JP2014184360A - Filter medium for pleat type air filter and pleat type air filter unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter medium for a pleat type air filter which does not cause the increase of structural pressure loss, which has a large dust feed amount and which is excellent in pleat processability even when a pleat type air filter unit has a high ridge height and to provide the pleat type air filter unit.SOLUTION: A filter medium for a pleat type air filter has a spun-bonded nonwoven fabric layer and an ultrafine fiber-mixed layer which are satisfied with such four conditions (1)-(4) that: (1) the spun-bonded nonwoven fabric layer has a unit weight of 10-90 g/m; (2) the ultrafine fiber-mixed layer is mixed with ultrafine fibers and hot melt fibers and the hot melt fibers are melted and bonded; (3) the filter medium for the pleat type air filter has unevenness; and (4) the filter medium for the pleat type air filter has a Gurley bending resistance of 18 mN or more. In a pleat type air filter unit, a pleat processing-applied filter medium for the pleat type air filter is fixed with a frame.

Description

  The present invention relates to a pleated air filter medium suitable for an air filter unit that can be used in air conditioning equipment for general buildings, factory air conditioning equipment, computer room, hospital air conditioning equipment, and the like, and a pleated air filter unit using the filter material.

  Conventionally, as a filter material for a pleated type air filter having a large amount of dust supply, suitable for an air filter unit used for air conditioning equipment in general buildings, factory air conditioning equipment, computer rooms, hospital air conditioning equipment, etc. For example, a filter medium in which a fiber web obtained by mixing ultrafine organic fibers having an average fiber diameter of less than 1 μm and heat-fusible fibers having an average fiber diameter of 5 to 100 μm formed by a melt blow method is bonded with heat-fusible fibers. Proposed (Patent Document 1). When this filter medium was subjected to pleating with a peak height of about 30 mm, the filter medium was deformed and could be used without increasing the structural pressure loss due to close contact between adjacent filter media. When the pleating process is performed at a high peak height such that the thickness of the filter medium is 50 mm or more, the filter medium is deformed, and the adjacent filter mediums are brought into close contact with each other and the structural pressure loss is increased.

JP-A-11-104417

In order to prevent such an increase in structural pressure loss, rigidity is imparted by bonding a spunbonded nonwoven fabric to the filter medium. Such spunbonded nonwoven fabrics are generally bonded to the downstream side of the filter media so that the filtration performance of the filter media is not impaired. However, the increase in structural pressure loss due to the close contact between adjacent filter media is prevented. Therefore, when a spunbond nonwoven fabric with a basis weight exceeding 100 g / m ² or a spunbond nonwoven fabric whose rigidity is improved by a resin binder is bonded, the pressure loss of the spunbond nonwoven fabric itself is high, and pleatability However, there were problems such as extremely inferiority.

  The present invention is a pleated air filter unit having a high peak height such that the peak height is 50 mm or more, and does not increase structural pressure loss, has a large amount of dust supply, and has excellent pleat processability. And a pleat type air filter unit using the same.

The invention according to claim 1 of the present invention is “a filter medium for a pleated air filter having a spunbond nonwoven fabric layer and an ultrafine fiber mixed layer that satisfy the following conditions (1) to (4). (1) Spunbond. The basis weight of the nonwoven fabric layer is 10 to 90 g / m ² (2) The ultrafine fiber mixed layer is a mixture of ultrafine fibers having an average fiber diameter of 0.1 to 10 μm and heat-fusible fibers having an average fiber diameter of 10 to 100 μm (3) The filter medium for pleated type air filter has irregularities, and (4) the Gurley stiffness of the pleated type air filter medium is 18 mN or more. Is.

    The invention according to claim 2 of the present invention is "a pleated air filter unit in which the pleated air filter medium according to claim 1 is fixed by a frame".

The filter medium for a pleated type air filter according to claim 1 of the present invention is reinforced with a spunbonded nonwoven fabric layer, so that the Gurley bending resistance is 18 mN or more as a whole, and is excellent in rigidity. Moreover, even if it has unevenness and is deformed, it is possible to prevent the adjoining filter media from being in close contact with each other, so that an increase in structural pressure loss can be prevented. Moreover, since the ultrafine fiber mixed layer in which ultrafine fibers and heat-fusible fibers are mixed is a layer having a large amount of dust supply, it is a filter material for a pleated air filter having a large amount of dust supply. Furthermore, since the basis weight of the spunbonded nonwoven fabric is relatively low at 10 to 90 g / m ² , the pressure loss of the spunbonded nonwoven fabric itself is low and the pleatability is excellent.

  The pleated type air filter unit according to claim 2 of the present invention is a pleated type air filter unit in which the structural pressure loss does not increase and the amount of dust supplied is large because the filter medium is pleated. Furthermore, it can be manufactured with good workability.

Process drawing which shows an example of the manufacturing process of the filter material for pleated type | mold air filters of this invention Example of schematic cross section of spreader Partially enlarged perspective view of pleated filter material for air filter

  The filter medium for pleated air filter of the present invention (hereinafter sometimes simply referred to as “filter medium for air filter”) has an ultrafine fiber having an average fiber diameter of 0.1 to 10 μm and an average fiber so that the amount of dust supply is large. A heat-fusible fiber having a diameter of 10 to 100 μm is mixed, and includes an ultrafine fiber mixed layer in which the heat-fusible fiber is fused, and a spunbond layer that reinforces the ultrafine fiber mixed layer.

  The ultrafine fibers constituting the ultrafine fiber mixed layer have an average fiber diameter of 0.1 to 10 μm. If the average fiber diameter of the ultrafine fibers is less than 0.1 μm, the pressure loss tends to increase, so that it tends to be difficult to be a filter medium for air filter that can be used for a long time, while the average fiber diameter If it exceeds 10 μm, it tends to be difficult to collect fine dust, and it is more preferable to use ultrafine fibers having an average fiber diameter of 0.25 to 5 μm.

  The “average fiber diameter” in the present invention means an arithmetic average value of fiber diameters at 200 points of fibers (for example, ultrafine fibers). This fiber diameter is a value measured based on an electron micrograph of a filter medium for air filter.

  Although the resin component which comprises this ultrafine fiber is not specifically limited, For example, it is from one or more types, such as polyolefin resin, such as a polypropylene type and a polyethylene type, a polyester resin, a polyamide resin, a polycarbonate resin, and a urethane resin Can be. Among these, it is preferable to include a polyolefin-based resin on the surface of the ultrafine fiber, and more preferable to include a polypropylene-based resin on the surface of the ultrafine fiber, which makes it easy to produce ultrafine fibers and easily electretize.

  The ratio of such ultrafine fibers to the ultrafine fiber mixed layer is preferably 2 mass% or more and 40 mass% or less. If the ultrafine fiber is less than 2 mass%, the amount of the ultrafine fiber tends to be too small to collect fine dust. On the other hand, if it exceeds 40 mass%, it is clogged immediately by coarse dust. Therefore, it is more preferably 3 to 35 mass%, and still more preferably 4 to 30 mass%.

  Such an ultrafine fiber may be manufactured by any method. For example, a melt discharge method, an electrostatic spinning method, or a liquid discharge capable of discharging a spinning solution as disclosed in JP-A-2009-287138. And a gas discharge unit that is located upstream of the liquid discharge unit and can discharge gas. Among these, the melt blow method is suitable because it is easy to form ultrafine fibers made of an olefin resin that is easily electretized and has high productivity.

  The production conditions of the ultrafine fibers may be any conditions as long as the ultrafine fibers having an average fiber diameter of 0.1 to 10 μm can be spun and can be appropriately adjusted by experiment. For example, when producing ultrafine fibers by a suitable melt-blowing method, nozzle pieces arranged with an orifice diameter of 0.1 to 0.5 mm and a pitch of 0.2 to 1.2 mm are set to a temperature of 220 to 370 ° C. The resin is discharged at a rate of 0.0035 to 1.5 g / min per orifice, and a resin discharge amount of 5 to 5, 5 to 5 with respect to the discharged resin at a temperature of 220 to 400 ° C. and a mass ratio. Ultrafine fibers can be produced by acting 000 times as much air.

  In the ultrafine fiber mixed layer of the present invention, in addition to the ultrafine fibers as described above, heat-fusible fibers having an average fiber diameter of 10 to 100 μm are mixed, and the heat-fusible fibers are fused. Therefore, a relatively coarse space is formed, and this space can be maintained, so that coarse dust can be collected, pressure loss can be reduced, and the device can be used for a long time.

  The average fiber diameter of the heat-fusible fiber needs to be 10 to 100 μm. If the average fiber diameter is less than 10 μm, a relatively rough space is not formed, the pressure loss becomes high, and it is used for a long time. On the other hand, if the average fiber diameter exceeds 100 μm, the space formed by the heat-fusible fiber is too large, and even if ultrafine fibers are mixed, fine dust cannot be collected. Since there exists a tendency, it is more preferable that it is 15-70 micrometers, and it is still more preferable that it is 15-55 micrometers.

  This heat-fusible fiber is made of, for example, a one-type all-melt type, such as a polyolefin resin such as polypropylene or polyethylene, a polyester resin, a polyamide resin, a polycarbonate resin, or a urethane resin, or two of these resins. It can be a composite type containing more than one type. Among these, in the latter composite type, the fiber shape can be maintained by the resin component not fused, and the space formed by mixing the heat fusible fibers is excellent. Therefore, it is preferable.

  As this suitable composite-type heat-fusible fiber, for example, (1) a resin component having a high melting point is used as a core component, and a resin component having a lower melting point than this resin component having a high melting point is a sheath component (fusion component). (2) Side-by-side type in which a high melting point resin component and a resin component having a lower melting point than this high melting point resin component (fusion component) are bonded together ( 3) A sea-island type resin in which many low-melting point resin components are scattered in the low-melting point resin component (sea component and fusion component). Among these, a core-sheath type, an eccentric type, or a sea-island type composite heat-fusible fiber that is unlikely to become small due to heat at the time of heat-sealing and has excellent shape stability can be suitably used.

  In addition, the melting point difference between the high melting point component and the low melting point component (fusion component) of the composite heat-fusible fiber is 10 ° C. or higher so that none of the resin components are melted when fused. Preferably, it is 20 ° C. or higher. In addition, if the ultrafine fiber is also fused when fusing the composite heat-fusible fiber, it becomes impossible to collect fine dust. The component) is preferably 10 ° C. or more lower than the melting point of the ultrafine fibers (when the ultrafine fibers are composed of a plurality of resin components, the resin component having the lowest melting point is used), and more preferably 20 ° C. or more. For example, when the ultrafine fiber is made of a suitable polypropylene resin, the melting point of the fusion component of the composite heat-fusible fiber is preferably 150 ° C. or less, and more preferably 140 ° C. or less. In this case, the fusion component of the composite heat-fusible fiber is preferably made of a polyethylene resin.

  The heat-fusible fiber may be a long fiber or a short fiber, but is preferably a short fiber so that it can be easily mixed with the ultrafine fiber. In the case of short fibers, the fiber length is preferably 5 to 160 mm, and more preferably 25 to 110 mm so as to be easily mixed with ultrafine fibers.

  Also, if this heat-fusible fiber is drawn, the ultrafine fiber mixed layer is excellent in strength and rigidity, and it is easy to maintain a relatively coarse space formed by the heat-fusible fiber. Is preferred. The term “stretched” means that a fiber is mechanically stretched after spinning.

  The ultrafine fiber mixed layer of the present invention is in a state where such a heat-fusible fiber and the above-mentioned ultrafine fiber are mixed, and since the heat-fusible fiber is in a fused state, air is filtered. When doing so, the space between the fibers is difficult to deform. Therefore, dust can be collected and the pressure loss can be reduced, so that it can be used for a long time.

  The heat-fusible fiber and the ultrafine fiber may be mixed uniformly or non-uniformly, but the amount of the heat-fusible fiber on one side (A surface) in the ultrafine fiber mixed layer However, if the amount of the heat-fusible fiber on the B-side facing the A-side is larger, the heat-fusible fiber is thicker than the ultrafine fiber, so the A-side is relatively rough and the B-side is relatively dense. Since it is a simple structure, it is preferable because the A surface is positioned upstream of the filtration air, so that it is possible to sequentially filter from large particles and to be a filter medium for an air filter with a larger amount of dust supply. is there. Thus, it is preferable that the amount of the heat-fusible fiber gradually decreases from the A surface to the B surface so that large particles can be sequentially filtered. In addition, when the below-mentioned spunbond nonwoven fabric layer is laminated on the B surface side, in addition to the rigidity of the spunbond nonwoven fabric layer on the B surface side, the A surface side has a large amount of heat-fusible fibers, and the heat-fusible property. Since the rigidity is increased by the fusion of the fibers, the air filter medium is high in rigidity, and it is easy to suppress an increase in the structural pressure loss.

  Such heat-fusible fibers preferably occupy 60 mass% or more of the ultrafine fiber mixed layer so that a relatively rough space can be formed, and account for 98 mass% or less in relation to the ultrafine fibers. preferable. More preferably, it occupies 65 to 97 mass% of the ultrafine fiber mixed layer, and more preferably occupies 70 to 96 mass%.

  In addition, the heat-fusible fiber does not need to consist of one type, and two or more types of heat-fusible fibers that differ from each other in terms of fiber diameter, composition, fiber length, and the like may be mixed. Moreover, since the size of the space can be gradually changed by mixing two or more kinds of heat-fusible fibers having different fiber diameters, there is a difference of about 10 to 50 μm in terms of the average fiber diameter. It is preferable to mix two or more kinds of heat-fusible fibers.

  The ultrafine fiber mixed layer of the present invention is a mixture of ultrafine fibers and heat-fusible fibers, but may contain fibers other than these fibers, for example, nylon fibers, vinylon fibers, polyester fibers, acrylic fibers, Synthetic fibers such as polyethylene fibers, polypropylene fibers, and polyurethane fibers, and functional fibers may be mixed to impart various functions. Examples of the functional fibers include vinylidene fibers that can impart flame retardancy, polyvinyl chloride fibers, polyclar fibers, or modified acrylic fibers, fibers including silver and copper that can impart antibacterial properties, and the like. . In addition, functional fibers having functions such as antistatic properties, deodorizing properties, deodorizing properties, and hygroscopic properties may be mixed. In addition, the functional substance which has these functions may be mixed in the ultrafine fiber and / or the heat-fusible fiber. In addition, when polyolefin fiber and acrylic fiber and / or modified acrylic fiber are mixed, it can be charged by friction.

  In the ultrafine fiber mixed layer, fibers other than the ultrafine fibers and heat-fusible fibers (hereinafter referred to as “other fibers”) collect fine dust by the ultrafine fibers and a relatively coarse space by the heat-fusible fibers. It is preferable that it is 38 mass% or less of the ultrafine fiber mixed layer so as not to prevent the formation and maintenance of. The other fibers may be long fibers or short fibers, but are preferably short fibers so as to be easily mixed with ultrafine fibers and heat-fusible fibers. In the case of a short fiber, the fiber length is preferably 5 to 160 mm, and more preferably 20 to 110 mm.

  Furthermore, it is preferable that the other fibers have a melting point higher by 10 ° C. or more than the melting point of the fusion component of the heat-fusible fiber so as not to be melted by heat when fusing the heat-fusible fiber. It is more preferable to have a melting point higher by at least ° C.

  In the ultrafine fiber mixed layer, at least ultrafine fibers and heat-fusible fibers are mixed, and the heat-fusible fibers are fused. In addition, since an ultrafine fiber mixed layer can be comprised only from the above organic fibers, it is not damaged, such as tearing at the time of handling the filter medium for air filters, or carrying. Moreover, since it can be incinerated when the service life of the filter medium for an air filter comes, it is suitable for disposal.

The thickness of the ultrafine fiber mixed layer of the present invention is preferably 0.1 to 10 mm. When the thickness of the ultrafine fiber mixed layer is less than 0.1 mm, it is difficult to form a relatively rough space with the heat-fusible fiber, so the pressure loss is high, and there is a tendency that it cannot be used for a long time, and the thickness exceeds 10 mm. Then, the portion that does not participate in the filtration tends to increase. Therefore, the thickness is more preferably 0.2 to 5 mm, and further preferably 0.5 to 4 mm. The “thickness” in the present invention refers to a value at a load of 0.2 N per 1 cm ^{2 of} unit area.

The basis weight of the ultrafine fiber mixed layer is preferably 30 to 300 g / m ² . If the basis weight is less than 30 g / m ² , the density tends to be too low and it becomes difficult to collect fine dust, whereas if it exceeds 300 g / m ² , the density becomes too high, immediately clogging by coarse dust, because there is a long period of time tends to become unavailable, more preferably from 40~250g / ^{m 2,} and even more preferably 50 to 200 g / ^{m 2.}

Furthermore, the apparent density of the ultrafine fiber mixed layer is preferably 0.003 to ³ g / cm ³ . If the apparent density is less than 0.003 g / cm ³ , it tends to be difficult to collect fine dust, while if it exceeds ³ g / cm ³ , clogging is immediately caused by coarse dust. It is more preferable that it is 0.008 to 1.25 g / cm ³ because it tends to occur and cannot be used for a long time. This apparent density is a value obtained by dividing the basis weight (unit: g / cm ² ) by the thickness (unit: cm).

  The filter material for an air filter of the present invention includes a spunbond nonwoven fabric layer in addition to the ultrafine fiber mixed layer described above, and is reinforced by a rigid spunbond nonwoven fabric layer. Since the softness is 18 mN or more and is in a very excellent state, even if pleating is performed, in addition to the fact that adjacent filter media are difficult to adhere to each other, even if the filter media is deformed, the filter media for air filter Has irregularities, and the adjacent filter media do not adhere to each other, so that the structural pressure loss is hardly increased. In particular, even when the pleating process is performed at a high mountain height where the mountain height is 50 mm or more (particularly, 100 mm or more), the filter medium is difficult to deform, and even if it is deformed, it is adjacent due to the presence of irregularities. It is possible to suppress an increase in pressure loss due to close contact between the filter media.

  The filter medium for air filter of the present invention has a Gurley stiffness of 18 mN or more, but the higher the Gurley stiffness, the better the above-mentioned effect. Therefore, it is preferably 20 mN or more, preferably 25 mN or more. Is more preferably 30 mN or more, and further preferably 35 mN or more. On the other hand, if the Gurley bending resistance is too high, the unevenness and the pleatability tend to be deteriorated, so that it is preferably 70 mN or less, and more preferably 50 mN or less. The “Gurley stiffness” of the present invention refers to the value of JIS L 1913-2010 [6.7.4 (Gurley method)].

  In addition, since a spunbonded nonwoven fabric can be comprised only from organic substance, it is not damaged, such as a tear, at the time of handling of the filter material for air filters, or conveyance. Moreover, since it can be incinerated when the service life of the filter medium for an air filter comes, it is suitable for disposal.

  The spunbonded nonwoven fabric of the present invention may be composed of any resin as long as it has the Gurley stiffness as described above as a result of being laminated with the ultrafine fiber mixed layer, for example, polypropylene or polyethylene Examples thereof include resins such as polyolefin resins, polyester resins, polyamide resins, polycarbonate resins, and urethane resins. Among these, since polyester-type resin has high rigidity, it is preferable that polyester-type resin is included.

  The spunbonded nonwoven fabric may be composed of one kind of these resins, but is preferably a composite type containing two or more kinds of these resins. This is because by using the composite type, fibers can be fused together, and the fiber shape can be maintained by a resin that does not participate in the fusion, and as a result, the rigidity of the spunbonded nonwoven fabric is excellent. In the case of the composite type, the resin may be arranged in any manner in the fiber cross section, but can be, for example, a core-sheath type, an eccentric type, a side-by-side type, or a sea-island type. When the fiber is composed of a high melting point component and a low melting point component (fusion component), the melting point is 10 ° C. or higher so that both resin components are not melted when fused. There is preferably a difference, more preferably a melting point difference of 20 ° C. or more. In addition, when a spunbond nonwoven fabric composed of composite type fibers is also involved in fusing with the ultrafine fiber mixed layer, when fusing the spunbond nonwoven fabric constituent fibers, the ultrafine fibers in the ultrafine fiber mixed layer are also fused. Then, since there is a tendency that fine dust cannot be collected, the low melting point component (fusion component) of the spunbond nonwoven fabric is the melting point of the ultrafine fiber (when the ultrafine fiber is composed of a plurality of resin components, It is preferably 10 ° C. or more lower than the resin component having the lowest melting point, more preferably 20 ° C. or more. For example, when the ultrafine fiber is made of a suitable polypropylene resin, the low melting point component (fusion component) of the spunbond nonwoven fabric constituting fiber preferably has a melting point of 150 ° C. or lower, and more preferably 140 ° C. or lower. An example of such a resin component is a polyethylene resin. Therefore, it is preferable that the fibers constituting the spunbonded nonwoven fabric include polyethylene as a fusion component and a polyester resin as a non-fusion component.

  The average fiber diameter of the spunbonded nonwoven fabric is not particularly limited, but is preferably 10 to 100 μm, and more preferably 20 to 50 μm. When the average fiber diameter is less than 10 μm, the pressure loss of the filter medium for air filter increases, and there is a tendency that it cannot be used for a long time. On the other hand, when the average fiber diameter exceeds 100 μm, the rigidity becomes too high, and unevenness and pleats This is because the workability tends to be inferior. Moreover, the spunbond nonwoven fabric constituent fiber does not need to consist of one type, and may be composed of two or more types of fibers that differ in terms of fiber diameter, composition, and the like.

  The spunbond nonwoven fabric layer preferably has a thickness of 0.1 to 2 mm. When the thickness is less than 0.1 mm, the reinforcing effect of the spunbond nonwoven fabric layer is weakened, and when a pleated air filter is used, the pressure loss tends to increase. When the thickness exceeds 2 mm, the rigidity becomes too high. The thickness is more preferably 0.15 to 1.5 mm, and still more preferably 0.2 to 1 mm because unevenness and pleating tend to be difficult.

Also, the basis weight of the spunbonded nonwoven fabric layer is 10~90g / ^{m 2.} When the basis weight is less than 10 g / m ² , the reinforcing effect by the spunbond nonwoven fabric layer is weakened, and it becomes difficult to make the Gurley stiffness of the pleated type air filter 18 mN or more. As a result, the structural pressure loss tends to increase. On the other hand, if it exceeds 90 g / m ² , the thickness will increase accordingly, the rigidity will be too high, and unevenness and pleating will tend to be difficult, and the pressure loss of the air filter medium will increase. , subjected to pleating, in order to pressure Sonka even unitized, it is preferably from 20 to 80 g / ^{m 2,} and more preferably 30~70g / ^{m 2.}

In addition, it is preferable that the spunbonded nonwoven fabric is partially fused so as to be excellent in rigidity. When such are partially fused, so as not to become higher pressure loss of spunbonded nonwoven is preferably an area per one fused portion is 0.1 cm ² or less, 0.05 cm ² or less It is more preferable that Further, the total area ratio of the fused portion is preferably 70% or less, and more preferably 50% or less. In addition, although the shape of a melt | fusion part is not specifically limited, For example, circular, polygonal shape (for example, a rhombus, a square, a rectangle, a hexagon, a parallelogram) etc. can be mentioned. Further, the fused portion may be a straight line or a curved line, and may be in a mesh state in which these are combined.

  In addition, in order to increase the rigidity of the spunbonded nonwoven fabric, it is conceivable to bond the spunbonded nonwoven fabric with a resin binder, but when bonded with a resin binder, a film resulting from the resin binder is formed and the pressure loss tends to increase. Therefore, it is preferable that the spunbonded nonwoven fabric is not bonded with a resin binder.

  Such a spunbond nonwoven fabric may be present on either side of the ultrafine fiber mixed layer, but does not impair the filtration performance of the ultrafine fiber mixed layer and can be a filter medium for air filters with a large amount of dust supply. Thus, it is preferable that it is located so that it exists in the downstream of filtration air rather than a microfiber mixed layer. In addition, as described above, when the ultrafine fiber mixed layer has an A surface with a large amount of heat-fusible fibers and a B surface with a small amount, the spunbond nonwoven fabric layer is present on the B surface side, and the spunbond nonwoven fabric layer side is It is preferable to be on the downstream side of the filtration air. It is because it can filter in order from a big dust.

  The spunbond nonwoven fabric layer and the ultrafine fiber mixed layer may or may not be bonded. When they are bonded, they may be bonded by the fusing property of the heat-fusible fiber of the spunbond nonwoven fabric constituting fiber and / or the ultrafine fiber mixed layer, or may be bonded by interposing a hot melt resin. Further, they may be bonded by a liquid binder or may be bonded by a needle punch. In addition, as described above, when the ultrafine fiber mixed layer has the A surface with a large amount of heat-fusible fibers and the B surface with a small amount, and the spunbond nonwoven fabric layer exists on the B surface side, the ultrafine fiber mixed layer It is preferable that the spunbond nonwoven fabric constituting fibers are bonded only to each other so that the ultrafine fibers are not melted and the filtration performance is not impaired.

  The filter medium for an air filter of the present invention has the spunbond nonwoven fabric layer and the ultrafine fiber mixed layer as described above. As described above, in addition to the Gurley bending resistance being 18 mN or more, there are irregularities. doing. Therefore, even if the filter medium for the air filter is deformed and is likely to be in close contact with the adjacent filter medium, it is possible to prevent the adjacent filter medium from adhering to each other by having the unevenness, so that the structural pressure loss is low. A pleated type air filter can be produced.

  In addition, this unevenness may be composed of a convex part of the resin application part and a concave part of the resin non-application part formed by a method such as applying a resin to the filter medium for the air filter, but the filtration area is reduced. It is preferable that the air filter medium itself, which is formed by an embossing roll or the like, has a concave part and a convex part. In particular, the air filter medium has a convex part on one side and a convex part on the other side. It is preferable that the corresponding portion is a recess. This is because when the convex portion and the concave portion correspond to each other, the fiber density of the concave and convex portion and the portion other than the concave and convex portion is substantially the same, and the entire filter medium for the air filter can be effectively used.

  As an example of such a suitable filter medium for air filter itself having irregularities corresponding to the convex portion and the concave portion, for example, as disclosed in Japanese Patent Application Laid-Open No. 2011-206724, the filter medium faces each other. Convex / concaves having different areas between the convex parts on the surface, two or more convex parts with different heights separated from each other on the surface facing when pleating as described in Japanese Patent Application No. 2012-212109 Such irregularities can be mentioned.

  In addition, when the air filter medium itself has irregularities corresponding to the convex portions and the concave portions, the maximum depth or the maximum depth from the air filter medium surface of the concave portions or convex portions can be prevented so that the adjoining filter media can be prevented. The height is preferably 1 to 9 mm, and more preferably 2 to 8 mm.

  It is preferable that the thickness of the flat part which is neither a convex part nor a recessed part of the filter medium for air filters of this invention is 0.2-12 mm. When the thickness is less than 0.2 mm, there is a tendency that the space for holding dust is not sufficiently secured and cannot be used for a long time, and when the thickness exceeds 12 mm, there is a tendency that a portion not involved in filtration tends to increase. Moreover, since unevenness and pleating tend to be difficult, the thickness is more preferably 0.4 to 6.5 mm, and even more preferably 0.7 to 5 mm.

The basis weight of the air filter medium is preferably 40 to 390 g / m ² . If the basis weight is less than 40 g / m ² , the amount of fibers is small, and there is a tendency that a space for holding dust is not sufficiently secured and cannot be used for a long time. On the other hand, if the basis weight exceeds 390 g / m ² , the amount of fibers is large. too, occur immediately clogged with coarse dust, because there is a tendency that can not be used for a long period of time, more preferably from 60~330g / ^{m 2,} and further in the range of 80~270g / ^{m 2} preferable.

  Moreover, it is preferable that the filtration performance of the flat filter medium before the unevenness of the filter medium for air filter of the present invention functions as a medium-high performance filter. Specifically, the particle collection efficiency is 5 to 95%. It is preferable that it is 6 to 90%, more preferably 7 to 85%. When the particle collection efficiency is less than 5%, the particle collection is insufficient, and when the particle collection efficiency exceeds 95%, the pressure loss of the filter material for the air filter immediately reaches the limit and the life is shortened. This is because there is a tendency.

The “collection efficiency” is a value obtained by the following operation. In other words, after setting the flat filter medium before unevenness in a holder having an effective frontage area of 0.04 m ² , atmospheric dust (particle number: U) having a particle size of 0.3 to 0.5 μm is placed upstream of the filter medium. When the air was supplied and allowed to pass air at a surface wind speed of 0.1 m / sec, the atmospheric dust number (D) on the downstream side was measured with a particle counter (manufactured by RION: model KC-01C) and calculated from the following equation: The value is the collection efficiency.
Collection efficiency (%) = [1- (D / U)] × 100

  Further, the initial pressure loss of the flat filter medium before the unevenness of the air filter medium of the present invention is preferably 80 Pa or less, more preferably 70 Pa or less, further preferably 60 Pa or less, and further preferably 50 Pa or less. This “initial pressure loss” refers to the initial pressure loss during the collection efficiency measurement.

Furthermore, the dust supply amount of the flat filter medium before having the irregularities of the air filter medium of the present invention is preferably 10 g / m ² or more, more preferably 20 g / m ² or more so as to have a long life. Preferably, it is 30 g / m ² or more. This dust supply amount is set with a flat filter medium before unevenness in a holder having an effective frontage area of 0.05 m ² , JIS 15 type dust is supplied upstream of the filter medium, and air is blown at a surface wind speed of 0.1 m / sec. It refers to the amount of dust supplied from the initial stage until the pressure loss reaches 300 Pa.

  The filter medium for an air filter in which the ultrafine fibers of the present invention are made of melt blown fibers can be produced, for example, as follows. First, as shown in FIG. 1, the heat-fusible fiber 4 opened by the fiber spreader 3 with respect to the flow of the ultrafine fiber 2 discharged from the melt blow apparatus 1 under the above-described conditions (in some cases, other fibers) The mixed fibers are collected by a collecting body 5 such as a conveyor to form an ultrafine fiber mixed web 6. Next, the spunbond nonwoven fabric 7 is laminated. Next, the laminated sheet is heat-treated with a heat treatment apparatus 8 to form an ultrafine fiber mixed layer by fusing the heat-fusible fiber 4, and at the same time, the extra-fine fiber mixed layer and the span are formed by fusing the heat-fusible fiber 4. After bonding the bonded nonwoven fabric 7 to form the fused laminated web 9, embossing is performed by the embossing device 10 to form irregularities on the main surface to produce the air filter medium 11 of the present invention. Can do.

  In some cases, the fusion-bonded web 9 can be formed by fusing the ultrafine fiber mixed layer and the spunbond nonwoven fabric 7 by utilizing the fusing property of the fibers constituting the spunbond nonwoven fabric. In particular, the ultrafine fiber mixed layer has an A surface with a large amount of heat-fusible fiber and a small B surface, and when a spunbonded nonwoven fabric layer is laminated on the B surface side, there are many ultrafine fibers on the B surface side, Since there is a tendency to be inferior in the bonding strength with the spunbond nonwoven fabric layer, it is preferable to bond using the fusing property of the fibers constituting the spunbond nonwoven fabric.

  Examples of the spreader 3 that supplies the heat-fusible fiber 4 include a card machine and a garnet machine, but a spreader 3 that houses a plurality of spreader cylinders 31 as shown in FIG. The heat-fusible fiber 4 can collide with the flow of the ultra-fine fiber 2 vigorously, and the entire ultra-fine fiber mixed web 6 is mixed so that the ultra-fine fiber 2 and the heat-fusible fiber 4 are mixed. be able to. In particular, when the heat-fusible fiber 4 is supplied from the right-angled direction as much as possible with respect to the flow of the ultra-fine fiber 2, the ultra-fine fiber 2 and the heat-fusible fiber 4 are mixed in the entire ultra-fine fiber mixed web 6. can do. 2, an air nozzle that can supply air so that the heat-fusible fiber 4 can be vigorously supplied from a right angle direction with respect to the flow of the ultrafine fibers 2 flying in the direction of gravity. 33 is provided.

  In addition, the existence ratio of the heat-fusible fiber 4 in the thickness direction of the ultrafine fiber mixed web 6 can be changed by adjusting the angle at which the heat-fusible fiber 4 is supplied to the ultrafine fiber 2. That is, by making the angle (θ in FIG. 1) for supplying the heat-fusible fiber 4 to the ultrafine fiber 2 an acute angle, the advance input of the heat-fusible fiber 4 to the flow of the ultrafine fiber 2 is weakened. Therefore, the amount of the heat-fusible fiber 4 is large on the supply side of the heat-fusible fiber 4, and the amount of the ultrafine fiber 2 is gradually increased toward the side opposite to the supply side of the heat-fusible fiber 4. It is possible to obtain an ultrafine fiber mixed web 6 having a large density and a dense structure in the thickness direction.

  The collection body 5 for collecting the ultrafine fiber mixed web 6 in which the ultrafine fiber 2 and the heat-fusible fiber 4 are mixed may be a roll or a net. So that the ultrafine fiber mixed web 6 is not disturbed or scattered by the collision with the airflow that transports the airflow, and the collector 5 is preferably air permeable, and further includes an airflow suction device on the side opposite to the collection surface. It is preferable.

The spunbonded nonwoven fabric 7 may or may not be heat-sealed between the fibers, but it is partly so as to be excellent in rigidity and easy to handle in the process. It is preferable to heat-seal. In the case of partial fusion as described above, the area per fusion part is preferably 0.1 cm ² or less so that the pressure loss of the spunbond nonwoven fabric itself does not increase, and 0.05 cm ² The following is more preferable. Further, the total area ratio of the fused portion is preferably 70% or less, and more preferably 50% or less. In addition, although the shape of a melt | fusion part is not specifically limited, For example, circular, polygonal shape (for example, a rhombus, a square, a rectangle, a hexagon, a parallelogram) etc. can be mentioned. Further, the fused portion may be a straight line or a curved line, and may be in a mesh state in which these are combined.

  Further, as described above, it is preferable that the spunbonded nonwoven fabric is not bonded with a resin binder so that the pressure loss does not increase.

  As shown in FIG. 1, when the heat-fusible fiber 4 of the ultrafine fiber mixed web 6 is fused, the heat treatment is performed at a temperature equal to or higher than the melting point of the fusion component of the heat-fusible fiber 4 and the ultrafine fiber 2 (in some cases, other It is preferable that the heat treatment be carried out at a temperature lower than the melting point (including the above-mentioned fibers) in a state where no mechanical pressure is applied. By doing so, the ultrafine fiber 2 is not formed into a film, can exhibit its original collection performance, and the relatively coarse space formed by the heat-fusible fiber is not impaired, and pressure loss is reduced. Since it does not become high, the filter medium 11 for air filters which can be used for a long period of time can be manufactured. Further, the bulky air filter medium 11 can be manufactured, in which the fusion is not biased to the vicinity of the surface of the air filter medium 11 and the air filter medium 11 is firmly fused. At the same time, the heat-bondable fibers 4 can be bonded to the spunbond nonwoven fabric 7. In addition, the fiber which comprises the spunbond nonwoven fabric 7 can also be melt | fused, and it can participate in the fusion | fusion integration of the spunbond nonwoven fabric 7 and the ultrafine fiber mixed web 6. FIG.

  Examples of the heat treatment apparatus 8 capable of performing such heat treatment include a hot air circulation type dryer and a suction type air through dryer. For example, when the ultrafine fiber is made of a polypropylene resin and the fusion component of the heat-fusible fiber is made of a polyethylene resin, it is preferable to perform the fusion by setting the atmospheric temperature of the heat treatment apparatus 8 to 135 to 150 ° C.

  Thus, the air filter medium 11 which has an unevenness | corrugation on the surface can be manufactured by implementing the embossing process with the embossing apparatus 10 with respect to the fusion | melting laminated web 9 fuse | fused with the heat-fusible fiber. In this embossing treatment, a cold calender roll is applied to the heat-bonded laminated web 9 in which the heat-fusible fiber (in some cases, the spunbond nonwoven fabric constituting fiber) is melted or still heated to form irregularities. Alternatively, a heat calender roll may be applied to the heat-bonded laminated web 9 in a solidified state in which the heat-fusible fibers (and possibly the spunbond nonwoven fabric constituting fibers) are not heated to form irregularities. Also good. In addition, in any calendar roll, a pair of rolls in which the convex portion of one roll and the concave portion of the other roll are fitted so that the air filter medium itself has concave and convex portions corresponding to the convex portion and the concave portion. Is preferably used. Moreover, when using a heat | fever calendar roll, it is preferable to adjust temperature and a pressure suitably so that an ultrafine fiber may not be fused.

  In addition, after heat-processing with a heat processing apparatus, after passing between smooth rolls or flat plate press under the temperature lower than melting | fusing point of any fiber which comprises the filter medium 11 for air filters, after adjusting thickness, embossing Unevenness can also be formed by the apparatus. Moreover, in order to raise collection efficiency more, after forming an unevenness | corrugation with an embossing apparatus, an electretization process can also be implemented. In addition, when electret-ized, in order to further increase the efficiency, it is preferable to perform the electret after the fiber oil agent of the heat-fusible fiber is reduced as much as possible by washing with water or hot water.

  The above is for the case where ultrafine fibers are formed by the melt blow method, but as disclosed in JP-A-2009-287138, an electrospinning method, a liquid discharge unit capable of discharging a spinning solution, and the liquid discharge unit In the case where the ultrafine fiber is formed by a spinning device that is located upstream of the gas discharge unit and is capable of discharging gas, the air filter is exactly the same except that the spinning device is used instead of the melt blowing device. Filter media can be produced.

  Further, at the same time as forming the fused laminated web 9 by fusing the heat-fusible fiber, it is not necessary to bond with the spunbond nonwoven fabric 7, and the ultra-fine fiber mixed web is formed by fusing the heat-fusible fiber. Later, it may be bonded to a spunbond nonwoven fabric. Further, it is not necessary to bond with the spunbond nonwoven fabric by fusing the heat-fusible fiber, it may be bonded by the fusing force of the fibers constituting the spunbond nonwoven fabric, may be bonded by a hot melt resin, or a liquid binder. May be coupled by a needle punch.

  Next, the pleated type air filter unit of the present invention (hereinafter sometimes simply referred to as “air filter unit”) is a pleat-processed air filter medium as described above fixed with a frame. It is. Therefore, the structural pressure loss does not increase, and the pleated air filter unit has a large amount of dust supply. Moreover, it can be manufactured with good workability.

  The air filter unit of the present invention can be exactly the same as the conventional pleated type air filter unit except that the air filter medium as described above is used. In addition, it is preferable to arrange | position so that the spunbond nonwoven fabric layer may be located in the downstream of the filtration air of an ultrafine fiber mixed layer so that the filtration performance of an ultrafine fiber mixed layer may not be inhibited.

  The pleating process is not limited as long as it can be folded into a zigzag shape. For example, the pleating process can be performed by a pleating machine such as a reciprocating type or a rotary type, or a method of pressing with a pressing die formed in a zigzag shape.

  The filter medium for an air filter according to the present invention has a Gurley stiffness of 18 mN or more, and has a concavo-convex structure on the main surface, and the adjacent filter media are difficult to adhere to each other. In particular, even when pleated at a high peak height, such as 100 mm or more, the filter media is not easily deformed, and even if it is deformed, adjacent filter media do not adhere to each other, resulting in structural pressure loss. It is hard to rise.

The pleated state will be described with reference to FIG. 3, which is a partially enlarged perspective view of the pleated air filter medium. The ridge line 112 and the valley line 113 of the air filter medium on which the pleats are formed. between each of the wall surfaces 120, 130 face each other, the first protrusion _{a 1 (121), B 1} (131) and the second protrusion _{a 2 (122), B 2} (132) is provided In any of the wall surfaces 120 and 130, the second protrusions A ₂ (122) and B ₂ (132) are the first protrusions A ₁ (121) and B ₁ (131) and the pleat mountain line. 112 is formed apart from the first protrusions A ₁ (121) and B ₁ (131), and the height of the second protrusions A ₂ (122) and B ₂ (132) of the first protrusion _a 1 (121) is Lower than the height of _one (131).

The protrusion A ₁ (121) is close to the mountain line 112 on the side close to the mountain line 112, and has a rounded triangular mountain line side slope 214 with the short side 212 as the base and the first vertex 215 as the tip, and the valley line 113. And a rounded trapezoidal valley-side slope 216 having a short side 213 as a base and a second vertex 217 as a tip, and the height of the first vertex 215 is the height of the second vertex 217. It is higher than the height, and a line 218 connecting the first vertex 215 and the second vertex 217 is a ridge line, which is the tip of the protruding portion A ₁ (121).

In addition, a first protrusion A ₁ ′ (121 ′) having the same shape as the first protrusion A ₁ (121) is adjacent to the first protrusion A ₁ (121) and protrudes to the back side of the fused laminated web. Are arranged to be. Then, the first protrusion A ₁ and '(121') and the first protrusion A _{1 (121),} at a position of point symmetry, and has a further front and back tipping positional relationship. Further, the wall surface 130 has a first protrusion B ₁ (131) having a shape symmetrical to the first protrusions A ₁ (121) and A ₁ ′ (121 ′), with the valley line 113 as the axis of symmetry. B ₁ ′ (131 ′) is arranged. Therefore, when the pleats are formed, the tip 218 of the first protrusion A ₁ (121) and the tip of the first protrusion B ₁ (131) are in contact with each other. Further, the tip of the first protrusion A ₁ ′ (121 ′) and the tip of the first protrusion B ₁ ′ (131 ′) are in contact with each other.

In addition to the first projecting portion, the second projecting portions A ₂ (122) and B ₂ (132) are provided on any of the wall surfaces 120 and 130. A _second protrusion A ₂ (122) having a bottom surface consisting of a long side 221 and short sides 222, 223 on the wall surface 120 has a long side 221 parallel to the longitudinal direction (or the pleat forming direction) of the air filter medium. It is arranged to have. The protrusion A ₂ (122) has a mountain-side slope with a short side 222 on the side close to the mountain line 112, and a valley-side slope with a short side 223 on the side near the valley line 113. The tip of the protrusion A ₂ (122) has a quadrangular shape parallel to the wall surface 120.

The second protrusion A _{2 (122)} and the second protrusion A ₂ of the same shape '(122') is arranged so as to protrude to the back side of the filter medium for an air filter. Then, the second projecting portion A ₂ and '(122') and the second protrusion A _{2 (122),} at a position of point symmetry, and has a further front and back tipping positional relationship. The wall surface 130 has a second protrusion B ₂ (132) having a shape symmetrical with the second protrusions A ₂ (122) and A ₂ ′ (122 ′) with the valley line 113 as the axis of symmetry. , B ₂ ′ (132 ′) is arranged.

The heights of the second protrusions A ₂ (122) and B ₂ (132) are the heights (protrusions) of the first protrusions A ₁ (121) and B ₁ (131) so that the airflow resistance is small. Is preferably lower than the maximum height of the portion.

In FIG. 3, the second protrusions A ₂ and B ₂ are formed between the first protrusions A ₁ (121) and B ₁ (131) and the pleat mountain line 112. The parts A ₁ and B ₁ are separated from each other so as to be adjacent to each other.

Furthermore, in addition to the second protrusion _A 2, _{B 2,} the second protrusion _A 2, _{B 2} same form as the projecting portion _{A 3} of the '(123'), another _{B 3} a '(133') It arrange | positions as a 2nd protrusion part. More specifically, another second protrusion A ₃ (123) having the same shape as A ₃ ′ (123 ′) is arranged so as to protrude to the back side of the filter medium for air filter. Then, the second projecting portion A ₃ of the other ₍₁₂₃₎ and another second protrusion A ₃ '(123'), at a position of point symmetry, and has a further positional relationship sides are upset. Further, another second protrusion B ₃ having a shape symmetrical to another second protrusions A ₃ ′ (123 ′) and A ₃ (123) with the valley line 113 as the axis of symmetry is provided on the wall surface 130. '(133') and B ₃ (133) are arranged.

  The air filter medium can be fixed by the frame, for example, by interposing a hot melt resin such as polyvinyl acetate between the frame and the air filter medium. In addition, as a frame, what consists of aluminum, aluminum alloy, stainless steel, or various resin can be used, for example.

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

(Production of ultra-fine fiber mixed web)
A melt-blowing nozzle piece arranged with an orifice diameter of 0.2 mm and a pitch of 0.8 mm was heated to a temperature of 320 ° C., and polypropylene fibers were discharged at a rate of 0.04 g / min per orifice. An ultrafine fiber 2 having a fiber diameter of 1 to 2 [mu] m (average fiber diameter of 1.5 [mu] m) in the same direction as the direction in which gravity acts by applying air of a mass ratio of 340 [deg.] C. and a mass ratio of 83 times to the discharged polypropylene fiber. A flow of (melting point: 160 ° C.) was formed.

  Next, two opening cylinders 31 as shown in FIG. 2 are accommodated in the housing 32 so as to form an angle of 65 ° (θ in FIG. 1) with the flow of the ultrafine fibers 2. The core sheath is made of polypropylene resin (melting point 160 ° C.) and the sheath component is made of polyethylene resin (melting point 135 ° C.), and the core sheath is stretched with a fiber diameter of 17 μm and a fiber length of 38 mm. 100 mass% of the mold heat-fusible fiber was supplied and mixed with the polypropylene extra fine fiber 2. The mixed fibers were collected by a mesh conveyor 5 to produce an ultrafine fiber mixed web 6. In addition, air was sucked and removed from the opposite side of the collecting surface of the conveyor 5 to prevent the ultrafine fiber mixed web 6 from being disturbed. The ultrafine fiber mixed web 6 is composed of 8 mass% extrafine fiber and 92 mass% core-sheath type heat-fusible fiber, and the ultrafine fiber is formed on the collecting surface side surface (B surface) of the conveyor 5. Is about 3.5 mass% (core-sheath type heat-fusible fiber: about 96.5 mass%), and the amount of extra fine fibers increases toward the surface (A surface) facing the collection surface side surface (B surface) Gradually decreased, and on the side A, ultrafine fibers were present at about 0.5 mass% (core-sheath type heat-fusible fiber: about 99.5 mass%).

(Examples 1-3, Comparative Examples 1-4)
A partially bonded spunbond nonwoven fabric 7 as shown in Table 1 was prepared. In addition, none of the spunbonded nonwoven fabrics were bonded with a resin binder.

＃：ＰＥＴ／ＰＥ・・ポリエステル（芯、融点：２６４℃）／ポリエチレン（鞘、融点：１３５℃）からなる芯鞘型複合繊維（平均繊維径：１９μｍ）

#: Core-sheath type composite fiber (average fiber diameter: 19 μm) made of PET / PE..polyester (core, melting point: 264 ° C.) / Polyethylene (sheath, melting point: 135 ° C.)

  Subsequently, the spunbond nonwoven fabric 7 was laminated on the B surface of the ultrafine fiber mixed web 6. Thereafter, the laminate is passed through the dryer 8 at a temperature of 137 ° C. for 1 minute, so that it is fused with the sheath component (polyethylene component) of the core-sheath type heat-fusible fiber and the polyethylene component of the spunbond nonwoven fabric without applying pressure. Thus, the fused laminated web 9 was formed. The collection efficiency, initial pressure loss, and dust supply amount of the fused laminated web 9 are as shown in Table 2.

Then, the fused fiber web is supplied between a pair of rolls having irregularities and the irregularities are fitted to each other (temperature: 80 ° C., slit interval: 0.3 mm), and the concaves and convexes correspond to the concaves and convexes, In addition, fold lines of mountain lines (112 in FIG. 3) and valley lines (113 in FIG. 3) were formed, and air filter media of the present invention as shown in Table 3 were produced. The basis weight of the ultrafine fiber mixed layer was 105 g / m ² , the thickness was 1.10 mm, and the apparent density was 0.095 g / cm ³ .

Moreover, the uneven | corrugated state was as FIG. 3, and the specific dimension was as follows.
(1). Distance between mountain line 112 and valley line 113: 125 mm
(2). First protrusion A ₁ (121): length of short side 212 = 8 mm, length of long side 211 = 90 mm, height of first vertex 215 = 7 mm, height of second vertex 217 = 4 mm , Area 218 connecting the first vertex 215 and the second vertex 217 = trapezoid (upper base: 2 mm, lower base: 6 mm, height: 61 mm)
(3). First protrusion _{A 1} '(121'): the first protrusion _A 1 (121) and projecting on the rear side in the same shape, distance = 10 mm between the first protrusion _A 1 (121)
(4). The first projecting portion _B 1 (131): the first projecting portion _A 1 and (121) the same shape, positioned a valley 113 as axis of symmetry (5). The first projecting portion _{B 1} '(131'): the first protrusion _{A 1} '(121') and the same shape, positioned a valley 113 as axis of symmetry (6). Second protrusion A ₂ (122): distance from pleat mountain line 112 = 5 mm, distance from first protrusion A ₁ (121) = 2 mm, height = 3 mm, length of long side (221) = 13 mm, length of short side (222) = 8 mm, tip surface = rectangular (6 mm × 4 mm)
(7). Second protrusion _{A 2} '(122'): the second protrusion _A 2 (122) and projecting on the rear side in the same shape, positioned in the second protrusion _A 2 (122) and point symmetry (8) . Second protrusion _B 2 (132): In the second protrusion _A 2 (122) and the same shape, positioned a valley line 113 as a symmetry axis (9). Second protrusion B ₂ ′ (132 ′): the same shape as the second protrusion A ₂ ′ (122 ′), with the valley line 113 as the axis of symmetry (10). Second protrusion A ₃ ′ (123 ′): distance from the pleat mountain line 112 = 5 mm, distance from the first protrusion A ₁ ′ (121 ′) = 2 mm, height = 3 mm, bottom surface = rectangular ( 8mm x 13mm), tip surface = rectangular (6mm x 2mm)
(11). Second protrusion _{B 3} '(133'): In the second protrusion _{A 3} '(123') and the same shape, positioned a valley line 113 as a symmetrical axis (12). Second protrusion _A 3 (123): In the second protrusion _{A 3} '(123') and the same shape, protruding on the rear side, positioned in the second projecting portion _{A 3} '(123') and point symmetry (13). Second protrusion _B 3 (133): In the second protrusion _A 3 (123) and the same shape, positioned a valley line 113 as a symmetrical axis

(Evaluation of air filter unit)
The filter media for air filters of Examples 1 to 3 and Comparative Examples 1 to 4 were pleated at a pleat interval of 8 mm, and then the top and bottom of the pleated filter media for air filters were polyester non-woven fabric (weight per unit: 200 g / m ^2). And a thickness of 2.6 mm) and a hot melt nonwoven fabric coated with a hot melt resin (weight per unit: 600 g / m ² , ethylene-vinyl acetate copolymer). An air filter unit having a depth of 150 mm was produced.

  And this air filter unit was fixed to the measurement frame, and the collection efficiency, the initial pressure loss, and the dust supply amount were measured with the spunbonded nonwoven fabric layer being the downstream side of the filtered air according to JIS B 9908 (2001) type 2. . The results are shown in Table 4.

  From Tables 3 and 4, since the Gurley bending resistance of the filter medium for air filter is 18 mN or more, and because it has irregularities, the adjacent filter medium does not adhere to each other, and the structural pressure loss is low. It was found that this is a pleated air filter medium that can fully demonstrate its performance and has a large amount of dust supply.

  The filter medium for a pleated type air filter of the present invention is a pleated air filter unit and can be suitably used for air conditioning equipment in general buildings, factory air conditioning equipment, computer rooms and hospital air conditioning equipment.

DESCRIPTION OF SYMBOLS 1 Melt blow apparatus 2 Ultrafine fiber 3 Opening machine 31 Opening cylinder 32 Housing 33 Air nozzle 4 Heat-fusible fiber 5 Collecting body 51 Suction apparatus 6 Ultrafine fiber mixed web 7 Spunbond nonwoven fabric 8 Heat treatment apparatus 9 Fusion lamination web 10 Embossing apparatus 11 Filter media for pleated type air filter 112 Mountain line 113 Valley line 120, 130 Wall surface 121 First protrusion A ₁
121 ′ first protrusion A ₁ ′
131 first protrusion _{B 1}
131 ′ first protrusion B ₁ ′
122 second protrusion _{A 2}
122 ′ second protrusion A ₂ ′
123 second protrusion _{A 3}
123 ′ second protrusion A ₃ ′
132 2nd protrusion B ₂
132 ′ second protrusion B ₂ ′
133 Second protrusion B ₃
133 ′ second protrusion B ₃ ′
212, 213 Short side 214 Mountain line side slope 215 First vertex 216 Valley line side slope 217 Second vertex 218 Edge, _first tip 221 of _first protrusion A ₁ Long side 222, 223 Short side

Claims (2)

A pleated air filter medium having a spunbond nonwoven fabric layer and an ultrafine fiber mixed layer that satisfy the following conditions (1) to (4).
(1) The basis weight of the spunbond nonwoven fabric layer is 10 to 90 g / m ² (2) The ultrafine fiber mixed layer is an ultrafine fiber having an average fiber diameter of 0.1 to 10 μm and a heat-fusible property having an average fiber diameter of 10 to 100 μm. (3) The filter medium for the pleated type air filter has irregularities (4) The Gurley stiffness of the filter medium for the pleated type air filter is 18 mN or more. Is A pleated air filter unit, wherein the pleated air filter medium according to claim 1, which has been pleated, is fixed by a frame.

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