate (PET), polyethylene (PE), polyphenylene sulfide (PPS), and polyamide (PA). Such a support layer may be a meltblown nonwoven fabric, a spunbond nonwoven fabric, or the like. The filter medium using this support layer has a total organic carbon (TOC) per unit area of ​​the filter medium of 1000 μg / m2, which is released from the filter medium by passing an inert gas through the filter medium heated to 40°C for 60 minutes. ２ Preferably, it is 500 μg / m or less. ２ It is more preferable that the following is satisfied: Even if a material containing a component that can generate organic gas in a high-temperature environment is used as the support layer, the porous membrane and the support layer are bonded using an adhesive, and it is not necessary to heat the support layer until it is in a molten state, so that an increase in the amount of total organic carbon due to heating of the support layer is suppressed.

[0078] The support layer is preferably composed of fibers that are not core-sheath structure fibers that include a core and a sheath having a melting point lower than that of the core, and that have a uniform cross-sectional structure.

[0079] Preferably, support layer is flame retardant.Specifically, support layer is preferably in accordance with UL94-HF method and shows the flame retardancy equivalent to HF-1.In addition, filter material is obtained by bonding porous membrane and support layer with adhesive, and there is no need to bond support layer in molten state, so it is easy to select the one that shows flame retardancy as the support layer of filter material.

[0080] The support layer preferably has a pressure loss of, for example, 10 Pa or less when air is passed through it at a flow rate of 5.3 cm / sec.

[0081] The support layer may have a particle collection efficiency of 10% or less, preferably 5% or less, when air containing NaCl particles having a particle diameter of 0.1 μm is passed through it at a flow rate of 5.3 cm / sec.

[0082] In addition, even when a plurality of support layers are used, the preferable physical properties of each support layer are the same.

[0083] Furthermore, as described above, the porous membrane and the support layer are bonded by an adhesive, so there is no need to partially melt either layer to bond them, and there is little restriction in the selection of the material of the porous membrane or the material of the support layer.

[0084] (2) Layer Structure of Filter Medium The layer structure of the filter medium is not particularly limited.

[0085] For example, as shown in Fig. 1, the filter material 30 may be configured such that the porous membrane 31 and the first support layer 32 are stacked in the air flow direction, and the adhesive 38 is located between the porous membrane 31 and the first support layer 32. As shown in Fig. 1, the first support layer 32 may be provided on the leeward side of the porous membrane 31, or as shown in Fig. 2, it may be provided on the windward side of the porous membrane 31. In addition, as shown in Fig. 3, the filter material may be provided with the first support layer 32 that is stacked on the porous membrane 31 in the air flow direction, and the second support layer 33 that is stacked on the opposite side of the first support layer 32 side of the porous membrane 31, and the porous membrane 31 is supported from both the leeward side and the windward side. In this case, it is preferable that the adhesive 38 is located between the porous membrane 31 and the first support layer 32, and the adhesive 38 is located between the porous membrane 31 and the second support layer 33.

[0086] (3) Air Filter Media The filter media is preferably used as an air filter media that captures dust contained in an air current.

[0087] The pressure loss of air filter material may be, for example, 400 Pa or less, preferably 300 Pa or less.The pressure loss of air filter material is not particularly limited, but may be 50 Pa or more.The pressure loss of air filter material can be measured as the pressure loss when air is passed through at a flow rate of 5.3 cm / second.

[0088] The air filter medium may have a particle collection efficiency of 99.00% or more, preferably 99.99% or more, when air containing NaCl particles with a particle diameter of 0.1 μm is passed through it at a flow rate of 5.3 cm / sec.

[0089] The air filter medium preferably has a PF value of, for example, 20 or more, determined by the following formula: PF value = {-log((100-collection efficiency (%)) / 100)} / (pressure loss (Pa) / 1000), where the pressure loss and collection efficiency are determined using NaCl particles with a particle diameter of 0.1 μm.

[0090] The thickness of air filter material is preferably 350 μ m or more for example.In addition, when the thickness of air filter material is used in the state of having folded part, from the viewpoint of suppressing the thickness of folded part from becoming too large, for example, it is preferably 1000 μ m or less, more preferably 750 μ m or less.The thickness of air filter material is the thickness value when a load of 0.3 N is applied to the measurement object in a specific measuring device.

[0091] In the air filter medium, it is preferable 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.

[0092] (4) Filter Pack Next, the filter pack (pleated filter medium) of this embodiment will be described with reference to FIG.

[0093] FIG. 4 is a perspective view of the appearance of the filter pack 20 of this embodiment.

[0094] The filter pack 20 includes the air filter medium (e.g., filter medium 30) described above. The air filter medium of the filter pack 20 is a processed filter medium that has been pleated into a zigzag shape with alternating mountain folds and valley folds. Pleating can be performed, for example, using a rotary folding machine. The folded width of the filter medium is not particularly limited, but is, for example, 25 mm to 280 mm. The pleated filter pack 20 can increase the folded area of ​​the filter medium when used in a filter unit, thereby obtaining a filter unit with high collection efficiency.

[0095] 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 a hot-melt resin is preferably used. Furthermore, the filter media 30 may have a plurality of embossed protrusions that maintain the pleat spacing.

[0096] (5) Filter Unit Next, the filter unit 1 will be described with reference to FIG.

[0097] FIG. 5 is a perspective view showing the appearance of the filter unit 1 of this embodiment.

[0098] The filter unit 1 includes the air filter medium or filter pack described above and a frame 25 that holds the air filter medium or filter pack (pleated filter medium). The filter unit 1 may be fabricated so that the filter medium that is not folded in the mountain or valley is held in the frame, or so that the filter pack 20 is held in the frame 25. The filter unit 1 shown in Figure 5 is fabricated using the filter pack 20 and the frame 25.

[0099] The frame 25 is made, for example, by combining plate materials or by molding resin, and the gap between the filter pack 20 and the frame 25 is preferably sealed with a sealant. The sealant is used to prevent leakage between the filter pack 20 and the frame 25, and is made of, for example, an epoxy, acrylic, or urethane resin.

[0100] The filter unit 1, which includes the filter pack 20 and the frame body 25, may be a mini-pleat type filter unit in which one filter pack 20 extending in a flat plate shape is held inside the frame body 25, or may be a V-bank type filter unit or a single-header type filter unit in which multiple filter packs extending in a flat plate shape are arranged and held in a frame body.

[0101] (6) Examples of Uses The filter medium, filter pack, and filter unit according to this embodiment are used, for example, in the following applications.

[0102] ULPA filters (Ultra Low Penetration Air Filters) (for semiconductor manufacturing), HEPA filters (for hospitals and semiconductor manufacturing), cylindrical cartridge filters (for industrial use), bag filters (for industrial use), heat-resistant bag filters (for exhaust gas treatment), heat-resistant pleated filters (for exhaust gas treatment), SINBRAN (registered trademark) filters (for industrial use), catalytic filters (for exhaust gas treatment), filters with adsorbent (for HDD integration), adsorbent vent filters (for HDD integration), vent filters (for HDD integration, etc.), vacuum cleaner filters (for vacuum cleaners), general-purpose multi-layer felt materials, gas turbine cartridge filters (for gas turbine compatible products), cooling filters (for electronic device housings), etc.

[0103] Freeze-drying materials such as freeze-drying containers, automotive ventilation materials for electronic circuits and lamps, container applications such as container caps, protective ventilation applications for electronic devices, ventilation / internal pressure adjustment applications such as medical ventilation applications.

[0104] Flat, pleated, three-dimensional masks (which prevent dust, oily smoke, bacteria, viruses, etc. from entering the body through the human mouth and nose).

[0105] (7) Bonding of porous membrane and support layer using adhesive Hereinafter, the step of bonding the porous membrane and support layer will be described.

[0106] The porous membrane roll 61 wound into a roll is bonded to a support layer, for example, using the device shown in Fig. 6. Here, an example will be described in which support layers 32 and 33 are bonded to both sides of the porous membrane 31 via an adhesive 38. The porous membrane 31 may be a fluororesin porous membrane stretched in the longitudinal and transverse directions.

[0107] In the apparatus shown in FIG. 6 , the porous membrane 31 sequentially delivered from the porous membrane roll 61 is supplied to the silicone rubber nip roll 64 via roll 74. The first support layer 32 sequentially delivered from the first support layer roll 62 is supplied to the temperature-controlled roll 65 via rolls 71, 72, and 73. After passing through roll 73 and before reaching the temperature-controlled roll 65, adhesive 38 is applied from a hot melt gun 68 to the surface of the first support layer 32 that will be bonded to the porous membrane 31. The temperature-controlled roll 65 adjusts the temperature so that the adhesive 38 applied to the first support layer 32 maintains its adhesive strength. The first support layer 32 and the porous membrane 31 are bonded by passing between the temperature-controlled roll 65 and the silicone rubber nip roll 64 with the adhesive 38 interposed therebetween. The sheet-like product, in which the first support layer 32 and the porous membrane 31 are bonded, is then supplied to the silicone rubber nip roll 67 via rolls 75, 76, and 77. The second support layer 33, sequentially fed from the second support layer roll 63, is supplied to the temperature-controlled roll 66 via rolls 78, 79, and 80. After passing through the roll 80 and before reaching the temperature-controlled roll 66, adhesive 38 is applied from a hot melt gun 68 to the surface of the second support layer 33 that will be bonded to the porous membrane 31. The temperature-controlled roll 66 adjusts the temperature so that the adhesive 38 applied to the second support layer 33 maintains its adhesive strength. The second support layer 33 and the porous membrane 31 are bonded by passing between the temperature-controlled roll 66 and a silicone rubber nip roll 67 with the adhesive 38 interposed therebetween. The sheet-like material formed by bonding the first support layer 32, the porous membrane 31, and the second support layer 33 in this manner is turned into a product via rolls 81, 82, 83, 84, 85, 86, and 87 and wound up onto the product roll 69.

[0108] It is preferable that the adhesive be applied in a molten state. Here, it is preferable to warm the support layer in order to prevent the adhesive from hardening in the support layer. Even in this case, the support layer is not heated above its melting point, and is preferably heated, for example, using temperature-controlled rolls 65, 66 at a temperature of 35°C to 70°C, more preferably 40°C to 60°C. This prevents the support layer from melting and prevents the fibers of the support layer from deforming. Furthermore, even if the support layer contains a component that can release organic gases due to heat, suppressing melting of the support layer also prevents the release of organic gases from the support layer. From the same perspective, it is preferable that the support layer be bonded to the porous membrane without becoming molten even when heated by the temperature-controlled rolls 65, 66.

[0109] Furthermore, it is preferable that the adhesive is heated to a molten state when applied, but is not reheated after application. By minimizing the heating history of the adhesive in this way, it is possible to suppress the generation of organic gases, even if the adhesive contains components that can generate organic gases when heated.

[0110] The adhesive is preferably applied using an applicator. The applicator preferably has a plurality of discharge nozzles arranged in a row, and the molten resin discharged from each discharge nozzle is stretched by an air flow sent around each nozzle in the discharge direction at a speed faster than the discharge speed, thereby forming a desired fiber diameter for application. Here, by reducing the melt viscosity of the molten resin, the adhesive becomes more easily stretched, thereby enabling the fiber diameter to be made thinner. Furthermore, by increasing the speed of the air flow, the adhesive becomes more easily stretched, thereby enabling the fiber diameter to be made thinner.

[0111] The shape of the adhesive application is not particularly limited, but is preferably such that a plurality of adhesive fibers are arranged side by side so that the direction perpendicular to the conveyance direction of the support layer 32 is the longitudinal direction of the adhesive fibers, as shown in Figures 7 and 8. The adhesive application shape may be a wave shape in which peaks protruding in a direction intersecting the longitudinal direction of the adhesive fibers and valleys protruding on the opposite side to the peaks in a direction intersecting the longitudinal direction of the adhesive fibers are alternately arranged, as shown in Figure 7. Alternatively, the adhesive may be a wave shape in which peaks and valleys are alternately arranged so as to have a portion extending in a direction intersecting the longitudinal direction of the adhesive fibers, as shown in Figure 8.

[0112] The support layers 32, 33 coated with adhesive as described above are superimposed on the porous membrane 31, and pressure is applied by the nip rolls 64, 67. At this time, the support layers 32, 33 and the porous membrane 31 are pressed against each other, thereby obtaining a filter medium 30. Here, the pressure applied by the nip rolls 64, 67 to the laminate of the porous membrane and the support layer attached with adhesive is preferably, for example, 0.6 MPa or less, from the viewpoint of suppressing the increase in the rate of pressure loss due to pressure during lamination. Furthermore, the pressure applied by the nip rolls 64, 67 to the laminate of the porous membrane and the support layer attached with adhesive is preferably, for example, 0.3 MPa or more, from the viewpoint of easily ensuring a good bonding state. This pressure can be measured, for example, using a pressure measurement film (Prescale manufactured by Fujifilm Corporation) as the instantaneous pressure when passing between the rolls. It is also preferable that the temperature of the nip rolls 64, 67 is not heated above the melting point of the support layers 32, 33.

[0113] In addition, for example, in the case of the manufacturing method that the porous membrane obtained by stretching is not wound up in roll form, is conveyed as it is, and is transferred to the process of bonding support layer, the thick air filter material that includes support layer must be rolled up and stored, so it will require space.On the other hand, as mentioned above, if the porous membrane that support layer is not bonded in state is wound up in roll form and stored, and when the filter material that support layer is bonded is needed, carry out bonding process to obtain filter material and ship, it can save space.

[0114] In addition, when melting and adhering support layer to porous membrane, because it takes a long time to heat the fiber of support layer by heating roller until it is in a molten state, when applying adhesive to adhere support layer to porous membrane, bonding process can be carried out in a shorter time.Here, when manufacturing porous membrane, when the porous membrane is obtained by stretching for a predetermined time, the time required for bonding porous membrane and support layer may be shorter than the time required for stretching porous membrane.Therefore, if the porous membrane obtained by stretching is not wound up in roll shape, and is directly transported, and the manufacturing method of transferring to the process of adhering support layer, the stretching process of porous membrane is the rate-limiting step.On the other hand, if the manufacturing method is to prepare a large number of porous membrane rolls that can be stored in a small space in advance, and carry out the bonding process with support layer while sending out the porous membrane that is wound up in roll shape, it can save space and quickly obtain air filter material.

[0115] Hereinafter, the contents of the present disclosure will be specifically described with reference to examples and comparative examples.

[0116] In Example 1, a fluororesin porous membrane obtained as follows was bonded to a support layer using an adhesive to obtain a filter medium.

[0117] First, 300 g of hydrocarbon oil (IP Solvent 2028, manufactured by Idemitsu Kosan Co., Ltd.) was added as an extrusion liquid lubricant per 1 kg of PTFE fine powder (Polyflon Fine Powder F106, manufactured by Daikin Industries, Ltd.) having an average molecular weight of 6.5 million and mixed at 20°C. The resulting mixture was then extruded using a paste extrusion device to obtain a rod-shaped compact. This rod-shaped compact was then formed into a sheet using a calendar roll heated to 70°C to obtain a fluororesin sheet. This fluororesin sheet was passed through a hot air drying oven at 250°C to evaporate and remove the hydrocarbon oil, yielding a strip-shaped unsintered fluororesin sheet with an average thickness of 200 μm and an average width of 150 mm.

[0118] Next, the unsintered fluororesin sheet was stretched in the longitudinal direction at a stretch ratio of 5. The stretching temperature in the longitudinal direction was 250° C. Here, the stretching rate (% / s) in the longitudinal direction was 150 (% / s).

[0119] Next, the stretched unsintered fluororesin sheet was stretched in the width direction at a stretching temperature of 350°C and a stretching ratio of 30 times using a tenter capable of continuous clipping, to obtain a fluororesin porous membrane. The fluororesin porous membrane was wound up on a porous membrane roll. The average fiber diameter of the obtained fluororesin porous membrane was 69 nm.

[0120] Then, while sending out fluororesin porous membrane from porous membrane roll, the supporting layer that is coated with adhesive is stacked on the leeward side of the air flow passing direction of fluororesin porous membrane, and through nip roll, the supporting layer is bonded to fluororesin porous membrane, thereby obtain the filter material of embodiment 1.

[0121] The support layer used in Example 1 was a spunbond nonwoven fabric (average fiber diameter 11 μm, basis weight 40 g / m) made of PET. ２ The average fiber diameter of the porous membrane in Example 1 / the average fiber diameter of the support layer was 0.0063.

[0122] The adhesive used in Example 1 was an olefin-based hot melt resin (manufactured by Asahi Chemical Synthetic Co., Ltd., product number: Asahi Melt FR921) having a melt viscosity of 1600 (mPa·s) at 180°C.

[0123] The adhesive was applied to the support layer by spray coating at a line speed of 30 m / min using an applicator manufactured by ITW Dynatec. The applicator used had multiple nozzles with parallel directions for discharging the adhesive. During application, the air flow velocity was controlled to be faster than the adhesive discharge velocity, so that the adhesive fibers stretched against the support layer were applied in a wavy pattern. The opening size at the tip of the applicator nozzle was 0.43 μm. ２ The size of the air outlet is 0.64 μm ２The pump speed for pumping the adhesive in a molten state heated to 180°C was set to 6.4%, and air heated to 190°C was pumped at a flow rate of 3000 cm3 in order to stretch the adhesive fibers after the molten adhesive was discharged from the nozzle. ３ The adhesive applied in this manner had an average fiber diameter of 48.7 μm and an adhesive application rate of 3.2 g / m ２ In Example 1, the ratio of the average fiber diameter of the adhesive to the average fiber diameter of the support layer was 4.43.

[0124] In Example 1, there were no locations where the fibers of the adhesive substantially overlapped each other. Furthermore, in Example 1, when an imaginary line 1 cm long was drawn in a direction perpendicular to the longitudinal direction of any one of the fibers of the adhesive, the average number of fibers of the adhesive intersecting the imaginary line was 2.5. In Example 1, the nip pressure when bonding the support layer to the fluororesin porous membrane using nip rolls was 0.40 Pa.

[0125] In the above Example 1, the peel strength (N / 35 mm) of the bonded porous membrane and support layer was measured and found to be 0.15 (N / 35 mm). The peel strength was measured based on the test method of JIS Z 0237:2009 180-degree peel test using a precision universal testing machine manufactured by Shimadzu Corporation, with a test piece width of 35 mm and a tensile speed of 100 mm / min (the same applies below).

[0126] In Example 2, a hot melt resin (manufactured by Asahi Chemical Synthetic Co., Ltd., product number: Asahi Melt FR530) having a melt viscosity of 2050 mPa·s at 180°C was used, the average fiber diameter of the adhesive was 42.6 μm, and the coating amount of the adhesive was 3.0 g / m ２ The same as in Example 1 except that the nip pressure was 0.55 Pa. In Example 2, the average fiber diameter of the adhesive / average fiber diameter of the support layer was 3.87. In Example 2, the peel strength (N / 35 mm) of the bonded porous membrane and support layer was measured and found to be 0.15 (N / 35 mm).

[0127] In Example 3, the material of the support layer was a PET material copolymerized with a phosphorus-based flame retardant (average fiber diameter 12 μm, basis weight 50 g / m ２ The average fiber diameter of the adhesive was 45.8 μm, and the coating amount of the adhesive was 3.1 g / m ２ The same as in Example 2 except that the nip pressure was 0.45 Pa. In Example 3, the average fiber diameter of the porous membrane / average fiber diameter of the support layer was 0.0058. In Example 3, the average fiber diameter of the adhesive / average fiber diameter of the support layer was 3.82. In the above Example 3, the peel strength (N / 35 mm) of the bonded porous membrane and support layer was measured and found to be 0.15 (N / 35 mm).

[0128] In Example 4, the hot melt resin of the adhesive was changed to Tomide 1310 manufactured by Fuji Chemical Industry Co., Ltd., which has a melt viscosity of 2500 mPa·s at 180°C, and the amount of adhesive applied was 3.4 g / m ２ The same as in Example 1 except that the nip pressure was 0.45 Pa. In Example 4, the average fiber diameter of the adhesive / average fiber diameter of the support layer was 4.94. In Example 4, the peel strength (N / 35 mm) of the bonded porous membrane and support layer was measured and found to be 0.17 (N / 35 mm).

[0129] In Comparative Example 1, a hot melt resin (manufactured by Henkel, product number: TECHNOMELT MP801) having a melt viscosity of 4000 mPa·s at 180°C was used, the average fiber diameter of the adhesive was 71.6 μm, and the coating amount of the adhesive was 4.2 g / m ２ The same as in Example 1 except that the nip pressure was 0.55 Pa. The average fiber diameter of the adhesive / average fiber diameter of the support layer in Comparative Example 1 was 6.51. When the peel strength (N / 35 mm) of the bonded porous membrane and support layer in Comparative Example 1 was measured, it was 0.2 (N / 35 mm).

[0130] In Comparative Example 2, a hot melt resin (manufactured by Asahi Chemical Synthetic Co., Ltd., product number: Asahi Melt FR561) having a melt viscosity of 4100 mPa·s at 180°C was used, the average fiber diameter of the adhesive was 98.3 μm, and the coating amount of the adhesive was 4.8 g / m ２The same as in Example 1 except that the nip pressure was 0.50 Pa. In Comparative Example 2, the average fiber diameter of the adhesive / average fiber diameter of the support layer was 8.94. For Comparative Example 2, the peel strength (N / 35 mm) of the bonded porous membrane and support layer was measured and found to be 0.25 (N / 35 mm).

[0131] In addition, for each embodiment 1-4 and comparative example 1-2, measure the pressure loss of the laminated product that only has porous membrane and supporting layer stacked and is not bonded to each other, and the pressure loss of the filter material that porous membrane and supporting layer are bonded to each other with adhesive, and obtain the increasing rate of the pressure loss that accompanies bonding.

[0132] (Pressure loss of laminate before bonding) A measurement sample in which the support layer was simply laminated on the porous membrane but not bonded was set in a filter holder with a diameter of 100 mm, and the inlet side was pressurized with a compressor, and the air permeation flow rate was adjusted to 5.3 cm / sec with a flow meter. Then, the pressure loss at this time was measured with a manometer.

[0133] (The pressure loss of the filter material after bonding) The measurement sample of the filter material that porous membrane and supporting layer are bonded with adhesive is set in the filter holder of diameter 100mm, and the inlet side is pressurized by compressor, and the flow rate of the air that passes through is adjusted to 5.3cm / sec by flow velocity meter.Then, the pressure loss at this time is measured by manometer.

[0134] (Increase in Pressure Loss) The increase in pressure loss was calculated from the pressure loss of the laminate and the pressure loss of the filter medium measured as described above according to the following formula: Increase in pressure loss (%) = (pressure loss of filter medium / pressure loss of laminate) x 100 - 100

[0135] The measurement results for each example and comparative example are shown below.

[0136] According to Table 1 above, it was confirmed that when the average fiber diameter of the adhesive is increased, the rate of increase in pressure loss due to the adhesive fibers covering the porous membrane increases significantly. In particular, when Example 2 and Comparative Example 1, which have the same nip pressure, are compared, it can be seen that the rate of increase in pressure loss increases significantly as the average fiber diameter of the adhesive increases.

[0137] In Comparative Example 3, a synthetic rubber-based hot melt resin (Sanyo Life Material 939S) having a melt viscosity of 2300 mPa·s at 180°C was used, the average fiber diameter of the adhesive was 102.2 μm, and the coating amount of the adhesive was 4.7 g / m ２ A filter medium similar to that of Example 1 was obtained, except that the nip pressure was 0.55 Pa. In the filter medium of Comparative Example 3, the increase rate of pressure loss was 43.1%.

[0138] In Example 5, a hot melt resin (manufactured by Asahi Chemical Synthetic Co., Ltd., product number: Asahi Melt FR921) having a melt viscosity of 1600 mPa·s at 180°C was used, the average fiber diameter of the adhesive was 45.3 μm, and the coating amount of the adhesive was 3.1 g / m ２ The filter material of Example 5 was the same as Example 1 except that the nip pressure was 0.75 Pa. In the filter material of Example 5, the increase rate of pressure loss was 23.1%.

[0139] In Example 6, a hot melt resin (manufactured by Asahi Chemical Synthetic Co., Ltd., product number: Asahi Melt FR530) having a melt viscosity of 2050 mPa·s at 180°C was used, the average fiber diameter of the adhesive was 43.7 μm, and the coating amount of the adhesive was 3.0 g / m ２ The filter material of Example 6 was the same as Example 1 except that the nip pressure was 0.90 Pa. In the filter material of Example 6, the increase rate of pressure loss was 50.8%.

[0140] In Examples 5 and 6, the rate of increase in pressure loss is high due to the increased nip pressure.

[0141] In Reference Example 1, a PP-based hot melt adhesive was used as the adhesive, and the adhesive was spray-applied using an applicator equipped with a plurality of nozzles whose discharge directions for discharging the adhesive were randomly oriented. The average fiber diameter of the adhesive was 116 μm, and the applied amount of adhesive was 5 g / m. ２ The support layer is made of a PET material copolymerized with a phosphorus-based flame retardant (average fiber diameter 12 μm, basis weight 50 g / m ２Obtain the same filter material as above-mentioned embodiment 1, except that the filter material is used (thickness 260 μ m).In above-mentioned reference example 1, when the peel strength (N / 35mm) of the bonded porous membrane and supporting layer is measured, porous membrane cannot be peeled off from supporting layer, and porous membrane breaks.

[0142] In the above-described Reference Example 1, the adhesive fibers were randomly applied, resulting in many overlaps between the adhesive fibers. Specifically, an average of five overlaps between the adhesive fibers per adhesive fiber were observed in Reference Example 1. In Reference Example 1, the adhesive was bonded so strongly that film rupture occurred when the peel strength was confirmed, but the increase in pressure loss was 39.2%.

[0143] In Reference Example 2, an EVA-based hot melt adhesive was used as the adhesive, and the powder adhesive was applied to the support layer and melted in a furnace by a sintering method. The average diameter, calculated by approximating the cross section of the powder particles to a circle, was 600 μm, which corresponds to the average fiber diameter of the adhesive. The adhesive was applied in an amount of 10 g / m. ２ The support layer is made of a PET material copolymerized with a phosphorus-based flame retardant (average fiber diameter 12 μm, basis weight 50 g / m ２ Obtain the same filter material as above-mentioned embodiment 1, except that the filter material is used (thickness 260 μ m).In above-mentioned reference example 2, when the peel strength (N / 35mm) of the bonded porous membrane and supporting layer is measured, porous membrane cannot be peeled off from supporting layer, and porous membrane breaks.

[0144] In the above-mentioned Reference Example 2, because of the sintering method, the amount of powder adhesive used tends to be large, and the powder adhesive tends to fill in the spaces between the fibers of the support layer, which tends to increase pressure loss. In Reference Example 2, the adhesion was strong enough to cause film rupture when the peel strength was confirmed, but the increase rate of pressure loss was 37.5%.

[0145] In addition, for each filter medium of the above Examples 1-6 and Comparative Examples 1-3, the amount of outgassing was measured according to the dynamic headspace method as follows. In the measurement of the amount of outgassing, a 120mm x 40mm test specimen was placed in a thermostatic chamber at 40°C for 60 minutes, and organic matter was desorbed from the test specimen. A high purity helium gas of 99.9999% was ventilated in the thermostatic chamber, and the gas after passing through was sent to an adsorption tube to collect the generated organic matter. The collected organic matter was analyzed by gas chromatography mass spectrometry (GC-MS). The amount of outgassing was 52 μg / m in Example 1, 52 μg / m in Example 2, and 52 μg / m in Comparative Examples 1. ２ , and Example 2 is 112 μg / m ２ , and Example 3 is 454 μg / m ２ , and Example 4 is 150 μg / m ２ , and Comparative Example 1 is 114 μg / m ２ , and Comparative Example 2 is 68 μg / m ２ , Comparative Example 3 is 850 μg / m ２ , and Example 5 is 60 μg / m ２ , and Example 6 is 105 μg / m ２ It was confirmed that the amount of outgassing was particularly increased in Comparative Example 3, which used a synthetic rubber hot melt adhesive.

[0146] In addition, when the outgassing amount was measured under the same conditions for Conventional Product 1 and Conventional Product 2 described below, Conventional Product 1 had a value of 550 μg / m ２ , and conventional product 2 is 814 μg / m ２ It was.

[0147] Conventional product 1 was a filter medium obtained by thermally laminating a fluororesin porous membrane and a core-sheath nonwoven fabric (spunbond nonwoven fabric manufactured by PT MULTI SPUNINDO JAYA) with PE as the core and PET as the sheath.

[0148] Conventional product 2 was a filter medium obtained by thermally laminating a fluororesin porous membrane and a core-sheath nonwoven fabric (manufactured by Unitika, product number: Elbes) with PE as the core and PET as the sheath.

[0149] Furthermore, for each filter material of the above-mentioned Examples 1-4, Comparative Examples 1 and 2, and Conventional Products 1 and 2, a flammability test was carried out using the UL94-HF method. As a result, 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.

[0150] Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure as defined in the claims.

[0151] DESCRIPTION OF SYMBOLS 1 Filter unit 20 Filter pack, pleated filter medium 25 Frame 30 Filter medium 31 Porous membrane 32 First support layer (support layer) 33 Second support layer (support layer) 38 Adhesive

[0152] JP 2009-297702 A

Claims

1. A filter medium (30) comprising a porous membrane (31), a support layer (32, 33), and a fibrous adhesive (38) for bonding the porous membrane and the support layer, wherein 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 to 1 / 30: 1 to 6: 1, and when viewed in the thickness direction of the filter medium, the multiple fibers of the adhesive do not overlap each other, or each fiber has three or less intersections.

2. A filter medium (30) comprising a porous membrane (31), support layers (32, 33), and a fibrous adhesive (38) for bonding them together, wherein, when viewed in the thickness direction of the filter medium, the longitudinal directions of the fibers of the adhesive are parallel to each other in a predetermined direction, and when viewed in the thickness direction of the filter medium, the fibers of the adhesive are wavy, each having peaks and valleys.

3. The filter medium described in claim 1, wherein, when viewed in the thickness direction of the filter medium, the longitudinal directions of each of the multiple fibers of the adhesive are in a predetermined direction and parallel to each other, and, when viewed in the thickness direction of the filter medium, each of the multiple fibers of the adhesive is wavy having peaks and valleys.

4. The amount of the adhesive is 1 g / m ２ 5g / m or more ２ The filter medium according to any one of claims 1 to 3, wherein:

5. The filter medium according to any one of claims 1 to 4, wherein the average fiber diameter of the adhesive is 20 μm or more and 60 μm or less.

6. A filter medium according to any one of claims 1 to 5, wherein when an imaginary line 1 cm long is drawn in a direction perpendicular to the longitudinal direction of any one of the multiple fibers of the adhesive, the average number of fibers of the adhesive intersecting the imaginary line is 2 or more and 3 or less.

7. The filter medium according to any one of claims 1 to 6, wherein the support layer is flame retardant.

8. The filter medium according to any one of claims 1 to 7, wherein the porous membrane is a polytetrafluoroethylene porous membrane.

9. The filter medium according to any one of claims 1 to 8, wherein the adhesive contains at least one of a polyolefin resin and a polyamide resin.

10. The filter medium according to any one of claims 1 to 9, wherein the adhesive is mainly composed of a polyolefin resin.

11. The support layer contains one or more selected from the group consisting of polyethylene terephthalate, polyethylene, polyphenylene sulfide, and polyamide, and the amount of total organic carbon per unit area of ​​the filter medium that is released from the filter medium by passing an inert gas through the filter medium heated to 40°C for 60 minutes is 1000 μg / m ２ The filter medium according to any one of claims 1 to 10, wherein:

12. The filter medium according to any one of claims 1 to 11, which is used as an air filter for treating gas.

13. A filter pack (20) comprising a filter medium according to any one of claims 1 to 12, which is folded so as to produce mountain folds and valley folds.

14. A filter unit (1) comprising: a filter material (30) as set forth in any one of claims 1 to 12; or a pleated filter material (20) as set forth in any one of claims 1 to 12 that is folded so as to create mountain folds and valley folds; and a frame (25) that holds the filter material or the pleated filter material.

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