Cylindrical filter and manufacturing method for the same

Abstract

To provide a cylindrical filter improved in filtration efficiency or filtration service life, and a manufacturing method for the same.SOLUTION: The cylindrical filter includes a filtration layer (3) wound around a core material (2). The filtration layer (3) includes a filtration layer A (310) and a filtration layer B (320). The filtration layer A (310) includes a fiber assembly A (311), and the filtration layer B (320) includes a fiber assembly B (321). A ratio PA / PB of an average pore diameter PA of the fiver assembly A (311) to an average pore diameter PB of the fiber assembly B (321) is 0.10 or more and 0.90 or less. At least either of the fiber assembly A (311) and the fiber assembly B (321) is larger in average fiber diameter than the fiber assembly A and the fiber assembly B, and is wound around while being overlapped with coarse non-woven cloths (312 and 322) in which ventilation rate and / or loads (N) that are needed during 30% compression and / or a compression rate under 100N loads satisfy a predetermined range.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cylindrical filter suitable for filtering fluids, particularly liquids containing foreign matter, and a method for manufacturing the same. [Background technology]

[0002] Cylindrical filters, which are made by winding a fiber assembly into a cylindrical shape, are easy to handle and are therefore widely used for filtering various liquids, such as beverages, chemical solutions, oils and fats, paints, and industrial cleaning water, such as cleaning water for electronic components and semiconductor products. Cylindrical filters typically have a filtration layer made of a cylindrical fiber assembly, such as a nonwoven fabric, wound around a core material. For example, Patent Document 1 describes a cylindrical filter including a filtration layer formed by stacking a fine nonwoven fabric and a large-fineness spunlace nonwoven fabric, the large-fineness nonwoven fabric comprising constituent fibers, including thermally bondable fibers having a fineness greater than that of the constituent fibers of the fine nonwoven fabric, the constituent fibers being entangled with each other and at least partially thermally bonded, in a substantially non-thermally bonded state and wound into a cylindrical shape.

[0003] Meanwhile, in the filtration of various liquids, there is a demand for smaller solid particle sizes that can be captured by cylindrical filters, i.e., higher filtration efficiency, and at the same time, there is a demand for a larger filtration volume of liquid that can pass through a single cylindrical filter, i.e., a longer filtration life. For example, Patent Documents 2 to 5 disclose cylindrical filters in which the fiber diameter and / or pore size of the fabric on the side closer to the inlet side, where the object to be filtered flows into the cylindrical filter, is larger, and the fiber diameter and / or pore size of the fabric on the side closer to the outlet side, where the object to be filtered flows out of the cylindrical filter, is smaller, thereby achieving both filtration efficiency and filtration life. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-000851 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-236985 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-236986 [Patent Document 4] Japanese Patent Application Laid-Open No. 2015-93259 [Patent Document 5] International Publication No. 2021 / 220720 Summary of the Invention [Problem to be solved by the invention]

[0005] However, as described in Patent Documents 1 to 5, even if a gradient is provided in the fiber diameter and / or pore diameter of the fabric constituting the filtration layer of a cylindrical filter, there is a problem that the filtration efficiency and filter life are insufficient.

[0006] In order to solve the above-mentioned problems of the prior art, the present invention provides a cylindrical filter having improved filtering efficiency or filter life, and a method for manufacturing the same. [Means for solving the problem]

[0007] The present invention relates to a cylindrical filter including a filtration layer wound around a core material, the filtration layer including filtration layer A and filtration layer B wound continuously in order from the outlet side of the material to be filtered, the filtration layer A including a fiber assembly A, and the filtration layer B including a fiber assembly B, the average pore size PA of the fiber assembly A and the average pore size PB of the fiber assembly B being different, and the average pore size PA / average pore size PB is 0.05 or more and 0.95 or less, at least one of the fiber assembly A and the fiber assembly B being wound in a state of being overlapped with a coarse nonwoven fabric, the coarse nonwoven fabric having a larger average fiber diameter than both the fiber assembly A and the fiber assembly B, and the cylindrical filter satisfying at least one of the following (i), (ii), and (iii): (i) Air permeability is 150 cm 3 / (cm 2 ·s) more than 500cm 3 / (cm 2·s) or less (ii) The load (N) required to compress it to 30% is 50N or more and 1500N or less. (iii) Compression rate under a 100N load is 25% or more and 70% or less

[0008] The present invention is a method for producing a cylindrical filter including a filtration layer wound around a core material, the filtration layer including a filtration layer A and a filtration layer B wound in order around the core material, and includes a winding step A to form the filtration layer A by winding only a fiber aggregate A around the core material for a predetermined length, or by winding the fiber aggregate A and a coarse nonwoven fabric together for a predetermined length so that the fiber aggregate A is closer to the core material than the coarse nonwoven fabric, and a winding step B to form the filtration layer A by winding only a fiber aggregate B around the filtration layer A for a predetermined length, or by winding the fiber aggregate B and the coarse nonwoven fabric together for a predetermined length so that the fiber aggregate B is closer to the filtration layer A than the coarse nonwoven fabric, the average pore size PA of the fiber assembly A is different from the average pore size PB of the fiber assembly B, and the average pore size PA / average pore size PB is 0.05 or more and 0.95 or less; the coarse nonwoven fabric has an average fiber diameter larger than both of the fiber assembly A and the fiber assembly B and satisfies at least one of the following (i), (ii), and (iii); and at least one of the fiber assembly A and the fiber assembly B is wound in a state of being overlapped with the coarse nonwoven fabric. (i) Air permeability is 150 cm 3 / (cm 2 ·s) more than 500cm 3 / (cm 2 ·s) or less (ii) The load (N) required to compress it to 30% is 50N or more and 1500N or less. (iii) Compression rate under a 100N load is 25% or more and 70% or less [Effects of the Invention]

[0009] The present invention can provide a cylindrical filter having improved filtration efficiency or filter life. Furthermore, the manufacturing method of the present invention can provide a cylindrical filter having improved filtration efficiency and filter life. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic, partially cutaway, perspective cross-sectional view of an example of a cylindrical filter of the present invention. [Figure 2] FIG. 1 is a schematic process diagram illustrating an example of a method for producing a cylindrical filter according to the present invention. [Figure 3] FIG. 1 is a schematic process diagram illustrating an example of a method for producing a cylindrical filter according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The inventors of the present invention conducted extensive research to solve the above-mentioned problems. As a result, they found that in a cylindrical filter including a core material and filtration layers A and B wound in order around the core material, the filtration efficiency and filtration life of the cylindrical filter can be improved by providing a gradient in the average pore size of fiber aggregate A contained in filtration layer A and fiber aggregate B contained in filtration layer B, and winding at least one of fiber aggregate A and fiber aggregate B in a state where it is overlapped with a coarse nonwoven fabric having a larger average fiber diameter than either fiber aggregate A or fiber aggregate B and having predetermined air permeability and / or compressibility. In this specification, the state in which the fiber aggregate is overlapped with the coarse nonwoven fabric means that the fiber aggregate and the coarse nonwoven fabric are merely stacked and in contact with each other in the thickness direction, with no interlayer adhesion.

[0012] <Cylindrical filter> The cylindrical filter includes a core material and a filtration layer wound around the core material.

[0013] (filtration layer) The filtration layer includes at least a filtration layer A and a filtration layer B wound continuously in this order from the outflow side to the inflow side of the object to be filtered. The filtration layer A includes a fiber assembly A, and the filtration layer B includes a fiber assembly B. The average pore diameter PA of the fiber assembly A is different from the average pore diameter PB of the fiber assembly B, and at least one of the fiber assembly A and the fiber assembly B has a larger average fiber diameter than both the fiber assembly A and the fiber assembly B, and has an air permeability of 150 cm 3 / (cm 2 ·s) more than 500cm 3 / (cm 2 s) or less, and / or the load (N) required to compress it to 30% is 50N to 1500N, and / or the compressibility under a load of 100N is 25% to 70%. In the following, unless otherwise specified, the coarse nonwoven fabric has an average fiber diameter larger than both fiber aggregate A and fiber aggregate B, and an air permeability of 150cm 3 / (cm 2 ·s) more than 500cm 3 / (cm 2 This refers to a nonwoven fabric having a compressibility of 25% to 70% under a load of 100N or more, and / or a load (N) of 50N to 1500N when compressed to 30% or less, and / or a compressibility of 25% to 70% under a load of 100N or more.

[0014] At least one of the fiber aggregates A and B is wound in a state overlapped with the coarse nonwoven fabric. This creates gaps between the layers of the fiber aggregates A and / or B that make up the filtration layer A and / or filtration layer B, compared to when the fiber aggregates A and / or B are wound alone. This allows the coarse nonwoven fabric to capture primarily large-sized objects to be filtered, and the use of the coarse nonwoven fabric allows the diffusion of fluid containing the objects to be filtered. This suppresses clogging of the fiber aggregates A and / or B, and therefore tends to improve the filtration efficiency and filter life of the cylindrical filter. The air permeability of the coarse nonwoven fabric is 150 cm 3 / (cm 2 When the air permeability of the coarse nonwoven fabric is 500 cm or more, the voids in the filtration layer are sufficient, and more foreign matter can be captured in the voids. 3 / (cm 2When the air permeability is less than 1 / s, adhesion between the fiber aggregates is suppressed, and at the same time, the fibers constituting the coarse nonwoven fabric are effective in capturing foreign matter, and the coarse nonwoven fabric itself can contribute to capturing foreign matter. Furthermore, the random structure formed between the fibers constituting the coarse nonwoven fabric has a fluid diffusion effect, allowing the fiber aggregate to be used for filtration over a wide area. In this specification, air permeability can be measured as described in the examples.

[0015] The air permeability of the coarse nonwoven fabric is set to 150 cm from the viewpoint of easily improving both filtration efficiency and filter life. 3 / (cm 2 ·s) more than 500cm 3 / (cm 2 s) or less, and 175cm 3 / (cm 2 ·s) over 450cm 3 / (cm 2 s) or less, and 200 cm 3 / (cm 2 ·s) more than 400cm 3 / (cm 2 It is more preferable that the value is equal to or less than s.

[0016] From the viewpoint of being more excellent in load resistance and being able to maintain its thickness when used for filtration, the load required when the coarse nonwoven fabric is compressed to 30% is preferably 50 N or more and 1500 N or less, more preferably 100 N or more and 1000 N or less, and even more preferably 150 N or more and 800 N or less. In this specification, the load required when compressed to 30% can be measured as described in the Examples.

[0017] From the viewpoint of having better load-bearing capacity and being able to maintain thickness when a large amount of filtration is performed, the coarse nonwoven fabric preferably has a compressibility under a load of 100 N of 25% or more and 70% or less, more preferably 27% or more and 65% or less, and even more preferably 30% or more and 60% or less.

[0018] The bending resistance of the coarse nonwoven fabric in the machine direction, i.e., the winding direction (MD), is not particularly limited as long as the breathability and compression characteristics satisfy the above-mentioned ranges. For example, it is preferably 1.0 mN·cm to 30 mN·cm, more preferably 1.5 mN·cm to 25 mN·cm, and even more preferably 2.0 mN·cm to 20 mN·cm. If the machine direction bending resistance of the coarse nonwoven fabric is 1.0 mN·cm or more, the coarse nonwoven fabric can be easily wound up during production. If the machine direction bending resistance of the coarse nonwoven fabric is 30 mN·cm or less, winding up during production is not hindered.

[0019] The bending resistance in the cross direction (CD) of the coarse nonwoven fabric is not particularly limited as long as the breathability and compression characteristics satisfy the above-mentioned ranges. For example, it is preferably 0.5 mN·cm to 20 mN·cm, more preferably 0.7 mN·cm to 15 mN·cm, and even more preferably 1.0 mN·cm to 10 mN·cm. If the cross direction bending resistance of the coarse nonwoven fabric is 0.5 mN·cm or more, it can easily accommodate the slight curvature of the core material in the width direction. If the cross direction bending resistance of the coarse nonwoven fabric is 20 mN·cm or less, it can easily be inserted evenly across the entire width without excessive bending in the width direction during production. In this specification, bending resistance can be measured as described in the Examples.

[0020] The average fiber diameter of the coarse nonwoven fabric is not particularly limited as long as it is larger than both fiber aggregate A and fiber aggregate B and the air permeability and compression characteristics satisfy the above-mentioned ranges. For example, it is preferably 40 μm to 120 μm, more preferably 50 μm to 110 μm, and even more preferably 55 μm to 100 μm. When the average fiber diameter of the coarse nonwoven fabric is 40 μm or more, the inter-fiber voids (inter-fiber structure) formed between the fibers constituting the coarse nonwoven fabric can withstand pressure, making it easier to ensure voids. When the average fiber diameter of the coarse nonwoven fabric is 120 μm or less, the number of fibers constituting the coarse nonwoven fabric increases for the same basis weight, which is thought to allow the fibers to capture foreign matter and contribute to filtration. In this specification, the average fiber diameter can be measured as described in the examples.

[0021] The average fineness of the coarse nonwoven fabric is not particularly limited as long as the breathability and compression characteristics satisfy the above-mentioned ranges. For example, it is preferably more than 10 dtex and not more than 120 dtex, more preferably 12 dtex to 100 dtex, even more preferably 15 dtex to 80 dtex, and even more preferably 20 dtex to 70 dtex. When the average fineness of the coarse nonwoven fabric exceeds 10 dtex, the fibers constituting the coarse nonwoven fabric are less susceptible to pressure applied during filtration, making it easier to maintain voids. When the average fineness of the coarse nonwoven fabric is 120 dtex or less, the filtration effect of the fibers of the coarse nonwoven fabric makes it possible to capture more foreign matter. In this specification, the average fineness can be measured as described in the examples.

[0022] The basis weight of the coarse nonwoven fabric is not particularly limited as long as the breathability and compressibility satisfy the above-mentioned ranges. For example, from the viewpoint of ensuring the number of fibers that contribute to filtration, it is 15 g / m 2 More than 80g / m 2 Preferably, it is 20 g / m or less. 2 More than 65g / m 2 More preferably, it is 25 g / m or less. 2 More than 50g / m 2 It is more preferable that the basis weight is not more than 10 ...

[0023] The thickness of the coarse nonwoven fabric is not particularly limited as long as the breathability and compression characteristics satisfy the above-mentioned ranges, but from the viewpoint of maintaining the fineness of the constituent fibers, it is preferably 0.2 mm to 2.5 mm, more preferably 0.4 mm to 2.0 mm, and even more preferably 0.6 mm to 1.8 mm. In this specification, the thickness can be measured in accordance with JIS L 1913.

[0024] The density of the coarse nonwoven fabric is not particularly limited as long as the breathability and compression characteristics satisfy the above-mentioned ranges. For example, from the viewpoint of increasing the voids, it is preferably 0.006 g / cm 3 More than 0.400g / cm3 Preferably, it is 0.008 g / cm or less. 3 More than 0.300g / cm 3 More preferably, it is 0.010 g / cm or less. 3 More than 0.200g / cm 3 More preferably, it is 0.013 g / cm or less. 3 More than 0.100g / cm 3 It is more preferable that the density is as follows: In this specification, the density can be measured as described in the examples.

[0025] The tensile strength of the coarse nonwoven fabric in the winding direction (MD) is not particularly limited as long as the breathability and compression characteristics satisfy the above-mentioned ranges. However, for example, from the viewpoint of preventing breakage of the nonwoven fabric when winding the filter during production, it is preferably 5 N / 5 cm to 100 N / 5 cm, more preferably 6 N / 5 cm to 90 N / 5 cm, and even more preferably 7 N / 5 cm to 80 N / 5 cm. The tensile strength of the coarse nonwoven fabric in the cross direction (CD) is not particularly limited as long as the breathability and compression characteristics satisfy the above-mentioned ranges. However, for example, from the viewpoint of preventing breakage due to the influence of width adjustment when winding the filter during production, it is preferably 1 N / 5 cm to 30 N / 5 cm, more preferably 1.5 N / 5 cm to 20 N / 5 cm, and even more preferably 2.0 N / 5 cm to 20 N / 5 cm. In this specification, the tensile strength of the nonwoven fabric can be measured according to JIS L 1913.

[0026] The elongation percentage in the machine direction (MD) of the coarse nonwoven fabric is not particularly limited as long as the breathability and compression properties satisfy the above-mentioned ranges. However, for example, from the viewpoint of suppressing width adjustment of the nonwoven fabric due to the influence of tension during production, it is preferably 5% to 40%, more preferably 7% to 35%, and even more preferably 10% to 30%. The elongation percentage in the cross direction (CD) of the coarse nonwoven fabric is not particularly limited as long as the breathability and compression properties satisfy the above-mentioned ranges. However, for example, from the viewpoint of suppressing the influence of tension and tensile strength during production, it is preferably 10% to 90%, more preferably 15% to 85%, and even more preferably 20% to 80%. In this specification, the elongation percentage of the nonwoven fabric can be measured in accordance with JIS L 1913.

[0027] The type of coarse nonwoven fabric is not particularly limited as long as its breathability and compression characteristics satisfy the above-mentioned ranges. For example, it may be a short-fiber nonwoven fabric (e.g., a nonwoven fabric composed of single fibers having a fiber length of 3 mm or more and 110 mm or less) or a long-fiber nonwoven fabric. It is preferable that the fibers constituting the coarse nonwoven fabric are bonded to each other at least at some of the fiber intersections where they come into contact with each other. In the case of a short-fiber nonwoven fabric, one or more selected from the group consisting of a thermal-bonded nonwoven fabric, a point-bonded nonwoven fabric, a calendered nonwoven fabric, and a chemical-bonded nonwoven fabric are more preferable, and one or more selected from the group consisting of an air-through nonwoven fabric and a chemical-bonded nonwoven fabric are even more preferable, with an air-through nonwoven fabric being even more preferable. In the case of a long-fiber nonwoven fabric, one or more selected from the group consisting of a spun-bonded nonwoven fabric, a melt-blown nonwoven fabric, a point-bonded nonwoven fabric, and a calendered nonwoven fabric are preferred. In this specification, the term "through-air nonwoven fabric" refers to a thermally bonded nonwoven fabric formed by integrating a carded web (a web made by carding) or an air-laid web (a web made by the air-laid method) containing thermally adhesive fibers using the non-contact heating method of air-through (hot air penetration).

[0028] The coarse nonwoven fabric can be made of any natural or synthetic fiber, but synthetic fibers made of thermoplastic resins are preferred. Examples of thermoplastic resins include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid, and polybutylene succinate; polyethylene resins such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and ultra-high molecular weight polyethylene; polypropylene resins such as isotactic, atactic, and syndiotactic polypropylene resins; polymethylpentene resin, polybutene-1 resin, ethylene-vinyl alcohol copolymer resin, and ethylene-propylene copolymer resin; polyamide resins such as nylon 6, nylon 66, nylon 11, and nylon 12; and engineering plastics such as polycarbonate, polyacetal, polystyrene, cyclic polyolefin, and polyphenylene sulfide (polyphenylene sulfide).

[0029] When the coarse nonwoven fabric is a thermal bonded nonwoven fabric such as an air-through nonwoven fabric, it preferably contains 50% by mass or more of thermal adhesive fibers, more preferably 80% by mass or more, and even more preferably consists of thermal adhesive fibers alone. The raw material for the thermal adhesive fibers is not particularly limited as long as it is a thermoplastic resin having melt spinnability. Examples of suitable thermo-adhesive fibers include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid, and polybutylene succinate; polyethylene resins such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and ultra-high molecular weight polyethylene; polypropylene resins such as isotactic, atactic, and syndiotactic polypropylene; polyolefin resins such as polymethylpentene resin, polybutene-1 resin, ethylene-vinyl alcohol copolymer resin, and ethylene-propylene copolymer resin; polyamide resins such as nylon 6, nylon 66, nylon 11, and nylon 12; and engineering plastics such as polycarbonate, polyacetal, polystyrene, cyclic polyolefin, and polyphenylene sulfide. The cross-sectional shape of the thermo-adhesive fiber is not particularly limited and may be circular, elliptical, triangular, polygonal, or multi-lobed. The fiber may be either a mono-fiber or a bi-component fiber. Furthermore, in the case of composite fibers, the cross-sectional shape of the fiber is not particularly limited, and may be any of a core-sheath type, an eccentric core-sheath type, a segmented type, a side-by-side type, and an islands-in-sea type. From the viewpoints of fiber strength, productivity, and the chemical resistance of the resulting core material, it is preferable to use polyolefin-based fibers made of polyolefin-based resins such as polyethylene resin, polypropylene resin, polymethylpentene resin, polybutene-1 resin, ethylene-vinyl alcohol copolymer resin, and ethylene-propylene copolymer resin. Regarding the fiber configuration, it is preferable to use polyolefin-based core-sheath composite fibers in which both the core component and the sheath component are made of polyolefin-based resins, from the viewpoints of productivity and production costs of the thermally adhesive fiber.The thermal adhesive fiber is not limited to a polyolefin-based sheath-core conjugate fiber, and conjugate fibers other than a polyolefin-based sheath-core conjugate fiber can be appropriately selected and used depending on the performance required for the cylindrical filter of the present invention. If the cylindrical filter is used in an application requiring heat resistance, it is preferable to use conjugate fibers containing a polyester resin, a polyamide resin, polycarbonate, and polyphenylene sulfide, and it is more preferable to use polyester-based sheath-core conjugate fibers in which the core component and the sheath component both contain a polyester resin, polyamide-based sheath-core conjugate fibers in which the core component and the sheath component both contain a polyamide resin, or a core-sheath conjugate fiber in which a polyester resin and a polyamide resin are combined.

[0030] When the thermally adhesive fiber is a core-sheath composite fiber, it is advantageous for thermal adhesive processing to select a resin for the sheath component whose melting point is at least 20°C lower than that of the core component. Preferred combinations of sheath and core components include, for example, polyethylene resin and polypropylene resin, ethylene-propylene copolymer resin and polypropylene resin, polybutene-1 resin and polypropylene resin, polyethylene resin and polymethylpentene resin, polypropylene resin and polymethylpentene resin, ethylene-propylene copolymer resin and polymethylpentene resin, polyethylene resin and polyethylene terephthalate, polypropylene resin and polyethylene terephthalate, ethylene-propylene copolymer resin and polyethylene terephthalate, low-melting point polyester and high-melting point polyester, polyethylene terephthalate and nylon 6,6, polyethylene terephthalate and nylon 6, and polyethylene resin and nylon 6. From the viewpoints of fiber strength, productivity, and chemical resistance, combinations containing at least one polyolefin-based resin component are preferred, more preferably combinations in which both the core and sheath components are polyolefin-based resins, and even more preferably combinations in which the core component is polypropylene resin and the sheath component is polyethylene resin.

[0031] A thermal-bonded nonwoven fabric such as an air-through nonwoven fabric may contain up to 50% by mass, or up to 20% by mass, of fibers other than the thermal adhesive fibers. The other fibers are not particularly limited, and examples thereof include natural fibers such as cotton, regenerated fibers such as rayon, semi-synthetic fibers such as acetate, and synthetic fibers such as polyolefin fibers, polyester fibers, polyamide fibers, and acrylic fibers.

[0032] The filtration layer A can include one or more selected from the group consisting of a filtration layer A1 in which a fiber assembly A and a coarse nonwoven fabric are wound in a superimposed state, and a filtration layer A2 in which only the fiber assembly A is wound. When the filtration layer A includes the filtration layer A1, it is desirable that in the filtration layer A1, the fiber assembly A and the coarse nonwoven fabric are stacked and wound around the core material so that the fiber assembly A is closer to the core material than the coarse nonwoven fabric. When the filtration layer A includes a filtration layer A2 in addition to the filtration layer A1, the filtration layer A2 may be positioned closer to the core material than the filtration layer A1.

[0033] The filtration layer B may include one or more selected from the group consisting of a filtration layer B1 in which a fiber assembly B and a coarse nonwoven fabric are wound in a superimposed state, and a filtration layer B2 in which only the fiber assembly B is wound. When the filtration layer B includes the filtration layer B1, it is desirable that in the filtration layer B1, the fiber assembly B and the coarse nonwoven fabric are stacked and wound around a core material so that the fiber assembly B is closer to the filtration layer A than the coarse nonwoven fabric. When the filtration layer B includes the filtration layer B2 in addition to the filtration layer B1, the filtration layer B2 may be positioned closer to the filtration layer A than the filtration layer B1.

[0034] The average pore size PA of the fiber assembly A and the average pore size PB of the fiber assembly B are different, and the ratio PA / PB is 0.05 or more and 0.95 or less. When the ratio PA / PB is within the above-mentioned range, it is easy to achieve both filtration efficiency and filtration life. When the ratio PA / PB is 0.05 or more, the fiber assembly B contained in the filtration layer B, which is located on the inlet side of the filtration layer A, easily captures large-sized solids, and it is possible to prevent oversized solids from entering the fiber assembly A contained in the filtration layer A. This prevents the fiber assembly A contained in the filtration layer A from clogging at an early stage, and it is easy to improve the filtration life of the cylindrical filter. When the ratio PA / PB is 0.95 or less, the average pore size of the fiber assembly A contained in the filtration layer A does not become large, and it is easy to improve the filtration efficiency of the cylindrical filter. From the viewpoint of improving both filtration efficiency and filtration life, the average pore size PA / average pore size PB is preferably 0.10 to 0.90, and more preferably 0.15 to 0.85. When higher filtration efficiency is required, the ratio is preferably 0.05 to 0.280, more preferably 0.10 to 0.270, and even more preferably 0.15 to 0.260. When higher filtration life is required, the ratio is preferably 0.295 to 0.950, more preferably 0.297 to 0.90, and even more preferably 0.300 to 0.850. In this specification, the average pore size of the fiber assembly can be measured as described in the Examples.

[0035] The average pore diameter PA of the fiber assembly A is not particularly limited as long as the ratio of average pore diameter PA / average pore diameter PB satisfies the above-mentioned range. However, from the viewpoint of achieving both filtration efficiency and filter life, for example, it is preferably 0.5 μm to 15.0 μm, more preferably 1.0 μm to 14.0 μm, and even more preferably 1.5 μm to 12.0 μm. When higher filtration efficiency is required, it is preferably 0.5 μm to 5.5 μm, more preferably 1.0 μm to 5.0 μm, and even more preferably 1.5 μm to 4.5 μm. When higher filtration life is required, it is preferably 9.0 μm to 35.0 μm, more preferably 10.0 μm to 30.0 μm, and even more preferably 11.0 μm to 25.0 μm.

[0036] The minimum pore size of the fiber assembly A is not particularly limited as long as the average pore size PA / average pore size PB satisfies the above-mentioned range. However, from the viewpoint of achieving both filtration efficiency and filter life, for example, it is preferably 0.1 μm to 10.0 μm, more preferably 0.5 μm to 8.0 μm, and even more preferably 1.0 μm to 6.0 μm. When higher filtration efficiency is required, it is preferably 0.1 μm to 5.0 μm, more preferably 0.5 μm to 4.5 μm, and even more preferably 1.0 μm to 4.0 μm. When higher filtration life is required, it is preferably 6.0 μm to 20.0 μm, more preferably 6.3 μm to 15.0 μm, and even more preferably 6.5 μm to 10.0 μm.

[0037] The maximum pore size of the fiber assembly A is not particularly limited as long as the average pore size PA / average pore size PB satisfies the above-mentioned range. However, for example, from the viewpoint of reliably capturing coarse particles, it is preferably 2.0 μm to 22.0 μm, more preferably 3.0 μm to 21.0 μm, and even more preferably 4.0 μm to 20.0 μm. When higher filtration efficiency is required, it is preferably 1.5 μm to 11.0 μm, more preferably 2.0 μm to 10.0 μm, and even more preferably 3.0 μm to 9.0 μm. When a longer filtration life is required, it is preferably 15.0 μm to 80.0 μm, more preferably 16.0 μm to 70.0 μm, and even more preferably 17.0 μm to 60.0 μm.

[0038] The maximum pore size of the fiber assembly A is not particularly limited as long as the average pore size PA / average pore size PB satisfies the above-mentioned range. However, for example, from the viewpoint of stabilizing filtration efficiency, it is preferably 0.5 μm to 15 μm, more preferably 1.0 μm to 13.0 μm, and even more preferably 2.0 μm to 10.0 μm. When higher filtration efficiency is required, it is preferably 0.5 μm to 5.5 μm, more preferably 1.0 μm to 5.0 μm, and even more preferably 1.5 μm to 4.5 μm. When a longer filtration life is required, it is preferably 8.0 μm to 30.0 μm, more preferably 9.0 μm to 25.0 μm, and even more preferably 10.0 μm to 20.0 μm.

[0039] The average fiber diameter of the fiber assembly A is smaller than that of the coarse nonwoven fabric, and the ratio of the average pore diameter PA to the average pore diameter PB is not particularly limited as long as it satisfies the above-mentioned range. For example, it is preferably 0.1 μm to 5.0 μm, more preferably 0.5 μm to 4.5 μm, and even more preferably 1.0 μm to 4.0 μm. When the average fiber diameter of the fiber assembly A satisfies this range, the average pore diameter easily satisfies the above-mentioned range, and both the filtration efficiency and the filtration life can be improved. When higher filtration efficiency is required, it is preferably 0.1 μm to 2.4 μm, more preferably 0.5 μm to 2.3 μm, and even more preferably 1.0 μm to 2.2 μm. When higher filtration life is required, it is preferably 2.7 μm to 12.0 μm, more preferably 2.8 μm to 9.0 μm, and even more preferably 2.9 μm to 6.0 μm.

[0040] The minimum fiber diameter of the fiber assembly A is not particularly limited as long as the average pore diameter PA / average pore diameter PB satisfies the above-mentioned range. For example, from the viewpoint of obtaining fine pore diameters due to the pore diameters between fibers with small fiber diameters, the minimum fiber diameter is preferably 0.10 μm to 2.0 μm, more preferably 0.2 μm to 1.5 μm, and even more preferably 0.25 μm to 1.0 μm. When higher filtration efficiency is required, the minimum fiber diameter is preferably 0.10 μm to 0.60 μm, more preferably 0.15 μm to 0.55 μm, and even more preferably 0.20 μm to 0.50 μm. When higher filtration life is required, the minimum fiber diameter is preferably 0.75 μm to 8.0 μm, more preferably 0.8 μm to 5.0 μm, and even more preferably 0.85 μm to 2.0 μm.

[0041] The maximum fiber diameter of the fiber assembly A is not particularly limited as long as the average pore diameter PA / average pore diameter PB satisfies the above-mentioned range. However, for example, from the viewpoint of facilitating capture of even inflowing coarse particles due to the variation, it is preferably 1.0 μm to 100 μm, more preferably 5.0 μm to 70 μm, and even more preferably 10 μm to 50 μm. When higher filtration efficiency is required, it is preferably 1.0 μm to 8.05 μm, more preferably 3.0 μm to 8.00 μm, and even more preferably 5.0 μm to 7.95 μm. When higher filtration life is required, it is preferably 8.35 μm to 100.0 μm, more preferably 8.40 μm to 75.0 μm, and even more preferably 8.45 μm to 50.0 μm.

[0042] The air permeability of the fiber assembly A is not particularly limited as long as the average pore diameter PA / average pore diameter PB satisfies the above-mentioned range. For example, from the viewpoint that the air permeability decreases as the fiber diameter becomes smaller and the filtration efficiency increases, 3 / (cm 2 ·s) more than 20cm 3 / (cm 2 s) or less, and 2 cm 3 / (cm 2 ·s) over 15cm 3 / (cm 2 s) or less is more preferable, and 3 cm 3 / (cm 2 ·s) more than 10cm 3 / (cm 2 If higher filtration efficiency is required, it is more preferable that the filtration efficiency is 1 cm or less. 3 / (cm 2 ·s) or more than 11cm 3 / (cm 2 s) or less, and 2 cm 3 / (cm 2 ·s) more than 10cm 3 / (cm 2 s) or less is more preferable, and 3 cm 3 / (cm 2·s) over 9cm 3 / (cm 2 If a longer filtration life is required, it is more preferable that the filter is 16 cm or less. 3 / (cm 2 ·s) more than 150m 3 / (cm 2 s) or less, and 17cm 3 / (cm 2 ·s) over 120cm 3 / (cm 2 s) or less is more preferable, and 18cm 3 / (cm 2 ·s) over 90cm 3 / (cm 2 It is more preferable that the value is equal to or less than s.

[0043] The average pore diameter PB of the fiber assembly B is not particularly limited as long as the ratio of the average pore diameter PA / average pore diameter PB satisfies the above-mentioned range. However, for example, from the viewpoint of easily capturing coarse particles, it is preferably 5.0 μm to 30 μm, more preferably 7.5 μm to 25 μm, and even more preferably 10 μm to 20 μm. When higher filtration efficiency is required, it is preferably 4.0 μm to 15.0 μm, more preferably 7.0 μm to 14.7 μm, and even more preferably 10.0 μm to 14.3 μm. When a longer filtration life is required, it is preferably 16.0 μm to 90 μm, more preferably 16.3 μm to 80 μm, and even more preferably 16.5 μm to 70 μm.

[0044] The minimum pore size of the fiber assembly B is not particularly limited as long as the average pore size PA / average pore size PB satisfies the above-mentioned range, but for example, from the viewpoint of capturing relatively fine particles, it is preferably 3.0 μm to 30 μm, more preferably 4 μm to 20 μm, and even more preferably 5 μm to 15 μm. When higher filtration efficiency is required, it is preferably 3.0 μm to 10.0 μm, more preferably 4.0 μm to 9.7 μm, and even more preferably 5.0 μm to 9.5 μm. When higher filtration life is required, it is preferably 11.0 μm to 25.0 μm, more preferably 11.3 μm to 20.0 μm, and even more preferably 11.5 μm to 17.0 μm.

[0045] The maximum pore size of the fiber assembly B is not particularly limited as long as the ratio of the average pore size PA to the average pore size PB satisfies the above-mentioned range. For example, from the viewpoint of preventing clogging by capturing inflowing coarse particles in the large pores, the maximum pore size is preferably 5 μm to 40 μm, more preferably 10 μm to 35 μm, and even more preferably 15 μm to 30 μm. When higher filtration efficiency is required, the maximum pore size is preferably 5.0 μm to 27.0 μm, more preferably 8.0 μm to 26.0 μm, and even more preferably 12.0 μm to 25.0 μm. When higher filtration life is required, the maximum pore size is preferably 30 μm to 300 μm, more preferably 31 μm to 250 μm, and even more preferably 32 μm to 200 μm.

[0046] The maximum pore size of the fiber assembly B is not particularly limited as long as the average pore size PA / average pore size PB satisfies the above-mentioned range. However, for example, from the viewpoint of reliably capturing coarse particles, it is preferably 5.0 μm to 20.0 μm, more preferably 8.0 μm to 17.0 μm, and even more preferably 10.0 μm to 15.0 μm. When higher filtration efficiency is required, it is preferably 4.0 μm to 13.0 μm, more preferably 6.0 μm to 12.8 μm, and even more preferably 8.0 μm to 12.6 μm. When higher filtration life is required, it is preferably 14.0 μm to 75.0 μm, more preferably 14.1 μm to 60.0 μm, and even more preferably 14.2 μm to 45.0 μm.

[0047] The average fiber diameter of the fiber aggregate B is smaller than that of the coarse nonwoven fabric, and is not particularly limited as long as the average pore diameter PA / average pore diameter PB satisfies the above-mentioned range. For example, it is preferably 1.0 μm to 10 μm, more preferably 1.5 μm to 7 μm, and even more preferably 2.0 μm to 5 μm. When the average fiber diameter of the fiber aggregate B satisfies this range, the average pore diameter easily satisfies the above-mentioned range, and both filtration efficiency and filtration life can be improved. When higher filtration efficiency is required, it is preferably 0.5 μm to 3.40 μm, more preferably 1.0 μm to 3.35 μm, and even more preferably 1.5 μm to 3.30 μm. When higher filtration life is required, it is preferably 3.70 μm to 30.0 μm, more preferably 3.75 μm to 25.0 μm, and even more preferably 3.80 μm to 20.0 μm.

[0048] The minimum fiber diameter of the fiber assembly B is not particularly limited as long as the average pore diameter PA / average pore diameter PB satisfies the above-mentioned range. For example, from the viewpoint of capturing fine foreign particles to a certain extent, the minimum fiber diameter is preferably 0.3 μm to 5.0 μm, more preferably 0.4 μm to 4.0 μm, and even more preferably 0.5 μm to 3.0 μm. When higher filtration efficiency is required, the minimum fiber diameter is preferably 0.3 μm to 1.07 μm, more preferably 0.4 μm to 1.06 μm, and even more preferably 0.5 μm to 1.05 μm. When higher filtration life is required, the minimum fiber diameter is preferably 1.08 μm to 20.0 μm, more preferably 1.09 μm to 15.0 μm, and even more preferably 1.10 μm to 10.0 μm.

[0049] The maximum fiber diameter of the fiber aggregate B is not particularly limited, as long as the average pore diameter PA / average pore diameter PB satisfies the above-mentioned range, but for example, from the viewpoint of ensuring the performance as a filter material, it is preferably 5.0 μm or more and 15 μm or less, more preferably 6.0 μm or more and 12 μm or less, and even more preferably 7.0 μm or more and 10 μm or less.When higher filtration efficiency is required, it is preferably 3.0 μm or more and 9.2 μm or less, more preferably 4.0 μm or more and 9.1 μm or less, and even more preferably 5.0 μm or more and 9.0 μm or less.When higher filtration life is required, it is preferably 9.8 μm or more and 50.0 μm or less, more preferably 9.9 μm or more and 40.0 μm or less, and even more preferably 10.0 μm or more and 30.0 μm or less.

[0050] The air permeability of the fiber assembly B is smaller than that of the coarse nonwoven fabric, and the average pore size PA / average pore size PB is required to satisfy the above-mentioned range. There are no particular limitations on this. For example, from the viewpoint of achieving both filtration efficiency and filter life, it is preferable to use a fiber assembly B having a pore size of 5 cm 3 / (cm 2 ·s) more than 50cm 3 / (cm 2 s) or less, and 10 cm 3 / (cm 2·s) over 40cm 3 / (cm 2 s) or less is more preferable, and 15 cm 3 / (cm 2 ·s) more than 30cm 3 / (cm 2 If higher filtration efficiency is required, it is more preferable that the filtration efficiency is 5 cm or less. 3 / (cm 2 ·s) over 40cm 3 / (cm 2 s) or less, and 10 cm 3 / (cm 2 ·s) or more than 35cm 3 / (cm 2 s) or less is more preferable, and 15 cm 3 / (cm 2 ·s) more than 30cm 3 / (cm 2 If a longer filtration life is required, it is more preferable that the filter is 45 cm 3 / (cm 2 ·s) or more than 340cm 3 / (cm 2 s) or less, and 50 cm 3 / (cm 2 ·s) more than 300cm 3 / (cm 2 s) or less is more preferable, and 55 cm 3 / (cm 2 ·s) over 260cm 3 / (cm 2 It is more preferable that the value is equal to or less than s.

[0051] It is preferable that the filtration layer further includes a filtration layer C wound around the inlet side of the filtration layer B for the material to be filtered, i.e., the filtration layer includes a filtration layer A, a filtration layer B, and a filtration layer C wound successively in this order from the outlet side of the material to be filtered, which tends to improve the filtration efficiency and / or the filtration life of the cylindrical filter.

[0052] The filtration layer C includes a fiber assembly C, the average fiber diameter of which is smaller than that of the coarse nonwoven fabric, and the average pore diameter PC of the fiber assembly C is different from the average pore diameter PA of the fiber assembly A and the average pore diameter PB of the fiber assembly B, and the ratio of the average pore diameter PB to the average pore diameter PC is preferably 0.05 or more and 0.95 or less. When the ratio of the average pore diameter PB to the average pore diameter PC is 0.05 or more, surface clogging of the fiber assembly C is unlikely to occur, and an improved filtration life can be expected. When the ratio of the average pore diameter PB to the average pore diameter PC is 0.95 or less, coarser foreign particles are captured, which tends to reduce the load on the fiber assembly in the subsequent stage. From the viewpoint of easily achieving both improved filtration efficiency and longer filtration life, the ratio of the average pore diameter PB to the average pore diameter PC is preferably 0.10 or more and 0.90 or less, and more preferably 0.15 or more and 0.85 or less. When higher filtration efficiency is required, the ratio is preferably 0.45 to 0.95, more preferably 0.55 to 0.90, and even more preferably 0.65 to 0.85.When higher filtration life is required, the ratio is preferably 0.05 to 0.50, more preferably 0.10 to 0.45, and even more preferably 0.15 to 0.40.

[0053] The filtration layer C can include one or more selected from the group consisting of a filtration layer C1 in which a fiber aggregate C and a coarse nonwoven fabric are wound in a superimposed state, and a filtration layer C2 in which only the fiber aggregate C is wound.

[0054] The average pore diameter PC of the fiber assembly C is not particularly limited as long as the ratio of average pore diameter PB / average pore diameter PC satisfies the above-mentioned range. However, for example, from the viewpoint of capturing coarse particles, it is preferably 5.0 μm to 60 μm, more preferably 10 μm to 50 μm, and even more preferably 15 μm to 40 μm. When higher filtration efficiency is required, it is preferably 5.0 μm to 30.0 μm, more preferably 7.0 μm to 27.0 μm, and even more preferably 10.0 μm to 25.0 μm. When a longer filtration life is required, it is preferably 40 μm to 90 μm, more preferably 43 μm to 80 μm, and even more preferably 45 μm to 70 μm.

[0055] The minimum pore size of the fiber assembly C is not particularly limited as long as the ratio of average pore size PB to average pore size PC satisfies the above-mentioned range. For example, from the viewpoint of capturing relatively fine particles, the minimum pore size is preferably 3 μm to 30 μm, more preferably 4 μm to 20 μm, and even more preferably 5 μm to 10 μm. When higher filtration efficiency is required, the minimum pore size is preferably 2 μm to 9 μm, more preferably 3 μm to 8.5 μm, and even more preferably 4 μm to 8 μm. When higher filtration life is required, the minimum pore size is preferably 10 μm to 25 μm, more preferably 10.5 μm to 20 μm, and even more preferably 11.0 μm to 15 μm.

[0056] The maximum pore size of the fiber aggregate C is not particularly limited as long as the ratio of average pore size PB to average pore size PC satisfies the above-mentioned range. For example, from the viewpoint of preventing clogging by capturing inflowing coarse particles in the large pores, the maximum pore size is preferably 10 μm to 80 μm, more preferably 15 μm to 70 μm, and even more preferably 20 μm to 60 μm. When higher filtration efficiency is required, the maximum pore size is preferably 10 μm to 70 μm, more preferably 15 μm to 60 μm, and even more preferably 20 μm to 50 μm. When higher filtration life is required, the maximum pore size is preferably 120 μm to 310 μm, more preferably 130 μm to 280 μm, and even more preferably 140 μm to 250 μm.

[0057] The maximum pore size of the fiber assembly C is not particularly limited as long as the ratio of average pore size PB / average pore size PC satisfies the above-mentioned range. However, for example, from the viewpoint of reliably capturing coarse particles, it is preferably 5 μm to 30 μm, more preferably 7 μm to 25 μm, and even more preferably 10 μm to 20 μm. When higher filtration efficiency is required, it is preferably 5 μm to 21 μm, more preferably 7 μm to 20 μm, and even more preferably 10 μm to 19 μm. When higher filtration life is required, it is preferably 27 μm to 70 μm, more preferably 28 μm to 60 μm, and even more preferably 29 μm to 50 μm.

[0058] The average fiber diameter of the fiber aggregate C is smaller than that of the coarse nonwoven fabric, and is not particularly limited as long as the ratio of average pore diameter PB / average pore diameter PC satisfies the above-mentioned range. For example, it is preferably 2.0 μm to 15 μm, more preferably 2.5 μm to 10 μm, and even more preferably 3.0 μm to 7 μm. When the average fiber diameter of the fiber aggregate C satisfies this range, the average pore diameter easily satisfies the above-mentioned range, and both filtration efficiency and filtration life can be improved. When higher filtration efficiency is required, it is preferably 1.0 μm to 7.0 μm, more preferably 1.5 μm to 6.5 μm, and even more preferably 2.0 μm to 6.0 μm. When higher filtration life is required, it is preferably 9.0 μm to 30.0 μm, more preferably 9.5 μm to 25.0 μm, and even more preferably 10 μm to 20 μm.

[0059] The minimum fiber diameter of the fiber assembly C is not particularly limited as long as the ratio of the average pore diameter PB to the average pore diameter PC satisfies the above-mentioned range. For example, from the viewpoint of capturing fine foreign particles to a certain extent, the minimum fiber diameter is preferably 0.3 μm to 3 μm, more preferably 0.4 μm to 2.5 μm, and even more preferably 0.5 μm to 2 μm. When higher filtration efficiency is required, the minimum fiber diameter is preferably 0.3 μm to 3 μm, more preferably 0.4 μm to 2.5 μm, and even more preferably 0.5 μm to 2 μm. When a longer filtration life is required, the minimum fiber diameter is preferably 4.5 μm to 15.0 μm, more preferably 5.0 μm to 12.5 μm, and even more preferably 5.5 μm to 10.0 μm.

[0060] The maximum fiber diameter of the fiber aggregate C is not particularly limited as long as the average pore diameter PB / average pore diameter PC satisfies the above-mentioned range, but for example, from the viewpoint of ensuring the performance as a filter medium, it is preferably 2 μm or more and 20 μm or less, more preferably 4 μm or more and 18 μm or less, and even more preferably 6 μm or more and 16 μm or less. When higher filtration efficiency is required, it is preferably 2 μm or more and 15 μm or less, more preferably 4 μm or more and 14 μm or less, and even more preferably 6 μm or more and 13 μm or less. When higher filtration life is required, it is preferably 19 μm or more and 45 μm or less, more preferably 20 μm or more and 40 μm or less, and even more preferably 21 μm or more and 35 μm or less.

[0061] The air permeability of the fiber aggregate C is smaller than that of the coarse nonwoven fabric, and the average pore size PB / average pore size PC is required to satisfy the above-mentioned range. There are no particular limitations on this. For example, from the viewpoint of ensuring the performance as a filter medium, 3 / (cm 2 ·s) over 140cm 3 / (cm 2 s) or less, and 20 cm 3 / (cm 2 ·s) over 120cm 3 / (cm 2 s) or less is more preferable, and 30 cm 3 / (cm 2 ·s) more than 100cm 3 / (cm 2 If higher filtration efficiency is required, it is more preferable that the filtration efficiency is 10 cm 3 / (cm 2 ·s) over 110cm 3 / (cm 2 s) or less, and 20 cm 3 / (cm 2 ·s) more than 100cm 3 / (cm 2 s) or less is more preferable, and 30 cm 3 / (cm 2 ·s) over 90cm 3 / (cm 2s) or less. If a longer filtration life is required, 3 / (cm 2 ·s) or more than 340cm 3 / (cm 2 s) or less, and 180 cm 3 / (cm 2 ·s) or more than 310cm 3 / (cm 2 s) or less, and 200 cm 3 / (cm 2 ·s) over 280cm 3 / (cm 2 It is more preferable that the value is equal to or less than s.

[0062] The basis weight of each of the fiber aggregates A, B, and C is not particularly limited as long as the ratio of average pore size PA / average pore size PB or the ratio of average pore size PB / average pore size PC satisfies the above-mentioned range. For example, from the viewpoint of improving filtration performance, it is preferable that the basis weight is 10 g / m 2 More than 100g / m 2 Preferably, it is 15 g / m or less. 2 More than 80g / m 2 More preferably, it is 20 g / m or less. 2 More than 70g / m 2 It is even more preferable that:

[0063] The thickness of each of the fiber aggregates A, B, and C is not particularly limited as long as the ratio of average pore diameter PA / average pore diameter PB or the ratio of average pore diameter PB / average pore diameter PC satisfies the above-mentioned range. However, from the viewpoint of productivity, the thickness is preferably 0.05 mm or more and 1.5 mm or less, more preferably 0.10 mm or more and 1.25 mm or less, and even more preferably 0.15 mm or more and 1.0 mm or less.

[0064] The density of each of the fiber aggregates A, B, and C is not particularly limited as long as the ratio of average pore size PA / average pore size PB or the ratio of average pore size PB / average pore size PC satisfies the above-mentioned range. However, from the viewpoint of production stability, it is preferable that the density is 0.01 g / cm. 3 More than 0.8g / cm3 Preferably, it is 0.015 g / cm or less. 3 More than 0.45g / cm 3 More preferably, it is 0.02 g / cm or less. 3 More than 0.3g / cm 3 It is even more preferable that:

[0065] The tensile strength in the machine direction (MD) of each of fiber aggregates A, B, and C is not particularly limited, but from the viewpoint of production stability, for example, it is preferably 5 N / 5 cm or more and 60 N / 5 cm or less, more preferably 7 N / 5 cm or more and 50 N / 5 cm or less, and even more preferably 10 N / 5 cm or more and 40 N / 5 cm or less.

[0066] The elongation percentage in the machine direction (MD) of each of fiber aggregates A, B, and C is not particularly limited as long as the breathability satisfies the above-mentioned range. However, from the viewpoint of production stability, for example, it is preferably 5% or more and 80% or less, more preferably 10% or more and 65% or less, and even more preferably 15% or more and 50% or less.

[0067] The tensile strength in the cross direction (CD) of each of fiber aggregates A, B, and C is not particularly limited, but from the viewpoint of production stability, for example, it is preferably 5 N / 5 cm or more and 50 N / 5 cm or less, more preferably 7 N / 5 cm or more and 40 N / 5 cm or less, and even more preferably 10 N / 5 cm or more and 30 N / 5 cm or less.

[0068] The cross direction (CD) elongation of each of fiber aggregates A, B, and C is not particularly limited, but from the viewpoint of production stability, it is preferably 10% or more and 150% or less, more preferably 15% or more and 140% or less, and even more preferably 20% or more and 130% or less.

[0069] The types of fiber aggregates A, B, and C are not particularly limited as long as they are composed of fibers and satisfy the above-mentioned average pore size requirements. Examples include nonwoven fabrics, woven fabrics, knitted fabrics, and composites thereof. The type of nonwoven fabric is not particularly limited and may be, for example, a long fiber (e.g., fibers longer than 110 mm or substantially continuous fibers) nonwoven fabric or a short fiber (e.g., fibers having a length of 3 mm or more and 110 mm or less) nonwoven fabric. Examples of long fiber nonwoven fabrics include spunbond nonwoven fabrics, meltblown nonwoven fabrics obtained by the meltblown method, and nonwoven fabrics obtained by electrospinning (electrospinning, electrostatic spinning). Examples of short fiber nonwoven fabrics include those obtained by preparing webs using short fibers by wet papermaking, carding using a carding machine, airlaid, or the like, and then integrating the webs. The carding method can produce webs such as parallel webs, semi-random webs, random webs, cross webs, and crisscross webs. The webs are integrated by one or more methods selected from adhesive bonding (chemical bonding), thermal bonding by softening or melting the fibers (thermal bonding), needle punching, and high-pressure water jet treatment (spunlace). Fiber aggregates A, B, and C are preferably meltblown nonwoven fabrics, since the smaller the fiber diameter and the smaller the pore size, the higher the capturing ability. Fiber aggregates A, B, and C may each be two or more types of meltblown nonwoven fabrics, as long as they satisfy the above-mentioned average pore size requirements.

[0070] At least one fiber aggregate selected from the fiber aggregates A, B, and C has a coarse-grained structure in the thickness direction, and the fiber aggregate having a coarse-grained structure in the thickness direction is preferably wound so that the dense side is located on the outflow side of the material to be filtered. Examples of fiber aggregates having a coarse-grained structure in the thickness direction include meltblown nonwoven fabrics, which are produced by discharging molten resin from a spinning nozzle, blowing it away with a high-speed airflow while fiberizing it, and depositing the fibers. For example, the side closer to the collecting screen becomes the dense side because fibers are sucked in from below the screen and deposited thereon.

[0071] In each of the fiber aggregates A, B, and C, the fibers may be natural fibers, synthetic fibers, or the like, without any particular limitation, but synthetic fibers made of a thermoplastic resin are preferred. As the thermoplastic resin, the same materials as those listed in the description of the coarse nonwoven fabric can be used as appropriate.

[0072] From the viewpoints of productivity of the fiber assembly and the cylindrical filter and high chemical resistance (such as acid resistance, base resistance, and resistance to various organic solvents) when the cylindrical filter is used, the fibers in each of fiber assembly A, fiber assembly B, and fiber assembly C are preferably composed of a polyolefin resin such as polypropylene resin, polymethylpentene resin, polybutene-1 resin, ethylene-vinyl alcohol copolymer resin, or ethylene-propylene copolymer resin, and more preferably contain at least polypropylene resin. Polypropylene resin has a relatively high melting point among polyolefin resins, so it can filter liquids at relatively high temperatures, has good chemical resistance, and is low-cost. It should be noted that the thermoplastic resin constituting the fibers in each of fiber assembly A, fiber assembly B, and fiber assembly C is not limited to polyolefin resin; thermoplastic resins other than polyolefin resin can be appropriately selected and used depending on the performance required of the cylindrical filter of the present invention. If the application requires heat resistance for the cylindrical filter, in each of fiber aggregates A, B, and C, the fibers are preferably made of one or more resins selected from the group consisting of polyester resins, polyamide resins, polycarbonates, and polyphenylene sulfide, and more preferably made of one or more resins selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, nylon 6, nylon 66, polycarbonate, and polyphenylene sulfide.

[0073] The fibers constituting each of fiber aggregates A, B, and C may be single fibers or composite fibers. Single fibers include fibers formed by splitting splittable composite fibers and fibers formed by leaching out the sea component from so-called islands-in-sea composite fibers to form ultrafine island component fibers. The composite fibers may be any of concentric sheath-core, eccentric sheath-core, side-by-side, and splittable composite fibers. Fiber aggregates A, B, and C are preferably composed of single fibers, and particularly preferably composed of single fibers made of polypropylene resin. The fibers constituting each of fiber aggregates A, B, and C are not limited to single fibers made of polypropylene resin; fibers made of thermoplastic resins other than polypropylene resin can be appropriately selected and used depending on the performance required of the cylindrical filter. For applications requiring heat resistance for the cylindrical filter, it is preferable that each of fiber aggregates A, B, and C be composed of a single fiber or a composite fiber containing a polyester resin, a polyamide resin, a polycarbonate, or a polyphenylene sulfide, and it is more preferable that each be composed of a single fiber of a thermoplastic resin selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, nylon 6, nylon 66, polycarbonate, and polyphenylene sulfide.

[0074] When the filtration layer includes filtration layer A and filtration layer B, from the viewpoint of easily increasing the filtration life, it is preferable that filtration layer B includes filtration layer B1 in which fibrous aggregate B and a coarse nonwoven fabric are wound in a superimposed state, and it is more preferable that filtration layer A also includes filtration layer A1 in which fibrous aggregate A and a coarse nonwoven fabric are wound in a superimposed state.

[0075] When the filtration layer includes filtration layer A, filtration layer B, and filtration layer C, from the viewpoint of easily increasing the filtration life, it is preferable that filtration layer B includes filtration layer B1 in which fibrous aggregate B and a coarse nonwoven fabric are wound in an overlapping state, and it is more preferable that filtration layer C includes filtration layer C1 in which fibrous aggregate C and a coarse nonwoven fabric are wound in an overlapping state, and filtration layer A may also include filtration layer A1 in which fibrous aggregate A and a coarse nonwoven fabric are wound in an overlapping state, but from the viewpoint of increasing filtration efficiency, filtration layer A may include filtration layer A2 in which only fibrous aggregate A is wound.

[0076] In the filtration layers constituting the cylindrical filter of the present invention, when the total mass of filtration layer A, filtration layer B, and filtration layer C is taken as 100% by mass, it is preferred that the content of filtration layer A is 10% by mass to 85% by mass, the content of filtration layer B is 10% by mass to 70% by mass, and the content of filtration layer C is 0% by mass to 55% by mass. It is more preferred that the content of filtration layer A is 10% by mass to 75% by mass, the content of filtration layer B is 15% by mass to 60% by mass, and the content of filtration layer C is 0% by mass to 45% by mass. When the content of filtration layer A closest to the outflow side is 85% by mass or less, the filtration life is likely to be extended, and when the content of filtration layer A is 10% by mass or more, the filtration efficiency is likely to be improved. When the content of filtration layer B, which mainly affects the filtration efficiency, is 70% by mass or less, the filtration life is likely to be extended, and when the content of filtration layer B is 10% by mass or more, the filtration efficiency is likely to be improved. If the content of filtration layer C located on the inlet side of filtration layer B is 55 mass% or less, the proportion of filtration layer C will not be too large and will be an appropriate proportion, which is also preferable because it improves and stabilizes the filtration efficiency.

[0077] (Core material) Generally, a cylindrical filter has a configuration in which a filtering nonwoven fabric is wound around a tubular core material having holes (also referred to as a hollow portion) through which the material to be filtered passes. In the present invention, the core material is not particularly limited as long as it does not substantially impede the passage of liquid flowing from its outer periphery to its inner periphery or from its outer periphery to its inner periphery. For example, perforated tubes made of thermoplastic resin, perforated tubes made of metal, perforated tubes made of ceramics, and cylindrical fiber molded bodies can be used. From the standpoints of chemical resistance and manufacturing costs, perforated tubes made of thermoplastic resin and cylindrical fiber molded bodies are preferred as core materials. Perforated tubes made of thermoplastic resin can be obtained by extrusion molding or injection molding of molten thermoplastic resin. The cylindrical fiber molded body can be produced by any method, including, for example, a fiber molded body obtained by heating a fiber web containing thermal adhesive fibers and winding it around a core rod, or a fiber molded body obtained by filling a cylindrical container with a fiber web containing thermal adhesive fibers and heating it. In the cylindrical fiber molding, the basis weight of the fiber web is preferably 5 g / m 2 More than 100g / m 2 Less than 10 g / m, more preferably 2 More than 80g / m 2 More preferably, 20 g / m or less 2 More than 60g / m 2 The cylindrical fiber molded body can be a fiber molded body obtained by directly winding fibers with a soft or molten surface around a cylindrical metal core rod and cooling them in a manufacturing method in which a molten thermoplastic resin is extruded into the air by a meltblowing method or the like to obtain a nonwoven fabric. The cylindrical fiber molded body can also be a fiber molded body obtained by directly winding a spunbond nonwoven fabric around a cylindrical core rod and cooling them. The size and shape of the core material can be determined appropriately depending on the size and type of the filtration device. When the core material is a perforated cylindrical body, the hole size can be, for example, a polygonal shape with sides of 1 to 10 mm or a circle with a diameter of 1 to 10 mm.

[0078] A fibrous molded body is preferably used as the core material. Core materials using resin molded bodies obtained by extrusion or injection molding of molten thermoplastic resins are almost ineffective at capturing solid matter. On the other hand, when using a fibrous molded body as the core material, the fibers must be firmly thermally bonded to each other to ensure high compressive strength so that the core material does not deform or break due to the pressure applied during filtration. A fibrous molded body with firmly thermally bonded fibers has a high density and narrow interfiber spacing, allowing it to capture solid matter to a certain extent. Furthermore, as a filter, it has excellent diffusion effects for filtered materials, and its thickness allows it to function as a deep filtration mechanism. Due to these actions and effects, cylindrical filters with a fibrous molded body core material are thought to have higher and more stable filtration efficiency than cylindrical filters with a resin molded body core material.

[0079] As the raw material of the thermal adhesive fiber contained in the core material, the same materials as those mentioned in the description of the coarse nonwoven fabric can be used appropriately.

[0080] The fiber molded body (fiber web) preferably contains 50% by mass or more of thermal adhesive fibers, more preferably 80% by mass or more, and even more preferably consists solely of thermal adhesive fibers. When the content of thermal adhesive fibers in the fiber molded body (core material) is 50% by mass or more, the pressure resistance strength of the cylindrical filter is increased and the possibility of fibers falling off during use is reduced. Furthermore, there are no particular limitations on the fibers other than the thermal adhesive fibers. For example, recycled fibers such as rayon, semi-synthetic fibers such as acetate, and synthetic fibers such as polyolefin fibers, polyester fibers, polyamide fibers, and acrylic fibers can be used. The average fiber diameter of the thermal adhesive fibers contained in the fiber molded body (core material) is not particularly limited, but is preferably 5 μm or more and 100 μm or less. When the average fiber diameter of the thermal adhesive fibers satisfies the above range, the resulting fiber molded body (core material) has sufficient strength and the ability to capture solid matter. The average fiber diameter of the thermal adhesive fiber is more preferably 10 μm or more and 32 μm or less, and even more preferably 15 μm or more and 28 μm or less.

[0081] (outer layer) The cylindrical filter preferably includes an outer layer disposed on the inlet side (also referred to as the outside) of the filtration layer where the material to be filtered enters. The outer layer is preferably used to prevent damage and / or shedding of the nonwoven fabric constituting the filtration layer, to facilitate the winding operation, and to impart a design to the surface of the cylindrical filter. When the filtration layer is composed of filtration layer A and filtration layer B, the outer layer is disposed on the outside of filtration layer B, and when the filtration layer is composed of filtration layer A, filtration layer B, and filtration layer C, the outer layer is disposed on the outside of filtration layer C.

[0082] The fiber assembly contained in the outer layer may be any of nonwoven fabric, knitted fabric, woven fabric, and composites thereof. However, from the viewpoint of strength, it is preferable to use a nonwoven fabric containing thermally adhesive fibers (hereinafter referred to as outer layer nonwoven fabric). As the thermally adhesive fibers, those described in the description of the core material can be used as appropriate. The outer layer nonwoven fabric preferably contains 50% by mass or more of thermally adhesive fibers, more preferably 80% by mass or more, and even more preferably consists of thermally adhesive fibers alone. Furthermore, there are no particular limitations on the fibers other than the thermally adhesive fibers, and examples that can be used include recycled fibers such as rayon, semi-synthetic fibers such as acetate, and synthetic fibers such as polyolefin fibers, polyester fibers, polyamide fibers, and acrylic fibers.

[0083] The outer diameter of the cylindrical filter may be appropriately determined depending on the application, etc., and is not particularly limited, but may be, for example, 40 mm to 72 mm, 60 mm to 69 mm, or 60 mm to 67 mm. The inner diameter of the cylindrical filter (outer diameter of the core material) may be 15 mm to 30 mm, 30 mm to 45 mm, or 45 mm to 60 mm. The thickness of the filtration layer (= [outer diameter of cylindrical filter - inner diameter of cylindrical filter] / 2) may be 2 mm to 10 mm, 10 mm to 15 mm, or 15 mm to 20 mm.

[0084] From the viewpoint of achieving both filtration efficiency and filter life, the tubular filter preferably has a filtration efficiency of 1.0 μm cutoff rate of 80% or more, more preferably 85% or more. Furthermore, from the viewpoint of achieving both filtration efficiency and filter life, the filtration efficiency of 0.7 μm cutoff rate is preferably 75% or more. Furthermore, when a longer filtration life is required, the tubular filter preferably has a filtration efficiency of 5.0 μm cutoff rate of 75% or more. Furthermore, when a higher filtration efficiency is required, the tubular filter preferably has a filtration efficiency of 0.7 μm cutoff rate of 90% or more.

[0085] From the viewpoint of achieving both a long filtration life and a high filtration efficiency, the tubular filter preferably has a filtration life of 700 liters or more, more preferably 750 liters or more, and even more preferably 800 liters or more. Furthermore, when a longer filtration life is required, the tubular filter preferably has a filtration life of 1000 liters or more. Furthermore, when a higher filtration efficiency is required, the tubular filter preferably has a filtration life of 190 liters or more.

[0086] FIG. 1 is a schematic, partially exploded, cross-sectional perspective view of a cylindrical filter according to one embodiment of the present invention. As shown in FIG. 1, the cylindrical filter (1) includes a core (2), a filtration layer (3) wound around the core (2), and an outer layer (4) wound around the inlet side (outside) of the filtration layer (3). The filtration layer (3) includes filtration layers A (310), B (320), and C (330), wound sequentially from the outlet side toward the inlet side of the material to be filtered. The filtration layer A (310) is composed of a filtration layer A1 in which a fiber aggregate A (311) and a coarse nonwoven fabric (312) are wound in a superimposed state. The filtration layer B (320) is composed of a filtration layer B1 in which a fiber aggregate B (321) and a coarse nonwoven fabric (322) are wound in a superimposed state. The filtration layer C (330) is composed of a filtration layer C1 in which a fiber assembly C (331) and a coarse nonwoven fabric (332) are wound together in an overlapping state. The coarse nonwoven fabrics (312), (322), and (332) may be independent nonwoven fabrics or may be the same continuous nonwoven fabric.

[0087] <Manufacturing method of cylindrical filters> The manufacturing method of the cylindrical filter includes a winding step A to form a filtration layer A by winding only fiber aggregate A around a core material for a predetermined length, or by winding the fiber aggregate A and a coarse nonwoven fabric together for a predetermined length so that the fiber aggregate A is located inside the coarse nonwoven fabric, and a winding step B to form a filtration layer B by winding only fiber aggregate B around filtration layer A for a predetermined length, or by winding the fiber aggregate B and a coarse nonwoven fabric together for a predetermined length so that the fiber aggregate B is located inside the filtration layer A for a predetermined length, in which at least one of the fiber aggregate A and the coarse nonwoven fabric is wound in an overlapping state. The core material, fiber aggregate A, fiber aggregate B, and coarse nonwoven fabric may be those described in the section regarding cylindrical filters. In this specification, "inside" refers to the outflow side of the material to be filtered, and "outside" refers to the inflow side of the material to be filtered.

[0088] In the winding step B, it is preferable to overlap the end of fiber aggregate B with the end of fiber aggregate A and then wind fiber aggregate B, and it is more preferable to overlap fiber aggregate A and fiber aggregate B so that the end of fiber aggregate A and the end of fiber aggregate B overlap by 3 cm to 15 cm, and then wind fiber aggregate B. This makes it possible to prevent the generation of longitudinal gaps between fiber aggregates A and B, and simultaneously improves the filtration efficiency and filter life.

[0089] The manufacturing method for the cylindrical filter may further include a winding step C in which the filtration layer C is formed by winding only the fiber aggregate C around the filtration layer B by a predetermined length, or by winding the fiber aggregate C and the coarse nonwoven fabric together by overlapping them by a predetermined length so that the fiber aggregate C is closer to the filtration layer B (inside) than the coarse nonwoven fabric.

[0090] In the winding step C, it is preferable to overlap the end of fiber aggregate C with the end of fiber aggregate B and then wind fiber aggregate C, and it is more preferable to overlap fiber aggregate B and fiber aggregate C so that the end of fiber aggregate B overlaps the end of fiber aggregate C by 3 cm to 15 cm, and then wind fiber aggregate C. This makes it possible to prevent the generation of longitudinal gaps between fiber aggregates A and B, and simultaneously improves the filtration efficiency and filter life.

[0091] In the winding step A, the length over which only the fiber aggregate A is wound, or the length over which the fiber aggregate A and the coarse nonwoven fabric are wound in a superimposed state, is preferably 0.5 m to 10 m, more preferably 1.0 m to 9 m, and even more preferably 1.5 m to 8 m. In the winding step B, the length over which only the fiber aggregate B is wound, or the length over which the fiber aggregate B and the coarse nonwoven fabric are wound in a superimposed state, is preferably 0.5 m to 10 m, more preferably 1.0 m to 9 m, and even more preferably 1.5 m to 8 m. In the winding step C, the length over which only the fiber aggregate C is wound, or the length over which the fiber aggregate C and the coarse nonwoven fabric are wound in a superimposed state, is preferably 0.5 m to 10 m, more preferably 1.0 m to 9 m, and even more preferably 1.5 m to 8 m. This makes it easy to obtain a filtration layer containing filtration layers A, B, and C in the amounts described in the section regarding the cylindrical filter.

[0092] The coarse nonwoven fabric used in the winding step A, the coarse nonwoven fabric used in the winding step B, and the coarse nonwoven fabric used in the winding step C may be independent nonwoven fabrics or may be the same continuous nonwoven fabric.

[0093] The method for producing a cylindrical filter may further include an outer layer forming step of winding a fiber assembly around the outside of the filtration layer to form an outer layer. In the outer layer forming step, the above-mentioned outer layer fiber assembly can be used as appropriate.

[0094] 2 is a schematic process diagram illustrating one example of a method for producing a cylindrical filter of the present invention. The method for producing a cylindrical filter includes a winding step A (100), a winding step B (200), a winding step C (300), and an outer layer forming step (400).

[0095] First, in the winding step A (100), the tip of the coarse nonwoven fabric (312) is brought into close contact with the core material (2), the core material (2) is pressed with a roll (e.g., a stainless steel roll), and the core material (2) is rotated in the direction of the arrow. The fiber aggregate A (311) is supplied in an overlapping state on top of the coarse nonwoven fabric (312) and wound around the core material (2) by a predetermined length, thereby forming the filtration layer A (310). The fiber aggregate A (311) is wound closer to the core material than the coarse nonwoven fabric (312). In the winding step A (100), the pressure (pressing pressure) applied to the roll pressing the core material (2) is preferably 0.01 MPa or more and 1.0 MPa or less, more preferably 0.03 MPa or more and 0.8 MPa or less, and even more preferably 0.05 MPa or more and 0.6 MPa or less. In Fig. 2, for the sake of convenience, the fiber aggregate A (311) and the coarse nonwoven fabric (312) are shown separated from each other, but in reality, the fiber aggregate A (311) and the coarse nonwoven fabric (312) are in contact with each other.

[0096] Next, in the winding step B (200), an end of the fiber aggregate B (321) is overlapped with an end of the fiber aggregate A (311), and then the coarse nonwoven fabric (322) is supplied in an overlapping state on the outside of the fiber aggregate B (321), and a predetermined length of the fiber aggregate B (321) and the coarse nonwoven fabric (322) are wound around the filtration layer A (310) to form the filtration layer B (320). In the winding step B (200), the pressure applied to the roll pressing the core material (2) is preferably 0.01 MPa to 1.0 MPa, more preferably 0.03 MPa to 0.8 MPa, and even more preferably 0.05 MPa to 0.6 MPa.

[0097] Next, in the winding step C (300), the end of the fiber aggregate C (331) is overlapped with the end of the fiber aggregate B (321), and then the coarse nonwoven fabric (332) is supplied in an overlapping state on the outside of the fiber aggregate C (331), and a predetermined length of the fiber aggregate C (331) and the coarse nonwoven fabric (332) are wound around the filtration layer B (320) to form the filtration layer C (330). In the winding step C (300), the pressure applied to the roll pressing the core material (2) is preferably 0.01 MPa to 1.0 MPa, more preferably 0.03 MPa to 0.8 MPa, and even more preferably 0.05 MPa to 0.6 MPa.

[0098] Next, in the outer layer forming step (400), an end of the outer layer fiber assembly (41) is overlapped with an end of the fiber assembly C (331), and then a predetermined length is wound around the filtration layer C (330) to form the outer layer (4), thereby obtaining the cylindrical filter 1. The filtration layer 3 is composed of a filtration layer A (310), a filtration layer B (320), and a filtration layer C (330).

[0099] The coarse nonwoven fabric (312), the coarse nonwoven fabric (322), and the coarse nonwoven fabric (332) may be independent nonwoven fabrics, or may be the same continuous nonwoven fabric.

[0100] 3 is a schematic process diagram illustrating a method for manufacturing a cylindrical filter according to one example of the present invention. The method for manufacturing the cylindrical filter includes a winding step A (100), a winding step B (200), a winding step C (300), and an outer layer forming step (400). The method for manufacturing the cylindrical filter includes the same winding steps B (200), C (300), and outer layer forming step (400) as the method for manufacturing the cylindrical filter shown in FIG. 2, except that in the winding step A (100), the tip of the fiber aggregate A (311) is brought into close contact with the core material (2), the fiber aggregate A (311) is pressed with a roll, and a predetermined length of the fiber aggregate A (311) is wound around the core material (2) while rotating the core material (2) in the direction of the arrow, thereby forming a filtration layer A (310).

[0101] Cylindrical filters are suitable for various applications involving the removal of solid matter from liquids, and can be used to filter liquids such as pure water, drinking water, chemical solutions, various oils and fats, plating solutions, paint solutions, and cleaning water for the electronics industry. [Example]

[0102] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0103] The measurement methods used in the examples and comparative examples will be explained below.

[0104] (Thickness, basis weight, and strength and elongation) Measurement was performed based on JIS L 1913.

[0105] (density) The density of the fiber aggregate and the coarse nonwoven fabric was calculated based on the thickness and basis weight measured as described above. Density = basis weight / thickness

[0106] (Air permeability of coarse nonwoven fabric) Cut the coarse nonwoven fabric into 20cm squares and use a basis weight of 375-400g / m 2 A plurality of sheets were stacked so as to form a sample, and the air permeability was measured in accordance with the Frazier method of JIS L 1913.

[0107] (Air permeability of fiber assembly) The air permeability was measured according to the Frazier method of JIS L 1913.

[0108] (pore diameter) The pore size of the fiber assembly was measured in accordance with JIS K 3832 using a capillary flow porometer "CFP-1200-AEXC-P" manufactured by Porous Material Inc.

[0109] (fiber diameter) A 50x magnified photograph of the fiber assembly was taken using a scanning electron microscope (Hitachi High-Technologies Ametech Japan, model number "SU3500"), and diagonal lines were drawn on the photograph. 50 intersections with the fibers were measured to determine the maximum fiber diameter, minimum fiber diameter, and average fiber diameter (arithmetic mean diameter).

[0110] (Compression characteristics) The coarse nonwoven fabric was cut into 10 cm squares, and several pieces were stacked to weigh 15 g to prepare a sample. The sample was compressed under the following conditions using a tension and compression tester (MinebeaMitsumi, model number "TGI-10kN"), and the load required to reach a predetermined displacement was measured. The rate of change in thickness at the predetermined load was calculated as the compression ratio. Zero point: 0.5N load point Head speed: 10mm / min Test end point: Measured up to a load of 3000N Compression rate (%) = 100 × {(thickness at a given load) / (thickness at zero point)}

[0111] (bending resistance) Measurement was performed according to JIS L 1913, 6.7.1 a) 41.5° cantilever method.

[0112] (Tensile strength and elongation) Measurement was carried out in accordance with JIS L 1913.

[0113] (Filter life) A test suspension with a concentration of 30 ppm was prepared by dispersing test powder conforming to JIS Z 8901 (JIS Type 8 test powder and JIS Type 11 test powder were prepared and mixed at a mass ratio of 1:1) in water. Next, 200 L of the test suspension was circulated from the outer periphery (the inlet side) of the cylindrical filter to the inner hollow portion (the outlet side) at a flow rate of 15 L / min, and 15 ppm of test powder was added to the test suspension every 13.5 minutes. The total amount of water (liters) passed until the water pressure required to maintain a flow rate of 15 L / min reached 0.2 MPa was defined as the filtration life of the cylindrical filter.

[0114] (filtration efficiency) An aqueous dispersion of test dust conforming to JIS Z 8901 (a 1:1 mixture of JIS Class 11 [median diameter 2 μm] and JIS Class 8 [median diameter 6.6 to 8.6 μm] by mass) adjusted to a concentration of 30 ppm was used as the test suspension. The test suspension was filtered at a flow rate of 15 liters / minute from the outer periphery of the cartridge filter toward the hollow interior while being stirred to ensure a uniform concentration. The number of particles by particle size M contained in the test suspension before filtration and the number of particles by particle size N contained in the test suspension that had passed through the cylindrical filter one minute after filtration began were measured by dividing the range from 0.7 μm to 7.1 μm into 64 parts and dividing the range into 64 parts. The filtration efficiency was expressed as the blocking rate (%), which indicates the degree to which particles of sizes 0.7 μm or more, 1.0 μm or more, 3.0 μm or more, 5.0 μm or more, and 7.1 μm or more were reduced before and after water was passed through, and the 80% particle size, which was calculated by linear conversion from the particle size when the cumulative blocking rate reached 80%. Blocking rate (%) = [(MN) / M] × 100

[0115] <Air-through nonwoven fabric> (Production Example 1) A thermal adhesive core-sheath composite fiber with a fineness of 28 dtex and a fiber length of 102 mm, in which the core component is polypropylene resin (melting point 166°C) and the sheath component is high-density polyethylene resin (melting point 132°C), is used at 100% by mass. This is passed through a parallel card to produce a card web (basis weight approximately 41 g / m 2 ) was obtained. The obtained carded web was placed on a water-permeable support, and a high-pressure water stream was sprayed onto the upper surface of the carded web once at a water pressure of 1.96 MPa and once at a water pressure of 2.94 MPa. Next, the carded web was dried by heating with hot air at 120°C, and then heated with hot air at 140°C to melt the sheath component of the composite fiber, thereby producing air-through nonwoven fabric 1.

[0116] (Production Example 2) An air-through nonwoven fabric 2 was produced in the same manner as in Production Example 1, except that 100% by mass of thermally adhesive core-sheath composite fibers with a fineness of 2.2 dtex and a fiber length of 51 mm, in which the core component was made of polypropylene resin (melting point 166°C) and the sheath component was made of high-density polyethylene resin (melting point 132°C), were used.

[0117] (Production Example 3) An air-through nonwoven fabric 3 was produced in the same manner as in Example 1, except that 100% by mass of thermal adhesive core-sheath composite fibers with a fineness of 67 dtex and a fiber length of 51 mm, in which the core component was made of polypropylene resin (melting point 166°C) and the sheath component was made of high-density polyethylene resin (melting point 132°C), were used.

[0118] <Meltblown nonwoven fabric> Meltblown nonwoven fabric 1: Meltblown nonwoven fabric made of a single fiber of polypropylene resin Meltblown nonwoven fabric 2: Meltblown nonwoven fabric made of a single fiber of polypropylene resin Meltblown nonwoven fabric 3: Meltblown nonwoven fabric made of a single fiber of polypropylene resin Meltblown nonwoven fabric 4: Meltblown nonwoven fabric made of a single fiber of polypropylene resin Meltblown nonwoven fabric 5: Meltblown nonwoven fabric made of a single fiber of polypropylene resin Meltblown nonwoven fabric 6: Meltblown nonwoven fabric made of a single fiber of polypropylene resin

[0119] The basis weight, thickness, density, breathability, compression characteristics, and stiffness of the through-air nonwoven fabrics 1 to 3, as well as the average fiber diameter of the fibers constituting each of the through-air nonwoven fabrics, were measured as described above, and the results are shown in Table 1 below. In Table 1 below, the load required for compression to 30% refers to the load when the compression rate is 30%. The basis weight, thickness, density, pore size, and breathability of the meltblown nonwoven fabrics 1 to 5, as well as the average fiber diameter of the fibers constituting each of the meltblown nonwoven fabrics, were measured as described above, and the results are shown in Table 2 below.

[0120] [Table 1]

[0121] [Table 2]

[0122] Example 1 (1) Preparation of the core material A thermal adhesive core-sheath composite fiber with a fineness of 2.2 dtex and a fiber length of 51 mm, consisting of a core component of polypropylene resin (melting point 166°C) and a sheath component of high-density polyethylene resin (melting point 132°C), was used at 100% by mass. This was passed through a parallel card to produce a card web (basis weight 46 g / m 2 ) was obtained. The obtained card web was placed on a water-permeable support, and a high-pressure water stream was sprayed onto the upper surface of the card web once at a water pressure of 1.96 MPa and once at a water pressure of 2.94 MPa. Next, it was dried by heating with hot air at 120°C, and then heated with hot air at 140°C to melt the sheath component of the composite fiber. While this was happening, the composite fiber was continuously wound around an iron core with a length of 1.5 m and a diameter of 30 mm until the winding diameter reached 41 mm, after which it was cooled and the iron core was removed to obtain a core material (thickness 5.5 mm). (2) Preparation of the filtration layer Next, the tip of the air-through nonwoven fabric 1 was attached to the core material, and then a stainless steel roll was used to press the core material from above at a pressure (press pressure) of 0.1 MPa. While rotating the core material, immediately after starting to wind the air-through nonwoven fabric 1, the meltblown nonwoven fabric 1 was supplied from the upper side of the air-through nonwoven fabric 1 (opposite the core material) in an overlapping state, and 2 m of the fabric was wound together to form a filtration layer A1 (filtration layer A). Then, the meltblown nonwoven fabric 2 was wound together with the air-through nonwoven fabric 1 for 2 m to form a filtration layer B1. Next, the meltblown nonwoven fabric 3 was wound together with the air-through nonwoven fabric 1 for 2 m to form a filtration layer C1 (filtration layer C). The ends of the fiber aggregate A and the fiber aggregate B overlapped by 5 cm, and the ends of the fiber aggregate B and the fiber aggregate C overlapped by 5 cm. (3) Preparation of the outer layer The air-through nonwoven fabric 2 was wrapped around the filtration layer to a length of 2 m to form the outer layer. While the cylindrical body was being rotated, a heater (surface temperature 140°C) consisting of a metal rod with 1 mm-wide metal flanges attached at 10 mm intervals was pressed against the outer surface of the outermost air-through nonwoven fabric 2. This melted the sheath component, a low-melting-point component of the thermal adhesive fiber that made up the air-through nonwoven fabric 2 abutting against the metal flanges, thereby bonding and forming the fabric so that it would not peel off. The outer diameter of the resulting cylindrical filter was 69.0 mm. (4) Cutting The obtained cylindrical formed body was cut to a length of 250 mm, taking care that the nonwoven fabric used was inserted evenly in the width direction, to prepare a cylindrical filter.

[0123] Example 2 A cylindrical filter was produced in the same manner as in Example 1, except that the pressing pressure of the rolls pressing the core material when winding the nonwoven fabrics constituting the filtration layer and the outer layer was set to 0.2 MPa. The outer diameter of the obtained cylindrical filter was 71.5 mm.

[0124] Example 3 A cylindrical filter was produced in the same manner as in Example 1, except that the meltblown nonwoven fabric 1 alone was wound around a core material by 2 m to form a filtration layer A2, and then the filtration layer A1, the filtration layer B1, and the filtration layer C1 were formed. The outer diameter of the obtained cylindrical filter was 67.6 mm.

[0125] Example 4 A cylindrical filter was produced in the same manner as in Example 1, except that the meltblown nonwoven fabric 1 was wound 1.5 m around the core material together with the air-through nonwoven fabric 1 to form the filtration layer A1. The outer diameter of the obtained cylindrical filter was 70.0 mm.

[0126] Example 5 A cylindrical filter was produced in the same manner as in Example 1, except that the lengths of the melt-blown nonwoven fabric 2 and the air-through nonwoven fabric 1 constituting the filtration layer B1 were 1.5 mm and the lengths of the melt-blown nonwoven fabric 3 and the air-through nonwoven fabric 1 constituting the filtration layer C1 were 1.5 m. The outer diameter of the obtained cylindrical filter was 67.7 mm.

[0127] Example 6 A cylindrical filter was produced in the same manner as in Example 1, except that the filtration layer A2 was formed by winding only the meltblown nonwoven fabric A around the core material by 2 m without forming the filtration layer A1. The outer diameter of the obtained cylindrical filter was 67.1 mm.

[0128] Example 7 A cylindrical filter was produced in the same manner as in Example 1, except that the filtration layer C2 was formed by winding only the meltblown nonwoven fabric 3 to a length of 2 m without forming the filtration layer C1. The outer diameter of the obtained cylindrical filter was 65.8 mm.

[0129] Example 8 A cylindrical filter was produced in the same manner as in Example 1, except that the air-through nonwoven fabric 3 was used instead of the air-through nonwoven fabric 1. The outer diameter of the obtained cylindrical filter was 70.9 mm.

[0130] Example 9 When winding the nonwoven fabrics constituting the filtration layer and the outer layer, the press pressure of the roll pressing the core material was 0.4 MPa, filtration layer C1 was not formed, the length of the meltblown nonwoven fabric 1 constituting the filtration layer A2 was 2.5 m, the length of the meltblown nonwoven fabric 1 and the air-through nonwoven fabric 1 constituting the filtration layer A1 was 2.5 m, and the length of the meltblown nonwoven fabric 2 and the air-through nonwoven fabric 1 constituting the filtration layer B1 was 3 m. A cylindrical filter was produced in the same manner as in Example 3. The outer diameter of the obtained cylindrical filter was 67.2 mm.

[0131] Example 10 A cylindrical filter was produced in the same manner as in Example 9, except that the length of the meltblown nonwoven fabric 1 constituting the filtration layer A2 was 3 m, the length of the meltblown nonwoven fabric 1 and the air-through nonwoven fabric 1 constituting the filtration layer A1 was 3 m, and the length of the meltblown nonwoven fabric 2 and the air-through nonwoven fabric 1 constituting the filtration layer B1 was 2 m. The outer diameter of the obtained cylindrical filter was 66.0 mm.

[0132] Example 11 When winding the nonwoven fabrics constituting the filtration layer and the outer layer, the press pressure of the roll pressing the core material was 0.2 MPa, the length of the meltblown nonwoven fabric 1 constituting the filtration layer A2 was 1 m, the length of the meltblown nonwoven fabric 1 and the air-through nonwoven fabric 1 constituting the filtration layer A1 was 1.5 m, the length of the meltblown nonwoven fabric 2 and the air-through nonwoven fabric 1 constituting the filtration layer B1 was 1.5 m, and the length of the meltblown nonwoven fabric 3 and the air-through nonwoven fabric 1 constituting the filtration layer C1 was 1.5 m. A cylindrical filter was produced in the same manner as in Example 3. The outer diameter of the obtained cylindrical filter was 65.4 mm.

[0133] Example 12 A cylindrical filter was produced in the same manner as in Example 1, except that the length of the meltblown nonwoven fabric 1 and the air-through nonwoven fabric 1 constituting the filtration layer A1 was 1 m. The outer diameter of the obtained cylindrical filter was 65.8 mm.

[0134] Example 13 A cylindrical filter was produced in the same manner as in Example 1, except that the filtration layer C1 was not formed, the meltblown nonwoven fabric 2 was used in place of the meltblown nonwoven fabric 1 in the filtration layer A1, and the meltblown nonwoven fabric 3 was used in place of the meltblown nonwoven fabric 2 in the filtration layer B1. The outer diameter of the obtained cylindrical filter was 65.6 mm.

[0135] Example 14 In the filtration layer A1, meltblown nonwoven fabric 2 was used instead of meltblown nonwoven fabric 1, and the length of the meltblown nonwoven fabric 2 and the air-through nonwoven fabric 1 constituting the filtration layer A1 was 1 m, in the filtration layer B1, meltblown nonwoven fabric 3 was used instead of meltblown nonwoven fabric 2, and the length of the meltblown nonwoven fabric 3 and the air-through nonwoven fabric 1 constituting the filtration layer B1 was 3 m, and in the filtration layer C1, meltblown nonwoven fabric 6 was used instead of meltblown nonwoven fabric 3. A cylindrical filter was produced in the same manner as in Example 2. The outer diameter of the obtained cylindrical filter was 69.8 mm.

[0136] Example 15 A cylindrical filter was produced in the same manner as in Example 2, except that the filtration layer C1 was not formed, the meltblown nonwoven fabric 3 was used in place of the meltblown nonwoven fabric 1 in the filtration layer A1, and the meltblown nonwoven fabric 6 was used in place of the meltblown nonwoven fabric 2 in the filtration layer B1. The outer diameter of the obtained cylindrical filter was 65.9 mm.

[0137] (Comparative Example 1) A cylindrical filter was produced in the same manner as in Example 1, except that filtration layer A2 was formed using only 2 m of meltblown nonwoven fabric 1, filtration layer B2 was formed using only 1 m of meltblown nonwoven fabric 2, and filtration layer C2 was formed using only 1 m of meltblown nonwoven fabric 3. The outer diameter of the obtained cylindrical filter was 61.9 mm.

[0138] (Comparative Example 2) A cylindrical filter was produced in the same manner as in Example 1, except that air-through nonwoven fabric 2 was used instead of air-through nonwoven fabric 1, filtration layer A1 was formed from 2 m of overlapping melt-blown nonwoven fabric 1 and air-through nonwoven fabric 2, filtration layer B1 was formed from 1 m of overlapping melt-blown nonwoven fabric 2 and air-through nonwoven fabric 2, and filtration layer C1 was formed from 1 m of overlapping melt-blown nonwoven fabric 3 and air-through nonwoven fabric 2. The outer diameter of the obtained cylindrical filter was 63.9 mm.

[0139] (Comparative Example 3) A cylindrical filter was produced in the same manner as in Example 1, except that filtration layer A2 was formed using only 2 m of meltblown nonwoven fabric 1, filtration layer B2 was formed using only 2 m of meltblown nonwoven fabric 2, and filtration layer C2 was formed using only 2 m of meltblown nonwoven fabric 3. The outer diameter of the obtained cylindrical filter was 61.3 mm.

[0140] Comparative Example 4 A cylindrical filter was produced in the same manner as in Example 1, except that the core material had a winding diameter of 57 mm (thickness 14 mm), and 1.0 m of overlapping meltblown nonwoven fabric 5 and air-through nonwoven fabric 2 was used to press the core material with a stainless steel roll at a pressure set to 0.2 MPa to form filtration layer A1, and filtration layers B1 and C were not formed. The outer diameter of the obtained cylindrical filter was 66.6 mm.

[0141] (Comparative Example 5) A cylindrical filter was produced in the same manner as in Example 1, except that filtration layer A2 was formed using only 0.75 m of meltblown nonwoven fabric 4, filtration layer B2 was formed using only 2 m of meltblown nonwoven fabric 2, and filtration layer C2 was formed using only 5 m of meltblown nonwoven fabric 5. The outer diameter of the obtained cylindrical filter was 64.1 mm.

[0142] The types and lengths (winding lengths) of the fiber assemblies constituting the filtration layers are shown in Table 3. Table 3 also shows the contents of filtration layers A, B, and C when the total mass of filtration layers A, B, and C is 100% by mass.

[0143] [Table 3]

[0144] In the examples and comparative examples, the filtration performance of the cylindrical filters was measured as described above. The results are shown in Table 4 below. Table 4 below also shows the types of meltblown nonwoven fabrics and coarse nonwoven fabrics corresponding to fiber aggregates A, B, and C used in the examples and comparative examples, as well as the PA / PB and PB / PC values. [Table 4]

[0145] As can be seen from Tables 1 to 4 above, the cylindrical filters of Examples 1 to 8, 11, and 12 had a 1.0 μm shielding rate of 80% or more for particles with a particle diameter of 1.0 μm or more, a 0.7 μm shielding rate of 75% or more for particles with a particle diameter of 0.7 μm or more, an 80% particle diameter of 0.85 μm or less, and a filtration life of 700 liters or more, and were both good in terms of filtration efficiency and filtration life. Furthermore, the cylindrical filters of Examples 9 and 10 had a 1.0 μm shielding rate for particles with a particle diameter of 1.0 μm or more and a 0.7 μm shielding rate for particles with a particle diameter of 0.7 μm or more of 95% or more, demonstrating extremely good filtration efficiency. Furthermore, the cylindrical filters of Examples 13 and 14 had a 3.0 μm shielding rate of 95% or more for particles with a particle size of 3.0 μm or more, had good filtration efficiency for impurities with large particle sizes, and had an excellent filtration life of over 1,300 L. Furthermore, the cylindrical filter of Example 15 had a 5.0 μm blocking rate of 80% or more for particles with a particle diameter of 5.0 μm or more, and had basic filtration efficiency. Its filtration life exceeded 2500 L, which was extremely good.

[0146] In comparison with Example 1, Example 3, in which the filtration layer A included not only a filtration layer A1 in which the fiber aggregate A and the coarse nonwoven fabric were wound, but also a filtration layer A2 in which only the fiber aggregate A was wound and which was located on the outflow side of the filtration layer A1, had a higher filtration efficiency than Example 1. In Example 4, in which the winding length of the fiber assembly A and the coarse nonwoven fabric used in the filtration layer A1 was reduced to about 75% compared to Example 1, the filtration efficiency was almost the same as that of Example 1. In Example 5, in which the winding length of the fiber aggregate B and the coarse nonwoven fabric used in the filtration layer B1 was reduced to about 75% compared to Example 1, and the winding length of the fiber aggregate C and the coarse nonwoven fabric used in the filtration layer C1 was reduced to about 75%, the filter life was almost the same as in Example 1. In contrast to Example 1, Example 6, in which the filtration layer A did not include a filtration layer A1 in which the fiber aggregate A and the coarse nonwoven fabric were wound, but included a filtration layer A2 in which only the fiber aggregate A was wound, had a filtration life that was almost the same as that of Example 1. In contrast to Example 1, Example 7, in which the filtration layer C did not include a filtration layer C1 in which the fiber aggregate C and the coarse nonwoven fabric were wound, but included a filtration layer C2 in which only the fiber aggregate C was wound, had a filtration life that was almost the same as that of Example 1. In Example 8, which used a coarse nonwoven fabric with higher breathability than Example 1, the filtration efficiency and filter life were almost the same as those of Example 1. In comparison with Example 1, Example 9 did not include filtration layer C, but added filtration layer A2, and had a longer winding length for the fiber aggregate A and coarse nonwoven fabric that constitute filtration layer A1 and the fiber aggregate B and coarse nonwoven fabric that constitute filtration layer B1. In this example, the 0.7 μm blocking rate for particles with a particle diameter of 0.7 μm or more was high, and the filtration efficiency was improved. In comparison with Example 1, Example 10 did not include filtration layer C, but added filtration layer A2, and had a longer winding length of the fiber aggregate A and coarse nonwoven fabric that constituted filtration layer A1. In this example, the 0.7 μm blocking rate for particles with a particle diameter of 0.7 μm or more was high, and the filtration efficiency was improved. In Example 11, in which a filtration layer A2 was added and the winding lengths of the fiber aggregate A and the coarse nonwoven fabric that constitute filtration layer A1, the winding lengths of the fiber aggregate B and the coarse nonwoven fabric that constitute filtration layer B1, and the winding lengths of the fiber aggregate B and the coarse nonwoven fabric that constitute filtration layer C1 were shortened, the 0.7 μm blocking rate for particles with a particle diameter of 0.7 μm or more was high, the filtration efficiency was improved, and the filtration life was also improved. In Example 12, in which the winding length of the fiber assembly A and the coarse nonwoven fabric constituting the filtration layer A1 was shortened compared to Example 1, the filtration efficiency was comparable and the filtration life was improved. Compared to Example 1, Examples 13 and 15 did not include filtration layer C and had larger average pore sizes of the fiber aggregate A constituting filtration layer A1 and the fiber aggregate B constituting filtration layer B1, and therefore had significantly improved filtration life. Compared to Example 1, Example 14, in which the average pore size of the fiber aggregate A constituting the filtration layer A1, the average pore size of the fiber aggregate B constituting the filtration layer B1, and the average pore size of the fiber aggregate C constituting the filtration layer C1 were increased, had an improved filtration life.

[0147] On the other hand, Comparative Examples 1, 3, and 5, which included filtration layers A2, B2, and C2 formed by winding only fiber aggregates A, B, and C without using a coarse nonwoven fabric, showed significantly reduced filtration life. Breathability is 100cm 3 / (cm 2 In Comparative Example 2, in which a coarse nonwoven fabric having an air permeability of less than 100 cm s was used, the filtration life was significantly reduced. 3 / (cm 2 It is presumed that this is because the coarse nonwoven fabric with a thickness of less than 1 / 4 s is easily crushed by the water pressure during filtration and is no longer able to maintain voids. In Comparative Example 4, in which the filtration layers A, B, and C were made of the same fiber assembly without providing a pore size gradient, the filtration life was extremely reduced.

[0148] The present invention is not particularly limited, but includes, for example, the following embodiments.

[0149] [1] A cylindrical filter including a core material and a filtration layer wound around the core material, wherein the filtration layer includes a filtration layer A and a filtration layer B wound continuously in order from the outflow side of the object to be filtered, The filtration layer A includes a fiber assembly A, and the filtration layer B includes a fiber assembly B, the average pore size PA of the fiber assembly A and the average pore size PB of the fiber assembly B are different, and the average pore size PA / average pore size PB is 0.05 or more and 0.95 or less; At least one of the fiber aggregate A and the fiber aggregate B is wound in a state where it is overlapped with a coarse nonwoven fabric, The coarse nonwoven fabric has an average fiber diameter larger than that of both the fiber aggregate A and the fiber aggregate B, and satisfies at least one of the following (i), (ii), and (iii): (i) Air permeability is 150 cm 3 / (cm 2 ·s) more than 500cm 3 / (cm 2 ·s) or less (ii) The load (N) required to compress it to 30% is 50N or more and 1500N or less. (iii) Compression rate under a 100N load is 25% or more and 70% or less [2] The cylindrical filter according to [1], wherein the average fiber diameter of the coarse nonwoven fabric is 40 μm or more and 120 μm or less. [3] The cylindrical filter according to [1] or [2], wherein the fibers constituting the coarse nonwoven fabric form fiber intersections where the fibers come into contact with each other, and the fibers are bonded to each other at at least some of the fiber intersections. [4] The cylindrical filter according to [3], wherein the coarse nonwoven fabric is at least one selected from the group consisting of an air-through nonwoven fabric and a chemically bonded nonwoven fabric. [5] The cylindrical filter according to any one of [1] to [4], wherein the fiber aggregate A and the fiber aggregate B are both meltblown nonwoven fabrics. [6] The filtration layer includes a filtration layer A, a filtration layer B, and a filtration layer C wound continuously in order from the outflow side of the object to be filtered, The filtration layer C includes a fiber aggregate C having an average fiber diameter smaller than that of the coarse nonwoven fabric, The cylindrical filter according to any one of [1] to [5], wherein the average pore diameter PC of the fiber assembly C is different from the average pore diameter PA of the fiber assembly A and the average pore diameter PB of the fiber assembly B, and the average pore diameter PB / average pore diameter PC is 0.05 or more and 0.95 or less. [7] The cylindrical filter according to [6], wherein each of the fiber aggregates B and C is wound in a state where it is overlapped with the coarse nonwoven fabric. [8] The cylindrical filter according to [6] or [7], wherein the fiber aggregate A, the fiber aggregate B, and the fiber aggregate C are all wound in a state where they are overlapped with the coarse nonwoven fabric. [9] Further, an outer layer is arranged on the inlet side of the filtration layer to be filtered, The cylindrical filter according to any one of [1] to [8], wherein the average fiber diameter or average pore diameter of the fiber aggregate constituting the outer layer is larger than the average fiber diameter or average pore diameter of any of the fiber aggregates constituting the filtration layer.

[10] A method for manufacturing a cylindrical filter including a core material and a filtration layer wound around the core material, The filtration layer includes a filtration layer A and a filtration layer B wound in this order from the outflow side of the object to be filtered, a winding step A for forming a filtration layer A by winding only the fiber aggregate A around the core material by a predetermined length, or by winding the fiber aggregate A and the coarse nonwoven fabric together by overlapping them by a predetermined length so that the fiber aggregate A is closer to the core material than the coarse nonwoven fabric; and a winding step B for forming a filtration layer B by winding only a fiber aggregate B around the filtration layer A by a predetermined length, or by winding the fiber aggregate B and the coarse nonwoven fabric together by overlapping them by a predetermined length so that the fiber aggregate B is closer to the filtration layer A than the coarse nonwoven fabric; the average pore size PA of the fiber assembly A and the average pore size PB of the fiber assembly B are different, and the average pore size PA / average pore size PB is 0.05 or more and 0.95 or less; The coarse nonwoven fabric has an average fiber diameter larger than that of both the fiber aggregate A and the fiber aggregate B, and has at least one selected from the following (i), (ii), and (iii): It fulfills A method for producing a cylindrical filter, comprising winding at least one of the fiber aggregate A and the fiber aggregate B in a state where the fiber aggregate A and the coarse nonwoven fabric are overlapped with each other. (i) Air permeability is 150 cm 3 / (cm 2 ·s) more than 500cm 3 / (cm 2 ·s) or less (ii) The load (N) required to compress it to 30% is 50N or more and 1500N or less. (iii) Compression rate under a 100N load is 25% or more and 70% or less

[11] The method for producing a cylindrical filter according to

[10] further comprises a winding step C of forming a filtration layer C by winding only a fiber aggregate C around the filtration layer B by a predetermined length, or by overlapping the fiber aggregate C and the coarse nonwoven fabric and winding the fiber aggregate C by a predetermined length around the filtration layer B so that the fiber aggregate C is closer to the filtration layer B than the coarse nonwoven fabric, wherein the average fiber diameter of the fiber aggregate C is smaller than the average fiber diameter of the coarse nonwoven fabric, the average pore diameter PC of the fiber aggregate C is different from the average pore diameter PA of the fiber aggregate A and the average pore diameter PB of the fiber aggregate B, and the average pore diameter PB / average pore diameter PC is 0.05 or more and 0.95 or less.

[12]

[12] The method for manufacturing a cylindrical filter according to

[11] , wherein in the winding step B, an end of the fiber aggregate B is overlapped on an end of the fiber aggregate A, and then the fiber aggregate B is wound; and / or in the winding step C, an end of the fiber aggregate C is overlapped on an end of the fiber aggregate B, and then the fiber aggregate C is wound.

[13] In the winding step A, the length of winding only the fiber aggregate A or the length of winding the fiber aggregate A and the coarse nonwoven fabric in a superposed state is 0.5 m or more and 10 m or less, In the winding step B, the length of winding only the fiber aggregate B or the length of winding the fiber aggregate B and the coarse nonwoven fabric in a superposed state is 0.5 m or more and 10 m or less, The method for producing a cylindrical filter according to

[11] or

[12] , wherein in the winding step C, the length over which only the fiber aggregate B is wound, or the length over which the fiber aggregate B and the coarse nonwoven fabric are wound together is 0.5 m or more and 10 m or less.

[14] The method for manufacturing a cylindrical filter according to any one of

[11] to

[13] , wherein in the winding step B, the fiber aggregate A and the fiber aggregate B are overlapped so that an end of the fiber aggregate A and an end of the fiber aggregate B overlap each other by 3 cm or more and 15 cm or less, and then the fiber aggregate B is wound; and / or in the winding step C, the fiber aggregate B and the fiber aggregate C are overlapped so that an end of the fiber aggregate B and an end of the fiber aggregate C overlap each other by 3 cm or more and 15 cm or less, and then the fiber aggregate C is wound.

[15] At least one fiber aggregate selected from the fiber aggregate A, the fiber aggregate B, and the fiber aggregate C is a fiber aggregate having a coarse-dense structure in the thickness direction, The method for producing a cylindrical filter according to any one of

[11] to

[14] , wherein the fiber assembly having a coarse-dense structure in the thickness direction is wound so that the dense surface is disposed on the outflow side of the object to be filtered.

[16] The method for producing a cylindrical filter according to any one of

[10] to

[15] , wherein the coarse nonwoven fabric used in the winding step A and the coarse nonwoven fabric used in the winding step B are the same continuous nonwoven fabric. [Industrial Applicability]

[0150] The cylindrical filter of the present invention can be suitably used for filtering liquids such as beverages, chemical solutions, oils and fats, paints, and industrial cleaning water such as cleaning water for electronic parts and semiconductor products. [Explanation of symbols]

[0151] 1 cylindrical filter 2 Core material 3 Filtration layer 310 Filtration layer A 320 Filtration layer B 330 Filtration layer C 311 Fiber assembly A 312 Coarse non-woven fabric 321 Fiber assembly B 322 Coarse non-woven fabric 331 Fiber assembly C 332 Coarse non-woven fabric 4 Outer layer 100 Rewind Project A 200 Rewinding Project B 300 Rewind Project C 400 Outer layer formation engineering

Claims

1. A cylindrical filter including a core material and a filtration layer wound around the core material, The filtration layer includes a filtration layer A and a filtration layer B wound continuously in order from the outflow side of the object to be filtered, The filtration layer A includes a fiber aggregate A, and the filtration layer B includes a fiber aggregate B, the average pore size PA of the fiber assembly A and the average pore size PB of the fiber assembly B are different, and the ratio of the average pore size PA / the average pore size PB is 0.05 or more and 0.95 or less; At least one of the fiber aggregate A and the fiber aggregate B is wound in a state where it is overlapped with a coarse nonwoven fabric, The coarse nonwoven fabric has an average fiber diameter larger than that of both the fiber aggregate A and the fiber aggregate B, and satisfies at least one of the following (i), (ii), and (iii): (i) Air permeability is 150 cm 3 / (cm 2 ・s) or more 500cm 3 / (cm 2 ・s) or less (ii) The load (N) required when compressed to 30% is 50N or more and 1500N or less. (iii) Compression rate under a load of 100 N is 25% or more and 70% or less

2. 2. The cylindrical filter according to claim 1, wherein the average fiber diameter of the coarse nonwoven fabric is 40 μm or more and 120 μm or less.

3. The cylindrical filter according to claim 1 , wherein the fibers constituting the coarse nonwoven fabric form fiber intersections where the fibers come into contact with each other, and the fibers are bonded to each other at at least some of the fiber intersections.

4. 4. The cylindrical filter according to claim 3, wherein the coarse nonwoven fabric is at least one selected from the group consisting of an air-through nonwoven fabric and a chemically bonded nonwoven fabric.

5. The cylindrical filter according to claim 1 , wherein the fiber aggregate A and the fiber aggregate B are both meltblown nonwoven fabrics.

6. The filtration layer includes a filtration layer A, a filtration layer B, and a filtration layer C which are wound continuously in order from the outflow side of the object to be filtered, The filtration layer C includes a fiber aggregate C having an average fiber diameter smaller than that of the coarse nonwoven fabric, The cylindrical filter according to any one of claims 1 to 5, wherein the average pore size PC of the fiber assembly C is different from the average pore size PA of the fiber assembly A and the average pore size PB of the fiber assembly B, and the average pore size PB / average pore size PC is 0.05 or more and 0.95 or less.

7. 7. The cylindrical filter according to claim 6, wherein each of the fiber aggregates B and C is wound around the coarse nonwoven fabric in a state where the fiber aggregates B and C are overlapped with the coarse nonwoven fabric.

8. 7. The cylindrical filter according to claim 6, wherein the fiber aggregate A, the fiber aggregate B, and the fiber aggregate C are all wound in a state where they are overlapped with the coarse nonwoven fabric.

9. Further, an outer layer is disposed on the inlet side of the filtration layer to which the object to be filtered is introduced, 2. The cylindrical filter according to claim 1, wherein the average fiber diameter or average pore diameter of the fiber aggregate constituting the outer layer is larger than the average fiber diameter or average pore diameter of any of the fiber aggregates constituting the filtration layers.

10. A method for manufacturing a cylindrical filter including a core material and a filtration layer wound around the core material, The filtration layer includes a filtration layer A and a filtration layer B wound in this order from the outflow side of the object to be filtered, a winding step A in which only the fiber aggregate A is wound around the core material by a predetermined length, or in which the fiber aggregate A and the coarse nonwoven fabric are overlapped and wound around the core material by a predetermined length so that the fiber aggregate A is closer to the core material than the coarse nonwoven fabric; and a winding step B for forming a filtration layer B by winding only a fiber aggregate B around the filtration layer A by a predetermined length, or by winding the fiber aggregate B and the coarse nonwoven fabric together by overlapping the fiber aggregate B by a predetermined length around the filtration layer A so that the fiber aggregate B is closer to the filtration layer A than the coarse nonwoven fabric; the average pore size PA of the fiber assembly A and the average pore size PB of the fiber assembly B are different, and the ratio of the average pore size PA / the average pore size PB is 0.05 or more and 0.95 or less; The coarse nonwoven fabric has an average fiber diameter larger than both the fiber aggregate A and the fiber aggregate B, and satisfies at least one of the following (i), (ii), and (iii): A method for producing a cylindrical filter, comprising winding at least one of the fiber aggregate A and the fiber aggregate B in a state where the fiber aggregate A and the fiber aggregate B are overlapped with the coarse nonwoven fabric. (i) Air permeability is 150 cm 3 / (cm 2 ・s) or more 500cm 3 / (cm 2 ・s) or less (ii) The load (N) required when compressed to 30% is 50N or more and 1500N or less. (iii) Compression rate under a load of 100 N is 25% or more and 70% or less

11. 11. The method for producing a cylindrical filter according to claim 10, further comprising a winding step C of forming the filtration layer C by winding only the fiber aggregate C around the filtration layer B for a predetermined length, or by overlapping the fiber aggregate C and the coarse nonwoven fabric and winding the fiber aggregate C for a predetermined length around the filtration layer B so that the fiber aggregate C is closer to the filtration layer B than the coarse nonwoven fabric, wherein the average fiber diameter of the fiber aggregate C is smaller than the average fiber diameter of the coarse nonwoven fabric, the average pore diameter PC of the fiber aggregate C is different from the average pore diameter PA of the fiber aggregate A and the average pore diameter PB of the fiber aggregate B, and the average pore diameter PB / average pore diameter PC is 0.05 or more and 0.95 or less.

12. 12. The method for manufacturing a cylindrical filter according to claim 11, wherein in the winding step B, an end of the fiber aggregate B is overlapped on an end of the fiber aggregate A and then the fiber aggregate B is wound, and / or in the winding step C, an end of the fiber aggregate C is overlapped on an end of the fiber aggregate B and then the fiber aggregate C is wound.

13. In the winding step A, the length of winding only the fiber aggregate A or the length of winding the fiber aggregate A and the coarse nonwoven fabric in a superposed state is 0.5 m or more and 10 m or less, In the winding step B, the length of winding only the fiber aggregate B or the length of winding the fiber aggregate B and the coarse nonwoven fabric in a superposed state is 0.5 m or more and 10 m or less, 12. The method for manufacturing a cylindrical filter according to claim 11, wherein in the winding step C, the length over which only the fiber aggregate B is wound, or the length over which the fiber aggregate B and the coarse nonwoven fabric are wound together is 0.5 m or more and 10 m or less.

14. 12. The method for manufacturing a cylindrical filter according to claim 11, wherein in the winding step B, the fiber aggregate A and the fiber aggregate B are overlapped with each other so that an end of the fiber aggregate A and an end of the fiber aggregate B overlap each other by 3 cm or more and 15 cm or less, and then the fiber aggregate B is wound; and / or in the winding step C, the fiber aggregate B and the fiber aggregate C are overlapped with each other so that an end of the fiber aggregate B and an end of the fiber aggregate C overlap each other by 3 cm or more and 15 cm or less, and then the fiber aggregate C is wound.

15. at least one fiber aggregate selected from the fiber aggregate A, the fiber aggregate B, and the fiber aggregate C is a fiber aggregate having a coarse-dense structure in a thickness direction, The method for manufacturing a cylindrical filter according to claim 11, wherein the fiber assembly having a coarse-dense structure in the thickness direction is wound so that the dense surface is disposed on the outflow side of the object to be filtered.

16. The method for producing a cylindrical filter according to claim 10, wherein the coarse nonwoven fabric used in the winding step A and the coarse nonwoven fabric used in the winding step B are the same continuous nonwoven fabric.

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