JP2021007929A - Multilayer composite filter medium and production method of the same - Google Patents

Abstract

To provide a multilayer composite filter medium improved with filtration performance and filtration life, and a production method of the same.SOLUTION: A multilayer composite filter medium having a principal surface includes: a paper base material 1 having a first average pore diameter; a nano-coated layer 2 containing nanofibers formed on the top surface of the base material 1; and a nonwoven fabric layer 3 disposed on the top surface of the base material 1 formed with the nano-coated layer 2 and made of a nonwoven fabric having a second average pore diameter larger than the first average pore diameter. The nonwoven fabric layer 3 is fixed to the base material 1 via a plurality of fixing regions 5 separately arranged so that the average fiber diameter of the nanofibers forming the nano-coated layer 2 is smaller than the average fiber diameter of fibers forming the base material 1 and the nonwoven fabric layer 3 and a gap 4 is formed between the nonwoven fabric layer 3 and the nano-coated layer 2.SELECTED DRAWING: Figure 1

Description

The present invention relates to a multilayer composite filter medium in which multiple layers are laminated.

Various filter media are used as filters for engine air, oil, and fuel. This type of filter medium is required to improve the amount of dust trapped and extend the life cycle. In particular, in recent years, engines are required to be smaller and lighter, and the area of the filter medium tends to be smaller accordingly. Therefore, higher performance is required to exhibit filtration performance in a limited area. There is.

As existing technology, a multi-layered filter medium (see Patent Document 1) in which a non-woven fabric as a coarse layer arranged on the upstream side and a filter paper as a dense layer arranged on the downstream side are joined, and a nanofiber layer on the surface of the filter paper. A method has been proposed in which a filter medium is formed into multiple layers (see Patent Document 2). In these filter media, the former has a feature that the trapping amount is greatly improved, and the latter has a feature that the filtration efficiency is greatly improved, but they are not compatible with each other.

Japanese Unexamined Patent Publication No. 2011-45825 Japanese Unexamined Patent Publication No. 2015-51434

The present invention has been developed in view of the above problems, and one of the objects of the present invention is to provide a multilayer composite filter medium having improved filtration performance and filtration life, and a method for producing the same.

Means for Solving Problems and Effects of Invention

The multilayer composite filter medium according to the first side surface of the present invention is a multilayer composite filter medium having a main surface, which is formed on a paper base material having a first average pore diameter and an upper surface of the base material. A non-woven fabric layer including a nano-coated layer containing nanofibers and a non-woven fabric having a second average pore diameter larger than the first average pore diameter, which is arranged on the upper surface side of the base material on which the nano-coated layer is formed, is provided. The average fiber diameter of the nanofibers forming the nanocoat layer is smaller than the average fiber diameter of the fibers forming the base material and the non-woven fabric layer, so that a gap is formed between the non-woven fabric layer and the nanocoat layer. The non-woven fabric layer is fixed to the base material via a plurality of fixed regions provided apart from each other.

With the above configuration, dust having a large particle size can be captured on the coarse non-woven fabric layer, and dust having a small particle size that has passed through the non-woven fabric layer can be captured by the nanocoat layer and collected in the voids of the filter medium. It is possible to extend the service life while suppressing clogging.

In addition to the above configuration, the multilayer composite filter medium according to the second side surface of the present invention has a first cake layer for forming a first cake layer in which dust trapped by the nonwoven fabric layer is aggregated on the upper surface of the nonwoven fabric layer. A one-cake layer forming region is formed, and a second cake layer forming region is formed in the voids to form a second cake layer in which dust captured by the nanocoat layer is aggregated.

With the above configuration, a first cake layer that mainly traps large particles of dust is formed on the coarse non-woven fabric layer, and a second cake layer that captures smaller dust particles is formed in the voids. Dust of different sizes can be efficiently captured to improve filtration performance and filtration life.

In the multilayer composite filter medium according to the third aspect of the present invention, in addition to any of the above configurations, the plurality of fixed regions are formed on the main surface of the multilayer composite filter medium at points. ing. With the above configuration, it is possible to form a wide void between the non-woven fabric layer and the nanocoat layer while preventing a decrease in filtration performance.

In the multilayer composite filter medium according to the fourth aspect of the present invention, in addition to any of the above configurations, the total area of the plurality of fixed regions is 20% with respect to the area of the main surface of the multilayer composite filter medium. It is as follows.

In the multilayer composite filter medium according to the fifth aspect of the present invention, in addition to any of the above configurations, the fixed region is formed by any of ultrasonic heat welding, hot melting, and thermocompression bonding.

In the multilayer composite filter medium according to the sixth aspect of the present invention, in addition to any of the above configurations, the base material is composed of a wet paper-made paper sheet, and the paper sheet comprises this. The fiber diameter of the fibers to be formed is 100 μm or less, the average fiber diameter is 1 μm to 80 μm, and the first average pore diameter is 0.5 μm to 200 μm.

In the multilayer composite filter medium according to the seventh aspect of the present invention, in addition to the above configuration, the base material impregnates the whole or a part of the paper sheet with a resin. By impregnating the paper sheet with resin and processing the paper in this way, the paper sheet can be made stronger.

In the multilayer composite filter medium according to the eighth side surface of the present invention, in addition to the above configuration, the base material is impregnated with a resin from the first surface side of the paper sheet, and the nanocoat layer is formed on the second surface. It is provided. With the above configuration, it is possible to obtain an advantage that an increase in initial pressure loss can be suppressed while reinforcing the paper sheet with resin.

In the multilayer composite filter medium according to the ninth aspect of the present invention, in addition to any of the above configurations, the nonwoven fabric constituting the nonwoven fabric layer has an average fiber diameter of 0.5 μm to 100 μm. The second average pore diameter is 1 μm to 600 μm.

In the multilayer composite filter medium according to the tenth aspect of the present invention, in addition to any of the above configurations, the non-woven fabric layer is formed by melt blowing.

In the multilayer composite filter medium according to the eleventh aspect of the present invention, in addition to any of the above configurations, the nanocoat layer has a fiber diameter of the nanofibers of 20 nm to 1000 nm.

In the multilayer composite filter medium according to the twelfth aspect of the present invention, in addition to any of the above configurations, the nanocoat layer is formed by an electrospinning method or an electrobubble spinning method.

In the multilayer composite filter medium according to the thirteenth aspect of the present invention, in addition to any of the above configurations, the base material is corrugated. With the above configuration, the surface area of the base material can be widened to improve the dust trapping performance, and by forming the base material in a corrugated shape, the volume of the voids can be increased to increase the amount of dust trapped, resulting in filtration performance. The filtration life can be extended.

In the multilayer composite filter medium according to the fourteenth aspect of the present invention, the surface of the base material is embossed in addition to any of the above configurations. With the above configuration, the surface area of the base material can be increased to improve the dust trapping performance, and the surface of the base material can be provided with irregularities to increase the volume of the voids and increase the amount of dust trapped, resulting in filtration performance. And the filtration life can be extended.

The multi-layer composite filter medium according to the fifteenth aspect of the present invention includes an air filter for an engine, an oil filter, a fuel filter, a filter for air conditioning equipment, a filter for hydraulic equipment, a filter for discharge processing equipment, a filter for a compressor, and a process filter. It is either.

The method for producing a multilayer composite filter medium according to the 16th aspect of the present invention includes a substrate preparation step of preparing a paper substrate having a first average pore diameter and coating nanofibers on the upper surface of the substrate. In the nanocoating step of forming the nanocoat layer, a non-woven fabric having a second average pore diameter larger than the first average pore diameter is arranged on the upper surface side of the base material on which the nanocoat layer is formed to form the non-woven fabric layer. A bonding step of fixing the non-woven fabric layer to the base material by providing a plurality of fixing regions at intervals so as to form a gap between the non-woven fabric layer and the nanocoat layer. There is.

By the above method, dust having a large particle size is collected on a coarse non-woven fabric layer, and dust having a small particle size that has passed through the non-woven fabric layer is captured by a nanocoat layer and collected in voids, thereby forming a filter medium mesh. It is possible to provide a multilayer composite filter medium capable of extending the life while suppressing clogging.

In the method for producing the multilayer composite filter medium according to the seventeenth aspect of the present invention, in addition to the above method, the base material preparation step includes a paper making step of wet-making a paper sheet constituting the base material and the paper making. It includes a resin processing step of impregnating the resin from the first surface side of the paper sheet made in the step, and in the nanocoating step, the nanocoat layer is formed on the second surface of the paper sheet. ..

In the method for producing a multilayer composite filter medium according to the eighteenth aspect of the present invention, in addition to any of the above methods, in the joining step, the plurality of fixed areas are pointed on the main surface of the multilayer composite filter medium. The plurality of fixed regions are provided so as to be separated from each other so that the total area of the plurality of fixed regions is 20% or less of the area of the main surface of the multilayer composite filter medium.

It is a schematic enlarged sectional view of the multilayer composite filter medium which concerns on one Embodiment of this invention. It is a schematic cross-sectional view which shows the state which the multilayer composite filter medium shown in FIG. 1 has captured dust. It is a top view of the multilayer composite filter medium which concerns on one Embodiment of this invention. It is a top view of the multilayer composite filter medium which concerns on other embodiment of this invention. It is a schematic enlarged sectional view of the multilayer composite filter medium which concerns on other embodiment of this invention. It is a schematic enlarged sectional view of the multilayer composite filter medium which concerns on other embodiment of this invention. It is a process diagram which shows the manufacturing process of the multilayer composite filter medium shown in FIG. It is a graph which shows the measurement result of a pressure difference and a dust holding amount. It is a graph which shows the measurement result of a pressure difference and a dust collection efficiency. It is a graph which shows the measurement result of the dust size and the dust collection efficiency.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments shown below are examples for embodying the technical idea of the present invention, and the present invention is not limited to the following. Further, the present specification does not specify the member shown in the claims as the member of the embodiment. In particular, the dimensions, materials, shapes, relative arrangements, and the like of the components described in the embodiments are not intended to limit the scope of the present invention to the specific description, and are merely explanatory examples. It's just that. The size and positional relationship of the members shown in each drawing may be exaggerated to clarify the explanation. Further, in the following description, members of the same or the same quality are shown with the same name and reference numeral, and detailed description thereof will be omitted as appropriate. Further, each element constituting the present invention may be configured such that a plurality of elements are composed of the same member and the plurality of elements are combined with one member, or conversely, the function of one member is performed by the plurality of members. It can also be shared and realized.

The multilayer composite filter medium according to the present invention is mainly used for filtering air and oil around an automobile engine or filtering fuel to remove dust, for example, an air filter for an engine, an oil filter, and a fuel. Used for filters, etc. Further, the multi-layer composite filter medium according to the present invention is not limited to automobiles, and the application is not limited to automobiles, and air conditioning equipment filters, hydraulic equipment filters, discharge processing equipment filters, compressor filters, process filters, air conditioner filters, and air purifiers. It can also be used as a machine filter or the like.

[Embodiment 1]
The multilayer composite filter medium according to the embodiment of the present invention is shown in the enlarged cross-sectional views of FIGS. 1 and 2. The multilayer composite filter medium 100 shown in FIG. 1 is a filter medium having a main surface, and is formed of a paper base material 1, a nanocoat layer 2 formed on the upper surface of the base material 1, and a nanocoat layer 2. It includes a non-woven fabric layer 3 arranged on the upper surface of the base material 1. The base material 1 has a first average pore diameter. The nanocoat layer 2 contains nanofibers. The non-woven fabric layer 3 is a non-woven fabric having a second average pore diameter larger than the first average pore diameter. Further, in the multilayer composite filter medium 100, the non-woven fabric layer 3 is used as the base material 1 via a plurality of fixed regions 5 provided apart from each other so as to form a gap 4 between the non-woven fabric layer 3 and the nanocoat layer 2. It is fixed.

In this specification, the method for measuring the average pore diameter of the base material 1 and the non-woven fabric layer 3 is determined by the bubble point method (ASTM F316-86, JIS K 3832). Further, in the following, as a method for measuring the average fiber diameter of the fibers forming each layer of the multilayer composite filter medium, 10 points are randomly selected from a plane of 4 mm × 3 mm by observation with a scanning electron microscope (SEM), and the fiber width is selected. Is measured, and this is performed 10 times, and the average value of a total of 100 points is taken as the average fiber diameter.

The multi-layer composite filter medium 100 is formed in a sheet shape as a whole, and has a structure in which an object to be filtered such as air or oil is passed in a direction substantially perpendicular to a main surface spreading in a plane to be filtered. The multilayer composite filter medium 100 is used in a state where the non-woven fabric layer 3 is arranged on the upstream side and the base material 1 is arranged on the downstream side in the flow direction of the object to be filtered indicated by the arrow in FIG.

(Base material 1)
The base material 1 is a paper filter paper, and is formed so that the first average pore diameter, which is the filter pore diameter, is, for example, 0.5 μm to 200 μm, preferably 1 to 100 μm. The base material 1 shown in FIG. 1 is composed of a wet-made paper sheet 1A. A filter paper composed of a wet-made paper sheet 1A is preferable because it can realize characteristics excellent in filtration performance and durability. The base material 1 can be reinforced by impregnating the paper sheet 1A with a resin.

(Paper sheet 1A)
In the paper sheet 1A to be wet-made, organic fibers such as cellulose fibers, regenerated cellulose fibers, and synthetic fibers are used as the main fibers. The cellulose fiber may be either a natural fiber such as pulp or a chemical fiber (recycled fiber) such as rayon. As the synthetic fiber, a fiber made of a synthetic resin, for example, PET fiber or the like can be used. These fibers can be used alone or in combination as the main fiber. In addition, a binder fiber can be mixed with the main fiber of the paper sheet 1A in order to impart strength. The binder fiber is a synthetic fiber having a lower melting point than the cellulose fiber (for example, 80 ° C. to 160 ° C.), and is, for example, a polyethylene fiber, a polyester fiber, a polyvinyl alcohol fiber, or the like, and these may be used alone or in combination. Can be done. Alternatively, an inorganic fiber such as glass fiber may be mixed with the main fiber of the paper sheet 1A. Further, the paper sheet 1A can be mixed with an inorganic powder. As such an inorganic powder, potassium titanate, calcium carbonate, basic magnesium sulfate, carbon powder and the like can be used.

The first average pore diameter, which is the pore diameter of the base material 1, can be controlled by, for example, adjusting the fiber diameter, blending ratio, or basis weight of the main fiber to be used. The first average pore diameter of the base material 1 tends to increase as more fibers having a large fiber diameter (for example, an average fiber diameter of 30 μm or more) are blended and as the basis weight decreases. On the contrary, the more fibers having a small fiber diameter (for example, the average fiber diameter is 5 μm or less) are blended, and the larger the basis weight is, the smaller the first average pore diameter of the base material 1 tends to be.

The basis weight of the base material 1 is not particularly limited, but if the basis weight is too small, the strength of the base material 1 may decrease, resulting in insufficient strength when used as a filter medium. Further, if the basis weight is too large, the thickness of the entire filter medium becomes too large, and the pressure loss during use tends to be large, which may shorten the filtration life. Therefore, the basis weight of the base material 1 is determined in consideration of these factors.

From the above, in the paper sheet 1A, the fiber diameter of the main fiber is 100 μm or less in order to set the first average pore diameter, which is the filter pore diameter, to 0.5 μm to 200 μm, preferably 1 to 100 μm. The average fiber diameter is 1 μm to 80 μm, preferably 5 μm to 50 μm, and the amount of graining, which is the mass per unit area, is 10 to 500 g / m ² , preferably 80 to 250 g / m ² .

(Resin processing)
The paper sheet made into a sheet can be impregnated with resin by resin processing in order to have strength. In the resin processing, for example, the paper sheet 1A is moved while being pressed against the outer peripheral surface of the rotating roll, and the liquid resin material applied to the surface of the roll is transferred to the surface of the paper sheet 1A. To do. As this resin material, for example, an emulsion type can be used, and the resin material is applied to the paper sheet 1A and impregnated into the whole or a part of the paper sheet 1A. The resin impregnated in whole or in part of the paper sheet 1A is dried to reinforce the paper sheet 1A from the inside. As such a resin, for example, phenol, bisphenol, epoxy, melamine, acrylic, vinyl acetate and the like can be used.

The paper sheet can be impregnated with resin from, for example, one side surface (lower surface in the drawing) side. At this time, the resin impregnated in the paper sheet can be impregnated in the entire inside of the sheet, but can also be impregnated in a part thereof. For example, when the paper thickness is large or the amount of resin impregnated is small, a portion not impregnated with the resin is formed, and a part of the paper sheet, to be exact, only the first surface side can be impregnated. In this way, when only one side of the paper sheet is processed with resin, by adjusting the degree of resin infiltration, it is possible to create a gradient in the amount of resin applied in the thickness direction, which can also reduce pressure loss. it can. The base material 1 impregnated with the resin from the first surface (lower surface in the figure) of the paper sheet 1A can be provided with the nanocoat layer 2 on the second surface (upper surface in the figure) on the opposite side. This base material 1 is impregnated with resin from the first surface side of the paper sheet 1A, which is the downstream side of the object to be filtered, to reinforce the sheet 1A, and the dust captured by the paper sheet 1A is moved to the downstream side. It can be effectively prevented from being discharged.

In the above resin processing, if the resin application amount is too large with respect to the fiber basis weight amount, the paper sheet becomes dense, the pressure loss increases, and the dust retention amount may decrease. In consideration of these facts, the amount of resin applied to the paper sheet is preferably 50% or less, more preferably 30% or less with respect to the basis weight. However, resin processing is not always necessary, and for example, if the paper sheet itself has sufficient strength, resin impregnation can be omitted.

(Nanocoat layer 2)
The nanocoat layer 2 is formed by coating the upper surface of the base material 1 with nanofibers. The average fiber diameter of the nanofibers forming the nanocoat layer 2 is smaller than the average fiber diameter of the fibers forming the base material 1 and the non-woven fabric layer 3. As a result, dust having a fine particle size that has passed through the non-woven fabric layer 3 can be effectively captured.

The nanocoat layer 2 is preferably provided by using an electrospinning method. The electrospinning method is a method of applying a high voltage of several thousand to tens of thousands of volts to a solution of a polymer to be a fiber and spraying it toward a ground or a negatively charged target to make it extremely fine. It is used as an effective method for producing nanofibers having a fiber diameter of nano-order. According to this method, nanofibers having a fiber diameter of several tens of nm can be obtained. The fiber system of the nanofiber is appropriately adjusted depending on, for example, the applied voltage in the electrospinning method, the rotation speed of the target drum, and the distance between the nozzle and the target. The nanocoat layer is one surface of the base material and is provided on the second surface of the paper sheet 1A.

The above-mentioned nanofibers are used for the nanocoat layer, and the average fiber diameter of the nanofibers constituting the nanocoat layer is 20 nm to 1000 nm. If the average fiber diameter of the nanofibers is larger than 1000 nm, the surface area of the nanocoat layer is insufficient and sufficient collection efficiency cannot be obtained. The lower limit of the average fiber diameter of the nanofibers is preferably 20 nm or more in consideration of the strength of the nanocoat layer. In consideration of these facts, the average fiber diameter of the nanofibers is 20 nm to 1000 nm, preferably 25 nm to 500 nm, and more preferably 50 nm to 300 nm.

The polymer to be nanofibers is not particularly limited as long as it can be dissolved in a solvent such as water or an organic solvent. For example, polyvinylidene, polyvinylidene fluoride, polyacrylonitrile, polyamide, polyurethane, polyethylene oxide, polylactic acid, polymetaphenylene isophthalamide, polyether sulfone, polymethylmethacrylate, chitosan, chitin, cellulose, aramid and the like can be used.

Basis weight of the nano-coated layer 2 provided on the substrate ^{1, 0.02g / m 2 ~10g / m} 2, preferably from ^{0.02g / m 2 ~0.2g / m 2} . If the basis weight of the nanocoat layer 2 is less than 0.02 g / m ² , the absolute number of nanofibers in the nanocoat layer 2 is insufficient, and sufficient collection and high efficiency cannot be obtained. Further, if the basis weight of the nanocoat layer 2 is more than 10 g / m ² , the pressure loss may increase. The basis weight of the nanocoat layer 2 is controlled by, for example, the spinning time. The longer the spinning time, the larger the basis weight, and the shorter the spinning time, the smaller the basis weight. The basis weight of the nanocoat layer 2 can be obtained, for example, by subtracting the basis weight of only the base material 1 from the total basis weight of the base material 1 and the nanocoat layer 2.

(Non-woven fabric layer 3)
The non-woven fabric layer 3 is made of a non-woven fabric sheet. The non-woven fabric layer 3 composed of the non-woven fabric sheet has a second average pore diameter which is larger than the first average pore diameter which is the filter pore diameter of the base material 1. The second average pore diameter, which is the pore diameter of the non-woven fabric layer 3, is 1 μm to 600 μm, preferably 10 μm to 300 μm. The non-woven fabric layer 3 is arranged on the upstream side of the base material 1 and effectively traps dust having a large particle size.

The non-woven fabric layer 3 has an average fiber diameter of 0.5 μm to 100 μm, preferably 0.8 μm to 40 μm, in order to realize the above-mentioned second average pore diameter. This is because if the fiber diameter is too small, the ventilation resistance increases and the rigidity as a sheet is insufficient, while if the fiber diameter is too large, the fiber surface area becomes small and the dust collection efficiency is significantly lowered. The basis weight of the nonwoven fabric layer 3 is, for ^{example, 5g / m 2 ~200g / m} 2, ^preferably, a ^{10g / m 2 ~100g / m 2} . This is because if the basis weight is smaller than 5 g / m ² , the rigidity of the sheet is insufficient, and if the basis weight is larger than 100 g / m ² , the ventilation resistance increases.

As such a non-woven fabric sheet, for example, a melt-blow non-woven fabric produced by the melt-blow method can be used. As the material of the melt blow nonwoven fabric, polypropylene, polybutylene terephthalate, polyethylene, polyester, polyamide, polymethylpentene, polyphenylene sulfide, polylactic acid and the like can be used. However, the non-woven fabric sheet is not limited to melt blow, and may be manufactured by combining one or several types such as chemical bond, thermal bond, spunlace, needle punch, stitch bond, and spunbond.

(Fixed area 5)
The non-woven fabric layer 3 is fixed to the upper surface of the base material 1 provided with the nanocoat layer 2 via the plurality of fixing regions 5. The fixed regions 5 shown in the figure are circular joints in a plan view, and are provided at a plurality of locations in a state of being separated from each other. The fixed region 5 is fixed to the base material 1 by, for example, ultrasonic heat welding. In this method, the non-woven fabric sheet is laminated on the upper surface of the base material 1 on which the nanocoat layer 2 is formed, and the pressing rods are pressed at predetermined intervals, and ultrasonic vibration is applied in this state to heat the non-woven fabric. It is melted and heat-welded to the base material 1. As described above, the ultrasonic heat welding method has a feature that the resin fibers contained in the non-woven fabric layer 3 and the base material 1 are heat-melted as binder fibers and bonded to each other, so that they can be fixed easily, easily, and at low cost. is there.

However, the non-woven fabric sheet can also be fixed via hot melt. This structure is, for example, sandwiched between the surface of the base material 1 on which the nanocoat is formed and the non-woven fabric sheet in a state where a hot melt adhesive that is melted by heat is applied, and the joint portion is heat-pressed. , The non-woven fabric sheet is heat-welded to the surface of the base material 1 via the plurality of fixed regions 5.

As described above, the fixed region 5 to be ultrasonically heat-welded is joined by crushing the non-woven fabric sheet in a state where the thermoplastic resin contained in the non-woven fabric sheet or the base material 1 is melted, or is joined by a hot press. The fixed region 5 is joined by crushing the heat-melted hot melt so as to penetrate into the non-woven fabric sheet or the base material 1. Therefore, as shown in the cross-sectional view of FIG. 1, these fixed regions 5 are welded in a state where the non-woven fabric layer 3 and a part of the base material 1 are crushed in the thickness direction to be formed in a concave shape. .. Further, the non-woven fabric layer 3 is maintained bulky without being crushed between the separated fixed regions 5, and a gap 4 is formed between the non-woven fabric layer 5 and the nanocoat layer 2.

The fixing regions 5 shown in FIG. 3 are provided on the main surface of the multilayer composite filter medium 100 at intervals of innumerable points, and the non-woven fabric sheet is fixed to the base material 1 at a plurality of locations. As described above, in the multilayer composite filter medium 100 in which the fixed regions 5 are formed in the shape of innumerable dots, the total area of the plurality of fixed regions 5 is 20% or less with respect to the area of the main surface of the multilayer composite filter media 100. , It is preferably provided so as to be 10% or less, more preferably 5% or less. As a result, the filtration region 10 on the main surface of the multilayer composite filter medium 100 can be secured widely.

As shown in FIG. 3, the fixed region 5 formed in a dot shape has a circular shape in a plan view. In this structure in which the fixed region 5 has a circular shape, a load can be uniformly applied to the peripheral edge of the joint, so that the non-woven fabric layer 3 and the base material 1 are not damaged at the boundary edge of the joint. Can be effectively prevented. However, the large number of fixed regions 5 arranged in a dot shape may have a shape other than a circle, for example, a polygonal shape, an elliptical shape, an oval shape, or a short linear shape. The non-woven fabric layer 3 can be fixed to the base material 1 by, for example, making the total length of the short linear fixing region 5 times or less the width and interspersing a large number on the main surface of the multilayer composite filter medium 100.

As shown in FIG. 3, the plurality of fixed regions 5 can be arranged in a grid pattern in a plan view. In this structure, a large number of filtration regions 10 partitioned by four fixed regions 5 forming a quadrangle are arranged in a continuous state in a direction orthogonal to each other. As a result, the material to be filtered, which is supplied to the main surface of the multilayer composite filter medium 100, can be evenly passed through the plurality of filtration regions 10 and filtered evenly.

Further, as shown in FIG. 4, the plurality of fixed regions 5 can be arranged in a slanted paper shape in a plan view. This structure is arranged in a state in which a large number of filtration regions 10 partitioned by three fixed regions 5 forming a triangle are continuous in the directions in which they are inclined (three directions in the figure). This structure also allows the material to be filtered supplied to the main surface of the multilayer composite filter medium 100 to be evenly passed through the plurality of filtration regions 10 to be filtered without unevenness. In particular, as shown in the figure, a structure in which three adjacent fixed regions 5 are arranged in a regular triangle shape is formed inside the filtration region 10 because all the fixed regions 5 adjacent to each other can be arranged at equal intervals. The difference in the spacing between the voids 4 can be reduced. That is, it is possible to reduce the difference in the spacing between the voids 4 formed inside the central portion and the end portion of the triangular filtration region 10, whereby the object to be filtered can be evenly passed through the plurality of filtration regions 10. Can be filtered without spots.

Further, although not shown, the fixed region 5 may be entirely or partially linear. The linear fixed region 5 is characterized in that the boundary portion can be reliably joined in the adjacent filtration region. However, when the fixed region 5 is made linear, the voids are in a non-communication state between the adjacent filtration regions, so that the movement of the object to be filtered is suppressed in the adjacent gaps. Therefore, the length, shape, and joint portion of the linear fixed region 5 are specified in consideration of these matters.

(Void 4)
The non-woven fabric layer 3 is fixed to the upper surface of the base material 1 via the plurality of fixing regions 5 so that a gap is formed between the non-woven fabric layer 3 and the nanocoat layer 2. The void 4 formed between the nanocoat layer 2 and the non-woven fabric layer 3 serves as a passage gap through which the object to be filtered that has passed through the non-woven fabric layer 3 passes. As described above, in the structure in which the gap is provided between the nanocoat layer 2 and the non-woven fabric layer 3, the object to be filtered that has passed through the non-woven fabric layer 3 is passed through the void and passed through the nanocoat layer 2, so that the passage resistance is reduced. It has the characteristic that it can pass through while being small.

(First cake layer forming region 13, second cake layer forming region 14)
In the above-mentioned multilayer composite filter medium 100, as shown in FIG. 2, a first cake layer 11 in which dust 15 captured by the non-woven fabric layer 3 is collected is formed on the upper surface of the non-woven fabric layer 3. The multilayer composite filter medium 100 is a first surface in which dust 15a having a large particle size captured by the non-woven fabric layer 3 having a second average pore diameter is collected on the upper surface of the non-woven fabric layer 3. The first cake layer forming region 13 that forms the cake layer 11 is used. In the first cake layer forming region 13, most of the large-sized dust with a large particle size is captured, but also a small amount of small-sized dust with a small particle size is captured. Further, the multilayer composite filter medium 100 is a second cake layer in which dust 15 captured by the nanocoat layer 2 formed of nanofibers is collected in a gap 4 formed between the non-woven fabric layer 3 and the nanocoat layer 2. 12 is formed. In the multilayer composite filter medium 100, the voids 4 are defined as a second cake layer forming region 14 forming a second cake layer 12 composed of dust 15b having a small particle size captured by the nanocoat layer 2.

As described above, in the multilayer composite filter medium 100, the non-woven fabric layer 3 arranged on the upstream side mainly captures the dust 15a having a large particle diameter in a state where the object to be filtered flows in the flow direction indicated by the arrow in the figure. The first cake layer 11 is formed. Further, the large dust 15b having a small particle size that is not captured by the nonwoven fabric layer 3 passes through the nonwoven fabric layer 3, but is captured by the nanocoat layer 2 to form the second cake layer 12. As described above, the multilayer composite filter medium 100 has a multilayer structure having different average pore diameters, so that dust having different particle diameters can be effectively captured and filtration efficiency can be improved, and dust matching the particle diameter can be removed. The filtration life can be extended by ideally capturing.

[Embodiment 2]
Further, the multilayer composite filter medium 200 according to the second embodiment of the present invention is shown in an enlarged cross-sectional view of FIG. In the multilayer composite filter medium 200 shown in FIG. 5, a paper base material 1X is corrugated. The base material 1X shown in the figure has a nanocoat layer 2 provided on the upper surface of a corrugated paper sheet, and a non-woven fabric layer 3 is arranged on the upper surface of the base material 1X on which the nanocoat layer 2 is formed. The non-woven fabric layer 3 is fixed to the base material 1X via a plurality of fixing regions 5 so as to form a gap 4 between the non-woven fabric layer 3 and the nanocoat layer 2.

As shown in FIG. 5, the base material 1X is processed into a cross-sectional waveform to increase the surface area in the filtration region 10, thereby improving the dust trapping performance. Further, the base material 1X is processed into a corrugated shape to form a plurality of rows of groove portions 6 on the surface. In the multi-layer composite filter medium 200, the volume of the void 4 can be increased by the plurality of rows of grooves 6 provided on the surface of the base material 1X in the filtration region 10. Therefore, the second cake layer forming region 14 can be widened to increase the amount of dust trapped, and the filtration life can be extended.

In this multilayer composite filter medium 200, for example, the fixed region 5 has a circular shape with a radius of 0.5 mm, the distance (D) between the fixed regions 5 adjacent to each other is set to 5 mm to 15 mm, and the fixed region 5 is corrugated into a cross-sectional waveform. The distance (d1) between the groove portions 6 formed on the surface of the base material 1X can be 2 mm to 10 mm, and the depth of the groove portions 6 can be 0.1 mm to 1.0 mm.

[Embodiment 3]
Further, the multilayer composite filter medium 300 according to the third embodiment of the present invention is shown in an enlarged cross-sectional view of FIG. In the multilayer composite filter medium 300 shown in FIG. 6, the surface of the paper base material 1Y is embossed. In the base material 1Y shown in the figure, a nanocoat layer 2 is provided on the upper surface of a paper sheet whose surface is embossed, and a non-woven fabric layer 3 is arranged on the upper surface of the base material 1Y on which the nanocoat layer 2 is formed. The non-woven fabric layer 3 is fixed to the base material 1Y via a plurality of fixing regions 5 so as to form a gap 4 between the non-woven fabric layer 3 and the nanocoat layer 2.

As shown in FIG. 6, the base material 1Y has a plurality of recesses 7 provided on the surface to increase the surface area in the filtration region 10, thereby enhancing the dust trapping performance. In the multi-layer composite filter medium 300, the volume of the void 4 can be increased by the plurality of recesses 7 provided on the surface of the base material 1Y in the filtration region 10. Therefore, the second cake layer forming region 14 can be widened to increase the amount of dust trapped, and the filtration life can be extended. In the base material 1Y shown in FIG. 6, the shape of the recess 7 is hemispherical, but the shape of the recess is not limited to this. The concave portion can have, for example, an elliptical shape, an oval shape, or a polygonal shape in a plan view, and has a shape in which the area gradually decreases toward the bottom of the concave portion, and the area of the opening and the bottom surface are made equal. It can also be shaped. For example, the recess may have an inverted truncated cone shape or a cylindrical shape.

In this multilayer composite filter medium 300, for example, the fixed area 5 has a circular shape with a radius of 0.5 mm, the distance (D) between the fixed areas 5 adjacent to each other is set to 5 mm to 15 mm, and the surface of the base material 1Y is embossed. The number of recesses 7 formed in is 1 piece / cm ² to 10 pieces / cm ² , the distance between the recesses 7 (d2) is ² mm to 10 mm, the opening area of the recesses 7 is 3 mm ^{2 to} 50 mm ² , and the recesses. The depth of 7 can be 0.1 mm to 1.0 mm.

(Manufacturing method of multilayer composite filter medium)
The above-mentioned multilayer composite filter medium 100 is manufactured as follows by the step shown in FIG. 7.
[Base material preparation process]
In this step, a paper base material 1 having a first average pore diameter is prepared. As shown in FIG. 7A, the paper base material 1 is composed of a paper sheet 1A that is made in the papermaking process. As shown in FIG. 7B, the paper sheet 1A made in the papermaking process is entirely or partially impregnated with resin in the resin processing process. In this resin processing step, a liquid resin is transferred to one side surface of the paper sheet 1A using a roll. The liquid resin is applied in a state of being impregnated from the first surface (lower surface in the drawing) side of the paper sheet 1A. The paper sheet 1A is reinforced by drying the resin impregnated inside.

[Nanocoat process]
As shown in FIG. 7C, the second surface of the paper sheet 1A is coated with nanofibers to form the nanocoat layer 2. The nanocoat layer 2 is preferably formed by an electrospinning method.

[Laminating process]
As shown in FIG. 7D, a non-woven fabric having a second average pore diameter larger than the first average pore diameter is arranged on the upper surface of the base material 1 on which the nanocoat layer 2 is formed to form the non-woven fabric layer 3. .. As the non-woven fabric forming the non-woven fabric layer 3, a melt-blow non-woven fabric formed by melt-blow is used.

[Joining process]
As shown in FIG. 7 (E), the upper surface of the non-woven fabric layer 3 is pressed against the base material 1 by the pressing rod 20 and ultrasonically vibrated to form the fixed region 5, and the non-woven fabric layer 3 is applied to the upper surface of the base material 1. And join locally. As shown in the figure, the non-woven fabric layer 3 is bonded to the base material 1 via a plurality of fixed regions 5 formed apart from each other so that a gap 4 is formed between the non-woven fabric layer 3 and the nanocoat layer 2. Will be done. As shown in FIG. 3 or 4, in the multilayer composite filter medium 100, a plurality of fixing regions 5 are provided on the main surface at intervals at points, and the non-woven fabric layer 3 is fixed to the base material 1.

Examples will be shown below, and the present invention will be described in more detail. However, the present invention is not limited to the following examples, and can be appropriately modified within the above-mentioned range. The technical scope of the present invention also includes those appropriately modified.

(Example 1)
A papermaking slurry obtained by suspending the following main fibers in a dispersion is wet-made to make a sheet-shaped paper sheet 1A. For example, water can be used as the dispersion liquid for suspending the main fibers. The paper sheet 1A is adjusted so that the basis weight is 100 g / m ² and the first average pore diameter, which is the filter pore diameter, is 20 μm to 90 μm.
Natural fiber (natural cellulose fiber): Average fiber diameter 20 μm ……… 90% by weight
Chemically synthesized fiber (polyester fiber): Average fiber diameter 10 μm …… 10% by weight

The surface of the wet-made paper sheet 1A is resin-processed. The paper sheet 1A is impregnated with resin from the front surface side. As the resin, for example, a liquid phenol resin applied to the surface of the roll is transferred to the surface of the paper sheet 1A and impregnated. The liquid resin impregnated on the surface of the paper sheet 1A is dried.

The second surface of the resin-processed paper sheet 1A is coated with nanofibers to provide a nanocoat layer. The nanocoat layer 2 is coated with a polyvinylidene fluoride solution as nanofibers on the upper surface of the base material 1 by, for example, an electrospinning method. Nanofibers, the average fiber diameter and 50 nm to 300 nm, the basis weight is adjusted to be ^{0.02g / m 2 ~0.2g / m 2} .

A non-woven fabric sheet is arranged on the upper surface of the base material 1 on which the nano-coated layer 2 is formed to provide the non-woven fabric layer 3. As the non-woven fabric sheet, a melt-blow non-woven fabric produced by the melt-blow method is used. Meltblown nonwoven, using a polypropylene fiber having an average fiber diameter and 0.8Myuemu～40myuemu, basis weight ^{10g / m 2 ~100g / m 2} , as the second average pore size is the pore size becomes 30μm~200μm Adjust to.

A plurality of fixed regions 5 are provided by ultrasonic heat welding by pressing pressing rods at a plurality of locations at predetermined intervals on the upper surface of the non-woven fabric layer 3 arranged on the upper surface of the base material 1, and the non-woven fabric layer 3 is used as the base material 1. To join. The tip surface of the pressing rod 20 has a circular shape with a radius of 0.5 mm, and as shown in FIG. 3, a plurality of fixed regions 5 are formed in an array in a grid pattern. The plurality of fixed regions 5 are arranged so that the distance between the adjacent fixed regions is 3 mm, and the total area of the plurality of fixed regions 5 is about 5 with respect to the area of the main surface of the multilayer composite filter medium 100. %.

(Comparative Example 1)
A filter paper is produced by impregnating both sides of a paper sheet wet-papered in the same manner as in Example 1 with a resin in the same manner as in Example 1, and this filter paper is used as the filter material of Comparative Example 1.

(Comparative Example 2)
A filter medium in which a resin is impregnated from the first surface side of a paper sheet wet-papered in the same manner as in Example 1 and a nanofiber is coated on the second surface to provide a nanocoat layer is used as the filter medium of Comparative Example 2. ..

(Comparative Example 3)
A melt-blown non-woven fabric manufactured in the same manner as in Example 1 is laminated and bonded to the surface of the filter paper manufactured in Comparative Example 1. The melt-blown nonwoven fabric is bonded to the filter paper via a plurality of fixed regions formed by ultrasonic heat welding, as in Example 1. The filter medium produced in this manner is used as the filter medium of Comparative Example 3.

Various measurements regarding the characteristics of the filter media prepared in Example 1 and Comparative Examples 1 to 3 were performed. The results are shown in the graphs of FIGS. 8 to 10.
In the following measurements, a filter tester MFP3000S manufactured by PALAS was used as a testing machine, and ISO and AC dust FINE were used as the dust used.

For the filter media prepared in Example 1 and Comparative Examples 1 to 3, a test piece of the filter medium having a single plate filtration area of 100 cm ² was set in a holder, and air was passed in the vertical direction at a flow velocity of 15 cm / sec to allow air to pass through the filter medium upstream. The dust retention amount (DHC) [g / m ² ] (see FIG. 8) and the dust collection efficiency [%] (see FIG. 9) with respect to the pressure difference ΔP on the side and the downstream side were measured. In addition, the dust collection efficiency [%] (see FIG. 10) with respect to the average pore size of the dust used was measured.

As is clear from FIGS. 8 to 10, it is clear that the multilayer composite filter medium in Example 1 can realize an excellent dust retention amount (DHC) and dust collection efficiency as compared with the filter media of Comparative Examples 1 to 3. It became.

The multi-layer composite filter medium of the present invention is suitably used as a filter medium capable of improving filtration performance and filtration life for air filters, oil filters, fuel filters for engines of automobiles, etc., or filters for air conditioning equipment, hydraulic equipment. It is suitably used as a filter for electric discharge processing equipment, a filter for a compressor, a process filter and the like.

100, 200, 300 ... Multilayer composite filter media 1, 1X, 1Y ... Base material 1A ... Paper sheet 2 ... Nanocoat layer 3 ... Non-woven fabric layer 4 ... Voids 5 ... Fixed area 6 ... Grooves 7 ... Recesses 10 ... Filtration area 11 ... First cake layer 12 ... Second cake layer 13 ... First cake layer forming region 14 ... Second cake layer forming region 15 ... Dust 15a ... Dust 15b ... Dust 20 ... Pressing rod

Claims (18)

A multi-layer composite filter medium with a main surface
A paper substrate with a first average pore diameter and
A nanocoat layer containing nanofibers formed on the upper surface of the base material and
A non-woven fabric layer made of a non-woven fabric having a second average pore diameter larger than the first average pore diameter, which is arranged on the upper surface side of the base material on which the nanocoat layer is formed, and
With
The average fiber diameter of the nanofibers forming the nanocoat layer is smaller than the average fiber diameter of the fibers forming the base material and the non-woven fabric layer.
A multilayer composite filter medium in which the non-woven fabric layer is fixed to the base material via a plurality of fixed regions provided apart from each other so as to form a gap between the non-woven fabric layer and the nanocoat layer. The multilayer composite filter medium according to claim 1.
On the upper surface of the non-woven fabric layer, a first cake layer forming region for forming a first cake layer in which dust trapped by the non-woven fabric layer is collected is formed.
A multi-layer composite filter medium formed in the voids with a second cake layer forming region forming a second cake layer in which dust captured by the nanocoat layer is aggregated. The multilayer composite filter medium according to claim 1 or 2.
A multilayer composite filter medium in which the plurality of fixed regions are formed on the main surface of the multilayer composite filter medium at points. The multilayer composite filter medium according to any one of claims 1 to 3.
A multilayer composite filter medium in which the total area of the plurality of fixed regions is 20% or less of the area of the main surface of the multilayer composite filter medium. The multilayer composite filter medium according to any one of claims 1 to 4.
A multilayer composite filter medium in which the fixed region is formed by any of ultrasonic heat welding, hot melting, and thermocompression bonding. The multilayer composite filter medium according to any one of claims 1 to 5.
The base material is composed of a wet-made paper sheet.
The paper sheet is
The fiber diameter is 100 μm or less, and the average fiber diameter is 1 μm to 80 μm.
A multilayer composite filter medium having a first average pore diameter of 0.5 μm to 200 μm. The multilayer composite filter medium according to claim 6.
A multilayer composite filter medium in which the base material is impregnated with a resin in whole or in part of the paper sheet. The multilayer composite filter medium according to claim 7.
A multilayer composite filter medium in which the base material is impregnated with a resin from the first surface side of the paper sheet and the nanocoat layer is provided on the second surface. The multilayer composite filter medium according to any one of claims 1 to 8.
The non-woven fabric constituting the non-woven fabric layer is
With an average fiber diameter of 0.5 μm to 100 μm,
A multilayer composite filter medium having a second average pore diameter of 1 μm to 600 μm. The multilayer composite filter medium according to any one of claims 1 to 10.
A multilayer composite filter medium in which the non-woven fabric layer is formed by melt blowing. The multilayer composite filter medium according to any one of claims 1 to 11.
The nanocoat layer is
A multilayer composite filter medium having an average fiber diameter of 20 nm to 1000 nm. The multilayer composite filter medium according to any one of claims 1 to 12.
A multi-layer composite filter medium in which the nanocoat layer is formed by an electrospinning method or an electrobubble spinning method. The multilayer composite filter medium according to any one of claims 1 to 12.
A multi-layer composite filter medium in which the base material is corrugated. The multilayer composite filter medium according to any one of claims 1 to 12.
A multi-layer composite filter medium in which the surface of the base material is embossed. The multilayer composite filter medium according to any one of claims 1 to 14.
A multi-layer composite filter medium that is one of an air filter for an engine, an oil filter, a filter for fuel, a filter for air conditioning equipment, a filter for hydraulic equipment, a filter for discharge processing equipment, a filter for a compressor, and a process filter. A base material preparation step for preparing a paper base material having a first average pore diameter, and
A nanocoating step of coating nanofibers on the upper surface of the base material to form a nanocoat layer,
A laminating step of arranging a non-woven fabric having a second average pore diameter larger than the first average pore diameter on the upper surface side of the base material on which the nanocoat layer is formed to form a non-woven fabric layer.
Production of a multilayer composite filter medium including a joining step of providing a plurality of fixing regions at intervals so as to form a gap between the nonwoven fabric layer and the nanocoat layer and fixing the nonwoven fabric layer to the substrate. Method. The method for producing a multilayer composite filter medium according to claim 16.
The base material preparation step
A papermaking process in which a paper sheet constituting the base material is wet-made and
Including a resin processing step of impregnating the resin from the front surface side of the paper sheet made by the papermaking step.
In the nanocoating step
A method for producing a multilayer composite filter medium in which the nanocoat layer is formed on the second surface of the paper sheet. The method for producing a multilayer composite filter medium according to claim 16 or 17.
In the joining process
The plurality of fixed regions are provided on the main surface of the multilayer composite filter medium at a point-like distance.
A method for producing a multilayer composite filter medium, wherein the total area of the plurality of fixed regions is 20% or less of the area of the main surface of the multilayer composite filter medium.