JP6991018B2 - Filter media with pleated shape - Google Patents

Description

The present invention relates to a filter medium having a pleated shape.

Conventionally, in order to collect dust in a fluid such as a gas or a liquid, a filter medium made of a sheet-like cloth such as a non-woven fabric, a woven fabric or a knitted fabric has been used. Further, the filter medium is required to have a low pressure loss such as an initial pressure loss and to exhibit high collection efficiency while maintaining a low pressure loss.
In order to provide a filter medium that satisfies the above-mentioned requirements, the applicant of the present application has been published in JP-A-11-104417 (Patent Document 1), JP-A-2014-004555 (Patent Document 2), and JP-A-2014-184360. We have proposed a filter medium having a pleated shape having the following configuration as described in Japanese Patent Application Laid-Open No. 3 (Patent Document 3).
(1) It has a fiber layer in which ultrafine fibers and thick fibers are mixed.
(2) The average fiber diameter of the ultrafine fibers constituting the fiber layer is 0.1 to 10 μm, and the average fiber diameter of the thick fibers constituting the fiber layer is larger than the average fiber diameter of the ultrafine fibers.
The filter medium having a pleated shape having the above-mentioned configurations (1) and (2) is per unit area when the filter medium having a pleated shape is viewed from the upstream side of filtration (upward on the paper surface in FIG. 1 described later). Since the area of the filter medium existing in the filter medium is large, the pressure loss such as the initial pressure loss is low, and the low pressure loss is maintained because the fiber layer is provided by mixing the ultrafine fibers having the above-mentioned average fiber diameter and the thick fibers. High collection efficiency can be demonstrated in the state.

Japanese Unexamined Patent Publication No. 11-10417 Japanese Unexamined Patent Publication No. 2014-004555 Japanese Unexamined Patent Publication No. 2014-184360

However, as disclosed in Patent Document 2 (paragraph number 0002) and Patent Document 3 (paragraph number 0002), the filter media having the above-mentioned configurations (1) and (2) is pleated with a mountain height of 50 mm or more. When the shape was formed, the adjacent filter media tended to adhere to each other, and the filter media was deformed.
As a result, a large structural pressure loss was generated in the filter medium having the pleated shape, and the filter medium having the pleated shape had a high pressure loss.

The first object of the present invention is to provide a filter medium having a pleated shape having a pleated mountain height of 50 mm or more, which has a lower pressure loss and can exhibit high collection efficiency while maintaining a low pressure loss.

The present invention
"A pleated filter medium with the following configuration.
(1) The filter medium having a pleated shape is composed only of a fiber layer composed of a mixture of ultrafine fibers and thick fibers.
(2) The average fiber diameter of the ultrafine fibers constituting the fiber layer is 0.1 to 10 μm, and the average fiber diameter of the thick fibers constituting the fiber layer is larger than the average fiber diameter of the ultrafine fibers.
(3) The height of the pleated ridge of the filter medium having a pleated shape is 50 mm or more.
(4) The filter medium having a pleated shape has a pleated-shaped portion in which the angle of the pleated valley formed between the adjacent pleated mountains is larger than 6.6 ° and smaller than 8.8 °. "
Is.

In a filter medium having a pleated shape having the configurations (1) to (3) as in the present invention, the angle of the pleated valley formed between the adjacent pleated peaks in order to prevent the adjacent filter media from coming into close contact with each other. When (hereinafter, sometimes referred to as a pleated valley angle) is increased, the pressure loss becomes higher as the area of the filter medium existing per unit area becomes smaller.
On the other hand, in a filter medium having a pleated shape having the configurations (1) to (3) as in the present invention, in order to widen the area of the filter medium existing per unit area, if the pleated valley angle is reduced, the adjacent filter media are moved to each other. Since it is easier to adhere, the filter medium is greatly deformed, and the pressure loss becomes high as the structural pressure loss increases.
Therefore, in a filter medium having a pleated shape having the configurations (1) to (3) as in the present invention, it has been considered that an increase in pressure loss is inevitable no matter how the pleated valley angle is adjusted. ..

However, as a result of continued studies by the inventors of the present application, the filter medium having a pleated shape having the configurations (1) to (3) according to the present invention has a pleated valley angle larger than 6.6 ° and smaller than 8.8 °. It has been found that when the pleated portion is provided, the pressure loss of the filter medium having the pleated shape is unexpectedly reduced.
Therefore, according to the present invention, it is possible to provide a filter medium having a pleated shape having a pleated mountain height of 50 mm or more, which has a lower pressure loss such as an initial pressure loss and can exhibit high collection efficiency while maintaining a low pressure loss.

It is a schematic cross-sectional view of the filter medium which has a pleated shape which concerns on this invention. It is a side view which shows an example of the filter medium manufacturing apparatus which can manufacture the filter medium which concerns on this invention.

In order to solve the problem in the present invention, various configurations such as the following can be appropriately selected.

The filter medium according to the present invention includes a fiber layer in which ultrafine fibers and thick fibers are mixed.
The fiber layer here refers to a layer made of a fiber web, a non-woven fabric, or a sheet-like fiber such as a knitted fabric or a woven fabric.
As an aspect of the fiber layer, it may be a fiber layer in which ultrafine fibers and thick fibers are uniformly mixed, or a fiber layer in which ultrafine fibers and thick fibers are non-uniformly mixed. As the fiber layer formed by the non-uniform mixture, for example, from one main surface to the other main surface in the fiber layer, the abundance ratio of ultrafine fibers and thick fibers (ratio of existing fiber mass or ratio of number of fibers, etc.) ) May change. The specific body can be in an embodiment in which the abundance ratio of ultrafine fibers decreases and the abundance ratio of thick fibers increases from one main surface to the other main surface.

The ultrafine fiber which is a constituent fiber of the fiber layer is, for example, a polyolefin resin (polyethylene, polypropylene, polymethylpentene, a polyolefin resin having a structure in which a part of hydrocarbon is replaced with a cyano group or a halogen such as fluorine or chlorine), or the like. Styline-based resin, polyether-based resin (polyetheretherketone, polyacetal, phenol-based resin, melamine-based resin, urea-based resin, epoxy-based resin, modified polyphenylene ether, aromatic polyetherketone, etc.), polyester-based resin (polyethylene terephthalate) , Polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polycarbonate, polyarylate, total aromatic polyester resin, unsaturated polyester resin, etc.), polyimide resin, polyamideimide resin, polyamide resin (for example) , Aromatic polyamide resin, aromatic polyetheramide resin, nylon resin, etc.), resin having a ditryl group (for example, polyacrylonitrile), urethane resin, epoxy resin, polysulfone resin (polysulfone, polyethersulfone, etc.) ), Fluorine resin (polytetrafluoroethylene, polyvinylidene fluoride, etc.), cellulose resin, polybenzoimidazole resin, acrylic resin (for example, polyacrylonitrile resin obtained by copolymerizing acrylic acid ester or methacrylic acid ester, acrylonitrile). It can be a fiber having a known resin such as a modal acrylic resin obtained by copolymerizing vinyl chloride or vinylidene chloride).
The resin described above may be composed of either a linear polymer or a branched polymer, and the resin may be a block copolymer or a random copolymer. Further, the three-dimensional structure of the resin and the presence or absence of crystallinity may be used. Further, it may be a mixture of a plurality of resins.

In particular, when the ultrafine fiber contains a resin having a volume resistivity of 10 ¹⁴ Ω · cm or more (more preferably, it is composed of only a resin having a volume resistivity of 10 ¹⁴ Ω · cm or more), the charge amount. Therefore, it is preferable to provide a charged filter medium having a pleated shape having excellent filtration performance.
Resins having a volume specific resistance value of 10 ¹⁴ Ω · cm or more include, for example, polyolefin resins (for example, polyethylene resins, polypropylene resins, polymethylpentene resins, polystyrene resins, etc.), polyvinyl tetrafluoride, and poly. Examples thereof include vinylidene chloride, polyvinyl chloride and polyurethane.
In order to increase the charge amount of the ultrafine fibers, it is preferable to mix the charge aid with the resin contained in the ultrafine fibers (particularly, the resin having a volume resistivity of 10 ¹⁴ Ω · cm or more).

As a charging aid, one or two selected from, for example, hindered amine compounds, aliphatic metal salts (for example, magnesium salt of stearic acid, aluminum salt of stearic acid, etc.), and unsaturated carboxylic acid-modified polymers. The above compounds can be added as additives. Among these series of additives, it is preferable to add a hindered amine compound, and as a specific example thereof, for example, poly [{(6- (1,1,3,3-tetramethylbutyl) imino-1,3,5) -Triazine-2,4-diyl) {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino}} , Dimethyl-1- (2-hydroxyethyl) succinate-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, 2- (3,5-di-t-butyl-4-hydroxybenzyl) ) -2-N-Butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl) and the like can be mentioned.
The mass of the charging aid added to the resin is not particularly limited, but if the mass of the charging aid added is too small, the charging effect in the fiber layer may be smaller than expected. Further, if the added mass of the charging aid is too large, the strength of the fiber layer may be inferior. Therefore, the mass of the charging aid added is preferably 0.01 mass% to 5 mass% with respect to the mass of the resin of 100 mass%.

The ultrafine fiber may be composed of one type of resin or may be composed of a plurality of types of resin. As the fiber mode composed of a plurality of types of resins, a fiber mode generally referred to as a composite fiber, for example, a core sheath type, a sea island type, a side-by-side type, an orange type, a bimetal type, or the like can be used.

Further, the ultrafine fibers may include irregular cross-sectional fibers in addition to fibers having a substantially circular cross-sectional shape and elliptical fibers. As the irregular cross-sectional fiber, a polygonal shape such as a triangular shape, an alphabetical character shape such as a Y shape, an irregular shape, a multi-leaf shape, a symbolic shape such as an asterisk shape, or a shape in which a plurality of these shapes are combined is used. Examples of fibers having a fiber cross section such as the above can be exemplified.

The fiber length of the ultrafine fiber is not particularly limited, but is a short fiber or a long fiber having a specific measurable length, or a fiber length having a length that makes it difficult to substantially measure the fiber length. It can be a continuous fiber having.
When the ultrafine fibers have a continuous length, the rigidity of the fiber layer is likely to be improved. Therefore, it is preferable to provide a filter medium having a low pressure loss by preventing the filter medium from being deformed by being excellent in strength. Therefore, it is preferable that the fiber layer contains ultrafine fibers having a continuous length as constituent fibers. The fiber having a continuous length can be produced by using a direct spinning method.

The average fiber diameter of the ultrafine fibers constituting the fiber layer is 0.1 to 10 μm. If the average fiber diameter of the ultrafine fibers is outside this range, it becomes difficult to provide a fiber layer capable of forming a filter medium capable of exhibiting high collection efficiency while maintaining a low pressure loss. The average fiber diameter of the ultrafine fibers constituting the fiber layer is preferably 0.25 to 5 μm so as to provide a fiber layer capable of forming a filter medium capable of exhibiting high collection efficiency while maintaining a low pressure loss. , 0.5-4 μm, more preferably.

The "average fiber diameter" referred to here can be calculated based on a 1000-fold electron micrograph of a measurement target portion including fibers such as the surface or cross section of a filter medium or a fiber layer. Specifically, 200 fibers (ultrafine fibers, thick fibers, etc.) for which the average fiber diameter is to be calculated are selected from the electron micrographs, and the arithmetic average value of each fiber diameter of the selected fibers is used as the average fiber diameter. When the cross-sectional shape of the fiber is non-circular, the diameter of a circle having the same area as the cross-sectional area is regarded as the fiber diameter.
As a specific example, when the ultrafine fiber is a fiber having a continuous length and the thick fiber is a short fiber or a long fiber, 200 fibers having a continuous length are selected from the electron micrographs, and each fiber diameter of the selected fiber is selected. By calculating the arithmetic average value of, the average fiber diameter of the ultrafine fibers constituting the fiber layer can be obtained.

The ultrafine fiber is, for example, a melt spinning method, a dry spinning method, a wet spinning method, a direct spinning method (melt blow method, spunbond method, electrostatic spinning method, a method of spinning using centrifugal force, JP-A-2011-012372). (Spinning method using the accompanying air flow described in the above, neutralization spinning method described in JP-A-2005-264374, etc.), fibers with a small fiber diameter by removing one or more resin components from the composite fiber. Can be obtained by a known method such as a method for extracting.
In particular, the ultrafine fibers are directly spun so that a fiber layer capable of improving the filtration performance of the pleated filter medium by having the fibers uniformly dispersed and present even though the fiber diameter is small and the basis weight is light can be formed. It is preferably prepared by the method.

The composition and manufacturing method of the thick fiber, which is a constituent fiber of the fiber layer, can be appropriately selected in the same manner as the above-mentioned composition of the ultrafine fiber, but the thick fiber is preferably a fiber containing a thermoplastic resin. When the thick fiber contains a thermoplastic resin, the thick fiber and the ultrafine fiber and / or the thick fiber can be fiber-bonded to each other by the thermoplastic resin, so that a fiber layer having a relatively coarse space can be provided. It is preferable to provide a fiber layer having a relatively coarse space because a filter medium having a low pressure loss can be provided.

As an embodiment of the thick fiber having such thermal adhesion performance, for example, (1) a resin component having a high melting point is used as a core component, and a resin component having a melting point lower than that of the resin component having a melting point (fused component) is used as a sheath component. A core-sheath type thick fiber or an eccentric type thick fiber, (2) a side-by-side type thick fiber in which a resin component having a high melting point and a resin component having a melting point lower than this high melting point resin component are bonded together, (3). It can be a sea-island type thick fiber or the like in which a large number of resin components having a higher melting point than the low melting point resin component are scattered in the low melting point resin component. Among these, the thick fiber is preferably a core-sheath type thick fiber, an eccentric type thick fiber, or a sea-island type thick fiber having the above-mentioned structure so as to easily form a fiber layer having a relatively coarse space.
Further, it is preferable that the thick fiber is a fiber that has been mechanically stretched after spinning (stretched fiber) because it can provide a fiber layer having excellent strength and rigidity.

The fiber length of the thick fibers can be appropriately selected in the same manner as the ultrafine fibers described above, but the thick fibers have a specific measurable length so as to be able to provide a fiber layer mixed with the ultrafine fibers in an intended manner. It is preferable that it is a short fiber or a long fiber having. In particular, even when an ultrafine fiber having a continuous length is adopted, the ultrafine fiber and the thick fiber are easily mixed, so that a fiber layer in which the ultrafine fiber and the thick fiber are mixed in an intended manner can be provided. In addition, the thick fibers are preferably short fibers or long fibers having a specific measurable length. The fiber length of the thick fiber can be appropriately selected, but is preferably 5 to 160 mm, more preferably 25 to 110 mm so as to be easily entangled with the ultrafine fiber.

The average fiber diameter of the thick fibers constituting the fiber layer is larger than the average fiber diameter of the ultrafine fibers. The average fiber diameter can be calculated in the same manner as the method for calculating the average fiber diameter of the ultrafine fibers constituting the fiber layer described above. As a specific example, when the ultrafine fibers are fibers having a continuous length and the thick fibers are short fibers or long fibers, 200 short fibers or long fibers are selected from the electron micrographs, and each fiber diameter of the selected fibers is selected. By calculating the arithmetic average value of, the average fiber diameter of the thick fibers constituting the fiber layer can be obtained.

The average fiber diameter of the thick fibers can be appropriately selected as long as it is thicker than the ultrafine fibers, but specifically, it can be thicker than 10 μm and 100 μm or less. When the average fiber diameter of the thick fibers is 10 μm or less, it becomes difficult to provide a fiber layer capable of forming a filter medium capable of exhibiting high collection efficiency while maintaining a low pressure loss. Further, if the average fiber diameter exceeds 100 μm, the space becomes too large, and it tends to be difficult to provide a fiber layer capable of forming a filter medium capable of collecting fine dust. Therefore, the average fiber diameter of the thick fibers constituting the fiber layer is preferably 15 to 70 μm, more preferably 15 to 55 μm.

The mass percentage of the ultrafine fibers in the fiber layer can be 2 mass% or more and 40 mass% or less. If the mass percentage of the ultrafine fibers is less than 2 mass%, there is a risk that fine dust cannot be collected due to the small amount of ultrafine fibers, while if it exceeds 40 mass%, the coarse dust will immediately cause eyes. There is a risk of clogging. Therefore, the mass percentage of the ultrafine fibers in the fiber layer is more preferably 3 to 35 mass%, and even more preferably 4 to 30 mass%.

The fiber layer may be composed of entangled ultrafine fibers and thick fibers. The entanglement method can be appropriately selected, but it can be a fiber layer in which the constituent fibers are entangled with each other by a needle, a water flow, a gas flow such as steam, or the like.
Further, the fiber layer may be formed by melting a part of the ultrafine fiber and / or the thick fiber and melting and integrating the fibers with each other, or by adhering and integrating the fibers with each other by a binder. In particular, when a part of the ultrafine fiber and / or the thick fiber is melted and the fibers are melted and integrated, the pressure loss of the filter medium due to the presence of the binder can be prevented from increasing, and the fiber is separated from the filter medium. It is preferable because it can prevent the filtration performance from deteriorating.

The thickness of the fiber layer is appropriately selected, but can be 0.1 to 10 mm. If the thickness of the fiber layer is less than 0.1 mm, it is difficult for the thick fibers to form a relatively coarse space, so that the pressure loss tends to increase. If the thickness exceeds 10 mm, there are many parts that are not involved in filtration. Tend. Therefore, the thickness is more preferably 0.2 to 5 mm, and even more preferably 0.5 to 4 mm. The "thickness" in the present invention is the load direction (thickness) of the object to be measured when 20 g per 1 cm ² unit area is loaded from the main surface of the object to be measured such as a fiber layer or a filter medium to the other main surface. Direction) length.

The basis weight of the fiber layer is appropriately selected, but can be 30 to 300 g / m ² . If the basis weight of the fiber layer is less than 30 g / m ² , the thickness and density tend to be too small to collect fine dust, and if the basis weight exceeds 300 g / m ² , the thickness and density tend to be too small. The density becomes too high, and the coarse dust tends to cause clogging immediately, or the pressure loss tends to increase. Therefore, the basis weight is more preferably 40 to 250 g / m ² , and even more preferably 50 to 200 g / m ² .

The apparent density of the fiber layer is appropriately selected, but can be 0.003 to 3 g / cm ³ . If the apparent density is less than 0.003 g / cm ³ , it tends to be difficult to collect fine dust, and if the apparent density exceeds 3 g / cm ³ , it is immediately visible due to the coarse dust. It tends to cause clogging and increase the pressure loss. Therefore, the apparent density is preferably 0.008 to 1.25 g / cm ³ .

Even if the filter medium according to the present invention is composed of only a fiber layer, it is formed by laminating a separately prepared support (for example, a fiber web, a non-woven fabric, or a cloth such as a knit or woven fabric, a film, a perforated plate, etc.) on the fiber layer. It may be composed of a laminated body. Since it is possible to provide a filter medium having excellent rigidity by reinforcing the fiber layer, it is preferable to use a spunbonded nonwoven fabric as a support. By reinforcing the fiber layer, it is possible to provide a filter medium having a pleated shape with a low pressure loss by preventing the filter media from being deformed due to the fact that the adjacent filter media are difficult to adhere to each other when the filter medium is pleated.
In particular, even if the filter medium has a pleated shape that is more easily deformed, such as a mountain height of 50 mm or more (particularly 100 mm or more), it is difficult for adjacent filter media to adhere to each other and the filter media is prevented from being deformed. Therefore, it is possible to provide a filter medium having a pleated shape having a low pressure loss.

The fineness of the constituent fibers in the support is appropriately selected, and the smaller the fineness value, the better the collection efficiency of the filter medium. However, if the fineness value is too small, the pressure loss of the filter medium may become excessively high. be. Therefore, the fineness of the constituent fibers in the support is preferably 1 to 100 dtex, preferably 2 to 50 dtex, and preferably 3 to 30 dtex.

The basis weight of the support can be appropriately selected, and the lighter the basis weight, the lower the pressure loss of the filter medium. However, if the basis weight is too light, the fiber layer cannot be effectively reinforced, and it becomes difficult to provide a filter medium having excellent rigidity. there is a possibility. Therefore, the basis weight of the support is preferably 20 to 200 g / m ² , preferably 30 to 150 g / m ² , and preferably 40 to 100 g / m ² .

The thickness of the support can be appropriately selected, but can be 0.1 to 2 mm, 0.15 to 1.5 mm, and 0.2 to 1 mm.

The method of laminating the fiber layer and the support can be appropriately selected. For example, even if the fiber layer and the support are simply overlapped with each other, the binder web, the binder liquid, or the fiber layer and the fiber layer and the support can be used. / Or both layers may be bonded and integrated by fiber adhesion by the constituent fibers of the support, or may be laminated and integrated by heat sealing, ultrasonic fusion, heat roll pressing, or the like.
When the fiber layer and the support are laminated by a binder, the amount of the binder applied can be appropriately selected, but the amount of the binder can be 1 to 30 g / m ² and 2 to 20 g / m ² . It can be 3 to 15 g / m ² .
Further, when the fiber layer and the support are bonded and integrated by the fiber adhesion by the fiber layer and / or the constituent fibers of the support, the air permeability between the fiber layer and the support is caused by the adhesive component such as a binder. It is preferable because it can prevent the pressure loss of the filter medium from increasing due to the blockage.

The fiber layer and / or support may contain functional particles, binders, pigments and the like.
Functional particles include, for example, radioactive substance adsorbents (eg, zeolite, activated carbon, navy blue (Prussian blue), etc.), antibacterial agents, antiviral agents, antifungal agents, catalysts (eg, titanium oxide, manganese dioxide, or platinum-supported alumina). Humidity control agents (eg silica gel, silica microcapsules, etc.), deodorants such as activated carbon and carbon black, pigments, flame retardants such as phosphate-based flame retardants and aluminum hydroxide, deodorants, insect repellents, and sterilizers. Particles such as agents, fragrances, cation exchange resins and anion exchange resins can be mentioned.
As described above, the functional particles and pigments may be supported or adhered to the fiber layer and / or the support, but are kneaded into the fibers constituting the fiber layer and / or the support. It may be in the above mode.

The filter medium is preferably charged so as to provide a filter medium having a lower pressure loss and capable of exhibiting a high collection efficiency while maintaining a low pressure loss. As a means for charging the filter medium, known means such as a plasma charging means, a corona charging means, a means for applying a force via a polar liquid to charge, and a means for rubbing and charging a plurality of types of fiber components are appropriately used. Available in combination or in combination.
It may be a charged filter medium provided with a charged fiber layer and / or a charged support, or a charged filter medium formed by charging the prepared filter medium.

The thickness of the filter medium can be appropriately selected, and the thinner the thickness, the lower the pressure loss of the filter medium, but if the thickness is too thin, the filtration performance may be deteriorated. Therefore, the thickness of the filter medium is preferably 0.2 to 12 mm, preferably 0.4 to 6.5 mm, and preferably 0.5 to 5 mm.

The basis weight of the filter medium can be appropriately selected. The heavier the basis weight, the easier it is to provide a filter medium having excellent rigidity. However, if the basis weight is too heavy, the pressure loss of the filter medium may increase. Therefore, the basis weight of the filter medium is preferably 35 to 400 g / m ² , preferably 50 to 330 g / m ² , and preferably 60 to 260 g / m ² .

The shape of the filter medium having the pleated shape of the present invention will be described with reference to FIG. 1, which is a schematic cross-sectional view.
FIG. 1 shows a longitudinal direction (horizontal direction on the paper surface) in which mountain folds and valley folds are alternately performed in the filter medium (1), and a direction perpendicular to the direction on the paper surface (vertical direction on the paper surface). The schematic cross-sectional view of the filter medium (10) having a pleated shape is shown from the direction perpendicular to both of them (the front side direction on the paper surface).

The filter medium (10) having a pleated shape has a zigzag shape formed by alternately and repeatedly processing mountain folds and valley folds in the longitudinal direction (left-right direction on the paper surface) of the filter medium (1), and has a pleated shape. The mountain fold portion existing on the upward side on the paper surface is referred to as a pleated mountain (2), and the valley fold portion existing on the downward side on the paper surface is referred to as a pleated valley (3).
Then, when the filter medium (10) having a pleated shape is allowed to stand on a plate having a flat main surface, it is on the paper surface in a direction perpendicular to the main surface of the flat plate (vertical direction on the paper surface). The length between the pleated mountain (2) and the pleated valley (3) adjacent to each other in the left-right direction is defined as the pleated mountain height (4). That is, the filter medium (10) having a pleated shape of the present invention includes a portion having a pleated mountain height (4) of 50 mm or more.

The pleated mountain height (4) is adjusted within the range according to the present invention so that the pressure loss is lower and the high collection efficiency can be exhibited while maintaining the low pressure loss, but the pleated mountain height (4) is adjusted. It can be 60 mm or more, 80 mm or more, and 100 mm or more.
The end of the pleated ridge (2) (upward end on the paper) and / or the end of the pleated valley (3) (downward end on the paper) has a curved structure. You may be.

The filter medium (10) having a pleated shape of the present invention is a pleated portion having a pleated valley angle (5) formed between adjacent pleated peaks (2) larger than 6.6 ° and smaller than 8.8 °. It has (6).
The pleated valley angle (5) referred to in the present invention is the upward side on the paper surface of the filter medium (10) having a pleated shape due to the existence of the pleated valley (3) between the adjacent pleated peaks (2). Refers to the angle (5) formed in.

The pleated valley angle (5) can be obtained by arranging the filter medium (10) having a pleated shape as shown in FIG. 1 and actually measuring it. If it is difficult to actually measure, the thickness of the filter medium, the pleated mountain spacing (the length of the distance between adjacent pleated mountains (2) in the left-right direction on the paper), and the pleated valley spacing (adjacent pleated valley). (3) The length of the distance between each other in the left-right direction on the paper), the distance between the adjacent pleated peaks and the pleated valley (the distance between the adjacent pleated peaks (2) and the pleated valley (3) in the left-right direction on the paper surface) The pleated valley angle (5) can be calculated from the shape of the filter medium (10) having a pleated shape, such as (length) and pleated mountain height (4).

The pleated valley angle (5) can be adjusted within the range according to the present invention so that the pressure loss is lower and the collection efficiency is high while maintaining the low pressure loss, but the above-mentioned effect is more effective. The pleated valley angle (5) is preferably 6.8 ° to 8.6 °, and more preferably 6.9 ° to 8.5 ° so that the pleated valley angle (5) can be exhibited.

The pleated portion (6) referred to in the present invention is a pleated mountain (2) adjacent to the pleated valley (3) forming the pleated valley angle (5) defined by the present invention in the left-right direction on the paper surface. Refers to the range between each other.
The filter medium (10) having a pleated shape of the present invention is provided with a pleated-shaped portion (6) having such a shape, so that at least the portion (6) can be prevented from being deformed, and the pressure loss is low. A filter medium (10) having a pleated shape can be provided. The number and ratio of the portions (6) included in the filter medium (10) having a pleated shape can be appropriately selected, but any filter medium (10) having a pleated shape including one or more said portions (6) may be used. All pleated valley angles (5) in the filter medium (10) having a pleated shape so that the effect of exhibiting high collection efficiency while maintaining a lower pressure loss and a lower pressure loss is further improved. ) Is preferably larger than 6.6 ° and smaller than 8.8 °.

The filter medium having a pleated shape can be used alone, but it may be a filter medium provided with other members. For example, even if a comb-shaped member having a shape along the pleated shape of the filter medium is provided so that the pleated shape is effectively maintained, the pleated shape of the filter medium can be changed by providing a bead on the main surface of the filter medium. Even if it is held, the end plates are adhered to both side surfaces (both sides on the front side of the paper surface and the back side of the paper surface on the paper surface in FIG. 1) or all side peripheral surfaces orthogonal to the ridge line on the side peripheral surface of the pleated filter medium. The pleated shape may be maintained by integrating them. Further, the filter medium having a pleated shape can be used alone, but another breathable member may be provided as a pre-filter or a back filter. The method of laminating the filter medium having a pleated shape and another breathable member can be appropriately selected. Both layers may be bonded and integrated by fiber adhesion, or may be laminated and integrated by heat sealing, ultrasonic fusion, or pressing a heat roll.

Next, a method for producing a filter medium having a pleated shape according to the present invention will be described. The method for producing a filter medium having a pleated shape of the present invention can be appropriately selected, but as an example, the filter medium can be produced by using the methods disclosed in Patent Documents 1 to 3, specifically, the following methods.
FIG. 2 is a side view showing an example of a filter medium manufacturing apparatus capable of manufacturing the filter medium according to the present invention.

The filter medium manufacturing apparatus (20) discharges the ultrafine fiber flow (22) by directly spinning using a die (21) for a direct spinning apparatus such as a melt blow apparatus, and at the same time, with respect to the ultrafine fiber flow (22). By applying a thick fiber flow (24) that has been opened and discharged using a fiber opening machine (23) such as a card machine or a garnet machine, a fiber group (25) in which ultrafine fibers and thick fibers are mixed can be prepared.
Then, by collecting the prepared fiber group (25), which is a mixture of ultrafine fibers and thick fibers, on a collector (26) such as a roll, a net, or a conveyor belt, the ultrafine fibers and thick fibers are mixed. A fiber web or non-woven fabric (27) can be produced.

The direction and angle at which the thick fiber flow (24) is applied to the ultrafine fiber flow (22) can be appropriately selected, but when preparing a fiber layer in which the ultrafine fibers and the thick fibers are uniformly mixed, the ultrafine fibers are prepared. Apply the thick fiber flow (24) from the direction as perpendicular to the fiber flow (22) as possible (apply the thick fiber flow (24) in FIG. 2 so that the discharge angle (θ) is close to 90 °. ) Is preferable.
Further, by adjusting the discharge angle (θ) of the thick fiber flow (24) to be close to a sharp angle or an blunt angle, the distribution of the thick fibers and the ultrafine fibers existing in the thickness direction in the fiber web or the nonwoven fabric (27) can be changed. It is possible to prepare a fiber layer in which the abundance ratio of ultrafine fibers and thick fibers (ratio of existing fiber mass or ratio of number of fibers, etc.) changes and is mixed from one main surface to the other main surface.

The type of the collector (26) can be appropriately selected, but the collector (26) has air permeability so as to easily collect the fiber group (25) in which ultrafine fibers and thick fibers are mixed. Further, it is preferable to provide the suction device (28) on the opposite side of the collection surface in the collection body (26).

After that, if necessary, the manufactured fiber web or non-woven fabric (27) is entangled using a needle, a water stream, or a gas stream such as steam, a treatment for imparting functional particles such as activated carbon, a binder imparting treatment, a heat treatment, and charging. A filter medium according to the present invention (a filter medium having a fiber web or a fiber layer derived from a non-woven fabric (27) in which ultrafine fibers and thick fibers are mixed) by subjecting it to a secondary treatment step such as treatment and laminating treatment with a support. Can be manufactured.
The type of charging treatment can be appropriately selected, but a method of applying a high voltage to the fabric to charge the fabric (corona charging method) or a method of applying a force to the fabric through the polar liquid to charge the fabric (corona charging method). (Polar liquid charging method), in the case of a fiber web containing a plurality of types of fibers that can be charged by rubbing against each other, the fiber web can be deformed in the thickness direction and charged by friction.

A filter medium having a pleated shape can be produced by processing the filter medium having a fiber layer derived from the fiber web thus produced so as to have a zigzag shape and a pleated shape. The type of the processing method can be appropriately selected, and for example, a filter medium having a pleated shape can be obtained by subjecting it to a pleating machine such as a reciprocating type or a rotary type, or by applying it to a method of pressing with a stamp formed into a zigzag shape. Can be manufactured. At this time, the pleated mountain height is 50 mm or more, and the pleated valley formed between the adjacent pleated mountains has a pleated shape portion larger than 6.6 ° and smaller than 8.8 °. In addition, the filter medium is folded into a zigzag shape and has a pleated shape.

In the above description, a method of producing a filter medium having a pleated shape folded in a zigzag shape after being subjected to a secondary treatment step has been exemplified, but the manufactured filter medium having a pleated shape may be subjected to a secondary treatment step.

The filter medium having a pleated shape produced in this manner can be used alone, but may be a filter medium provided with other members. For example, even if a comb-shaped member having a shape along the pleated shape of the filter medium is provided so that the pleated shape is effectively maintained, the pleated shape of the filter medium is maintained by providing a bead on the main surface of the filter medium. Even if the pleated shape is maintained by laminating and integrating the support on the pleated filter medium, both side surfaces orthogonal to the ridge line on the side peripheral surface of the pleated filter medium. The pleated shape may be maintained by adhering and integrating end plates on the front side of the paper surface and both side surfaces on the back side of the paper surface in FIG. 1 or on all side peripheral surfaces.
Further, the filter medium having a pleated shape can be used alone, but another breathable member may be provided as a pre-filter or a back filter. The laminating method can be appropriately selected, but for example, it may be simply laminated, bonded and integrated by binder web, binder liquid, or fiber adhesion, or pressed with a heat seal, ultrasonic fusion, or heat roll. Can be laminated.

Hereinafter, the present invention will be specifically described with reference to Examples, but these do not limit the scope of the present invention.

(Preparation method of non-woven fabric)
A spinning resin made by blending 4 mass% of a hindered amine compound Kimasorb (manufactured by BASF Japan Co., Ltd., model number: Kimasorb 944FDL, registered trademark) with 96 mass% of polypropylene resin is melt-injected from a die for a heated melt blow device. By doing so, melt spinning (direct spinning method) was performed to form an ultrafine fiber flow.
Next, it is opened so as to form an angle of 65 ° with respect to the formed ultrafine fiber flow in the direction in which the ultrafine fibers are melt-injected (the discharge angle (θ) of the thick fiber flow (24) in FIG. 2). By applying a thick fiber flow formed by discharging a composite fiber (average fiber diameter: 30 μm, fiber length: 64 mm) whose core component is made of polypropylene resin and whose sheath component is made of polyethylene resin from the fiber machine, ultrafine fibers and thick fibers are made. A mixed fiber group was prepared and collected on a mesh-like conveyor to prepare a non-woven fabric (grain: 80 g / m ² , thickness: 0.75 mm, production width: 620 mm).
In collecting the fiber group, a suction device was provided on the opposite side of the collection surface of the mesh conveyor, and the fiber group was collected while sucking and removing air from the opposite side of the collection surface of the mesh conveyor.

In the nonwoven fabric thus prepared, the ultrafine fibers having a continuous length having an average fiber diameter of 2.5 μm and the thick fibers of the short fibers having an average fiber diameter of 30 μm are ultrafine fibers: thick fibers = 7 mass%: 93 mass%. It was a mixture.
Further, 50 mass% (thick fibers: 50 mass%) of ultrafine fibers are present on the main surface of the non-woven fabric on the collection surface side of the mesh conveyor, and the ultrafine fibers are present on the main surface facing the main surface on the collection surface side. The fiber was present in 3 mass% (thick fiber: 97 mass%). Then, the amount of ultrafine fibers gradually decreased and the amount of thick fibers gradually increased from the main surface on the collection surface side of the nonwoven fabric toward the opposite main surface.

(How to charge the non-woven fabric)
A charged non-woven fabric was prepared by subjecting the non-woven fabric to a corona discharge treatment (DC voltage: 8.5 kV).

(Examples and comparative examples)
By supplying the charged non-woven fabric prepared as described above to a pleating machine, mountain folds and valley folds are alternately and repeatedly processed in the longitudinal direction of the charged non-woven fabric to fold it so as to have a zigzag shape. A filter medium having a pleated shape was prepared.
As for how to fold the charged nonwoven fabric, by changing the distance between adjacent pleated ridges and the height of the pleated ridges as shown in Table 1, a charged filter medium having a pleated shape as an example or a comparative example can be obtained. Prepared.
Moreover, the performance as a filter medium was evaluated by subjecting the prepared charged filter medium having each pleated shape to the following (method for measuring initial pressure loss).

(Measurement method of initial pressure loss)
By attaching end plates as frame members to all side peripheral surfaces of the charged filter media having each pleated shape, the charged filter media having each pleated shape was finished into a filter unit having a frontage area of 610 mm square. Then, each of the prepared filter units is subjected to an initial pressure loss (Pa) based on the test method type 2 specified in JIS B 9908 (2001) "Ventilation air filter unit / ventilation electrostatic collector performance test method". It was measured.

Table 1 summarizes the configurations of the charged filter media having each pleated shape as examples and comparative examples, and the measurement results of the initial pressure loss (Pa).

From the results in Table 1, when the pleated valley angle was larger than 6.6 ° and had a pleated-shaped portion smaller than 8.8 °, the charged filter medium having the pleated shape had a low initial pressure loss.
Therefore, according to the present invention, it is possible to provide a filter medium having a pleated shape having a pleated mountain height of 50 mm or more, which has a lower pressure loss and can exhibit high collection efficiency while maintaining a low pressure loss.

The present invention relates to, for example, food and medical product production factory applications, precision equipment manufacturing factory applications, indoor cultivation facility applications for agricultural products, general household applications or industrial facility applications such as office buildings, air purifier applications, OA equipment applications, etc. It can be suitably used as a gas or liquid filter medium in various vehicle applications such as automobiles and aircraft.

10 ... Filter material having a pleated shape 1 ... Filter material 2 ... Pleated mountain 3 ... Pleated valley 4 ... Pleated mountain height 5 ... Pleated formed between adjacent pleated mountains Valley angle 6 ... Pleated shape part 20 ... Filter material manufacturing equipment 21 ... Die for direct spinning equipment 22 ... Extra-fine fiber flow 23 ... Fiber opener 24 ... Thick fiber flow 25 ...・ ・ Fiber group 26 in which ultrafine fibers and thick fibers are mixed ・ ・ ・ Collector 27 ・ ・ ・ Fiber web or non-woven fabric in which ultrafine fibers and thick fibers are mixed 28 ・ ・ ・ Suction device

Claims (1)

A filter medium having a pleated shape having the following configurations.
(1) The filter medium having a pleated shape is composed only of a fiber layer composed of a mixture of ultrafine fibers and thick fibers.
(2) The average fiber diameter of the ultrafine fibers constituting the fiber layer is 0.1 to 10 μm, and the average fiber diameter of the thick fibers constituting the fiber layer is larger than the average fiber diameter of the ultrafine fibers.
(3) The height of the pleated ridge of the filter medium having a pleated shape is 50 mm or more.
(4) The filter medium having a pleated shape has a pleated-shaped portion in which the angle of the pleated valley formed between the adjacent pleated mountains is larger than 6.6 ° and smaller than 8.8 °.

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