JP2011194336A - Laminated filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated filter which shows high rigidity and enhanced capturing rate by suppressing an increase in the pressure loss during filter passage.SOLUTION: This laminated filter 1 includes a back layer 2 made up of a fiber sheet and a face layer 3 of a fiber sheet. In addition, the laminated filter 1 is used in the way that the back layer 2 is positioned on the downstream side of a fluid suction. The back layer 2 includes a plurality of through apertures 20 and shows that the distance between the fibers in a part 21 other than the through aperture 20 in the back layer 2 is longer than the distance between the fibers of the face layer 3.

Description

  The present invention relates to a laminated filter used by being attached to a frame body provided on an air suction side of a grease filter installed in a ventilation fan, a range hood, or the like.

Grease that captures oil smoke etc. at the suction port of the ventilation fan and range hood to prevent the smoke exhaust fan etc. from being directly soiled by oil smoke and dust generated during cooking (hereinafter also referred to as oil smoke). A metal filter called a filter is attached. However, this grease filter has an insufficient ability to collect oil smoke and the like so that the inside of the hood is soiled and cleaning is troublesome, and in order to reduce the trouble, a nonwoven fabric or the like is further added to the outer frame body. A disposable filter made of a material (a so-called range hood filter) is attached and used. As a method for increasing the collection rate of oil smoke and the like by such a filter for a range hood, a method of narrowing the eyes of the filter by a method of reducing the fiber diameter of the fiber to be used or increasing the amount of the fiber to be used can be considered. . However, if the filter is made finer in this way to increase the collection rate, the pressure loss when passing through the filter increases and the air permeability decreases. In addition, it is desirable to increase the retention amount of oil or the like and extend the usable period, but in order to increase the retention amount, it is necessary to increase the amount of fibers, leading to an increase in pressure loss. This leads to a reduction in ventilation performance by obstructing the suction of the ventilation fan by mounting the range hood filter. Further, if the amount of fibers is reduced in order to suppress an increase in pressure loss when passing through the filter, or if the density of the filter is lowered and bulky, the rigidity of the filter for the range hood is generally lowered or the collection performance is lowered. Also, if the rigidity is lowered, the range hood filter is loosened when the range hood filter is attached to the grease filter frame, the range hood filter cannot be brought into close contact with the grease filter, and the collection rate is reduced. This will cause the grease filter and the ventilation fan body to become dirty.
Therefore, there is a need for a filter that balances the performance of each of the performances while suppressing an increase in pressure loss when passing through the filter and having a high rigidity and a long use period.

Apart from the above technique, Patent Document 1 discloses an ultrafine nonwoven fabric having an average fiber diameter of 0.5 to 6.0 μm and a bulk density of 0.05 to 0.50 g / cm ³ , an average fiber diameter of 10 to 60 μm, and a bulk. A filter is described in which a fiber sheet having a density of 0.05 to 0.50 g / cm ³ is laminated and formed into an uneven shape having a height of 3 to 100 mm. This filter is used in air cleaners, vacuum cleaners, automobiles, masks, and the like, and is intended to maintain the collection of fine particles over a long period of time. However, there is no disclosure regarding a filter that balances the performances, which suppresses an increase in pressure loss when passing through the filter and has high rigidity and a long use period.

  In Patent Document 2 and Patent Document 3, two or more layers of nonwoven fabric are laminated, the nonwoven fabric disposed on the suction side (outside) is made dense, and the nonwoven fabric disposed on the fan side (inside) is sparse. A simple filter is described. However, there is no disclosure regarding a filter that balances the performances, which suppresses an increase in pressure loss when passing through the filter and has high rigidity and a long use period.

JP-A-4-180808 JP-A-8-24535 JP 2000-218113 A

  Accordingly, an object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a filter having high rigidity and a long use period while suppressing an increase in pressure loss when passing through the filter. Another object of the present invention is to provide a filter capable of adjusting pressure loss, rigidity, and period of use in a balanced manner.

  The present invention is a multilayer filter having a back surface layer composed of a fiber sheet and a surface layer composed of a fiber sheet, wherein the multilayer filter is used such that the back surface layer is located downstream of fluid suction. The back surface layer has a plurality of through holes, and the inter-fiber distance of the back surface layer other than the through holes is longer than the inter-fiber distance of the front surface layer. Is.

  According to the multilayer filter of the present invention, the increase in pressure loss when passing through the filter is suppressed and the rigidity is high, so that looseness and sagging do not occur during attachment, and the collection rate can be increased. Further, according to the multilayer filter of the present invention, it is possible to provide a filter that balances oil retention, pressure loss, rigidity, service life, and the like.

FIG. 1 is a perspective view of a multilayer filter according to this embodiment of the present invention. FIG. 2 is an explanatory diagram for explaining a state in which the multilayer filter shown in FIG. 1 is attached to the frame body of the grease filter. 3 is an end view taken along line X1-X1 of the multilayer filter shown in FIG. FIG. 4A is a schematic diagram showing the flow of fluid in the conventional filter, and FIG. 4B is a schematic diagram showing the flow of fluid in the multilayer filter of the present invention. FIG. 5 is a schematic diagram showing a method for measuring pressure loss. FIG. 6 is a schematic diagram showing how oil droplets are collected when oil-repellent fibers are used as part of the surface layer.

  Hereinafter, the multilayer filter of the present invention will be described based on preferred embodiments with reference to FIGS. In the drawings, the same reference numerals indicate the same components.

  The multilayer filter 1 of this embodiment has the back surface layer 2 which consists of a fiber sheet, and the surface layer 3 which consists of a fiber sheet, as shown in FIG. 1, FIG. The back surface layer 2 and the front surface layer 3 are bonded and integrated or laminated in a non-bonded state. When the back surface layer 2 and the front surface layer 3 are joined and integrated, the joining method of the both is based on the constituent materials of these layers, etc., adhesion by adhesive or fusion by the action of heat, and ultrasonic A known joining means such as fusion is employed.

  The multilayer filter 1 is used so that the back surface layer 2 is located on the downstream side of fluid suction. As shown in FIG. 2, when the multilayer filter 1 is used by being attached to a frame 5 having a shielding part 4, the multilayer filter 1 is attached to the frame 5 so that the back surface layer 2 faces the frame 5. Used. Examples of the frame 5 include a grease filter installed on the air intake side of a range hood, and a member having a grid-like or other shape shield provided in an air conditioner, an exhaust duct, or the like. The shielding part 4 in the frame 5 is a part for constituting a filter in the frame 5. Since this part shields the passage of fluid, it is called the shielding part 4 in the present invention. For example, when the frame body 5 is a grease filter, the grease filter is roughly classified into a baffle type and a mesh type, and the baffle plate of the baffle type grease filter corresponds to the shielding part 4 described above. In the case of the mesh type, the metal part of the punching metal or the expanded metal corresponds to the shielding part 4. The shielding part 4 in the frame provided in an air conditioner, an exhaust duct, or the like refers to, for example, a lattice-shaped part constituting a filter. Note that the frame 5 is not normally provided for mounting a disposable filter such as the laminated filter of the present embodiment, and prevents dust from being sucked or rectified, and the grease filter prevents contamination of the ventilation fan. However, in this application, it is referred to as a frame for convenience. Moreover, the frame 5 is taken out individually from a wall, a ceiling, or the like, and a case where a disposable filter is attached or a case where a disposable filter is attached without being taken out is not limited.

  As shown in FIGS. 1 and 2, the multilayer filter 1 of the present embodiment has a rectangular shape that is long in the X direction shown in FIG. 1. In the multilayer filter 1 of this embodiment, as shown in FIG. 1, it is formed from a back layer 2 and a surface layer 3 having the same shape and the same size. That is, the back layer 2 and the surface layer 3 of the multilayer filter 1 of the present embodiment are also rectangular shapes that are long in the X direction. As shown in FIG. 1, the multilayer filter 1 has a length L1 in the X direction of 260 mm to 1800 mm, and a length W1 in the Y direction (width direction) shown in FIG. 1 is 260 mm to 600 mm. Note that the X direction and the Y direction are orthogonal to each other.

The back surface layer 2 has a plurality of through holes 20. The through-holes 20 are openings penetrating in the thickness direction of the back surface layer 2, and are formed from 25 to 200 per 10 cm ^{2 of the} back surface layer 2 from the viewpoint of maintaining rigidity and strength while reducing pressure loss. It is more preferable that 50 to 100 are formed per 10 cm ² .

  From the viewpoint of maintaining rigidity and strength while reducing pressure loss, and maintaining the amount of oil retained, the opening ratio of the through holes 20 in the back layer 2, that is, the total area of the plurality of through holes 20 is the back layer. The total area of 2 is preferably 10% to 60%, and more preferably 25% to 50%.

  The back surface layer 2 of the present embodiment is formed with uniform circular through-holes 20 arranged at equal intervals in the X direction and the Y direction. That is, in the present embodiment, the back surface layer 2 has circular through holes 20 arranged in parallel in the X direction with a constant interval L3 (4 mm to 14 mm), and forms a straight line in the X direction. These rows are formed side by side with a certain interval in the Y direction. Here, the diameter L of the through hole 20 is preferably 2 to 15 mm, and more preferably 2 to 8 mm, from the viewpoint of maintaining rigidity and strength while reducing pressure loss. Further, in this row, the through-hole 20 is arranged at the same position as the through-hole 20 of the row adjacent in the Y direction. The through-hole 20 forms a straight row in the Y direction, and this row is in the X direction. Are juxtaposed at a certain interval. In addition, although the shape of the through-hole 20 is a uniform circular shape in the present embodiment, it may be an elliptical shape, a triangular shape, a trapezoidal shape, or a combination thereof. In the present embodiment, the through holes 20 are arranged at regular intervals in the X direction or the Y direction, but may be indefinite. Further, the through holes 20 may be arranged in a so-called staggered arrangement so that the through holes 20 are not adjacent to each other in adjacent rows.

  The distance between the fibers of the portion 21 other than the through-hole 20 in the back surface layer 2 is longer than the distance between the fibers of the surface layer 3 described later from the viewpoint of suppressing increase in pressure loss and forming a sparse space. The distance between the fibers of the portion 21 of the back layer 2 is 50 μm to 300 μm from the viewpoint of providing a certain amount of rigidity and strength as a sheet while forming a sparse space while suppressing pressure loss as much as possible. It is preferably 70 μm to 250 μm. The average interfiber distance of the back layer 2 is calculated from the following equation.

また、貫通口２０の設けられた裏面層２０の貫通口２０以外の部分２１の繊維間距離については、計算時に以下の式から算出される裏面層２の見かけの坪量ｗ’を、坪量ｗの代わりに用いて計算を行なっている。

裏面層２の坪量ｗ’＝ｗ × （１００／（１００−ａ））

ここで、ｗ’は裏面層２の見かけの坪量（ｇ／ｍ²）を表し、ｗは裏面層２の実際の坪量（ｇ／ｍ²）を表し、aは裏面層２の開口率（％）を表す。

Moreover, about the interfiber distance of the parts 21 other than the through-hole 20 of the back surface layer 20 in which the through-hole 20 is provided, the apparent basis weight w ′ of the back surface layer 2 calculated from the following formula at the time of calculation is calculated as the basis weight. Calculation is performed using w instead of w.

Basis weight w ′ = w × (100 / (100−a)) of back layer 2

Here, w ′ represents the apparent basis weight (g / m ² ) of the back layer 2, w represents the actual basis weight (g / m ² ) of the back layer 2, and a represents the aperture ratio of the back layer 2. (%).

  The through hole 20 of the back surface layer 2 is larger than the interfiber distance, and the size thereof is 30 of the interfiber distance of the portion 21 other than the through hole 20 in the back surface layer 2 from the viewpoint of sufficiently suppressing an increase in pressure loss. It is preferably at least twice, more preferably at least 35 times. The “size of the through-hole 20” means the diameter L2 (see FIG. 3) in the case of a uniform circular shape as in the present embodiment. It means the length at a large position. From the viewpoint of suppressing an increase in pressure loss, the size of the through hole 20 of the back surface layer 2 is better as it is larger than the inter-fiber distance of the portion 21 of the back surface layer 2, but the breakage of the back surface layer 2 to be described later. From the viewpoint of ensuring strength, rigidity, and elongation, the upper limit is preferably 150 times or less the inter-fiber distance of the portion 21 of the back layer 2.

  The multilayer filter 1 of the present embodiment includes a through-hole 20 and has one of the characteristics of the back surface layer 2 having a high space forming ability. Specifically, as shown in FIG. 4A, in the conventional filter 100, when this is attached to the frame 5 having the shielding part 4, a part of the filter 100 that does not face the shielding part 4. In FIG. 5, the resistance when passing through the frame 5 is small because the fluid flow path is short (indicated by “A” in the figure). However, in the part facing the shielding part 4, the fluid is passed by the shielding part 4. Is blocked, and fluid cannot pass through unless it detours to the part where the shielding part 4 does not exist (indicated by B in the figure). As a result, the flow path of the fluid becomes long, resulting in an increase in passage resistance. For this reason, it is not easy for the conventional filter 100 to ensure a sufficient fluid velocity to collect the target object. On the other hand, as shown in FIG. 4B, in the multilayer filter 1 of the present embodiment, when this is attached to the frame 5 having the shielding part 4, the surface layer 3 and the shielding part of the frame 5. 4, a space S caused by the back surface layer 2 is formed. Due to the presence of the space S, the fluid can easily pass through the frame 5 by shortcutting the space S even in the portion of the multilayer filter 1 facing the shielding portion 4. As a result, the flow path length of the fluid can be made shorter than that shown in FIG. 4A (indicated by B ′ in FIG. 4B), thereby preventing an increase in passage resistance. For this reason, according to the multilayer filter 1 of the present embodiment, it is possible to ensure a sufficient fluid velocity to collect the target object even if the surface layer 3 serving as the collection layer is fine. It becomes.

  The space forming ability of the back surface layer 2 in the present embodiment is represented by the interfiber distance of the portion 21 other than the through hole 20, the area ratio of the through hole 20, and the thickness of the back surface layer 2. The inter-fiber distance of the portion 21 other than the through-hole 20, the area ratio of the through-hole 20, and the back surface layer 2 are judged to be higher in the space forming ability of the back surface layer 2 as the values are larger.

  The thickness of the back surface layer 2 under a load of 50 Pa is preferably 0.5 mm to 12 mm from the viewpoint of suppressing the passage resistance of the air passing through the back surface layer 2 and ensuring a sufficient fluid velocity. More preferably. When the back surface layer 2 and the surface layer 3 are integrated, the thickness is peeled from the multilayer filter 1 so that the through-hole 20 is not crushed, and the thickness is measured at the back surface layer 2 at 10 points. The value obtained by averaging them. The reason for applying a load of 50 Pa when measuring the thickness is that, depending on the material, the back surface layer 2 may be compressed in the thickness direction by the suction force when the fluid is filtered, and the thickness may be crushed. The thickness of the back layer 2 varies depending on the shape of the shielding part to be mounted, but the fluid velocity reaches the upper limit at about 5 mm. Increasing the thickness further does not negatively affect the fluid velocity, but it is impractical to give the thickness more than necessary, and the thickness of the multilayer filter 1 becomes unnecessarily large, so the upper limit is 12 mm. The degree is preferred.

[Measurement method of thickness]
A square-shaped measuring piece having a size of 100 mm in the X direction and 100 mm in the Y direction is cut out. This square-shaped measurement piece cut out is used as a measurement sample. A circular metal plate having a diameter of 5.6 cm and a weight of 12.6 g is placed on the measurement sample, a load of 50 Pa is applied, and the thickness is measured using a laser thickness gauge manufactured by Keyence Corporation. The thickness of layer 2 is assumed.

  The back surface layer 2 suppresses an increase in pressure loss by the through-hole 20 and forms a space between the surface layer 3 and the frame body 5 to increase the rigidity of the multilayer filter 1. It is preferable that the material is not easily deformed when added. As a result of investigations by the present inventors on such properties, it has been found that it is advantageous that the back layer 2 has a high rigidity or breaking strength. Further, it has been found that the back layer 2 is advantageously low in elongation. Specifically, with respect to the rigidity of the back surface layer 2, the rigidity value measured by the cantilever method is preferably 25 mm or more, and more preferably 50 mm or more. Regarding the breaking strength of the back layer 2, the breaking strength value is preferably 1 to 150 N / 25 mm, and more preferably 3 to 100 N / 25 mm. Regarding the elongation, the elongation when a tensile stress of 0.5 N / 25 mm is applied is preferably 1 to 15%, and more preferably 1 to 8%. It is preferable that the rigidity, breaking strength, and elongation satisfy the above range in either the X direction or the Y direction of the back surface layer 2, and more preferably satisfy the above range in both directions. Rigidity, breaking strength and elongation are measured by the following methods. In addition, when measuring each physical property of the back surface layer 2 or the surface layer 3 from the multilayer filter 1, when the back surface layer 2 and the surface layer 3 are integrated, the through-hole 20 is not crushed or the surface layer A measurement sample is obtained by peeling from the laminated filter 1 so that the fiber structure 3 is not broken.

[Measurement of rigidity]
In each of the X direction and the Y direction, it is cut into a width of 20 mm and a length of 150 mm, which is used as a measurement sample, and measured by a cantilever method in accordance with JIS L 1096 8.19.1.

[Measurement method of breaking strength]
A rectangular measuring piece having a size of 100 mm in the X direction and 25 mm in the Y direction is cut out. The cut out rectangular measurement piece is used as a measurement sample. The measurement sample is attached to a chuck of a tensile tester so that the X direction is the tensile direction. The distance between chucks is 50 mm. The measurement sample is pulled at 300 mm / min, and the maximum load point until the sample breaks is defined as the breaking strength of MD. Further, a rectangular measurement piece having a size of 100 mm in the Y direction and 25 mm in the X direction is cut out and used as a measurement sample. This measurement sample is attached to the chuck of a tensile tester so that the Y direction is the tensile direction. The breaking strength in the Y direction is obtained by the same procedure as the method for measuring the breaking strength in the X direction described above.

[Measurement of elongation]
With respect to the X direction and the Y direction, a measurement sample is prepared by the same procedure as described above for [Measurement method of breaking strength], and the measurement sample is attached to a chuck of a tensile tester and pulled. The conditions at this time are also the same as the above-mentioned [Measurement method of breaking strength]. The length of the stretched measurement sample when the load value is 0.5 N is measured, and the elongation at a load of 0.5 N / 25 mm is obtained from the following formula.
Elongation (%) = {(Length when stretched−50) / 50} × 100

  The back surface layer 2 having the through hole 20 has a pressure loss at a portion other than the through hole at a wind speed of 0.8 m / s from the viewpoint of sufficiently increasing the fluid velocity without increasing the pressure loss as the multilayer filter 1. 20 Pa or less, preferably 10 Pa or less. Although the pressure loss of the back surface layer 2 is measured by the back surface layer alone, it is preferably measured in a state where there is no through hole before the through hole is formed. The pressure loss is measured by the following method.

(Measurement of pressure loss)
When measuring the pressure loss by directly attaching the measurement sample to the range hood, the measurement error increases due to the pressure difference between the inside and outside of the duct or the gap between the hoods. As shown in FIG. Measurement is performed using an apparatus that simulates the above. In the modeled device, Showa Denki EC-100T-R313 was used as a blower, and a cylinder with a diameter of 14 cm (area 154 cm ² ) and a length of 95 cm was attached to the front of the blower. A measurement sample is placed on top. In addition, since air is sucked into the cylinder by suction of the blower to generate an air flow, the blower side in the cylinder becomes leeward. In order to measure the pressure difference between the cylinder from the measurement sample to the blower and the cylinder outside, a pressure difference measuring machine (model E8Y-AR2C) manufactured by OMRON Corporation is installed. In this measuring machine, the pressure difference with the outside air outside the cylinder is measured at a position 23 cm leeward from the center of the measurement sample (31 cm above the blower in the cylinder).
Next, using a wind speed measuring machine (model 6541) manufactured by Nippon Kanomax Co., Ltd. as a wind speed measuring machine, with the measurement sample attached, measuring the wind speed at a position 20 cm above the center of the measurement sample, The blower is adjusted so that the wind speed at the position is 0.8 m / s. Under this condition, the pressure difference at a wind speed of 0.8 m / s is measured to determine the pressure loss.
A case where only the measurement sample is attached to the inside of the cylinder and measured is referred to as “single pressure loss”. In addition, when the measurement sample was measured with the frame (using a cross catch filter for Mitsubishi Range Hood V-6037K6-BL cut to a diameter of 14 cm) attached to the inside of the cylinder, Pressure loss ". In these cases, the measurement sample is attached by sealing the periphery so that there is no gap with the inner diameter of the cylinder, but the measurement sample in the cylinder is vented by the seal in a region having a diameter of 13 cm.

  The back layer 2 is preferably composed of a bulky fiber sheet in order to form a space between the surface layer 3 and the frame 5 and to obtain an effect of reducing pressure loss. As the fiber sheet, a nonwoven fabric, a woven fabric, a knitted fabric, a net material, or a composite material thereof can be used. Since the multilayer filter 1 is generally used up, it is preferable to use a non-woven fabric as the fiber sheet in consideration of economy.

When using a nonwoven fabric as the back layer 2, various nonwoven fabrics such as an airlaid nonwoven fabric, an air-through nonwoven fabric, a spunlace nonwoven fabric, a meltblown nonwoven fabric, a spunbond nonwoven fabric, and a chemical bond nonwoven fabric can be used as the nonwoven fabric. Of these nonwoven fabrics, air laid nonwoven fabrics and air-through nonwoven fabrics are preferably used from the viewpoint of bulkiness. Airlaid nonwoven, when using the air-through nonwoven fabric, the fiber diameter of the constituent fibers, it is preferably 15Myuemu～50myuemu, preferably has a basis weight of 10 to 50 g / m ^2, is 10 to 20 g / m ² Is more preferable.

  The through-hole 20 can be formed on a flat sheet using a punch blade, a pin, or the like. Moreover, in the case of a nonwoven fabric, you may form by providing an opening in the process which produces a fiber web, and making it into a sheet, and you may form simultaneously with making a fiber web into a sheet by a water flow etc.

  The surface layer 3 preferably has a fiber-to-fiber distance of 50 μm to 250 μm, and more preferably 60 μm to 150 μm, from the viewpoint of sufficiently collecting the object. The average interfiber distance of the front surface layer 3 is calculated from the above equation similar to the interfiber distance of the back surface layer 2.

  As the fiber sheet constituting the surface layer 3, a nonwoven fabric, a woven fabric, a knitted fabric, a net material, or a composite material thereof can be used. Since the multilayer filter 1 is generally used up, it is preferable to use a non-woven fabric as the fiber sheet in consideration of economy.

  When a nonwoven fabric is used as the surface layer 3, various nonwoven fabrics such as a spunlace nonwoven fabric, an airlaid nonwoven fabric, an air-through nonwoven fabric, a melt blown nonwoven fabric, a spunbond nonwoven fabric, and a chemical bond nonwoven fabric can be used as the nonwoven fabric. Of these nonwoven fabrics, it is preferable to use a spunlace nonwoven fabric from the viewpoint that fibers can be freely selected and flame retardant fibers are easily used. When using a spunlace nonwoven fabric, the fiber diameter of the constituent fibers is preferably 7 μm to 35 μm. Moreover, when an air-through nonwoven fabric or an airlaid nonwoven fabric is used as the surface layer, a bulky nonwoven fabric can be formed, so that pressure loss can be reduced and it can be suitably used. Even when an air-through nonwoven fabric or an airlaid nonwoven fabric is used, the fiber diameter of the constituent fibers is preferably 7 μm to 35 μm. Furthermore, when a chemical bond nonwoven fabric is used as the surface layer, the fibers can be freely selected, bulky, and the flame retardant performance can be improved by adding a flame retardant as a binder. I can do it. Also when using a chemical bond nonwoven fabric, it is preferable that the fiber diameter of a constituent fiber is 7 micrometers-35 micrometers.

The surface layer 3 made of a nonwoven fabric preferably has a basis weight of 20 to 150 g / m ² , particularly 20 to 100 g / m ² . The thickness (under a 50 Pa load) is preferably 0.5 to 10 mm, and more preferably 1 to 5 mm. The thickness of the surface layer 3 is measured in the same manner as the thickness of the back layer 2. The surface layer 3 made of a nonwoven fabric preferably has a pressure loss of 2 to 35 Pa, more preferably 5 to 35 Pa, from the viewpoint of securing the collection property and antifouling property. The pressure loss of the surface layer 3 is measured by the method shown in paragraph [0029] above.

  When the multilayer filter 1 is used as, for example, an oil collecting filter attached to a range hood, as the surface layer 3, a first layer facing outward and a second layer facing the back layer 2 side It is preferable to use those having the surface of the constituent fibers of the second layer having oil repellency, since the oil droplets can be effectively prevented from falling through. The reason for this is as follows.

  FIG. 6 schematically shows a longitudinal section of the surface layer 3 having the above-described configuration. In the surface layer 3, the surface of the fiber F1 existing in a substantially half surface region on one side in the thickness direction has oil repellency, and the surface of the fiber F2 existing in the remaining substantially half surface region has oil repellency. Not. When the surface layer 3 is used with the side where the fiber F2 exists located on the range side (the side facing outward), the oil component A first adheres to the fiber F2 located on the range side as shown in FIG. To do. Since the fiber F2 does not have oil repellency, the oil component A adhering to the fiber F2 spreads on the surface of the fiber F2 and forms an oil film M. The oil component A constituting the oil film M moves in the thickness direction of the surface layer 3 toward the fan side (back surface layer 2 side, frame body 5 side) by capillary action. When the oil component M that moves toward the fan reaches the region where the fiber F1 exists, the oil repellency of the fiber F1 prevents the formation of the oil film M, and also prevents the transfer due to capillary action. As a result, it comes to exist in the state of oil droplets on the surface of the fiber F1, and it becomes difficult for the capillary force to act. As a result, the oil component A is difficult to move to the fan side of the surface layer 3. For this reason, the oil component A can be prevented from falling through.

  In order to make the surface of the fiber F1 have oil repellency, (i) a non-woven fabric is prepared using fibers not having an oil repellant, and then a resin to which an oil repellant or an oil repellant is added is applied. And (b) a method for producing the surface layer 3 using an oil-repellent fiber. In the case of (a), for example, the surface of the fiber may be coated with a fluorine-based oil repellent to impart oil repellency.

  In order to coat the surface of the fiber F1 with a fluorine-based oil repellent, for example, a fluororesin emulsion may be applied to the fiber surface and dried. As a result, the fluororesin can be adhered to the surface of the fiber in a film form. By performing heat treatment after drying, the adhesion of the fluororesin attached to the fiber surface can be enhanced. In order to apply the fluororesin emulsion to the fiber surface, for example, the emulsion may be dipped (impregnated), sprayed and sprayed, or the emulsion is foamed. As other methods, the surface of the fiber can be fluorinated to impart oil repellency by using diluted fluorine gas, low temperature plasma, or sputtering by glow discharge.

  Fluororesin includes tetrafluoroethylene resin, tetrafluoroethylene / perfluoropropyl vinyl ether copolymer, tetrafluoroethylene / hexafluoropropylene copolymer, chlorotrifluoroethylene resin, ethylene / tetrafluoroethylene copolymer, fluoride Vinylidene resin, vinyl fluoride resin, hexafluoropropylene / vinylidene fluoride copolymer, polyimide-modified fluorine resin, PPS-modified fluorine resin, epoxy-modified fluorine resin, PES-modified fluorine resin, phenol-modified fluorine resin, Examples include acrylate polymers and methacrylate copolymers having a perfluoroalkylethylene group. Also, a fluororesin emulsion can be used. As such an emulsion, Asahi Guard (registered trademark) AG-7000, which is a fluorine resin manufactured by Asahi Glass, for example, can be used.

  The amount of the fluororesin attached is preferably 0.1 to 10% by weight, particularly 0.5 to 2% by weight, based on the weight of the fiber before the fluororesin is attached. By setting the adhesion amount to 0.5% by weight or more, sufficient oil repellency can be imparted to the fiber surface. Moreover, the fall of the air permeability of the filter resulting from excessive adhesion is prevented by making adhesion amount into 10 weight% or less.

  When the fiber itself is made of a material having oil repellency, the above-described various fluororesins can be used as the material.

  As the oil repellent used for the oil repellent treatment, a part of the surfactant can be used in addition to the fluorine-based oil repellent. Such a surfactant can exhibit oil repellency by applying it to a nonwoven fabric and drying it. For example, the oil repellency can be imparted to the fiber by applying a nonionic surfactant, alkyl glucoside, and an amphoteric surfactant, lauramidopropyl betaine, to a nonwoven fabric and drying. In addition, among the fibers in which an oil containing fluorine is applied to the surface, there are fibers in which the fiber surface exhibits oil repellency by heating, and such fibers can also be used in the present invention. Examples of such fibers include Ube Nitto's ultra-oil-repellent nonwoven cotton and UC fiber HR-PLE.

  Examples of the fibers used when producing a nonwoven fabric using oil-repellent fibers include fibers in which fluorine is kneaded and fibers made of a fluororesin. Examples of such fibers include Toyoflon (registered trademark), which is a fluorine fiber manufactured by Toray, and Teflon (registered trademark) manufactured by DuPont.

  The oil-repellent surface layer 3 can be manufactured, for example, by the following method. First, the surface layer 3 is formed using fibers having no oil repellency, and a fluororesin emulsion is applied by spraying from one side. Thereafter, the drug is dried by heat.

  The multilayer filter 1 of the present embodiment having the above configuration is particularly useful as an oil collecting filter for a range hood as described above, and is also useful as a gas filter such as an air conditioner filter or an exhaust duct filter. It is. In the multilayer filter 1 of the present embodiment, the air permeability of the multilayer filter 1 is governed by the air permeability of the surface layer 3 because the surface layer 3 has a lower air permeability than the back surface layer 2. Therefore, the air permeability of the multilayer filter 1 is substantially the same as the air permeability of the surface layer 3.

  The constituent fibers constituting the fiber sheets of the back layer 2 and the surface layer 3 are non-flammable fibers or flame retardant fibers from the viewpoint of safety when used as an oil collecting filter for a ventilation fan or a range hood. It is preferable. As the incombustible fiber, glass fiber, carbon fiber, etc. can be used. As the incombustible fiber, polyvinyl chloride, polyvinylidene chloride, polyclar, flame retardant polyester, flame retardant acrylic, flame retardant rayon, flame retardant polypropylene. It is preferable to use flame retardant polyethylene, flame retardant polylactic acid, or the like. Alternatively, it is preferable to blend incombustible fiber and / or flame retardant fiber. A flame-retardant fiber is a fiber having a LOI value of 26 or more.

  When the constituent fibers of the back layer 2 and the surface layer 3 are not incombustible fibers or flame retardant fibers, or when the flame resistance is insufficient even if they are incombustible fibers or flame retardant fibers, a post-processing step Alternatively, a halogen-based or phosphorus-based flame retardant may be applied to the fiber, or a polyboric acid flame retardant may be applied to the fiber. Alternatively, the coating may be formed by applying a resin containing a flame retardant to the fiber surface as a binder.

  When the constituent fibers of the back surface layer 2 and the surface layer 3 do not have to be non-combustible fibers or flame retardant fibers, synthetic fibers made of synthetic resin for forming fibers known as the constituent fibers, such as polyethylene, polypropylene, polybutylene For example, fibers made of polyolefin materials such as polyethylene terephthalate, polyester materials such as polybutylene terephthalate, polyamide materials such as nylon 6 and nylon 66, polyacrylonitrile materials, rayon, various rubbers and the like can be used. Further, it is also possible to use a vinyl material such as polyvinyl chloride, or a fiber made of vinylidene such as polyvinylidene chloride. Further, fibers made of modified materials, alloys, or mixtures of these materials can also be used. Since it is a carbon neutral fiber, it has a low environmental impact, so polylactic acid fiber can also be used suitably.

  The multilayer filter 1 formed by laminating the back surface layer 2 and the surface layer 3 described above can suppress an increase in pressure loss when passing through the filter and has high rigidity, so that the collection rate can be increased. The rigidity of the formed multilayer filter 1 is preferably 50 mm or more, and more preferably 70 mm or more. Since the formed multilayer filter 1 has high rigidity, it can be attached in close contact with the frame 5 without causing looseness. The rigidity of the multilayer filter 1 was measured by a cantilever method in accordance with JIS L 1096 8.19.1 using the laminated filter 1 cut into a width of 20 mm and a length of 150 mm in each of the X direction and the Y direction. The rigidity preferably satisfies the above range in either one of the X direction and the Y direction of the multilayer filter 1, and more preferably satisfies the above range in both directions.

  The formed multilayer filter 1 has a breaking strength value of preferably 1 to 150 N / 25 mm, and more preferably 3 to 100 N / 25 mm, with respect to its breaking strength. Since the formed multilayer filter 1 has high breaking strength, it is difficult to be deformed when an external force is applied, and can be attached in close contact with the frame 5. The breaking strength of the multilayer filter 1 is measured by the same method as that for the back layer 2. Regarding the elongation, the elongation when a tensile stress of 0.5 N / 25 mm is applied is preferably 1 to 15%, and more preferably 1 to 8%. The elongation preferably satisfies the above range in one of the X direction and the Y direction of the multilayer filter 1, and more preferably satisfies the above range in both directions. Since the formed multilayer filter 1 has a lower elongation than the case of the surface layer 3 alone, it is not easily deformed when an external force is applied, and can be attached in close contact with the frame 5.

The formed multilayer filter 1 is preferably 5 to 40 Pa, and more preferably 10 to 35 Pa, from the viewpoint of securing the collection property and antifouling property with respect to the pressure loss of the single unit.
Moreover, the formed multilayer filter 1 is preferably 5 to 50 Pa and preferably 10 to 40 Pa in terms of pressure loss when the frame is attached, from the viewpoint of securing collection and antifouling properties. Further preferred.

The effects of the multilayer filter 1 according to the embodiment of the present invention described above when used with the back surface layer 2 positioned on the downstream side of the fluid suction (the frame body 5 side) will be described.
As shown in FIGS. 1 and 3, the multilayer filter 1 of the present embodiment is a laminate of a back surface layer 2 and a surface layer 3, so that the amount of oil retained can be increased and the rigidity can be increased. Since it becomes high, it is hard to loosen and sag at the time of attachment to the frame 5, and the oil collection rate can be increased. In the multilayer filter 1 of the present embodiment, as shown in FIG. 1 and FIG. 3, the back surface layer 2 has a plurality of through holes 20, and the portion 21 other than the through holes 20 in the back surface layer 2. Since the inter-fiber distance is longer than the inter-fiber distance of the surface layer 3 disposed on the side facing outward, an increase in pressure loss when passing through the filter can be suppressed. Furthermore, the multilayer filter 1 of this embodiment controls the size of the through-hole 20 of the back surface layer 2, the area ratio of the through-hole 20, and the like so that the balance of oil retention, pressure loss, rigidity, service life, etc. is balanced. A filter can be provided.

  The multilayer filter of the present invention is not limited to the above-described embodiment, and can be changed as appropriate. For example, when the laminated filter is used as an oil collecting filter for a range hood, only the surface layer 3 on the stove side may be composed of non-combustible fibers or flame retardant fibers.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited to such examples.

[Example 1]
(1) Back surface layer An air-through nonwoven fabric having a basis weight of 40 g / m ² was used. This nonwoven fabric was composed of a core-sheath type composite fiber (fiber diameter: 17.5 μm) whose core was polypropylene and whose sheath was polyethylene. On this nonwoven fabric, through-holes having a diameter of 8 mm were formed with a punch blade at an opening ratio of 25% (50 per 10 cm ² ). The non-woven fabric after forming the through-hole has a thickness of 2.16 mm under a load of 50 Pa, a breaking strength in the MD direction (fiber flow direction) and CD direction (direction perpendicular to the fiber flow direction) is 14.6 N / 25 mm, respectively. 3.3 N / 25 mm, MD and CD elongations of 1.5% and 3.1%, the distance between fibers other than the through hole is 85.3 μm, and the pressure loss of the part other than the through hole is 17 The basis weight was 30 g / m ² .

(2) Surface layer A spunlace nonwoven fabric having a basis weight of 40 g / m ² was used. This nonwoven fabric was composed of propylene fibers (fiber diameter: 15.5 μm). The nonwoven fabric had a thickness of 1.77 mm, a fiber-to-fiber distance of 71.2 μm, and a pressure loss of 31.0 Pa under a 50 Pa load.

(3) Multilayer filter The obtained back surface layer and the back surface layer were stacked and melt-fused and integrated by placing them in a dryer set at 142 ° C. for 10 minutes. As a result, the intended multilayer filter was obtained.

[Examples 2 to 4]
A multilayer filter was obtained in the same manner as in Example 1 except that those shown in Table 1 were used as the back layer.

Example 5
A laminated filter was obtained in the same manner as in Examples 1 and 2, except that the nonwoven fabric shown below was used as the back layer.
(1) Back surface layer An air-through nonwoven fabric having a basis weight of 15 g / m ² was used. This non-woven fabric was composed of a core-sheath type composite fiber (fiber diameter 30 μm) whose core was polypropylene and whose sheath was polyethylene, and was further strengthened by calendering. On this nonwoven fabric, through-holes having a diameter of 8 mm were formed with a punch blade at an opening ratio of 25% (50 per 10 cm ² ). The non-woven fabric after the formation of the through hole has a thickness of 0.54 mm under a load of 50 Pa, and a breaking strength in the MD direction (fiber flow direction) and CD direction (direction perpendicular to the fiber flow direction) is 4.4 N / 25 mm, respectively. 1.9 N / 25 mm, MD direction and CD direction elongations of 2.1% and 6.9%, the distance between fibers other than the through hole is 154.1 μm, and the pressure loss of the part other than the opening is 3 The basis weight was 11.3 g / m ² .

Example 6
A laminated filter was obtained in the same manner as in Examples 1 to 3 except that the nonwoven fabric shown below was used as the back layer.
(1) Back surface layer An air-through nonwoven fabric having a basis weight of 40 g / m ² was used. This nonwoven fabric was composed of side-by-side type composite fibers (fiber diameter 42 μm) made of polypropylene and polyethylene. On this nonwoven fabric, through-holes having a diameter of 8 mm were formed with a punch blade at an opening ratio of 25% (50 per 10 cm ² ). The nonwoven fabric after the formation of the through-hole has a thickness of 2.48 mm under a load of 50 Pa, a breaking strength in the MD direction (fiber flow direction) and CD direction (direction perpendicular to the fiber flow direction) is 1.3 N / 25 mm, respectively. 1.0 N / 25 mm, MD and CD elongations of 8.1% and 9.9%, the distance between fibers other than the through-hole is 226 μm, and the pressure loss of the part other than the opening is 4.1 Pa. The basis weight was 30 g / m ² .

Example 7
A laminated filter was obtained in the same manner as in Example 4 except that the nonwoven fabric shown below was used as the surface layer.
(1) Surface layer An air-through nonwoven fabric having a basis weight of 34 g / m ² was used. This nonwoven fabric was composed of a core-sheath type composite fiber (fiber diameter: 17.5 μm) whose core was polypropylene and whose sheath was polyethylene. The nonwoven fabric had a thickness of 0.9 mm, a fiber-to-fiber distance of 60.7 μm, and a pressure loss of 15.9 Pa under a 50 Pa load.

Example 8
A multilayer filter was obtained in the same manner as in Examples 4 and 5 except that the nonwoven fabric shown below was used as the surface layer.
(1) Surface layer A chemical bond nonwoven fabric having a basis weight of 34 g / m ² was used. This nonwoven fabric was composed of polypropylene fibers (fiber diameter 27 μm). The nonwoven fabric had a thickness of 1.5 mm, a fiber-to-fiber distance of 160.2 μm, and a pressure loss of 3.3 Pa under a 50 Pa load.

[Comparative Example 1]
The multilayer filter of Comparative Example 1 was obtained using only the same surface layer as in Example 1 as shown in Table 2 without providing the back layer.

[Comparative Examples 2 to 4]
The multilayer filters of Comparative Examples 2 to 4 were obtained using the back surface layer having the physical properties shown in Table 2 without providing a through hole in the back surface layer.

[Comparative Examples 5 and 6]
The multilayer filters of Comparative Examples 5 and 6 were obtained using only the same surface layer as in Examples 7 and 8 without providing the back layer.

[Comparative Examples 7 and 8]
The multilayer filters of Comparative Examples 7 and 8 were obtained using the back surface layer having the physical properties shown in Table 2 without providing a through hole in the back surface layer.

[Evaluation]
About the multilayer filter obtained by the Example and the comparative example, the rigidity of each MD direction and CD direction, elongation, and breaking strength were measured. Moreover, about the laminated filter obtained by the Example and the comparative example, the oil retention amount, the single-piece | unit pressure loss, and the pressure loss at the time of frame attachment were measured with the following method.

<Measurement of oil retention>
The weights of the multilayer filters obtained in Examples and Comparative Examples were measured, and then each multilayer filter was completely immersed in Nisshin Canola Oil (registered trademark) manufactured by Nisshin Oillio Group Co., Ltd. It was taken out from the clean canola oil (registered trademark), suspended in a vertical state, and weighed after 8 hours. The amount of oil retained was determined by subtracting the initial weight of the multilayer filter from the weight of the multilayer filter after oil retention. The oil retention amount is a value obtained by measuring two points and averaging them.

As is clear from the results shown in Tables 1 and 2, the laminated filters of Examples 1 to 4 have a maximum pressure loss increase of 6 Pa compared to the filter of Comparative Example 1, and the rectifying effect when attached to the frame. As a result, the rigidity is improved by more than 3 times in the CD direction and the oil collection amount is also improved by about 1.5 times, and the rigidity and the collection amount are suppressed while suppressing an increase in pressure loss. It has improved. Moreover, although the laminated filter of Examples 1-4 compared with the filter of the comparative example 2, although the rigidity and the oil collection amount are reducing, the pressure loss is also reduced by 10 Pa or more alone, and the balance is good. It is a filter with performance. Further, as is apparent from the physical properties of Examples 1 to 4, it is possible to adjust the rigidity, pressure loss, and oil retention amount to desired values by adjusting the size and area ratio of the through holes.
In addition, as is clear from Examples 5 and 6 shown in Table 1 and Comparative Examples 1, 3, and 4 shown in Table 2, the pressure can be similarly obtained by using non-woven fabrics having different types of openings in the back layer. It is possible to design a filter with a well-balanced performance with high rigidity and oil retention while suppressing an increase in loss.
Further, as is clear from Examples 7 and 8 shown in Table 1 and Comparative Examples 5 to 8 shown in Table 2, even when different types of non-woven fabrics are used for the surface layer, the increase in pressure loss is similarly suppressed. Also, it is possible to design a filter with high balance and high rigidity and oil retention.
As a result, the filter of each example is less likely to loosen when attaching the range hood filter to the grease filter while maintaining ventilation performance compared to the filter of each comparative example, and can be used for a long time. Can provide a simple filter. In addition, it is possible to create a filter having pressure loss, rigidity, and oil retention amount according to the usage scene.

DESCRIPTION OF SYMBOLS 1 Multilayer filter 2 Back surface layer 20 Through-hole 21 Portion other than the through-hole of a back surface layer 3 Surface layer 4 Shielding part 5 Frame

Claims (7)

A multilayer filter having a back surface layer made of a fiber sheet and a surface layer made of a fiber sheet,
The multilayer filter is used such that the back surface layer is located on the downstream side of fluid suction,
The back layer has a plurality of through holes,
A multilayer filter in which the inter-fiber distance of the portion other than the through hole in the back layer is longer than the inter-fiber distance of the surface layer.   2. The multilayer filter according to claim 1, wherein the size of each through hole is 30 times or more the inter-fiber distance of a portion other than the through hole in the back surface layer.   The multilayer filter according to any one of claims 1 and 2, wherein the multilayer filter has a rigidity measured by a cantilever method specified in JIS L 1096 of 50 mm or more.   The multilayer filter according to any one of claims 1 to 3, wherein an aperture ratio of the through hole in the back layer is 10 to 60%.   The multilayer filter according to claim 1, wherein the back surface layer has a thickness of 0.5 to 12.0 mm under a 50 Pa load.   The laminated filter according to any one of claims 1 to 5, wherein the fiber sheet of each of the back layer and the surface layer is a non-combustible fiber or a flame retardant fiber.   The multilayer filter according to claim 1, wherein the multilayer filter is used as a filter for a range hood or a ventilation fan.

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