Fiber structure, three-dimensional filter, and filter for filtration

Abstract

The invention provides a fiber structure and a three-dimensional filter using the fiber structure. A fiber structure (10) is provided with an opening (2) and a protruding part (8) protruding from the opening (2), the protruding part (8) is provided with a side wall part (4) formed on the side surface and a bottom part (6) formed on the bottom surface, and the depth (D) of a cavity part (5) between the opening (2) and the bottom part (6) is 5-75 mm.

Description

[0001] Related Application

[0002] This application claims the priority of Japanese Patent Application No. 2022-187546 filed in Japan on November 24, 2022, and is incorporated herein by reference in its entirety as part of this application. Technical Field

[0003] The present invention relates to a fibrous structure having a protrusion protruding from an opening, and a three-dimensional filter using the fibrous structure. Background Art

[0004] Since the fibrous structure has numerous minute voids between fibers, it is used as a filter material by allowing liquids and gases to pass through the voids. In order to increase the surface area as a filtration area and improve the filter function, it can be processed into various shapes for use.

[0005] For example, Patent Document 1 (Japanese Utility Model Laid-Open No. 5-44218) discloses a filter material composed of a non-woven fabric that has been pleated by continuous annular pleat lines.

[0006] In addition, as an invention for increasing the surface area by a method other than pleating, for example, in Patent Document 2 (Japanese Patent No. 5179939), as a fibrous sheet composed of a non-woven fabric, having a three-dimensional shape, a large surface area, and excellent morphological stability, there is disclosed a fibrous structure including a flat plate-like mesh member (A) composed of linear bodies and a non-woven fabric member (B). The non-woven fabric member (B) is composed of a mesh-like base portion welded to the linear bodies and a plurality of bulging portions that bulge in a direction opposite to the mesh-like base portion in each mesh of the flat plate-like mesh member (A). Among them, the average pore diameter of the mesh of the mesh-like base portion is 1 to 30 mm, and the ratio of the average diameter of the linear bodies to the average pore diameter of the mesh of the mesh-like base portion is average diameter of linear bodies / average pore diameter of mesh = 1 / 1 to 1 / 100. The average height of the bulging portions is 1.5 to 8 mm, the thickness of the bulging portions is 0.5 to 5 mm, and the ratio of the two is average height / thickness = 1.05 / 1 to 5 / 1. The ratio of the average height of the bulging portions to the average pore diameter of the mesh of the mesh-like base portion is average height / average pore diameter = 1 / 5 to 2 / 1. The density of the mesh-like base portion is 0.05 to 0.5 g / cm 3 , and the density of the bulging portions is 0.001 to 0.2 g / cm 3 , and the ratio of the two densities is mesh-like base portion / bulging portion = 3 / 1 to 50 / 1.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Utility Model Laid-Open Publication No. 5-44218

[0010] Patent Document 2: Japanese Patent No. 5179939

[0011] Content of the Invention

[0012] Problems to be Solved by the Invention

[0013] However, for the pleated filter of Patent Document 1, not only is the productivity reduced due to the pleating process, but it is also difficult to stabilize the quality during the pleating process. In addition, for the three-dimensional filter of Patent Document 2, considering the thickness of the protruding portion itself, since the depth of the protruding portion is insufficient, there is room for improvement in terms of the life of the filter when used as a three-dimensional filter.

[0014] Therefore, an object of the present invention is to provide a fibrous structure having a protruding portion, wherein the protruding portion has a cavity portion with a sufficient depth, for example, the life of the filter can be improved when used as a three-dimensional filter.

[0015] Means for Solving the Problems

[0016] That is, the present invention can be configured in the following manner.

[0017] [Mode 1]

[0018] A fibrous structure including an opening portion and a protruding portion protruding from the opening portion, wherein

[0019] the protruding portion includes a side wall portion formed on the side surface and a bottom portion formed on the bottom surface, and the depth (D) of the cavity portion existing between the opening portion and the bottom portion in the protruding portion is 5 to 75 mm (preferably 8 to 65 mm, more preferably 10 to 55 mm, and further preferably 15 to 55 mm).

[0020] [Mode 2]

[0021] The fibrous structure according to Mode 1, wherein

[0022] the area B of the ideal cone calculated based on the depth (D) of the cavity portion and the area (R) of the opening portion is 550 to 8000 mm 2 (preferably 600 to 5000 mm 2 , more preferably 700 to 3000 mm 2 ).

[0023] [Mode 3]

[0024] The fibrous structure according to Mode 1 or 2, wherein

[0025] The ratio (B / R) of the area B of the ideal cone calculated based on the depth (D) of the cavity portion and the area (R) of the opening portion to the area (R) of the opening portion is 1.1 or more (preferably 1.2 or more, more preferably 1.3 or more, and particularly preferably 1.4 or more).

[0026] [Mode 4]

[0027] For the fibrous structure according to any one of Modes 1 to 3, wherein

[0028] The average area (R) of the opening portion is 200 mm 2 or more (preferably 300 mm 2 or more, more preferably 400 mm 2 or more).

[0029] [Mode 5]

[0030] For the fibrous structure according to any one of Modes 1 to 4, wherein

[0031] The ratio (Tb / Ta) of the thickness Tb of the bottom portion to the thickness Ta of the opening portion is 20 to 500 (preferably 30 to 400).

[0032] [Mode 6]

[0033] For the fibrous structure according to any one of Modes 1 to 5, wherein

[0034] The ratio (Tb / D) of the thickness Tb of the bottom portion to the depth D of the cavity portion is 2 or less (preferably 1.5 or less).

[0035] [Mode 7]

[0036] For the fibrous structure according to any one of Modes 1 to 6, wherein

[0037] The ratio (D / H) of the depth D of the void portion to the height H of the protruding portion is 0.35 to 0.99 (preferably 0.40 to 0.98).

[0038] [Mode 8]

[0039] For the fibrous structure according to any one of Modes 1 to 7, wherein

[0040] The protruding portion is composed of a bulging portion.

[0041] [Mode 9]

[0042] For the fibrous structure according to any one of Modes 1 to 8, it further includes a support body composed of a wire body, and the opening portion is supported by the support body.

[0043] [Mode 10]

[0044] The fibrous structure according to any one of Modes 1 to 9 has a plurality of protrusions, and for every 10,000 mm 2 the number of protrusions is 5 to 50 per 10,000 mm 2 (preferably 7 to 40 per 10,000 mm 2 and more preferably 8 to 30 per 10,000 mm 2 ).

[0045] [Mode 11]

[0046] A three-dimensional filter comprising:

[0047] The fibrous structure according to any one of Modes 1 to 10.

[0048] [Mode 12]

[0049] A filter for filtration comprising:

[0050] A module in which the end of the fibrous structure according to any one of Modes 1 to 10 is fixed to a housing.

[0051] When used in this specification, unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" include the plural forms including "at least one". When used in this specification, the terms "and / or", "at least 1", and "more than 1" include any and all combinations of the relevant listed items.

[0052] It should be noted that any combination of at least two components disclosed in the claims and / or the specification and / or the drawings is also included in the present invention. In particular, any combination of two or more claims recited in the claims is also included in the present invention.

[0053] Effects of the Invention

[0054] According to the present invention, since the fibrous structure forms protrusions having cavity portions and the cavity portions have a specific depth, for example, when used as a three-dimensional filter, the depth of the cavity portions can be utilized to increase the accumulation amount of the filtered matter and extend the life of the filter. Description of the Drawings

[0055] The present invention can be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and the drawings are only for illustration and explanation, and should not be used to limit the scope of the present invention. The scope of the present invention is determined by the claims. It should be noted that the following drawings are schematic diagrams for illustration, and the dimensions of each part do not reflect the actual dimensional ratio. In different drawings, the same reference numerals are used for common components and the description thereof is omitted.

[0056] Figure 1 is an enlarged schematic cross-sectional view showing the opening and the protruding portion in the fiber structure for explaining one mode of the present invention.

[0057] Figure 2 is an enlarged schematic perspective view showing the opening and the protruding portion in the fiber structure for explaining one mode of the present invention.

[0058] Figure 3 is for explaining Figure 2 the ideal cone of the cavity portion in the fiber structure of.

[0059] Figure 4 is a schematic perspective view showing the fiber structure of one mode of the present invention.

[0060] Figure 5 is an enlarged schematic top view showing the opening of the fiber structure for explaining one mode of the present invention.

[0061] Figure 6 is an enlarged schematic perspective view showing the meltblown forming method of the fiber structure for explaining one mode of the present invention.

[0062] Figure 7 is an electron micrograph of the cross-section in the thickness direction of the fiber structure obtained in Example 1.

[0063] Symbol Explanation

[0064] 10 ··· Fiber structure

[0065] 2 ··· Opening

[0066] 2a ··· Open end

[0067] 3 ··· Top surface

[0068] 4, 34 ··· Side wall portion

[0069] 5, 35 ··· Cavity portion

[0070] 6, 36 ··· Bottom

[0071] 8, 38 ··· Protruding portion (bulging portion)

[0072] 9... Support

[0073] 20... Nozzle

[0074] 21... High-temperature gas

[0075] 24... Molten polymer

[0076] 26... Fiber flow

[0077] 29... Collector

[0078] 251... Notch for hanging ear

[0079] 260, 261, 262... Joint Detailed implementation mode

[0080] (Fiber structure)

[0081] The fiber structure of one embodiment of the present invention includes an opening and a protruding portion protruding from the opening. Figure 1 It is an enlarged schematic cross-sectional view for explaining the opening and the protruding portion in the fiber structure of one embodiment. The fiber structure 10 includes an opening 2 and a protruding portion 8 extending from the opening end 2a of the opening 2.

[0082] In Figure 1 , the protruding portion 8 is composed of a side wall portion 4 having the opening end 2a as the upper end and extending downward, and a bottom portion 6 continuously formed from the side wall portion 4, and a cavity portion 5 is formed inside thereof. It should be noted that the opening of the opening 2 shown by the dotted line is sometimes referred to as the top surface 3.

[0083] Figure 2 Fig. shows a three-dimensional schematic view observed from the protruding portion side in the fiber structure 10 formed by adjacent multiple protruding portions 8. In Figure 2 , from the viewpoint of explaining the state of the protruding portion, the state in which the multiple protruding portions 8 of the fiber structure 10 protrude upward is described. It should be noted that a cavity portion (not shown) with a given depth is formed in each of the protruding portions 8 in the fiber structure 10.

[0084] Figure 1 Is a view of extracting one protruding portion 8 in the fiber structure 10 in which multiple protruding portions 8 are formed adjacent to each other as shown in Figure 2 . In the opening 2, the boundary with the adjacent protruding portion is indicated by a wavy line.

[0085] Since the side wall portion 4 and the bottom portion 6 are continuously formed, it is sometimes difficult to clearly distinguish the boundary between the side wall portion 4 and the bottom portion 6. In such a case, the portion continuous from the opening end 2a can be judged as the representative portion of the side wall portion 4, or the portion forming the bottom surface of the protruding portion 8 can be judged as the representative portion of the bottom portion 6.

[0086] The opening 2 has a thickness Ta. In addition, the bottom 6 has a thickness Tb. The thickness Tb of the bottom 6 is a value obtained as follows: in a cross-sectional plane that bisects the protruding portion with a plane including the center point of the opening, when the most prominent point in the protruding portion is taken as the vertex P of the protruding portion, on a straight line perpendicular to the top surface 3 from the vertex P, the thickest portion is taken as the thickness of the protruding portion, and the value obtained by measuring the protruding portion with a vernier caliper.

[0087] It should be noted that the opening 2 can also be supported by a support 9. In Figure 1 the support 9 on the right side is omitted, and only the support on the left side is described. When there is a support 9, the support 9 is preferably bonded or welded to at least a part of the opening 2.

[0088] Figure 3 It is an enlarged schematic perspective view of the opening 2 and the protruding portion 8 in the fiber structure for explaining one mode. Figure 3 It is a view showing a part of a plurality of adjacent protruding portions 8 arranged, and in the opening 2, the boundary with the adjacent protruding portion is indicated by a wavy line.

[0089] The protruding portion 8 has a cavity portion 5 with a depth D above the bottom 6. Here, in order to easily evaluate the cavity portion 5 of the protruding portion 8, as a hypothetical figure, in Figure 3 the protruding portion 8 in, with the top surface 3 of the opening 2 as the base, an ideal cone C with the depth D of the cavity portion 5 as the height is depicted by a dotted line.

[0090] Figure 3 The depth D of the cavity portion 5 shown has the depth at the time when a vernier caliper is inserted from the top surface 3 of the opening 2 and the vernier caliper contacts the fiber forming the bottom. For example, when the bottom of the protruding portion is formed by a plurality of fiber layers, the depth D is the distance from the top surface 3 of the opening to the bottom surface of the fiber layer closest to the opening side.

[0091] On the other hand, in the protruding portion 8, the height H is the distance from the top surface 3 of the opening 2 to the vertex P of the protruding portion 8. For example, when the bottom of the protruding portion is formed by a plurality of fiber layers, the vertex P of the protruding portion exists in the fiber layer farthest from the opening, and the height H is the distance from the top surface 3 of the opening to the vertex P.

[0092] Figure 4 It is for Figure 3 taking out and explaining the ideal cone C described in. The ideal cone C is a cone with the area of the base of the top surface 3 of the opening 2 being R and the height being D. It can be obtained by using Figure 4The volume of the ideal cone shown and the area of the side wall of the ideal cone are used to evaluate the cavity portion of the fibrous structure.

[0093] The protruding portion only needs to have a cavity portion with a sufficient depth, and the shape can be appropriately determined according to the use and manufacturing method. For example, in Figure 1 , the protruding portion is composed of a bulging portion bulged by the blowing treatment during the meltblowing method. It should be noted that in this specification, the protruding portion formed by the meltblown nonwoven fabric is sometimes simply referred to as the bulging portion.

[0094] [Structure of the fibrous structure]

[0095] (Depth of the cavity portion)

[0096] The fibrous structure includes one or more opening portions and a protruding portion protruding from the opening portion. When the fibrous structure has a plurality of protruding portions, the depth of the cavity portion in each protruding portion can be evaluated by the depth D.

[0097] The depth D of the cavity portion is 5 mm or more and 75 mm or less. From the viewpoint of increasing the capacity of the cavity portion, the depth D can be preferably 8 mm or more, more preferably 10 mm or more, and further preferably 15 mm or more. On the other hand, from the viewpoint of improving the shape stability of the cavity portion, the depth D can be preferably 65 mm or less, more preferably 55 mm or less. Details of the measurement method of the depth of the cavity portion are described in the examples below.

[0098] When the fibrous structure has a plurality of protruding portions, the depth of the cavity portion only needs to calculate the average value of the depths of the protruding portions at three points, namely, the two end portions and the central portion, on the straight line cutting across the fibrous structure.

[0099] When there are a plurality of protruding portions, the areal density of the protruding portion can be, for example, 5 to 50 per 10000 mm 2 , preferably 7 to 40 per 10000 mm 2 , more preferably 8 to 30 per 10000 mm 2 . The areal density of the protruding portion can be calculated by 10000 ÷ the base area (mm 2 ).

[0100] (Thickness of the bottom)

[0101] The thickness Tb of the bottom measured by cutting the protruding portion in the thickness direction can be determined according to the use, for example, it can be 0.5 mm or more, preferably 1.0 mm or more, and more preferably 2.0 mm or more. As the upper limit of the thickness of the bottom, it can be appropriately set according to the size of the protruding portion, for example, it can be 30 mm or less. Here, the thickness of the bottom is the value obtained as follows: in the cut surface that bisects the protruding portion with the plane including the center point of the opening, on the straight line perpendicular to the top surface 3, the thickest part is taken as the thickness of the bottom, and the value obtained by measuring the protruding portion with a vernier caliper. Details of the method for measuring the thickness of the bottom are described in the examples below.

[0102] (Ratio of the thickness Tb of the bottom to the depth D of the cavity portion)

[0103] For the protruding portion, it is preferable that the thickness of the bottom is smaller than the depth of the cavity portion. For example, the ratio (Tb / D) of the thickness Tb of the bottom to the depth D of the cavity portion can be 2 or less, preferably 1.5 or less. The lower limit value of the Tb / D ratio is not particularly limited, for example, it can be about 0.01.

[0104] (Ratio of the depth D of the cavity portion to the height H of the protruding portion)

[0105] The ratio of the depth D of the cavity portion to the height H of the protruding portion can be, for example, 0.35 to 0.99, and preferably can be 0.40 to 0.98.

[0106] (Thickness Ta of the opening)

[0107] The thickness Ta of the opening measured by cutting the protruding portion in the thickness direction can be determined according to the use, for example, it can be 0.01 to 0.5 mm, preferably 0.05 to 0.3 mm, and further preferably about 0.1 to 0.2 mm. Here, the thickness of the opening is the average value of the values obtained by selecting 5 opening ends adjacent to the protruding portion through SEM and observing and measuring the thickness respectively through SEM.

[0108] (Width W of the opening)

[0109] The width of the opening can be appropriately determined according to the size and use of the protruding portion. For example, it can be selected from the range of about 10 to 100 mm, for example, it can be 13 to 70 mm, and preferably about 15 to 40 mm.

[0110] It should be noted that the width W of the opening can be measured using a vernier caliper. For example, Figure 5 The enlarged schematic top view for explaining the opening of the fiber structure is shown. As Figure 5As shown, the average value obtained by measuring the width of the opening portion in the direction parallel to the traveling direction (MD) three times with a vernier caliper is defined as W1, and the average value obtained by measuring the width of the opening portion in the direction (TD) orthogonal to the traveling direction (MD) three times with a vernier caliper is defined as W2. The average value of W1 and W2 is measured as the width W of the opening portion. In Figure 5 In the above, a rectangular opening portion has been described, but for other shapes, as long as W1 is determined for the longest width in the traveling direction (MD) of the opening portion, and W2 is determined for the longest width in the direction (TD) orthogonal to the traveling direction (MD).

[0111] (Thickness Tb of the bottom relative to the thickness Ta of the opening portion)

[0112] Regarding the thickness Tb of the bottom relative to the thickness Ta of the opening portion, for the thinner opening end, when the bottom is thicker, for example, in the case of being used as a filter, etc., from the viewpoint of considering both the storage property and the filtering property in packaging, for example, the ratio (Tb / Ta) of the thickness Tb of the bottom to the thickness Ta of the opening portion can be, for example, 20 to 500, preferably 30 to 400.

[0113] (Ratio of the density ρb of the bottom to the density ρa of the opening end)

[0114] In addition, regarding the density of the opening end and the bottom, for example, in the meltblowing method, etc., when formed by ejecting a certain amount of molten polymer, it can be considered that the weight of the polymer ejected per unit area is of the same degree. Therefore, it can be considered that the ratio of the density of the bottom to the density of the opening end is of the same degree as the ratio (Tb / Ta) of the thickness Tb of the bottom to the thickness Ta of the opening portion. Therefore, in the case of a fiber structure formed by the meltblowing method, etc., as the ratio (ρb / ρa) of the density ρb of the bottom to the density ρa of the opening end, for example, it can be 20 to 500, preferably 30 to 400.

[0115] (Density ρb of the bottom of the protrusion)

[0116] Regarding the density ρb of the bottom obtained by density conversion from the density ρa of the opening end, it can be calculated in the form of ρb = ρa×(Tb / Ta) by using the fact that the ratio of the density of the bottom to the density of the opening end (ρb / ρa) is of the same degree as the ratio (Tb / Ta) of the thickness Tb of the bottom to the thickness Ta of the opening portion.

[0117] In this case, the density ρb of the bottom can be, for example, 0.001 to 0.2 g / cm 3 , preferably 0.003 to 0.1 g / cm 3 , more preferably 0.005 to 0.07 g / cm 3(Specifically, it is about 0.01 to 0.05 g / cm 3 ) or so.

[0118] (Area of the opening part)

[0119] The area R of the opening part can be appropriately set according to the use. For example, it can be 200 mm 2 or more, preferably 300 mm 2 or more, more preferably 400 mm 2 or more. There is no particular limitation on the upper limit of the area R of the opening part. For example, it can be 10000 mm 2 .

[0120] Here, the area R of the opening part is the area of the top surface of the fiber structure, which refers to the area projected onto the top surface when the fiber structure is photographed from above. When the fiber structure has multiple protrusions, the area R of the opening part only needs to calculate the average value of the areas of the opening parts at three points, namely the two end parts and the central part, on the straight line cutting across the fiber structure. It should be noted that when the opening area of the support can be easily grasped, from the perspective of simplicity, the opening area of the support can also be used as a representative value.

[0121] The shape of the opening part can also be a polygonal shape (triangle, quadrilateral, pentagon, hexagon, octagon, etc.), circular shape, elliptical shape, irregular shape, etc. Among them, from the perspective of easy manufacturing, a quadrilateral shape (for example, rectangular shape, square shape, rhombus shape, parallelogram shape other than them) is preferred. It should be noted that for the shape of the opening part. Within the range where it can be judged as a polygon, the corners and straight parts of the polygon can also have roundness.

[0122] (Volume of the ideal cone)

[0123] The volume of the ideal cone C that can be calculated based on the area R of the opening part and the depth D of the cavity part can be used as a reference for evaluating the volume of the cavity part. In this case, the volume A of the ideal cone C can be calculated by A = R × D × 1 / 3.

[0124] The volume A of the ideal cone C can be selected from a wide range of, for example, 500 to 600000 mm 3 , preferably 800 to 300000 mm 3 , more preferably 1000 to 100000 mm 3 .

[0125] (Area of the ideal cone)

[0126] In addition, in applications such as filters, since the area of the side wall of the ideal cone affects the filtration efficiency, the fiber structure can also be evaluated using the area of the ideal cone C. In this case, the area B of the side wall of the ideal cone C can be calculated based on the shape of the opening. For example, for a cone with a depth D as the height of the cone and an opening that is an n-sided polygon or a circle, the side wall area A can be calculated using the development diagram of the cone unfolded with each of the n sides as the base or the development diagram of the cone unfolded with the outer circumference of the circle as the base. The lateral area based on such a development diagram of the ideal cone can be appropriately calculated by those skilled in the art.

[0127] When used as a filter, the area B of the side wall of the ideal cone C corresponds to the filtration area. When the filtration area is large, the area for trapping dust is large, so the pressure loss caused by dust clogging is reduced. Therefore, a filter with a large filtration area can achieve both high trapping efficiency and low pressure loss, and thus can improve the filter life. From this point of view, it is preferable that the area B of the side wall of the ideal cone C is large. For this reason, the area B of the side wall of the ideal cone C can be appropriately set according to the application, for example, it can be 550 to 8000 mm 2 , preferably 600 to 5000 mm 2 , more preferably 700 to 3000 mm 2 .

[0128] In addition, the ratio (B / R) of the area B of the side wall of the ideal cone to the area R of the opening corresponds to the filtration area per unit filter area. That is, when the filter area is determined, when B / R is large, the filter can achieve both high trapping efficiency and low pressure loss, and thus can improve the filter life. From this point of view, B / R is preferably 1.1 or more, more preferably 1.2 or more, further preferably 1.3 or more, and particularly preferably 1.4 or more. On the other hand, the upper limit of B / R can be appropriately set according to the application, and from the viewpoint of productivity, it is preferably 6.0 or less.

[0129] (Unit weight per unit area of the fiber structure)

[0130] The unit weight per unit area of the fiber structure is not particularly limited. From the viewpoint of light weight, a smaller unit weight per unit area is preferred. For example, it can be 5 to 200 g / m 2 , preferably 10 to 150 g / m 2 , more preferably 15 to 80 g / m 2 .

[0131] The fiber structure can be formed by a single protrusion or by a plurality of protrusions. The shape of the protrusion can be appropriately set according to the shape of the opening as long as it has a specific depth, and can be, for example, bell-shaped, cylindrical, quadrangular prism-shaped, quadrangular pyramid-shaped, irregularly shaped, etc. In addition, the front end of the protrusion is preferably a shape with roundness. Here, the shape with roundness does not need to be a complete arc shape, and some concave-convex shapes can be formed relative to the ideal arc shape. In the case where the fiber structure has a plurality of protrusions, the plurality of protrusions can be a combination of these shapes, and from the viewpoint of productivity, preferably substantially the same shape.

[0132] [Fibers of fiber structure]

[0133] The fiber structure can be formed, for example, from natural fibers (cellulose fibers such as cotton, kapok, and hemp, protein fibers such as wool and silk, etc.), semi-synthetic fibers (acetate fibers such as triacetate fibers, etc.), regenerated fibers (rayon, polynosic, cuprammonium fibers, lyocell fibers, etc.), synthetic fibers, etc. These fibers can be used alone or in combination of two or more.

[0134] The synthetic fiber may be any fiber that can be spun from a fiber-forming resin by a known technique. Examples of the fiber-forming resin include polyolefin resins (polyolefin resins such as polyethylene and polypropylene). 2-4 Olefin resins, etc.), polyvinyl alcohol resins (ethylene-vinyl alcohol copolymers, etc.), polyvinyl chloride resins (polyvinyl chloride, polyvinylidene chloride, etc.), polyester resins (polyalkylene arylate resins such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, aliphatic polyester resins such as polylactic acid, wholly aromatic polyester resins such as liquid crystal polyester, etc.), polyamide resins (aliphatic polyamide resins such as polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, polyamide 612, semi-aromatic polyamide resins, aromatic polyamide resins such as polyphenylene isophthalamide, polyhexamethylene terephthalamide, polyparaphenylene terephthalamide, etc.), polyurethane resins (urethane polymers obtained by reaction of polyol components such as polyether polyol and polyester polyol with polyisocyanate components, etc.), etc. These fiber-forming resins may be used alone or in combination of two or more thereof. Among them, fibers capable of being melt-blown are preferred, and polyolefin resins, polyester resins, polyamide resins, and polyurethane resins are preferred, and polypropylene resins are particularly preferred.

[0135] The average fiber diameter can be appropriately set according to the size and use of the fiber structure. For example, from the viewpoint of filtration performance, etc., it can be 0.2 to 20 μm, preferably 0.5 to 15 μm, and more preferably 0.7 to 12 μm (especially 1 to 10 μm). The average fiber diameter is the value measured by the method described in the following examples.

[0136] The average fiber length can be selected according to its manufacturing method. For example, the average fiber length can be 10 mm or more, preferably 20 mm or more. In the case of melt-blown nonwoven fabric, it is usually continuous fiber.

[0137] The fiber structure can contain conventional additives according to its use, such as stabilizers (thermal stabilizers such as copper compounds, ultraviolet absorbers, light stabilizers, antioxidants, etc.), antibacterial agents, deodorants, fragrances, colorants (dyes, pigments, etc.), fillers, flame retardants, chargeability improvers (hindered amines, etc.), antistatic agents, conductive agents, plasticizers, lubricants, crystallization rate retardants, etc. These additives can be used alone or in combination of two or more. These additives can be selected according to the type. For example, it can be 0.01 to 30 parts by mass, preferably 0.1 to 20 parts by mass, and more preferably 0.3 to 10 parts by mass (especially 0.5 to 5 parts by mass) relative to 100 parts by mass of the resin component. It should be noted that these additives can be contained in the fiber or attached (supported) on the fiber surface. According to need, the fiber structure can also be electretized.

[0138] In addition, the fiber structure can further include a support body composed of linear bodies, and the above-mentioned opening part is supported by the support body. The linear bodies can be formed corresponding to the shape of the opening part and are formed at the protruding part side at the opening end. The average diameter of the linear bodies can be appropriately set according to the shape and use of the fiber structure, and can be selected from the range of about 0.01 to 10 mm. From the viewpoint of light weight, for example, it can be 0.01 to 3 mm, preferably 0.05 to 2 mm, and more preferably 0.1 to 1 mm (especially about 0.15 to 0.5 mm).

[0139] The linear bodies can be inorganic fibers or organic fibers. As inorganic fibers, for example, glass fibers, carbon fibers, activated carbon fibers, alumina fibers, silicon carbide fibers, boron fibers, Tyranno fibers, metal fibers (gold fibers, silver fibers, copper fibers, steel fibers, aluminum fibers, stainless steel fibers, etc.) can be cited. As organic fibers, natural fibers, synthetic fibers, semi-synthetic fibers, regenerated fibers, etc. can be cited. As organic fibers, the fibers exemplified as the fibers forming the fiber structure can be cited. Among them, from the viewpoint of integration with the fiber, organic fibers composed of the same type of thermoplastic resin as the thermoplastic resin constituting the fiber are preferred.

[0140] These fibers can be used alone or in combination of two or more. The fibers constituting the filament body are not limited to monofilaments, and can also be textile yarns or multifilament yarns. In particular, the combination of two or more fibers can be a blended yarn or multifilament yarn of different types of fibers, or a monofilament yarn in which the synthetic resin as the raw material forms an alloy or composite structure. It should be noted that, from the perspective of simplicity, etc., monofilament yarns composed of a single thermoplastic resin can be commonly used. The cross-sectional shape of the monofilament yarn (the cross-sectional shape perpendicular to the fiber length direction) is not limited to the general circular cross-section or special cross-section [flat shape, elliptical shape, polygonal shape, 3-14 petal shape, T-shaped, H-shaped, V-shaped, dog bone (I-shaped), etc.] which are solid cross-sectional shapes, and can also be a hollow cross-sectional shape, etc., but is usually a circular cross-section.

[0141] [Physical properties of the fiber structure]

[0142] (Air permeability of the fiber structure)

[0143] The fiber structure can, for example, have an air permeability of 1 cm 3 / (cm 2 ·s) or more based on a Frazier-type air permeability meter, and the air permeability can preferably be 10-1000 cm 3 / (cm 2 ·s), more preferably 50-800 cm 3 / (cm 2 ·s), and further preferably 100-700 cm 3 / (cm 2 ·s). Here, the air permeability is the value measured by the method described in the following examples.

[0144] (Collection efficiency)

[0145] The fiber structure can be used, for example, to capture fine particles (for example, fine particles in the range of number average particle size of 0.01-2 μm, preferably 0.05-1 μm, particularly preferably 0.1-0.5 μm, etc.). For example, the collection efficiency of dust under dry conditions can be 30% or more, preferably 40% or more, more preferably 50% or more. Here, the collection efficiency is the value measured by the method described in the following examples.

[0146] (Pressure loss and QF value)

[0147] The pressure loss during the capture of the fibrous structure can be, for example, 5 Pa or less, preferably 4 Pa or less, and more preferably 3 Pa or less. The lower limit of the pressure loss is not particularly limited and can be 0.01 Pa. In addition, the QF value calculated by the following formula based on the above capture efficiency and pressure loss can be 0.2 or more, preferably 0.4 or more, and more preferably 0.8 or more. The upper limit value of the QF value is not particularly limited and can be about 4, for example. Here, the pressure loss and the QF value are values measured by the methods described in the following examples.

[0148] QF (1 / Pa) = -ln(100 - ΔE) / ΔP

[0149] [In the formula, ΔE represents the capture efficiency (%), and ΔP represents the pressure loss (Pa).]

[0150] (Pressure loss during NaCl deposition)

[0151] The fibrous structure can perform capture using the cavity part, and even in a state where a certain amount of powder has already been retained, better capture can be performed. As such an index, for example, the pressure loss measured after pre-depositing 30 mg of NaCl can be 6 Pa or less, preferably 5 Pa or less, and more preferably 4.2 Pa or less. The lower limit of the pressure loss is not particularly limited and can be 0.1 Pa. Here, the pressure loss during NaCl deposition is a value measured by the method described in the following examples.

[0152] (Increase in pressure loss)

[0153] The fibrous structure can perform capture using the cavity part, and even in a state where a certain amount of powder has already been retained, better capture can be performed. As such an index, for example, the increase in pressure loss can be 5 Pa or less, preferably 4 Pa or less, and more preferably 3 Pa or less. Additionally, it is most preferable that there is no increase in pressure loss. In such a case, the increase amount is 0 Pa. Here, the increase in pressure loss is a value measured by the method described in the following examples.

[0154] [Manufacturing method of the fibrous structure]

[0155] For the fibrous structure, as long as the fibers can be formed into a shape with a specific depth, the manufacturing method is not particularly limited. For example, it can be a dry method (carding method, air-laying method) using short fibers, a wet method, or a spunbond method. The preferred manufacturing method is the meltblown molding method. Hereinafter, the meltblown molding method will be described.

[0156] An example of meltblown molding is Figure 6 shown. Figure 6It is an enlarged schematic perspective view for explaining the meltblowing method of the fiber structure of one aspect of the present invention. Among them, in Figure 6 In Figure 6 , the nozzle cross-section is shown for the nozzle 20 to show the internal situation of the nozzle.

[0157] In normal meltblowing, there is no trapping net, and the extremely fine fibers with weldability are trapped on the collector in a folded state, and the trapped fibers are welded to each other to form an integrated sheet.

[0158] On the other hand, in the meltblowing of the above-mentioned fiber structure, by using the opening of the trapping net, the extremely fine fibers can pass through the trapping net in a state of being stretched without being folded. Therefore, the extremely fine fibers passing through the opening will not be folded but stretched, and the fiber shape can be maintained. And at the contact part with each other, the speed is directly attenuated while welding, and finally they gather at the part corresponding to the bottom to form the bottom. In this case, the fiber aggregate can be sheeted while increasing the surface area of the non-woven fabric, and a protrusion formed by the side wall part and the bottom can be formed. At this time, the fibers that do not undergo fiber welding among the fibers stretched by the trapping net exist as the thickness part of the bottom.

[0159] For example, as shown in the photograph of the fiber structure obtained in Example 1 ( Figure 7 ), at the bottom, the stretched fibers can be in a multi-layered state. In this case, each layer exists separately from each other to form independent layers. Therefore, the shapes of each layer are often different. It should be noted that as a method of counting the layers, in the meltblowing process, the fiber group passing through the opening is stretched to form the side wall part, and the layer formed by combining the side wall part from the side towards the center part of the bottom is counted as one layer. In Figure 7 Figure 7 , the bottom can be counted as having 3 layers. In Figure 7 Figure 7 , an intermediate layer is formed between the innermost layer and the outermost layer on the opening side. For example, when used as a filter, even if there are particles leaking from the side of the innermost layer, the leaking particles can be further trapped by the intermediate layer and the outermost layer. In addition, when there are multiple layers at the bottom, the voids between the fibers generated in the outermost layer of the bottom in contact with the vertex X of the protrusion can be larger than the voids between the fibers generated in the innermost layer of the bottom existing on the opposite side of the vertex X of the protrusion. The difference in these voids between the fibers can be confirmed by visual observation in the cross-sectional photograph.

[0160] The molten polymer 24 is ejected from the nozzle 20 together with the jet of the high-temperature gas 21 shown by the downward arrow, and becomes a fiber stream 26 composed of a plurality of fibers refined by the jet blowing the ejected polymer, and collides with the collection net 28 located on the downstream side of the jet. The fiber stream 26 that collides with the collection net 28 uses the opening of the collection net 28 as the drum outlet 32. Further, the fiber stream 26 travels downstream from the collection net 28 and finally forms a protruding portion formed by fibers, that is, a bulging portion 38. A collector 29 is further provided on the downstream side of the collection net 28.

[0161] In such a bulging portion 38, the side wall 34 of the bulging portion 38 is formed by the fiber stream 26 with the drum outlet 32 as the upper end, and the bottom 36 is formed. Both the side wall 34 and the bottom 36 can be formed by fine-fiber fibers by the meltblowing method. In addition, inside the bulging portion 38, a cavity portion 35 is formed by the air flow flowing from the center of the opening portion 28a. It should be noted that in Figure 5 , for simplicity, the fibers forming the opening portion are not shown. The opening portion is formed by the fibers stacked on the collection net 28, and the fiber structure is composed of the opening portion and the bulging portion 38. The collection net 28 moves in the traveling direction of the conveyor shown by the arrow by a usual conveyor or the like.

[0162] The fiber structure only needs to have at least an opening portion and a protruding portion (bulging portion) protruding from the opening portion. The collection net can be removed after the bulging portion is formed by the meltblowing method, or the collection net can be a support body (line body) that strengthens the opening portion of the fiber and is included in the fiber structure. In the case of removing the fiber structure from the collection net, for example, a peeling roller (not shown) can be arranged on the downstream side where the fiber structure is formed in the traveling direction of the conveyor to peel the fiber structure from the collection net.

[0163] The thermoplastic resin (including other additives as required) can be melt-kneaded using a conventional mixer (such as a melt-kneading extruder, etc.). The melting temperature only needs to be able to melt the thermoplastic resin, and there is no particular limitation. It can be selected according to the type of thermoplastic resin. In the case of polypropylene resin, for example, the temperature is 150 to 280 °C, preferably 160 to 250 °C, and more preferably about 180 to 240 °C.

[0164] The thermoplastic resin after melt-kneading is supplied to a spinneret. The spinneret is usually formed with a row of spinning holes, and the interval of the spinning holes is, for example, 100 to 4000 holes / m, preferably 500 to 3000 holes / m, and more preferably about 1000 to 2500 holes / m. The discharge amount per single hole (X) is, for example, 0.01 to 1 g / hole·min, preferably 0.03 to 0.5 g / hole·min, and more preferably about 0.05 to 0.3 g / hole·min. In the case of polypropylene resins, the spinning temperature is, for example, 150 to 300 °C, preferably 200 to 280 °C, and more preferably about 220 to 270 °C. The discharge amount of the molten resin from the spinneret is, for example, 10 to 2000 g / (m·min), preferably 50 to 1000 g / (m·min), and more preferably about 100 to 500 g / (m·min).

[0165] The molten resin is ejected together with high-temperature air (usually at the same temperature as the spinning temperature) from a slit provided near the spinneret toward a mesh member or a support having a given opening area and forms an ultrafine fiber shape. The opening area (Rn) can be selected, for example, from 200 to 10000 mm 2 , and can be preferably 300 to 5000 mm 2 , and more preferably 400 to 2000 mm 2 . It should be noted that, as the mesh member, in the case of using a support having the same opening area, the unit area weight of the support can be selected, for example, from 5 to 200 g / m 2 , and can be preferably 10 to 100 g / m 2 , 15 to 55 g / m 2 .

[0166] The air pressure (Y) can be selected from the range of about 0.001 to 0.06 MPa according to the opening area, the distance to the trapping net, and the size of the desired protrusion. For example, it can be selected from the range of 0.002 to 0.05 MPa, preferably from 0.003 to 0.030 MPa, more preferably from 0.005 to 0.020 MPa, and even more preferably from the range of about 0.005 to 0.013 MPa.

[0167] The air temperature is, for example, a temperature near the spinning temperature, for example, a temperature 0 to 50 °C higher than the spinning temperature, preferably a temperature 3 to 30 °C higher than the spinning temperature, and more preferably a temperature 5 to 20 °C higher than the spinning temperature.

[0168] In addition, in order to adjust the height and shape of the protrusion, it is preferable to adjust the distance between the nozzle opening and the trapping net (trapping distance: Z). The trapping distance can be appropriately selected according to the suction force of the suction device, and can be selected from the range of about 1 to 100 cm, for example, 2 to 50 cm, preferably 3 to 30 cm, and more preferably about 5 to 20 cm (especially 7 to 15 cm).

[0169] In the present invention, the gap formed between the trapping net and the suction device (belt conveyor) only needs to be a distance that can form the desired protrusion height and can perform suction. For example, it can be 10 mm or more, preferably 20 to 300 mm, and more preferably about 30 to 200 mm, so that the fiber structure blown by air pressure can form a protrusion.

[0170] For example, according to the opening area and the size of the desired protrusion, the manufacturing conditions can be appropriately changed. As an example of the manufacturing conditions when manufacturing the fiber structure, if the opening areas are of the same degree, it is preferable that the trapping distance is small and the air pressure is low.

[0171] For example, when setting the above-mentioned single-hole ejection amount (X: g / hole·min), air pressure (Y: MPa), trapping distance (Z: cm), and opening area (Rn: mm 2 ), when setting (Y×Z) / (X×Rn)×10000, it can be adjusted so that it is 28 or less.

[0172] In addition, if the opening area, single-hole ejection amount, and trapping distance are of the same degree, when the air pressure is low, there is a tendency to deepen the depth of the cavity part.

[0173] In addition, if the opening area, single-hole ejection amount, and air pressure are of the same degree, when the trapping distance is small, there is a tendency to deepen the depth of the cavity part.

[0174] In addition, if the opening area, trapping distance, and air pressure are of the same degree, when the single-hole ejection amount is high, there is a tendency to deepen the depth of the cavity part.

[0175] The unit area weight of the fiber structure can be adjusted by controlling the supply speed (conveyor speed) of the flat net member. The conveyor speed is, for example, 1 to 200 m / minute, preferably 2 to 100 m / minute, and more preferably about 3 to 50 m / minute (especially 5 to 30 m / minute). In the present invention, by appropriately adjusting the conveyor belt speed, trapping distance, and air pressure, a fiber structure with a desired protrusion shape can be obtained.

[0176] The thus obtained fibrous structure can be charged by conventional electretization treatment. As conventional methods, for example, there can be cited: a method of charging by friction or contact, a method of irradiating active energy rays (such as electron beams, ultraviolet rays, X-rays, etc.), a method of using gas discharges such as corona discharge and plasma, a method of applying a high electric field, a hydrocharging method in which ultrasonic vibration acts via a polar liquid such as water, etc.

[0177] In the hydrocharging method, for example, a polar solvent such as water or an organic solvent (preferably water from the viewpoint of productivity such as wastewater treatment) is sprayed onto the fibrous structure, or it is vibrated while spraying, or it is sucked from one side of the fibrous structure after or while being given, whereby the polar solvent penetrates into the fibrous structure to make it charged. The pressure of the polar solvent colliding with the fibrous structure can preferably be 0.1 to 5 MPa. The suction pressure from the lower part can preferably be 500 to 5000 mmHg₂O. The treatment time of hydrocharging can preferably be 0.001 to 5 seconds.

[0178] (Use of the fibrous structure)

[0179] The fibrous structure can be used for various applications in industrial, agricultural, and living materials, etc., such as filters, wipers, separators, capacitors, capacitive microphones, ultrasonic diagnostic transducers, cushioning materials, etc.

[0180] In particular, it is useful as various filters, liquid filters in the pharmaceutical industry, electronics industry, food industry, automotive industry, etc., filters in the household appliance field (such as air purifiers, air conditioners, etc.), filters in the industrial field (such as bag filters, pre-filters, medium-performance filters, etc.), filters in the automotive industry (such as cabin filters, etc.).

[0181] (Three-dimensional filter)

[0182] In addition, in the case of utilizing the three-dimensional structure of the fibrous structure, the fibrous structure can be housed in a housing of a given shape and used as a three-dimensional filter. The three-dimensional filter can be used as a filter for fluids such as gases or liquids, preferably a filter having a filtering function for gases. When used as a filtering filter, the three-dimensional filter can be used with the opening of the fibrous structure facing the upstream side and the protruding part facing the downstream side when filtering the fluid.

[0183] In a fibrous structure having a plurality of protrusions, the plurality of protrusions protrude from one surface, and a plurality of continuous void portions are independently arranged. Therefore, each void portion can independently exhibit trapping performance like an insect net. In such a fibrous structure, the thickness of the filter can be suppressed to a low thickness derived from the height of the protrusions. On the other hand, when compared with a pleated shape having the same thickness, a larger surface area can be obtained by the plurality of protrusions than that of a linear pleated shape. As a result, it is possible to contribute not only to the trapping efficiency of the filter but also to the long life of the filter.

[0184] In addition, a function based on a filling material can be imparted by filling particulate matter such as activated carbon into the void portions of the three-dimensional filter, and excellent filterability can be achieved. Here, filling means a state in which particulate matter is introduced into at least a part of the void portion, and it may not be a state in which the entire void portion is filled with the particulate matter.

[0185] Furthermore, the fibrous structure can be used as a modular three-dimensional filter in a state where its end portion is fixed to a housing. For a modular three-dimensional filter, not only the operability of the filtering device is improved, but it can also be used as a replacement filter.

[0186] When housed in a housing, the fibrous structure may not be subjected to pleating processing that is usually performed to increase the surface area of the filter material, that is, it can be used in an unpleated manner.

[0187] Examples

[0188] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited by any of the examples. In the following examples and comparative examples, various physical properties were measured by the following methods.

[0189] [Depth D of the cavity portion]

[0190] The depth D of the cavity portion of the fibrous structure was measured by inserting the depth rod of a vernier caliper (manufactured by MITUTOYO CORPORATION, CD-20C) into the cavity portion of the fibrous structure and measuring the depth. Specifically, the vernier caliper was inserted from the opening side, and the moment when the vernier caliper contacted the fiber constituting the bottom was measured as the depth. One measurement was performed for one protrusion. When the fibrous structure had a plurality of protrusions, the depth of the cavity portion was calculated as the average of the depths of the protrusions at three points, namely, the two end portions and the central portion on a straight line cutting across the fibrous structure.

[0191] It should be noted that during the measurement, in order to adjust the shape of the protrusion, within the range where the joining between fibers remains unchanged, the shape of the protrusion can be adjusted by air ventilation from the opening side, or suction from the protrusion side, or by implementing both, and then the depth is measured. Specifically, air is blown at a pressure of 0.5 MPa for 1 minute from a position 10 cm away from the opening of the protrusion to bulge the protrusion. Then, the blowing of air is stopped, and when the change in the shape of the protrusion disappears, it is judged as "the structure of the protrusion is stable", and the depth can be measured.

[0192] [Thickness Ta of the opening part]

[0193] The fiber structure is cut by a cross-section passing through the center of the protrusion, and this cross-section is photographed with a scanning electron microscope (SEM) (magnification: 35 - 200 times, any magnification including the height of the protrusion). The thickness Ta of the opening part and the thickness Tb of the bottom are obtained from the photograph. It should be noted that the maximum thickness of the protrusion is measured. The ratio is calculated using the scale in the photograph at any magnification. The thickness is measured at 5 randomly selected points from the photograph, and the average value is adopted.

[0194] [Thickness Tb of the bottom]

[0195] The thickness Tb of the bottom of the fiber structure is obtained by cutting the protrusion in half along the MD direction. Then, the thickness is measured using a vernier caliper (manufactured by MITUTOYO CORPORATION, CD - 20C). One measurement is performed for one protrusion. In the case where the fiber structure has multiple protrusions, the depth of the cavity part is calculated as the average value of the depths of the protrusions at three points, namely, the two end parts and the central part on a straight line cutting across the fiber structure.

[0196] [Width of the opening part]

[0197] The width W of the opening part of the fiber structure is measured by using a vernier caliper to measure each side of the opening part. For one opening part, a total of 2 measurements are performed in the MD direction (W1) and the CD direction (W2). In the case where the fiber structure has multiple opening parts, the width of the opening part is calculated as the average value of the widths of the opening parts at three points, namely, the two end parts and the central part on a straight line cutting across the fiber structure.

[0198] [Area R of the opening part]

[0199] It is calculated by multiplying the width W1 and W2 of the opening part. It should be noted that the area of the opening part can also be measured from the photograph of the opening part. In this case, in the case where the fiber structure has multiple opening parts, the area of the opening part is calculated as the average value of the widths of the opening parts at three points, namely, the two end parts and the central part on a straight line cutting across the fiber structure.

[0200] [Average fiber diameter]

[0201] The fiber structure was photographed with a scanning electron microscope (SEM) at a magnification of 1000 times, and the diameters of any 50 fibers in the photograph were measured, and the average value was calculated.

[0202] [Air permeability]

[0203] The measurement was carried out by the Frazier method in accordance with JIS L 1913 (2010).

[0204] [Collection efficiency, pressure loss and QF value]

[0205] The filter characteristics of the fiber structure were evaluated using a filter evaluation device (manufactured by TSI Inc., model 8130A). First, the test sample was installed in the measurement unit so that the diameter of the filter surface was 110 mm. An aqueous NaCl solution with a concentration of 2.0 wt% was installed in the filter evaluation device to generate NaCl particles with a number average diameter of 0.26 μm as test dust. Air containing the generated NaCl dust (dust concentration D1: 200 mg / m 3 ) was allowed to flow at a flow rate of 32 liters per minute through the measurement unit equipped with the filter for 10 seconds, and the dust concentration D1 on the upstream side and the dust concentration D2 on the downstream side (after filtration) were measured using a light scattering mass concentration meter, and the collection efficiency was calculated from the following formula.

[0206] Collection efficiency (%) = {(D1 - D2) / D1} × 100

[0207] In addition, a differential pressure gauge was arranged between the upstream side and the downstream side of the measurement unit in the filter evaluation device, and the differential pressure (pressure loss) at a flow rate of 32 liters per minute was measured. Further, based on the natural logarithm of the filter transmittance calculated from the above collection efficiency and the value of the pressure loss, the QF value was calculated from the following formula.

[0208] QF (1 / Pa) = -ln(100 - ΔE) / ΔP

[0209] [In the formula, ΔE represents the collection efficiency (%), and ΔP represents the pressure loss (Pa).]

[0210] [Pressure loss during NaCl accumulation]

[0211] The filter characteristics of the fibrous structure were evaluated using a filter evaluation device (TSI, model 8130A). First, the test sample was installed in the measuring unit such that the diameter of the filter surface was 110 mm. An aqueous NaCl solution with a concentration of 2.0 wt% was installed in the filter evaluation device to generate NaCl particles with a number average particle size of 0.26 μm as test dust. Air containing the generated NaCl dust (dust concentration D1: 200 mg / m 3 ) was allowed to flow at a rate of 32 liters per minute through the measuring unit equipped with the filter for 60 minutes, and the dust concentration D1 on the upstream side and the dust concentration D2 on the downstream side (after filtration) were measured using a light scattering mass concentration meter.

[0212] When it was possible to measure up to a dust accumulation amount of 30 mg or more, at the moment when the dust accumulation amount reached 30 mg, the differential pressure (pressure loss) at a flow rate of 32 liters per minute was measured between the upstream and downstream sides of the measuring unit in the filter evaluation device using a differential pressure gauge.

[0213] When it was not possible to measure up to a dust accumulation amount of 30 mg, an approximate straight line was drawn through the pressure loss, and the value calculated by extrapolating the pressure loss at the moment when the dust accumulation amount reached 30 mg was adopted.

[0214] It should be noted that when the pressure loss could not be calculated by the above two methods, the maximum pressure loss in the measurement interval was adopted.

[0215] [Increase in pressure loss]

[0216] The increase in pressure loss was calculated as the difference between the pressure loss at 30 mg of accumulation (or equivalent value) and the initial pressure loss, which were used in the measurement of the pressure loss during the above-mentioned NaCl accumulation.

[0217] (Example 1)

[0218] It was manufactured using a general meltblown nonwoven fabric manufacturing device in the following manner. That is, polypropylene (melt flow rate 600 g / 10 minutes) was melted at 200 °C using an extruder and then ejected from a spinneret nozzle (spinneret) with 1300 spinning holes per meter (arranged in a single row) at a spinning temperature of 250 °C and a single-hole ejection amount of 0.1 g / hole·minute onto a flat net (manufactured by CONWED, trade name “R02659”, a polypropylene warp and weft orthogonally intersecting type with heat-sealed intersections, mesh size 18×28 mm, unit area weight 49 g / m 2, on an average fineness of 300 μm). Further, while ejecting polypropylene, hot air with a temperature of 260 °C and a pressure of 0.01 MPa was ejected from a slit provided near the spinneret holes to thin the ejected fibers, which were then collected on a mesh conveyor located 10 cm below the nozzle (spinneret), and a three-dimensional fiber structure was manufactured. The average fiber diameter of the non-woven fabric was 3.1 μm. It should be noted that the distance between the collection net and the suction device was 10 cm.

[0219] Next, for the obtained fiber structure, a charging treatment was carried out by the hydroelectret electrostatic method. Specifically, after spraying water onto the fiber structure under the following conditions, a slit-shaped suction nozzle was brought into contact with the surface of the fiber structure to suck water, thereby allowing the water to penetrate into the interior of the fiber structure. After removing the water, it was naturally dried.

[0220] · Water pressure: 0.2 Mpa

[0221] · Suction pressure: 2000 mmH2O

[0222] · Treatment time: 0.0084 seconds (speed 10 m / min)

[0223] In addition, for one protrusion of the fiber structure, a photograph obtained by photographing the cross-section in the thickness direction with a camera is shown in Figure 7 . It should be noted that it should be noted that the photograph directly shows a slightly distorted shape at the time of cutting when the cross-section of the fiber structure is exposed, so the actual depth D and height H are different from the measured values derived from the photograph.

[0224] Furthermore, the measurement results of the air permeability, capture efficiency, pressure loss, and QF value of the obtained electret are shown in Table 1.

[0225] (Example 2)

[0226] A fiber structure was manufactured in the same manner as in Example 1 except that the air pressure was set to 0.007 MPa and the distance between the nozzle (spinneret) and the collection net was set to 15 cm. The characteristics of the obtained fiber structure and electret are shown in Table 1.

[0227] (Example 3)

[0228] A fiber structure was manufactured in the same manner as in Example 1 except that the air pressure was set to 0.007 MPa and the distance between the nozzle (spinneret) and the collection net was set to 10 cm. The characteristics of the obtained fiber structure and electret are shown in Table 1.

[0229] (Example 4)

[0230] Except that the air pressure was set to 0.005 MPa and the distance between the nozzle (spinneret) and the collection net was set to 15 cm, the properties of the obtained fiber structure and electret are shown in Table 1.

[0231] (Example 5)

[0232] Except that the air pressure was set to 0.007 MPa and the distance between the nozzle (spinneret) and the collection net was set to 20 cm, a fiber structure was produced in the same manner as in Example 1. The properties of the obtained fiber structure and electret are shown in Table 1.

[0233] (Example 6)

[0234] Except that the air pressure was set to 0.006 MPa and the distance between the nozzle (spinneret) and the collection net was set to 20 cm, a fiber structure was produced in the same manner as in Example 1. The properties of the obtained fiber structure and electret are shown in Table 1.

[0235] (Example 7)

[0236] Except that the single-hole discharge amount was set to 0.2 g / hole·min, the air pressure was 0.012 MPa, and the distance between the nozzle (spinneret) and the collection net was set to 15 cm, a fiber structure was produced in the same manner as in Example 1. The properties of the obtained fiber structure and electret are shown in Table 1.

[0237] (Example 8)

[0238] Except that the single-hole discharge amount was set to 0.2 g / hole·min, the air pressure was 0.014 MPa, and the distance between the nozzle (spinneret) and the collection net was set to 15 cm, a fiber structure was produced in the same manner as in Example 1. The properties of the obtained fiber structure and electret are shown in Table 1.

[0239] (Example 9)

[0240] Except that the single-hole discharge amount was set to 0.2 g / hole·min, the air pressure was 0.014 MPa, and the distance between the nozzle (spinneret) and the collection net was set to 10 cm, a fiber structure was produced in the same manner as in Example 1. The properties of the obtained fiber structure and electret are shown in Table 1.

[0241] (Example 10)

[0242] Except that the flat net used as the collection net was changed to a polypropylene warp and weft orthogonally intersecting type intersection heat-sealed net (mesh size 36×28 mm, average fineness 300 μm), a fiber structure was produced in the same manner as in Example 1. The properties of the obtained fiber structure and electret are shown in Table 1.

[0243] (Example 11)

[0244] Except that the flat net used as the capture net was changed to a polypropylene warp and weft orthogonal intersection heat-sealing type (mesh size 36×20 mm, unit area weight 7 g / m 2 , average fiber fineness 100 μm), the fibrous structure was manufactured in the same manner as in Example 1. The properties of the obtained fibrous structure and electret are shown in Table 1.

[0245] (Comparative Example 1)

[0246] The collection was directly captured by the collector without using a flat net. The distance between the nozzle and the collector was 20 cm. Except for this, the fibrous structure was manufactured in the same manner as in Example 1. The properties of the obtained fibrous structure and electret are shown in Table 1.

[0247] (Comparative Example 2)

[0248] Except that the air pressure was set to 0.012 MPa and the distance between the nozzle (spinneret) and the capture net was set to 15 cm, the fibrous structure was manufactured in the same manner as in Example 1. The properties of the obtained fibrous structure and electret are shown in Table 1.

[0249] (Comparative Example 3)

[0250] Except that a flat net (manufactured by CONWED, trade name “R5340”, polypropylene warp and weft orthogonal intersection heat-sealing type, mesh size 6×6 mm, unit area weight 19 g / m 2 , average fiber fineness μm) was used, the air pressure was set to 0.007 MPa, and the distance between the nozzle (spinneret) and the capture net was set to 10 cm, the fibrous structure was manufactured in the same manner as in Example 1. The properties of the obtained fibrous structure and electret are shown in Table 1.

[0251]

[0252] As shown in Table 1, Examples 1 to 11 all used a capture net and had a three-dimensional shape with a cavity part of a given depth. Therefore, not only was the pressure loss low, but the QF value could also be increased. In addition, even in the state where 30 mg of NaCl had been accumulated, the increase in pressure loss could be suppressed, so the life of the filter could be extended.

[0253] In addition, as Figure 7 shown, when the fiber shape could be maintained at the base, it was considered that fine particles could also be captured at the bottom and the increase in pressure loss could be suppressed.

[0254] On the other hand, in Comparative Example 1, the collection was directly carried out in the collector without using a collection net, so it was not a three-dimensional shape but a simple planar fiber structure. The obtained fiber structure not only had a low air permeability but also a high pressure loss, and the QF value was also low. In addition, due to the high rate of increase in pressure loss, the life of the filter could not be extended.

[0255] In Comparative Example 2, the fiber aggregate that passed through the collection net quickly formed a bottom, so the depth of the cavity portion could not be increased. As a result, compared with the example, the pressure loss was still high and the QF value was also low. In addition, compared with the example, due to the high rate of increase in pressure loss, the life of the filter could not be extended.

[0256] In Comparative Example 3, by controlling the three-dimensional shape, the pressure loss was high and the QF value was also low. Since the depth of the cavity portion could not be increased, the increase in pressure loss could not be suppressed in the state where 30 mg of NaCl had already been accumulated. As a result, the life of the filter was shortened.

[0257] Industrial Applicability

[0258] The fiber structure of the present invention has a protruding portion with a given depth, so the protruding portion has a cavity portion with a sufficient depth. Therefore, due to its air permeability, three-dimensional shape, and large surface area, it can be used in various fields such as industrial, agricultural, and living materials, such as filters, wipers, separators, capacitors, condenser microphones, ultrasonic diagnostic transducers, cushioning materials, etc. In addition, it can also be used as a filter for filtration in which a given substance (such as granular materials such as coffee and activated carbon) is pre-filled in the cavity portion of the protruding portion.

[0259] In addition, due to the cavity portion having a given depth, especially a large surface area, it is excellent in the collection property of fine dust (particles) and its long life, so it can be used as various filters, liquid filters in the pharmaceutical industry, electronic industry, food industry, automotive industry, etc., filters in the household appliance field (such as air purifiers, air conditioners), industrial fields (such as bag filters, pre-filters, medium-performance filters (filters used for particle sizes of 0.4 - 0.7 μm, etc.)), and cabin filters for automobiles.

[0260] When used for the above-mentioned purposes, usually, in order to increase the surface area of the filter material, the filter is subjected to pleating processing. However, since this fiber structure can ensure the surface area of the filter material by forming a given cavity portion in the protruding portion, it can be used even without pleating processing.

[0261] As described above, the preferred embodiments of the present invention have been described, but various additions, changes, or deletions can be made without departing from the gist of the present invention, and such embodiments are also included within the scope of the present invention.

Claims

1. A fibrous structure having an opening portion and a protruding portion protruding from the opening portion, wherein the protruding portion has a side wall portion formed on the side surface and a bottom portion formed on the bottom surface, the depth (D) of the cavity portion present between the opening portion and the bottom portion in the protruding portion is 5 to 75 mm.

2. The fibrous structure according to claim 1, wherein The area B of the ideal cone calculated based on the depth (D) of the cavity part and the area (R) of the opening part is 550 to 8000 mm 2 .

3. The fibrous structure according to claim 1 or 2, wherein the ratio (B / R) of the area B of the ideal cone calculated based on the depth (D) of the cavity portion and the area (R) of the opening portion to the area (R) of the opening portion is 1.1 or more.

4. The fibrous structure according to any one of claims 1 to 3, wherein The average area (R) of the opening part is 200 mm 2 or more.

5. The fibrous structure according to any one of claims 1 to 4, wherein the ratio (Tb / Ta) of the thickness Tb of the bottom portion to the thickness Ta of the opening portion is 20 to 500.

6. The fibrous structure according to any one of claims 1 to 5, wherein the ratio (Tb / D) of the thickness Tb of the bottom portion to the depth D of the cavity portion is 2 or less.

7. The fibrous structure according to any one of claims 1 to 6, wherein the ratio (D / H) of the depth D of the void portion to the height H of the protruding portion is 0.35 to 0.

99.

8. The fibrous structure according to any one of claims 1 to 7, wherein the protruding portion is composed of a bulging portion.

9. The fibrous structure according to any one of claims 1 to 8, further comprising a support body composed of a wire body, and the opening portion is supported by the support body.

10. The fibrous structure according to any one of claims 1 to 9, which has a plurality of protrusions, and the number of protrusions per 10,000 mm 2 is 5 to 50 per 10,000 mm 2 .

11. A three-dimensional filter comprising: the fibrous structure according to any one of claims 1 to 10.

12. A filter for filtration, comprising: a module in which the end portion of the fibrous structure according to any one of claims 1 to 10 is fixed to a housing.

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