Fiber filter material, filtration method, and method for manufacturing fiber filter material

Abstract

To provide a fibrous filter material that exhibits excellent ability to capture solids, including fine particles with a particle size of 10 μm or less, from water to be treated, allows for precision filtration, and can be reused after washing; a filtration method using the same; and a method for manufacturing the fibrous filter material. [Solution] A fibrous filter material comprising a main fiber and a thermoplastic elastomer, wherein at least a portion of the fiber entanglement points of the main fiber are fixed by the thermoplastic elastomer, the fibrous filter material has a maximum length of 3 mm to 20 mm, and an apparent density of 0.02 g / cm³. 3 ~0.10 g / cm³ 3 It is a fibrous filter material.

Description

[Technical Field]

[0001] The present invention relates to a fibrous filter material suitable for filtering water, a filtration method, and a method for manufacturing a fibrous filter material. [Background technology]

[0002] As a filter material for water treatment, fibrous filter media have been developed and are being used as an alternative to sand filtration (see, for example, Patent Document 1).

[0003] While sand filtration can remove solid particles with a diameter of approximately 10 μm or larger, fiber filtration, which uses fiber media as the filter material, can remove solid particles with a diameter of 5 μm or larger. However, it cannot remove solid particles with a finer particle size, and in order to remove solid particles with a finer particle size, it is common to separate them using a microfiltration membrane. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 2672780 [Overview of the project] [Problems that the invention aims to solve]

[0005] The object of the present invention is to provide a fibrous filter material that is excellent at capturing solids, including fine particles with a particle size of 10 μm or less, from water to be treated, is capable of precision filtration, and can be reused after washing; a filtration method using the same; and a method for manufacturing the fibrous filter material. [Means for solving the problem]

[0006] As a result of diligent research to achieve the above objective, the inventors of the present invention discovered that even fibrous filter media, if certain requirements are met, can exhibit excellent collection of fine particles, enable precision filtration, and can be reused repeatedly after washing, thus arriving at the present invention. In more detail, the present invention provides excellent collection efficiency of impurity particles contained in water, including particles with a diameter of 10 μm or less, by compressing the filter media during filtration, enabling precise filtration. Furthermore, the filter media can be reused repeatedly as it recovers its shape during washing.

[0007] In other words, the present invention encompasses the following: <1> A fibrous filter material comprising a main fiber and a thermoplastic elastomer, wherein at least a portion of the fiber entanglement points of the main fiber are fixed by the thermoplastic elastomer, the fibrous filter material has a maximum length of 3 mm to 20 mm, and an apparent density of 0.02 g / cm³. 3 ~0.10 g / cm³ 3 It is a fibrous filter material. <2> The thermoplastic elastomer is a polyether polyester block copolymer, in which polybutylene terephthalate-based polyester is used as the hard segment and polyoxybutylene-based polyether is used as the soft segment. <1> The fiber filter material described above. <3> The compressibility at 20°C is 20% to 70%. <1> or <2> The fiber filter material described above. <4> For use in devices with a filtration mechanism <1> ~ <3> A fiber filter material listed in any one of the following. <5> The main fiber comprises short fibers with a fineness of 1 dtex to 4 dtex. <1> ~ <4> A fiber filter material listed in any one of the following. <6> Its shape is columnar. <1> ~ <5> A fiber filter material listed in any one of the following. <7> In a device having a filtration mechanism capable of filtration while maintaining the compaction state of the filter layer <1> ~ <6> A filtration method that uses a fibrous filter material described in any one of the following. <8> A method for manufacturing a fibrous filter medium comprising a main fiber and a thermoplastic elastomer, the method comprising the step of processing a sliver comprising the main fiber and the thermoplastic elastomer with a die at 100°C to 200°C. <9> The method for manufacturing a fibrous filter medium according to <8>, wherein the main fiber comprises short fibers having a fineness of 1 dtex to 4 dtex.

Advantages of the Invention

[0008] The fibrous filter medium of the present invention is excellent in collecting solids including solids having a fine particle size of 10 μm or less, can perform precision filtration, and can be repeatedly used by washing.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, the fibrous filter medium, the filtration method, and the method for manufacturing the fibrous filter medium will be described.

[0010] In this specification, a numerical range indicated using "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In a numerical range described stepwise in this specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other stepwise descriptions. In the numerical range described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. In this specification, the term "step" includes not only an independent step but also a step that cannot be clearly distinguished from other steps as long as the intended purpose of the step is achieved.

[0011] In this specification, the "fibrous filter medium" may sometimes be simply referred to as the "filter medium".

[0012] <Fibrous Filter Medium> The fibrous filter medium of the present invention is a fibrous filter medium containing main fibers and a thermoplastic elastomer, wherein at least a part of the fiber entanglement points of the main fibers are fixed by the thermoplastic elastomer, and the fibrous filter medium has a maximum length of 3 mm to 20 mm and an apparent density of 0.02 g / cm 3 ~0.10 g / cm 3 .

[0013] With the above configuration, it is excellent in the collection property of solids including solids with a particle size of 10 μm or less, can perform precision filtration, and can be repeatedly used by washing.

[0014] (Main fibers) The fibrous filter medium of the present invention contains main fibers. The main fibers preferably include polyester staple fibers.

[0015] The polyester staple fibers may be any of polyethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, polytrimethylene terephthalate, polycyclohexylene dimethylene terephthalate, polypivalolactone, or copolymers thereof. However, from the viewpoints of the elasticity and recovery of the finally obtained fibrous filter medium, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, or polycyclohexylene dimethylene terephthalate is preferable. The polyester staple fibers may be, for example, heat-adhesive composite fibers having polyethylene terephthalate as a core component and polyethylene or polypropylene arranged around it as a sheath component.

[0016] The fineness of the main fibers is preferably 1 dtex to 4 dtex, more preferably 1.2 dtex to 3.6 dtex, still more preferably 1.5 dtex to 3.2 dtex, and particularly preferably 1.6 dtex to 3 dtex from the viewpoints of improving the filtration performance and the collection property of fine particles. When the fineness of the main fibers is within this range, it is easy to achieve the compression characteristics required for a fibrous filter medium for precision filtration.

[0017] The length of the main fibers is preferably 30mm to 100mm, more preferably 40mm to 70mm, and even more preferably 50mm to 60mm, from the viewpoint of increasing the number of fiber entanglement points between the main fibers and improving the strength and durability of the fiber filter material.

[0018] The ratio of fineness to length (mm / dtex) of the main fiber is preferably 5 to 100, more preferably 10 to 50, and even more preferably 15 to 25.

[0019] When the ratio of fineness to length (mm / dtex) of the main fibers is 5 or higher, filtration performance tends to improve, and the number of fiber entanglement points between the main fibers increases, which tends to improve the strength and durability of the fiber filter media. On the other hand, the ratio of fineness to length (mm / dtex) of the main fiber is 100 or less, making it easier to procure the main fiber.

[0020] In the fibrous filter media of the present invention, the content of the main fiber is preferably 20% to 90% by mass, and more preferably 30% to 70% by mass, based on the total mass of the fibrous filter media. When the content of the main fiber is within this range, the main fiber can effectively exhibit its properties in the fibrous filter media, and the fibrous filter media is likely to achieve the desired properties.

[0021] The specific gravity of the main fiber is preferably in the range of 1.1 to 2. Since the specific gravity of water is 1, it sinks in water during use, improving filtration and washing efficiency (note that the specific gravity of polyethylene terephthalate resin is 1.38).

[0022] The melting point of the main fiber is preferably between 180°C and 280°C.

[0023] (Thermoplastic elastomer) The fibrous filter material of the present invention contains a thermoplastic elastomer.

[0024] In the present invention, a polyether polyester block copolymer is preferred as the thermoplastic elastomer, wherein polyester is used as the hard segment and poly(alkylene oxide) glycol is used as the soft segment, and a polyether polyester block copolymer is particularly preferred, wherein polybutylene terephthalate polyester is used as the hard segment and polyoxybutylene polyether is used as the soft segment.

[0025] In addition to the examples given above, examples of hard segments of the polyether polyester block copolymer include polyesters composed of at least one dicarboxylic acid selected from aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, diphenoxyethanedicarboxylic acid, and sodium 5-sulfisophthalate; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid; and aliphatic dicarboxylic acids such as succinic acid, oxalic acid, adipic acid, sebacic acid, dodecanoic acid, and dimer acid; and at least one diol component selected from aliphatic diols such as ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentyl glycol, and decamethylene glycol, or alicyclic diols such as 1,1-cyclohexanedimethanol and tricyclodecanedimethanol.

[0026] Furthermore, examples of poly(alkylene oxide) glycols with an average molecular weight of 400 to 5000 include polyethylene glycol, poly(1,2-propylene oxide) glycol, poly(tetramethylene oxide) glycol, poly(trimethylene oxide) glycol, copolymer of ethylene oxide and propylene oxide, and copolymer of ethylene oxide and tetrahydrofuran.

[0027] A polyether polyester block copolymer is also suitable, in which the hard segment is a polyester whose main acid components are 40-100 mol% terephthalic acid and 0-50 mol% isophthalic acid, the main glycol component is 1,4-butanediol, and the main soft segment component is a poly(alkylene oxide) glycol with an average molecular weight of 400-5000, and the copolymerization ratio (mass ratio) of the hard segment component to the soft segment component is 95:5-20:80 mass%.

[0028] In the fibrous filter material of the present invention, the thermoplastic elastomer is preferably included in the heat-adhesive composite fiber. It is even more preferable that the thermoplastic elastomer is included as a sheath component in the heat-adhesive composite fiber.

[0029] The heat-adhesive composite fiber is preferably composed of the main fiber and the thermoplastic elastomer in a fiber cross-section with an area ratio of 20:80 to 80:20. The composite state of the two components may be any known composite state, such as core-sheath type, eccentric core-sheath type, parallel (side-by-side) type, sea-island type composite spun fiber or sea-island type mixed spun fiber, or mandarin orange segment type coordination (split) fiber, but it is preferable that a portion of the thermoplastic elastomer is exposed on the fiber surface, preferably so that the thermoplastic elastomer occupies 30% or more of the circumference in the fiber cross-section. In particular, the parallel type, core-sheath type, and eccentric core-sheath type are preferable because they allow for easy impartment of latent crimping ability, where fine crimping becomes apparent during heat treatment when forming the fiber structure, thereby increasing the entanglement between fibers and improving adhesion.

[0030] Furthermore, the shape of the fiber cross-section does not need to be a perfect circle; polygonal, finned, or lumpy shapes are acceptable. However, considering the case where short fibers are formed and passed through the carding process, a perfect circle shape is preferable. It may also have one or more hollow sections. Furthermore, heat-adhesive composite fibers can be manufactured using conventionally known methods.

[0031] When a thermoplastic elastomer is included in the heat-adhesive composite fiber, the fineness of the heat-adhesive composite fiber is preferably 12 dtex or less, and more preferably 4 dtex to 8 dtex.

[0032] By setting the fineness of the heat-adhesive composite fibers within the above range, when the thermoplastic elastomer is melted to form a fiber filter material, the number of fixed (adhered) fiber entanglement points formed in the fiber filter material becomes appropriate, resulting in sufficient strength. Furthermore, it is preferable that the adhesion phenomenon between the heat-adhesive composite fibers during the manufacturing process is also suppressed.

[0033] When a thermoplastic elastomer is included in the heat-adhesive composite fiber, the length of the heat-adhesive composite fiber when cut into short fibers is preferably 30 mm to 100 mm, and more preferably 40 mm to 80 mm. Within this range, carding properties and adhesion of the fiber structure are particularly good.

[0034] When thermoplastic elastomers are included in heat-adhesive composite fibers, the content of thermoplastic elastomers is preferably 30% to 80% by mass, based on the total mass of the heat-adhesive composite fibers.

[0035] When a thermoplastic elastomer is included as a sheath component in a heat-adhesive composite fiber, the content of the thermoplastic elastomer as a sheath component is preferably 30% to 80% by mass, based on the total mass of the heat-adhesive composite fiber (core-sheath component).

[0036] The melting point of the thermoplastic elastomer is preferably 120°C to 200°C, more preferably 130°C to 180°C, and even more preferably 150°C to 160°C.

[0037] If the melting point of the thermoplastic elastomer is within the above range, the adhesion points described later are less likely to be destroyed and are more likely to be maintained even when the water to be filtered is at a high temperature, and adhesion point unevenness during the manufacturing of the fiber filter material is also more easily suppressed.

[0038] In the fiber filter medium of the present invention, the content of the thermoplastic elastomer is preferably 15% by mass to 70% by mass, more preferably 20% by mass to 40% by mass, based on the total mass of the fiber filter medium.

[0039] As already described, the fiber filter medium of the present invention includes main fibers and a thermoplastic elastomer. In the fiber filter medium of the present invention, the main fibers have a plurality of fiber entanglement points among the main fibers inside the main fiber aggregate. In the fiber filter medium of the present invention, at least a part of the fiber entanglement points of the main fibers are fixed by the thermoplastic elastomer. Since the fiber entanglement points are fixed by the thermoplastic elastomer, the aggregate form can be maintained without dispersing the main fibers.

[0040] [[ID=I4]](Physical property values of the fiber filter medium, etc.) -Apparent density- The apparent density of the fiber filter medium of the present invention is 0.02 g / cm 3 to 0.1 g / cm 3 . If the apparent density of the fiber filter medium is less than 0.02 g / cm 3 , there is a problem that the filter medium after washing remains greatly crushed and is difficult to recover. On the other hand, if the apparent density exceeds 0.1 g / cm 3 , the compression rate decreases and the filter medium becomes hard, resulting in a problem that the filtration performance decreases. The apparent density of the fiber filter medium is determined by the method described in the examples.

[0041] -Bulk density- The bulk density of the fiber filter medium of the present invention is preferably not less than 15 kg / m 3 and less than 60 kg / m 3 . The bulk density of the fiber filter medium is the bulk density when the fiber filter medium is filled in the filtration device, and is determined by the method described in the examples.

[0042] -SS removal rate- From the viewpoint of contributing to precision filtration, the SS removal rate of the fibrous filter media of the present invention is preferably 86% or higher, more preferably 88% or higher, and even more preferably 90% or higher. The SS removal rate of the fibrous filter media can be determined by the method described in the examples.

[0043] -FI value- The FI value of the fiber filter material of the present invention is preferably such that the FI value (Fouling Index) of the filtrate after filtration is 5 or less, and more preferably 4 or less. This FI value, also known as the SDI (Silt Density Index) value, is an index defined in JIS K 3802 and the US ASTM D4189. While typically used in reverse osmosis to quantify trace amounts of suspended solids in the water supplied to the module, it is also widely used as an indirect indicator of the amount of suspended solids present in relatively clear water. The FI value was measured by filtering 500 ml of sample water at 206 kPa using a 47 mm diameter, 0.45 μm filter, and measuring the time required to obtain 500 ml of filtrate from the start of filtration (f0) and the time required to obtain the same amount of filtrate 15 minutes after the start of filtration (f 15 ) is calculated using the following formula. FI value = (1 - f0 / f 15 ) × 100 / 15)

[0044] A Fouling Index (FI) of 5 or less suggests that particles and polymers in the range of 0.1 to 10 μm can be separated, contributing to microfiltration.

[0045] -Tensile Strength- The tensile strength of the fiber filter material of the present invention is preferably 0.4 N / cm or more, more preferably 1.5 N / cm or more, and even more preferably 2 N / cm or more, at a tensile speed of 5 mm / min and a gripping distance of 2 mm. Having the above-mentioned tensile strength of the fiber filter material ensures sufficient strength and durability.

[0046] -Compression ratio- The fibrous filter media of the present invention preferably has a compressibility of 20% to 70% at 20°C. A compressibility within this range at 20°C has the advantage of improving filtration performance because the filter media is compressed during use, reducing inter-filter media voids and internal filter media voids. From this viewpoint, the compressibility of the fibrous filter media at 20°C is more preferably 40% or more, and even more preferably 50% or more. The compressibility at 20°C can be determined by the method described in the examples.

[0047] - Repeated Compression Ratio - The fibrous filter media of the present invention preferably has an initial compressibility of 20% to 70% at 20°C, and a repeated compressibility of 50% or more, particularly 55% to 65%, up to the 5th cycle at 20°C. When the repeated compressibility is within this range, the filter media is compressed during use, reducing the inter-filter media voids and internal filter media voids, which has the advantage of improving filtration performance. The repeated compressibility can be determined by the method described in the examples.

[0048] -Recovery rate- The fiber filter media of the present invention preferably has a recovery rate of 10% or more after the fifth repeated compression at 20°C. Furthermore, it is preferable that the compression rate after the fifth repeated compression is 55% to 65%, and the recovery rate of the filter media at that time is 10% or more, particularly 12% to 20%. For example, when the compression rate is 60% and the recovery rate is 16%, the actual filter media, which was compressed to the initial 40%, recovers to 56%, meaning it has recovered by 40% ((56% / 40%)-1) compared to immediately after compression. Within this range, the recovery of the filter media after washing is high, so even if washing is repeated, the filtration performance can be maintained and the lifespan of the filter media can be improved.

[0049] -Shape, etc.- The fibrous filter media of the present invention must have a maximum length of 3 to 20 mm. If the maximum length of the fibrous filter media is less than 3 mm, leakage from the filtration tank is likely to occur. If the length of the fibrous filter media exceeds 20 mm, the gaps between the fibrous media become larger, and the filtration performance deteriorates. In this specification, "maximum length" refers to the diameter of the bounding ball (smallest enclosing ball) that has the smallest volume and is in contact with the fibrous filter media. For example, if the fibrous filter media is cylindrical, the diameter of the circumscribed circle tangent to the rectangle obtained by cutting perpendicularly through the center of the circle coincides with the diameter of the bounding ball and the smallest enclosing ball. Therefore, the length of the diagonal of that rectangular cross-section is taken as the maximum length of the fibrous filter media. The fibrous filter material of the present invention is preferably columnar, and more preferably cylindrical or rectangular. The cross-sectional shape of the fibrous filter material is preferably circular or rectangular. Furthermore, it is preferable that all of the fibrous filter material pieces have the same shape.

[0050] When the fibrous filter material of the present invention is cylindrical or rectangular prism-shaped, the diameter of the circle or circumscribed circle in the cross-section of the fibrous filter material is preferably 3 mm to 20 mm, more preferably 4 mm to 16 mm, and even more preferably 5 mm to 12 mm.

[0051] When the fibrous filter media of the present invention is cylindrical or rectangular prism-shaped, the length of the fibrous filter media is preferably 3 mm to 18 mm in the longitudinal direction. Furthermore, the length of the fibrous filter media is preferably 4 mm to 12 mm in the longitudinal direction, and more preferably 5 mm to 9 mm in the longitudinal direction. If the length of the fibrous filter media is less than 3 mm in the longitudinal direction, outflow from the filtration tank is likely to occur. If the length of the fibrous filter media exceeds 18 mm in the longitudinal direction, the gaps between the fibrous filter media become larger, and the filtration performance decreases. Here, length refers to the length in the longitudinal direction of the columnar object when an intermediate body, such as a sliver shape, is cut or otherwise processed.

[0052] (Uses of fiber filter media) The fibrous filter material of the present invention may be used in a device having a filtration mechanism. Examples of devices having a filtration mechanism include, but are not limited to, those equipped with a raw liquid tank, a booster pump, a filtrate tank, a backwash pump, etc.

[0053] <Filtration Method> The filtration method of the present invention is a method of filtration using the above-mentioned fibrous filter material in a device having a filtration mechanism capable of filtration while maintaining the compacted state of the filter layer.

[0054] One method for maintaining the compacted state of the filter bed is to fill the fibrous filter material of the present invention into a device having a filtration mechanism capable of filtration, and to pre-pressure and compress the filter bed with a booster pump before the filtration process. As for the filtration method, the fibrous filter material of the present invention may be filled into a filtration device, and the liquid to be treated may be passed through from top to bottom to perform the filtration process. Furthermore, if a wire mesh or similar is installed above or below the filter media in the filtration tower, and the height of the filter layer is fixed during filtration, the filtration process may be performed by passing the liquid to be treated from below the filter media upwards.

[0055] Furthermore, filtration performance can be confirmed by the SS removal rate. A SS removal rate of 86% or higher is preferable.

[0056] <Method for manufacturing fiber filter media> The present invention relates to a method for producing a fibrous filter material comprising a main fiber and a thermoplastic elastomer, and includes a step of processing a sliver comprising the main fiber and the thermoplastic elastomer with a die at 100°C to 200°C.

[0057] By including the above steps, the fibrous filter material of the present invention can be obtained.

[0058] The fibrous filter material of the present invention is obtained by forming thermal bonding points within the fibrous filter material at least a portion of the contact points between the main fibers and the heat-adhesive composite fibers (short fibers) containing a thermoplastic elastomer, and / or the contact points between the heat-adhesive composite fibers containing a thermoplastic elastomer. For example, it can be obtained by blow molding into a specific mold and then heat treatment. Specifically, it is obtained by first preparing a sliver containing a main fiber and a thermoplastic elastomer, and then processing the sliver with a die at 100°C to 200°C.

[0059] The processing temperature of the sliver described above (100°C to 200°C) is above the melting point of the thermoplastic elastomer used, but below the melting point of the main fibers. By keeping the processing temperature of the sliver within this range, the fiber entanglement points between the main fibers adhere sufficiently, and the desired fiber filter material can be obtained.

[0060] The processing time for the sliver is preferably 10 to 100 seconds, and more preferably 20 to 50 seconds.

[0061] The sliver may be processed only once or multiple times. When processing multiple times, it is preferable to gradually reduce the diameter of the nozzle.

[0062] The mass per unit length of the sliver before processing is preferably 0.3 g / m to 20 g / m, more preferably 0.4 g / m to 8 g / m, and even more preferably 0.5 g / m to 2.5 g / m.

[0063] The diameter of the die during processing is preferably 3mm to 50mm, and from the viewpoint of heat transfer to the sliver, 5.5mm to 9.5mm is particularly preferred.

[0064] The length of the jaw during processing is preferably between 5mm and 200mm. [Examples]

[0065] The present invention will be described in detail below with reference to examples. The melting points in the examples were analyzed by DSC. Furthermore, the physical properties of the filter material were determined according to the following methods.

[0066] -Apparent Density- For each of the 10 columnar filter media, measure the diameter, length, and weight, and measure 1 cm for each filter media. 3 The mass per unit was calculated, and the average value was determined.

[0067] -Bulk density- A graduated cylinder with an inner diameter of 80 mm and a volume of 2 L was filled with filter media up to the 1 L mark, and its weight was determined to calculate the mass per unit volume of filter media. When filling the graduated cylinder with filter media, the filter media was added while vibrating to reduce the gaps between the media, and the container was struck against the surface at least 10 times until the change in the filled volume of filter media was no longer visible before measurement.

[0068] -SS removal rate- The SS concentrations in the raw water and the filtered treated water were determined using the method described in JIS K 0102 14.1 Suspended Solids. The SS removal rate (%) was calculated by dividing the difference between the raw water SS concentration and the treated water SS concentration by the raw water SS concentration. SS (Suspended Solids) refers to "suspended substances" as defined in JIS K 0102, which are insoluble substances suspended in water.

[0069] -FI value- The filtered sample water was filtered using a 47 mm diameter, 0.45 μm filter at a pressure of 206 kPa. The time required to obtain 500 ml of filtrate from the start of the initial filtration (f0) and the time required to obtain the same amount of 500 ml of filtrate after continuing filtration under the same conditions for 15 minutes (f) were measured. 15 ) was calculated using the following formula. FI value = (1 - f0 / f 15 ) × 100 / 15

[0070] -Fiber shedding rate- The initial amount of fibrous filter media placed in the filtration tower was set to 100. After each wash cycle, the fibers detached from the filter media were collected using a net with a 10 μm mesh size, and the percentage of the collected fiber weight was calculated. For subsequent wash cycles, the percentage is calculated by accumulating the weight of fibers detached from the first wash cycle to the total fiber weight.

[0071] -Tensile Strength- The sides of a columnar filter medium were clamped with a flat plate chuck with a gripping distance of 2 mm, and the tensile strength (N / m) was measured under the condition of a tensile speed of 5 mm / min.

[0072] -Compression ratio- The following measurements were taken at 20°C. A cylindrical filter tower with a diameter of 100 mm was filled with filter media to a height of 310 mm. The difference between the filter media filling height before applying the load and the filter media filling height after applying a load by placing a 16 kg weight on it and waiting 5 minutes was defined as the compression amount. The compression ratio (a higher value indicates greater compression) was calculated by dividing this compression amount by the filter media filling height before applying the load.

[0073] -Repeated compression ratio of filter media- The compression ratio of the filter media described above was defined as the initial compression ratio, and the compression ratio after repeating the same test multiple times was defined as the "repeated compression ratio" of the filter media.

[0074] -Recovery rate of filter media- After measuring the compression ratio of the filter media for each measurement, the weight was removed, and the recovery rate (the larger the value, the more it recovered to its original height) was calculated by dividing the difference between the filter media's filling height after 10 minutes and the filling height immediately after each compression ratio measurement by the filter media's filling height before the load was applied. The recovery rate after the first test was defined as the initial recovery rate, and the recovery rate after repeating the same test multiple times was defined as the "recovery rate after the 〇th test" for the filter media. The denominator, "filling height of the filter media before applying load," was always the "filling height of the filter media before applying load for the first time." The recovery rate of the filter media was measured up to the 5th test.

[0075] -Visual inspection of the filter media shape after filtration- After filtration, the filter media were classified into three categories based on their cross-sectional shape: those with almost no change, those compressed and deformed by 20% to 40% of volume without returning to their original shape, and those compressed and deformed by 50% or more of volume without returning to their original shape. The changes in the shape of each filter media were then visually inspected.

[0076] <Example 1> -Preparing the filter media- As the main fiber, polyethylene terephthalate fibers (short fibers) with a fineness of 2.1 dtex, a length of 51 mm, and a melting point of 253°C were prepared at a concentration of 40% by mass based on the total mass of the filter material. As a heat-adhesive composite fiber, a core-sheath type composite polyester fiber was prepared, comprising polyethylene terephthalate in the core and thermoplastic elastomer in the sheath portion at a density of 40% by mass relative to the total mass of the heat-adhesive composite fiber, with a fineness of 6.6 dtex, a length of 64 mm, and a melting point of the sheath portion of 154°C. This fiber was prepared at a density of 60% by mass relative to the total mass of the filter material. The main fibers and heat-adhesive composite fibers were blended using a cotton blending method to obtain a sliver weighing 0.7 g per meter. The molded sliver was heat-treated at 183°C for 30 seconds, then passed through a die with a diameter of 8.5 mm and a length of 80 mm, and then through another die with a diameter of 6 mm and a length of 80 mm, to obtain a molded fiber bundle with an average diameter of 7 mm. (Note that lowering the processing temperature in this step will result in a softer material.) The resulting molded fiber bundle was cut to a length of 7.5 mm to obtain cylindrical water treatment filter media with a maximum length of 10.3 mm. The apparent density of the resulting filter media was 0.09 g / cm³. 3 The bulk density of the filter media is 26.6 kg / m³. 3 The lateral tensile strength of the filter material at a tensile speed of 5 mm / min and a gripping distance of 2 mm was 2.3 N / cm. The thermoplastic elastomer content of the filter material was 24% by mass.

[0077] -Evaluation of precision filtration performance- (SS removal rate) 188 kg of filter media was stacked in a 3,000 mm diameter filtration tower so that the filter media filling height was 1,000 mm. The bulk density of the filter media in the filtration tower at this time was 26.6 kg / m³. 3 That was the case. The material was further compressed to 800 mm, and the filtration performance was evaluated based on the SS removal rate when seawater was used as the raw water and passed through in a downward flow at a filtration speed of LV40 m / h. The filtration test was conducted for 6 hours. The results are shown in Table 2. As shown in Table 2, the average raw water SS concentration when seawater was used as the raw water source was 3.4 mg / L. The SS removal rate averaged 91%, demonstrating high SS removal performance and indicating high filtration performance as a filter media for microfiltration. (Incidentally, according to the Journal of the Japan Society for Marine Surveys and Technology, 24(2), pp. 1-10, September 2012, the measured particle size in seawater ranged from 2 to 460 μm, demonstrating that the fibrous filter media of the present invention, capable of removing 91% of suspended solids (SS) from seawater, can be used as a microfiltration filter media as an alternative to microfiltration membranes.) After a 6-hour filtration test, the filtration evaluation was continued under the same conditions for up to 25 days. Basically, washing was performed once a day, and when the pressure loss reached 9 kPa, an additional wash was performed, the washing for that day was omitted, and daily washing resumed from the following day. The SS removal rate remained stable over 25 days, averaging 94.4%. Furthermore, even with daily cleaning and continued filtration, the filter media did not deteriorate, the SS removal rate remained high, and the filtration performance was maintained. After further evaluation for another 760 days, it was confirmed that the SS removal rate remained stable at 90%.

[0078] (FI value) 18.8 kg of filter media was stacked in a 300 mm diameter filtration tower to a packing height of 1,000 mm. The bulk density of the filter media in the filtration tower at this time was 26.6 kg / m³. 3 The sample was then compressed to 800 mm, and the filtered water was collected when seawater was used as the raw water and passed through it in a downward flow at a filtration rate of LV40 m / h. The FI value was then measured. The filtration test was conducted daily for 22 days. The results are shown in Table 2. As shown in Table 2, the average FI value of the raw water when seawater was used as the raw water was 6.4. The FI value on day 2 of filtration was 3.9, the FI value on day 12 of filtration was 3.9, and the FI value on day 22 of filtration was 3.6. The average FI value over 22 days was 3.8, and the FI value was 5 or less, confirming that this filter media was performing precise filtration.

[0079] -Durability evaluation- 7.5 kg of filter media were stacked in a 600 mm diameter filtration tower to a packing height of 1,000 mm. The durability of the filter media was confirmed by repeating a 10-minute filtration, 10-minute filter media washing, and 2-minute water discard cycle and measuring the weight of the detached fibers during the discard water. The filtration speed was LV60 m / h, the washing speed was LV35 m / h, and washing was performed with air agitation at an air volume of 90 Nm³. 3 / m 2 The test was performed using the / h command. The results are shown in Table 3. As shown in Table 3, the fiber shedding rate was 0.05% after 60 washes, 0.09% after 200 washes, 0.12% after 450 washes, and 0.51% after 1840 washes, which are very good results, and the filtration performance remained high even after 1840 washes.

[0080] -Evaluation of compressibility- 64.8g of dry filter media at 20°C was placed in a compression test apparatus with a diameter of 100mm and a height of 310mm. A 16kg weight was placed on top to apply a filtration pressure of 20kPa, similar to that of an actual filter in operation, and the filter bed was compressed. The compression ratio was checked after 5 minutes. The results are shown in Table 3. As shown in Table 3, the compressibility after 5 minutes under a 16 kg load was 62.3%, indicating high compressibility.

[0081] -Evaluation of repeated compressibility and resilience- 64.8g of dry filter media at 20°C was placed in a compression test apparatus with a diameter of 100mm and a height of 310mm. A load of 16kg was applied to compress the filter bed, and the compression ratio after 5 minutes was taken as the initial compression ratio. This was repeated 5 times, and the repeated compression ratios up to the 5th time were confirmed. In each compression ratio measurement, the weight was removed after the compression ratio measurement, and the recovery ratio was calculated by dividing the difference between the filter media filling height after 10 minutes and the filter media filling height after the compression ratio measurement by the filter media filling height before the load was applied. The recovery rate for subsequent compressions was calculated by, for example, determining the recovery rate after the second compression by dividing the difference between the filter media filling height after the second compression, 10 minutes after removing the weight, and the filter media filling height after the second compression by the filter media filling height before the first load was applied. The recovery rate after the third compression was calculated by dividing the difference between the filter media filling height 10 minutes after the third compression (after removing the weight) and the filter media filling height after the third compression by the filter media filling height before the first load was applied. In this way, the recovery rate of the filter media was checked up to the fifth time. The results are shown in Table 3.

[0082] As shown in Table 3, the compressibility after 5 minutes with a 16kg load was 62.3%, indicating high compressibility. The compressibility after the second compression was 60.9%, the third 62.0%, the fourth 62.3%, and the fifth 62.5%. Furthermore, the recovery rate after the first compression was 19.5%, the second 17.3%, the third 16.2%, the fourth 15.3%, and the fifth 14.8%, indicating high recovery of the filter media after washing. Even with repeated washing, the filtration performance with a high SS removal rate can be maintained, improving the lifespan of the filter media.

[0083] -Visual inspection of the filter media shape after filtration- After filtration, the filter media were classified into three categories based on their cross-sectional shape: those with almost no change, those compressed and deformed by 20% to 40% of volume and not returning to their original shape, and those compressed and deformed by 50% or more of volume and not returning to their original shape. The shape changes were visually inspected. The results are shown in Table 3. As shown in Table 3, after 23 days of filtration, 60% of the filter media showed almost no change in cross-sectional shape, 40% were compressed and deformed by 20% to 40% of the volume and did not return to their original shape, and 0% were compressed and deformed by 50% or more of the volume and did not return to their original shape.

[0084] <Comparative Example 1> -Preparing the filter media- As the main fiber, polyethylene terephthalate fibers (short fibers) with a fineness of 2.1 dtex, a length of 51 mm, and a melting point of 253°C were prepared at a concentration of 40% by mass based on the total mass of the filter material. As a heat-adhesive composite fiber, a core-sheath type composite polyester fiber was prepared, comprising polyethylene terephthalate in the core and thermoplastic elastomer in the sheath portion at a density of 40% by mass relative to the total mass of the heat-adhesive composite fiber, with a fineness of 6.6 dtex, a length of 64 mm, and a melting point of the sheath portion of 154°C. This fiber was prepared at a density of 60% by mass relative to the total mass of the filter material. The main fibers and heat-adhesive composite fibers were blended using cotton batting to obtain a sliver weighing 0.8 g per meter. The molded sliver was then heat-treated at 180°C for 23 seconds, and then passed through a die with a diameter of 10 mm and a length of 80 mm, and again through another die with a diameter of 10 mm and a length of 80 mm to obtain a molded fiber bundle with an average diameter of 10 mm. The resulting molded fiber bundle was cut to a length of 20 mm, yielding filter media with a maximum length of 22 mm. The apparent density of the filter media is 0.09 g / cm³. 3 The bulk density is 33.2 kg / m³. 3 (It is presumed that the bulk density increased because the filter material was soft and flexible.) The tensile strength of the obtained filter material at a tensile speed of 5 mm / min and a gripping distance of 2 mm was 4.1 N / cm. The thermoplastic elastomer content in the filter material was 24% by weight.

[0085] -Evaluation of precision filtration performance- 2.82 kg of filter media was stacked in a filtration tower made of straight pipes with a diameter of 300 mm and a length of 2,250 mm, so that the filter media filling height was 1,200 mm. A filtration test was conducted using seawater with a SS concentration of 2.7 mg / L, flowing it downwards for 5 hours. The results are shown in Table 2. As shown in Table 2, the average SS removal rate was 63.0% at a filtration rate of LV40 m / h and 70.4% at LV80 m / h. The pressure loss remained almost constant at approximately 3 kPa during the test in both cases of LV40 m / h and LV80 m / h. It is thought that the large voids between the filter media prevented the removal of SS.

[0086] -Evaluation of compressibility- 80.8 g of dry filter media at 20°C was placed in a compression test apparatus with a diameter of 100 mm and a height of 310 mm. A load of 16 kg was applied to compress the filter bed, and the compression ratio was checked after 5 minutes. The results are shown in Table 3. As shown in Table 3, the compressibility after 5 minutes with a 16 kg load was 68.1%, indicating high compressibility.

[0087] - Assessment of recovery - After measuring the initial compression ratio and removing the weight, the initial recovery rate, calculated by dividing the filter media filling height after 10 minutes by the filter media filling height before applying the load, was a low 16.9% (see Table 3).

[0088] <Comparative Example 2> -Preparing the filter media- As the main fiber, polyethylene terephthalate fibers (short fibers) with a fineness of 2.1 dtex, a length of 51 mm, and a melting point of 253°C were prepared at a concentration of 40% by mass based on the total mass of the filter material. As a heat-adhesive composite fiber, a core-sheath type composite polyester fiber was prepared, comprising polyethylene terephthalate in the core and thermoplastic elastomer in the sheath portion at a density of 40% by mass relative to the total mass of the heat-adhesive composite fiber, with a fineness of 6.6 dtex, a length of 64 mm, and a melting point of the sheath portion of 154°C. This fiber was prepared at a density of 60% by mass relative to the total mass of the filter material. The main fibers and heat-adhesive composite fibers were mixed and molded, and the sliver feeding speed was varied to obtain 10g of sliver per meter. After that, the molded sliver was heat-treated at 200°C for 14 seconds, then passed through a die with a diameter of 10mm and a length of 80mm, and then through another die with a diameter of 8.5mm and a length of 160mm to obtain a molded fiber bundle with a diameter of 9mm. The resulting molded fiber bundle was cut to a length of 15 mm, yielding filter media with a maximum length of 17.5 mm. The apparent density of the filter media is 0.12 g / cm³. 3 The bulk density is 40 kg / m³. 3 The obtained filter material had a tensile strength of 13 N / cm per 2 mm gripping distance at a tensile speed of 5 mm / min. The thermoplastic elastomer content in the filter material was 24% by mass.

[0089] -Evaluation of precision filtration performance- 0.31 kg of filter media was stacked in a 100 mm diameter filtration tower to a packing height of 1,000 mm. Using a solution of Showa Chemical Industry's Radiolite #100 dissolved at 14 mg per liter of industrial water as the raw water, the filtration performance was evaluated from the SS removal rate when water was passed through in a downward flow at a filtration speed of LV40 m / h. The results are shown in Table 2. As shown in Table 2, the filtration test was conducted for 5 hours, and the average SS removal rate was 50%, which could not be considered high for use as a filter media for precision filtration.

[0090] -Evaluation of compressibility- 97.4 g of dry filter media at 20°C was placed in a compression test apparatus with a diameter of 100 mm and a height of 310 mm. A load of 16 kg was applied to compress the filter bed, and the compression ratio was checked after 5 minutes. The results are shown in Table 3. As shown in Table 3, the compressibility after 5 minutes under a 16 kg load was 32.4%, indicating low compressibility. Furthermore, when the main fiber was changed to 7.7 dtex and 32 mm in length, the same test was conducted, and the compressibility of the filter media was 47.0%.

[0091] - Assessment of recovery - After measuring the initial compression ratio and removing the weight, the initial recovery rate, calculated by dividing the difference between the filter media filling height after 10 minutes and the filter media filling height after compression by the "filter media filling height before load application," was 9.6%. Furthermore, when the main fiber was changed to 7.7 dtex and 32 mm and the same test was conducted, the filter media recovery rate was 19.1%.

[0092] <Comparative Example 3> -Preparing the filter media- As the main fiber, polyethylene terephthalate fibers (short fibers) with a fineness of 2.1 dtex, a length of 51 mm, and a melting point of 253°C were prepared at a concentration of 40% by mass based on the total mass of the filter material. As a heat-bondable composite fiber, a core-sheath type composite polyester fiber was prepared, comprising polyethylene terephthalate in the core and thermoplastic elastomer in the sheath portion at a ratio of 40% by mass relative to the heat-bondable composite fiber, with a fineness of 6.6 dtex, a length of 64 mm, and a melting point of the sheath portion of 154°C. This fiber was prepared at a ratio of 60% by mass relative to the total mass of the filter material. The main fibers and heat-adhesive composite fibers were blended using cotton batting to obtain a sliver with a mass of 3.4 g per meter. After that, the molded sliver was heat-treated at 160°C for 30 seconds, and then passed through a die with a diameter of 10 mm and a length of 160 mm to obtain a molded fiber bundle with an average diameter of 9 mm. The resulting molded fiber bundle was cut to a length of 15 mm, yielding filter media with a maximum length of 17.5 mm. The apparent density of the filter media is 0.11 g / cm³. 3 The bulk density is 32.9 kg / m³. 3 The obtained filter material had a tensile strength of 6.8 N / cm per 2 mm gripping distance at a tensile speed of 5 mm / min. The thermoplastic elastomer content in the filter material was 24% by mass.

[0093] -Evaluation of precision filtration performance- 3.6 kg of filter media was stacked in a filtration tower consisting of a straight pipe with a diameter of 300 mm and a length of 2,250 mm, so that the filter media was packed to a height of 1,000 mm. Water was then passed through the tower at a filtration rate of LV135 m / h for approximately 5 minutes to compress the filter layer to 560 mm. After that, seawater was passed through the tower in a downward flow at a filtration rate of LV40 m / h, and the filtration performance was evaluated based on the SS removal rate and pressure loss. The filtration test was conducted for 48 hours. The average SS concentration in the raw water was 2.6 mg / L. The results are shown in Table 2. As shown in Table 2, the SS removal rate was 80.9%, which was high. The pressure remained almost constant at around 10 kPa until 22 hours, but increased sharply after that. However, since washing was performed about once a day, the increase in pressure loss beyond 22 hours did not affect the filtration performance in actual use.

[0094] -Evaluation of compressibility- 80.1 g of dry filter media at 20°C was placed in a 100 mm diameter compression test apparatus, and a load of 16 kg was applied to compress the filter bed. The compression ratio was checked after 5 minutes. The results are shown in Table 3. As shown in Table 3, the compressibility after 5 minutes with a 16 kg load was 63.9%, indicating high compressibility.

[0095] - Assessment of recovery - After measuring the initial compression ratio and removing the weight, the initial recovery rate, calculated by dividing the difference between the filter media filling height after 10 minutes and the filter media filling height after compression by the "filter media filling height before applying the load," was a low 14.0% (see Table 3).

[0096] -Visual inspection of the filter media shape after filtration- After filtration, the filter media were classified into three categories based on their cross-sectional shape: those with almost no change, those compressed and deformed by 20% to 40% of volume without returning to their original shape, and those compressed and deformed by 50% or more of volume without returning to their original shape. The shape changes were then examined. The results are shown in Table 3. As shown in Table 3, after 23 days of filtration, 0% of the filter media showed almost no change in cross-sectional shape, 40% were compressed and deformed by 20% to 40% of the volume and did not return to their original shape, and 60% were compressed and deformed by 50% or more of the volume and did not return to their original shape.

[0097] [Table 1]

[0098] [Table 2]

[0099] [Table 3]

Claims

1. A fibrous filter material comprising a main fiber and a thermoplastic elastomer, At least a portion of the fiber entanglement points of the main fiber are fixed by the thermoplastic elastomer. The aforementioned fibrous filter media has a maximum length of 3 mm to 20 mm and an apparent density of 0.02 g / cm³. ３ ~0.10 g / cm ３ That is, Fiber filter media.

2. The fibrous filter material according to claim 1, wherein the thermoplastic elastomer is a polyether polyester block copolymer having a polybutylene terephthalate-based polyester as the hard segment and a polyoxybutylene-based polyether as the soft segment.

3. The fibrous filter material according to claim 1, wherein the compressibility at 20°C is 20% to 70%.

4. A fibrous filter material according to claim 1 for use in a device having a filtration mechanism.

5. The fiber filter material according to claim 1, wherein the main fiber comprises short fibers having a fineness of 1 dtex to 4 dtex.

6. The fiber filter material according to claim 1, wherein the shape is columnar.

7. A filtration method comprising filtering using a fibrous filter material according to any one of claims 1 to 6 in an apparatus having a filtration mechanism capable of filtering while maintaining the compacted state of the filter layer.

8. A method for producing a fiber filter material containing a main fiber and a thermoplastic elastomer, The process includes a step of processing a sliver, which comprises a main fiber and a thermoplastic elastomer, with a die at 100°C to 200°C. A method for manufacturing fiber filter media.

9. The method for producing a fiber filter material according to claim 8, wherein the main fiber comprises short fibers having a fineness of 1 dtex to 4 dtex.

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