JP7422576B2 - Filter medium, filter element, and method for manufacturing filter medium - Google Patents

Description

The present invention relates to a filter medium having a deodorizing function, a filter element made of the filter medium, and a method for manufacturing the filter medium.

BACKGROUND ART Conventionally, there has been a demand for filter media to purify the air by removing not only dust present in the air but also volatile organic compounds (VOC) that cause odors and allergies.

As a filter material that can remove such VOCs, for example, an adsorbent is placed between layers formed of two nonwoven fabrics, such as the filter material for an air filter disclosed in Japanese Patent Application Laid-open No. 2018-167155 (Patent Document 1). Filter media using activated carbon and inorganic porous materials are known. In addition, the filter medium for air filters of Patent Document 1 is made by stirring an adsorbent (activated carbon, inorganic porous material) and a hot melt adhesive in a shaker, spreading the mixture uniformly on a nonwoven fabric, and heating it to dissolve the hot melt adhesive. Filter media for air filters is manufactured by covering the material with another nonwoven fabric and hot pressing it.

JP2018-167155A (Claim 5, etc.)

However, since the filter medium disclosed in Patent Document 1 is compressed by hot press, the two nonwoven fabrics are dense and the pressure loss is large.

The present invention was made under these circumstances, and aims to provide a filter medium with a deodorizing function that has a small pressure loss, a filter element made of the filter medium, and a method for manufacturing the filter medium.

The invention according to claim 1 of the present invention provides a filter medium in which deodorizing particles are arranged between two fiber aggregates A and B, in which at least one fiber aggregate A is disposed in a cross section in the thickness direction of the filter medium. There are parts with high apparent density and parts with low apparent density, and the apparent density of the part with the highest apparent density and the apparent density of the part with the lowest apparent density in one fiber aggregate A. A filter medium with a difference of 0.030 g/cm ³ or more.

The invention according to claim 2 of the present invention is "the filter medium according to claim 1, wherein the fiber aggregate B and the deodorizing particles are bonded to each other via an organic resin, and the organic resin is in a sheet shape." be.

The invention according to claim 3 of the present invention is as follows: ``Claim 1 or 2, wherein the fiber aggregate B and the deodorizing particles are bonded via an organic resin, and the amount of the organic resin is 10 g/m ² or less. The filter medium described in .

The invention according to claim 4 of the present invention is "the filter medium according to any one of claims 1 to 3, wherein the content of deodorizing particles is 100 g/m ² or less."

The invention according to claim 5 of the present invention is "the filter medium according to any one of claims 1 to 4, wherein the thickness of the filter medium is 0.70 mm or less."

The invention according to claim 6 of the present invention is characterized in that “the filter medium according to any one of claims 1 to 5 is pleated, and the filter medium is provided with an outer frame on the periphery of the pleated filter medium. It becomes a filter element.”

The invention according to claim 7 of the present invention provides the following steps: ``(1) preparing a fiber aggregate B precursor and arranging deodorizing particles on one main surface of the fiber aggregate B precursor; Another fiber aggregate A precursor is laminated on the main surface having deodorizing particles of the body B precursor, and pressure is applied to at least partially deform the fiber aggregate A precursor in the thickness direction to form a fiber aggregate. The step of forming a filter medium in which deodorizing particles are arranged between the fiber aggregate A derived from the A precursor and the fiber aggregate B derived from the fiber aggregate B precursor, according to claim 1. ``Method for manufacturing filter media.''

In the filter medium according to claim 1 of the present invention, there is a difference between the apparent density of the part with the highest apparent density and the part of the fiber aggregate A with the lowest apparent density in the cross section in the thickness direction of one fiber aggregate A. is 0.030 g/ ^cm3 or more, there are parts with low apparent density and parts with high apparent density in fiber aggregate A, and air can easily pass through the parts with low apparent density, so the pressure loss is low. A small filter medium with deodorizing function can be realized.

In the filter medium according to claim 2 of the present invention, the fiber aggregate B and the deodorizing particles are bonded to each other via an organic resin, and the organic resin is in the form of a sheet. Also, the distribution of the organic resin is uniform, and the deodorizing particles are uniformly distributed on the fiber aggregate B, making it easy to realize a filter medium with good deodorizing performance.

In the filter medium according to claim 3 of the present invention, the fiber aggregate B and the deodorizing particles are bonded via an organic resin, and since the amount of the organic resin is as small as 10 g/m ² or less, the filter medium is pleated. When pleating, the adhesion between the deodorizing particles and the organic resin comes off, and pleating is possible even if the force applied during pleating is small, making it a filter medium that is easy to pleat and has excellent processability.

In the filter medium according to claim 4 of the present invention, since the content of deodorizing particles is as small as 100 g/m ² or less, the deodorizing particles are scattered between the two fiber aggregates A and B. Therefore, a portion where the apparent density of one of the fiber aggregates A is low tends to exist in the portion where the deodorizing particles are not present, so it is easy to realize a filter medium with low pressure loss.

The filter medium according to claim 5 of the present invention is a thin filter medium with a thickness of 0.70 mm or less, so it can be installed even in a small space, and it is easy to pleat and has good workability. It is an excellent filter medium.

Since the filter element according to claim 6 of the present invention is pleated, the filtering area of the filter medium is wide, and the filter element has excellent dust and VOC collection efficiency.

The method for producing a filter medium according to claim 7 of the present invention includes arranging deodorizing particles on one main surface of the fiber aggregate B precursor, and then disposing the deodorizing particles on the main surface of the fiber aggregate B precursor having the deodorizing particles. Another fiber aggregate A precursor is laminated and pressurized to at least partially deform the fiber aggregate A precursor in the thickness direction, so that the fiber aggregate A derived from the fiber aggregate A precursor and the fiber By forming a filter medium in which deodorizing particles are arranged between fiber aggregates B derived from an aggregate B precursor, this method can produce a filter medium with a deodorizing function and a small pressure loss.

It is an explanatory view showing an example of the cross section of the filter medium of the present invention in the thickness direction. FIG. 2 is an explanatory diagram showing a cross section in the thickness direction of a conventional filter medium. 1 is a photograph taken with a scanning electron microscope (magnification: 80 times) of a cross section in the thickness direction of the filter medium of Example 1. This is a photograph of a cross section in the thickness direction of the filter medium of Comparative Example 1, taken with a scanning electron microscope (magnification: 80 times).

The fiber aggregate A(1) constituting the filter medium of the present invention has a portion with high apparent density and a portion with low apparent density in the cross section in the thickness direction of the filter medium, and the one fiber aggregate A(1) has a portion with high apparent density and a portion with low apparent density. ), the difference between the apparent density of the part with the highest apparent density and the part with the lowest apparent density is 0.030 g/cm ³ or more.

The filter medium of the present invention includes fiber aggregates A(1) and fiber aggregates B(2), and the fiber aggregate A(1) has a larger difference in apparent density in the cross section in the thickness direction of the filter medium. ).

FIG. 1 illustrates an example of a cross section in the thickness direction of a filter medium in which the fiber aggregate A(1) has a portion with a high apparent density and a portion with a low apparent density. In the filter medium shown in FIG. 1, the fiber aggregate A (1) constituting the filter medium follows the shape of the deodorizing particles (3), and the length of the fiber aggregate A in the thickness direction is not constant. In addition, in FIG. 1, the part with the highest apparent density in the fiber aggregate A (1) is the part (5) with the shortest length in the thickness direction in the fiber aggregate A (1), The portion with the lowest apparent density in (1) is the portion (6) with the longest length in the thickness direction in the fiber aggregate A (1). On the other hand, in the filter medium of the prior art, the length of the fiber aggregate A(1) in the thickness direction is constant, as shown in FIG. ) is also constant.

The apparent density of the portion with the highest apparent density and the apparent density of the portion of the fiber aggregates A and B with the lowest apparent density in the cross section in the thickness direction of the filter medium shown in FIG. It can be calculated.
(1) Calculate the basis weight of fiber aggregate A or B. Note that the basis weight refers to the mass per 1 m ² of area on the widest surface.
(2) Cut the filter medium in a direction perpendicular to the main surface of the filter medium.
(3) Observe the cut surface of the filter medium cut in (2) with a microscope, and take three cross-sectional photographs of the filter medium. At this time, take a cross-sectional photograph so that the long side of the cut surface of the filter medium is 1 cm or more.
(4) From the cross-sectional photographs of the three filter media obtained in (3), the longest length (mm) of the fiber aggregate A or B in the thickness direction perpendicular to the main surface of the filter media is determined from the cross-sectional photographs. The measured values for the three cross-sectional photographs are arithmetic averaged and rounded to the fourth decimal place. In addition, the shortest length (mm) of the fiber aggregate A or B in the thickness direction is similarly determined. Note that the "principal surface" in the present invention refers to the widest surface.
(5) The apparent density of the part (the part with the highest apparent density) having the shortest length in the thickness direction in fiber aggregates A and B and the part having the longest length in the thickness direction in the following formula: Calculate the apparent density of (the part with the lowest apparent density).
d={a/b}/10 ³
d: Apparent density (g/cm ³ )
a: Fabric weight of fiber aggregate (g/m ² )
b: Arithmetic mean value of the longest or shortest length in the thickness direction of the fiber aggregate (mm)

The difference between the apparent density of the portion with the highest apparent density and the portion of the fiber aggregate A(1) constituting the filter medium of the present invention with the lowest apparent density is 0.030 g/cm ³ or more. However, the larger the difference in apparent density, the easier air can pass through the parts with lower apparent density, so the apparent density of the part with the highest apparent density and the part with the lowest apparent density The difference is more preferably 0.035 g/cm ³ or more, and even more preferably 0.040 g/cm ³ or more. If the difference between the apparent density of the part with the highest apparent density and the part with the lowest apparent density is too large, the air permeability of the part with the highest apparent density will be too low, causing an increase in pressure loss. Therefore, it is preferably 0.080 g/cm ³ or less.

In addition, the length in the thickness direction of the part with the highest apparent density in the fiber aggregate A (1) should be 0.070 mm or more, since the longer it is, the higher the air permeability and the lower pressure loss can be achieved. It is preferably 0.090 mm or more, more preferably 0.110 mm or more. Regarding the upper limit, if the length in the thickness direction is too long, the filtration performance of the filter medium may deteriorate, so 0.250 mm or less is realistic. The length in the thickness direction of the portion with the lowest apparent density in the fiber aggregate A (1) is preferably 1.00 mm or less, and 0.700 mm or less, since the filtration performance of the filter medium may deteriorate if it is too long. The following is preferable, and 0.550 mm or less is more preferable. Regarding the lower limit, if it is too short, the air permeability may decrease and the filter medium may have a high pressure loss, so 0.100 mm or more is realistic.

Furthermore, the lower the apparent density of the portion of the fiber aggregate A (1) with the highest apparent density, the higher the air permeability and the ^lower the pressure loss can be achieved. It is preferably 0.150 g/cm ³ or less, more preferably 0.130 g/cm ³ or less. As for the lower limit, a realistic value of 0.100 g/cm ³ or more is possible since there is a possibility that the filtration performance of the filter medium may deteriorate. If the apparent density of the portion of the fiber aggregate A(1) with the lowest apparent density is too low, the filtration performance of the filter medium may ^deteriorate . 0.030 g/cm ³ or more is more preferable, and even more preferably 0.040 g/cm ³ or more. Regarding the upper limit, a realistic value of 0.100 g/cm ³ or less is because if the apparent density is too high, the air permeability may decrease and the filter medium may have a high pressure loss.

The fiber aggregate A(1) constituting the filter medium of the present invention can be composed of, for example, nonwoven fabric, woven fabric, or knitted fabric.

Examples of the components constituting the fiber aggregate A(1) include polyolefin resins (polyethylene, polypropylene, polymethylpentene, polyolefin resins with a structure in which a portion of the hydrocarbon is replaced with a cyano group or a halogen such as fluorine or chlorine). ), styrene resin, polyether resin (polyether ether ketone, polyacetal, phenol resin, melamine resin, urea resin, epoxy resin, modified polyphenylene ether, aromatic polyether ketone, etc.), polyester resin (Polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polycarbonate, polyarylate, wholly aromatic polyester resin, unsaturated polyester resin, etc.), polyimide resin, polyamideimide resin, polyamide resin resins (e.g., aromatic polyamide resins, aromatic polyetheramide resins, nylon resins, etc.), resins with nitrile groups (e.g., polyacrylonitrile, etc.), urethane resins, epoxy resins, polysulfone resins (polysulfone, polyether sulfone, etc.), fluorine resins (polytetrafluoroethylene, polyvinylidene fluoride, etc.), cellulose resins, polybenzimidazole resins, acrylic resins (e.g., polyacrylonitrile resins copolymerized with acrylic esters or methacrylic esters, etc.) , a modacrylic resin copolymerized with acrylonitrile and vinyl chloride or vinylidene chloride, etc.), vinylon fiber, and other known organic resins.

Note that these organic resins may have either a linear polymer structure or a branched polymer structure, and the organic resin may be a block copolymer or a random copolymer. There are no particular limitations on the steric structure or the presence or absence of crystallinity. Furthermore, it may be a mixture of organic resins, and is not particularly limited.

The fibers constituting the fiber aggregate A(1) are, for example, one type of fibers selected from melt spinning, dry spinning, wet spinning, direct spinning (melt blowing, spunbond, electrostatic spinning, etc.), and composite fibers. It can be obtained by a known method such as a method of extracting fibers with a small fiber diameter by removing the above organic resin, or a method of obtaining split fibers by beating the fibers.

The fibers constituting the fiber aggregate A(1) may be composed of one type or multiple types of organic resin. As the fiber containing multiple types of organic resins, conjugate fibers generally referred to as conjugate fibers, such as core-sheath type, sea-island type, side-by-side type, and orange type, can be used.

The fiber diameter of the fibers constituting the fiber aggregate A(1) is not particularly limited, but the fiber diameter is preferably 1.0 to 30 μm, more preferably 1.5 to 20 μm, and 2.0 to 15 μm. is even more preferable. The fiber length of the fibers constituting the fiber aggregate A is preferably 5 mm or more, more preferably 10 mm or more, even more preferably 20 mm or more, since the longer the fiber aggregate A is, the better the shape stability is. It may be.

The fiber aggregate B(2) constituting the filter medium of the present invention can have the same constituent components and constituent fibers as the fiber aggregate A(1).

The fiber diameter and fiber length of the fibers constituting the fiber aggregate B (2) are not particularly limited, but the fiber diameter is preferably 1.0 to 50 μm, more preferably 3.0 to 40 μm, and More preferably, the thickness is from .0 to 30 μm. The fiber length is preferably 3 mm or more, more preferably 4 mm or more, and even more preferably 5 mm or more. As for the upper limit of the fiber length, 25 mm or less is realistic.

The deodorizing particles (3) constituting the filter medium of the present invention refer to particles having a deodorizing effect, and examples thereof include activated carbon and inorganic particles such as silica gel and titanium oxide. The number of deodorizing particles constituting the filter medium of the present invention may be one type or two or more types. Among these, it is preferable that the deodorizing particles contain two types, activated carbon and silica gel, because the filter medium can efficiently deodorize.

The shape and size of the deodorizing particles (3) are adjusted as appropriate, but the deodorizing particles may be, for example, spherical (approximately spherical or true spherical), fibrous, acicular, flat, irregular, polyhedral, feather-like, etc. It can be appropriately selected from tetrapod shapes and the like. Further, the average particle diameter of the deodorizing particles is preferably 0.10 to 1.5 mm, more preferably 0.11 to 1.2 mm, and most preferably 0.12 to 1.0 mm. preferable.

In addition, the particle diameter of the deodorizing particles (3) in the present invention refers to the diameter of the deodorizing particles that can be measured by taking an electron micrograph of the deodorizing particles or an electron micrograph of the main surface of the filter medium containing the deodorizing particles. The average particle diameter means the average particle diameter of 10 deodorizing particles. In addition, when the shape of the deodorizing particles shown in an electron micrograph is non-circular, the diameter of a circle having the same area as the deodorizing particles having the shape shown in the electron micrograph is regarded as the diameter of the deodorizing particles.

Further, the deodorizing particles (3) may contain compounds that react with odor components and compounds that adsorb odor components, such as amine compounds and acid hydrazide compounds, for the purpose of improving deodorization efficiency.

The lower the content of the deodorizing particles (3) contained in the filter medium of the present invention, the more the constituent fibers of the fiber aggregate A (1) enter into the part of the filter medium where the deodorizing particles are not present, and the fiber aggregate Since parts of body A (1) with low apparent density tend to exist, it is easy to realize a filter medium with low pressure loss, so it is preferably 100 g/m ² or less, more preferably 90 g/m ² or less, and 80 g/m 2 or less. ² or less is more preferable. On the other hand, if the content of the deodorizing particles is too small, the filter medium may not be able to sufficiently capture VOCs and the deodorizing effect of the filter medium may be insufficient, so it is realistically 5 g/m ² or more.

In the filter medium of the present invention, it is preferable that the fiber aggregate B (2) and the deodorizing particles (3) are bonded to each other via an organic resin (4) so that the deodorizing particles (3) are difficult to fall off from the filter medium. . When the fiber aggregate B (2) and the deodorizing particles (3) are bonded via the organic resin (4), the shape of the organic resin (4) may be, for example, particulate or sheet-like. When the organic resin (4) is in the form of a sheet, the distribution of the organic resin (4) is more uniform than when the organic resin (4) is in the form of particles, and the deodorizing particles are distributed on the fiber aggregate B (2). is preferable because it is easy to realize a filter medium with good deodorizing performance and uniform distribution of odor.

The type of organic resin (4) used for adhesion used in the present invention is appropriately selected and is not particularly limited. can be used.

If the amount of organic resin (4) bonding fiber aggregate B (2) and deodorizing particles ( ³ ) in the filter medium is 10 g/m2 or less, the deodorizing particles (3) will be removed when pleating the filter medium. The adhesion between the organic resin (4) and the organic resin (4) is released, and pleating is possible even with less force applied during pleating, making it easy to pleat and having excellent workability. According to (4), it is a filter medium that is difficult to reduce pressure and has a small pressure loss, which is preferable. The smaller the amount of the organic resin (4) bonding the fiber aggregate B (2) and the deodorizing particles ( ³ ), the more the above effect can be obtained. m ² or less is more preferable. On the other hand, if the amount of the organic resin (4) is too small, the deodorizing particles ( ³ ) may easily fall off from the filter medium, so it is preferably 1 g/m2 or more, more preferably 2 g/m2 or ^more , and 3 g/m2 or more. /m ² or more is more preferable.

In addition, for the purpose of preventing the deodorizing particles (3) from falling off and improving the handling of the filter medium, the fiber aggregate A (1) and the deodorizing particles (3) may be bonded via an organic resin. The shape of the organic resin is not particularly limited. The larger the total amount of organic resin that adheres the fiber aggregates A (1) and B (2) and the deodorizing particles in the filter medium, the more difficult it is for the deodorizing particles to fall off. Since the air permeability of the filter medium may decrease and the pressure loss may increase, and the processability of the filter medium may deteriorate, it is preferably 2 to 20 g/m ² , more preferably 4 to 18 g/m ² , and 6 ˜16 g/m ² is more preferred.

Although the basis weight of the filter medium of the present invention is adjusted as appropriate, it is preferably 50 to 200 g/m ² , more preferably 80 to 170 g/m ² , and even more preferably 100 to 150 g/m ² .

Further, the thickness of the filter medium of the present invention is preferably 0.70 mm or less so that the filter medium can be installed even in a small space and has excellent processability (pleat processing, etc.). Since the thinner the thickness, the more the above effect can be obtained, the thickness is more preferably 0.68 mm or less, and even more preferably 0.66 mm or less. On the other hand, if the filter medium is too thin, the shape retention may deteriorate, so the thickness is preferably 0.30 mm or more, more preferably 0.40 mm or more, and even more preferably 0.50 mm or more. The "thickness" of the filter medium and the fiber aggregate A precursor and fiber aggregate B precursor described below were measured using a high-precision digital measuring device (registered trademark: Lightmatic (VL-50A), manufactured by Mitutoyo Co., Ltd.). It refers to the arithmetic average value of the distance between each main surface measured at five points when a load of 100 g is applied in the direction between the main surfaces, and the length in the thickness direction of the fiber aggregates A and B mentioned above. have different definitions.

Preferably, at least one of the fiber aggregates A(1) and B(2) constituting the filter medium is treated with electret. Due to the electret treatment, submicron-sized and nano-sized fine dust, which is normally difficult to remove, can be collected by electrostatic force.

The filter medium of the present invention has two fiber aggregates A (1) and B (2) and deodorizing particles (3), but includes fiber aggregates other than fiber aggregates A and B, and air permeability. It may also include a breathable material such as a porous film or a breathable foam.

Moreover, the filter medium of the present invention may allow air to pass through so that the fiber aggregate A(1) is on the upstream side, or may allow air to pass through so that the fiber aggregate B(2) is on the upstream side. However, if the air passes through fiber aggregate B (2), which has a small difference in apparent density inside the fiber aggregate, on the upstream side, the air flow will be less biased in the filter medium, and dust and dirt will be removed more efficiently. Since VOCs can be collected, when using a filter medium, it is preferable to use the filter medium so that air passes through it so that the fiber aggregate B side is on the upstream side.

Note that the cross-sectional structure in the thickness direction of the filter medium of the present invention is not limited to that illustrated in FIG. Even when the filter media have different apparent densities, the same effects as those of the filter media having the cross-sectional structure illustrated in FIG. 1 can be achieved.

Furthermore, the filter medium of the present invention may be in the form of a flat plate that is not particularly processed, but it is also possible to use a pleated filter medium of the present invention, and a pleated filter medium with an outer frame on the periphery. A filter element having a large filtration area and excellent dust and VOC collection efficiency is preferable. The pleat height of the filter element of the present invention is preferably 5 to 50 mm, more preferably 10 to 45 mm, and even more preferably 15 to 30 mm. The pleat interval of the filter element is preferably 2 to 20 mm, more preferably 3 to 15 mm, and even more preferably 3 to 10 mm. The outer frame of the filter element is the entire peripheral edge of the pleated filter medium (for example, if the filter medium is pleated but has a rectangular planar shape, the peripheral edge in the direction perpendicular to the fold direction of the pleats, and the folds of the pleats) (periphery in a direction parallel to the direction), or only a part of the periphery of a pleated filter medium (for example, if the filter medium is pleated but has a rectangular planar shape, the pleat shape may be fixed). For the purpose of holding, the pleats may be located only at the peripheral edge in a direction perpendicular to the fold direction of the pleats.

Further, the pleated filter medium and the outer frame can be bonded, for example, by interposing a hot melt resin such as polyvinyl acetate between the outer frame and the filter medium. Further, as the outer frame, for example, an outer frame made of aluminum, aluminum alloy, stainless steel, various resins, paper, or nonwoven fabric can be used.

Note that the above-described filter medium and filter element can be used as a filter unit by being housed in a frame-shaped filter frame, for example.

Furthermore, the filter medium of the present invention may be subjected to processing other than pleating. Examples of processed filter media of the present invention include roll filters for roll filter devices in which the filter media is processed so as to be rolled and used by unwinding the filter media.

Next, a method for manufacturing the filter medium of the present invention will be explained.

First, a fiber aggregate B precursor is prepared, and deodorizing particles are placed on one main surface of the fiber aggregate B precursor.

The fiber aggregate B precursor can be composed of, for example, nonwoven fabric, woven fabric, or knitted fabric. When the fiber aggregate B precursor is a woven fabric or a knitted fabric, the fiber aggregate B precursor can be prepared by weaving or knitting the fibers prepared as described above. When the fiber aggregate B precursor is a nonwoven fabric, for example, a dry nonwoven fabric by a dry process, a wet nonwoven fabric by a wet process, a spunbond nonwoven fabric by a direct spinning process, a melt-blown nonwoven fabric, an electrostatically spun nonwoven fabric, etc. can be used. Among these, non-woven fabrics are preferable because they have excellent processability (pleating etc.) of the filter medium, and among non-woven fabrics, wet-laid non-woven fabrics are more preferable because their constituent fibers have short fiber lengths and have better pleat processability. .

When the fiber aggregate B precursor is a nonwoven fabric, the constituent fibers of the nonwoven fabric may be bound together by, for example, entangling them with a needle or water stream, integrating the fibers with a binder, or combining the constituent fibers of the nonwoven fabric. When the fibrous web before being combined contains fibers containing a thermoplastic resin, a method of heat-treating the fibrous web to melt the thermoplastic resin and integrate the fibers can be mentioned. . In addition, as a method for heat-treating the fiber web, for example, a method of heating and pressurizing with a calendar roll, a method of heating with a hot air dryer, a method of melting the thermoplastic resin fibers by irradiating infrared rays under no pressure, etc. can be used. can.

The apparent density of the fiber aggregate B precursor is preferably 0.060 to 0.400 g/cm 3 , and preferably 0.080 to 0.400 g/cm ³ so that a filter medium with excellent filtration performance and a filter medium with excellent processability can be produced. More preferably, it is 0.300 g/cm ³ , and even more preferably 0.100 to 0.200 g/cm ³ . Further, the basis weight of the fiber aggregate B precursor is preferably 10.0 to 100 g/m ² and 20.0 to 80. More preferably, it is 0 g/m ² , and even more preferably 30.0 to 60.0 g/m ² . Furthermore, the thickness of the fiber aggregate B precursor is preferably 0.100 to 0.600 mm, and preferably 0.150 to 0.600 mm, so that a filter medium with excellent filtration performance and a filter medium with excellent processability can be produced. It is more preferably 500 mm, and even more preferably 0.200 to 0.400 mm.

Furthermore, the amount of the deodorizing particles (3) to be arranged is such that the fiber aggregate A precursor enters the portion where the deodorizing particles (3) are not present, and the cross section in the thickness direction of the fiber aggregate A (1) constituting the filter medium is determined. In order to have a portion with high apparent density and a portion with low apparent density, it is preferably 100 g/m ² or less, more preferably 90 g/m ² or less, and even more preferably 80 g/m ² or less.

Moreover, the method of arranging the deodorizing particles (3) is not particularly limited. In addition, in order to prevent the deodorizing particles (3) from falling off, an organic resin (4) is placed on one main surface of the fiber aggregate B precursor before the deodorizing particles (3) are placed, and the fiber aggregate B It is preferable to adhere the precursor and the deodorizing particles (3). The method of arranging the organic resin (4) and bonding the fiber aggregate B precursor and the deodorizing particles (3) includes, for example, laminating sheet-like organic resins (4) or stacking particulate organic resins (4). The organic resin (4) is placed on one main surface of the fiber aggregate B precursor by dispersing the organic resin (4), and then the organic resin (4) is dissolved by heat or high-temperature steam, etc. There is a method in which the deodorizing particles (3) are placed while the particles are melting, and the deodorizing particles (3) are bonded by cooling. A method of placing the deodorizing particles (3) on the main surface, placing the deodorizing particles (3) while the organic resin (4) is dissolved, cooling and adhering the deodorizing particles (3); The organic resin (4) is placed on one main surface of the fiber aggregate B precursor by applying 4), and then the deodorizing particles (3) are placed before the organic resin (4) dries and solidifies. After that, the organic resin (4) is dried and the deodorizing particles (3) are bonded to the organic resin (4).

Next, another fiber aggregate A precursor is laminated on the main surface having the deodorizing particles (3) of the fiber aggregate B precursor, and pressure is applied to at least partially remove the fiber aggregate A precursor in the thickness direction. deodorizing particles (3) are arranged between fiber aggregate A (1) derived from fiber aggregate A precursor and fiber aggregate B (2) derived from fiber aggregate B precursor. Additionally, a filter medium of the present invention is manufactured.

The fiber aggregate A precursor, like the fiber aggregate B precursor, can be composed of nonwoven fabric, woven fabric, or knitted fabric, but among these, the thickness is easy to change, and the fiber aggregate A precursor Nonwoven fabrics that tend to have a difference in apparent density of 0.030 g/ ^m2 or more between the area with the highest apparent density and the area with the lowest apparent density in the fiber aggregate A (1) are preferred, and among nonwoven fabrics, A dry non-woven fabric or a melt-blown non-woven fabric that tends to have a difference in apparent density of 0.030 g/m2 or ^more and has a certain thickness is more preferable, and can be easily treated with electret, and a filter medium with high dust collection performance can be realized. More preferred are melt-blown nonwoven fabrics.

At this time, the constituent fibers of the fiber aggregate A precursor enter into the part where the deodorizing particles (3) are not present, and in the cross section of the fiber aggregate A (1) in the thickness direction, it is seen as a part with high apparent density. The apparent density of the fiber aggregate A precursor is 0.020 to 0.200 g/cm ³ so that it is easy to manufacture a filter medium with a low hanging density and a filter medium with excellent filtration performance. It is preferably 0.025 to 0.100 g/cm ³ , more preferably 0.030 to 0.050 g/cm ³ . In addition, the thickness of the fiber aggregate A precursor is set so that it is easy to produce a portion with a high apparent density and a filter medium with a low apparent density in the cross section of the fiber aggregate A (1) in the thickness direction. In order to easily manufacture a filter medium with excellent filtration performance, the diameter is preferably 0.050 to 0.800 mm, more preferably 0.070 to 0.500 mm, and 0.100 to 0.400 mm. More preferred. Furthermore, the basis weight of the fiber aggregate A precursor is preferably 5.0 to 30.0 g/m ² so that the filter medium has excellent filtration performance and processability. It is more preferably 0 to 25.0 g/m ² , and even more preferably 10.0 to 20.0 g/m ² .

The method of applying pressure when laminating another fiber aggregate A precursor on the main surface having deodorizing particles of the fiber aggregate B precursor and applying pressure is not particularly limited, but for example, between two rolls. Examples include a method of applying pressure by passing through a layer, and a method of applying pressure by pressing from above a laminated product. When applying pressure by passing between two rolls, the fiber aggregate B precursor, the deodorizing particles, and the fiber aggregate are deformed at least partially in the thickness direction. It is preferable that the distance between the two rolls is narrower than the thickness of the laminate obtained by laminating the body A precursors, and the distance between the two rolls is smaller than the total thickness of the fiber aggregate B precursor and the fiber aggregate A precursor. It is more preferable to make it narrow. Note that the temperature during pressurization may be heated without particular heating, but if the temperature is too high, the constituent fibers of fiber aggregate precursors A and B may be dissolved and the fiber aggregate precursor A may be heated. , B may be blocked and pressure loss may increase, it is preferable to apply pressure at a temperature lower than the lowest melting point of the constituent fibers of the fiber aggregates A and B precursors.

In addition, for the purpose of preventing the deodorizing particles (3) from falling off and improving the handling of the filter medium, before laminating another fiber aggregate A precursor on the main surface of the fiber aggregate B precursor having the deodorizing particles. , an organic resin is placed on the main surface of the fiber aggregate B precursor having deodorizing particles or on one main surface of the fiber aggregate A precursor, and the fiber aggregate B precursor and/or the deodorizing particles (3) are arranged. It is preferable to bond the fiber aggregate A precursor to the fiber aggregate A precursor. As a method for placing an organic resin and bonding the fiber aggregate B precursor and/or deodorizing particles (3) to the fiber aggregate A precursor, the above organic resin is placed, and the fiber aggregate B precursor and/or the deodorizing particles (3) are bonded together. A method similar to the method of bonding the deodorizing particles (3) can be employed. Note that even if the adhesion between the fiber aggregate B precursor and the deodorizing particles (3) and the adhesion between the fiber aggregate B precursor and/or the deodorizing particles (3) and the fiber aggregate A precursor are performed at the same time, You can also go separately.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but these are not intended to limit the scope of the present invention.

(Example 1)
(Fiber aggregate A precursor)
A polypropylene resin with a melting point of 160°C was used as the thermoplastic resin, and an apparatus consisting of an extruder, a gear pump, a melt blow nozzle, a compressed air generator, an air heater, a collection conveyor, and a winder was used to produce a fabric weight of 15.0 g. A melt ^- blown nonwoven fabric with continuous fibers having a fiber diameter of 2.0 to 5.0 ^μm was produced. Thereafter, the melt-blown nonwoven fabric was subjected to an electret treatment to produce a fiber aggregate A precursor.
(Fiber aggregate B precursor)
A fibrous web with a basis weight of 35.0 g/m ² is produced using a wet method using an inclined wire method, and is composed of 60 mass% polyethylene terephthalate fibers with a fiber diameter of 25 μm and a fiber length of 20 mm, and 40 mass% of vinylon fibers with a fiber diameter of 15 μm and a fiber length of 20 mm. was created. Thereafter, the fiber web is impregnated with an acrylic binder and subjected to dry heat treatment to obtain a fiber aggregate B precursor consisting of a wet-laid nonwoven fabric having a basis weight of 45.0 g/m ² , a thickness of 0.300 mm, and an apparent density of 0.150 g/cm ³ was created.
(deodorizing particles)
Activated carbon having an average particle diameter of 0.30 μm and a specific surface area of 1100 m ² /g, and spherical silica gel having an average particle diameter of 0.15 μm and a specific surface area of 480 m ² /g were prepared.
Next, the activated carbon and the silica gel were mixed at a mass ratio of 3:1 to obtain deodorizing particles of the present invention.
(Manufacture of filter media)
A thermoplastic organic resin sheet having a melting point of 110° C. and made of copolyamide having a basis weight of 5 g/m ² was laminated on one main surface of the fiber aggregate B precursor.
Next, deodorizing particles were uniformly sprinkled on the main surface having a thermoplastic organic resin sheet made of a copolymerized polyamide of the fiber aggregate B precursor so that the total amount was 63 g/m ² .
Thereafter, steam treatment was performed at a pressure of 5 kg/cm ² and a temperature of 120° C. for 7 seconds to melt the thermoplastic organic resin sheet and adhere the fiber aggregate B precursor and the deodorizing particles.
Furthermore, on the main surface of the fiber aggregate B precursor having the deodorizing particles, a melted hot melt resin made of polypropylene with a basis weight of 5 g/m ² is sprayed, and while the hot melt resin is melting, The fiber aggregate A precursor was laminated and passed between two rolls at room temperature with an inter-roll distance of 0.65 mm to adhere the fiber aggregate A precursor and deodorizing particles to a fabric weight of 133 g/m ² and a thickness. A filter medium of 0.65 mm was obtained. In the filter medium of Example 1, the longest length in the thickness direction of fiber aggregate A is 0.238 mm, the shortest length in the thickness direction is 0.120 mm, and the portion of fiber aggregate A with the highest apparent density. The apparent density of the sample was 0.125 g/cm ³ , and the apparent density of the portion with the lowest apparent density was 0.063 g/cm ³ , with a difference of 0.062 g/cm ³ . In addition, the longest length in the thickness direction of fiber aggregate B is 0.290 mm, the shortest length in the thickness direction is 0.276 mm, and the apparent density of the part with the highest apparent density is 0.163 g/cm ^3. The apparent density of the part with the lowest apparent density was 0.155 g/cm ³ , with a difference of 0.008 g/cm ³ .
(Manufacture of filter elements)
The filter medium was subjected to a pleating machine, and an outer frame made of nonwoven fabric was attached to the entire periphery of the filter medium using hot melt resin to produce a filter element with a square size of 200 mm, a pleat height of 19 mm, and a pleat interval of 3 mm. did.

(Comparative example 1)
(Manufacture of filter media)
On one main surface of the same fiber aggregate B precursor as in Example 1, a mixture of 63 g/m ² of the same deodorizing particles as in Example 1 and 10 g/m ² of low-density polyethylene particles with a melting point of 98 ° C. was sprinkled, and then A steam treatment was performed at a pressure of 5 kg/cm ² and a temperature of 120° C. for 7 seconds to melt the low-density polyethylene particles and adhere the fiber aggregate B precursor to the deodorizing particles.
Furthermore, while the low-density polyethylene particles were melting, the same fiber aggregate A precursor as in Example 1 was laminated on the main surface of the fiber aggregate B precursor having deodorizing particles, and the distance between the rolls was 0.65 mm. The filter medium was passed between two rolls at room temperature to adhere the fiber aggregate A precursor and the deodorizing particles to obtain a filter medium having a basis weight of 133 g/m ² and a thickness of 0.65 mm. In the filter medium of Comparative Example 1, the longest length in the thickness direction of fiber aggregate A is 0.188 mm, the shortest length in the thickness direction is 0.142 mm, and the portion of fiber aggregate A with the highest apparent density. The apparent density was 0.106 g/cm ³ , the apparent density of the part with the lowest apparent density was 0.080 g/cm ³ , and the difference was 0.026 g/cm ³ . In addition, the longest length in the thickness direction of fiber aggregate B is 0.283 mm, the shortest length in the thickness direction is 0.271 mm, and the apparent density of the part with the highest apparent density is 0.166 g/cm ^3. The apparent density of the part with the lowest apparent density was 0.159 g/cm ³ , with a difference of 0.007 g/cm ³ .
(Manufacture of filter elements)
The filter medium was subjected to a pleating machine, and an outer frame made of nonwoven fabric was attached to the entire periphery of the filter medium using hot melt resin to produce a filter element with a square size of 200 mm, a pleat height of 19 mm, and a pleat interval of 3 mm. did.

The filter media and filter elements of Examples and Comparative Examples were evaluated in the following pressure drop test.

(Pressure loss test)
The filter media and filter elements of Examples and Comparative Examples were set in a holder with an effective frontage area of 0.1 ^m2 , and air was blown vertically from the fiber aggregate B side toward the fiber aggregate A side at a surface wind speed of 3 m/min. The pressure difference between the upstream and downstream sides of the filter medium and filter element was measured using a MODUS digital manometer MA2-04P differential pressure gauge. The measurement was performed by arbitrarily sampling five locations from one filter medium or filter element, and the average value was taken as the pressure loss (unit: Pa) of the filter medium and filter element.

The results of the pressure drop test are shown in Table 1 below.

From the results in Table 1, it can be seen that the filter medium and filter element of Example 1 having the structure of the present invention were made using the same fiber aggregate A precursor and Although it is manufactured using the fiber aggregate B precursor and is composed of the same amount of deodorizing particles and the organic resin that bonds the same amount of deodorizing particles and the fiber aggregate, it is a filter medium and filter element with low pressure loss. I found out something.

The filter medium and filter element according to the present invention can be used as a filter for purifying the air inside a room, etc., and are particularly preferably used as an air filter for purifying the air inside a vehicle such as an automobile or a railway vehicle.

1... Fiber aggregate A
2...Fiber aggregate B
3... Deodorizing particles 4... Organic resin 5... Portion with the shortest length in the thickness direction in the fiber aggregate A 6... Portion with the longest length in the thickness direction in the fiber aggregate A

Claims (7)

A filter medium in which deodorizing particles are arranged between two fiber aggregates A and B,
In the cross section of the filter medium in the thickness direction, at least one fiber aggregate A has a portion with high apparent density and a portion with low apparent density,
The apparent density of the portion with the highest apparent density in the one fiber aggregate A is 0.100 g/cm ³ or more and 0.200 g/cm ³ or less,
The apparent density of the portion with the lowest apparent density in the one fiber aggregate A is 0.020 g/cm ³ or more and 0.100 g/cm ³ or less,
The length in the thickness direction of the portion with the highest apparent density in the one fiber aggregate A is 0.070 mm or more and 0.250 mm or less,
The length in the thickness direction of the portion with the lowest apparent density in the one fiber aggregate A is 0.100 mm or more and 1.00 mm or less,
A filter medium in which the difference between the apparent density of the part with the highest apparent density and the part of the fiber aggregate A with the lowest apparent density is 0.030 g/cm ³ or more. The filter medium according to claim 1, wherein the fiber aggregate B and the deodorizing particles are bonded to each other via an organic resin, and the organic resin is in the form of a sheet. The filter medium according to claim 1 or 2, wherein the fiber aggregate B and the deodorizing particles are bonded to each other via an organic resin, and the amount of the organic resin is 10 g/m ² or less. The filter medium according to any one of claims 1 to 3, wherein the content of deodorizing particles is 100 g/m ² or less. The filter medium according to any one of claims 1 to 4, wherein the thickness of the filter medium is 0.70 mm or less. A filter element comprising: a pleated filter medium according to claim 1; and an outer frame around the pleated filter medium. (1) preparing a fiber aggregate B precursor and arranging deodorizing particles on one main surface of the fiber aggregate B precursor;
(2) Laminating another fiber aggregate A precursor on the main surface having deodorizing particles of the fiber aggregate B precursor and applying pressure to partially deform at least the fiber aggregate A precursor in the thickness direction. forming a filter medium in which deodorizing particles are arranged between a fiber aggregate A derived from a fiber aggregate A precursor and a fiber aggregate B derived from a fiber aggregate B precursor;
The method for producing a filter medium according to claim 1, comprising:

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