High-performance air filter media and its manufacturing method

Abstract

An object of the present disclosure is to provide a filter medium for air filters that does not contain PFAS or siloxane compounds and has a high PF value and water repellency. [Solution] The air filter material according to the present disclosure is a filter material for air filters made of a wet nonwoven fabric containing glass fibers with a fiber diameter of less than 1 μm, characterized in that the wet nonwoven fabric contains a water repellent agent (excluding cases where the water repellent agent is a fiber) whose main component is a hydrocarbon-based polymer that does not contain fluorine or silicon in the molecule, and does not contain a binder resin.

Description

[Technical Field]

[0001] The present disclosure relates to a filter medium for air filters used in air filters installed in clean rooms for the semiconductor, liquid crystal, and food industries, building air conditioners, air purifiers, and the like. [Background technology]

[0002] Air filters equipped with air filter media are generally used to capture and remove submicron or micron-sized particles in the air. Air filters are classified into coarse dust filters, medium- to high-performance filters, HEPA filters, ULPA filters, etc., depending on the particle size and collection efficiency they can capture. The latter type means that the filter can capture smaller particles and has a higher collection efficiency.

[0003] Air filter media are required to have the required particle collection efficiency and low pressure loss so as not to increase the airflow energy. The PF value shown in equation 1 is an index value for collection efficiency and pressure loss, and the higher this value, the higher the collection efficiency and the lower the pressure loss, indicating a superior filter media.

[0004]

number

[0005] Furthermore, water repellency is a physical property required for air filter media. By having sufficient water repellency, it is possible to prevent the problem of water droplets blocking the pores of the filter media when condensation occurs due to temperature changes or when humid air is ventilated. In addition, in places near the sea, it is possible to prevent the deliquescence phenomenon, in which sea salt particles captured by the filter media are liquefied by the moisture in the air and then released. On the other hand, if the water repellency is low, there is a problem that sealants, hot melts, etc. used when processing the filter media into air filter units will seep in.

[0006] In order to impart water repellency to a filter medium, a method of attaching a fluorine-based water repellent and / or a silicone-based water repellent (see, for example, Patent Document 1 or Patent Document 2) is widely used.

[0007] Examples of filter media using water repellents other than fluorine-based and silicone-based include a method using synthetic paraffin (see, for example, Patent Document 3) and a method using alkyl ketene dimer (see, for example, Patent Document 4).

[0008] Furthermore, air filter material must have sufficient strength, so that it does not crack or break when processing and when using ventilation.In order to give air filter material strength, the method of making binder resin adhere is widely used, but by making binder resin adhere, form binder film, and block the pore of filter material, so that pressure loss increases, and also, by covering the surface of the thin fiber that contributes to particle collection, there is the problem that collection efficiency decreases.

[0009] As a method for imparting strength to a filtering medium for air filters without using a binder resin, a method using binder fibers can be mentioned (see, for example, Patent Document 5 or Patent Document 6). [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2-175997 [Patent Document 2] Japanese Patent Application Publication No. 9-225226 [Patent Document 3] WO97 / 04851 publication [Patent Document 4] WO02 / 016005 publication [Patent Document 5] Special Publication No. 2008-518772 [Patent Document 6] Japanese Patent Application Publication No. 2018-38983 Summary of the Invention [Problem to be solved by the invention]

[0011] However, in the technology disclosed in Patent Document 1 or Patent Document 2, the perfluoroalkyl compounds (hereinafter abbreviated as PFAS) that make up the fluorine-based water repellents are persistent and highly bioaccumulative, leading to a global movement to restrict their use. Furthermore, the siloxane compounds and their condensation products, cyclic siloxanes, that make up the silicone-based water repellents, have the problem of adhering to the surfaces of semiconductor substrates and glass substrates, resulting in reduced product yields and the occurrence of cissing. Furthermore, because cyclic siloxanes, like PFASs, are persistent and highly bioaccumulative, there is a movement to restrict their use.

[0012] Furthermore, in the techniques disclosed in Patent Document 3 and Patent Document 4, it was difficult to achieve a balance between the physical properties of the PF value and water repellency of the filter medium in either method.

[0013] As mentioned above, there is a demand for an air filter material that does not contain PFAS and siloxane compounds, but in the past, it was difficult to obtain a filter material that has both high PF value and water repellency.Therefore, the object of the present disclosure is to provide an air filter material that does not contain PFAS and siloxane compounds, and has high PF value and water repellency. [Means for solving the problem]

[0014] The present inventors have conducted intensive research to solve the above-mentioned problems, and have found that by making the wet-laid nonwoven fabric that contains glass fiber with a fiber diameter of less than 1 μm contain a water repellent agent that is mainly composed of hydrocarbon polymer that does not contain fluorine and silicon in its molecule, and by not containing binder resin, unexpectedly, the air filter material with high PF value and water repellency can be obtained, and have completed the present invention.That is, the air filter material of the present invention is characterized in that, in the air filter material that is made of the wet-laid nonwoven fabric that contains glass fiber with a fiber diameter of less than 1 μm, the wet-laid nonwoven fabric contains a water repellent agent that is mainly composed of hydrocarbon polymer that does not contain fluorine and silicon in its molecule (however, except when the water repellent agent is fiber), and does not contain binder resin.

[0015] In the air filter material according to the present invention, the wetlaid nonwoven fabric may further contain binder fibers, which can provide an air filter material with higher strength.

[0016] In the air filter medium according to the present invention, the blending ratio of the binder fibers is preferably 10 to 70 mass % based on the total mass of the fibers in the filter medium, which can increase the PF value while ensuring the strength of the filter medium.

[0017] The air filter material according to the present invention may have a configuration in which the wetlaid nonwoven fabric is reinforced with a reinforcing material, thereby further increasing the strength of the filter material as required.

[0018] The air filter material according to the present invention includes a form in which the wetlaid nonwoven fabric does not contain binder fibers and is reinforced with a reinforcing material. If the wetlaid nonwoven fabric does not contain binder fibers, the strength of the wetlaid nonwoven fabric itself may be insufficient. However, by reinforcing the wetlaid nonwoven fabric with a reinforcing material, a high PF value and strength can be ensured.

[0019] In the air filter material according to the present invention, it is preferable that the wetlaid nonwoven fabric contains glass wool fibers having an average fiber diameter of less than 1 μm and glass wool fibers having an average fiber diameter of 1 μm or more, and the blending ratio of the glass wool fibers having an average fiber diameter of less than 1 μm is higher than the blending ratio of the glass wool fibers having an average fiber diameter of 1 μm or more, thereby providing the filter material with a large surface area that contributes to particle collection.

[0020] In the air filter material according to the present invention, the hydrocarbon polymer is preferably an acrylic polymer, which makes it possible to obtain an air filter material having higher water repellency.

[0021] In the air filter material according to the present invention, it is preferable that the wetlaid nonwoven fabric further contains a surfactant, which makes it possible to obtain an air filter material having a higher PF value.

[0022] In the air filter medium according to the present invention, the solid mass ratio of the water repellent to the surfactant (water repellent / surfactant) is preferably 2 to 70 parts by mass relative to 100 parts by mass of the water repellent, thereby obtaining a filter medium with a good balance of physical properties such as PF value and water repellency.

[0023] In the air filter material according to the present invention, the wetlaid nonwoven fabric further contains one or more other fibers selected from the group consisting of natural fibers, regenerated fibers, polyolefin fibers, polyurethane fibers, and vinylon fibers, and the content of the other fibers is 30 mass% or less of the total mass of the fibers in the air filter material.

[0024] The air filter material according to the present invention includes an embodiment in which the binder fibers are one or more fibers selected from the group consisting of polyvinyl alcohol fibers, polyester fibers, and polyolefin fibers.

[0025] The method for producing an air filter material according to the present invention is characterized by comprising the steps of: forming a wet sheet from a slurry containing glass fibers with a fiber diameter of less than 1 μm by a wet papermaking method; impregnating the wet sheet with an aqueous dispersion containing a water repellent agent (excluding the case where the water repellent agent is a fiber) that is mainly composed of a hydrocarbon polymer that does not contain fluorine and silicon in its molecule, and does not contain a binder resin; and drying the wet sheet impregnated with the aqueous dispersion to obtain a dry sheet.By this production method, an air filter material can be obtained that does not contain PFAS and siloxane compounds, and has a good balance of physical properties such as PF value and water repellency.

[0026] In the method for producing an air filter medium according to the present invention, it is preferable that the slurry further contains binder fibers, which makes it possible to obtain an air filter medium having higher strength.

[0027] In the method for producing an air filter medium according to the present invention, the hydrocarbon polymer is preferably an acrylic polymer, which makes it possible to obtain an air filter medium having higher water repellency.

[0028] In the method for producing an air filter material according to the present invention, it is preferable that the aqueous dispersion further contains a surfactant, which makes it possible to obtain an air filter material having a higher PF value.

[0029] In the method for producing an air filter material according to the present invention, the dry sheet further contains one or more other fibers selected from the group consisting of natural fibers, regenerated fibers, polyolefin fibers, polyurethane fibers, and vinylon fibers, and the content of the other fibers is 30 mass% or less of the total mass of the fibers in the air filter material.

[0030] The method for producing a filter medium for air filters according to the present invention includes an embodiment in which the binder fibers are one or more fibers selected from the group consisting of polyvinyl alcohol fibers, polyester fibers, and polyolefin fibers. [Effects of the Invention]

[0031] According to the present disclosure, it is possible to obtain a filter medium for air filters that does not contain PFAS or siloxane compounds and has a high PF value and water repellency. DETAILED DESCRIPTION OF THE INVENTION

[0032] Next, the present invention will be described in detail with reference to the embodiments, but the present invention is not limited to these descriptions. Various modifications of the embodiments may be made as long as the effects of the present invention are achieved.

[0033] The air filter material according to this embodiment is made of a wet-laid nonwoven fabric containing glass fibers. Because glass fibers have high rigidity, they can maintain sufficient voids within the filter material for air passage, resulting in a high PF value. Glass wool fibers and chopped glass fibers can be used as the glass fibers. The glass wool fibers referred to here are irregular, discontinuous, wool-like glass fibers with a certain fiber diameter distribution, produced by drawing using a flame drawing method or a rotary drawing method. The fiber diameter generally ranges from about 0.1 to about 10 μm. Because of the certain distribution, the fiber diameter is generally expressed as an average fiber diameter. The fiber diameter of the glass wool fibers used in this embodiment is also an average fiber diameter. Meanwhile, chopped glass fibers are regular, linear glass fibers obtained by cutting continuous glass fibers spun from a spinneret with a predetermined diameter to a predetermined fiber length. The fiber diameter generally ranges from about 4 to about 30 μm, and the fiber length generally ranges from about 1.5 to about 25 mm. In the filter material of this embodiment, the glass wool fiber with a small diameter and an irregular shape has the effect of increasing collection efficiency and maintaining voids in the filter material. The chopped glass fiber with a large diameter and a straight line has the effect of providing the strength and rigidity required when processing and using the filter unit, but because the fiber tends to accumulate horizontally during the manufacturing of the filter material, if the blending ratio of chopped glass fiber is high, the density of the filter material tends to increase.

[0034] The wetlaid nonwoven fabric contains at least a portion of glass fibers with a fiber diameter of less than 1 μm (hereinafter referred to as submicron glass fibers). These are made of glass wool fibers. The reason for including submicron glass fibers is that they have a high surface area that contributes to particle capture. In this embodiment, the blending ratio of glass wool fibers including submicron glass fibers is preferably 5 to 90 mass%, more preferably 25 to 80 mass%, and even more preferably 45 to 70 mass%, based on the total fiber mass in the filter medium. In this embodiment, the blending ratio of submicron glass fibers is preferably 5 to 85 mass%, more preferably 20 to 75 mass%, and even more preferably 30 to 65 mass%, based on the total fiber mass in the filter medium. Furthermore, the blending ratio of chopped glass fibers is preferably 1 to 50 mass%, more preferably 3 to 30 mass%, and even more preferably 5 to 10 mass%, based on the total fiber mass in the filter medium.

[0035] In the air filter material according to this embodiment, the wetlaid nonwoven fabric preferably contains glass wool fibers having an average fiber diameter of less than 1 μm and glass wool fibers having an average fiber diameter of 1 μm or more, and the blending ratio of the glass wool fibers having an average fiber diameter of less than 1 μm is higher than the blending ratio of the glass wool fibers having an average fiber diameter of 1 μm or more. This provides the filter material with a large surface area that contributes to particle capture. The blending ratio of the glass wool fibers having an average fiber diameter of less than 1 μm is preferably 1.2 to 10 times, and more preferably 2.0 to 8.4 times, higher than the blending ratio of the glass wool fibers having an average fiber diameter of 1 μm or more.

[0036] The wetlaid nonwoven fabric preferably contains binder fibers. Addition of binder fibers can impart strength through welding, hydrogen bonding, physical entanglement, and the like. Welding and bonding includes point bonding of binder fibers to glass wool. Examples of binder fibers include polyvinyl alcohol fibers, polyester fibers, and polyolefin fibers. Among these, the use of melt-adhesive binder fibers is preferred in this embodiment. Examples of the melt-adhesive binder fibers include side-by-side binder fibers in which meltable and non-meltable portions are combined side by side; core-sheath binder fibers having a non-meltable core and a meltable sheath; and fully meltable binder fibers that melt entirely and contribute to bonding between main fibers such as glass fibers. The binder fiber content is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, and even more preferably 30 to 50% by mass, based on the total fiber mass of the fibers in the filter medium. The PF value can be increased while ensuring the strength of the filter medium. The melt adhesive binder fiber may be any one of side-by-side type binder fiber, sheath-core type binder fiber, and full-melt type binder fiber, or may be a combination of two or three types. Examples of the combination of two types include a combination of a side-by-side type binder fiber and a sheath-core type binder fiber, a combination of a side-by-side type binder fiber and a full-melt type binder fiber, or a combination of a sheath-core type binder fiber and a full-melt type binder fiber.

[0037] The melt-bonded binder fibers maintain their shape when mixed into a wet sheet, but when heated in the heat-drying process, they melt partially or entirely and bond with the main fibers or with each other. The melted binder fibers contained in the air filter material that has undergone the heat-drying process maintain their fiber shape, or although there are some interrupted portions, the fiber shape can be observed, with only dotted or linear shapes being observed. More specifically, when the fully meltable binder fibers are heated, they melt entirely and bond with the glass fibers or with each other. The melted fully meltable binder fibers may have some deformed portions such as interruptions, crushing, or bending, but the fiber shape can be observed, with only linear or dotted shapes being observed. In this embodiment, the only difference between the fully meltable binder fibers before and after the heat-drying process is that they are fibrous and have traces of their former fibrous form, so the fully meltable binder fibers before melting and the melted fully meltable binder fibers are referred to as fully meltable binder fibers. Furthermore, when the side-by-side binder fiber or the sheath-core binder fiber is heated, the meltable portion of the side-by-side binder fiber or the sheath portion of the sheath-core binder fiber melts and bonds with the glass fiber, bonds between side-by-side binder fibers, or bonds between sheath-core binder fibers. In the melted side-by-side binder fiber or the melted sheath-core binder fiber, the unmelted portion of the side-by-side binder fiber or the core portion of the sheath-core binder fiber maintains its fibrous shape. In this embodiment, since the side-by-side binder fiber or the sheath-core binder fiber is in a fibrous form both before and after the heat drying step, both the side-by-side binder fiber or the sheath-core binder fiber before melting and the melted side-by-side binder fiber or the sheath-core binder fiber are referred to as "side-by-side binder fiber or the sheath-core binder fiber." When the binder resin is heated in a heating and drying process or the like, it melts or the emulsion particles fuse together to form a film, which spreads over the entire filter medium and is distributed in a flat pattern.

[0038] In this embodiment, fibers other than binder fibers and glass fibers may be used as fibers constituting the wetlaid nonwoven fabric. Examples of such fibers include natural fibers such as wood pulp, recycled fibers such as rayon, and synthetic fibers such as polyolefin fibers, polyurethane fibers, and vinylon fibers. The blending amount of these fibers is preferably within a range that does not interfere with the effect of glass fibers in increasing the PF value. For example, the blending amount is 30% by mass or less of the total fibers, more preferably 20% by mass or less, and even more preferably 10% by mass or less.

[0039] This embodiment encompasses a form in which the wetlaid nonwoven fabric is reinforced with a reinforcing material, as long as it does not impair the effects of the present invention. For example, the wetlaid nonwoven fabric to be used as the air filter filter material may be bonded to another nonwoven fabric. The wetlaid nonwoven fabric to be used as the air filter filter material may be fused to another nonwoven fabric. By bonding or fusing with another nonwoven fabric, the strength can be increased. Examples of the other nonwoven fabric include polyester nonwoven fabric, polyolefin nonwoven fabric, etc. Even when the wetlaid nonwoven fabric contains binder fibers, the wetlaid nonwoven fabric may be reinforced with a reinforcing material. If necessary, the strength of the filter material can be further increased. Furthermore, when the wetlaid nonwoven fabric does not contain binder fibers, it is preferable that the wetlaid nonwoven fabric be reinforced with a reinforcing material. If the wetlaid nonwoven fabric does not contain binder fibers, the strength of the wetlaid nonwoven fabric itself may be insufficient. However, by reinforcing the wetlaid nonwoven fabric with a reinforcing material, a high PF value and strength can be ensured. In this specification, when indicating the blending ratio or the like in the filter medium, calculations are made based on the wet-laid nonwoven fabric, excluding other nonwoven fabrics.

[0040] The water repellent is attached to the fibers of the wetlaid nonwoven fabric and is used to impart the water repellency required for the air filter medium. The main component of the water repellent is a hydrocarbon-based polymer that does not contain fluorine or silicon in the molecule. The water repellent contains 50% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more of the hydrocarbon-based polymer that does not contain fluorine or silicon in the molecule. A hydrocarbon-based polymer is a polymer made of an organic compound with a hydrocarbon skeleton. The organic compound that constitutes the polymer may or may not contain oxygen, nitrogen, etc. Among hydrocarbon-based polymers, acrylic polymers are more preferred. An acrylic polymer is a polymer polymerized using acrylic acid esters or methacrylic acid esters as the main raw material monomer. The acrylic polymer is synthesized containing 50% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more of the raw material monomer. The ester portion of the acrylic polymer is preferably a hydrocarbon group. This hydrocarbon group may be linear or branched, may be a saturated or unsaturated hydrocarbon, and may even have an alicyclic or aromatic ring. Among these, linear ones are preferred, and linear alkyl groups are more preferred. The number of carbon atoms in the ester moiety is preferably 9 or more, more preferably 12 or more. If the number of carbon atoms is 8 or less, the water repellent treatment agent will not exhibit sufficient water repellency. Furthermore, the ionic nature of the hydrocarbon-based water repellent is preferably cationic. Since the surface of glass fiber is negatively charged, the water repellent agent is more likely to be adsorbed to the fiber surface, resulting in higher water repellency. Examples of such hydrocarbon-based water repellents include the Unidyne XF series (manufactured by Daikin Industries, Ltd.) made of acrylic polymers and the Mayshield series (manufactured by Meisei Chemical Industry Co., Ltd.) made of hydrocarbon-based polymers, and the agent may be selected from among these commercially available products.

[0041] The air filter material according to this embodiment does not contain a binder resin. While the binder resin provides strength to the air filter material, the formed coating clogs the pores of the air filter material, lowering the PF value. The binder resin is a water-soluble resin or aqueous emulsion, which distinguishes it from binder fibers. Resins mainly used as binder resins include poly(meth)acrylic ester resins, polyvinyl acetate resins, polyurethane resins, and polyvinyl alcohol. Among these, binder resins made of poly(meth)acrylic ester resins are characterized by the ester moiety having a carbon number of 8 or less (preferably 80% by mass or more, more preferably 90% by mass or more of the acrylic ester or methacrylic ester). On the other hand, water repellents made of acrylic polymers are characterized by the ester moiety having a carbon number of more than 8 (preferably 80% by mass or more, more preferably 90% by mass or more of the acrylic ester or methacrylic ester), which distinguishes them from binder resins in this respect.

[0042] The surfactant according to the present embodiment is used to reduce the density of the air filter material and improve the PF value. Since the addition of a surfactant reduces water repellency, it is preferable that the surfactant be cationic or nonionic, which contributes little to the reduction of water repellency. Examples of surfactants include primary to tertiary amine salts, quaternary ammonium salts, fatty acid esters, and aliphatic ethers.

[0043] In this embodiment, the solid mass ratio of the water repellent to the surfactant (water repellent / surfactant) is preferably 2 to 70 parts of surfactant when the water repellent is 100 parts. It is preferably 5 to 60 parts, and more preferably 10 to 50 parts. This ratio allows for a filter medium with a good balance of physical properties, namely, the PF value and water repellency, to be obtained. If the mass ratio of the surfactant is lower than 2 parts, it is difficult to contribute to an increase in the PF value. If the mass ratio of the surfactant is higher than 70 parts, sufficient water repellency may not be obtained.

[0044] In this embodiment, the solid mass content of the water repellent agent in the filter medium is preferably 0.1 to 5% relative to the entire filter medium, and more preferably 0.2 to 3%. If the content of these components is lower than 0.1%, sufficient water repellency may not be obtained. On the other hand, if the content is higher than 5%, a sufficient PF value may not be obtained.

[0045] In this embodiment, the water repellent is impregnated into a wet nonwoven fabric in the form of an aqueous dispersion, and then the fabric is dried by heating. When a surfactant is added to the wet nonwoven fabric, it is preferably added to the aqueous dispersion containing the water repellent. For heating, a multi-cylinder dryer, Yankee dryer, or hot air dryer is used in a papermaking machine, and a rotary dryer or circulation dryer is used in a handsheet machine. The heating temperature is 80 to 150°C, more preferably 100 to 140°C.

[0046] In this embodiment, additives such as a crosslinking agent and an antifoaming agent may be added as appropriate to the aqueous dispersion used for impregnation, as long as the effects of the present invention are not impaired.

[0047] In the manufacturing process of the filter material for air filter according to the present embodiment, raw material fiber is dispersed in water to obtain raw material slurry, and this is made into sheet by wet papermaking method to obtain wet sheet.When glass fiber is used as raw material fiber in large amount, the water used for dispersion and papermaking is preferably acidic, and more preferably pH 2 to 4.By dispersing and papermaking under acidic conditions, glass fiber can be easily bonded to each other, and strength can be increased. [Example]

[0048] The present invention will be described below with specific examples, but the present invention is not limited to these descriptions.In addition, "part" in example indicates the solid content mass ratio of fiber in raw material slurry, or the solid content mass ratio of components in impregnation liquid, and the total amount of all fibers in raw material slurry is 100 parts, and the binder resin in impregnation liquid is 100 parts.In addition, "%" in example indicates the solid content mass ratio of components in filter material.

[0049] Example 1 Sixty parts of glass wool fiber (B-06-F, manufactured by Unifrax Co.) with an average fiber diameter of 0.65 μm, 30 parts of glass wool fiber (B-26-R, manufactured by Unifrax Co.) with an average fiber diameter of 2.44 μm, and 10 parts of chopped glass fiber (EC-6-6-SP, manufactured by Unifrax Co.) with an average fiber diameter of 6 μm and a cut length of 6 mm were disintegrated using acidic water of pH 3.0 in a table disintegrator to obtain a raw material slurry. The raw material slurry was then paper-made to obtain a wetlaid nonwoven fabric. Furthermore, the wetlaid nonwoven fabric was impregnated with an impregnation solution prepared by mixing 100 parts of a cationic acrylic water repellent (Unidyne XF-4001, manufactured by Daikin Industries, Ltd.) mainly composed of a hydrocarbon-based polymer containing no fluorine or silicon in the molecule, and water, and dried in a rotary dryer at 130°C to obtain a fabric with a basis weight of 70 g / m. 2 The content of the impregnated component in the filter material was 2.5%.

[0050] <Example 2> The same procedure as in Example 1 was repeated except that an impregnation solution was used, which was prepared by mixing 100 parts of a cationic acrylic water repellent (Unidyne XF-4001, manufactured by Daikin Industries, Ltd.) whose main component was a hydrocarbon polymer that did not contain fluorine or silicon in the molecule, 25 parts of a cationic surfactant (Cathiogen TMP, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), and water. 2 The content of the impregnated component in the filter material was 1.7%.

[0051] Example 3 A 70 g / m2 (basis weight) PET film was prepared in the same manner as in Example 1, except that an impregnation solution was used that was prepared by mixing a slurry of 42 parts of glass wool fiber (B-06-F, manufactured by Unifrax Co.) having an average fiber diameter of 0.65 μm, 5 parts of glass wool fiber (B-26-R, manufactured by Unifrax Co.) having an average fiber diameter of 2.44 μm, 5 parts of chopped glass fiber (EC-6-6-SP, manufactured by Unifrax Co.) having an average fiber diameter of 6 μm and a cut length of 6 mm, 30 parts of fully fused binder fiber (Melty 4000, manufactured by Unitika Ltd.), and 18 parts of core-sheath binder fiber (TJ04CN, manufactured by Teijin Limited), with 100 parts of a cationic acrylic water repellent agent (Unidyne XF-4001, manufactured by Daikin Industries, Ltd.) containing a hydrocarbon polymer containing no fluorine or silicon in the molecule as the main component, and water. 2 The content of the impregnated component in the filter material was 1.3%.

[0052] Example 4 The same procedure as in Example 1 was repeated except that the slurry of disintegrated fibers described in Example 3 was used, and an impregnation solution was prepared by mixing 100 parts of a cationic acrylic water repellent agent (Unidyne XF-4001, manufactured by Daikin Industries, Ltd.) whose main component is a hydrocarbon polymer that does not contain fluorine or silicon in the molecule, 25 parts of a cationic surfactant (Cathiogen TMP, manufactured by Meisei Chemical Industry Co., Ltd.), and water. 2 The content of the impregnated component in the filter material was 0.6%.

[0053] <Example 5> A 70 g / m2 (basis weight) woven fabric was prepared in the same manner as in Example 1, except that an impregnation solution was used that was prepared by mixing a slurry of 42 parts of glass wool fiber (B-06-F, manufactured by Unifrax Co.) having an average fiber diameter of 0.65 μm, 35 parts of glass wool fiber (B-26-R, manufactured by Unifrax Co.) having an average fiber diameter of 2.44 μm, 5 parts of chopped glass fiber (EC-6-6-SP, manufactured by Unifrax Co.) having an average fiber diameter of 6 μm and a cut length of 6 mm, and 18 parts of core-sheath binder fiber (TJ04CN, manufactured by Teijin Limited), 100 parts of a cationic acrylic water repellent agent (Unidyne XF-4001, manufactured by Daikin Industries, Ltd.) mainly composed of a hydrocarbon polymer not containing fluorine or silicon in the molecule, 25 parts of a cationic surfactant (Catiogen TMP, manufactured by Meisei Chemical Industry Co., Ltd.), and water. 2 The content of the impregnated component in the filter material was 1.3%.

[0054] Example 6 22 parts of glass wool fiber (B-00-F, manufactured by Unifrax Co.) with an average fiber diameter of 0.33 μm, 5 parts of glass wool fiber (B-26-R, manufactured by Unifrax Co.) with an average fiber diameter of 2.44 μm, and 5 parts of chopped glass fiber (EC-6-6-SP, manufactured by Unifrax Co.) with an average fiber diameter of 6 μm and a cut length of 6 mm were used. A 100-ply impregnation solution was prepared by mixing 100 parts of a cationic acrylic water repellent (Unidyne XF-4001, manufactured by Daikin Industries, Ltd.) containing a hydrocarbon polymer as the main component and not containing fluorine or silicon in the molecule, 25 parts of a cationic surfactant (Catiogen TMP, manufactured by Meisei Chemical Industry Co., Ltd.), and water. The same procedure as in Example 1 was repeated except that a slurry of 5 parts of fully melted binder fiber (Melty 4000, manufactured by Unitika Ltd.) and 18 parts of core-sheath binder fiber (TJ04CN, manufactured by Teijin Ltd.) was used. 2 The content of the impregnated component in the filter material was 0.6%.

[0055] Example 7 The same procedure as in Example 1 was repeated except that the slurry of disintegrated fibers described in Example 3 was used, and an impregnation solution was prepared by mixing 100 parts of a cationic acrylic water repellent agent (Unidyne XF-4001, manufactured by Daikin Industries, Ltd.) whose main component is a hydrocarbon polymer that does not contain fluorine or silicon in the molecule, 5 parts of a cationic surfactant (Cathiogen TMP, manufactured by Meisei Chemical Industry Co., Ltd.), and water. 2 The content of the impregnated component in the filter material was 1.1%.

[0056] Example 8 The same procedure as in Example 1 was repeated except that the slurry of disintegrated fibers described in Example 3 was used, and an impregnation solution was prepared by mixing 100 parts of a cationic acrylic water repellent agent (Unidyne XF-4001, manufactured by Daikin Industries, Ltd.) whose main component is a hydrocarbon polymer that does not contain fluorine or silicon in the molecule, 67 parts of a cationic surfactant (Cathiogen TMP, manufactured by Meisei Chemical Industry Co., Ltd.), and water. 2 The content of the impregnated component in the filter material was 0.5%.

[0057] Example 9 The air filter medium obtained in Example 2 was treated with a reinforcing material having a basis weight of 20 g / m 2 The olefin spunbond nonwoven fabric (Elves T0203WDO, manufactured by Unitika Ltd.) was laminated by heat and pressure.

[0058] <Comparative Example 1> The same procedure as in Example 1 was repeated except for the omission of the impregnation step, and the basis weight was 70 g / m. 2 Thus, an air filter medium of the above formula was obtained.

[0059] <Comparative Example 2> A paper sheet with a basis weight of 70 g / m was impregnated in the same manner as in Example 1, except that an impregnation solution containing 100 parts of an acrylic binder resin (Boncoat AN-1190S, manufactured by DIC Corporation), 20 parts of a cationic acrylic water repellent agent (Unidyne XF-4001, manufactured by Daikin Industries, Ltd.) whose main component is a hydrocarbon polymer that does not contain fluorine or silicon in the molecule, and water was used.2 The content of the impregnated component in the filter material was 5.1%.

[0060] <Comparative Example 3> The same procedure as in Example 1 was carried out to impregnate a sheet of paper with a basis weight of 70 g / m, except that an impregnation liquid prepared by mixing 100 parts of a fluorine-based water repellent agent (Asahiguard AG-E060, manufactured by AGC Corporation) and water was used. 2 The content of the impregnated component in the filter material was 1.2%.

[0061] <Comparative Example 4> A 70 g / m2 spunbonded woven fabric was prepared in the same manner as in Example 1, except that the defibrated fiber slurry described in Example 3 was used and the impregnation step was omitted. 2 Thus, an air filter medium of the above formula was obtained.

[0062] <Comparative Example 5> A pulp cloth having a basis weight of 70 g / m was prepared in the same manner as in Example 1, except that the impregnation liquid used was a mixture of the pulp slurry prepared by disintegrating the fibers described in Example 3, 100 parts of an acrylic binder resin (Boncoat AN-1190S, manufactured by DIC Corporation), 20 parts of a cationic acrylic water repellent agent (Unidyne XF-4001, manufactured by Daikin Industries, Ltd.) whose main component is a hydrocarbon polymer that does not contain fluorine or silicon in the molecule, and water. 2 The content of the impregnated component in the filter material was 5.0%.

[0063] <Comparative Example 6> The same procedure as in Example 1 was carried out to impregnate a woven fabric having a basis weight of 70 g / m, except that the impregnation liquid was prepared by mixing the slurry of disintegrated fibers described in Example 3 with 100 parts of a fluorine-based water repellent (Asahiguard AG-E060, manufactured by AGC Corporation) and water. 2 The content of the impregnated component in the filter material was 0.8%.

[0064] The filter materials for air filters obtained in the examples and comparative examples were evaluated using the following methods.

[0065] <Pressure loss> The pressure loss was measured using a manometer (Manostage WO81, manufactured by Yamamoto Electric Co., Ltd.) as the differential pressure when air was passed through the filter medium for an air filter with an effective area of 100 cm 2 at a face velocity of 5.3 cm / second.

[0066] <Transmittance> The transmittance was determined from the ratio of the number of PAO particles upstream and downstream when air containing polydisperse polyalphaolefin (PAO) particles generated by a Ruskin nozzle was passed through the filter medium for an air filter with an effective area of 100 cm 2 at a face velocity of 5.3 cm / second. The upstream and downstream numbers of PAO particles were measured using a laser particle counter (KC-22B, manufactured by Lion Corporation). The target particle diameters were 0.10 - 0.15 μm and 0.30 μm.

[0067] <PF value> The PF value was calculated using the formula shown in Equation (1) from the values of the pressure loss and particle transmittance. The target particle diameters were 0.10 - 0.15 μm and 0.30 μm.

[0068] <Tensile strength> The tensile strength was measured using an autograph AGX-S (manufactured by Shimadzu Corporation) under the conditions of a test width of 1 inch, a test length of 100 mm, and a tensile speed of 15 mm / min. In principle, the maximum point of the stress-strain diagram was taken as the tensile strength, but in Example 9 where a reinforcing material was laminated, the upper yield point was taken as the tensile strength.

[0069] <Water repellency> The water repellency was measured in accordance with MIL-STD-282.

[0070] The evaluation results of the filter medium for an air filter conducted by the above method are shown in Table 1 and Table 2.

[0071]

Table 1

[0072]

Table 2

[0073] In Comparative Examples 1 and 4, no water repellent agent was added to the wetlaid nonwoven fabric, and therefore there was no water repellency. Comparing Example 1 with Comparative Example 1, Example 1 not only achieved high water repellency but also had an improved PF value. Comparing Example 3 with Comparative Example 4, Example 3 not only achieved high water repellency but also had an improved PF value.

[0074] Comparing Example 1 and Comparative Example 2, it was confirmed that the air filter material of Example 1, which contains a water repellent agent that does not contain fluorine or silicon and is impregnated with an aqueous dispersion that does not contain a binder resin, has a higher PF value and water repellency than the air filter material of Comparative Example 2 to which a binder resin is attached.

[0075] In Example 2, in contrast to Example 1, a surfactant was added to the aqueous dispersion in addition to the fluorine- and silicon-free water repellent, and it was confirmed that although the water repellency was reduced, a higher PF value could be obtained.

[0076] Comparing Examples 1 and 2 with Comparative Example 3, it was confirmed that by using a water repellent agent that does not contain fluorine or silicon according to the present invention, filter media in Examples 1 and 2 have a good balance of physical properties, such as PF value and water repellency, that are equal to or better than those obtained when a fluorine-based water repellent agent is used in Comparative Example 3.

[0077] In Examples 3 and 4, the PF value was lower than in Examples 1 and 2 due to the addition of binder fibers to the fiber slurry, but it was confirmed that the strength of the air filter medium was increased.

[0078] Comparing Examples 3 and 4 with Comparative Example 5, it was confirmed that, like the fiber slurry systems of Examples 1 and 2 to which no binder fiber was added, the air filter media of Examples 3 and 4 impregnated with the aqueous dispersion containing the fluorine- and silicon-free water repellent agent and not containing the binder resin had a higher PF value and water repellency than the air filter media of Comparative Example 5 to which the binder resin was attached.

[0079] Comparing Examples 3, 4, 7, and 8 with Comparative Example 6, it was confirmed that, like the fiber slurry systems of Examples 1 and 2 without added binder fibers, the air filter media of Examples 3, 4, 7, and 8 using water repellents that do not contain fluorine or silicon have a better balance of physical properties, including PF value, water repellency, and strength, than the air filter media of Comparative Example 6 using a fluorine-based water repellent.

[0080] Comparing Examples 2, 4, 5, and 6, it is found that increasing the amount of binder fiber added reduces the PF value and water repellency, but improves strength. Therefore, by changing the amount of binder fiber added, it is possible to adjust the balance of physical properties of the air filter medium.

[0081] Comparing Example 2 with Example 9, lamination reduced the PF value but improved the strength. Furthermore, comparing Example 4 with Example 9, the PF value and strength were similar when 48 parts of binder fiber was added and when lamination was performed without binder fiber, so selection can be made depending on the application. The claims of this application as filed are set forth below. (Appendix 1) In an air filter medium made of a wet-laid nonwoven fabric containing glass fibers with a fiber diameter of less than 1 μm, The wetlaid nonwoven fabric contains a water repellent agent mainly composed of a hydrocarbon polymer that does not contain fluorine or silicon in its molecule, and does not contain a binder resin. (Appendix 2) 2. The air filter medium according to claim 1, wherein the wetlaid nonwoven fabric further comprises binder fibers. (Appendix 3) 3. The filter material for air filters according to claim 2, wherein the blending ratio of the binder fibers is 10 to 70 mass % based on the total mass of the fibers in the filter material. (Appendix 4) 3. The air filter medium according to claim 2, wherein the wetlaid nonwoven fabric is reinforced with a reinforcing material. (Appendix 5) 2. The air filter medium according to claim 1, wherein the wetlaid nonwoven fabric does not contain binder fibers and is reinforced with a reinforcing material. (Appendix 6) The wetlaid nonwoven fabric contains glass wool fibers having an average fiber diameter of less than 1 μm and glass wool fibers having an average fiber diameter of 1 μm or more, and 2. The air filter medium according to claim 1, wherein the blending ratio of glass wool fibers with an average fiber diameter of less than 1 μm is higher than the blending ratio of glass wool fibers with an average fiber diameter of 1 μm or more. (Appendix 7) 2. The air filter material according to claim 1, wherein the hydrocarbon polymer is an acrylic polymer. (Appendix 8) 8. The air filter medium according to any one of claims 1 to 7, wherein the wetlaid nonwoven fabric further contains a surfactant. (Appendix 9) 9. The air filter medium according to claim 8, wherein the solid mass ratio of the water repellent to the surfactant (water repellent / surfactant) is 2 to 70 parts by mass per 100 parts by mass of the water repellent. (Appendix 10) A step of forming a wet sheet by forming a slurry containing glass fibers having a fiber diameter of less than 1 μm into a sheet by a wet papermaking method; a step of impregnating the wet sheet with an aqueous dispersion containing a water repellent agent mainly composed of a hydrocarbon polymer containing no fluorine or silicon in its molecule and no binder resin; and drying the wet sheet impregnated with the aqueous dispersion to obtain a dry sheet. (Appendix 11) 11. The method for producing a filter material for an air filter according to claim 10, wherein the slurry further contains binder fibers. (Appendix 12) 11. The method for producing a filter material for air filters according to claim 10, wherein the hydrocarbon polymer is an acrylic polymer. (Appendix 13) 13. The method for producing a filter medium for air filters according to any one of claims 10 to 12, wherein the aqueous dispersion further contains a surfactant.

Claims

1. In an air filter material made of a wet-laid nonwoven fabric containing glass fibers with a fiber diameter of less than 1 μm, The wetlaid nonwoven fabric contains a water repellent agent (except when the water repellent agent is a fiber) whose main component is a hydrocarbon polymer that does not contain fluorine or silicon in its molecule, and is a filter material for air filters, characterized in that it does not contain a binder resin.

2. 2. The air filter medium according to claim 1, wherein the wetlaid nonwoven fabric further comprises binder fibers.

3. 3. The filter material for air filters according to claim 2, wherein the blending ratio of the binder fibers is 10 to 70% by mass based on the total mass of the fibers in the filter material.

4. 3. The air filter medium according to claim 2, wherein the wetlaid nonwoven fabric is reinforced with a reinforcing material.

5. 2. The air filter medium according to claim 1, wherein the wetlaid nonwoven fabric does not contain binder fibers and is reinforced with a reinforcing material.

6. The wetlaid nonwoven fabric contains glass wool fibers having an average fiber diameter of less than 1 μm and glass wool fibers having an average fiber diameter of 1 μm or more, and 2. The air filter medium according to claim 1, wherein the blending ratio of glass wool fibers having an average fiber diameter of less than 1 μm is higher than the blending ratio of glass wool fibers having an average fiber diameter of 1 μm or more.

7. 2. The air filter medium according to claim 1, wherein the hydrocarbon polymer is an acrylic polymer.

8. The air filter medium according to any one of claims 1 to 7, wherein the wetlaid nonwoven fabric further contains a surfactant.

9. The air filter material according to claim 8, characterized in that the solid mass ratio of the water repellent to the surfactant (water repellent / surfactant) is 2 to 70 parts by mass relative to 100 parts by mass of the water repellent.

10. The air filter material according to claim 1, characterized in that the wetlaid nonwoven fabric further contains one or more other fibers selected from the group consisting of natural fibers, regenerated fibers, polyolefin fibers, polyurethane fibers and vinylon fibers, and the content of the other fibers is 30 mass% or less of the total fiber mass of the fibers in the air filter material.

11. 3. The air filter medium according to claim 2, wherein the binder fibers are one or more fibers selected from the group consisting of polyvinyl alcohol fibers, polyester fibers, and polyolefin fibers.

12. forming a wet sheet by forming a slurry containing glass fibers having a fiber diameter of less than 1 μm into a sheet by a wet papermaking method; impregnating the wet sheet with an aqueous dispersion containing a water repellent agent mainly composed of a hydrocarbon polymer containing no fluorine or silicon in its molecule (excluding cases where the water repellent agent is a fiber) and no binder resin; and drying the wet sheet impregnated with the aqueous dispersion to obtain a dry sheet.

13. 13. The method for producing a filter medium for an air filter according to claim 12, wherein the slurry further contains binder fibers.

14. 13. The method for producing a filter material for an air filter according to claim 12, wherein the hydrocarbon polymer is an acrylic polymer.

15. The method for producing a filter medium for air filters according to any one of claims 12 to 14, wherein the aqueous dispersion further contains a surfactant.

16. The method for producing a filter material for air filters according to claim 12, characterized in that the dry sheet further comprises one or more other fibers selected from the group consisting of natural fibers, recycled fibers, polyolefin fibers, polyurethane fibers and vinylon fibers, and the content of the other fibers is 30 mass% or less relative to the total mass of the fibers in the filter material for air filters.

17. 14. The method for producing a filter material for an air filter according to claim 13, wherein the binder fiber is one or more fibers selected from the group consisting of polyvinyl alcohol fiber, polyester fiber, and polyolefin fiber.

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