JP6347699B2 - Three-layer filter medium, filter element using the same, and method for manufacturing three-layer filter medium - Google Patents

Description

  The present invention relates to a three-layer filter material that can be used for an air filter, a mask, and the like, a filter element using the same, and a method for manufacturing the three-layer filter material.

  Conventionally, a filter medium has been used to collect dust in the air. Such a filter medium preferably has a low pressure loss and a high dust collection efficiency. However, in order to satisfy such a requirement, a charged filter medium is used. As such a charged filter medium, a filter medium is known in which two or more kinds of fibers having different constituent resins are rubbed and charged by a difference in the charge train.

  For example, the applicant of the present application stated that “in a charged non-woven fabric composed of a plurality of clean fiber components, the fiber components being frictionally charged with each other, the plurality of fiber components were spun by a polyolefin fiber and an inorganic solvent. A charged non-woven fabric characterized by containing acrylic fiber "(Patent Document 1). Such a charged non-woven fabric has the above-mentioned physical properties, that is, a low pressure loss and a high dust collection efficiency. However, when a filter medium is used, a certain degree of rigidity may be required as in the case where the filter element is subjected to a folding process and the periphery thereof is fixed with an outer frame. The rigidity was insufficient and it was difficult to use as a filter medium.

In addition to Patent Document 1, the applicant of the present application is “a charged air filter in which a prefilter and a main filter are laminated and at least one of these filters is charged. A chargeable air filter characterized in that it is a frictionally charged non-woven fabric comprising a base fiber and a clean acrylic fiber spun by an inorganic solvent, and the main filter is a melt-blown non-woven fabric. "(Patent Document 2) ), "In the charging filter in which the prefilter layer, the main filter layer, and the backup filter layer are laminated, the prefilter layer has a mass per unit area of 40 to 120 g / m in which fibers having an average fineness of 1 to 6 dtex are entangled. consists of ^two of the charged nonwoven, the main filter layer has an average fiber diameter of 10μm Consists charged nonwoven fabric made of a fiber of the lower, the backup filter layer is made of charged nonwoven fabric mass 100 to 300 g / m ² per unit area fibers having an average fineness 1~6dtex is entangled, the unit of backup filter layer A charging filter characterized in that the mass per area is larger than the mass per unit area of the prefilter layer "(Patent Document 3).

  These charging filters disclose laminating a melt blown nonwoven fabric, another frictionally charged nonwoven fabric, etc. in addition to the frictionally charged nonwoven fabric as described above. Ultrasonic sealing, adhesive, fiber A method such as bonding is disclosed. However, when the layers are integrated by these methods, heat or moisture acts on the frictional charging filter as much as possible, so that there is a tendency for the charge amount to decrease and the collection efficiency to decrease. Further, in the process of transporting after manufacturing these charging filters, the frictional charging filter escapes through the transporting rollers even when coming into contact with the transporting rollers, and the collection efficiency tends to decrease.

  In addition, when the charging filter in Patent Documents 1 to 3 is used for an application requiring flame retardancy, such as when used as a vehicle interior filter for an automobile or the like, the flame retardancy is insufficient. It was something that could not be applied.

JP 2000-170068 A JP 2000-189732 A JP 2002-31010 A

  The present invention has been made under such circumstances, and has a three-layer filter material that has rigidity, is difficult to reduce the collection efficiency, and has flame retardancy, a filter element using the three-layer filter material, and a three-layer filter It aims at providing the manufacturing method of material.

  The invention according to claim 1 of the present invention is “a three-layer filter material having a frictionally charged nonwoven fabric layer in which two or more kinds of fibers having different constituent resins are mixed between bulky fiber sheet layers having a thickness of 0.5 mm or more, The triboelectrically charged nonwoven fabric layer-constituting fibers have entered the bulky fiber sheet layer, and each bulky fiber sheet layer contains fibers having a limiting oxygen index of 20 or more as constituent fibers, and the basis weight of the triboelectrically charged nonwoven fabric layer is 0. A three-layer filter medium having a basis weight of 5 times or more.

  The invention according to claim 2 of the present invention is “a filter element comprising the three-layer filter material according to claim 1 in a folded state”.

  The invention according to claim 3 of the present invention is “(1) a step of preparing a mixed fiber web in which two or more kinds of fibers having different constituent resins are mixed, (2) a fiber having a critical oxygen index of 20 or more, and having a thickness A step of preparing two bulky fiber sheets having a basis weight of 0.5 mm or more and 0.5 or more times the basis weight of the mixed fiber web; (3) sandwiching the mixed fiber web between the bulky fiber sheets; A step of forming a sheet, (4) a step of forming an integrated three-layer sheet having the mixed fiber web constituting fibers enter the bulky fiber sheet and having a mixed nonwoven fabric layer between the bulky fiber sheet layers, and (5) the integration. A step of forming a washed three-layer sheet from which the oil agent has been removed by washing the three-layer sheet, and (6) deforming the washed three-layer sheet in the thickness direction, charging the mixed nonwoven fabric layer by friction, and a bulky fiber sheet layer A step of forming a three-layer filtration media having a frictional charging nonwoven layer, and having a city, a manufacturing method of a three-layer filtration medium. "Is.

  The three-layer filter medium according to claim 1 of the present invention is a three-layer filter medium having rigidity because it includes two bulky fiber sheet layers having a thickness of 0.5 mm or more in addition to the frictionally charged nonwoven fabric layer.

  In addition, the bulky fiber sheet layer is bulky and easily deformed when the three-layer filter medium is transported, when the three-layer filter medium is processed, or when the three-layer filter medium is used. Since the bulky fiber sheet layer is deformed, the fibers constituting the frictionally charged non-woven fabric layer are easily charged by friction, so that the amount of charge is difficult to decrease and the collection efficiency is not easily lowered. It is.

  Further, both of the bulky fiber sheet layers constituting both surface layers contain fibers having an oxygen limit index of 20 or more as constituent fibers, and have a basis weight of 0.5 times or more the basis weight of the frictionally charged nonwoven fabric layer. Therefore, it is a three-layer filter material that is also excellent in flame retardancy.

  The filter element according to claim 2 of the present invention is provided with the three-layer filter material folded in a folded state, and the three-layer filter material has rigidity, and the friction-charged nonwoven fabric layer-constituting fibers are charged by friction. It is a filter element that is less likely to reduce the charge amount and the collection efficiency because it is easy. In addition, the filter element is excellent in flame retardancy.

  In the method for producing a three-layer filter material according to claim 3 of the present invention, after forming an integrated three-layer sheet, the oil agent is removed to make it easy to frictionally charge, and then deformed in the thickness direction and charged by friction. It can be manufactured without being affected by heat and moisture during integration, and can be charged by being deformed in the thickness direction when transporting the cleaning three-layer sheet. Thus, it is possible to produce a three-layer filter medium in which the charge amount is difficult to decrease and the collection efficiency is difficult to decrease.

  Moreover, since the two bulky fiber sheets are used, a rigid three-layer filter material can be manufactured.

  Furthermore, since it is a bulky fiber sheet containing fibers having a limiting oxygen index of 20 or more and having a basis weight of 0.5 times or more the basis weight of the mixed fiber web, it is laminated so as to form both surface layers. A three-layer filter medium having excellent properties can be produced.

Schematic cross-sectional view of an apparatus that can deform the cleaning three-layer sheet in the thickness direction Schematic cross-sectional view of another device capable of deforming the cleaning three-layer sheet in the thickness direction Schematic cross-sectional view of still another apparatus capable of deforming the cleaning three-layer sheet in the thickness direction Schematic cross-sectional view of still another apparatus capable of deforming the cleaning three-layer sheet in the thickness direction Schematic cross-sectional view of still another apparatus capable of deforming the cleaning three-layer sheet in the thickness direction

  Since the three-layer filter material of the present invention has two layers of bulky fiber sheet layers having a thickness of 0.5 mm or more, it has rigidity, and when the three-layer filter material is transported, processed, or used, Since the bulky fiber sheet layer is deformed (particularly, deformed in the thickness direction), the frictionally charged non-woven fabric layers constituting the bulky fiber sheet layer are easily charged with each other by friction, so the charge amount is difficult to decrease, It is a three-layer filter material in which the collection efficiency does not easily decrease.

  As described above, the bulky fiber sheet layer has a thickness of 0.5 mm or more so as to be excellent in rigidity and deformability. Preferably, it is 0.7 mm or more, more preferably 0.8 mm or more, and further preferably 1 mm or more. On the other hand, when the thickness exceeds 100 mm, the form stability tends to be poor, and since it is too thick and inferior in versatility, it is preferably 100 mm or less, more preferably 50 mm or less, and 30 mm or less. Is more preferably 10 mm or less, and further preferably 5 mm or less. The “thickness” in the present invention means a thickness at a load of 0.098 kPa.

  Such a bulky fiber sheet layer is not particularly limited as long as it has a certain degree of rigidity and deformability, and includes, for example, bonding means such as fiber fusion, needle punch, hydroentanglement, and binder bond. One or two or more non-woven fabrics can be used. Among these, the fiber-fused nonwoven fabric or the binder-bonded nonwoven fabric is preferable because it is excellent in rigidity and deformability, and the fiber-fused nonwoven fabric is particularly preferable because the entire fiber surface can be involved in filtration.

  In the present invention, even if the below-mentioned frictionally charged nonwoven fabric layer is mainly composed of flammable fibers, the frictionally charged nonwoven fabric layer is sandwiched by two layers of bulky fiber sheet layers, so that Any bulky fiber sheet layer includes fibers having a limiting oxygen index of 20 or more as constituting fibers so that flame retardancy can be imparted. The greater the amount of fibers with a critical oxygen index of 20 or more, the better the flame retardancy. Therefore, the fibers with a critical oxygen index of 20 or more occupy 70 mass% or more in any bulky fiber sheet layer. It is preferable to occupy 80 mass% or more, more preferably 90 mass% or more, and most preferably 100 mass%. In addition, this limiting oxygen index means the value measured by JISK7201.

  More specifically, the fibers having a limiting oxygen index of 20 or more include, for example, polyester fibers, polyamide fibers, vinylon fibers, polyvinylidene chloride fibers, synthetic fibers such as polyvinyl chloride fibers, inorganic fibers such as glass fibers, wool, And animal fibers such as silk. Among these, a synthetic fiber is preferable because it can easily maintain and improve the charge amount of the triboelectrically charged non-woven fabric layer by rubbing with the below-described triboelectric fabric of the triboelectrically charged non-woven fabric layer. Among these synthetic fibers, polyester fibers are preferable because they are excellent in rigidity.

  Examples of fibers having a limiting oxygen index of less than 20 that can form a bulky fiber sheet layer include synthetic fibers such as acrylic fibers and polyolefin fibers, regenerated fibers such as rayon fibers, semi-synthetic fibers such as acetate fibers, cotton and hemp And plant fibers.

  As described above, the bulky fiber sheet layer is preferably made of a fiber-fused nonwoven fabric. However, in the case of using such a fiber-fused nonwoven fabric, it includes a fused fiber having a fusible resin on the fiber surface. The bonded fibers are preferably fused. Such a fused fiber is also preferably a fiber having a critical oxygen index of 20 or more. For example, a fused fiber having a polyester resin, a polyamide resin, a polyvinylidene chloride resin, or a polyvinyl chloride resin on the fiber surface. Is preferred. As described above, since the polyester fiber having excellent rigidity is preferable, the fused fiber is preferably a fused fiber having a polyester resin on the fiber surface.

  The fused fiber only needs to have the above-mentioned resin on the fiber surface, and may be composed of one type of resin. However, the fused fiber maintains the fiber form even when fused, and has high rigidity. In order to be a non-woven fabric, that is, a bulky fiber sheet layer, in addition to the resin on the fiber surface involved in fusion, it is a fusion fiber composed of two or more types of resins that do not participate in fusion. preferable. For example, when the fusion fiber is composed of two types of resins, a core-sheath fusion fiber in which a high melting point resin is coated with a low melting point resin, and a high melting point resin and a low melting point resin are bonded together. A side-by-side fused fiber can be mentioned. In particular, a core-sheath type fused fiber is suitable because it can be a bulky fiber sheet layer having excellent rigidity.

  As described above, a fusion fiber having a polyester-based resin on the fiber surface is suitable as the fusion fiber. Therefore, the resin combination is polyethylene terephthalate / copolyester, polyethylene terephthalate / polybutylene terephthalate, polyethylene terephthalate / polytrile. The combination of methylene terephthalates is preferable, and the combination of the resin is particularly preferably a core component / sheath component.

  Although the fineness of the fibers constituting the bulky fiber sheet layer is not particularly limited, the bulky fiber sheet layer contains fibers having a fineness of 15 dtex or more so that the three-layer filter medium has excellent rigidity. Preferably, it contains fibers with a fineness of 18 dtex or more, and more preferably contains fibers with a fineness of 20 dtex or more. On the other hand, if the fineness is too large, the mechanical collection efficiency tends to decrease, so that it is preferably 50 dtex or less. As the number of fibers having such a fineness of 15 dtex or more increases, the rigidity of the three-layer filter medium can be increased. Therefore, the bulky fiber sheet layer preferably includes 30 mass% or more, and 45 mass% or more is included. More preferably, it is more preferably contained in an amount of 65 mass% or more. On the other hand, from the viewpoint of improving mechanical collection efficiency, it is preferable to include fibers of less than 15 dtex, more preferably to include fibers of 12 dtex or less, and further to include fibers of 10 dtex or less. Preferably, it contains fibers of 8 dtex or less.

  The “fineness” in the present invention means a value obtained by the A method defined in JIS L 1015: 2010, 8.5.1 (positive fineness).

  The fiber length of the fibers constituting the bulky fiber sheet layer is not particularly limited, but is preferably 30 mm or more, and 40 mm or more so that the bulky fiber sheet layer is excellent in the rigidity of the three-layer filter medium. It is more preferable that it is 50 mm or more. On the other hand, if the fiber length is too long, it tends to be difficult to uniformly disperse the fibers, and as a result, the collection efficiency tends to deteriorate. Therefore, it is preferably 150 mm or less, and 110 mm or less. More preferably. The “fiber length” in the present invention means a value obtained by JIS L 1015: 2010, 8.4.1 [corrected staple diagram method (B method)].

Each of the bulky fiber sheet layers has a basis weight of 0.5 times or more that of the below-described frictionally charged non-woven fabric layer so that the basis weight of the bulky fiber sheet layer can impart flame retardancy to the three-layer filter medium. Since the basis weight of the bulky fiber sheet layer is high, that is, the greater the amount of fibers having a critical oxygen index of 20 or more, the flame retardancy is excellent. Therefore, the basis weight of any bulky fiber sheet layer is the basis weight of the frictionally charged nonwoven fabric layer. It is preferably 0.6 times or more, more preferably 0.7 times or more, still more preferably 0.8 times or more, still more preferably 0.9 times or more, and 1 time or more. More preferably. On the other hand, if the basis weight of the bulky fiber sheet layer is too high, it tends to be inferior in versatility, such as being too thick and difficult to fold, so that the basis weight of the frictionally charged nonwoven fabric layer is 4 times or less. Preferably, it is 3 times or less. The basis weight is a mass per 1 m ² , and is a value obtained by the method defined in JIS L 1085: 1998 6.2 “Mass per unit area”.

Further, the apparent density of the bulky fiber sheet layer is not particularly limited as long as the thickness is 0.5 mm or more, but any bulky fiber sheet layer is 0.02 to 0.00 mm so as to be easily deformed. is preferably from 10 g / ^{m 2,} more preferably from 0.04~0.08g / ^{m 2,} and even more preferably 0.05~0.07g / ^{m 2.} The “apparent density” in the present invention is a calculated value obtained by dividing the basis weight by the thickness.

  Although the three-layer filter material of the present invention has two bulky fiber sheet layers, these bulky fiber sheet layers may be exactly the same, and the resin composition, fineness, and fiber of the fiber having a critical oxygen index of 20 or more. It may be a bulky fiber sheet layer that is different from at least one point selected from: long; structure of bulky fiber sheet layer, fiber blending, basis weight, thickness, and apparent density.

  In addition to the bulky fiber sheet layer as described above, the three-layer filter material of the present invention has a frictionally charged nonwoven fabric layer in which two or more kinds of fibers having different constituent resins are mixed. Since it has entered the fiber sheet layer, it is a three-layer filter material in which the charge amount is unlikely to decrease and the collection efficiency is unlikely to decrease. That is, in the three-layer filter material of the present invention, the bulky fiber sheet layer is easily deformed at the time of conveyance, processing, or use, and when it is deformed, the frictionally charged nonwoven fabric layer constituent fibers that have entered are easily charged by friction. The three-layer filter medium is less likely to reduce the charge amount and lower the collection efficiency.

  The frictionally charged nonwoven fabric layer of the present invention is composed of a nonwoven fabric in which two or more kinds of fibers having different constituent resins are mixed and charged by friction. However, if the constituent fibers are different, the constituent fibers are frictionally charged. As is the case, it is preferable that fibers composed of resins separated from the charge train are mixed. For example, a combination of polyolefin fiber and acrylic fiber; a combination of fluorine fiber and polyamide fiber, wool, glass fiber, silk or rayon fiber; a combination of urethane fiber and polyamide fiber, wool, glass fiber, silk or rayon fiber; Combination of vinyl fiber and polyamide fiber, wool, glass fiber, silk or rayon fiber; Combination of polyolefin fiber and polyamide fiber, wool, glass fiber, silk or rayon fiber; Combination of acrylic fiber and polyamide fiber, wool, glass fiber, silk or Combination of rayon fiber; combination of vinylon fiber and polyamide fiber, wool, glass fiber, silk or rayon fiber; combination of polyester fiber and polyamide fiber, wool, glass fiber, silk or rayon fiber; combination of acetate fiber and polyamide fiber, wool, glass Fiber, silk or rayon fiber , And the like; combinations. Among these, a combination of polyolefin fiber and acrylic fiber is a preferable combination because of a large amount of charge.

  In addition, "the constituent resin is different" means that the resin constituting the fiber surface (excluding both ends) is different, and the resin constituting the inside of the fiber is the same as the constituent resin of the other fibers. However, if the resin constituting the fiber surface (excluding both ends) is different, it is regarded as a fiber having a different constituent resin.

  As described above, the triboelectrically charged non-woven fabric layer-constituting fiber is preferably a combination of polyolefin fiber and acrylic fiber. Examples of the polyolefin fiber-constituting resin include polypropylene resin, polyethylene resin, polystyrene resin, vinyl acetate copolymer resin, An ethylene-propylene copolymer, or a resin obtained by substituting a part of these resins with a cyano group or a halogen can be used, and the polyolefin fiber is a composite fiber composed of one or more of these constituent resins. be able to. For example, it may be a core-sheath type composite fiber, and the sheath component may be a polyolefin fiber composed of a polyolefin resin.

  In the case of a suitable polyolefin-based fiber, it preferably contains a phosphorus-based additive and a sulfur-based additive. This is because the initial collection efficiency is improved by containing the phosphorus-based additive and the sulfur-based additive. In addition to the phosphorus-based additive and the sulfur-based additive, other additives such as phenol-based and amine-based additives may be further included.

  The phosphorus-based additive is preferably contained in the polyolefin fiber in an amount of 0.01% by mass or more, more preferably 0.2% by mass or more, and further preferably 0.3% by mass or more. Preferably, it contains 0.6 mass% or more.

  Examples of the phosphorus additive include trisnonylphenyl phosphite, tris (2,4-di-t-butylphenyl) phosphite, distearyl pentaerythritol diphosphite, bis (2,4-di-t- Butylphenyl) pentaerythritol phosphite, bis (2,6, di-t-butyl-4-methylphenyl) pentaerythritol phosphite, 2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite , Tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylene-di-phosphonite, bis (2,4-bis (1,1-dimethylethyl) -6-methylphenyl) ethyl ester Phosphoric acid, tetrakis (2,4-di-t-butylphenyl) (1,1-biphenyl) -4,4′-diylbi Phosphonites, can be mentioned phosphorus-based antioxidant such as bis (bis (2,4-di -t- butyl-5-methylphenoxy) phosphino).

  Examples of sulfur-based additives include sulfur such as dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, pentaerythritol tetrakis, and the like. A system antioxidant or the like can be preferably used. This sulfur-based additive is preferably contained in the polyolefin fiber in an amount of 0.01 mass% or more, and more preferably 0.1 mass% or more.

  In addition, since there exists a tendency for spinnability to worsen when the total amount of a phosphorus additive and a sulfur type additive increases, the total amount of a phosphorus type additive and a sulfur type additive is 5 mass% or less of polyolefin fiber. Is preferably 2 mass% or less, and more preferably 1 mass% or less.

  On the other hand, as the acrylic fiber, any of a polyacrylonitrile type mainly containing acrylonitrile (85% or more) and a modacrylic type containing acrylonitrile of 35% or more and less than 85% can be used. There are two types of polyacrylonitrile fibers, one spun using an organic solvent and one spun using an inorganic solvent, and any polyacrylonitrile fiber may be used.

  In addition, since it can be a three-layer filter material having excellent rigidity when the fused fibers include fused fibers as the frictionally charged nonwoven fabric constituting fibers, and the fused fibers are fused, the fused fibers as the frictionally charged nonwoven fabric layered fibers. Is preferably included.

  The fused fiber that can constitute the frictionally charged nonwoven fabric layer can be a fused fiber similar to the fused fiber that can constitute the bulky fiber sheet layer. In other words, for example, a polyester-based resin, a polyamide-based resin, a polyvinylidene chloride-based resin, a polyvinyl chloride-based resin, and a fused fiber having a polyolefin-based resin on the fiber surface can be cited. The fused fiber is preferably used.

  Further, the fused fiber constituting the frictionally charged nonwoven fabric layer only needs to have the above-described resin on the fiber surface, and may be composed of one kind of resin. As shown, in addition to the resin on the fiber surface involved in fusion, it is preferably a fusion fiber composed of two or more types of resins that do not participate in fusion. For example, when it is composed of two types of resins, a core-sheath type fusion fiber in which a high melting point resin is coated with a low melting point resin, and a side-by-side fusion type in which a high melting point resin and a low melting point resin are bonded together Fiber. In particular, a core-sheath type fused fiber is preferable because it can be a frictionally charged nonwoven fabric layer having excellent rigidity.

  As described above, a fusion fiber having a polyester-based resin on the fiber surface is suitable as the fusion fiber. Therefore, the resin combination is polyethylene terephthalate / copolyester, polyethylene terephthalate / polybutylene terephthalate, polyethylene terephthalate / polytrile. The combination of methylene terephthalates is preferable, and the combination of the resin is particularly preferably a core component / sheath component.

  When either or both of the bulky fiber sheet layers contain fused fibers, the fused fibers that constitute the frictionally charged nonwoven fabric layer are the same as the fused fibers that constitute either or both of the bulky fiber sheet layers. May be different or different, but if one or both fused fibers are the same, the bulky fiber sheet layer and the frictionally charged non-woven fabric layer are firmly fused, and delamination is difficult Therefore, it is preferable.

  In addition, as described above, the triboelectric non-woven fabric layer of the present invention preferably contains polyolefin fibers and acrylic fibers, but when it contains fused fibers, in addition to the polyolefin fibers and acrylic fibers. A fused fiber may be included, or a fused fiber may be used instead of an acrylic fiber, and a fused fiber and a polyolefin-based fiber may be included.

  The fineness of the fibers constituting the frictionally charged nonwoven fabric layer is not particularly limited. However, if the surface area of the fibers is large, the fibers tend to rub against each other, the amount of charge increases, and the collection efficiency by charging can be improved. Therefore, it is preferably 10 dtex or less, more preferably 7 dtex or less, still more preferably 5 dtex or less, and even more preferably 3 dtex or less. On the other hand, since the pressure loss tends to increase when the fiber becomes too thin, it is preferably 0.1 dtex or more, more preferably 0.5 dtex or more, and further preferably 1 dtex or more. preferable.

  Further, the fiber length of the fibers constituting the frictionally charged non-woven fabric layer is not particularly limited, but is preferably 20 mm or more so that the fiber enters the bulky fiber sheet layer and is easily frictionally charged when the bulky fiber sheet layer is deformed. , 35 mm or more, more preferably 50 mm or more. On the other hand, if the fiber length is too long, it tends to be difficult to uniformly disperse the fibers, and as a result, the collection efficiency tends to deteriorate. Therefore, it is preferably 150 mm or less, and 110 mm or less. More preferably.

The frictionally charged nonwoven fabric layer of the present invention is a layer in which two or more kinds of fibers having different constituent resins are mixed. However, the ratio of the number of positively charged fibers to the number of negatively charged fibers is 1: 0.5 to 2 so that the fibers can be easily charged by friction between the fibers. Preferably, it is 1: 0.75 to 1.5, more preferably 1: 0.8 to 1.2. For example, a suitable polyolefin fiber (fineness: 2.2 dtex, fiber length: 51 mm, density: 0.9 g / cm ³ ) and acrylic fiber (fineness: 2.2 dtex, fiber length: 51 mm, density: 1. 14 g / cm ³ ), the polyolefin fiber and the acrylic fiber are preferably in a mass ratio of about 39:61 to 72:28, more preferably about 46:54 to 63:37. Preferably, it is more preferably about 51:49 to 62:38.

  Even if the frictionally charged nonwoven fabric layer contains fused fibers, the ratio between the number of positively charged fibers and the number of negatively charged fibers is such that the fibers are easily charged by friction between the fibers. It is preferable that the fused fibers are mixed so that the ratio is the same. In general, in order to increase the rigidity of the frictionally charged nonwoven fabric layer, it is preferable that the fused fibers occupy 15 mass% or more of the frictionally charged nonwoven fabric layer, and more preferably, the fused fibers occupy 20 mass% or more. . On the other hand, when the amount of fused fibers increases, the amount of fibers involved in frictional charging decreases, and there is a tendency that the fibers cannot be sufficiently charged. Therefore, the fused fibers are preferably 60 mass% or less of the frictionally charged nonwoven fabric layer, and 50 mass. % Or less is more preferable, and 40 mass% or less is still more preferable.

The basis weight of the frictionally charged non-woven fabric layer of the present invention is not particularly limited, but since it is preferable that there is a certain amount of fiber so that the amount of charge is large, it is preferably 20 g / m ² or more, and 30 g / m. ^It is more preferably ² or more, and further preferably 40 g / m ² or more. On the other hand, if the basis weight is too high, the pressure loss tends to increase. Therefore, it is preferably 200 g / m ² or less, more preferably 180 g / m ² or less, and 150 g / m ² or less. Is more preferable. In particular, the amount of fibers involved in frictional charging in the triboelectric nonwoven fabric layer is preferably 20 g / m ² or more, more preferably 30 g / m ² or more, and 35 g / m ² so that the charge amount is large. More preferably, it is more preferably 40 g / m ² or more, and further preferably 45 g / m ² or more. On the other hand, in the triboelectric nonwoven fabric layer, the amount of fibers involved in triboelectric charging is preferably 200 g / m ² or less, more preferably 180 g / m ² or less, and more preferably 150 g / m ² so that pressure loss is unlikely to increase. More preferably, it is m ² or less.

  Further, the thickness of the frictionally charged nonwoven fabric layer is not particularly limited, but not only the bulky fiber sheet layer but also the frictionally charged nonwoven fabric layer itself is deformed in the thickness direction so that the friction that has not entered the bulky fiber sheet layer. The charged non-woven fabric layer-constituting fibers are also rubbed and charged, so that the amount of charge tends to increase, preferably 0.3 mm or more, more preferably 0.5 mm or more, and 0.7 mm or more. Is more preferable, and more preferably 1 mm or more. On the other hand, it is preferable that it is 3 mm or less so that it may be a three-layer filter medium excellent in form stability and versatility.

Further, the apparent density of the frictionally charged non-woven fabric layer is not particularly limited, but a certain amount of fibers are present, and 0.02 to 0.0.0 so as to have flexibility to be charged by friction between the fibers. it is preferably from 20 g / ^{m 2,} and more preferably 0.05~0.10g / ^{m 2.}

  The fibers constituting such a frictionally charged non-woven fabric layer have entered the bulky fiber sheet layer, and since the frictional charging occurs when the bulky fiber sheet layer is deformed (particularly when deformed in the thickness direction), the amount of charge is unlikely to decrease. It is a three-layer filter material in which the collection efficiency does not easily decrease. That is, the bulky fiber sheet layer is deformed when the fibers constituting the frictionally charged nonwoven sheet layer do not enter the bulky fiber sheet layer, as in the case where the frictionally charged nonwoven fabric layer and the bulky fiber sheet layer are simply laminated. However, the fibers constituting the frictionally charged non-woven fabric layer are not easily charged by friction, whereas the fibers constituting the frictionally charged non-woven fabric layer have entered the bulky fiber sheet layer. Since the constituent fibers are oriented in the thickness direction of the three-layer filter material, the fibers constituting the frictionally charged nonwoven fabric layer are easily charged by friction when the bulky fiber sheet layer is deformed.

  In addition, when the fibers constituting the frictionally charged nonwoven fabric layer enter the bulky fiber sheet layer and the frictionally charged nonwoven fabric layer constituting fibers are entangled with the bulky fiber sheet layer constituting fibers, the frictionally charged nonwoven fabric layer and the bulky fiber sheet layer Is a preferred embodiment because it is difficult to peel off.

  In addition, the fibers constituting the frictionally charged nonwoven fabric layer need only enter one of the bulky fiber sheet layers, but may enter both bulky fiber sheet layers. Further, when the fibers constituting the frictionally charged nonwoven fabric layer enter the bulky fiber sheet layer and / or any one of the bulky fiber sheet constituent fibers enters the frictionally charged nonwoven fabric layer and the fibers are intertwined, Since peeling does not easily occur, this is a preferred embodiment.

Is not particularly limited basis weight of the three-layer filtration media of the present invention, is preferably from 40400 g / ^{m 2,} more preferably from 60~360g / ^{m 2,} in 80~300g / ^{m 2} more preferably there, more preferably in the range of 90~250g / ^{m 2,} and even more preferably 100 to 200 g / ^{m 2.}

  Further, the thickness of the three-layer filter medium is not particularly limited, but is preferably 1.1 to 203 mm, and is preferably 1.5 to 50 mm so that the three-layer filter medium is easily deformed in the thickness direction and the charge amount is likely to increase. Is more preferably 2 to 30 mm, further preferably 2.5 to 20 mm, further preferably 3 to 10 mm, and further preferably 3 to 5 mm.

  In addition, the three-layer filter medium of the present invention preferably has a certain degree of rigidity because it has a wide filtration area and is preferably folded to form a filter element so that an increase in pressure loss can be suppressed. preferable. More specifically, the bending resistance measured by the Gurley method specified in 6.7.4 of JIS L 1913: 2010 is preferably 1 mN or more, more preferably 2.5 mN or more, and 4 mN or more. More preferably. The test piece is a rectangle with a size of 30 mm × 40 mm, and the side of 30 mm is fixed to the chuck for measurement.

  The filter element of the present invention comprises the three-layer filter material as described above in a folded state. For this reason, the filter element is rigid and has a triboelectrically charged nonwoven fabric layer that is easily charged by friction, so that the amount of charge is hardly reduced and the collection efficiency is hardly lowered. In addition, since the three-layer filter material of the present invention is rigid, it is a filter element that can be manufactured by performing a good folding process. Furthermore, since the above-mentioned three-layer filter material is also excellent in flame retardancy, it is a filter element excellent in flame retardancy.

  The filter element of the present invention can be exactly the same as the conventional filter element except that the three-layer filter material as described above is used.

  For example, crease folding is not limited as long as creases can be formed by folding into a zigzag shape, for example, by a pleating machine such as a reciprocating type or a rotary type, or a method of pressing with a stamping die formed in a zigzag shape Can do.

  The folded three-layer filter medium can be fixed by the outer frame, for example, by interposing a hot melt resin such as polyvinyl acetate between the outer frame and the three-layer filter medium. In addition, as an outer frame, the outer frame which consists of aluminum, aluminum alloy, stainless steel, various resin, paper, or a nonwoven fabric (for example, three-layer filter material of this invention) can be used, for example.

  The three-layer filter material of the present invention includes, for example, (1) a step of preparing a mixed fiber web in which two or more kinds of fibers having different constituent resins are mixed, and (2) a fiber having a critical oxygen index of 20 or more and having a thickness. A step of preparing two bulky fiber sheets having a basis weight of 0.5 mm or more and 0.5 or more times the basis weight of the mixed fiber web; (3) sandwiching the mixed fiber web between the bulky fiber sheets; A step of forming a sheet, (4) a step of forming an integrated three-layer sheet having the mixed fiber web constituting fibers enter the bulky fiber sheet and having a mixed nonwoven fabric layer between the bulky fiber sheet layers, and (5) the integration. A step of forming a washed three-layer sheet from which the oil agent has been removed by washing the three-layer sheet, and (6) deforming the washed three-layer sheet in the thickness direction, charging the mixed nonwoven fabric layer by friction, and a bulky fiber sheet Interlayer , It can be prepared to form a three-layered filtering material having a frictional charging nonwoven layer, by. Such a manufacturing method is a method in which, after forming an integrated three-layer sheet, the oil agent is removed to make it easy to frictionally charge, and then deformed in the thickness direction and charged by friction. It can be manufactured without being affected by heat and moisture when it is integrated with a charged non-woven fabric, and it can be charged by being deformed in the thickness direction during transport, etc., reducing the amount of charge. Therefore, it is possible to manufacture a three-layer filter medium that is difficult to be collected and whose collection efficiency is difficult to decrease. Moreover, since the two bulky fiber sheets are used, a rigid three-layer filter material can be manufactured. Furthermore, since the mixed fiber web is sandwiched between two bulky fiber sheets containing fibers having a critical oxygen index of 20 or more, a three-layer filter material having excellent flame retardancy can be produced.

  More specifically, first, (1) a step of preparing a mixed fiber web in which two or more types of fibers having different constituent resins are mixed is performed. Such a mixed fiber web can be formed, for example, by a dry method such as a card method or an air array method using the above-described fibers. The frictionally charged non-woven fabric layer constituting the three-layer filter material of the present invention can be composed of the fibers as described above, but contains polyolefin fibers and acrylic fibers so that it is easily charged by friction. Therefore, it is preferable that the mixed fiber web contains polyolefin fibers and acrylic fibers. In addition, when the frictionally charged non-woven fabric layer contains fused fibers (hereinafter, sometimes referred to as “fused fibers for the charged layer”), the polyolefin fibers or acrylic fibers may be used instead of the polyolefin fibers or acrylic fibers. In addition to the fibers, it is preferable to include fused fibers for the charging layer.

  And (2) a step of preparing two bulky fiber sheets containing fibers having a critical oxygen index of 20 or more, a thickness of 0.5 mm or more, and a basis weight of 0.5 times or more the basis weight of the mixed fiber web. carry out. Such a bulky fiber sheet can be formed, for example, by a dry method such as a card method or an air lay method using fibers having a limiting oxygen index of 20 or more as described above. In addition, since the bulky fiber sheet layer constituting the three-layer filter material of the present invention is preferably made of a fiber fusion nonwoven fabric, the bulky fiber sheet is a fiber web containing fusion fibers (hereinafter referred to as “bulk fiber web”). It is preferable that it is expressed.

  Two bulky fiber sheets are formed, but these bulky fiber sheets may be exactly the same, and the resin composition, fineness, and fiber length of fibers having a critical oxygen index of 20 or more; It may be a bulky fiber sheet selected from among a forming method, fiber blending, basis weight, thickness, and apparent density;

  Next, (3) a step of forming a three-layer sheet by sandwiching the mixed fiber web between the bulky fiber sheets is performed. Thus, by sandwiching the mixed fiber web between the bulky fiber sheets, it is possible to produce a three-layer filter medium having excellent rigidity and flame retardancy.

  Next, (4) the mixed fiber web constituting fiber is allowed to enter the bulky fiber sheet, and a step of forming an integrated three-layer sheet having a mixed nonwoven fabric layer between the bulky fiber sheet layers is performed. The method for causing the mixed fiber web constituent fibers to enter the bulky fiber sheet is not particularly limited, and examples thereof include a method of causing a needle or a water stream to act. Among these, the method of causing the needle to act is preferable because the mixed fiber web constituent fibers can be surely oriented in the thickness direction that is easily triboelectrically charged and the bulky fiber sheet is less likely to be damaged. is there.

  In addition, by making a needle or a water flow act, one bulky fiber sheet constituent fiber enters the mixed fiber web and entangles, and the mixed fiber web constituent fiber enters and entangles the other bulky fiber sheet. Also, there is a feature that it is easy to produce a three-layer filter material that is difficult to delaminate.

  In addition, when the needle or water flow is applied not only from the one bulky fiber sheet side but also from the other bulky fiber sheet side, the mixed fiber web constituent fibers enter both bulky fiber sheets and become entangled. Therefore, frictional charging is easily caused by deformation of both bulky fiber sheet layers, and delamination is less likely to occur.

The preferable needle conditions are not particularly limited, but the needle density is 30 needles / cm ² or more so that the mixed fiber web constituent fibers enter one of the bulky fiber sheets and are oriented in the thickness direction. It is preferable to operate at 40 lines / cm ² or more. On the other hand, if the needle density is too high, the rigidity tends to decrease. Therefore, it is preferable to act at 100 needles / cm ² or less.

  In addition, since the mixed fiber web itself is often entangled by the action of a needle, water flow, etc., the fibers are often bonded together, so the layer derived from the mixed fiber web in the integrated three-layer sheet after integration is mixed nonwoven fabric Expressed as a layer.

  Subsequently, (5) a step of cleaning the integrated three-layer sheet and forming a cleaned three-layer sheet from which the oil agent has been removed is performed. By carrying out this step, the triboelectric sheet can be triboelectrically charged efficiently by deformation in the thickness direction of the cleaning three-layer sheet described later. In this way, since the oil agent is removed after forming the integrated three-layer sheet, the mixed fiber web can be formed using the fibers to which the oil agent is adhered. Compared to the case of forming, it has excellent fiber opening performance, contributes to production stability, and eliminates the need to install a static eliminator, etc. on the opening machine Play.

  The method for cleaning the integrated three-layer sheet is not particularly limited. For example, by cleaning the integrated three-layer sheet with an alkaline aqueous solution, alcohol, water (including hot water or hot water), or a mixed solution thereof. The oil agent can be removed to form a washed three-layer sheet. In addition, you may wash | clean twice or more using these solutions. In that case, the same solution may be sufficient and a different solution may be sufficient.

  And (6) The cleaning three-layer sheet is deformed in the thickness direction, the mixed nonwoven fabric layer is charged by friction, and a three-layer filter material having a frictionally charged nonwoven fabric layer is formed between the bulky fiber sheet layers. The three-layer filter material of the present invention can be produced. That is, the washed three-layer sheet has a bulky fiber sheet layer into which mixed nonwoven fabric layer-constituting fibers have entered, and since this bulky fiber sheet layer is bulky, it is easily deformed in the thickness direction. Is deformed in the thickness direction, the bulky fiber sheet layer is deformed. In this bulky fiber sheet layer, two or more kinds of fibers having different constituent resins constituting the mixed nonwoven fabric layer have entered, and the bulky fiber sheet When the layer is deformed, the mixed nonwoven fabric constituent fibers that have entered are frictionally charged, and a three-layer filter medium having a frictionally charged nonwoven fabric layer between the bulky fiber sheet layers can be produced. In addition, when the mixed nonwoven fabric layer constituting fiber has entered both bulky fiber sheets, any mixed nonwoven fabric constituting fiber that has entered the bulky fiber sheet is charged by friction.

  The method of deforming the washed three-layer sheet in the thickness direction is not particularly limited as long as the mixed nonwoven fabric layer-constituting fibers are triboelectrically charged. For example, a method of passing a gap narrower than the thickness of the washed three-layer sheet And a method of rapidly changing the conveying direction of the washed three-layer sheet.

More specifically, as a method of passing a gap narrower than the thickness of the cleaning three-layer sheet, as shown in a schematic cross-sectional view in FIG. 1, so as to have a gap narrower than the thickness of the cleaning three-layer sheet S, Alternatively, a method of passing between a pair of rollers R ₁ and R ₂ arranged so that there is no gap (gauge: 0), as shown in a schematic cross-sectional view in FIG. A method of passing between a pair of plates P ₁ and P ₂ arranged so as to have a narrow gap or no gap, and the thickness of the cleaning three-layer sheet S as shown in a schematic sectional view in FIG. A method of passing between the plate P ₁ and the roller R ₂ arranged so as to have a narrower gap or no gap, as shown in a schematic sectional view in FIG. It has a narrower gap than the thickness of S To, or the gap are arranged so as not, between the rollers R _1, R _2, and the roller R _2, a method of passing between R _3, and the like. Among these, the method using only the roller as shown in FIGS. 1 and 4 is preferable because the cleaning three-layer sheet is hardly damaged.

The gap formed by these rollers R _{1 to} R _{2 and the} like is not particularly limited as long as it is narrower than the thickness of the cleaning three-layer sheet, but is preferably 0.1 mm or less.

The surface of the roller R ₁ to R _3, the surface of the plate P ₁ to P _2, as can be deformed in the thickness direction across bulky fiber sheet layer in washed three layer sheet, with no irregularities smooth surface Preferably there is.

In addition, when a roller having a large number of needles on the surface is used as the rollers R _{1 to} R ₃ , the bulky fiber sheet layer can be deformed in the thickness direction, and the needles enter the mixed nonwoven fabric layer to be mixed. It is preferable because the triboelectrically charged non-woven fabric layer having a large charge amount can be easily formed by efficiently moving the non-woven fabric layer-constituting fibers and rubbing the fibers.

  Furthermore, it is not necessary to use a single set of devices capable of deforming such a cleaning three-layer sheet in the thickness direction. In order to further increase the amount of charge, two or more sets are used for friction charging. Is preferred. In addition, when it has two or more sets of friction charging apparatuses, it is not necessary to be the same apparatus. In addition, when two or more sets of friction charging devices are provided, it is preferable that the friction charging device located on the downstream side in the transport direction is a device having a narrow gap because the amount of friction charging can be increased.

Furthermore, if the rollers R _{1 to} R ₃ and / or the plates P _{1 to} P ₂ are made of an insulator having a volume resistivity of 10 ¹² or more, the rollers R _{1 to} R ₃ and / or the plates P _{1 to} P ₂ and the mixed nonwoven fabric layer constituting fibers that have entered the bulky fiber sheet layer are charged by friction, so that the rollers R _{1 to} R ₃ and / or the plates P _{1 to} P ₂ are made of an insulator as described above. It is preferable.

On the other hand, the conveying direction of the washed three-layer sheet as a method for abruptly changed, as shown in a schematic cross-sectional view in FIG. 5, along the roller R _1, the conveying direction of the washed three-layer sheet by 90 ° changes a method of deforming in the thickness direction of the washed three-layer sheet, not shown, using a plate instead of the roller R ₁ in FIG. 5, along the plate, a conveying direction of the washed three-layer sheet 90 ° change By making it, the method of making it deform | transform in the thickness direction of a washing | cleaning three-layer sheet | seat can be mentioned.

  In FIG. 5, the frictional charging is performed by changing the conveyance direction of the cleaning three-layer sheet by 90 °. However, as long as the frictional charging is performed, it is not necessary to change by 90 °, but by changing the conveyance direction. This is a change that can be triboelectrically charged by deforming the cleaning three-layer sheet to a thickness of 50% or less of the apparent thickness (thickness under no load) of the cleaning three-layer sheet before the change in the conveying direction. Is preferred.

  Thus, the surface of the roller or the like that acts as a fulcrum for changing the conveying direction is a smooth surface without unevenness so that the entire bulky fiber sheet layer in the cleaning three-layer sheet can be deformed in the thickness direction. preferable. In addition, when a roller having a large number of needles on the surface is used as a roller that acts as a fulcrum, the bulky fiber sheet layer can be deformed in the thickness direction, and the needles enter the mixed nonwoven fabric layer and mix. It is preferable because the triboelectrically charged non-woven fabric layer having a large charge amount can be easily formed by efficiently moving the non-woven fabric layer-constituting fibers and rubbing the fibers.

  In addition, it is not necessary to have a single set of devices that can change the cleaning three-layer sheet in the thickness direction by rapidly changing the transport direction. To increase the amount of charge, two or more sets are used. It is preferable to perform frictional charging. In addition, when two or more sets of frictional charging devices are included, it is not necessary for both sets to be devices that rapidly change the conveyance direction, as described above, and a device that passes a gap narrower than the thickness of the cleaning three-layer sheet, It can also be used together. In addition, in the case of having two or more sets of devices that rapidly change the conveyance direction, if the amount of deformation in the thickness direction of the friction charging device located on the downstream side of the conveyance direction is increased, the amount of frictional charging can be increased. This is preferable because it is possible.

Further, when a roller or the like that acts as a fulcrum for changing the conveyance direction is formed of an insulator having a volume resistivity of 10 ¹² or more, the roller and the mixed nonwoven fabric layer constituting fibers that have entered the bulky fiber sheet layer Since charging is also caused by friction, the roller or the like acting as a fulcrum is preferably made of an insulator as described above.

  The above is the basic method for producing the three-layer filter material of the present invention. As described above, since the bulky fiber sheet layer is preferably composed of a fiber-fused nonwoven fabric layer, it is fused as at least one bulky fiber sheet. After forming an integrated three-layer sheet using a fiber web (hereinafter referred to as a “bulk fiber for fusion”) and forming an integrated three-layer sheet, the mixed nonwoven fabric layer is charged by friction. Before forming the frictionally charged nonwoven fabric layer, it is preferable to fuse the bulky fusion fiber to form a bulky fiber sheet layer composed of the fiber-fused nonwoven fabric layer. In other words, if the fusion fiber for bulkiness is fused before forming the integrated three-layer sheet, the mixed fiber web constituent fiber and the bulky fiber sheet when the mixed fiber web constituent fiber enters the bulky fiber sheet. This is because the entanglement with the constituent fibers is weak and tends to be difficult to be charged when the washed three-layer sheet is deformed, and the mixed nonwoven fabric layer and the bulky fiber sheet layer tend to peel off. On the other hand, if the mixed nonwoven fabric layer is charged by friction to form a frictionally charged nonwoven fabric layer and then the bulky fusion fiber is fused, the amount of charge tends to decrease due to heat at the time of fusion. . In particular, it is preferable to fuse the bulky fusion fiber at the stage of the integrated three-layer sheet before washing, because when the integrated three-layer sheet is washed, it can withstand the load caused by washing and easily maintain the form. is there.

  A method for fusing the bulky fusion fibers to form a fiber-fused nonwoven fabric layer (bulky fiber sheet layer) is a method in which the bulky fusion fibers are fused and a fiber-fused nonwoven fabric layer having a thickness of 0.5 mm or more ( The bulking fiber sheet layer) may be formed, and the fusing condition is not particularly limited because the fusing condition varies depending on the bulky fusing fiber. This condition can be appropriately set experimentally in accordance with the bulky fusion fiber. The heating means can be implemented by, for example, a hot air dryer, an infrared lamp, a heating roll, etc., but if it is a heating means such as a hot air dryer or an infrared lamp that does not act by solid pressure, the fiber-fused nonwoven fabric layer This is preferable because it does not impair the bulkiness.

  In addition, when both bulky fiber sheets contain the fusion fiber for bulkiness, the resin involved in the fusion of the fusion fiber for bulkiness constituting one bulky fiber sheet, and the bulkiness constituting the other bulky fiber sheet It is preferable that the melting point difference with the resin involved in the fusion of the fusion fiber for use is within 10 ° C. because both of the bulky fusion fibers can be fused at the same time. More preferably, the resins involved in the fusion are the same.

  Furthermore, as described above, it is preferable that the friction-charged nonwoven fabric layer-constituting fiber includes a charging-layer fusion fiber and is fused to provide excellent rigidity. However, the mixed fiber web is preferably a charging-layer fusion fiber. If the mixed three-layer sheet is formed using the mixed fiber web containing the fused fibers for the charging layer, and before the mixed nonwoven fabric layer is charged by friction to form the frictionally charged nonwoven fabric layer, In addition, it is preferable to form a mixed nonwoven fabric layer by fusing the fused fibers for the charging layer. In other words, if the fused fiber for the charging layer is fused before forming the integrated three-layer sheet, the fused fiber for the charged layer is fused when the mixed fiber web constituting fiber is allowed to enter the bulky fiber sheet. This is because the effect of improving the rigidity by fusing the fused fiber for charging layer tends to be halved. On the other hand, if the mixed nonwoven fabric layer is charged by friction to form a frictionally charged nonwoven fabric layer and the fused fibers for the charge layer are fused, the amount of charge tends to be reduced by the heat at the time of fusion. In particular, if the fused fiber for the charging layer is fused at the stage of the integrated three-layer sheet before cleaning, it is preferable because it can withstand the load caused by cleaning and maintain the form when the integrated three-layer sheet is cleaned. It is.

  In addition, the method for fusing the fused fiber for the charging layer to form the mixed nonwoven fabric layer is sufficient if the fused fiber for the charged layer is fused, and the fusion condition varies depending on the fused fiber for the charged layer. Therefore, it is not particularly limited. This condition can be appropriately set experimentally according to the fused fiber for the charging layer. The heating means can be implemented by, for example, a hot air dryer, an infrared lamp, a heating roll, etc., but if the heating means is not heated by a solid, such as a hot air dryer or an infrared lamp, the bulk of the mixed nonwoven fabric layer is high. As a result, a bulky frictionally charged non-woven fabric layer can be formed, and charging due to deformation of the triboelectrically charged non-woven fabric layer is easy to use.

  As described above, whether the bulky fiber web includes the bulky fused fiber or the mixed fiber web includes the charging layer fused fiber, the integrated three-layer sheet. It is preferable to fuse the bulky fusion fiber and / or the charge layer fusion fiber after friction, and before charging the mixed nonwoven fabric layer by friction, so that the bulkiness constituting one bulky fiber web When two or more fusion fibers selected from the fusion fiber for bulk, the fusion fiber for bulk constituting the other bulky fiber web, and the fusion fiber for charging layer are included, they are fused simultaneously. However, it is preferable in the manufacturing process. Therefore, it is preferable that the melting point difference of the resin involved in the fusion of the two or more fusion fibers contained is within 10 ° C., and more preferably the same melting point so that the temperature can be easily set.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

(Core-sheath type fusion fiber A)
Core-sheath fused fiber A having polyethylene terephthalate as a core component and copolymer polyester (melting point: 110 ° C.) as a sheath component (fineness: 22 dtex, fiber length: 64 mm, critical oxygen index: 20, Unitika ester T-4080) Prepared.

(Core-sheath fused fiber B)
Core-sheath type fusion fiber B (polyfineness: 6.6 dtex, fiber length: 51 mm, critical oxygen index: 20, unitica ester T-) having polyethylene terephthalate as a core component and copolymer polyester (melting point: 110 ° C.) as a sheath component 4080) was prepared.

(Core-sheath fused fiber C)
Core-sheath fused fiber C having polyethylene terephthalate as a core component and copolymer polyester (melting point: 110 ° C.) as a sheath component (fineness: 17 dtex, fiber length: 51 mm, critical oxygen index: 20, manufactured by HUVIS, trade name) : LMF).

(Core-sheath type fusion fiber D)
Core-sheath fused fiber C having polyethylene terephthalate as a core component and copolymer polyester (melting point: 110 ° C.) as a sheath component (fineness: 6 dtex, fiber length: 51 mm, critical oxygen index: 20, manufactured by HUVIS, trade name) : LMF).

(Acrylic fiber)
As an acrylic fiber, a polyacrylonitrile acrylic fiber [Bonnel (registered trademark) H815, fineness: 2.2 dtex, fiber length: 51 mm, critical oxygen index: 18, manufactured by Mitsubishi Rayon, Ltd.] obtained by wet spinning a spinning solution dissolved in an organic solvent. Density: 1.15 g / cm ³ ] was prepared.

(Polypropylene fiber)
As a polypropylene fiber, Ubenito U PP-NM (fineness: 2.2 dtex, fiber length: 51 mm, critical oxygen index: 18, manufactured by Ube Nitto Kasei Co., Ltd., density: 0.89 g / cm ³ ) was prepared.

(Spunbond nonwoven fabric)
As the spunbond nonwoven fabric, Marix (registered trademark, manufactured by Unitika, basis weight: 20 g / m ² , thickness: 0.14 mm), which is a polyester spunbond nonwoven fabric, was prepared.

Example 1
(1) A mixture of 60 mass% acrylic fiber and 40 mass% polypropylene fiber (number of acrylic fibers: number of polypropylene fibers = 1.16: 1), opened by a card machine, and mixed fiber web (weight: 50 g / m ²⁾ ) Was formed.

(2) 65 mass% of core-sheath type fusion fiber A (fusing fiber for bulkiness) and 35 mass% of core-sheath type fusion fiber B (fusing fiber for bulkiness) are blended and opened by a card machine, resulting in high bulkiness. A fiber web A (weight: 50 g / m ² ) and a bulky fiber web B (weight: 50 g / m ² ) were formed.

  (3) The mixed fiber web was sandwiched between the bulky fiber webs A and B to form a three-layer sheet.

(4) From the side of the bulky fiber web B of the three-layer sheet, a portion of acrylic fiber and polypropylene fiber constituting the mixed fiber web is made bulky by causing the needle to act at a needle density of 40 / cm ^2. While entering into A, it was entangled to form an integrated three-layer sheet having a mixed nonwoven fabric layer between the bulky fiber web layers A and B. In addition, some of the constituent fibers of the bulky fiber web B entered the mixed nonwoven fabric layer and were intertwined.

  (4 ′) A core-sheath type fused fiber constituting the bulky fiber web layers A and B on both surfaces by passing hot air from above with a hot air dryer in which the integrated three-layer sheet is set at a temperature of 150 ° C. Fusion fusion integration having only a sheath component of A and B, followed by a mixed nonwoven fabric layer between fiber fusion nonwoven fabric layers (bulky fiber sheet layers A and B) through between hot rolls (gauge: 3 mm) A three-layer sheet (thickness: 3 mm) was formed.

  (5) The fusion-integrated three-layer sheet was washed with warm water at a temperature of 70 ° C. for 6 seconds and then naturally dried to form a washed three-layer sheet from which the oil was removed.

(6) While conveying the washed three-layer sheet, the mixed nonwoven fabric layer is charged by friction by passing between smooth rubber rolls with a gauge of 0 and deforming in the thickness direction, and a fiber-fused nonwoven fabric layer (bulky fiber) Between the sheet layers A and B), a three-layer filter material having a frictionally charged nonwoven fabric layer (weight per unit: 150 g / m ² , thickness: 3 mm, frictionally charged nonwoven fabric layer constituting fibers entered the bulky fiber sheet layer A) was formed. . The physical properties of this three-layer filter material were as shown in Table 1.

(Example 2)
Fiber webs (weight per unit: 50 g / m ² ) obtained by blending the core-sheath type fusion fiber C85 mass% and the core-sheath type fusion fiber D15 mass% and opening them with a card machine were used as the bulky fiber webs A and B. Except for this, in the same manner as in Example 1, a three-layer filter medium having a triboelectrically charged nonwoven fabric layer (fiber weight: 150 g / m ² , thickness: 3 mm) between the fiber fusion nonwoven fabric layers (bulky fiber sheet layers A and B). The triboelectrically charged non-woven fabric layer-constituting fibers entered the bulky fiber sheet layer A). The physical properties of this three-layer filter material were as shown in Table 1.

(Example 3)
A fiber web (weight per unit: 30 g / m ² ) obtained by blending the core-sheath type fusion fiber A65 mass% and the core-sheath type fusion fiber B35 mass% and opening it with a card machine was used as the bulky fiber webs A and B. Except that, in the same manner as in Example 1, a three-layer filter medium having a friction-charged nonwoven fabric layer between the fiber-fused nonwoven fabric layers (bulky fiber sheet layers A and B) (weight per unit: 110 g / m ² , thickness: 2) .4 mm, triboelectrically charged non-woven fabric layer constituting fibers formed a bulky fiber sheet layer A). The physical properties of this three-layer filter material were as shown in Table 1.

(Comparative Example 1)
(1) A mixture of 60 mass% acrylic fiber and 40 mass% polypropylene fiber (number of acrylic fibers: number of polypropylene fibers = 1.16: 1), opened by a card machine, and mixed fiber web (weight: 50 g / m ²⁾ ) Was formed.

(2) 65 mass% of core-sheath type fusion fiber A (fusing fiber for bulkiness) and 35 mass% of core-sheath type fusion fiber B (fusing fiber for bulkiness) are blended and opened by a card machine, resulting in high bulkiness. A fiber web A (weight per unit area: 100 g / m ² ) was formed.

  (3) The mixed fiber web and the bulky fiber web A were laminated to form a two-layer sheet.

(4) From the mixed fiber web side of the two-layer sheet toward the bulky fiber web A side, by operating the needle at a needle density of 40 needles / cm ² , the acrylic fiber and the polypropylene fiber constituting the mixed fiber web Part of the bulky fiber web A was made to enter and entangled to form an integrated bilayer sheet having the bulky fiber web layer A and the mixed nonwoven fabric layer.

  (4 ') The sheath of the core-sheath-type fused fibers A and B constituting the bulky fiber web layer A by passing hot air from above with a hot air dryer in which the integrated two-layer sheet is set at a temperature of 150 ° C. Only the components are fused, and subsequently, a fusion-integrated two-layer sheet (thickness: having a fiber-fused nonwoven fabric layer (bulky fiber sheet layer A) and a mixed nonwoven fabric layer through a hot roll (gauge: 3 mm). 3 mm).

  (5) The fusion-integrated two-layer sheet was washed with warm water at a temperature of 70 ° C. for 6 seconds and then naturally dried to form a washed two-layer sheet from which the oil was removed.

(6) While transporting the washed double-layer sheet, the mixed nonwoven fabric layer is charged by friction by passing between smooth rubber rolls with a gauge of 0 and deforming in the thickness direction, whereby a fiber-fused nonwoven fabric layer (bulky fiber) A two-layer filter medium (sheet weight: 150 g / m ² , thickness: 3 mm, the friction-charged nonwoven fabric layer constituting fibers entered the bulky fiber sheet layer A) having a sheet layer A) and a friction-charged nonwoven fabric layer was formed. The physical properties of this two-layer filter material were as shown in Table 1.

(Comparative Example 2)
A fiber web (weight per unit: 20 g / m ² ) obtained by blending the core-sheath type fusion fiber A65 mass% and the core-sheath type fusion fiber B35 mass% and opening it with a card machine was used as the bulky fiber webs A and B. Except for this, in the same manner as in Example 1, a three-layer filter medium having a friction-charged nonwoven fabric layer between the fiber-fused nonwoven fabric layers (bulky fiber sheet layers A and B) (weight per unit: 90 g / m ² , thickness: 2) .2 mm, the triboelectrically charged non-woven fabric layer constituting fibers formed a bulky fiber sheet layer A). The physical properties of this three-layer filter material were as shown in Table 1.

(Comparative Example 3)
In the same manner as in Example 1 except that the spunbond nonwoven fabric (weight per unit: 20 g / m ² , thickness: 0.14 mm) was used instead of the bulky fiber webs A and B, between the spunbond nonwoven fabrics, A three-layer filter material having a frictionally charged nonwoven fabric layer (weight per unit: 90 g / m ² , thickness: 1.28 mm, the frictionally charged nonwoven fabric layer constituting fibers entered one spunbond nonwoven fabric layer) was formed. The physical properties of this three-layer filter material were as shown in Table 1.

(Comparative Example 4)
Except that the acrylic fiber and polypropylene fiber constituting the mixed fiber web were not allowed to enter any of the bulky fiber webs A and B without causing the needle to act on the three-layer sheet, the same as in Example 1. A three-layer filter material (weight per unit area: 150 g / m ² , thickness: 3 mm) having a frictionally charged nonwoven fabric layer was formed between the fiber fusion nonwoven fabric layers (bulky fiber sheet layers A and B). The physical properties of this three-layer filter material were as shown in Table 1.

(Comparative Example 5)
Acrylic fiber nonwoven fabric layer (bulky bulk) in the same manner as in Example 1 except that a fiber web (weight per unit: 50 g / m ² ) obtained by opening 100% acrylic fiber with a card machine was used as the bulky fiber webs A and B. A three-layer filter medium having a frictionally charged nonwoven fabric layer (fiber weight: 150 g / m ² , thickness: 3 mm, fibers constituting the frictionally charged nonwoven fabric layer entered the acrylic fiber nonwoven fabric layer) was formed between the fiber sheet layers A and B). . The physical properties of this three-layer filter material were as shown in Table 1.

(Evaluation of three-layer filter media)
(1) Measurement of collection efficiency;
A flat three-layer filter medium is set in a holder having an effective frontage area of 0.04 m ^{2 so} that the bulky fiber sheet layer A side becomes the upstream side, and then air dust (atmospheric dust with a particle size of 0.3 to 0.5 μm). Number: U) is supplied to the upstream side of the three-layer filter medium, and the surface wind speed is 10 cm / sec. In the case where air was allowed to pass through, the atmospheric dust number (D) on the downstream side was measured with a particle counter (manufactured by RION: model KC-01C), and the value calculated from the following equation was taken as the collection efficiency. The results are shown in Table 1.
Collection efficiency (%) = [1- (D / U)] × 100

(2) Rigidity measurement;
The rigidity of each three-layer filter medium or two-layer filter medium was measured by the Gurley method specified in 6.7.4 of JIS L 1913: 2010. The test piece was a rectangle with a size of 30 mm × 40 mm, and the measurement was performed with the 30 mm side fixed to the chuck so that the bulky nonwoven fabric layer A was in contact with the pendulum B. The results are shown in Table 1.

(3) Evaluation of flame retardancy;
Flame retardancy was evaluated by the method specified in JACA N0.11A-2003 "Flammability test flame resistance test of filter medium for air purifier". That is, the case where the flame did not ignite or the flame was 35 mm or less even after flame ignited was evaluated as “◯”, and the case where the flame was flared and the combustion distance exceeded 35 mm was evaluated as “X”. In addition, the test piece was made into the rectangle of 150 mm x 50 mm, and it installed and measured so that a fire might hit the bulky fiber sheet layer A side. The results are shown in Table 1.

From the results in Table 1, the following was found.
(1) From comparison between Example 3 and Comparative Example 2, if the basis weight of the bulky fiber sheet layer is 0.5 times or more the basis weight of the frictionally charged nonwoven fabric layer, the flame retardancy is excellent.
(2) From the comparison between Example 1 and Comparative Example 1, when the bulky fiber sheet layer is present on both sides of the frictionally charged nonwoven fabric layer, the flame retardancy is excellent.
(3) From the comparison between Example 3 and Comparative Example 3, when the thickness of the bulky fiber sheet layer is 0.5 mm or more, the collection efficiency is excellent.
(4) From the comparison between Example 1 and Comparative Example 4, when the fibers constituting the frictionally charged nonwoven fabric layer enter the bulky fiber sheet layer, the collection efficiency is high.
(5) From the comparison between Example 1 and Comparative Example 5, when the fiber constituting the bulky fiber sheet layer contains a fiber having a critical oxygen index of 20 or more, the flame retardancy is excellent.

  The three-layer filter material of the present invention has rigidity and is difficult to lower the collection efficiency, and is excellent in flame retardancy, and therefore for a folded filter element that requires flame retardancy. It can be suitably used as a three-layer filter material. The filter element obtained by folding the three-layer filter material of the present invention can be suitably used, for example, as an air filter, particularly as an air filter for a vehicle interior.

R ₁ to R ₃ roller P ₁ to P ₂ plate S washed three layer sheet

Claims (3)

It is a three-layer filter medium having a frictionally charged nonwoven fabric layer in which two or more kinds of fibers having different constituent resins are mixed between bulky fiber sheet layers having a thickness of 0.5 mm or more, and the frictionally charged nonwoven fabric layer constituting fibers are bulky fiber sheet layers. The bulky fiber sheet layer includes fibers having a limiting oxygen index of 20 or more as constituent fibers, and has a basis weight of 0.5 times or more that of the frictionally charged nonwoven fabric layer. A three-layer filter medium. A filter element comprising the three-layer filter material according to claim 1 in a folded state. (1) a step of preparing a mixed fiber web in which two or more kinds of fibers having different constituent resins are mixed;
(2) a step of preparing two bulky fiber sheets including fibers having a critical oxygen index of 20 or more, a thickness of 0.5 mm or more, and a basis weight of 0.5 times or more the basis weight of the mixed fiber web;
(3) sandwiching the mixed fiber web between bulky fiber sheets to form a three-layer sheet;
(4) A step of causing the mixed fiber web constituent fibers to enter the bulky fiber sheet and forming an integrated three-layer sheet having a mixed nonwoven fabric layer between the bulky fiber sheet layers,
(5) washing the integrated three-layer sheet to form a washed three-layer sheet from which the oil agent has been removed; and (6) deforming the washed three-layer sheet in the thickness direction and forming the mixed nonwoven fabric layer by friction. Forming a three-layer filter medium having a triboelectrically charged nonwoven fabric layer between charged and bulky fiber sheet layers;
The manufacturing method of the three-layer filter material characterized by having.

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