JP2019042703A - Filter medium having pleat shape - Google Patents

Abstract

To provide a filter medium having a pleat shape of which a pleat crest height is 50 mm or more, which is low in pressure loss and can exhibit a high collection efficiency in a state that a low pressure loss is maintained.SOLUTION: A filter medium having a pleat shape has the following configuration: (1) a filter medium having a pleat shape comprises a fiber bed in which ultra fine fibers and thick fibers are mixed; (2) an average fiber diameter of the ultra fine fiber, which constitutes the fiber bed, is 0.1 to 10 μm, and an average fiber diameter of the thick fiber, which constitutes the fiber bed, is thicker than the average fiber diameter of the ultra fine fiber; and (3) a pleat crest height of the filter medium having the pleat shape is 50 mm or more. The filter medium has a pleat shape part of which a pleat valley angle is larger than 6.6° and smaller than 8.8°, whereby a filter medium having a pleat shape which is lower in a pressure loss such as an initial pressure loss, and further, can exhibit a high collection efficiency in a state that a low pressure loss is maintained can be provided.SELECTED DRAWING: Figure 1

Description

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

BACKGROUND ART Conventionally, in order to collect dust in a fluid such as a gas or a liquid, for example, a filter medium made of a sheet-like cloth such as a non-woven fabric, a woven fabric or a knitted fabric is used. The filter medium is required to have low pressure loss such as initial pressure loss and to be able to exhibit high collection efficiency while maintaining low pressure loss.
In order to provide a filter medium satisfying the above-mentioned requirements, the applicant of the present invention has so far disclosed Japanese Patent Application Laid-Open Nos. 11-104417 (Patent Document 1), 2014-004555 (Patent Document 2), 2014-184360 The filter medium which has a pleat shape provided with the following structures as described in the gazette (patent document 3) etc. was proposed.
(1) It is equipped with a fiber layer formed 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 thicker than the average fiber diameter of the ultrafine fibers.
The pleated filter media having the configurations (1) and (2) described above have a unit area per unit area when the pleated filter media is viewed from the filtration upstream side (upward direction on the sheet of FIG. 1 described later). The pressure loss such as initial pressure loss is low because of the large area of the filter media present in the fiber, and the low pressure loss is maintained because the fiber layer is formed by mixing ultrafine fibers and thick fibers having the above-mentioned average fiber diameter. High collection efficiency can be exhibited in the state.

Japanese Patent Application Laid-Open No. 11-104417 JP, 2014-004555, A JP, 2014-184360, A

However, as disclosed in Patent Document 2 (Paragraph No. 0002) and Patent Document 3 (Paragraph No. 0002), the filter medium provided with the above-described configurations (1) and (2) is pleated with a peak height of 50 mm or more In the case of the shape, adjacent filter media easily adhere to each other, and the filter media were deformed.
As a result, large structural pressure loss occurred in the pleated filter medium, and the pleated filter medium had high pressure loss.

In the present invention, it is a first object of the present invention to provide a filter medium having a pleat shape having a pleat height of 50 mm or more and capable of exhibiting high collection efficiency while maintaining lower pressure loss and maintaining low pressure loss.

The present invention
"A pleated filter media with the following configuration.
(1) The pleated filter medium is provided with a fiber layer in which microfibers and large 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 thicker than the average fiber diameter of the ultrafine fibers,
(3) The pleat height of the pleated filter medium is 50 mm or more,
(4) The filter medium having a pleated shape has a pleated portion in which the angle of the pleated valley formed between adjacent pleats is larger than 6.6 ° and smaller than 8.8 °.
It is.

In a filter medium having a pleated shape having a configuration of (1) to (3) as in the present invention, in order to prevent adjacent filter media from adhering to each other, an angle of a pleat valley formed between adjacent pleat peaks If the size (hereinafter referred to as the pleat valley angle) is increased, the pressure loss becomes high as the area of the filter medium present per unit area is narrowed.
On the other hand, in the filter medium having a pleated shape having the configuration of (1) to (3) as in the present invention, when the pleat valley angle is reduced in order to widen the filter medium area existing per unit area, adjacent filter media Since it is easier to be in close contact, a large deformation occurs in the filter medium, and the pressure loss becomes high as the structural pressure loss increases.
Therefore, in a filter medium having a pleated shape having a configuration of (1) to (3) as in the present invention, it has been considered that an increase in pressure loss can not be avoided regardless of how the pleat valley angle is adjusted. .

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

It is a schematic cross section of the filter medium which has a pleat shape which concerns on this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a side view which shows an example of the manufacturing apparatus of a filter medium which can manufacture the filter medium concerning this invention.

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

The filter medium which concerns on this invention is equipped with the fiber layer which an ultrafine fiber and a thick fiber are mixed.
The term "fiber layer" as used herein 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 a mode of a fiber layer, even if it is a fiber layer which an ultrafine fiber and a thick fiber mix uniformly, a fiber layer formed by an ultrafine fiber and a thick fiber mixed unevenly may be sufficient. As the fiber layer formed by mixing nonuniformly, for example, the ratio of the number of ultra-fine fibers to the number of fibers or the ratio of the number of fibers or the like from the one main surface to the other main surface in the fiber layer ) May be changed. A specific example can be an aspect in which the abundance ratio of microfibers decreases and the abundance ratio of thick fibers increases from one major surface to the other major surface.

The ultrafine fibers which are constituent fibers of the fiber layer are, for example, polyolefin resins (polyethylene, polypropylene, polymethylpentene, polyolefin resins having a structure in which a part of hydrocarbon is substituted with cyano group or halogen such as fluorine or chlorine), Styrene resin, polyether resin (polyether ether ketone, polyacetal, phenol resin, melamine resin, urea resin, epoxy resin, modified polyphenylene ether, aromatic polyether ketone, etc.), polyester resin (polyethylene terephthalate) , Polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polycarbonate, polyarylate, wholly aromatic polyester resin, unsaturated polyester resin Etc.), polyimide-based resin, polyamide-imide resin, polyamide-based resin (eg, aromatic polyamide resin, aromatic polyetheramide resin, nylon resin, etc.), resin having a tolyl group (eg, polyacrylonitrile, etc.), urethane resin Resin, epoxy resin, polysulfone resin (polysulfone, polyether sulfone, etc.), fluorine resin (polytetrafluoroethylene, polyvinylidene fluoride, etc.), cellulose resin, polybenzimidazole resin, acrylic resin (eg, acrylic acid) It is possible to use a fiber provided with a known resin such as polyacrylonitrile resin obtained by copolymerizing ester or methacrylic ester or the like and moda acrylic resin obtained by copolymerizing acrylonitrile and vinyl chloride or vinylidene chloride.
The above-mentioned resin may be made 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 any. Furthermore, a plurality of resins may be mixed.

In particular, the ultra-fine fiber contains a volume resistivity 10 ¹⁴ Ω · cm or more resins (more preferably, the volume resistivity 10 ¹⁴ Ω · cm or more when only and a resin), the charge amount Can be provided, which is preferable because it can provide a charged filter medium having a pleated shape excellent in filtration performance.
As a resin having a volume specific resistance value of 10 ¹⁴ Ω · cm or more, for example, polyolefin resin (for example, polyethylene resin, polypropylene resin, polymethylpentene resin, polystyrene resin, etc.), polytetrafluoroethylene, poly Vinylidene chloride, polyvinyl chloride, polyurethane and the like can be mentioned.
In order to further increase the charge amount of the ultrafine fibers, it is preferable to mix a charging aid with a resin (in particular, a resin having a volume specific resistance of 10 ¹⁴ Ω · cm or more) contained in the ultrafine fibers.

As the charging assistant, for example, one or two selected from hindered amine compounds, aliphatic metal salts (eg, magnesium salts of stearic acid, aluminum salts of stearic acid, etc.), 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 specific examples thereof include, 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) -4-hydroxy-2,2,6,6-tetramethylpiperidine succinate, 2- (3,5-di-t-butyl-4-hydroxybenzyl) And n-butyl malonate bis (1,2,2,6,6-pentamethyl-4-piperidyl) and the like.
The addition mass of the charging aid to be added to the resin is not particularly limited, but if the addition mass of the charging aid is too small, the charging effect in the fiber layer may be smaller than expected. In addition, when the addition amount of the charging aid is too large, the strength of the fiber layer may be deteriorated. Therefore, the addition mass of the charging aid is preferably 0.01 mass% to 5 mass% with respect to the mass 100 mass% of the resin.

  The ultrafine fibers may be composed of one type of resin or may be composed of plural types of resins. As a fiber aspect comprised from several types of resin, it can be fiber aspect, such as core-sheath type, a sea island type, a side-by-side type, an orange type, a bimetal type, generally called composite fiber, for example.

The ultrafine fibers may contain modified cross-section fibers in addition to fibers having a substantially circular cross-sectional shape and fibers having an oval shape. In addition, as irregular shape fiber, polygonal shape such as triangular shape, alphabet letter shape such as Y shape, irregular shape, multi-leaf shape, symbol shape such as asterisk shape, or a shape in which a plurality of these shapes are combined Etc. can be exemplified.

The fiber length of the ultrafine fiber is not particularly limited, but a short fiber or a long fiber having a specific measurable length, or a fiber length having a length substantially difficult to measure the fiber length Can be a continuous fiber.
When the ultrafine fibers have a continuous length, the rigidity of the fiber layer is likely to be improved, so that the deformation of the filter medium can be prevented by the excellent strength, and a filter medium with low pressure loss can be provided, which is preferable. Therefore, the fiber layer preferably contains microfibers having a continuous length as constituent fibers. In addition, the fiber which has continuous length can be manufactured using a direct spinning method.

The average fiber diameter of the microfibers constituting the fiber layer is 0.1 to 10 μm. If the average fiber diameter of the ultrafine fibers is outside this range, it will be difficult to provide a fiber layer that can constitute a filter medium that can exhibit high collection efficiency while maintaining low pressure loss. The average fiber diameter of the microfibers constituting the fiber layer is preferably 0.25 to 5 μm so as to provide a fiber layer capable of constituting a filter medium capable of exhibiting high collection efficiency while maintaining low pressure loss. And 0.5 to 4 μm are more preferable.

The “average fiber diameter” as referred to herein can be calculated based on a 1000 × electron photomicrograph of a portion to be measured including fibers such as the surface or cross section of the filter medium or fiber layer. Specifically, 200 points of fibers (such as ultrafine fibers or thick fibers) whose average fiber diameter is to be calculated are selected from electron micrographs, and the arithmetic mean value of the respective fiber diameters of the selected fibers is taken 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 points of fibers having a continuous length are selected from the electron micrograph and each fiber diameter of the selected fibers The average fiber diameter of the ultrafine fibers constituting the fiber layer can be determined by calculating the arithmetic mean value of

Ultrafine fibers are produced, for example, by melt spinning method, dry spinning method, wet spinning method, direct spinning method (melt blow method, spun bond method, electrostatic spinning method, method of spinning using centrifugal force, JP-A-2011-012372) The method of spinning by using the accompanying air current described in JP-A-2005-250324, the neutralization spinning method described in JP-A-2005-264374, etc.), the fiber having a thin fiber diameter by removing one or more kinds of resin components from the composite fiber Can be obtained by a known method such as a method of extracting
In particular, the microfibers are directly spun so that a fiber layer capable of improving the filtration performance of a pleated filter medium can be constituted by the uniform dispersion and presence of fibers despite the fact that the fiber diameter is small and the fabric weight is light. Preferably it is prepared using a method.

  The constitution and production method of the thick fiber which is the constituent fiber of the fiber layer can be appropriately selected in the same manner as the constitution of the ultrafine fiber described above, but the thick fiber is preferably a fiber containing a thermoplastic resin. When the large fibers contain a thermoplastic resin, the large fibers and the ultrafine fibers and / or the large fibers can be fiber-bonded to each other by the thermoplastic resin, so that a fiber layer having a relatively rough space can be provided. By providing a fiber layer having a relatively rough space, a filter medium with low pressure loss can be provided, which is preferable.

As an embodiment of a large fiber having such thermal adhesive performance, for example, (1) a resin component of high melting point is used as a core component, and a resin component (fusion component) of melting point lower than this high melting resin component is a sheath component Core-sheath type large fiber or eccentric type large fiber, (2) side-by-side type large 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, (3) A low-melting resin component may be a sea-island thick fiber or the like in which a large number of resin components having a higher melting point than the low-melting resin component are scattered. Among these, in order to easily form a fiber layer having a relatively rough space, the large fiber is preferably a core-sheath type large fiber, an eccentric type large fiber, or a sea-island type large fiber having the above-described configuration.
In addition, when the thick fiber is a fiber (stretched fiber) mechanically subjected to a stretching process after spinning, a fiber layer excellent in strength and rigidity can be provided, which is preferable.

The fiber length of the thick fiber can be appropriately selected as in the above-described ultrafine fiber, but the thick fiber has a specific length that can be measured so that the fiber layer formed by mixing with the ultrafine fiber can be provided. It is preferable that they are short fibers or long fibers having In particular, even in the case where an ultrafine fiber having a continuous length is employed, a fiber layer can be provided in which the ultrafine fiber and the large fiber are mixed in an intended manner because the ultrafine fiber and the large fiber are easily mixed. Preferably, the heavy fibers are short fibers or long fibers having a specific length that can be measured. The fiber length of the large fiber can be selected as appropriate, but is preferably 5 to 160 mm, more preferably 25 to 110 mm so as to be easily entangled with the microfiber.

  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 fiber is a fiber having a continuous length and the thick fiber is a short fiber or a long fiber, 200 points of the short fiber or the long fiber are selected from the electron micrograph and each diameter of the selected fibers The average fiber diameter of the thick fiber which comprises a fiber layer can be calculated | required by calculating the arithmetic mean value of.

The average fiber diameter of the thick fiber can be appropriately selected as long as it is thicker than the ultrafine fiber, but specifically, it can be thicker than 10 μm and not more than 100 μm. When the average fiber diameter of the thick fibers is 10 μm or less, it becomes difficult to provide a fiber layer that can constitute a filter medium that can exhibit high collection efficiency while maintaining low pressure loss. When the average fiber diameter exceeds 100 μm, the space is too large, which tends to make it difficult to provide a fiber layer capable of forming a filter medium capable of collecting fine dust. Therefore, it is preferable that the average fiber diameter of the thick fiber which comprises a fiber layer is 15-70 micrometers, and it is more preferable that it is 15-55 micrometers.

The mass percentage of the microfibers 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 possibility that fine dust can not be collected due to the small amount of the ultrafine fibers, while if it exceeds 40 mass%, the coarse dust may cause eye contact immediately There is a risk of getting stuck. Therefore, the mass percentage of the ultrafine fibers in the fiber layer is more preferably 3 to 35 mass%, and still more preferably 4 to 30 mass%.

The fiber layer may be composed of entangled microfibers and large fibers. The method of entanglement can be selected as appropriate, but it can be a fiber layer in which constituent fibers are entangled by a needle, a water stream, or a gas stream such as water vapor.
In addition, the fiber layer may be configured by melting a part of the ultrafine fibers and / or the large fibers and melting and integrating the fibers, or by bonding and integrating the fibers with a binder. In particular, when microfibers and / or large fibers are partially melted and the fibers melt and integrate, it is possible to prevent the pressure loss of the filter medium from increasing due to the presence of the binder, and the fibers are detached from the filter medium It is preferable because it can prevent the filtration performance from decreasing.

The thickness of the fiber layer may be appropriately selected but may be 0.1 to 10 mm. If the thickness of the fiber layer is less than 0.1 mm, it is difficult to form a relatively rough space by thick fibers, so the pressure loss tends to be high, and if the thickness is more than 10 mm, there are many parts not involved in filtration Tend. Therefore, the thickness is more preferably 0.2 to 5 mm, and still more preferably 0.5 to 4 mm. The “thickness” in the present invention refers to the load direction (thickness) of the measurement object when 20 g per unit area of ² cm ² is loaded from the main surface of the measurement object such as a fiber layer or a filter medium to the other main surface. Direction) length.

Although the fabric weight of a fiber layer selects suitably, it can be 30-300 g / m < ² >. If the fabric weight of the fiber layer is less than 30 g / m ² , the thickness and density tend to be too small to make it difficult to collect fine dust, and if the fabric weight exceeds 300 g / m ² , the thickness and thickness There is a tendency that the density becomes too large and clogging is immediately caused by coarse dust, and the pressure loss tends to increase. Therefore, the basis weight is more preferably from 40~250g / ^{m 2,} and even more preferably 50 to 200 g / ^{m 2.}

The apparent density of the fiber layer can be selected as appropriate, but it can be 0.003 to ³ g / cm ³ . If the apparent density is less than 0.003 g / cm ³ , it will tend to be difficult to collect fine dust, and if the apparent density exceeds ³ g / cm ³ , coarse dust will immediately make it noticeable. The clogging tends to occur and the pressure loss tends to increase. 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 the fiber layer, it is formed by laminating a support separately prepared for the fiber layer (for example, a fiber web, a non-woven fabric, a fabric such as a knitted fabric or a woven fabric, a film, a porous plate, etc.) You may be comprised from the laminated body. It is preferable to adopt a spunbond non-woven fabric as a support since a filter medium having excellent rigidity can be provided by reinforcing the fiber layer. Reinforcement of the fiber layer prevents adjacent filter media from adhering to each other when the filter media is pleated, preventing deformation of the filter media, and providing a filter media having a pleated shape with low pressure loss.
In particular, even in the case of a filter medium having a pleat shape that is more easily deformed such that the peak height is 50 mm or more (particularly, 100 mm or more), adjacent filter media hardly adhere to each other to prevent deformation of the filter medium Thus, a filter medium having a pleated shape with low pressure loss can be provided.

  Although the fineness of the constituent fibers in the support is appropriately selected, the smaller the value of fineness tends to improve the collection efficiency of the filter medium, but if the value of fineness is too small, the pressure loss of the filter medium may be excessively high. is there. Therefore, the fineness of constituent fibers in the support is preferably 1 to 100 dtex, preferably 2 to 50 dtex, and more preferably 3 to 30 dtex.

Although the weight of the support can be appropriately selected, the lighter the weight, the lower the pressure loss of the filter medium. However, if the weight is too light, the fiber layer can not be effectively reinforced and it becomes difficult to provide a rigid filter. there is a possibility. Therefore, it is preferred basis weight of the support is 20 to 200 g / ^{m 2,} is preferably from 30 to 150 g / ^{m 2,} preferably from 40 to 100 g / ^{m 2.}

  Although the thickness of a support body can be selected suitably, it can be 0.1-2 mm, can be 0.15-1.5 mm, and can be 0.2-1 mm.

Although the method of laminating the fiber layer and the support can be appropriately selected, for example, even in the embodiment in which only the fiber layer and the support are simply laminated, a binder web, a binder solution or a fiber layer The two layers may be bonded and integrated by fiber bonding with the component fibers of the support, or may be laminated and integrated by pressing a heat seal, ultrasonic fusion, or a heat roll.
If the fiber layer and the support are laminated by the binder, but the applied amount of the binder may be appropriately selected, amount of binder may be 1 to 30 g / m ^2, it can be a 2 to 20 g / m ² , 3-15 g / m ² can be.
Also, when the fiber layer and the support are bonded and integrated by bonding the fibers of the fiber layer and / or the constituent fibers of the support, the air permeability of the fiber layer and the support is due to the adhesive component such as the binder. It is preferable because it can prevent clogging and increase in pressure loss of the filter medium.

The fiber layer and / or the support may contain functional particles, a binder, a pigment and the like.
As functional particles, for example, radioactive substance adsorbents (eg, zeolite, activated carbon, bitumen (Prussian blue), etc.), antibacterial agents, antiviral agents, antifungal agents, catalysts (eg, titanium oxide, manganese dioxide or platinum-supporting alumina) Etc.), moisture control agents (eg, silica gel and silica microcapsules), deodorizers such as activated carbon and carbon black, pigments, phosphoric acid flame retardants, flame retardants such as aluminum hydroxide, deodorants, insect repellents, sterilization And particles such as agents, fragrances, cation exchange resins and anion exchange resins.
The functional particles and pigments may be present as supported or adhered to the fiber layer and / or the support as described above, but they are mixed into the fibers constituting the fiber layer and / or the support. It may be an aspect that

The filter medium is preferably charged so as to provide a filter medium capable of exhibiting high collection efficiency while maintaining low pressure loss and maintaining low pressure drop. As a means for charging the filter medium, for example, a known means such as a plasma charging means, a corona charging means, a means for charging by applying a force through a polar liquid, a means for frictionally charging a plurality of fiber components, etc. It can be used selectively or in combination.
The charged filter medium may be a charged filter medium comprising a charged fiber layer and / or a charged support, or may be a charged filter medium formed by charging the prepared filter medium.

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

Although the basis weight of the filter medium can be appropriately selected, the heavier the basis weight, the more easily providing a filter medium with excellent rigidity, but if the basis weight is too heavy, the pressure loss of the filter medium may increase. Therefore, it is preferred basis weight of the filter medium is 35~400g / ^{m 2,} is preferably from 50~330g / ^{m 2,} preferably from 60~260g / ^{m 2.}

The shape of the filter medium having a 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 at the time of seeing the filter medium (10) which has pleat shape from the direction (front side direction on a paper surface) perpendicular | vertical to both is shown in figure.

The pleated filter medium (10) has a zigzag shape in which a mountain fold and a valley fold are repeatedly processed alternately in the longitudinal direction (left and right direction on the drawing) of the filter medium (1). A mountain-folded portion present on the upper side of the paper surface of the filter medium (10) has a pleated peak (2), and a valley-folded portion present on the lower side of the paper surface is a pleated valley (3).
Then, when the pleated filter medium (10) is placed 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 pleat mountain (2) and the pleat valley (3) adjacent to each other in the left-right direction is taken as the pleat mountain height (4). That is, the filter medium (10) having a pleated shape of the present invention is provided with a portion having a pleat peak height (4) of 50 mm or more.

The pleat height (4) is adjusted within the range according to the present invention so that high collection efficiency can be exhibited while maintaining a low pressure loss and maintaining a low pressure loss, but the pleat height (4) is It can be 60 mm or more, can be 80 mm or more, and can be 100 mm or more.
The end of the pleat peak (2) (upper end on the sheet) and / or the end of the pleat valley (3) (lower end on the sheet) have a curved structure. May be

The filter medium (10) having the pleated shape of the present invention is a pleated portion having a pleated valley angle (5) formed between adjacent pleat peaks (2) of more than 6.6 ° and less than 8.8 °. It has (6).
The pleat valley angle (5) as referred to in the present invention means that the pleat valley (3) exists between adjacent pleat peaks (2), whereby the upward direction side on the paper surface of the filter medium (10) having a pleat shape Point to the angle (5) formed on

  The pleated valley angle (5) can be determined by arranging and measuring the pleated filter medium (10) as shown in FIG. When measurement is difficult, the thickness of the filter medium, pleat ridge interval (the length between adjacent pleat ridges (2) in the horizontal direction on the paper surface), pleat valley interval (adjacent pleat valley) (3) The length between the adjacent pleat peaks and the pleat valley (the length between the adjacent pleat peaks (2) and the pleat valley (3) on the page) The pleat valley angle (5) can be calculated from the shape of the filter medium (10) having a pleated shape, such as the length in (4) and the pleat peak height (4).

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

The pleated portion (6) referred to in the present invention is a pleated peak (2) which is 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. Refers to the range between each other.
By providing the pleated portion (6) having such a shape, the filter medium (10) having the pleated shape of the present invention can prevent deformation of at least the portion (6), and the pressure loss is low. A filter medium (10) having a pleated shape can be provided. In addition, although the number and ratio of this part (6) with which the filter medium (10) which has a pleat shape is equipped can be selected suitably, it is good if it is a filter medium (10) which has a pleat shape provided with one or more said parts (6). All pleated valley angles (5 in the pleated filter medium 10) such that the effect of exhibiting high collection efficiency while maintaining low pressure loss and low pressure loss is further improved Preferably,) is more than 6.6 ° and less than 8.8 °.

The pleated filter medium may be used alone, but may be a filter medium provided with other members. For example, even if a comb-like member having a shape along the pleated shape of the filter medium is provided so that the pleated shape is effectively retained, the pleated shape of the filter medium is provided by providing the bead on the main surface of the filter medium Even if it is held, the end plates adhere to the side surfaces of the side peripheral surface of the pleated filter media that are orthogonal to the ridgelines (the both side surfaces on the front and back sides of the paper in the paper of FIG. 1) The pleat shape may be maintained by unifying. Moreover, although the filter medium which has pleat shape can also be used alone, you may equip another air-permeable member as a prefilter or a back filter. A lamination method of the filter medium having a pleated shape and another air-permeable member can be selected as appropriate, but, for example, even if it is an embodiment in which only lamination is performed, other than that, a binder web, a binder solution or constituent fibers The two layers may be bonded and integrated by fiber bonding, or may be laminated and integrated by pressing a heat seal, ultrasonic fusion, or a heat roll.

Next, the method for producing a filter medium having a pleated shape according to the present invention will be described. Although the manufacturing method of the filter medium which has a pleat shape of this invention can be selected suitably, a filter medium can be manufactured using the method of an indication to patent document 1-3, specifically, the following method as an example.
FIG. 2: is a side view which shows an example of the manufacturing apparatus of a filter medium which can manufacture the filter medium which concerns on this invention.

The filter medium manufacturing apparatus (20) discharges the microfiber stream (22) by direct spinning using a die (21) for a direct spinning apparatus such as a meltblowing apparatus, and for the microfiber stream (22), By applying the thick fiber stream (24) opened and discharged using an opener (23) such as a card machine or a garnet machine, it is possible to prepare a fiber group (25) composed of a mixture of ultrafine fibers and thick fibers.
Then, by collecting the prepared fiber group (25) consisting of a mixture of ultrafine fibers and large fibers on a collection body (26) such as a roll, a net or a conveyor belt, the ultrafine fibers and large fibers are mixed. A fibrous 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 selected as appropriate, but in the case of preparing a fiber layer in which the ultrafine fibers and the thick fibers are uniformly mixed, The thick fiber flow (24) is applied to the fiber flow (22) from a direction as perpendicular as possible (the discharge angle (θ) of the thick fiber flow (24) in FIG. 2 is close to 90 °) Is preferred.
In addition, by adjusting the discharge angle (θ) of the thick fiber flow (24) to an acute angle or an obtuse angle, the distribution of the thick fibers and the ultrafine fibers in the thickness direction in the fiber web or nonwoven fabric (27) is changed. From one main surface to the other main surface, it is possible to prepare a fiber layer in which the abundance ratio of ultrafine fibers and large fibers (such as the ratio of the amount of fibers present or the ratio of the number of fibers) changes and is mixed.

  The type of collecting body (26) can be selected appropriately, but the collecting body (26) has air permeability so that it is easy to collect the fiber group (25) formed by the mixture of ultrafine fibers and large fibers. Preferably, the suction device (28) is provided on the opposite side of the collecting surface of the collecting body (26).

Then, if necessary, the produced fiber web or non-woven fabric (27) may be entangled with a needle, water stream or gas stream such as water vapor, application of functional particles such as activated carbon, binder application, heat treatment, charging Filter medium according to the present invention (filter medium having a fiber web derived from a mixture of ultrafine fibers and large fibers or a nonwoven fabric (27)) by being subjected to secondary treatment processes such as treatment and lamination with a support Can be manufactured.
The type of electrification treatment can be selected as appropriate, by applying a high voltage to the fabric for charging (corona charging method) or applying a polar liquid to the fabric and applying force via the polar liquid to electrify the fabric ( Polar Liquid Charging Method) In the case of a fibrous web containing a plurality of types of fibers that can be charged by rubbing each other, the fibrous web can be subjected to a method of deforming in the thickness direction and charging it by friction.

  A filter medium having a pleated shape can be manufactured by processing the filter medium having the fiber layer derived from the fiber web produced in this manner into a zigzag shape so as to have a pleated shape. The type of the processing method can be appropriately selected, but for example, the filter medium having a pleated shape can be provided by being provided to a pleating machine such as a reciprocating type or a rotary type, or by using a pressing method formed in a zigzag shape. It can be manufactured. At this time, it has a pleated shape having a pleated peak height of 50 mm or more, and has a pleated portion having an angle of a pleated valley formed between adjacent pleated peaks larger than 6.6 ° and smaller than 8.8 °. Then, the filter medium is folded in a zigzag shape and has a pleated shape.

In addition, although the method to manufacture the filter medium which has a fold pleat shape in zigzag shape after providing to a secondary treatment process was illustrated above, you may provide the filter medium which has the manufactured pleat shape to a secondary treatment process.

The filter medium having a pleated shape manufactured in this manner can be used alone, but may be a filter medium provided with other members. For example, even if a comb-like member having a shape along the pleated shape of the filter medium is provided so that the pleated shape is effectively retained, 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 integrally laminating the support on the pleated filter medium, the side surfaces of the side circumferential surface of the pleated filter medium may be orthogonal to the ridges. The pleated shape may be maintained by bonding and integrating end plates (all sides on the front side and the rear side of the drawing sheet in FIG. 1) or on all side peripheral surfaces.
Moreover, although the filter medium which has pleat shape can also be used alone, you may provide another air-permeable member as a prefilter or a back filter. The lamination method can be selected as appropriate, but, for example, an embodiment in which only lamination is performed, bonding and integration are carried out by binder web, binder liquid or fiber adhesion, or heat seal, ultrasonic fusion or heat roll is pressed, etc. Can be stacked.

  Hereinafter, the present invention will be specifically described by way of examples, but these do not limit the scope of the present invention.

(Method of preparing non-woven fabric)
Melting injection from a die for a melt-blowing apparatus, in which a resin for spinning is prepared by blending 4 mass% of chimasorb of a hindered amine compound (BASF Japan KK, model number: Chimasorb 944 FDL, registered trademark) with 96 mass% of polypropylene resin. By melt spinning (direct spinning method), an ultrafine fiber stream was formed.
Then, an angle of 65 ° (a discharge angle (θ) of the thick fiber flow (24) in FIG. 2) is opened with the direction in which the microfiber is melted and injected with respect to the formed microfine fiber flow. By applying a thick fiber flow 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 large fibers are produced. A non-woven fabric (weight: 80 g / m ² , thickness: 0.75 mm, production width: 620 mm) was prepared by preparing a mixed fiber group and collecting it on a mesh conveyor.
In addition, in collecting the fiber group, a suction device was provided on the opposite side of the collecting surface of the mesh conveyor, and the fiber group was collected while sucking and removing air from the opposite side of the collecting surface of the mesh conveyor.

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

(Method of charging nonwoven fabric)
The non-woven fabric was subjected to corona discharge treatment (DC voltage: 8.5 kV) to prepare a charged non-woven fabric.

(Example and Comparative Example)
By supplying the charged non-woven fabric prepared as described above to a pleating machine, it is repeatedly processed alternately in a mountain fold and a valley fold in the longitudinal direction of the charged non-woven fabric so that it has a zigzag shape, A filter media having a pleated shape was prepared.
In addition, about the fold method of the charged nonwoven fabric, the charged filter medium which has a pleat shape used as an Example or a comparative example by each changing the space | interval of pleat ridges which adjoin as Table 1 and pleat ridge height each becomes. Prepared.
Moreover, the performance as a filter medium was evaluated by using the charged filter medium which has each pleat shape prepared as follows (measurement method of initial stage pressure loss).

(Measurement method of initial pressure loss)
By attaching an end plate as a frame material to all side peripheral surfaces of the charged filter media having each pleat shape, the charged filter media having each pleat shape are finished into a filter unit having a 610 mm square opening area. Then, based on the test method type 2 specified in JIS B 9908 (2001) “Performance test method for air filter unit for ventilation and electric dust collector for ventilation”, each filter unit prepared was evaluated as initial pressure loss (Pa) It was measured.

Table 1 summarizes the configuration of the charged filter media having pleat shapes that serve as the example and the comparative example, and the measurement results of the initial pressure loss (Pa).

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

The present invention is used, for example, in production plant applications for food and medical products, in manufacturing plants for precision instruments, in indoor cultivation facilities for agricultural crops, in general household applications or industrial facilities such as office buildings, in air cleaner applications and OA equipment applications, etc. It can be suitably used as a gas or liquid filter medium in electric appliance applications of the above, and various vehicle applications such as automobiles and aircraft.

10 ... filter medium 1 having a pleated shape 1 ... filter medium 2 ... pleated mountain 3 ... pleated valley 4 ... pleated mountain height 5 ... pleat formed between adjacent pleated mountains Angle of valley 6 ... pleated portion 20 ... manufacturing device of filter medium 21 ... die 22 for direct spinning device ... ultrafine fiber stream 23 ... opening machine 24 ... thick fiber stream 25 · · Fiber group 26 consisting of a mixture of ultrafine fibers and large fibers · · · Collection body 27 · A fiber web or non-woven fabric 28 consisting of a mixture of ultrafine fibers and large fibers · · · Suction device

Claims (1)

A pleated filter media having the following configuration.
(1) The pleated filter medium is provided with a fiber layer in which microfibers and large 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 thicker than the average fiber diameter of the ultrafine fibers,
(3) The pleat height of the pleated filter medium is 50 mm or more,
(4) The filter medium having a pleated shape has a pleated portion in which the angle of pleated valleys formed between adjacent pleats is larger than 6.6 ° and smaller than 8.8 °.

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