JP2013094717A - Air filter medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air filter medium which has high collection efficiency, in which the increase of pressure loss is suppressed and of which the lifetime is prolonged.SOLUTION: An air filter medium includes a laminate of a filter layer, a prefilter layer, and an adhesive layer. In the filter layer, a polytetrafluoroethylene porous membrane and an air-permeable fiber layer are laminated. The prefilter layer is laminated on one side of the filter layer, and the adhesive layer is provided between the filter layer and the prefilter layer. In the filter layer, both outermost layers are air-permeable fiber layers. An average fiber diameter of fibers constituting the prefilter layer is 0.6 to 15 μm, and the average fiber diameter of fibers constituting the air-permeable fiber layer is 10 to 30 μm. The average fiber diameter of fibers constituting the air-permeable fiber layer is larger than the average fiber diameter of fibers constituting the prefilter layer. The adhesive layer is a fiber layer of which the basis weight is 5 to 10 g/m.

Description

  The present invention relates to an air filter medium using a polytetrafluoroethylene (PTFE) porous membrane, and in particular, is used for capturing or removing suspended particles in a gas such as a turbine intake filter medium and a mask filter medium. The present invention relates to an air filter medium.

  Conventionally, glass filter media made by making paper by adding a binder to glass fibers have been often used as air filter media used for turbine intake and the like. Such a glass filter medium has several problems. For example, a glass filter medium has a problem that self-generated dust is generated when processing such as bending is performed because adhering fibrils are present therein.

  In recent years, filter media including a PTFE porous membrane has begun to be used as a high performance air filter media for clean rooms in the semiconductor industry. The filter medium described in Patent Document 1 is an example. A filter medium including a PTFE porous membrane is suitable as an air filter medium because it has high collection efficiency and low pressure loss. However, because of the high collection efficiency, clogging occurs early and the pressure loss increases, so that the filter medium including the PTFE porous membrane has a problem in terms of its life.

  Various studies have been made in order to prevent clogging of the PTFE porous membrane and extend the life of the air filter medium. For example, Patent Document 2 and Patent Document 3 disclose that a prefilter layer capable of collecting large dust in advance is provided on the upstream side of the air flow with respect to the PTFE porous membrane. As the prefilter layer, a breathable support material such as a nonwoven fabric made of fibers is used. Patent Document 4 discloses a filter medium in which two types of breathable support materials made of fibers having different diameters and a PTFE porous membrane are laminated. Patent Document 5 discloses a filter medium in which two types of PTFE porous membranes having different collection efficiencies are laminated.

  These techniques do not particularly limit the laminated structure of the PTFE porous membrane and other layers such as a prefilter layer and the configuration of the filter medium. However, the effect of the laminated structure and configuration on the performance of the air filter medium is large, and in some cases, even if a device such as providing a prefilter layer is devised, the life of the filter medium is not greatly extended. Depending on the laminated structure and configuration, the handling property of the filter medium is deteriorated. For example, if the pleating process is performed on the filter medium having the PTFE porous membrane provided in the outermost layer, the PTFE porous membrane is easily damaged. Thus, knowledge about the optimal laminated structure of the PTFE porous membrane and other layers and the optimal configuration of the air filter medium including the PTFE porous membrane has not been sufficient.

JP 2000-61280 A JP 2002-370009 A Japanese Patent Laid-Open No. 2000-300921 JP 2002-370020 A JP 2005-205305 A

  An object of the present invention is to provide an air filter medium having a high collection efficiency, an increase in pressure loss, and a long life.

That is, the present invention
A filter layer in which a PTFE porous membrane and a breathable fiber layer are laminated;
A pre-filter layer laminated on one side of the filter layer;
An adhesive layer provided between the filter layer and the prefilter layer;
Including a laminate of
Both outermost layers in the filter layer are the breathable fiber layers,
The average fiber diameter of the fibers constituting the prefilter layer is 0.6 to 15 μm,
The fiber constituting the breathable fiber layer has an average fiber diameter of 10 to 30 μm,
The average fiber diameter of the fibers constituting the breathable fiber layer is larger than the average fiber diameter of the fibers constituting the prefilter layer,
The adhesive layer is a fiber layer having a basis weight of 5 to 10 g / m ² .
An air filter medium is provided.

The air filter medium of the present invention includes a laminate of a prefilter layer, an adhesive layer, and a filter layer. The prefilter layer is made of fibers having an average fiber diameter of 0.6 to 15 μm, and is provided on one side of the filter layer. Thereby, the raise of the pressure loss accompanying use of an air filter medium can be suppressed. The filter layer includes a PTFE porous membrane together with a breathable fiber layer. Thereby, an air filter medium having a high collection efficiency can be obtained. The average fiber diameter of the fibers constituting the breathable fiber layer is 10 to 30 μm, which is larger than the average fiber diameter of the fibers constituting the prefilter layer. Thereby, the filter layer can have high air permeability. The adhesive layer is provided between the filter layer and the prefilter layer. The adhesive layer is a fiber layer having a basis weight of 5 to 10 g / m ² . The outermost layer of the filter layer and in contact with the adhesive layer is a breathable fiber layer. Thus, clogging between the PTFE porous membrane and the prefilter layer is suppressed, and an air filter medium in which the PTFE porous membrane and the prefilter layer are firmly integrated can be obtained. The outermost layer of the filter layer that is further away from the adhesive layer is also a breathable fiber layer. Accordingly, the PTFE porous membrane can be protected when performing processing such as pleating on the air filter medium, and damage to the PTFE porous film associated with the use of the air filter medium can be prevented. Therefore, according to the present invention, it is possible to obtain an air filter medium having a high collection efficiency, an increase in pressure loss, and a long life.

It is typical sectional drawing which shows the air filter medium which is one Embodiment of this invention. It is typical sectional drawing which shows the air filter medium which is another embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic cross-sectional view showing an air filter medium according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing an air filter medium that is another embodiment of the present invention. In any of the drawings, when used, the air filter medium is arranged with the upper side of the drawing as the upstream side of the airflow. Further, hereinafter, the upstream side of the airflow may be simply referred to as “upper side”.

  An air filter medium 100 shown in FIG. 1 includes a filter layer 10, an adhesive layer 20 laminated so as to be in contact with one surface of the filter layer 10, and a prefilter layer laminated so as to be in contact with the other surface of the adhesive layer 20. 30. The filter layer 10 is a laminate in which a PTFE porous membrane 11 and a breathable fiber layer 12 are laminated. As shown in FIG. 1, both outermost layers in the filter layer 10 are breathable fiber layers 12. In the filter medium 100, the filter layer 10 has a laminated structure of air permeable fiber layer 12 / PTFE porous membrane 11 / air permeable fiber layer 12. In the filter medium 100, the adhesive layer 20 is composed of a single layer. Thus, the filter medium 100 has a laminated structure of prefilter layer 30 / adhesive layer 20 / breathable fiber layer 12 / PTFE porous membrane 11 / breathable fiber layer 12 in order from the top.

  The air filter medium 200 shown in FIG. 2 differs from the air filter medium 100 shown in FIG. 1 only in that the adhesive layer 20 is a laminate of two layers. The adhesive layer 20 in the filter medium 200 is formed by laminating a first adhesive layer 21 in contact with the breathable fiber layer 12 and a second adhesive layer 22 in contact with the prefilter layer 30. In this way, the filter medium 200 is composed of the prefilter layer 30 / second adhesive layer 22 / first adhesive layer 21 / breathable fiber layer 12 / PTFE porous membrane 11 / breathable fiber layer 12 in order from the upper side. It has a laminated structure.

  Hereinafter, each layer constituting the air filter medium 100, 200 will be described.

<Prefilter layer>
The prefilter layer 30 is provided on the upstream side of the airflow with respect to the filter layer 10. The prefilter layer 30 is laminated so as to be in contact with one surface of the adhesive layer 20. The pre-filter layer 30 has a function of preventing clogging of the PTFE porous membrane 11 by preliminarily collecting relatively large dust in the atmosphere while having moderate air permeability. Since the prefilter layer 30 suppresses an increase in pressure loss due to the use of the filter media 100 and 200, the life of the filter media 100 and 200 is extended. The PTFE porous membrane 11 is weak in strength because it is thin by stretching, and it is difficult to use it alone as an air filter medium. The prefilter layer 30 also has a function of reinforcing the PTFE porous membrane 11.

  The prefilter layer 30 is made of fibers such as short fibers and filaments, and has better air permeability than the PTFE porous membrane, such as non-woven fabric, woven fabric, mesh (mesh sheet) and other porous materials. Can be used. Among these, a nonwoven fabric is preferable because it is excellent in terms of strength, flexibility, and workability.

  If the average fiber diameter of the fibers constituting the prefilter layer 30 is 0.6 μm or more, the prefilter layer 30 can have sufficient strength and air permeability. If the average fiber diameter of the fibers constituting the prefilter layer 30 is 15 μm or less, the prefilter layer 30 can have a collection efficiency sufficient to collect relatively large dust in the atmosphere. Therefore, the average fiber diameter of the fibers constituting the prefilter layer 30 is 0.6 to 15 μm, and preferably 0.6 to 3.0 μm.

  In addition, the average fiber diameter in this specification can be measured using an optical microscope as mentioned later.

  The smaller the average fiber diameter of the fibers constituting the layer, the better the performance of the layer for collecting dust. Therefore, the average fiber diameter of the fibers constituting the prefilter layer 30 is preferably smaller than the average fiber diameter of the fibers constituting the breathable fiber layer 12. Accordingly, the prefilter layer 30 previously collects relatively large dust in the atmosphere on the upstream side of the airflow, and the PTFE porous membrane 11 collects finer dust on the downstream side of the airflow. Filter media 100 and 200 can be realized. From the same viewpoint, it is preferable that the average fiber diameter of the fibers constituting the prefilter layer 30 is smaller than the average fiber diameter of the fibers constituting the adhesive layer 20.

The thickness of the prefilter layer 30 is, for example, 0.12 to 0.35 mm. As a material of the fibers constituting the prefilter layer 30, a core-sheath structure in which polyester such as polypropylene (PP) and polyethylene terephthalate (PET), a core part is made of PET, and a sheath part is made of polyethylene (PE) is used. Examples thereof include fibers (PET / PE fibers), polyamide, nylon, polyphenylene sulfide (PPS), and the like. The fiber material constituting the prefilter layer 30 preferably has high chemical resistance and a good balance between low melting point and heat resistance from the viewpoint of manufacturing. For these reasons, the prefilter layer 30 is preferably composed of PP fibers. The basis weight of the prefilter layer 30 is preferably 5 to 100 g / m ² from the viewpoints of handling properties, pressure loss, and collection performance.

<Filter layer>
The filter layer 10 is composed of a laminate of a breathable fiber layer 12 and a PTFE porous membrane 11. As the PTFE porous membrane 11 in the filter layer 10, any pore diameter, thickness, porosity and the like can be used without particular limitation as long as the collection performance corresponding to the intended use of the filter medium 100 is exhibited. .

  The thickness of the PTFE porous membrane 11 is appropriately determined depending on the size of the filter medium to be produced and is, for example, 2 to 100 μm. The average pore diameter of the PTFE porous membrane 11 is, for example, 0.5 to 50 μm.

  The method for producing the PTFE porous membrane 11 is not particularly limited as long as the collection performance corresponding to the intended use of the filter medium 100 is exhibited. As a manufacturing method of the PTFE porous membrane 11, the manufacturing method described in Unexamined-Japanese-Patent No. 10-030031, international publication 94/16802 pamphlet etc. is mentioned, for example. An example of the manufacturing method of the PTFE porous membrane 11 is shown below.

  First, a liquid lubricant is added to and mixed with the unfired PTFE fine powder. The PTFE fine powder (PTFE fine powder) is not particularly limited, and commercially available products can be used. The liquid lubricant is not particularly limited as long as it can wet the surface of the PTFE fine powder and can be removed later, hydrocarbon oils such as naphtha, white oil, liquid paraffin, toluene, xylene, alcohols, Ketones and esters can be used. Two or more liquid lubricants may be used in combination.

  The addition ratio of the liquid lubricant to the PTFE fine powder is appropriately determined depending on the type of the PTFE fine powder, the type of the liquid lubricant, and the conditions of sheet molding described later. For example, for 100 parts by weight of the PTFE fine powder, It is 15-35 weight part of liquid lubricants.

  Next, a mixture of the unfired PTFE fine powder and the liquid lubricant is formed into a sheet shape in an unfired state to obtain a sheet-like molded body. Examples of the sheet forming method include a rolling method in which the mixture is extruded in a rod shape and then rolled with a pair of rolls, and an extrusion method in which the mixture is extruded in a plate shape to form a sheet. Two or more methods may be combined to form a sheet. Although the thickness of a sheet-like molded object is suitably determined by the conditions of extending | stretching performed later, etc., it is 0.1-0.5 mm, for example.

  The liquid lubricant contained in the sheet-shaped molded body is preferably removed by a heating method, an extraction method or the like before the subsequent stretching step. The solvent used in the extraction method is not particularly limited, and examples thereof include normal decane, dodecane, naphtha, kerosene, and sumoyl.

  Next, it extends | stretches with respect to a sheet-like molded object. As the stretching method, biaxial stretching is preferred. For example, after the sheet-like molded product is stretched at a temperature of 150 to 390 ° C. so that the length in the longitudinal direction is 2 to 60 times, the temperature is set so that the length in the width direction is 10 to 60 times. The PTFE porous membrane 11 is obtained by stretching at 40 to 150 ° C. In addition, after extending | stretching, you may heat and heat more than the melting point of PTFE.

  The breathable fiber layer 12 in the filter layer 10 maintains the performance of the PTFE porous membrane 11 and the pre-filter layer 30 and prevents problems that may occur with the manufacture, processing, and use of the filter media 100 and 200. Have For the breathable fiber layer 12, a material having sufficient breathability is used. Specifically, the breathable fiber layer 12 is made of a material such as a nonwoven fabric, a woven fabric, or a mesh (mesh-like sheet) that is made of fibers such as short fibers and filaments and that is more breathable than the PTFE porous membrane 11. ) And other porous materials can be used. Among these, a nonwoven fabric is preferable because it is excellent in terms of strength, flexibility, and workability.

  Conventionally, a filter medium has been manufactured by integrating a laminate obtained by stacking a prefilter layer so as to be in contact with a PTFE porous membrane. However, in such a case, clogging occurs at the interface between the prefilter layer and the PTFE porous membrane during integration, so that the pressure loss of the filter medium increases, and the pressure loss associated with the use of the filter medium also increases. Easy to grow.

  On the other hand, according to this embodiment, the PTFE porous membrane 11 is located between the two air permeable fiber layers 12 in the filter layer 10. As described above, the average fiber diameter of the fibers constituting the breathable fiber layer 12 is larger than the average fiber diameter of the fibers constituting the prefilter layer 30. That is, the breathable fiber layer 12 has a higher breathability than the prefilter layer 30. Therefore, even if the breathable fiber layer 12 is laminated so as to be in contact with the PTFE porous membrane 11, clogging is less likely to occur. In particular, the outermost layer of the filter layer 10 and the layer on the prefilter layer 30 side (the layer in contact with the adhesive layer 20) is the breathable fiber layer 12. In other words, the uppermost layer of the filter layer 10 (the outermost layer of the filter layer 10 on the upstream side of the airflow) is the breathable fiber layer 12. Therefore, it is not the surface of the PTFE porous membrane 11 but the surface of the air permeable fiber layer 12 that is the uppermost layer of the filter layer 10 and has high air permeability that is involved in the integration with the prefilter layer 30. Since the prefilter layer 30 is not directly laminated on the PTFE porous membrane 11, the above-described problems can be suppressed. Accordingly, it is possible to realize the filter media 100 and 200 in which the increase in pressure loss is suppressed, the lifetime is long, and the PTFE porous membrane 11 and the prefilter layer 30 are firmly integrated.

  Further, the outermost layer of the filter layer 10 and the layer farther from the prefilter layer 30 is also the breathable fiber layer 12. In other words, the lowermost layer of the filter layer 10 (the outermost layer of the filter layer 10 on the downstream side of the airflow) is the breathable fiber layer 12. Therefore, the PTFE porous membrane 11 in the filter media 100 and 200 is protected by the breathable fiber layer 12 from both sides. Therefore, even if processing such as pleating is performed on the filter media 100 and 200, the PTFE porous membrane 11 is not damaged. Therefore, it is possible to realize the filter media 100 and 200 having excellent handling properties during processing such as pleating.

  The breathable fiber layer 12 in contact with the surface of the PTFE porous membrane 11 has a function of supporting the PTFE porous membrane 11 when the filter media 100 and 200 are used. When the average fiber diameter of the fibers constituting the breathable fiber layer 12 is too large, the distance between the contact points between the fibers constituting the breathable fiber layer 12 and the PTFE porous film 11 becomes long. A portion that is not sufficiently supported by the breathable fiber layer 12 is generated. If the PTFE porous membrane 11 is not sufficiently supported, the PTFE porous membrane 11 is easily damaged by pleating the filter media 100 and 200 and using the filter media 100 and 200 after pleating. When the PTFE porous membrane 11 is damaged, the collection efficiency of the filter media 100 and 200 is reduced due to the occurrence of leakage, and the life of the filter media 100 and 200 is shortened. On the other hand, when the average fiber diameter in the air permeable fiber layer 12 is too small, the pressure loss of the filter media 100 and 200 tends to increase. For these reasons, the average fiber diameter of the fibers constituting the breathable fiber layer 12 is 10 to 30 μm, and preferably 15 to 25 μm. When the average fiber diameter of the fibers constituting the breathable fiber layer 12 is within this range, it is possible to realize the filter media 100 and 200 having high collection efficiency, an increase in pressure loss, and a long life.

  As described above, by laminating the PTFE porous membrane 11 with the air permeable fiber layer 12 to form the filter layer 10, it is possible to realize the filter media 100 and 200 that sufficiently exhibit the excellent performance of the PTFE porous membrane 11.

  As long as both outermost layers in the filter layer 10, that is, the uppermost layer and the lowermost layer in the filter layer 10 are both the breathable fiber layers 12, the laminated structure of the breathable fiber layer 12 and the PTFE porous membrane 11 in the filter layer 10. The order is not limited. In the filter layer 10, the PTFE porous membrane 11 and the air permeable fiber layer 12 may be alternately laminated, or one or both of the PTFE porous membrane 11 and the air permeable fiber layer 12 are continuously laminated. There may be parts that are. The plurality of breathable fiber layers 12 in the filter layer 10 may be the same as or different from each other. The filter layer 10 preferably has a laminated structure of a breathable fiber layer 12 / PTFE porous membrane 11 / breathable fiber layer 12. The filter layer 10 may consist of only these three layers as shown in FIGS.

The basis weight of the breathable fiber layer 12 is preferably 15 to 30 g / m ² from the viewpoint of the breathability of the filter media 100 and 200. The thickness of the air-permeable fiber layer 12 is preferably 130 to 200 μm from the viewpoint of the air permeability of the filter media 100 and 200, the handleability in pleating and the like, and the overall thickness of the filter media 100 and 200.

  Although it does not restrict | limit especially as a material of the fiber which comprises the air permeable fiber layer 12, For example, Polyester, such as polyethylene (PE) and polypropylene (PP), Polyester, such as a polyethylene terephthalate (PET), Polyamide, and these composite materials Etc. From the viewpoint that the PTFE porous membrane 11 and the air permeable fiber layer 12 can be easily and satisfactorily bonded, the fibers constituting the air permeable fiber layer 12 preferably contain a polyolefin having a low melting point, particularly polypropylene or polyethylene.

  The breathable fiber layer 12 is preferably composed of a composite fiber having a core-sheath structure in which the core component has a melting point relatively higher than that of the sheath component. A material having a relatively high melting point such as PET is used as the core component, and a material having a relatively low melting point such as polyolefin is used as the sheath component. Specifically, as a fiber having a core-sheath structure, the core part is made of PET and the sheath part is made of PE (PET / PE fiber), or the core part is made of PP and the sheath part is made of PE. (PP / PE fiber). When the breathable fiber layer 12 made of core-sheath structure fibers is used, even if the breathable fiber layer 12 and the PTFE porous film 11 are laminated by heating, the structure and thickness of the breathable fiber layer 12 change due to heat. In addition, it is possible to prevent damage to the PTFE porous membrane 11 due to shrinkage of the breathable fiber layer 12. From the viewpoint that the PTFE porous membrane 11 and the breathable fiber layer 12 can be easily and satisfactorily bonded, the breathable fiber layer 12, particularly the breathable fiber layer 12 in contact with the PTFE porous membrane 11, is made of PET / PE fibers. It is preferable to become.

  As a method for producing the filter layer 10 by integrating the laminated body of the PTFE porous membrane 11 and the air-permeable fiber layer 12, a nip lamination by heat, a lamination using an infrared heater (see Japanese Patent No. 3672868) ) And the like. Among these, a laminate using an infrared heater is preferable from the viewpoint that strong adhesion can be realized without reducing the thickness of each layer. When the breathable fiber layer 12 is made of fibers having a core-sheath structure, the heating temperature of the breathable fiber layer 12 may be set to be higher than the softening point of the sheath component (preferably higher than the melting point) and lower than the melting point of the core component. preferable.

<Adhesive layer>
The adhesive layer 20 is laminated so as to be in contact with the upper surface of the filter layer 10. The adhesive layer 20 is interposed between the air-permeable fiber layer 12 and the prefilter layer 30 that are the uppermost layers of the filter layer 10, thereby integrating the filter layer 10 and the prefilter layer 30. The adhesive layer 20 is a fiber layer having a basis weight of 5 to 10 g / m ² . When the basis weight of the adhesive layer 20 is 10 g / m ² or less, a decrease in air permeability due to the integration of the filter layer 10 and the prefilter layer 30 and an increase in pressure loss due to the use of the filter media 100 and 200 are prevented. be able to. When the basis weight of the adhesive layer 20 is 5 g / m ² or more, the prefilter layer 30 and the filter layer 10 can be firmly integrated via the adhesive layer 20.

The adhesive layer 20 is preferably a fiber layer formed by an airlaid method. The airlaid method (airlaid method) is a method of forming a fiber layer by dispersing a spread fiber group in the air, transporting it in an air stream, and depositing it on a carrier. (See, for example, JP-A-2006-81779, JP-A-2006-83396, JP-A-2006-83497, etc.). By using the airlaid method, the basis weight of the obtained fiber layer can be easily controlled. Further, by using the airlaid method, the basis weight of the adhesive layer can be minimized. Specifically, the basis weight of the adhesive layer 20 can be easily controlled to 5 to 10 g / m ² .

  Usually, as a method of integrating the two layers, after overlapping the two layers so as to contact each other, the surface of both layers is melted by heat, or an adhesive such as hot melt is applied between the two layers. The method to do is adopted. However, when such a method is used to integrate a prefilter layer made of fibers having a relatively small average fiber diameter (with a relatively high collection efficiency) and other layers, the interface between the two layers In this case, clogging is likely to occur. As a result, the pressure loss of the obtained filter medium increases, the increase in pressure loss accompanying the use of the filter medium also increases, and the life of the filter medium is shortened.

On the other hand, in this embodiment, since the filter layer 10 and the pre-filter layer 30 are integrated via the adhesive layer 20 which is a fiber layer having a basis weight of 5 to 10 g / m ² , the filter layer 10 and the pre-filter layer 30 are integrated. Clogging is unlikely to occur between the filter layer 30 and the filter layer 30. Therefore, it is possible to realize the filter media 100 and 200 having a long life in which an increase in pressure loss is suppressed.

  The thickness of the adhesive layer 20 is, for example, 30 to 70 μm. When the thickness of the adhesive layer 20 is 30 μm or more, the adhesion between the prefilter layer 30 and the adhesive layer 20 and between the adhesive layer 20 and the filter layer 10 can be improved. If the thickness of the adhesive layer 20 is 70 μm or less, the air permeability in the adhesive layer 20 can be increased.

  The average fiber diameter of the fibers constituting the adhesive layer 20 is, for example, 10 to 60 μm, and preferably 15 to 40 μm. If the average fiber diameter of the fibers constituting the adhesive layer 20 is 10 μm or more, the air permeability in the adhesive layer 20 can be increased. If the average fiber diameter of the fiber which comprises the contact bonding layer 20 is 60 micrometers or less, the adhesion | attachment between the pre filter layer 30 and the contact bonding layer 20 and between the contact bonding layer 20 and the filter layer 10 can be made favorable.

  The average fiber diameter of the fibers constituting the adhesive layer 20 is preferably larger than the average fiber diameter of the fibers constituting the breathable fiber layer 12 in the filter layer 10. Thereby, when the adhesive layer 20 is bonded to the filter layer 10, clogging at the interface between the filter layer 10 and the adhesive layer 20 can be suppressed, and an increase in pressure loss of the filter media 100 and 200 can be suppressed. . From the same viewpoint, the average fiber diameter of the fibers constituting the adhesive layer 20 is preferably larger than the average fiber diameter of the fibers constituting the prefilter layer 30.

  The adhesive layer 20 preferably includes the same material as the material included in the breathable fiber layer 12 and / or the prefilter layer 30 with which the adhesive layer 20 is in contact. Thereby, the adhesive layer 20 can adhere the filter layer 10 and the pre-filter layer 30 more firmly, and can obtain the filter media 100 and 200 which are hard to peel off. The adhesive layer 20 is preferably made of a composite fiber having a core-sheath structure in which the core component has a relatively higher melting point than the sheath component. As a composite fiber having a core-sheath structure, a core part made of PET and a sheath part made of PP (PET / PP fiber), a core part made of PET, and a sheath part made of PE (PET / PE Fiber) and the like.

  The adhesive layer 20 may be composed of two or more layers. When the material of the breathable fiber layer 12 and the prefilter layer 30 at the uppermost layer of the filter layer 10 are different from each other, by appropriately selecting the material of each layer in the adhesive layer 20 composed of two or more layers, The filter medium 200 in which the filter layer 10, the adhesive layer 20, and the prefilter layer 30 are firmly bonded to each other can be easily obtained. For example, in the filter medium 200 including two layers, that is, the adhesive layer 20 formed of a laminate of the first adhesive layer 21 and the second adhesive layer 22, the breathable fiber layer 12 that is the uppermost layer of the filter layer 10. Includes the material A, and the prefilter layer 30 includes the material B. In this case, by selecting a material containing the material A as the first adhesive layer 21, it is possible to realize strong adhesion between the filter layer 10 and the first adhesive layer 21. Further, by selecting the second adhesive layer 22 containing the material B, it is possible to realize strong adhesion between the second adhesive layer 22 and the prefilter layer 30. As a result, the filter medium 200 in which adjacent layers are firmly integrated as a whole is obtained.

  The method for laminating the filter layer 10, the adhesive layer 20, and the prefilter layer 30 is not particularly limited. For example, the filter medium 10, the adhesive layer 20, and the prefilter layer 30 can be individually manufactured, and these three layers 10, 20, 30 can be stacked in this order and then integrated to produce the filter media 100, 200. .

  Alternatively, the filter medium 100 and 200 are manufactured by preparing a bonded body of the adhesive layer 20 and the prefilter layer 30 in advance, superimposing the filter layer 10 on the adhesive layer 20 in the bonded body, and then integrating them. Also good. The bonded body of the adhesive layer 20 and the prefilter layer 30 is integrated after, for example, the prefilter layer 30 manufactured in advance and the adhesive layer 20 manufactured independently using the airlaid method or the like are overlapped. Can be manufactured. Alternatively, the joined body may be manufactured by forming the pre-filter layer 30 on the adhesive layer 20 manufactured independently using the airlaid method or the like using a normal method. Alternatively, the bonded body may be manufactured by forming the adhesive layer 20 on the prefilter layer 30 manufactured in advance using an airlaid method or the like. In this case, for example, the fiber group is deposited on the upper surface of the prefilter layer 30 and at the same time, air is sucked from the lower surface side of the prefilter layer 30. As a result, the fiber group penetrates into the inside of the prefilter layer 30 on the air flow flowing from the upper surface to the lower surface of the prefilter layer 30 and is entangled with the fibers on the upper surface of the prefilter layer 30. The adhesive layer 20 can be formed. A step of binding the fiber groups in the adhesive layer 20 to each other using the thermal bond method with respect to the adhesive layer 20 manufactured alone or to the adhesive layer 20 formed on the prefilter layer 30. May be added. Thereby, the handleability of the adhesive layer 20 in a later step can be improved.

  Integration of filter layer 10, adhesive layer 20 and prefilter layer 30, integration of adhesive layer 20 and prefilter layer 30, integration of bonded body of adhesive layer 20 and prefilter layer 30 and filter layer 10 For example, heat or infrared rays is used to integrate the layers. Specifically, examples of the integration method include nip lamination by heat, lamination using an infrared heater, and the like. Among these, a laminate using an infrared heater is preferable from the viewpoint that it is easy to realize a long-life filter medium 100, 200 that achieves strong adhesion without crushing the thickness of each layer and is suppressed from clogging. When the breathable fiber layer 12, the adhesive layer 20, and / or the prefilter layer 30 are made of fibers having a core-sheath structure, the heating temperature of these layers is higher than the softening point of the sheath component (preferably higher than the melting point) and the core component. It is preferable to set it lower than the melting point.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not restrict | limited to a following example.

Example 1
In Example 1, an air filter medium having the laminated structure shown in FIG. 1 was produced.

As the prefilter layer, a non-woven fabric (Syntex, manufactured by Mitsui Chemicals) made of PP fibers, having an average fiber diameter of 3 μm, a thickness of 0.26 mm, and a basis weight of 40 g / m ² was used. First, an adhesive layer was formed on the prefilter layer by using the airlaid method, thereby preparing a joined body of the prefilter layer and the adhesive layer. The fibers constituting the adhesive layer were PET / PE fibers having a core-sheath structure, the core part being made of PET, and the sheath part being made of PE. The average fiber diameter of the PET / PE fibers was 30 μm. The thickness of the adhesive layer was 40 μm, and the basis weight was 5 g / m ² .

Next, a filter layer was produced. 20 parts by weight of liquid paraffin as a liquid lubricant was uniformly mixed with 100 parts by weight of PTFE fine powder (Fullon CD-123, manufactured by Asahi ICI Fluoropolymers). The resulting mixture was preformed at a pressure of 20 kg / cm ² . The obtained preform was extruded into a sheet. By passing the obtained sheet-like material between a pair of metal rolling rolls, a sheet-like molded body as a long film having a thickness of 0.2 mm was obtained. The liquid lubricant contained in the sheet-like molded body was removed by an extraction method using trichlene. This sheet-like molded body was wound around a tubular core body in a roll shape. The wound sheet-like molded body was uniaxially stretched 15 times in the longitudinal direction at 280 ° C. by a roll stretching method. Further, this was stretched 30 times in the width direction at 120 ° C., and then heat treated at 400 ° C. for 30 seconds to obtain a PTFE porous membrane having a thickness of 10 μm and an average pore diameter of 0.6 μm.

As the breathable fiber layer, a non-woven fabric (Elves T0303WDO, manufactured by Unitika Ltd.) was used. The fibers constituting the breathable fiber layer were PET / PE fibers having a core-sheath structure, the core part being made of PET and the sheath part being made of PE. The average fiber diameter of the PET / PE fibers was 20 μm. The breathable fiber layer had a thickness of 150 μm and a basis weight of 30 g / m ² .

  A filter layer was produced by integrating the PTFE porous membrane and the breathable fiber layer with an infrared laminate so as to have a three-layer structure in which the breathable fiber layer was laminated on both surfaces of the PTFE porous membrane. The heating temperature of the breathable fiber layer was 160 ° C.

  A laminated body was obtained by stacking a joined body of the prefilter layer and the adhesive layer on the filter layer so as to obtain the laminated structure shown in FIG. The laminate was integrated at 160 ° C. by infrared lamination to produce an air filter medium.

(Example 2)
In Example 2, an air filter medium having the laminated structure shown in FIG. 2 was produced.

  The same prefilter layer as in Example 1 was used. The same filter layer as in Example 1 was produced.

A second adhesive layer was formed on the prefilter layer using the airlaid method, and further, a first adhesive layer was formed on the second adhesive layer using the airlaid method. As a result, a joined body of the prefilter layer and the adhesive layer having a laminated structure of (prefilter layer / second adhesive layer / first adhesive layer) was obtained. In addition, the fiber which comprises a 1st contact bonding layer was a PET / PE fiber which has a core sheath structure, a core part is a product made from PET, and a sheath part is a product made from PE. The average fiber diameter of the PET / PE fibers was 60 μm. The thickness of the first adhesive layer was 15 μm, and the basis weight was 5 g / m ² . The fibers constituting the second adhesive layer were PET / PP fibers having a core-sheath structure, the core part being made of PET and the sheath part being made of PP. The average fiber diameter of the PET / PP fiber was 60 μm. The thickness of the second adhesive layer was 15 μm, and the basis weight was 5 g / m ² . Therefore, the adhesive layer composed of the first adhesive layer and the second adhesive layer as a whole was composed of fibers having an average fiber diameter of 60 μm, a thickness of 30 μm, and a basis weight of 10 g / m ² .

  A laminated body was obtained by superimposing the obtained joined body of the prefilter layer and the adhesive layer on the filter layer so that the laminated structure shown in FIG. 2 was obtained. The laminate was integrated by the same method as in Example 1 to produce an air filter medium.

(Example 3)
In the same manner as in Example 1, a laminate in which the filter layer was overlaid on the joined body of the prefilter layer and the adhesive layer was produced. The laminated body was integrated by a hot roll nip using a heated calendar roll to produce an air filter medium having a laminated structure shown in FIG.

(Comparative Example 1)
The same prefilter layer as in Example 1 was used. The same filter layer as in Example 1 was produced. On the prefilter layer, a styrene-butadiene rubber (SBR) hot melt adhesive was applied at a basis weight of 10 g / m ² . An air filter medium in which the prefilter layer and the filter layer were integrated with each other through the adhesive was produced by overlapping the filter layer on the surface of the prefilter layer on which the adhesive was applied.

(Comparative Example 2)
The same prefilter layer as in Example 1 was used. The same filter layer as in Example 1 was produced. A laminate was obtained by directly superimposing the filter layer on the prefilter layer. The laminate was integrated by a hot roll nip using a heated calender roll to produce an air filter medium.

(Comparative Example 3)
1 has the same laminated structure as in Example 1, except that the average fiber diameter of the fibers constituting the adhesive layer is 10 μm and the average fiber diameter of the fibers constituting the breathable fiber layer is 50 μm. An air filter medium was prepared.

(Comparative Example 4)
An air filter medium having a laminated structure similar to that of FIG. 1 is produced in the same manner as in Example 1 except that the basis weight of the adhesive layer is 30 g / m ² and the average fiber diameter of the fibers constituting the adhesive layer is 60 μm. did.

(Comparative Example 5)
An air filter medium having a laminated structure similar to that of FIG. 1 was produced in the same manner as in Example 1 except that the average fiber diameter of the fibers constituting the breathable fiber layer was 50 μm.

  In addition, the average fiber diameter of the fiber which comprises a layer was calculated | required using the optical microscope (made by Lasertec). That is, a small amount of fiber collected from the layer was observed with an optical microscope, and the fiber diameter in terms of perfect circle was measured for 30 fibers. The average fiber diameter was determined by dividing the total of the measured fiber diameters in terms of perfect circle by the number of fibers measured.

  The pressure loss and the collection efficiency of the air filter media obtained in Examples 1 to 3 and Comparative Examples 1 to 5 were measured. Further, the air filter media obtained in Examples 1 to 3 and Comparative Examples 1 to 5 were pleated, and the collection efficiency and DHC (Dust Holding Capacity) of the air filter media after pleating were measured. These measurement methods will be described below. In addition, the pleating process was performed using a pleating machine (TK-11, manufactured by Toyo Koki Co., Ltd.) with a pleat height of 20 mm.

<Pressure loss>
The air filter medium was set in a circular holder having an effective area of 100 cm ² . Gas was permeated through the set filter medium, and a pressure difference was applied between the inlet side and the outlet side. The pressure loss when the linear velocity of the gas passing through the filter medium was adjusted to 5.3 cm / second was measured with a pressure gauge (manometer).

<DHC>
The air filter medium after the pleating process was set in the same apparatus as the measurement of the pressure loss. The set filter medium was permeated with air (atmosphere) for 14 days at a linear velocity of 30 cm / sec, and the pressure loss after 14 days was measured with a manometer.

<Collection efficiency>
The air filter medium (or the air filter medium after pleating) was set in the same apparatus as the measurement of the pressure loss, and the linear velocity of the gas passing through the filter medium was adjusted to 5.3 cm / sec. Subsequently, polydispersed dioctyl phthalate (DOP) was flowed from the upstream side of the filter medium so that the concentration of DOP particles of 0.3 to 0.5 μm was about 10 ⁷ particles / L. The concentration of the DOP particles on the downstream side of the filter medium was measured with a particle counter, and the collection efficiency was determined by the following equation (1).

  The results of these measurements are shown in Table 1.

  The air filter media obtained in Examples 1 to 3 showed high collection efficiency. The air filter media obtained in Examples 1 to 3 showed high collection efficiency even after pleating. The pressure loss and DHC pressure loss of the air filter media obtained in Examples 1 to 3 were both small. In the air filter media obtained in Examples 1 to 3, the difference between the pressure loss and the DHC pressure loss was also small. Thus, in Examples 1 to 3, a long-life air filter medium having a high collection efficiency and suppressing an increase in pressure loss due to the use of the filter medium was obtained.

  When Example 1 and Example 3 were compared, the pressure loss and DHC pressure loss of the air filter medium obtained in Example 1 were smaller. The difference between the pressure loss and the DHC pressure loss was 110 Pa in Example 1 and 180 Pa in Example 3. Thus, compared with Example 3, in Example 1, the increase in the pressure loss accompanying the use of the filter medium was more effectively suppressed. Unlike Example 3, in Example 1, an infrared laminating method was employed as a method of integrating the prefilter layer and the filter layer via an adhesive layer. Therefore, compared with Example 3, in Example 1, it is thought that the clogging of the filter medium accompanying integration was suppressed more effectively.

  In Comparative Example 1, the DHC pressure loss was larger than in Examples 1 to 3, and the difference between the pressure loss and the DHC pressure loss was also large. As described above, in Comparative Example 1, an increase in pressure loss due to the use of the air filter medium could not be sufficiently suppressed. In Comparative Example 1, since the prefilter layer and the filter layer were integrated using a hot melt adhesive instead of the adhesive layer, it is considered that an air filter medium that was easily clogged with use was obtained.

  In Comparative Example 2, compared to Example 3, the pressure loss and the DHC pressure loss were large, and the difference between the pressure loss and the DHC pressure loss was also large. Thus, the filter medium obtained in Comparative Example 2 had a large pressure loss, and the increase in pressure loss accompanying the use of the filter medium was also large. In Comparative Example 2, a filter medium was produced by integrating the prefilter layer and the filter layer in a state of being directly overlapped. For this reason, a filter medium with low air permeability is obtained, and it is considered that clogging occurred between the prefilter layer and the filter layer with the use of the filter medium.

  In Comparative Examples 3 and 5, the collection efficiency after pleating was lower than in Example 1. In Comparative Examples 3 and 5, the average fiber diameter of the fibers constituting the breathable fiber layer was as large as 50 μm. For this reason, in the filter media obtained in Comparative Examples 3 and 5, the PTFE porous membrane is not sufficiently supported by the fibers constituting the breathable fiber layer, and accompanying the pleating process and the use of the filter media (DHC measurement) It is considered that a leak has occurred.

In Comparative Example 4, compared to Example 1, the pressure loss and the DHC pressure loss were large, and the difference between the pressure loss and the DHC pressure loss was also large. In Comparative Example 4, the basis weight of the adhesive layer was as large as 30 g / m ² . For this reason, in Comparative Example 4, a filter medium with low air permeability was obtained, and it is considered that clogging occurred with the use of the filter medium after pleating (DHC measurement).

  The air filter medium of the present invention can be used in various applications such as a turbine intake filter medium, a clean room air filter medium, a mask filter medium, and a filter medium used in general household appliances. The air filter medium of the present invention is particularly suitable for use as an air filter medium subjected to processing such as pleating.

DESCRIPTION OF SYMBOLS 10 Filter layer 11 PTFE porous membrane 12 Breathable fiber layer 20 Adhesive layer 21 First adhesive layer 22 Second adhesive layer 30 Pre-filter layer 100,200 Air filter medium

Claims (9)

A filter layer in which a polytetrafluoroethylene (PTFE) porous membrane and a breathable fiber layer are laminated;
A pre-filter layer laminated on one side of the filter layer;
An adhesive layer provided between the filter layer and the prefilter layer;
Including a laminate of
Both outermost layers in the filter layer are the breathable fiber layers,
The average fiber diameter of the fibers constituting the prefilter layer is 0.6 to 15 μm,
The fiber constituting the breathable fiber layer has an average fiber diameter of 10 to 30 μm,
The average fiber diameter of the fibers constituting the breathable fiber layer is larger than the average fiber diameter of the fibers constituting the prefilter layer,
The adhesive layer is a fiber layer having a basis weight of 5 to 10 g / m ² .
Air filter media.   The air filter medium according to claim 1, wherein an average fiber diameter of fibers constituting the adhesive layer is 15 to 40 μm.   The air filter medium according to claim 1 or 2, wherein the adhesive layer has a thickness of 30 to 70 µm.   The air filter medium according to any one of claims 1 to 3, wherein the adhesive layer is the outermost layer of the filter layer and includes the same material as that contained in the breathable fiber layer in contact with the adhesive layer.   The air filter medium according to any one of claims 1 to 4, wherein the adhesive layer is a fiber layer formed by an airlaid method.   The air-permeable fiber layer in the filter layer has a core-sheath structure, the core portion is made of polyethylene terephthalate (PET), and the sheath portion is made of a composite fiber made of polyethylene (PE). The air filter medium in any one of -5.   The air filter medium according to claim 6, wherein the fibers constituting the adhesive layer have a core-sheath structure, the core portion is made of PET, and the sheath portion is made of PE. The pre-filter layer is made of polypropylene (PP) fiber,
The adhesive layer consists of two layers,
Of the two layers, the first adhesive layer in contact with the filter layer is:
It has a core-sheath structure, the core part is made of PET, and the sheath part is made of PE.
Of the two layers, the second adhesive layer in contact with the prefilter layer is:
The air filter medium according to claim 6, wherein the air filter medium has a core-sheath structure, the core part is made of PET, and the sheath part is made of PP.   The air filter medium according to any one of claims 1 to 8, wherein the filter layer has a laminated structure of air permeable fiber layer / PTFE porous membrane / air permeable fiber layer.

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