Filter

Abstract

To provide a filter having an adhesive playing a role in holding an object to be collected.SOLUTION: There is provided a filter in which an adhesive contains a cellulose nanofiber in addition to an adhesive component, and thereby prevents an object to be collected from flowing out to the downstream side. There is provided a filter in which the adhesive component exists in a dispersed state in the adhesive without unintended aggregation due to existence of the cellulose nanofiber, and thereby the filter has a cloth where the adhesive is distributed without forming lumps and the adhesive is uniformly attached. As a result, a filter which prevents an object to be collected from flowing out to the downstream side can be provided.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a filter having an adhesive capable of holding objects to be collected. [Background technology]

[0002] For example, filters are installed and used in homes, large structures such as buildings, hospitals, and schools, as well as factories such as food factories, pharmaceutical factories, and semiconductor factories, to capture dust particles and other particles contained in the air introduced into the building.In addition, filters are installed and used in industrial facilities such as paint booths to capture paint mists and dust particles contained in the atmosphere where products are processed and manufactured.

[0003] However, conventional filters used for such purposes have the problem that the objects captured by the filter tend to fall off and flow downstream of the filter during use or replacement.

[0004] As a filter capable of preventing such objects from falling off, for example, Japanese Patent Application Laid-Open No. 2001-137627 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2022-167454 (Patent Document 2) disclose a filter having a fabric to which an adhesive containing an adhesive component such as polybutene is attached. In this filter, the objects to be captured are held in contact with the adhesive, making them less likely to fall off the filter. As a result, the objects to be captured can be prevented from flowing downstream of the filter. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2001-137627

[0006] [Patent Document 2] Patent Publication No. 2022-167454 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the case of filters (hereinafter sometimes abbreviated as filters) having a fabric with an adhesive attached, such as those disclosed in Patent Documents 1 and 2, the objects to be collected still tend to flow out downstream of the filter. Therefore, there is a need for a filter that makes it difficult for the objects to be collected to flow downstream. [Means for solving the problem]

[0008] The present invention is "(Claim 1) A filter comprising a fabric to which an adhesive is attached, the adhesive containing an adhesive component and cellulose nanofibers. (Claim 2) The filter according to claim 1, wherein the same type of fiber is present throughout the thickness of the fabric. (Claim 3) The filter according to claim 1 or claim 2, wherein the fabric has a coarse layer and a dense layer. [Effects of the Invention]

[0009] The applicant of the present application investigated the cause of this problem and found that if the object to be collected passes through the filter without coming into contact with and being held by the adhesive, the object to be collected flows out downstream of the filter.In addition, the applicant found that if the object to be collected that had been held in contact with the adhesive falls off, the object to be collected also flows out downstream of the filter if the fallen object to be collected does not come into contact with and be held by the adhesive on the downstream side of the filter. The inventors have found that the reason that the objects to be collected pass through the filters according to the conventional technology is due to the uneven distribution of the adhesive in the fabric.

[0010] In other words, when comparing filters with fabric having the same amount of adhesive attached, one filter with uniformly attached adhesive (filter A) and one filter with unevenly distributed adhesive (filter B), the following phenomenon is thought to occur.

[0011] Because the adhesive is uniformly adhered to the fabric of filter A, objects to be captured in the air passing through filter A can easily come into contact with and be held by the adhesive. In addition, if objects to be captured fall off the adhesive, because the adhesive is uniformly adhered to filter A in the thickness direction, the objects to be captured can also easily come into contact with and be held by the adhesive on the downstream side of filter A. As a result, it is thought that the objects to be collected are less likely to flow out to the downstream side of the filter A.

[0012] On the other hand, because the adhesive is not uniformly adhered to the fabric of filter B, objects to be captured in the air passing through filter B are difficult to come into contact with and be held by the adhesive. In addition, if objects to be captured fall off the adhesive, the adhesive is not uniformly adhered to filter B in the thickness direction, so the objects to be captured are difficult to come into contact with and be held by the adhesive even downstream of filter B. As a result, it is thought that the objects to be collected tend to flow out to the downstream side of filter B.

[0013] As a result of further research, the applicant discovered that by including cellulose nanofibers in addition to the adhesive component in the adhesive, a filter can be provided that makes it difficult for the objects to be captured to flow downstream. Although the reason for this is not entirely clear, it is thought to be due to the following effect: The presence of cellulose nanofibers allows the adhesive components in the adhesive to remain dispersed without unintentional aggregation, so the adhesive is distributed without clumping, making it possible to realize a filter equipped with a fabric to which the adhesive is uniformly attached. As a result, it is possible to provide a filter that makes it difficult for the objects to be captured to flow downstream.

[0014] Furthermore, in the filter according to the present invention, the same type of fiber can be present throughout the thickness of the fabric, which results in the same or similar adhesive properties across the thickness of the fabric, thereby achieving a filter with fabric to which the adhesive is more uniformly attached across the thickness of the fabric. Therefore, it is possible to provide a filter that makes it more difficult for the objects to be collected to flow downstream.

[0015] Furthermore, the filter according to the present invention can have a fabric with a coarse layer and a dense layer, and by providing such a fabric, it is possible to realize a filter with low pressure loss due to the presence of the coarse layer and high collection efficiency due to the presence of the dense layer. Therefore, it is possible to provide a filter in which the objects to be collected are less likely to flow downstream and which has higher filtering performance. DETAILED DESCRIPTION OF THE INVENTION

[0016] In the present invention, various configurations can be appropriately selected, for example, the following configurations. Note that, unless otherwise specified, the various measurements described in the present invention are performed under atmospheric pressure. Furthermore, measurements are performed under a temperature condition of 25°C. Unless otherwise specified, the various measurement results described in the present invention are measured to a value one digit smaller than the desired value, and the value is calculated by rounding off the value. Specifically, when the desired value is expressed to one decimal place, the value is measured to two decimal places, and the obtained value is rounded to one decimal place to calculate the value to one decimal place, and this value is used as the desired value. The upper and lower limits exemplified in the present invention can be combined in any combination.

[0017] The fabric referred to in the present invention refers to a structure made of fibers in the form of a sheet, such as a fiber web or nonwoven fabric, or a woven or knitted fabric. In particular, when the filter includes a fabric (particularly a fiber web or nonwoven fabric) in which all constituent fibers are randomly entangled, this is preferable because it provides a filter that has lower pressure loss, excellent collection properties, and is likely to maintain its filtration performance for a long period of time.

[0018] The constituent fibers of the fabric include, for example, polyolefin resins (e.g., polyethylene, polypropylene, polyolefin resins in which part of the hydrocarbon is substituted with a cyano group or a halogen such as fluorine or chlorine), polymethylpentene, styrene resins, polyvinyl alcohol resins, polyether resins (e.g., polyether ether ketone, polyacetal, modified polyphenylene ether, aromatic polyether ketone), polyester resins (e.g., polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polycarbonate, polyarylate, wholly aromatic polyester resin), polyimide resins, It can be made using known resins such as polyamideimide resin, polyamide-based resin (e.g., aromatic polyamide resin, aromatic polyetheramide resin, nylon resin, etc.), resin having a nitrile group (e.g., polyacrylonitrile, etc.), urethane-based resin, epoxy-based resin, polysulfone-based resin (e.g., polysulfone, polyethersulfone, etc.), fluorine-based resin (e.g., polytetrafluoroethylene, polyvinylidene fluoride, etc.), cellulose-based resin, polybenzimidazole resin, acrylic-based resin (e.g., polyacrylonitrile-based resin copolymerized with acrylic acid ester or methacrylic acid ester, modacrylic-based resin copolymerized with acrylonitrile and vinyl chloride or vinylidene chloride, etc.).

[0019] These resins may be either linear polymers or branched polymers, may be block copolymers or random copolymers, and may have any three-dimensional structure or crystallinity, without any particular limitations.Furthermore, the fabric may contain, as its constituent fibers, fibers made of a mixed resin obtained by blending multiple resin components.

[0020] The fabric may also contain, as constituent fibers, known inorganic fibers such as silicone fibers, glass fibers, metal oxide fibers such as silica fibers, and metal fibers.

[0021] The constituent fibers can be obtained by known methods, such as melt spinning, dry spinning, wet spinning, direct spinning (melt-blowing, spunbonding, electrostatic spinning, etc.), a method of extracting fibers with a small fiber diameter by removing one or more resin components from composite fibers, or a method of beating fibers to obtain split fibers.

[0022] The constituent fibers may be composed of one type of resin or multiple types of resins. Fibers composed of multiple types of resins may be in the form of what are generally called composite fibers, such as core-sheath composite fibers, sea-island composite fibers, side-by-side composite fibers, and orange composite fibers.

[0023] The constituent fibers may include irregular cross-section fibers other than those having a substantially circular or elliptical cross-sectional shape. The irregular cross-section fibers may have a cross section that is hollow, polygonal such as a triangular shape, alphabetic such as a Y-shape, irregular, multi-lobed, symbolic such as an asterisk, or a shape combining multiple of these shapes.

[0024] When the fabric contains heat-fusible fibers as constituent fibers, the constituent fibers of the fabric are heat-fused together, which is preferable because it can impart strength and shape stability to the fabric. Such heat-fusible fibers may be fully fusible heat-fusible fibers or partially fusible heat-fusible fibers in the same manner as the above-mentioned composite fibers (for example, core-sheath composite fibers in which the sheath component is heat-fusible).

[0025] For example, a fiber web can be prepared by a dry method in which the above-mentioned fibers are fed into a carding device or an air-laying device to entangle the fibers, or a wet method in which the fibers are dispersed in a solvent and woven into a sheet to entangle the fibers, and then the fibers are spun and collected.

[0026] Furthermore, a fabric made of a mixture of fibers having a continuous length and staple fibers having a specific fiber length is preferable because it provides a filter that has lower pressure loss, excellent collection properties, and is easy to maintain its filtration performance for a long period of time.

[0027] The constituent fibers of the prepared fiber web can be entangled and / or integrated to prepare a nonwoven fabric. Examples of methods for entangling and / or integrating the constituent fibers include integrating the constituent fibers with an adhesive component, integrating the constituent fibers with a binder resin other than the adhesive component, entanglement with needles or water flow, and heat-fusion bonding the constituent fibers with heat-fusible fibers by subjecting the fiber web to a heat treatment. The resins exemplified as being capable of forming the constituent fibers of fabrics can be used as the binder resin.

[0028] Alternatively, nonwoven fabrics can be prepared using direct spinning methods (meltblowing, spunbonding, electrospinning, methods in which a spinning solution and a gas stream are discharged in parallel to each other to spin (for example, the method disclosed in JP-A-2009-287138), etc.).

[0029] The heat treatment method can be appropriately selected, and examples thereof include a method of heating or heating and pressurizing with a roll, a method of heating by subjecting to a heater such as an oven dryer, a far-infrared heater, a dry heat dryer, or a hot air dryer, and a method of irradiating infrared rays without pressure to heat the resin contained therein.

[0030] When the fabric is a woven or knitted fabric, the woven or knitted fabric can be prepared by weaving or knitting the fibers prepared as described above.

[0031] In addition to fiber webs, nonwoven fabrics, woven fabrics, and knitted fabrics may also be subjected to the above-mentioned method of entangling and / or integrating constituent fibers.

[0032] The fineness and fiber length of the fibers constituting the fabric are not particularly limited, but can be adjusted appropriately to provide a filter that has lower pressure loss, excellent collection properties, and is easy to maintain filtration performance for a long period of time. The fineness can be 1 to 50 dtex, 5 to 40 dtex, or 10 to 30 dtex. The constituent fibers can be fibers with a continuous length (fibers with no specific length), such as directly spun fibers such as meltblown fibers and electrospun fibers. The constituent fibers can also be staple fibers with a specific fiber length, and the fiber length can be 30 to 120 mm, 40 to 100 mm, or 50 to 80 mm. The "fiber length" refers to a value measured in accordance with JIS L1015 (2010), 8.4.1c) direct method (method C).

[0033] The fabric may be composed of a single fiber layer, or may be a fabric having multiple fiber layers, such as a fabric prepared by laminating multiple fiber layers or a fabric prepared by forming a new fiber layer on the main surface of a fiber layer.

[0034] A specific example is a fabric constructed by laminating a fiber layer (coarse layer) having a low apparent density, such as a fiber layer derived from a fiber web having a low apparent density, and a fiber layer (dense layer) having a high apparent density, such as a fiber layer derived from a fiber web having a high apparent density. The method for laminating the fiber layers can be appropriately selected, and examples include a method of simply overlapping and laminating each fiber layer, a method of laminating each fiber layer and then subjecting the fiber layers to an entanglement treatment such as needle punching or hydroentanglement treatment to entangle the constituent fibers beyond the interlayer space between the fiber layers and laminating them together, a method of bonding each fiber layer with a binder to laminate them together, and a method of laminating each fiber layer together by melting heat-fusible fibers contained in the constituent fibers.

[0035] As another specific example, the fabric may be a fabric having a fiber layer (dense layer) with a high apparent density formed on the main surface of a fiber layer (coarse layer) with a low apparent density, or a fabric having a fiber layer (coarse layer) with a low apparent density formed on the main surface of a fiber layer (dense layer). A method for forming a new fiber layer on the main surface of a fiber layer can be appropriately selected, and examples include a method for forming a new fiber layer by paper-making a fiber dispersion on the main surface of the fiber layer, and a method for forming a new fiber layer by collecting spun fibers on the main surface of the fiber layer.

[0036] The apparent density (unit: g / cm 3 ) is the basis weight (unit: g / m) of the fiber sheet sampled from the fiber layer to be measured. 2 ) by the thickness (unit: mm) and convert the obtained value. The apparent density of a fiber layer with a low apparent density (coarse layer) can be adjusted as appropriate, but should be within the range of 0.003 to 0.3 g / cm. 3 and can be 0.005 to 0.05 g / cm 3 and can be 0.01 to 0.03 g / cm 3 The apparent density of the fiber layer with a high apparent density (dense layer) can be adjusted as appropriate, but is preferably 0.003 to 0.3 g / cm. 3 and can be 0.005 to 0.05 g / cm 3 and can be 0.01 to 0.03 g / cm 3 It can be.

[0037] By providing a fabric having a laminated structure of coarse and dense layers, it is possible to realize a filter with lower pressure loss due to the presence of the coarse layers and high collection efficiency due to the presence of the dense layers, which is preferable.

[0038] The fabric may have three or more fiber layers, and in this case, it is preferable to provide a third fiber layer between the coarse and dense layers, the third fiber layer having an apparent density higher than that of the coarse layer but lower than that of the dense layer, in order to realize a filter with low pressure loss and high collection efficiency.

[0039] In the filter of the present invention, it is preferable that the same type of fiber is present throughout the thickness of the fabric. As a result, the adhesive properties of the adhesive are the same or similar across the thickness of the fabric, resulting in a filter with fabric to which the adhesive is more uniformly attached throughout the thickness of the fabric. This makes it possible to provide a filter that is more resistant to the flow of the target material downstream.

[0040] Here, the presence of the same type of fiber across the thickness of the fabric means that the resin constituting one type of fiber present on both main surfaces of the fabric is the same as the resin constituting one type of fiber present on a cut surface formed when the fabric is cut parallel to the main surfaces at any thickness in the thickness direction (two cut surfaces are formed by cutting, but at least one of the cut surfaces) formed.

[0041] In particular, it is most preferable that the same fibers are present throughout the thickness of the fabric to achieve a filter with a fabric to which the adhesive is more uniformly attached. Here, "the same fibers are present throughout the thickness of the fabric" means that the fibers constituting both main surfaces of the fabric and the fibers present on the cut surface formed by cutting the fabric at an arbitrary thickness in the thickness direction parallel to the main surfaces (two cut surfaces are formed by cutting, but at least one of the cut surfaces) are the same fibers. Here, "the same fibers" refers to fibers that have the same fiber diameter, fiber length, cross-sectional shape, and resin composition.

[0042] As a specific example, in a fabric composed of a single fiber layer made up of fibers containing a certain resin as a constituent resin, the fibers making up both main surfaces of the fabric and the fibers present on the cut surface formed when the fabric is cut parallel to the main surfaces at any thickness in its thickness direction (two cut surfaces are formed by cutting, but at least one of the cut surfaces) are the same fibers.

[0043] When a fabric has multiple fiber layers, if each fiber layer contains the same type of fiber as its constituent fiber, the adhesive properties of each fiber layer will be the same or similar, which will result in uniform adhesion of the adhesive across each fiber layer, making it possible to realize a filter including a fabric with uniformly adhered adhesive, which is preferable.

[0044] Here, when we say that a certain fiber layer (fiber layer a, for example, a coarse layer) and another fiber layer (fiber layer b, for example, a dense layer) contain the same type of fiber, we mean that the resin constituting one type of fiber among the constituent fibers of fiber layer a is the same as the resin constituting one type of fiber among the constituent fibers of fiber layer b.

[0045] As a specific example, in a fabric having a fiber layer a prepared by blending fibers containing a certain resin as a constituent resin and a fiber layer b prepared by blending fibers containing the same resin as a constituent resin, the fiber layer a and the fiber layer b contain the same type of fiber.

[0046] In particular, it is most preferable that each fiber layer of the fabric contains the same fiber, so that the adhesive can be more uniformly applied to each fiber layer and a filter having a fabric with a uniformly applied adhesive can be realized. As a specific example, in a fabric having a fiber layer c prepared by blending a certain fiber and a fiber layer d prepared by blending the same fiber, the fiber layer c and the fiber layer d contain the same fiber.

[0047] The various configurations of the fabric, such as thickness and basis weight, are not particularly limited, but can be adjusted as appropriate to provide a filter that has lower pressure loss and excellent collection properties, is easy to maintain filtration performance for a long period of time, and is difficult for the objects to be collected to flow downstream.

[0048] The thickness may be 3 to 50 mm, 5 to 40 mm, or 10 to 30 mm. The basis weight is 10 to 1000 g / m 2 and can be 100 to 700 g / m 2 and can be 200 to 500 g / m 2In the present invention, the thickness is 1.0 g / cm in the direction perpendicular to the main surface. 2 The basis weight is the length in the vertical direction when a compressive load of 10 ... 2 This refers to the mass per unit mass.

[0049] In the filter according to the present invention, an adhesive is attached to the fabric. The adhesive component contained therein adheres the target substance to the adhesive, thereby holding the target substance in contact with the adhesive and preventing the target substance from falling off the filter equipped with the fabric.

[0050] The type of adhesive component can be appropriately selected depending on the application of the filter, etc., and examples of adhesive components that can be used include polybutene, polyisobutylene, polyisoprene, polybutadiene, acrylic copolymers, styrene-butadiene rubber, ethylene-vinyl acetate copolymers, polyvinyl acetate, polyacrylic esters, paraffin, phosphate esters, natural rubber adhesives, etc. The adhesive may contain one type of adhesive component or multiple types of adhesive components.

[0051] The mass ratio of the adhesive component contained in the adhesive can be adjusted as appropriate, but the mass of the adhesive component relative to 100 mass of the adhesive can be more than 0 and less than 100, can be 0.1 to 70, can be 0.3 to 50, can be 0.5 to 30, or can be 1.0 to 10.

[0052] Furthermore, the filter according to the present invention is characterized in that the adhesive contains cellulose nanofibers. Nanofibers refer to fibers with an average fiber diameter of less than 1,000 μm. The term "average fiber diameter" as used herein refers to the arithmetic mean value of the fiber diameters of 50 fibers measured on an electron microscope photograph taken at 2000x magnification of the cross section of the object being measured. Furthermore, if the fiber diameter is too small to measure, it can be measured on an electron microscope photograph at a magnification greater than 2000x. If the cross-sectional shape of the fiber is not a solid circle, the fiber diameter is considered to be the diameter of a circle having the same area as the cross-sectional area of ​​the fiber.

[0053] The cellulose nanofibers referred to here are nanofibers containing cellulose, and commercially available cellulose nanofibers or conventionally known cellulose nanofibers can be used.

[0054] In addition to single cellulose nanofibers, the cellulose may be in the form of cellulose microfibril bundles, which are formed by loosely bundling several cellulose nanofibers together and exist as basic units in the cell wall, or microfibrillated cellulose, which is formed by bundling microfibril bundles of several tens to several hundreds of nanometers to form a spider web-like network.

[0055] Other examples include cellulose nanofibers prepared by chemical treatment using TEMPO-catalyzed oxidation or sulfuric acid esterification, cellulose nanofibers prepared using enzymatic hydrolysis, cellulose nanofibers prepared using iodine, needle-shaped cellulose nanoelements (cellulose nanocrystals) obtained by treatment with strong acid, and bacterial cellulose.

[0056] Furthermore, the cellulose nanofibers may be prepared using a high-pressure homogenizer method, a microfluidizer method, an underwater counter-collision method, a grinder grinding method, a freeze-pulverization method, an ultrasonic fiberization method, a high-speed stirring method, a bead mill method, or the like.

[0057] As a result of continued research, the applicant of the present application discovered that by including cellulose nanofibers in addition to the adhesive component in the adhesive, it is possible to create a filter that makes it difficult for the objects to be captured to flow downstream.

[0058] Although the reason for this is not entirely clear, it is thought to be due to the following effect: The presence of cellulose nanofibers allows the adhesive components in the adhesive to remain dispersed without unintentional aggregation, so the adhesive is distributed without clumping, making it possible to realize a filter equipped with a fabric to which the adhesive is uniformly attached. As a result, it is possible to provide a filter that makes it difficult for the objects to be captured to flow downstream.

[0059] The mass ratio of the adhesive component to the cellulose nanofibers contained in the adhesive can be adjusted as appropriate, but the mass of the cellulose nanofibers relative to 100 mass of the adhesive component can be 0.01 to 20, 0.05 to 10, or 0.1 to 8.

[0060] The adhesive may also contain additives such as flame retardants (halogen-based flame retardants, metal hydroxide-based flame retardants, phosphorus-based flame retardants), fragrances, pigments, antiviral agents, antibacterial agents, antifungal materials, photocatalytic particles, activated carbon, and inorganic particles.

[0061] The mass of the adhesive attached to the fabric can be adjusted as appropriate, but in order to provide a filter that does not unintentionally clog the pores of the fabric, has lower pressure loss and excellent collection properties, and is easy to maintain filtration performance for a long period of time, the percentage of the mass of the adhesive relative to the mass of the fabric can be 1 to 70 mass%, 5 to 50 mass%, or 10 to 30 mass%.

[0062] The various configurations of the fabric to which the pressure-sensitive adhesive of the present invention is attached, such as thickness and basis weight, are not particularly limited, but can be appropriately adjusted to provide a filter that has lower pressure loss and excellent collection ability, and that is likely to maintain filtration performance for a long period of time, and to provide a filter in which the pressure-sensitive adhesive and the objects to be collected held by the pressure-sensitive adhesive are less likely to fall off. The thickness can be 3 to 50 mm, 5 to 40 mm, or 10 to 30 mm. The basis weight can be 10 to 1000 g / m. 2 and can be 100 to 700 g / m 2 and can be 200 to 500 g / m 2 It can be.

[0063] The fabric with the adhesive attached thereto obtained as described above can be used alone as a filter. However, the fabric may also be used as a filter by providing a pre-filter layer or a back filter layer. In this case, the materials constituting the pre-filter layer or back filter layer can be appropriately selected, and for example, another fabric, a porous film, or a breathable foam can be used.

[0064] Next, an example of a method for manufacturing a filter according to the present invention will be described. (Step 1) preparing a fabric; (Step 2) preparing an adhesive component and cellulose nanofibers; (Step 3) adding the adhesive component and the cellulose nanofibers to a solvent or dispersion medium to prepare an adhesive solution or adhesive dispersion; (Step 4) applying the pressure-sensitive adhesive solution or the pressure-sensitive adhesive dispersion to the fabric; (Step 5) removing the solvent or the dispersion medium from the fabric to which the PSA solution or the PSA dispersion has been applied; It can be prepared by a manufacturing method having the following steps.

[0065] (Step 3) will be explained. The type of solvent or dispersion medium can be selected as appropriate, but it is preferable to use a solvent that dissolves the adhesive component but does not dissolve the cellulose nanofibers, or a dispersion medium that does not dissolve the adhesive component and the cellulose nanofibers, so that the adhesive solution or dispersion can be suitably applied to the fabric. The adhesive solution or dispersion may also contain additives.

[0066] (Step 4) will be explained. The method for applying the PSA solution or PSA dispersion to the fabric can be appropriately selected, for example, a method of applying the PSA solution or PSA dispersion to the fabric directly or in a foamed state using a spray or a gravure roll, or a method of immersing the fabric in the PSA solution or PSA dispersion can be used.

[0067] (Step 5) will be explained. The method for removing the solvent or dispersion medium can be appropriately selected, and for example, the solvent or dispersion medium can be evaporated and removed by heating in a heater such as an oven dryer, far-infrared heater, dry heat dryer, or hot air dryer, or by leaving the mixture at room temperature or in a reduced pressure atmosphere. The heating temperature when removing the solvent or dispersion medium is a temperature at which the solvent or dispersion medium can volatilize, and the lower and upper limits of the heating temperature are selected so as to prevent unintended deterioration of components contained in the fabric or adhesive.

[0068] When the fabric contains heat-fusible fibers as constituent fibers, the constituent fibers of the fabric may be bonded together by heat-fusible bonding of the heat-fusible fibers in this step.

[0069] After being subjected to a heater to remove the solvent or dispersion medium, the heated fabric to which the pressure-sensitive adhesive is attached is cooled or allowed to cool.

[0070] The fabric having the adhesive attached thereto obtained as described above can be used as a filter by itself, or can be punched out and used as a filter. However, the fabric may also be used as a filter by providing a pre-filter layer or a back-filter layer on the fabric, in which case the materials constituting the pre-filter layer or back-filter layer can be appropriately selected, and for example, another fabric, a porous film, or a breathable foam can be used.

[0071] The filter according to the present invention can be used in a flat plate form, but it may also be used after undergoing secondary processing such as pleating or corrugating, providing an edge band, or electrostatic charging or hydrophilization.

[0072] The method of using the filter can be adjusted as appropriate, but in the case of a filter having a fabric with a coarse layer and a dense layer, it is preferable to use the filter with the coarse layer positioned on the inflow side of the material to be filtered, so that the pressure loss is low, the collection efficiency is higher, and the material to be collected is less likely to flow downstream. [Example]

[0073] The present invention will be specifically described below with reference to examples, but these examples are not intended to limit the scope of the present invention.

[0074] (Preparing laminated nonwoven fabric) First, the fibers described below were mixed and fed to a carding machine to form a first fiber web (basis weight: 140 g / m 2 , apparent density: 0.016 g / cm 3 ) was prepared. Core-sheath composite fiber A (core component: polypropylene, sheath component: polyethylene (melting point: 130°C), fineness: 1.7 dtex, fiber length: 51 mm): 25 parts by weight Core-sheath composite fiber B (core component: polypropylene, sheath component: polyethylene (melting point: 130°C), fineness: 3.3 dtex, fiber length: 51 mm): 35 parts by weight Core-sheath composite fiber C (core component: polypropylene, sheath component: polyethylene (melting point: 130°C), fineness: 3.3 dtex, fiber length: 64 mm): 40 parts by weight Next, the fibers described below were mixed and fed to a carding machine to produce a second fiber web (basis weight: 130 g / m 2 , apparent density: 0.013 g / cm 3 ) was prepared. Core-sheath composite fiber B: 45 parts by weight Core-sheath composite fiber D (core component: polypropylene, sheath component: polyethylene (melting point: 130°C), fineness: 3.3 dtex, fiber length: 64 mm, hindered amine flame retardant kneaded in as an additive): 45 parts by weight Core-sheath composite fiber E (core component: polypropylene, sheath component: polyethylene (melting point: 130°C), fineness: 16.0 dtex, fiber length: 76 mm): 10 parts by weight The first fiber web and the second fiber web were simply laminated together and subjected to a heat treatment in this state, melting only the sheath component of the core-sheath composite fiber and heat-melting the constituent fibers together. After that, the nonwoven fabric (basis weight: 270 g / m) was obtained by allowing it to cool. 2 , thickness: 19 mm) was prepared. Next, a heat-bonded net (basis weight: 18 g / m) made of polyethylene resin with a melting point of 109 °C was applied. 2 A refrigerant battery (Warif (registered trademark), model number SS28L, manufactured by ENEOS Techno Materials Corporation) was prepared. The thermally bonded net was simply laminated on the main surface of the nonwoven fabric on the side of the fiber layer derived from the first fiber web, and was then placed in a heat drum (heating temperature: approximately 130°C) in this state to melt the thermally bonded net and fuse it to the nonwoven fabric. After that, the laminated nonwoven fabric (basis weight: 288 g / m) was formed by allowing it to cool. 2 , thickness: 19 mm) was prepared.

[0075] Example 1 An adhesive dispersion having the following composition was prepared. Aqueous dispersion of phosphorus-based flame retardant (solids concentration: 67% by mass): 30.0 parts by mass ·Polybutene particles (average molecular weight: 2300): 0.3 parts by mass Cellulose nanofiber aqueous dispersion (solid content: 5% by mass): 0.5 parts by mass Green pigment: trace amount ·Water: 69.2 parts by mass The foamed adhesive dispersion was then applied to the main surface of the laminated nonwoven fabric derived from the thermal adhesive net, and the laminated nonwoven fabric was then squeezed with a mangle roll to remove any unnecessary adhesive dispersion. The laminated nonwoven fabric was then dried in a hot air heater (heating temperature: 130°C). The laminated nonwoven fabric was then allowed to cool, revealing the adhesive-adhered laminated nonwoven fabric (basis weight: 331 g / m²). 2 , Adhesive weight: 43g / m 2 , thickness: 18 mm) was prepared. The thus prepared laminated nonwoven fabric having the adhesive attached thereto was used as a filter.

[0076] (Comparative Example 1) An adhesive dispersion having the following composition was prepared. The prepared adhesive dispersion had a higher viscosity than the adhesive dispersion prepared in Example 1. Aqueous dispersion of phosphorus-based flame retardant (solids concentration: 67% by mass): 30.0 parts by mass ·Polybutene particles (average molecular weight: 2300): 0.3 parts by mass Green pigment: trace amount (same parts by weight as in Example 1) ·Water: 69.7 parts by mass A laminated nonwoven fabric (basis weight: 333 g / m) to which the PSA was attached was prepared in the same manner as in Example 1, except that the PSA dispersion thus prepared was used. 2 , Adhesive weight: 45g / m 2 , thickness: 18 mm) was prepared. The thus prepared laminated nonwoven fabric having the adhesive attached thereto was used as a filter.

[0077] The filters prepared in the comparative examples and examples all had a laminated structure of a fiber layer with a high apparent density (dense layer) derived from the first fiber web and a fiber layer with a low apparent density (coarse layer) derived from the second fiber web. The same type of fiber (particularly the same fiber, sheath-core composite fiber B) was present throughout the thickness of the fabric, and the PSA was present throughout the entire thickness of the filter.

[0078] (Method for checking adhesive adhesion and results) In the filters prepared in Example 1 and Comparative Example 1, the main surfaces derived from the thermal adhesive net were visually inspected by a human.

[0079] As a result of the confirmation, it was found that the green color unevenness on the main surface was less in Example 1 than in Comparative Example 1. The green color was derived from the green pigment contained in the adhesive. Therefore, it was found that the adhesive was more uniformly attached in the filter prepared in Example 1 than in the filter prepared in Comparative Example 1.

[0080] (Method for checking dust retention performance and results) Circular samples (diameter: 110 mm) were collected from the filters prepared in Comparative Example 1 and Example 1. The samples were then placed on the vibration section of a vibration tester (IDEX (registered trademark) BF-50UT) with filter paper between them. The main surface of the filter, derived from the thermally bonded net, was exposed. Next, 1 g of one of the 11 test powders described in JIS Z8901:2006 "Test Powders and Test Particles" was placed on the center of the exposed main surface of the sample. The vibration tester was then operated with 10 to 55 Hz vibration for 1 minute (SWEEEP mode setting) as one cycle.

[0081] As a result, in the filter of Comparative Example 1, the test powder flowed out onto the main surface of the filter paper after 15 cycles (15 minutes) of operation of the vibration tester. On the other hand, in the filter of Example 1, the test powder did not flow out onto the main surface of the filter paper even after 15 cycles of operation of the vibration tester.

[0082] From the above, it has been found that the present invention can provide a filter that makes it difficult for objects to be collected to flow downstream. [Industrial Applicability]

[0083] The filter of the present invention can be suitably used as a gas filter or a liquid filter in, for example, food or medical product production factories, precision equipment manufacturing factories, indoor crop cultivation facilities, general households, industrial facilities such as hospitals and office buildings, electrical appliances such as air purifiers and office automation equipment, and various vehicles such as automobiles and aircraft.

Claims

1. A filter comprising a fabric having an adhesive attached thereto, The adhesive contains an adhesive component and cellulose nanofibers. filter.

2. The same type of fiber is present throughout the thickness of the fabric. The filter of claim 1 .

3. The fabric has a coarse layer and a dense layer. The filter according to claim 1 or claim 2.