WO2024122160A1 - Filter material for air filter, and method for manufacturing same - Google Patents

Filter material for air filter, and method for manufacturing same Download PDF

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Publication number
WO2024122160A1
WO2024122160A1 PCT/JP2023/034051 JP2023034051W WO2024122160A1 WO 2024122160 A1 WO2024122160 A1 WO 2024122160A1 JP 2023034051 W JP2023034051 W JP 2023034051W WO 2024122160 A1 WO2024122160 A1 WO 2024122160A1
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Prior art keywords
fibers
filter medium
beaten
biodegradable
ketene dimer
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PCT/JP2023/034051
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French (fr)
Japanese (ja)
Inventor
祐希 山▲崎▼
栄子 目黒
正 佐藤
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北越コーポレーション株式会社
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Publication of WO2024122160A1 publication Critical patent/WO2024122160A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/14—Other self-supporting filtering material ; Other filtering material
    • B01D39/16—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • D21H11/16—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only modified by a particular after-treatment
    • D21H11/20—Chemically or biochemically modified fibres
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
    • D21H27/08—Filter paper

Definitions

  • This disclosure relates to air filter media used in various fields such as factory and building air conditioning, automobile passenger compartments, air conditioners, air purifiers, and personal protective equipment, and in particular to air filter media that have a small environmental impact and little degradation in filtering performance during use.
  • Glass fiber filter media and meltblown nonwoven fabric filter media are mainly used as medium to high performance filter media for air filters used in building air conditioning, etc.
  • Glass fiber filter media is non-flammable, so it is disposed of in landfills as industrial waste after use. This places a large burden on the environment when it is disposed of.
  • meltblown nonwoven fabric filter media mainly uses non-renewable and finite fossil resources (such as PP) as raw materials, and when incinerated, it emits a large amount of carbon dioxide over its entire life cycle. Furthermore, if it leaks into the environment after use, it will not decompose and will remain in the environment. For these reasons, there is a demand for filter media that contain renewable materials, have a small environmental impact, and are biodegradable.
  • filter media containing fibrillated lyocell fibers, biodegradable fibers, and regenerated or semi-synthetic fibers have been proposed (see Patent Document 1 or Patent Document 2).
  • cellulosic fibers such as lyocell fibers have high hygroscopic and water-absorbent properties, and therefore when used in a high-humidity environment or when air currents or dust containing moisture pass through, the fibers swell and the filter media structure changes, resulting in a problem of a decrease in the filtering performance of the air filter media, for example, a decrease in the PF value.
  • the PF value is defined by the formula 1, and the higher the PF value, the higher the dust particle collection efficiency, the lower the pressure loss, and the higher the filtering performance of the filter media.
  • transmittance [%] 100-collection efficiency [%].
  • the objective of this disclosure is to provide a filter media for air filters that contains renewable materials, is biodegradable, and has sufficient water repellency.
  • the air filter medium according to the present invention is a filter medium made of a wet nonwoven fabric, characterized in that the fibers constituting the filter medium include beaten fibers and unbeaten fibers, the beaten fibers are fibrillated lyocell fibers, the unbeaten fibers are biodegradable fibers, and the filter medium includes an alkyl ketene dimer.
  • the content of the alkyl ketene dimer in the entire filter medium is preferably in the range of 0.05 to 2.0% by mass. This makes it possible to obtain a filter medium with sufficient water repellency and a high PF value.
  • the biodegradable fiber is at least one selected from the group consisting of regenerated cellulose fiber, natural cellulose fiber, and polylactic acid-based fiber. This makes it possible to obtain a filter medium with a high PF value and biodegradability.
  • the air filter medium of the present invention may contain a biodegradable binder. This makes it possible to obtain a filter medium that is biodegradable and has sufficient strength and rigidity for processing and use of the filter.
  • the biodegradable binder may be polyvinyl alcohol and/or polylactic acid. This makes it possible to obtain a filter medium with sufficient strength and stiffness without significantly decreasing the PF value.
  • the alkyl ketene dimer is not covered with a continuous film of the biodegradable binder. This makes it possible to obtain a filter medium that has sufficient strength and rigidity while retaining water repellency.
  • the method for producing a filter medium for air filters according to the present invention is characterized by comprising a papermaking process in which a raw material slurry in which beaten fibers and non-beaten fibers are dispersed in water is made into a sheet by a wet papermaking method to form a wet sheet, a process in which an alkyl ketene dimer is applied to the wet sheet, and a drying process in which the wet sheet to which the alkyl ketene dimer has been applied is thermally dried to form a dry sheet.
  • This method makes it possible to obtain a filter medium with sufficient water repellency and a high PF value.
  • a binder may be dispersed in the raw material slurry together with the fibers. This makes it possible to obtain a filter medium with sufficient strength and rigidity without impairing the effect of the alkyl ketene dimer in improving water repellency and PF value.
  • the present disclosure makes it possible to obtain a filter medium that has a small environmental impact and exhibits little deterioration in filtering performance during use.
  • a filter medium for air filters that contains renewable materials, is biodegradable, and has sufficient water repellency to prevent moisture absorption by cellulosic fibers, including fibrillated lyocell fibers.
  • the lyocell fiber in this embodiment is a regenerated cellulose fiber spun by an organic solvent spinning method using N-methylmorpholine N-oxide as a solvent.
  • organic solvent spinning method cellulose is dissolved in an organic solvent as it is and spun, so there is little molecular breakage, the average degree of polymerization is higher than other regenerated cellulose fibers, the fiber has high rigidity, and the cross-sectional shape of the fiber is close to circular. This rigidity and cross-sectional shape make it easier to maintain the voids in the filter medium.
  • the fibrillated lyocell fiber after beating also maintains the rigidity and cross-sectional shape, making it easier to maintain the voids in the filter medium.
  • fibrillated by beating the surface area of the fiber that contributes to particle collection increases, increasing the collection efficiency, and the fibers become more entangled, increasing the tensile strength of the filter medium.
  • the beaten fibers in this embodiment are fibrillated lyocell fibers, and the amount of beaten fibers is preferably 2 to 30 parts, more preferably 3 to 20 parts, and even more preferably 5 to 15 parts, of 100 parts of the total of the beaten fibers, unbeaten fibers, and binder that make up the filter medium. If the amount is less than 2 parts, the surface area of the fibers that contributes to particle capture is insufficient, making it difficult to achieve sufficient capture efficiency. On the other hand, if the amount exceeds 30 parts, the fibers become too entangled and block the voids, resulting in a large increase in pressure loss compared to the increase in capture efficiency, and a decrease in the PF value.
  • a beating machine or disintegrator such as a Niagara beater, PFI mill, single disc refiner, double disc refiner, or deflaker can be used.
  • a beating machine or disintegrator such as a Niagara beater, PFI mill, single disc refiner, double disc refiner, or deflaker.
  • the length-weighted average fiber length of the fibrillated lyocell fibers used in the present invention is preferably 0.6 mm or more, more preferably 0.8 to 3 mm, and even more preferably 1 to 2 mm.
  • the length-weighted average fiber length of fibrillated lyocell fibers was measured in accordance with ISO16065-2:2014 "Determination of fiber length by automated optical analysis - Part 2: Unpolarized light method.”
  • the lyocell fiber undergoes fibrillation by beating, resulting in a thinner fiber diameter. If the fiber diameter is too thin, the fiber is more likely to be cut, resulting in the aforementioned problem of shortening the fiber length. On the other hand, if the fiber diameter is too thick, the surface area of the fiber that contributes to particle collection is insufficient.
  • the average fiber diameter of the fibrillated lyocell fiber used in this embodiment is preferably 0.3 ⁇ m or more, more preferably 0.4 to 1.5 ⁇ m, and even more preferably 0.5 to 1.0 ⁇ m.
  • the average fiber diameter of the fibrillated lyocell in this embodiment was calculated using the formula 2 from the specific surface area measured by the BET multipoint method using nitrogen.
  • the fiber density of Lyocell is assumed to be 1.5 g/ cm3 .
  • the non-beaten fibers in this embodiment are biodegradable fibers that have not been beaten, have not been fibrillated, or have a slightly fuzzy surface.
  • biodegradable fibers include regenerated cellulose fibers, natural cellulose fibers, polylactic acid-based fibers, polybutylene succinate fibers, and polyhydroxyalkanoate fibers.
  • the fibers do not melt during thermal drying and the molten fibers can be prevented from blocking the pores of the filter medium, thereby preventing a decrease in the PF value, it is preferable to use at least one type selected from the group consisting of regenerated cellulose fibers, natural cellulose fibers, and polylactic acid-based fibers.
  • Non-beaten fibers of different types and/or different fiber diameters may be mixed and used.
  • the amount of unbeaten fibers is preferably 50 to 98 parts, more preferably 60 to 95 parts, and even more preferably 70 to 90 parts, of 100 parts of the total of beaten fibers, unbeaten fibers, and binders that make up the filter medium. If the amount of unbeaten fibers is less than 50 parts, the amount of beaten fibers and/or binder will be high, resulting in a low PF value. On the other hand, if the amount of unbeaten fibers exceeds 98 parts, sufficient collection efficiency and/or strength and stiffness will not be obtained.
  • Regenerated cellulose fibers are made from cellulose, such as viscose rayon fibers spun using the viscose method and lyocell fibers spun using the organic solvent spinning method. These are renewable materials made from wood pulp, and are biodegradable in soil burials and in the ocean.
  • Natural cellulose fibers are fibers that are primarily made from cellulose extracted from plants, and include wood pulp, cotton linter pulp, hemp pulp, kenaf pulp, and mercerized pulp obtained by treating wood pulp with alkali. These are renewable materials made from plants and are biodegradable when buried in the soil.
  • Polylactic acid fiber is a fiber spun from polylactic acid, which is polymerized from lactic acid obtained by saccharification and fermentation of biomass-derived starch as a raw material, and is biodegradable when buried in soil. Unlike cellulose fiber, polylactic acid fiber has thermoplasticity, so it can be used to give thermoformability to filter media.
  • main fibers made of normal polylactic acid with a melting point of 170°C or higher binder fibers that partially use polylactic acid whose melting point has been lowered to less than 170°C by modifying the molecular structure are also used as polylactic acid main fibers.
  • polylactic acid main fibers are used as unbeaten fibers
  • polylactic acid binder fibers are used as a binder, which will be described later.
  • the non-beaten fibers preferably have an average fiber diameter of 5 ⁇ m or more, more preferably 6 to 50 ⁇ m, and even more preferably 7 to 40 ⁇ m. If the average fiber diameter is smaller than 5 ⁇ m, it becomes difficult to maintain the voids necessary to uniformly distribute the beaten fibers, which may cause an increase in pressure loss. On the other hand, if the average fiber diameter exceeds 50 ⁇ m, the difference in fiber diameter from the beaten fibers is large, which may cause a large variation in the pore size of the filter medium and a decrease in collection efficiency.
  • the alkyl ketene dimer in this embodiment is a dimer obtained by reacting naturally derived fatty acids (e.g. palmitic acid with 16 carbon atoms or stearic acid with 18 carbon atoms) via acid chloride. It is widely used as a sizing agent in paper to prevent ink from penetrating. It is also biodegradable, and its use as a water-resistant agent for biodegradable materials is being considered (see, for example, Non-Patent Document 1). In this embodiment, it is used to impart sufficient water repellency to the fibers that make up the filter medium and to prevent a decrease in the filter performance during use of the filter medium.
  • naturally derived fatty acids e.g. palmitic acid with 16 carbon atoms or stearic acid with 18 carbon atoms
  • acid chloride e.g. palmitic acid with 16 carbon atoms or stearic acid with 18 carbon atoms
  • It is widely used as a sizing agent in paper to prevent ink from pe
  • the content of alkyl ketene dimer in the entire filter medium is preferably 0.05 to 2.0 mass%, more preferably 0.1 to 1.8 mass%, and particularly preferably 0.6 to 1.7 mass%. If the content is less than 0.05 mass%, sufficient water repellency (e.g., 100 mm water column height) may not be obtained. On the other hand, if the content is 0.05 mass% or more, sufficient water repellency (e.g., 100 mm water column height) can be obtained, and if the content is 0.1 mass% or more, even higher water repellency (e.g., 200 mm water column height) can be obtained. If the alkyl ketene dimer content exceeds 2.0 mass%, the PF value may decrease.
  • the PF value of the filter medium can be increased by adjusting the content of alkyl ketene dimer in the entire filter medium to an appropriate range.
  • the mechanism by which this PF value is increased is unclear, it is presumed that when an appropriate amount of alkyl ketene dimer is attached to the surface of fibrillated lyocell fibers, the PF value is increased because the collection efficiency is increased by preventing the fibers from agglomerating and increasing the surface area of the fibers, and the pressure loss is reduced by expanding the gaps between the fibers.
  • a biodegradable binder may be contained in the filter medium for the purpose of improving strength and stiffness.
  • the biodegradable binder for example, polyvinyl alcohol, polylactic acid, or both polyvinyl alcohol and polylactic acid can be used.
  • Polyvinyl alcohol is biodegradable and bonds fibers together, and is either fibrous or powdery, which can be dispersed in water together with beaten fibers and non-beaten fibers to form a raw material slurry, or can be mixed with an alkyl ketene dimer to form an aqueous solution or aqueous dispersion that can be attached by a method such as impregnation or coating.
  • Polylactic acid is the polylactic acid binder fiber described above, which bonds fibers together when heated above its melting point. It is more preferable that the biodegradable binder is in powder form. It is uniformly dispersed and point-bonded to the fibers, so that high strength and stiffness can be obtained without significantly decreasing the PF value. It is particularly preferable that the powdered binder is polyvinyl alcohol. Even higher strength and stiffness can be obtained. On the other hand, biodegradable binders in the form of an aqueous solution or dispersion may form a continuous film that covers the fibers throughout the entire filter medium, lowering the PF value, so care must be taken not to apply too much.
  • the amount of the biodegradable binder is preferably 0.5 to 20 parts, and more preferably 1 to 15 parts, of 100 parts of the total of the fibers and binder that make up the filter medium. If the amount is less than 0.5 parts, there is a risk that sufficient improvement in strength and stiffness will not be obtained, and if it exceeds 20 parts, there is a risk that the PF value will decrease.
  • additives such as antifoaming agents and dispersants can be appropriately added to the filter medium as long as they do not impede the effects of the present invention.
  • the method for producing the filter medium in this embodiment uses a wet papermaking method. That is, the fibers that make up the filter medium are dispersed in water using a dispersing machine such as a pulper, the resulting raw material slurry is deposited on a wire and dehydrated to form a wet sheet, and the resulting wet sheet is impregnated with an alkyl ketene dimer by a method such as impregnation or coating, and dried using a dryer such as a hot air dryer or cylinder dryer to obtain the filter medium as a dry sheet. If an alkyl ketene dimer is imparted to the dried sheet, the effect of improving the PF value by the alkyl ketene dimer cannot be fully obtained.
  • a dispersing machine such as a pulper
  • the resulting raw material slurry is deposited on a wire and dehydrated to form a wet sheet
  • the resulting wet sheet is impregnated with an alkyl ketene dimer by a
  • the biodegradable binder in the raw material slurry together with the fibers that make up the filter medium in the production using the above-mentioned wet papermaking method it is preferable to disperse the biodegradable binder in the raw material slurry together with the fibers that make up the filter medium in the production using the above-mentioned wet papermaking method. If the biodegradable binder in the form of an aqueous solution or aqueous dispersion is mixed with the alkyl ketene dimer and applied simultaneously by a method such as impregnation or coating, the alkyl ketene dimer will be covered with a continuous film of the biodegradable binder, and there is a risk that sufficient water repellency will not be obtained. It is preferable to disperse the biodegradable binder in the raw material slurry together with the fibers that make up the filter medium to form a wet sheet, and then apply the alkyl ketene dimer to the wet sheet.
  • additives such as antifoaming agents and dispersants can be added to the raw material slurry as appropriate, as long as they do not impede the effects of the present invention.
  • the basis weight of the filter medium in this embodiment is not particularly limited, but is preferably 25 to 350 g/m 2 , more preferably 50 to 250 g/m 2 , and even more preferably 70 to 150 g/m 2 . If the basis weight is less than 25 g/m 2 , sufficient tensile strength and/or Gurley stiffness may not be obtained. On the other hand, if the basis weight is more than 350 g/m 2 , the area of the filter medium that can be accommodated in the filter unit may be insufficient.
  • the PF value of the filter medium in this embodiment is not particularly limited, but is preferably 4.5 or more, more preferably 6.0 or more, and even more preferably 7.0 or more. This results in a filter medium with a good balance between pressure loss and collection efficiency.
  • the tensile strength of the filter medium in this embodiment varies depending on the application and post-processing method, and is not particularly limited, but is preferably 0.40 kN/m or more, and more preferably 0.45 kN/m or more. A tensile strength of 0.40 kN/m or more can be used for many applications.
  • the Gurley stiffness of the filter medium in this embodiment differs depending on the application and post-processing method, and is not particularly limited, but is preferably 7.0 mN or more, and more preferably 10.0 mN or more.
  • a Gurley stiffness of 7.0 mN can be used for many applications.
  • Example 1 14 parts of fibrillated lyocell fiber (average fiber diameter 0.8 ⁇ m, length-weighted average fiber length 1.1 mm) obtained by beating lyocell fiber (manufactured by Lenzing AG) as beaten fiber, and 86 parts of regenerated cellulose fiber lyocell fiber (manufactured by Lenzing AG, average fiber diameter 12 ⁇ m, average fiber length 4 mm) as non-beaten fiber were added with tap water so that the slurry concentration was 0.5 mass%, and disintegrated using a mixer to obtain a raw material slurry. Next, the raw material slurry obtained using a hand-made papermaking device was made into a wet sheet.
  • the obtained wet sheet was impregnated with a water dilution of alkyl ketene dimer (SE2360, manufactured by Seiko PMC Co., Ltd.) so that the alkyl ketene dimer content in the entire filter material was 0.01 mass% in solid content, and dried using a rotary dryer at 130 ° C. to obtain a filter material for air filters with a basis weight of 100 g / m 2 as a dried sheet.
  • alkyl ketene dimer SE2360, manufactured by Seiko PMC Co., Ltd.
  • Example 13 Use 86 parts of mercerized pulp (Porosenia, manufactured by Rayonier Inc., average fiber diameter 34 ⁇ m, average fiber length 2.6 mm) as natural cellulose fiber as non-beaten fiber, and impregnate so that alkyl ketene dimer content is 1.0 mass% in solid content, and obtain air filter material with basis weight of 101g/ m2 by the same method as in Example 1.
  • mercerized pulp Porosenia, manufactured by Rayonier Inc., average fiber diameter 34 ⁇ m, average fiber length 2.6 mm
  • Example 14 As non-beaten fiber, use 76 parts of Lyocell fiber (manufactured by Lenzing AG, average fiber diameter 12 ⁇ m, average fiber length 4 mm) and 10 parts of polylactic acid-based fiber (PL01, manufactured by Unitika Co., Ltd., average fiber diameter 13 ⁇ m, average fiber length 5 mm, melting point 170 ° C.), but use the same method as in Example 13 to obtain air filter material with basis weight of 101 g / m 2 .
  • Lyocell fiber manufactured by Lenzing AG, average fiber diameter 12 ⁇ m, average fiber length 4 mm
  • PL01 manufactured by Unitika Co., Ltd., average fiber diameter 13 ⁇ m, average fiber length 5 mm, melting point 170 ° C.
  • Example 15 Use 84 parts of Lyocell fiber (manufactured by Lenzing AG, average fiber diameter 12 ⁇ m, average fiber length 4 mm) as non-beaten fiber, and 2 parts of polyvinyl alcohol powder (Poval K-177, manufactured by Denka Co., Ltd.) as binder to obtain raw material slurry, and obtain air filter material with basis weight of 101 g/ m2 by the same method as in Example 13.
  • Lyocell fiber manufactured by Lenzing AG, average fiber diameter 12 ⁇ m, average fiber length 4 mm
  • polyvinyl alcohol powder Polyvinyl alcohol powder
  • Example 16 As non-beaten fiber, 76 parts of Lyocell fiber (manufactured by Lenzing AG, average fiber diameter 12 ⁇ m, average fiber length 4 mm) and as binder, 10 parts of core-sheath type polylactic acid binder fiber (PL80, manufactured by Unitika Co., Ltd., average fiber diameter 15 ⁇ m, average fiber length 5 mm, core melting point 170 ° C, sheath melting point 130 ° C) are used to obtain raw material slurry, and by the same method as in Example 13, obtain air filter material with basis weight of 101 g / m 2 .
  • Lyocell fiber manufactured by Lenzing AG, average fiber diameter 12 ⁇ m, average fiber length 4 mm
  • core-sheath type polylactic acid binder fiber PL80, manufactured by Unitika Co., Ltd., average fiber diameter 15 ⁇ m, average fiber length 5 mm, core melting point 170 ° C, sheath melting point 130 ° C
  • Example 17 The aqueous solution of polyvinyl alcohol (Poval 28-98, manufactured by Kuraray Co., Ltd.) and alkyl ketene dimer (SE2360, manufactured by Seiko PMC Co., Ltd.) are mixed to form a water dilution, so that the polyvinyl alcohol content of the entire filter medium is 2.0 mass% in solid content, and the alkyl ketene dimer content is 1.0 mass% in solid content. Except for this, the same method as in Example 1 is used to obtain an air filter medium with a basis weight of 103 g/ m2 .
  • the air filter media obtained in the examples and comparative examples were evaluated using the methods described below.
  • Basis weight was measured according to JIS P 8124:2011 "Paper and paperboard -- Determination of basis weight”.
  • ⁇ Thickness and density> The thickness and density were measured in accordance with JIS P 8118:1998 "Paper and paperboard -- Test method for thickness and density” using a measurement pressure of 50 kPa.
  • the pressure loss was measured as the differential pressure when air was passed through an air filter medium having an effective area of 100 cm2 at a face velocity of 5.3 cm/sec using a manometer (Manometer Gauge WO81, manufactured by Yamamoto Electric Works, Ltd.).
  • the transmittance was calculated from the ratio of the number of particles upstream and downstream when air containing polydisperse polyalphaolefin (PAO) particles generated by a Laskin nozzle was blown through an air filter medium with an effective area of 100 cm2 at a surface velocity of 5.3 cm/sec, and the number of PAO particles upstream and downstream was measured using a laser particle counter (KC-22B, manufactured by Rion Co., Ltd.).
  • the target particle size was 0.3 ⁇ m
  • the transmittance was calculated as the geometric mean value of the transmittance of 0.2 to 0.3 ⁇ m and 0.3 to 0.4 ⁇ m.
  • PF value> The PF value was calculated from the pressure loss and the transmittance using the formula shown in Equation 1.
  • Water repellency was measured according to MIL-STD-282.
  • Gurley stiffness was measured according to JAPAN TAPPI No. 40:2000 "Paper and paperboard -- Test method for stiffness by bending under load -- Gurley method.”
  • Examples 1 to 12 in Table 1 and Comparative Example 1 in Table 2 show that by setting the alkyl ketene dimer content to 0.05% by mass or more, air filter media with sufficient water repellency at a water column height of 100 mm or more can be obtained, and by setting it to 0.1% by mass or more, even higher water repellency at a water column height of 200 mm or more can be obtained.
  • Example 6 in Table 1 and Examples 13 and 14 in Table 2 show that by using regenerated cellulose fiber, natural cellulose fiber and/or polylactic acid-based fiber as the non-beaten fiber, sufficient water repellency (water column height of 100 mm or more), PF value (4.5 or more), tensile strength (0.4 kN/m or more) and Gurley stiffness (7.0 mN or more) were obtained.
  • Example 6 in Table 1 and Examples 15 and 16 in Table 2 show that high tensile strength and Gurley stiffness were obtained by using a binder.
  • Example 6 in Table 1 and Comparative Example 2 in Table 2 show that adding alkyl ketene dimer resulted in higher water repellency than when a paraffin wax water repellent was added.
  • the air filter medium of the present invention can be used as an air filter medium for use in a variety of fields, including factory and building air conditioning, automobile passenger compartments, air conditioners, air purifiers, and personal protective equipment.
  • composition includes a plurality of such compositions, as well as a single composition.

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Abstract

The purpose of the present disclosure is to provide a filter material for an air filter, the filter material containing a renewable material, having biodegradability, and further having sufficient water repellency. According to the present disclosure, the filter material for an air filter comprises a wet nonwoven fabric and is characterized in that fibers constituting the filter material include beaten fibers and non-beaten fibers, the beaten fibers are fibrillated Lyocell fibers, the non-beaten fibers are biodegradable fibers, and the filter material includes an alkyl ketene dimer.

Description

エアフィルタ用濾材及びその製造方法Air filter material and its manufacturing method
　本開示は、工場及びビルの空調、自動車客室、エアコン、空気清浄機、個人用保保護具などの種々の分野で使用されるエアフィルタ用濾材に関し、特に、環境負荷が小さく、且つ使用時の濾過性能の低下が小さいエアフィルタ用濾材に関する。 This disclosure relates to air filter media used in various fields such as factory and building air conditioning, automobile passenger compartments, air conditioners, air purifiers, and personal protective equipment, and in particular to air filter media that have a small environmental impact and little degradation in filtering performance during use.
　ビル空調等に使用されるエアフィルタ用の中・高性能濾材としては、ガラス繊維濾材及びメルトブローン不織布濾材が主に使用される。ガラス繊維濾材は、不燃性であるため使用後は産業廃棄物として埋め立て処分される。このため、廃棄時の環境負荷が大きい。一方でメルトブローン不織布濾材は、原料として再生不可能で有限な化石資源（ＰＰ等）を主に使用しており、焼却処分された場合のライフサイクル全体での二酸化炭素排出量が大きい。又、使用後に環境に流出した場合、分解されず環境中に留まり続ける。以上の理由により、環境負荷が小さい、再生可能材料を含み、且つ生分解性を有する濾材が望まれている。 Glass fiber filter media and meltblown nonwoven fabric filter media are mainly used as medium to high performance filter media for air filters used in building air conditioning, etc. Glass fiber filter media is non-flammable, so it is disposed of in landfills as industrial waste after use. This places a large burden on the environment when it is disposed of. On the other hand, meltblown nonwoven fabric filter media mainly uses non-renewable and finite fossil resources (such as PP) as raw materials, and when incinerated, it emits a large amount of carbon dioxide over its entire life cycle. Furthermore, if it leaks into the environment after use, it will not decompose and will remain in the environment. For these reasons, there is a demand for filter media that contain renewable materials, have a small environmental impact, and are biodegradable.
　これら問題を解決するために、フィブリル化リヨセル繊維、生分解性繊維、及び再生繊維又は半合成繊維を含有する濾材が提案されている（特許文献１又は特許文献２を参照。）。しかしながら、リヨセル繊維などのセルロース系繊維は吸湿性及び吸水性が高いため、高湿度の環境での使用や、水分を含む気流やダストが通過した場合に、繊維の膨潤や濾材構造の変化を引き起こし、エアフィルタ用濾材の濾過性能の低下、例えば、ＰＦ値の低下を引き起こす問題がある。尚、ＰＦ値は数１の式により定義され、このＰＦ値が高いほど、ダスト粒子の捕集効率が高く、且つ圧力損失が低い、濾過性能が高い濾材であることを意味する。 In order to solve these problems, filter media containing fibrillated lyocell fibers, biodegradable fibers, and regenerated or semi-synthetic fibers have been proposed (see Patent Document 1 or Patent Document 2). However, cellulosic fibers such as lyocell fibers have high hygroscopic and water-absorbent properties, and therefore when used in a high-humidity environment or when air currents or dust containing moisture pass through, the fibers swell and the filter media structure changes, resulting in a problem of a decrease in the filtering performance of the air filter media, for example, a decrease in the PF value. The PF value is defined by the formula 1, and the higher the PF value, the higher the dust particle collection efficiency, the lower the pressure loss, and the higher the filtering performance of the filter media.
Figure JPOXMLDOC01-appb-M000001
 ここで、透過率［％］＝１００－捕集効率［％］である。
Figure JPOXMLDOC01-appb-M000001
 Here, transmittance [%]=100-collection efficiency [%].
　前記の問題を解決するためには、濾材に撥水性を付与する方法が有効であり、エアフィルタ用濾材に撥水性を付与する方法としては、フッ素系撥水剤を用いる方法が広く用いられている（例えば、特許文献３又は特許文献４を参照。）。しかしながら、フッ素系撥水剤を構成するパーフルオロアルキル化合物は、難分解性で且つ生物蓄積性が高いため、世界的にその使用を規制する動きがあり、本発明の目的には適さない。 In order to solve the above problems, it is effective to provide the filter medium with water repellency, and a method using a fluorine-based water repellent is widely used as a method for providing water repellency to filter medium for air filters (see, for example, Patent Document 3 or Patent Document 4). However, the perfluoroalkyl compounds that make up the fluorine-based water repellent are persistent and highly bioaccumulative, and there are global moves to restrict their use, making them unsuitable for the purpose of the present invention.
特開２００６－１６７６５９号公報JP 2006-167659 A 特開２００６－３２６４７０号公報JP 2006-326470 A 特開２００１－７９３１８号公報JP 2001-79318 A 特開２０１４－９８０８２号公報JP 2014-98082 A
　前記の通り、環境負荷が小さく、且つ使用時の濾過性能の低下が小さい濾材が求められているが、従来の技術では、これらの特性を兼ね備えた濾材を得ることが難しかった。従って、本開示の課題は、再生可能材料を含み、且つ生分解性を有し、更には十分な撥水性を有するエアフィルタ用濾材を提供することである。 As mentioned above, there is a demand for filter media that has a small environmental impact and that experience little degradation in filtering performance during use, but with conventional technology, it has been difficult to obtain filter media that combines these characteristics. Therefore, the objective of this disclosure is to provide a filter media for air filters that contains renewable materials, is biodegradable, and has sufficient water repellency.
　本発明に係るエアフィルタ用濾材は、湿式不織布からなる濾材であり、前記濾材を構成する繊維が、叩解繊維と非叩解繊維とを含み、前記叩解繊維がフィブリル化リヨセル繊維であり、前記非叩解繊維が生分解性繊維であり、且つ前記濾材がアルキルケテンダイマーを含むことを特徴とする。このような構成によれば、環境負荷が小さく、且つ使用時の濾過性能の低下が小さい濾材を得ることができる。 The air filter medium according to the present invention is a filter medium made of a wet nonwoven fabric, characterized in that the fibers constituting the filter medium include beaten fibers and unbeaten fibers, the beaten fibers are fibrillated lyocell fibers, the unbeaten fibers are biodegradable fibers, and the filter medium includes an alkyl ketene dimer. With this configuration, it is possible to obtain a filter medium that has a small environmental impact and that exhibits little deterioration in filtering performance during use.
　本発明に係るエアフィルタ用濾材では、前記アルキルケテンダイマーの濾材全体に対する含有量が０．０５～２．０質量％の範囲にあることが好ましい。これにより、十分な撥水性と高いＰＦ値を有する濾材を得ることができる。 In the air filter medium of the present invention, the content of the alkyl ketene dimer in the entire filter medium is preferably in the range of 0.05 to 2.0% by mass. This makes it possible to obtain a filter medium with sufficient water repellency and a high PF value.
　本発明に係るエアフィルタ用濾材では、前記生分解性繊維が、再生セルロース繊維、天然セルロース繊維及びポリ乳酸主体繊維からなる群より選ばれる少なくとも１種であることが好ましい。これにより、高いＰＦ値と生分解性を有する濾材を得ることができる。 In the air filter medium of the present invention, it is preferable that the biodegradable fiber is at least one selected from the group consisting of regenerated cellulose fiber, natural cellulose fiber, and polylactic acid-based fiber. This makes it possible to obtain a filter medium with a high PF value and biodegradability.
　本発明に係るエアフィルタ用濾材では、生分解性バインダーを含んでもよい。これにより、生分解性を有しつつ、フィルタの加工及び使用のために十分な強度と剛度を有する濾材を得ることができる。 The air filter medium of the present invention may contain a biodegradable binder. This makes it possible to obtain a filter medium that is biodegradable and has sufficient strength and rigidity for processing and use of the filter.
　本発明に係るエアフィルタ用濾材では、生分解性バインダーがポリビニルアルコール及び／又はポリ乳酸であってもよい。これにより、ＰＦ値を大幅に低下させずに十分な強度と剛度を有する濾材を得ることができる。 In the air filter medium of the present invention, the biodegradable binder may be polyvinyl alcohol and/or polylactic acid. This makes it possible to obtain a filter medium with sufficient strength and stiffness without significantly decreasing the PF value.
　本発明に係るエアフィルタ用濾材では、前記アルキルケテンダイマーが前記生分解性バインダーの連続皮膜により被覆されていないことが好ましい。これにより、撥水性を保持しつつ十分な強度と剛度を有する濾材を得ることができる。 In the air filter medium of the present invention, it is preferable that the alkyl ketene dimer is not covered with a continuous film of the biodegradable binder. This makes it possible to obtain a filter medium that has sufficient strength and rigidity while retaining water repellency.
　本発明に係るエアフィルタ用濾材の製造方法は、叩解繊維と非叩解繊維を水に分散させた原料スラリーを湿式抄紙法によってシート化して湿潤シートを形成する抄紙工程と、前記湿潤シートにアルキルケテンダイマーを付与する工程と、アルキルケテンダイマーを付与した前記湿潤シートを熱乾燥して乾燥シートを形成する乾燥工程とを有することを特徴とする。このような方法によれば、十分な撥水性と高いＰＦ値を有する濾材を得ることができる。 The method for producing a filter medium for air filters according to the present invention is characterized by comprising a papermaking process in which a raw material slurry in which beaten fibers and non-beaten fibers are dispersed in water is made into a sheet by a wet papermaking method to form a wet sheet, a process in which an alkyl ketene dimer is applied to the wet sheet, and a drying process in which the wet sheet to which the alkyl ketene dimer has been applied is thermally dried to form a dry sheet. This method makes it possible to obtain a filter medium with sufficient water repellency and a high PF value.
　本発明に係るエアフィルタ用濾材の製造方法では、原料スラリー中に繊維とともにバインダーを分散させてもよい。これにより、アルキルケテンダイマーによる撥水性及びＰＦ値の向上効果を阻害することなく、十分な強度と剛度を有する濾材を得ることができる。 In the method for producing a filter medium for air filters according to the present invention, a binder may be dispersed in the raw material slurry together with the fibers. This makes it possible to obtain a filter medium with sufficient strength and rigidity without impairing the effect of the alkyl ketene dimer in improving water repellency and PF value.
　本開示により、環境負荷が小さく、且つ使用時の濾過性能の低下が小さい濾材を得ることができる。すなわち、再生可能材料を含み、且つ生分解性を有し、更にはフィブリル化リヨセル繊維を含むセルロース系繊維の吸湿を防ぐために十分な撥水性を有するエアフィルタ用濾材を得ることができる。 The present disclosure makes it possible to obtain a filter medium that has a small environmental impact and exhibits little deterioration in filtering performance during use. In other words, it is possible to obtain a filter medium for air filters that contains renewable materials, is biodegradable, and has sufficient water repellency to prevent moisture absorption by cellulosic fibers, including fibrillated lyocell fibers.
　次に、本発明について実施形態を示して詳細に説明するが、本発明はこれらの記載に限定して解釈されない。本発明の効果を奏する限り、実施形態は種々の変形をしてもよい。 Next, the present invention will be described in detail with reference to an embodiment, but the present invention should not be interpreted as being limited to these descriptions. Various modifications of the embodiment may be made as long as the effects of the present invention are achieved.
　本実施形態におけるリヨセル繊維とは、溶剤としてＮ－メチルモルホリンＮ－オキシドを用いた有機溶剤紡糸法によって紡糸された再生セルロース繊維である。有機溶剤紡糸法は、セルロースをそのまま有機溶剤に溶解させて紡糸するため、分子の切断が少なく、平均重合度が他の再生セルロース繊維に比べて高く、繊維の剛直性が高いとともに、繊維の断面形状が円形に近い特徴を有する。この剛直性と断面形状により、濾材中の空隙を維持し易くなる。又、叩解後のフィブリル化リヨセル繊維も、前記の剛直性と断面形状を維持するため、濾材中の空隙を維持し易くなる。更に、叩解によってフィブリル化されると、粒子捕集に寄与する繊維の表面積が大きくなるため、捕集効率が上昇するとともに、繊維同士の絡み合いが多くなるため、濾材の引張強度が上昇する。 The lyocell fiber in this embodiment is a regenerated cellulose fiber spun by an organic solvent spinning method using N-methylmorpholine N-oxide as a solvent. In the organic solvent spinning method, cellulose is dissolved in an organic solvent as it is and spun, so there is little molecular breakage, the average degree of polymerization is higher than other regenerated cellulose fibers, the fiber has high rigidity, and the cross-sectional shape of the fiber is close to circular. This rigidity and cross-sectional shape make it easier to maintain the voids in the filter medium. In addition, the fibrillated lyocell fiber after beating also maintains the rigidity and cross-sectional shape, making it easier to maintain the voids in the filter medium. Furthermore, when fibrillated by beating, the surface area of the fiber that contributes to particle collection increases, increasing the collection efficiency, and the fibers become more entangled, increasing the tensile strength of the filter medium.
　本実施形態における叩解繊維は、フィブリル化リヨセル繊維であり、叩解繊維の配合量は、濾材を構成する叩解繊維、非叩解繊維及びバインダーの合計を１００部とすると、そのうち、２～３０部であることが好ましく、３～２０部であることがより好ましく、５～１５部であることが更に好ましい。配合量が２部未満であると、粒子捕集に寄与する繊維の表面積が十分でなく、十分な捕集効率が得られにくい。一方で、配合量が３０部を超えると、繊維同士の絡まりが多すぎるために空隙を塞いで、捕集効率の上昇に比して圧力損失が大きく上昇し、ＰＦ値が低下する恐れがある。 The beaten fibers in this embodiment are fibrillated lyocell fibers, and the amount of beaten fibers is preferably 2 to 30 parts, more preferably 3 to 20 parts, and even more preferably 5 to 15 parts, of 100 parts of the total of the beaten fibers, unbeaten fibers, and binder that make up the filter medium. If the amount is less than 2 parts, the surface area of the fibers that contributes to particle capture is insufficient, making it difficult to achieve sufficient capture efficiency. On the other hand, if the amount exceeds 30 parts, the fibers become too entangled and block the voids, resulting in a large increase in pressure loss compared to the increase in capture efficiency, and a decrease in the PF value.
　リヨセル繊維をフィブリル化するための叩解方法としては、ナイアガラビーター、ＰＦＩミル、シングルディスクリファイナー、ダブルディスクリファイナー、デフレーカー等の叩解機又は離解機を使用できる。叩解においては、リヨセルの繊維長を短くしすぎないように、強すぎる負荷をかけずに叩解することが好ましい。 As a beating method for fibrillating lyocell fibers, a beating machine or disintegrator such as a Niagara beater, PFI mill, single disc refiner, double disc refiner, or deflaker can be used. During beating, it is preferable to beat without applying too strong a load so as not to shorten the fiber length of the lyocell too much.
　リヨセル繊維の叩解を進めると、繊維が切断されて繊維長が短くなる。繊維長が短くなりすぎると、シート形成後の空隙を埋めてしまうため、圧力損失が高くなる恐れがある。一方で繊維長が長すぎると、水に分散させて原料スラリーとする際の分散性が悪くなり、濾材の構造が不均一となる恐れがある。本発明で使用するフィブリル化リヨセル繊維の長さ荷重平均繊維長は０．６ｍｍ以上であることが好ましく、０．８～３ｍｍであることがより好ましく、１～２ｍｍであることが更に好ましい。 As the beating of lyocell fibers proceeds, the fibers are cut and the fiber length shortens. If the fiber length becomes too short, it may fill the voids after the sheet is formed, resulting in high pressure loss. On the other hand, if the fiber length is too long, it may become less dispersible when dispersed in water to form a raw material slurry, resulting in a non-uniform structure of the filter medium. The length-weighted average fiber length of the fibrillated lyocell fibers used in the present invention is preferably 0.6 mm or more, more preferably 0.8 to 3 mm, and even more preferably 1 to 2 mm.
　尚、フィブリル化リヨセル繊維の長さ加重平均繊維長は、ＩＳＯ１６０６５－２：２０１４「Ｄｅｔｅｒｍｉｎａｔｉｏｎ　ｏｆ　ｆｉｂｒｅ　ｌｅｎｇｔｈ　ｂｙ　ａｕｔｏｍａｔｅｄ　ｏｐｔｉｃａｌ　ａｎａｌｙｓｉｓ－Ｐａｒｔ２：Ｕｎｐｏｌａｒｉｚｅｄ　ｌｉｇｈｔ　ｍｅｔｈｏｄ」に従って測定した。 The length-weighted average fiber length of fibrillated lyocell fibers was measured in accordance with ISO16065-2:2014 "Determination of fiber length by automated optical analysis - Part 2: Unpolarized light method."
　リヨセル繊維は、叩解によりフィブリル化が進行して繊維径が細くなる。繊維径が細すぎると、繊維が切断されやすくなり、前記した繊維長が短くなる問題が起きる。一方で繊維径が太すぎると、粒子捕集に寄与する繊維の表面積が不十分となる。本実施形態で使用するフィブリル化リヨセル繊維の平均繊維径は０．３μｍ以上であることが好ましく、０．４～１．５μｍであることがより好ましく、０．５～１．０μｍであることが更に好ましい。 The lyocell fiber undergoes fibrillation by beating, resulting in a thinner fiber diameter. If the fiber diameter is too thin, the fiber is more likely to be cut, resulting in the aforementioned problem of shortening the fiber length. On the other hand, if the fiber diameter is too thick, the surface area of the fiber that contributes to particle collection is insufficient. The average fiber diameter of the fibrillated lyocell fiber used in this embodiment is preferably 0.3 μm or more, more preferably 0.4 to 1.5 μm, and even more preferably 0.5 to 1.0 μm.
　尚、本実施形態におけるフィブリル化リヨセルの平均繊維径は、窒素を用いたＢＥＴ多点法により測定された比表面積より、数２の式を用いて計算した。 In addition, the average fiber diameter of the fibrillated lyocell in this embodiment was calculated using the formula 2 from the specific surface area measured by the BET multipoint method using nitrogen.
Figure JPOXMLDOC01-appb-M000002
 ここで、リヨセルの繊維密度は１．５ｇ／ｃｍ３とする。
Figure JPOXMLDOC01-appb-M000002
 Here, the fiber density of Lyocell is assumed to be 1.5 g/ cm3 .
　本実施形態における非叩解繊維は、叩解されておらず、フィブリル化されていないか、又は表面がわずかに毛羽立っている生分解性繊維である。生分解性繊維としては、例えば、再生セルロース繊維、天然セルロース繊維、ポリ乳酸主体繊維、ポリブチレンサクシネート繊維、ポリヒドロキシアルカノエート繊維などが挙げられるが、熱乾燥時に繊維が溶融せず、溶融した繊維が濾材の孔を塞ぐことによりＰＦ値が低下する現象を防ぐことができるため、再生セルロース繊維、天然セルロース繊維及びポリ乳酸主体繊維からなる群より選ばれる少なくとも１種であることが好ましい。異なる種類及び／又は異なる繊維径を有する非叩解繊維を混合して使用してもよい。 The non-beaten fibers in this embodiment are biodegradable fibers that have not been beaten, have not been fibrillated, or have a slightly fuzzy surface. Examples of biodegradable fibers include regenerated cellulose fibers, natural cellulose fibers, polylactic acid-based fibers, polybutylene succinate fibers, and polyhydroxyalkanoate fibers. However, since the fibers do not melt during thermal drying and the molten fibers can be prevented from blocking the pores of the filter medium, thereby preventing a decrease in the PF value, it is preferable to use at least one type selected from the group consisting of regenerated cellulose fibers, natural cellulose fibers, and polylactic acid-based fibers. Non-beaten fibers of different types and/or different fiber diameters may be mixed and used.
　本実施形態における非叩解繊維の配合量は、濾材を構成する叩解繊維、非叩解繊維及びバインダーの合計を１００部とすると、そのうち、５０～９８部であることが好ましく、６０～９５部であることがより好ましく、７０～９０部であることが更に好ましい。非叩解繊維の配合量が５０部未満であると、叩解繊維及び／又はバインダーの配合量が高くなるためＰＦ値が低下する。一方で、非叩解繊維の配合量が９８部を超えると十分な捕集効率並びに／又は強度及び剛度が得られなくなる。 In this embodiment, the amount of unbeaten fibers is preferably 50 to 98 parts, more preferably 60 to 95 parts, and even more preferably 70 to 90 parts, of 100 parts of the total of beaten fibers, unbeaten fibers, and binders that make up the filter medium. If the amount of unbeaten fibers is less than 50 parts, the amount of beaten fibers and/or binder will be high, resulting in a low PF value. On the other hand, if the amount of unbeaten fibers exceeds 98 parts, sufficient collection efficiency and/or strength and stiffness will not be obtained.
　再生セルロース繊維とは、セルロースを原料として、ビスコース法により紡糸された紡糸されたビスコースレーヨン繊維や、有機溶媒紡糸法により紡糸されたリヨセル繊維などである。これらは、木材パルプを原料とした再生可能材料であり、土中埋没分解性及び海洋生分解性を有している。 Regenerated cellulose fibers are made from cellulose, such as viscose rayon fibers spun using the viscose method and lyocell fibers spun using the organic solvent spinning method. These are renewable materials made from wood pulp, and are biodegradable in soil burials and in the ocean.
　天然セルロース繊維とは、植物から取り出されたセルロースを主体とした繊維であり、木材パルプ、コットンリンターパルプ、麻パルプ、ケナフパルプ、木材パルプをアルカリ処理して得られるマーセル化パルプ等がある。これらは、植物を原材料とした再生可能材料であり、土中埋没生分解性を有している。 Natural cellulose fibers are fibers that are primarily made from cellulose extracted from plants, and include wood pulp, cotton linter pulp, hemp pulp, kenaf pulp, and mercerized pulp obtained by treating wood pulp with alkali. These are renewable materials made from plants and are biodegradable when buried in the soil.
　ポリ乳酸繊維とは、バイオマス由来の澱粉を原料として糖化及び発酵による得られた乳酸を重合したポリ乳酸を紡糸した繊維であり、土中埋没生分解性を有している。ポリ乳酸繊維は、セルロース繊維と異なり熱可塑性を有しているため、濾材に熱成形性を付与することができる。ポリ乳酸繊維としては、１７０℃以上の融点を有する通常のポリ乳酸からなる主体繊維の他に、分子構造の改変により融点を１７０℃未満に低下させたポリ乳酸を部分的に用いたバインダー繊維も利用されている。本実施形態においては、ポリ乳酸主体繊維は非叩解繊維として用い、ポリ乳酸バインダー繊維は後記のバインダーとして用いる。 Polylactic acid fiber is a fiber spun from polylactic acid, which is polymerized from lactic acid obtained by saccharification and fermentation of biomass-derived starch as a raw material, and is biodegradable when buried in soil. Unlike cellulose fiber, polylactic acid fiber has thermoplasticity, so it can be used to give thermoformability to filter media. In addition to main fibers made of normal polylactic acid with a melting point of 170°C or higher, binder fibers that partially use polylactic acid whose melting point has been lowered to less than 170°C by modifying the molecular structure are also used as polylactic acid main fibers. In this embodiment, polylactic acid main fibers are used as unbeaten fibers, and polylactic acid binder fibers are used as a binder, which will be described later.
　本実施形態における非叩解繊維は、平均繊維径が５μｍ以上であることが好ましく、より好ましくは６～５０μｍであり、更に好ましくは７～４０μｍである。平均繊維径が５μｍよりも細いと、叩解繊維を均一に分布させるために必要な空隙を維持することが難しくなり、圧力損失の上昇を引き起こす恐れがある。一方で、平均繊維径が５０μｍを超えると、叩解繊維との繊維径の差異が大きいために、濾材の孔径のばらつきが大きくなり、捕集効率の低下を引き起こす恐れがある。 In this embodiment, the non-beaten fibers preferably have an average fiber diameter of 5 μm or more, more preferably 6 to 50 μm, and even more preferably 7 to 40 μm. If the average fiber diameter is smaller than 5 μm, it becomes difficult to maintain the voids necessary to uniformly distribute the beaten fibers, which may cause an increase in pressure loss. On the other hand, if the average fiber diameter exceeds 50 μm, the difference in fiber diameter from the beaten fibers is large, which may cause a large variation in the pore size of the filter medium and a decrease in collection efficiency.
　本実施形態におけるアルキルケテンダイマーは、天然物由来の脂肪酸（例えば、炭素数１６のパルチミン酸や炭素数１８のステアリン酸）を原料として、酸塩化物を経由して反応させて二量体としたものである。紙において、インキの染み込みを防止するサイズ剤として広く使用されている。又、生分解性を有しており、生分解性材料の耐水化剤としての利用が検討されている（例えば、非特許文献１を参照。）。本実施形態においては、濾材を構成する繊維に対して十分な撥水性を付与し、濾材使用中の濾過性能の低下を防止するために用いられる。 The alkyl ketene dimer in this embodiment is a dimer obtained by reacting naturally derived fatty acids (e.g. palmitic acid with 16 carbon atoms or stearic acid with 18 carbon atoms) via acid chloride. It is widely used as a sizing agent in paper to prevent ink from penetrating. It is also biodegradable, and its use as a water-resistant agent for biodegradable materials is being considered (see, for example, Non-Patent Document 1). In this embodiment, it is used to impart sufficient water repellency to the fibers that make up the filter medium and to prevent a decrease in the filter performance during use of the filter medium.
　本実施形態におけるアルキルケテンダイマーの濾材全体に対する含有量は、０．０５～２．０質量％であることが好ましく、０．１～１．８質量％がより好ましく、０．６～１．７質量％であることが特に好ましい。含有量が０．０５質量％未満であると、十分な撥水性（例えば、１００ｍｍ水柱高）が得られない場合がある。一方、含有量が０．０５質量％以上であると、十分な撥水性（例えば、１００ｍｍ水柱高）を得ることができ、含有量が０．１質量％以上であると、より高い撥水性（例えば、２００ｍｍ水柱高）を得ることができる。アルキルケテンダイマーの含有量が２．０質量％を超えると、ＰＦ値が低下する恐れがある。 In this embodiment, the content of alkyl ketene dimer in the entire filter medium is preferably 0.05 to 2.0 mass%, more preferably 0.1 to 1.8 mass%, and particularly preferably 0.6 to 1.7 mass%. If the content is less than 0.05 mass%, sufficient water repellency (e.g., 100 mm water column height) may not be obtained. On the other hand, if the content is 0.05 mass% or more, sufficient water repellency (e.g., 100 mm water column height) can be obtained, and if the content is 0.1 mass% or more, even higher water repellency (e.g., 200 mm water column height) can be obtained. If the alkyl ketene dimer content exceeds 2.0 mass%, the PF value may decrease.
　又、アルキルケテンダイマーの濾材全体に対する含有量を適切な範囲にすることにより、濾材のＰＦ値を上昇できることを本発明者は見出した。このＰＦ値を上昇させる機構は定かではないが、適切な量のアルキルケテンダイマーをフィブリル化リヨセル繊維の表面に付着させた場合においては、繊維同士の凝集を防いで繊維の表面積を上昇させることにより捕集効率を上昇させるとともに、繊維間の空隙を広げることにより圧力損失を低下させるため、ＰＦ値を上昇させるものと推定される。一方で多すぎる量のアルキルケテンダイマーを付着させた場合においては、アルキルケテンダイマーが繊維間の空隙を埋めて繊維の表面積を低下させることにより捕集効率を低下させるとともに、目詰まりにより圧力損失を不必要に上昇させるため、ＰＦ値を低下させるものと推定される。アルキルケテンダイマーの濾材全体に対する含有量が０．０５～２質量％の範囲であると、アルキルケテンダイマー非含有の場合よりも高いＰＦ値を得ることができ、含有量が０．１～１．５質量％であると、更に高い（例えば、アルキルケテンダイマー非含有よりも０．８ポイント以上高い）ＰＦ値を得ることができる。 The inventors have also found that the PF value of the filter medium can be increased by adjusting the content of alkyl ketene dimer in the entire filter medium to an appropriate range. Although the mechanism by which this PF value is increased is unclear, it is presumed that when an appropriate amount of alkyl ketene dimer is attached to the surface of fibrillated lyocell fibers, the PF value is increased because the collection efficiency is increased by preventing the fibers from agglomerating and increasing the surface area of the fibers, and the pressure loss is reduced by expanding the gaps between the fibers. On the other hand, when too much alkyl ketene dimer is attached, it is presumed that the PF value is reduced because the alkyl ketene dimer fills the gaps between the fibers, reducing the surface area of the fibers, thereby reducing the collection efficiency, and unnecessarily increasing the pressure loss due to clogging. When the content of alkyl ketene dimer in the entire filter medium is in the range of 0.05 to 2 mass%, a higher PF value can be obtained than when no alkyl ketene dimer is contained, and when the content is 0.1 to 1.5 mass%, an even higher PF value (for example, 0.8 points higher than when no alkyl ketene dimer is contained) can be obtained.
　本実施形態においては、強度及び剛度の向上を目的として、濾材中に生分解性バインダーを含有してもよい。生分解性バインダーとしては、例えば、ポリビニルアルコール、ポリ乳酸、又は、ポリビニルアルコール及びポリ乳酸の両方を使用することができる。ポリビニルアルコールは、生分解性を有するとともに繊維同士を接着するものであり、叩解繊維及び非叩解繊維と一緒に水に分散して原料スラリーとすることが可能な繊維状又は粉末状のものであるか、又はアルキルケテンダイマーと混合して含浸又は塗布等の方法により付着させることが可能な水溶液又は水分散液の状態にできるものである。ポリ乳酸は、前記のポリ乳酸バインダー繊維であり、融点以上に加熱された場合に繊維同士を接着するものである。生分解性バインダーは粉末状であることがより好ましい。均一に分散し、繊維と点接着するため、ＰＦ値を大きく低下させずに高い強度、剛度を得ることができる。粉末状バインダーはポリビニルアルコールであることが特に好ましい。更に高い強度、剛度を得ることができる。一方で、水溶液又は水分散液の状態の生分解性バインダーは、濾材全体にわたって繊維を被覆する連続皮膜を形成してＰＦ値を低下させる恐れがあるため、付着量を多くしすぎないようにする等の注意が必要である。 In this embodiment, a biodegradable binder may be contained in the filter medium for the purpose of improving strength and stiffness. As the biodegradable binder, for example, polyvinyl alcohol, polylactic acid, or both polyvinyl alcohol and polylactic acid can be used. Polyvinyl alcohol is biodegradable and bonds fibers together, and is either fibrous or powdery, which can be dispersed in water together with beaten fibers and non-beaten fibers to form a raw material slurry, or can be mixed with an alkyl ketene dimer to form an aqueous solution or aqueous dispersion that can be attached by a method such as impregnation or coating. Polylactic acid is the polylactic acid binder fiber described above, which bonds fibers together when heated above its melting point. It is more preferable that the biodegradable binder is in powder form. It is uniformly dispersed and point-bonded to the fibers, so that high strength and stiffness can be obtained without significantly decreasing the PF value. It is particularly preferable that the powdered binder is polyvinyl alcohol. Even higher strength and stiffness can be obtained. On the other hand, biodegradable binders in the form of an aqueous solution or dispersion may form a continuous film that covers the fibers throughout the entire filter medium, lowering the PF value, so care must be taken not to apply too much.
　本実施形態において、濾材に生分解性バインダーを含有させる場合の生分解性バインダーの配合量は、濾材を構成する繊維及びバインダーの合計を１００部とすると、そのうち、０．５～２０部であることが好ましく、１～１５部であることがより好ましい。配合量が０．５部未満であると、十分な強度及び剛度の向上効果が得られない恐れがあり、２０部を超えると、ＰＦ値が低下する恐れがある。 In this embodiment, when a biodegradable binder is contained in the filter medium, the amount of the biodegradable binder is preferably 0.5 to 20 parts, and more preferably 1 to 15 parts, of 100 parts of the total of the fibers and binder that make up the filter medium. If the amount is less than 0.5 parts, there is a risk that sufficient improvement in strength and stiffness will not be obtained, and if it exceeds 20 parts, there is a risk that the PF value will decrease.
　本実施形態においては、本発明の効果を妨げない範囲で、濾材に消泡剤、分散剤等の添加剤を適宜含めることができる。 In this embodiment, additives such as antifoaming agents and dispersants can be appropriately added to the filter medium as long as they do not impede the effects of the present invention.
　本実施形態の濾材の製造方法は、湿式抄紙法を用いる。すなわち、濾材を構成する繊維をパルパー等の分散機を用いて水中に分散させて、得られた原料スラリーをワイヤー上に堆積及び脱水して湿潤シートを形成して、得られた湿潤シートに含浸又は塗布等の方法によりアルキルケテンダイマーを付与して、熱風ドライヤーやシリンダードライヤー等の乾燥機を用いて乾燥して、乾燥シートとしての濾材を得る。乾燥後のシートにアルキルケテンダイマーを付与した場合は、アルキルケテンダイマーによるＰＦ値の向上効果が十分に得られない。 The method for producing the filter medium in this embodiment uses a wet papermaking method. That is, the fibers that make up the filter medium are dispersed in water using a dispersing machine such as a pulper, the resulting raw material slurry is deposited on a wire and dehydrated to form a wet sheet, and the resulting wet sheet is impregnated with an alkyl ketene dimer by a method such as impregnation or coating, and dried using a dryer such as a hot air dryer or cylinder dryer to obtain the filter medium as a dry sheet. If an alkyl ketene dimer is imparted to the dried sheet, the effect of improving the PF value by the alkyl ketene dimer cannot be fully obtained.
　本実施形態の濾材の製造方法において、生分解性バインダーを含有させる場合は、前記の湿式抄紙法を用いる製造において、原料スラリー中に濾材を構成する繊維とともに生分解性バインダーを分散させることが好ましい。水溶液又は水分散液の状態の生分解性バインダーをアルキルケテンダイマーと混合して含浸又は塗布等の方法により同時に付与した場合は、アルキルケテンダイマーが生分解性バインダーの連続皮膜により被覆されるため、撥水性が十分に得られない恐れがある。原料スラリー中に濾材を構成する繊維とともに生分解性バインダーを分散させて湿潤シートとしてから湿潤シートにアルキルケテンダイマーを付与することが好ましい。 In the method for producing the filter medium of this embodiment, when a biodegradable binder is contained, it is preferable to disperse the biodegradable binder in the raw material slurry together with the fibers that make up the filter medium in the production using the above-mentioned wet papermaking method. If the biodegradable binder in the form of an aqueous solution or aqueous dispersion is mixed with the alkyl ketene dimer and applied simultaneously by a method such as impregnation or coating, the alkyl ketene dimer will be covered with a continuous film of the biodegradable binder, and there is a risk that sufficient water repellency will not be obtained. It is preferable to disperse the biodegradable binder in the raw material slurry together with the fibers that make up the filter medium to form a wet sheet, and then apply the alkyl ketene dimer to the wet sheet.
　本実施形態においては、本発明の効果を妨げない範囲で、原料スラリーに消泡剤、分散剤等の添加剤を適宜添加することができる。 In this embodiment, additives such as antifoaming agents and dispersants can be added to the raw material slurry as appropriate, as long as they do not impede the effects of the present invention.
　本実施形態における濾材の坪量は、特に限定するものではないが、好ましくは２５～３５０ｇ／ｍ2、より好ましくは５０～２５０ｇ／ｍ2、更に好ましくは７０～１５０ｇ／ｍ2である。坪量が２５ｇ／ｍ２未満であると、十分な引張強度及び／又はガーレー剛度が得られない場合がある。一方で、坪量が３５０ｇ／ｍ２を超えると、フィルタユニットに収容可能な濾材の面積が不十分となる場合がある。 The basis weight of the filter medium in this embodiment is not particularly limited, but is preferably 25 to 350 g/m 2 , more preferably 50 to 250 g/m 2 , and even more preferably 70 to 150 g/m 2 . If the basis weight is less than 25 g/m 2 , sufficient tensile strength and/or Gurley stiffness may not be obtained. On the other hand, if the basis weight is more than 350 g/m 2 , the area of the filter medium that can be accommodated in the filter unit may be insufficient.
　本実施形態における濾材のＰＦ値は、特に限定するものではないが、好ましくは４．５以上であり、より好ましくは６．０以上、更に好ましくは７．０以上である。これにより、圧力損失と捕集効率のバランスが良い濾材となる。 The PF value of the filter medium in this embodiment is not particularly limited, but is preferably 4.5 or more, more preferably 6.0 or more, and even more preferably 7.0 or more. This results in a filter medium with a good balance between pressure loss and collection efficiency.
　本実施形態における濾材の引張強度は、用途や後加工の方法に応じて必要とされる引張強度が異なり、特に限定するものではないが、好ましくは０．４０ｋＮ／ｍ以上であり、より好ましくは０．４５ｋＮ／ｍ以上である。引張強度が０．４０ｋＮ／ｍ以上であれば、多くの用途に対応できる。 The tensile strength of the filter medium in this embodiment varies depending on the application and post-processing method, and is not particularly limited, but is preferably 0.40 kN/m or more, and more preferably 0.45 kN/m or more. A tensile strength of 0.40 kN/m or more can be used for many applications.
　本実施形態における濾材のガーレー剛度は、用途や後加工の方法に応じて必要とされるガーレー剛度が異なり、特に限定するものではないが、好ましくは７．０ｍＮ以上であり、より好ましくは１０．０ｍＮ以上である。る。ガーレー剛度が７．０ｍＮであれば、多くの用途に対応できる。 The Gurley stiffness of the filter medium in this embodiment differs depending on the application and post-processing method, and is not particularly limited, but is preferably 7.0 mN or more, and more preferably 10.0 mN or more. A Gurley stiffness of 7.0 mN can be used for many applications.
　以下に、本発明に係る実施例及び比較例を挙げて本発明を具体的に説明する。しかし、本発明はこれらに限定されるものではない。 The present invention will be specifically explained below with reference to examples and comparative examples. However, the present invention is not limited to these.
＜実施例１＞
　叩解繊維としてリヨセル繊維（Ｌｅｎｚｉｎｇ　ＡＧ製）を叩解して得られたフィブリル化リヨセル繊維（平均繊維径０．８μｍ、長さ加重平均繊維長１．１ｍｍ）１４部と、非叩解繊維として再生セルロース繊維であるリヨセル繊維（Ｌｅｎｚｉｎｇ　ＡＧ製、平均繊維径１２μｍ、平均繊維長４ｍｍ）８６部を、スラリー濃度が０．５質量％となるように水道水を加えてミキサーを用いて離解して、原料スラリーを得た。次に、手抄装置を用いて得られた原料スラリーを抄紙して、湿潤シートを得た。次に、得られた湿潤シートに、アルキルケテンダイマー（ＳＥ２３６０、星光ＰＭＣ（株）製）の水希釈液を、濾材全体に対するアルキルケテンダイマー含有量が固形分で０．０１質量％となるように含浸処理により付与して、１３０℃のロータリードライヤーを用いて乾燥して、乾燥シートとして坪量１００ｇ／ｍ２のエアフィルタ用濾材を得た。 Example 1
14 parts of fibrillated lyocell fiber (average fiber diameter 0.8 μm, length-weighted average fiber length 1.1 mm) obtained by beating lyocell fiber (manufactured by Lenzing AG) as beaten fiber, and 86 parts of regenerated cellulose fiber lyocell fiber (manufactured by Lenzing AG, average fiber diameter 12 μm, average fiber length 4 mm) as non-beaten fiber were added with tap water so that the slurry concentration was 0.5 mass%, and disintegrated using a mixer to obtain a raw material slurry. Next, the raw material slurry obtained using a hand-made papermaking device was made into a wet sheet. Next, the obtained wet sheet was impregnated with a water dilution of alkyl ketene dimer (SE2360, manufactured by Seiko PMC Co., Ltd.) so that the alkyl ketene dimer content in the entire filter material was 0.01 mass% in solid content, and dried using a rotary dryer at 130 ° C. to obtain a filter material for air filters with a basis weight of 100 g / m 2 as a dried sheet.
＜実施例２～１２＞
　濾材全体に対するアルキルケテンダイマー含有量が固形分で、表１に示した０．０５～１０質量％の範囲の各数値となるように含浸処理を行った以外は、実施例１と同様の方法により、坪量が１００～１１０ｇ／ｍ２の範囲のエアフィルタ用濾材を得た。 <Examples 2 to 12>
Except for carrying out impregnation treatment so that the alkyl ketene dimer content in the entire filter medium is in the range of 0.05 to 10 mass% as shown in Table 1, obtain air filter medium with basis weight in the range of 100 to 110 g/ m2 by the same method as in Example 1.
＜実施例１３＞
　非叩解繊維として天然セルロース繊維であるマーセル化パルプ（ポロセニア、Ｒａｙｏｎｉｅｒ　Ｉｎｃ．製、平均繊維径３４μｍ、平均繊維長２．６ｍｍ）８６部を用いたことと、アルキルケテンダイマー含有量が固形分で１．０質量％となるように含浸処理を行った以外は実施例１と同様の方法により、坪量１０１ｇ／ｍ２のエアフィルタ用濾材を得た。 Example 13
Use 86 parts of mercerized pulp (Porosenia, manufactured by Rayonier Inc., average fiber diameter 34 μm, average fiber length 2.6 mm) as natural cellulose fiber as non-beaten fiber, and impregnate so that alkyl ketene dimer content is 1.0 mass% in solid content, and obtain air filter material with basis weight of 101g/ m2 by the same method as in Example 1.
＜実施例１４＞
　非叩解繊維としてリヨセル繊維（Ｌｅｎｚｉｎｇ　ＡＧ製、平均繊維径１２μｍ、平均繊維長４ｍｍ）７６部と、ポリ乳酸主体繊維（ＰＬ０１、ユニチカ（株）製、平均繊維径１３μｍ、平均繊維長５ｍｍ、融点１７０℃）１０部を用いた以外は、実施例１３と同様の方法により、坪量１０１ｇ／ｍ２のエアフィルタ用濾材を得た。 <Example 14>
As non-beaten fiber, use 76 parts of Lyocell fiber (manufactured by Lenzing AG, average fiber diameter 12 μm, average fiber length 4 mm) and 10 parts of polylactic acid-based fiber (PL01, manufactured by Unitika Co., Ltd., average fiber diameter 13 μm, average fiber length 5 mm, melting point 170 ° C.), but use the same method as in Example 13 to obtain air filter material with basis weight of 101 g / m 2 .
＜実施例１５＞
　非叩解繊維としてリヨセル繊維（Ｌｅｎｚｉｎｇ　ＡＧ製、平均繊維径１２μｍ、平均繊維長４ｍｍ）８４部と、バインダーとしてポリビニルアルコール粉末（ポバールＫ－１７７、デンカ（株）製）２部を用いて原料スラリーを得た以外は、実施例１３と同様の方法により、坪量１０１ｇ／ｍ２のエアフィルタ用濾材を得た。 Example 15
Use 84 parts of Lyocell fiber (manufactured by Lenzing AG, average fiber diameter 12 μm, average fiber length 4 mm) as non-beaten fiber, and 2 parts of polyvinyl alcohol powder (Poval K-177, manufactured by Denka Co., Ltd.) as binder to obtain raw material slurry, and obtain air filter material with basis weight of 101 g/ m2 by the same method as in Example 13.
＜実施例１６＞
　非叩解繊維としてリヨセル繊維（Ｌｅｎｚｉｎｇ　ＡＧ製、平均繊維径１２μｍ、平均繊維長４ｍｍ）７６部と、バインダーとして芯鞘型ポリ乳酸バインダー繊維（ＰＬ８０、ユニチカ（株）製、平均繊維径１５μｍ、平均繊維長５ｍｍ、芯融点１７０℃、鞘融点１３０℃）１０部を用いて原料スラリーを得た以外は、実施例１３と同様の方法により、坪量１０１ｇ／ｍ２のエアフィルタ用濾材を得た。 <Example 16>
As non-beaten fiber, 76 parts of Lyocell fiber (manufactured by Lenzing AG, average fiber diameter 12 μm, average fiber length 4 mm) and as binder, 10 parts of core-sheath type polylactic acid binder fiber (PL80, manufactured by Unitika Co., Ltd., average fiber diameter 15 μm, average fiber length 5 mm, core melting point 170 ° C, sheath melting point 130 ° C) are used to obtain raw material slurry, and by the same method as in Example 13, obtain air filter material with basis weight of 101 g / m 2 .
＜実施例１７＞
　ポリビニルアルコール（ポバール２８－９８、（株）クラレ製）の水溶液とアルキルケテンダイマー（ＳＥ２３６０、星光ＰＭＣ（株）製）を混合した水希釈液を、濾材全体に対するポリビニルアルコール含有量が固形分で２．０質量％、アルキルケテンダイマー含有量が固形分で１．０質量％となるように含浸処理を行った以外は、実施例１と同様の方法により、坪量が１０３ｇ／ｍ２のエアフィルタ用濾材を得た。 <Example 17>
The aqueous solution of polyvinyl alcohol (Poval 28-98, manufactured by Kuraray Co., Ltd.) and alkyl ketene dimer (SE2360, manufactured by Seiko PMC Co., Ltd.) are mixed to form a water dilution, so that the polyvinyl alcohol content of the entire filter medium is 2.0 mass% in solid content, and the alkyl ketene dimer content is 1.0 mass% in solid content. Except for this, the same method as in Example 1 is used to obtain an air filter medium with a basis weight of 103 g/ m2 .
＜比較例１＞
　アルキルケテンダイマーの含浸処理を行わなかったこと以外は、実施例１と同様の方法により、坪量１００ｇ／ｍ２のエアフィルタ用濾材を得た。 <Comparative Example 1>
An air filter medium having a basis weight of 100 g/m 2 was obtained in the same manner as in Example 1, except that the impregnation treatment with alkyl ketene dimer was not performed.
＜比較例２＞
　アルキルケテンダイマーの代わりにパラフィンワックス撥水剤（ペトロックスＰ－３１０、明成化学工業（株）製）の水希釈液を、濾材全体に対するパラフィンワックス撥水剤含有量が固形分で１．０質量％となるように含浸処理により付与した以外は、実施例１と同様の方法により、坪量１０１ｇ／ｍ２のエアフィルタ用濾材を得た。 <Comparative Example 2>
Instead of alkyl ketene dimer, impregnate with water dilution of paraffin wax water repellent (Petrox P-310, manufactured by Meisei Chemical Industry Co., Ltd.) so that the paraffin wax water repellent content in the whole filter medium is 1.0 mass% in solid content, but obtain air filter medium with basis weight of 101g/ m2 by the same method as in Example 1.
　実施例及び比較例において得られたエアフィルタ用濾材の評価は、以下に示す方法を用いて行った。 The air filter media obtained in the examples and comparative examples were evaluated using the methods described below.
＜坪量＞
　坪量は、ＪＩＳ　Ｐ　８１２４：２０１１「紙及び板紙－坪量の測定方法」に従って測定した。 <Basance weight>
The basis weight was measured according to JIS P 8124:2011 "Paper and paperboard -- Determination of basis weight".
＜厚さ及び密度＞
　厚さ及び密度は、ＪＩＳ　Ｐ　８１１８：１９９８「紙及び板紙－厚さ及び密度の試験方法」に従って測定した。尚、測定圧力は５０ｋＰａとした。 <Thickness and density>
The thickness and density were measured in accordance with JIS P 8118:1998 "Paper and paperboard -- Test method for thickness and density" using a measurement pressure of 50 kPa.
＜圧力損失＞
　圧力損失は、有効面積１００ｃｍ２のエアフィルタ用濾材に面風速５．３ｃｍ／秒で通風した際の差圧として、マノメーター（マノスターゲージＷＯ８１、（株）山本電機製作所製）を用いて測定した。 <Pressure loss>
The pressure loss was measured as the differential pressure when air was passed through an air filter medium having an effective area of 100 cm2 at a face velocity of 5.3 cm/sec using a manometer (Manometer Gauge WO81, manufactured by Yamamoto Electric Works, Ltd.).
＜透過率＞
　透過率は、ラスキンノズルで発生させた多分散ポリアルファオレフィン（ＰＡＯ）粒子を含む空気が有効面積１００ｃｍ２のエアフィルタ用濾材に面風速５．３ｃｍ／秒で通風した際の上流及び下流のＰＡＯ粒子の個数をレーザーパーティクルカウンター（ＫＣ－２２Ｂ、リオン（株）製）を用いて測定し、上流と下流の粒子個数の比から求めた。対象粒子径は０．３μｍとし、０．２～０．３μｍと０．３～０．４μｍの透過率の幾何平均値として求めた。 <Transmittance>
The transmittance was calculated from the ratio of the number of particles upstream and downstream when air containing polydisperse polyalphaolefin (PAO) particles generated by a Laskin nozzle was blown through an air filter medium with an effective area of 100 cm2 at a surface velocity of 5.3 cm/sec, and the number of PAO particles upstream and downstream was measured using a laser particle counter (KC-22B, manufactured by Rion Co., Ltd.). The target particle size was 0.3 μm, and the transmittance was calculated as the geometric mean value of the transmittance of 0.2 to 0.3 μm and 0.3 to 0.4 μm.
＜ＰＦ値＞
　ＰＦ値は、圧力損失と透過率の値から、数１に示す式を用いて計算した。 <PF value>
The PF value was calculated from the pressure loss and the transmittance using the formula shown in Equation 1.
＜撥水性＞
　撥水性は、ＭＩＬ－ＳＴＤ－２８２に従って測定した。 <Water repellency>
Water repellency was measured according to MIL-STD-282.
＜引張強度＞
　引張強度は、万能試験機（オートグラフＡＧＳ－Ｘ、（株）島津製作所製）を用いて、試験幅２５．４ｍｍ、試験長１００ｍｍ、引張速度１５ｍｍ／分の条件で測定した。 <Tensile strength>
The tensile strength was measured using a universal testing machine (Autograph AGS-X, manufactured by Shimadzu Corporation) under conditions of a test width of 25.4 mm, a test length of 100 mm, and a tensile speed of 15 mm/min.
＜ガーレー剛度＞
　ガーレー剛度は、ＪＡＰＡＮ　ＴＡＰＰＩ　Ｎｏ．４０：２０００「紙及び板紙－荷重曲げによるこわさ試験方法－ガーレー法」に従って測定した。 <Gurley stiffness>
The Gurley stiffness was measured according to JAPAN TAPPI No. 40:2000 "Paper and paperboard -- Test method for stiffness by bending under load -- Gurley method."
　前記の方法で行ったエアフィルタ用濾材の評価結果を表１及び表２に示した。 The evaluation results of the air filter media performed using the above method are shown in Tables 1 and 2.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
　表１の実施例１～１２及び表２の比較例１の結果より、アルキルケテンダイマーの含有量を０．０５質量％以上とすることで１００ｍｍ水柱高以上の十分な撥水性を有するエアフィルタ用濾材が得られ、０．１質量％以上とすることで２００ｍｍ水柱高以上の更に高い撥水性を得ることができた。又、アルキルケテンダイマーの含有量を０．０５～２．０質量％の範囲とすることでアルキルケテンダイマー非含有の場合よりも高いＰＦ値を有するエアフィルタ用濾材が得られ、０．１～１．５質量％の範囲とすることでアルキルケテンダイマー非含有の場合よりも０．８ポイント以上高いＰＦ値が得られた。 The results of Examples 1 to 12 in Table 1 and Comparative Example 1 in Table 2 show that by setting the alkyl ketene dimer content to 0.05% by mass or more, air filter media with sufficient water repellency at a water column height of 100 mm or more can be obtained, and by setting it to 0.1% by mass or more, even higher water repellency at a water column height of 200 mm or more can be obtained. In addition, by setting the alkyl ketene dimer content in the range of 0.05 to 2.0% by mass, air filter media with a higher PF value than when no alkyl ketene dimer was contained was obtained, and by setting it in the range of 0.1 to 1.5% by mass, a PF value 0.8 points higher than when no alkyl ketene dimer was contained was obtained.
　表１の実施例６、表２の実施例１３及び１４の結果より、非叩解繊維に再生セルロース繊維、天然セルロース繊維及び／又はポリ乳酸主体繊維を用いることにより、十分な撥水性（１００ｍｍ水柱高以上）、ＰＦ値（４．５以上）、引張強度（０．４ｋＮ／ｍ以上）及びガーレー剛度（７．０ｍＮ以上）が得られた。 The results of Example 6 in Table 1 and Examples 13 and 14 in Table 2 show that by using regenerated cellulose fiber, natural cellulose fiber and/or polylactic acid-based fiber as the non-beaten fiber, sufficient water repellency (water column height of 100 mm or more), PF value (4.5 or more), tensile strength (0.4 kN/m or more) and Gurley stiffness (7.0 mN or more) were obtained.
　表１の実施例６、表２の実施例１５及び１６の結果より、バインダーを使用することにより、高い引張強度及びガーレー剛度が得られた。 The results of Example 6 in Table 1 and Examples 15 and 16 in Table 2 show that high tensile strength and Gurley stiffness were obtained by using a binder.
　表２の実施例１５及び１７の結果より、バインダーを予め含有させたシートに対してアルキルケテンダイマーを付与することにより、バインダーとアルキルケテンダイマーを同時に付与させた場合よりも高い撥水性が得られた。 The results of Examples 15 and 17 in Table 2 show that by adding alkyl ketene dimer to a sheet that already contained a binder, higher water repellency was obtained than when the binder and alkyl ketene dimer were added simultaneously.
　表１の実施例６及び表２の比較例２の結果より、アルキルケテンダイマーを付与することにより、パラフィンワックス撥水剤を付与した場合よりも高い撥水性が得られた。 The results of Example 6 in Table 1 and Comparative Example 2 in Table 2 show that adding alkyl ketene dimer resulted in higher water repellency than when a paraffin wax water repellent was added.
　本発明のエアフィルタ用濾材は、工場及びビルの空調、自動車客室、エアコン、空気清浄機、個人用保護具等の種々の分野で使用されるエアフィルタ用濾材に用いることができる。 The air filter medium of the present invention can be used as an air filter medium for use in a variety of fields, including factory and building air conditioning, automobile passenger compartments, air conditioners, air purifiers, and personal protective equipment.
　As used throughout this disclosure, the singular forms "a," "an," and "the" include plural reference unless the context clearly dictates otherwise. Thus, for example, a reference to "a composition" includes a plurality of such compositions, as well as a single composition.

  As used throughout this disclosure, the singular forms "a,""an," and "the" include plural reference unless the context clearly dictates otherwise. Thus, for example, a reference to "a composition" includes a plurality of such compositions, as well as a single composition.

Claims (10)

  1. 　湿式不織布からなる濾材であり、
    　前記濾材を構成する繊維が、叩解繊維と非叩解繊維とを含み、
    　前記叩解繊維がフィブリル化リヨセル繊維であり、
    　前記非叩解繊維が生分解性繊維であり、
    　前記濾材がアルキルケテンダイマーを含むことを特徴とするエアフィルタ用濾材。     This is a filter material made of wet nonwoven fabric.
    The fibers constituting the filter medium include beaten fibers and non-beaten fibers,
    The beaten fibers are fibrillated lyocell fibers,
    The unbeaten fiber is a biodegradable fiber,
    1. A filter medium for air filters, comprising an alkyl ketene dimer.
  2. 　前記アルキルケテンダイマーの濾材全体に対する含有量が、０．０５～２．０質量％の範囲にあることを特徴とする請求項１に記載のエアフィルタ用濾材。 The filter medium for air filters according to claim 1, characterized in that the content of the alkyl ketene dimer in the entire filter medium is in the range of 0.05 to 2.0 mass%.
  3. 　前記非叩解繊維である前記生分解性繊維が、再生セルロース繊維、天然セルロース繊維及びポリ乳酸主体繊維からなる群より選ばれる少なくとも１種であることを特徴とする請求項１又は２に記載のエアフィルタ用濾材。 The air filter medium according to claim 1 or 2, characterized in that the biodegradable fibers that are non-beaten fibers are at least one type selected from the group consisting of regenerated cellulose fibers, natural cellulose fibers, and polylactic acid-based fibers.
  4. 　生分解性バインダーを含むことを特徴とする請求項１又は２に記載のエアフィルタ用濾材。 The air filter medium according to claim 1 or 2, characterized in that it contains a biodegradable binder.
  5. 　前記生分解性バインダーがポリビニルアルコール、ポリ乳酸、又は、ポリビニルアルコール及びポリ乳酸を含むことを特徴とする請求項４に記載のエアフィルタ用濾材。 The air filter medium according to claim 4, characterized in that the biodegradable binder contains polyvinyl alcohol, polylactic acid, or polyvinyl alcohol and polylactic acid.
  6. 　前記アルキルケテンダイマーが前記生分解性バインダーの連続皮膜により被覆されていないことを特徴とする請求項４に記載のエアフィルタ用濾材。 The air filter medium according to claim 4, characterized in that the alkyl ketene dimer is not covered by a continuous film of the biodegradable binder.
  7. 　濾材を構成する叩解繊維及び非叩解繊維を水に分散させた原料スラリーを湿式抄紙法によってシート化して湿潤シートを形成する抄紙工程と、
    　前記湿潤シートにアルキルケテンダイマーを付与する工程と、
    　アルキルケテンダイマーを付与した前記湿潤シートを熱乾燥して乾燥シートを形成する乾燥工程と、を有し、
    　前記叩解繊維がフィブリル化リヨセル繊維であり、前記非叩解繊維が生分解性繊維であることを特徴とするエアフィルタ用濾材の製造方法。     A papermaking process in which a raw material slurry in which beaten fibers and non-beaten fibers constituting a filter medium are dispersed in water is formed into a sheet by a wet papermaking method to form a wet sheet;
    applying an alkyl ketene dimer to the wet sheet;
    A drying step of thermally drying the wet sheet to which the alkyl ketene dimer has been applied to form a dry sheet,
    A method for producing a filter medium for an air filter, characterized in that the beaten fibers are fibrillated lyocell fibers, and the non-beaten fibers are biodegradable fibers.
  8. 　前記アルキルケテンダイマーを、乾燥後の濾材全体に対する含有量が０．０５～２．０質量％の範囲となるように付与することを特徴とする請求項７に記載のエアフィルタ用濾材の製造方法。 The method for producing a filter medium for air filters according to claim 7, characterized in that the alkyl ketene dimer is added so that its content in the entire filter medium after drying is in the range of 0.05 to 2.0 mass%.
  9. 　前記非叩解繊維である前記生分解性繊維が、再生セルロース繊維、天然セルロース繊維及びポリ乳酸主体繊維からなる群より選ばれる少なくとも１種であることを特徴とする請求項７又は８に記載のエアフィルタ用濾材の製造方法。 The method for producing a filter material for air filters according to claim 7 or 8, characterized in that the biodegradable fibers that are the non-beaten fibers are at least one type selected from the group consisting of regenerated cellulose fibers, natural cellulose fibers, and polylactic acid-based fibers.
  10. 　前記原料スラリー中に前記叩解繊維及び前記非叩解繊維ととともに生分解性バインダーを分散させたことを特徴とする請求項７又は８に記載のエアフィルタ濾材の製造方法。

          9. The method for producing an air filter medium according to claim 7, wherein a biodegradable binder is dispersed in the raw material slurry together with the beaten fibers and the unbeaten fibers.
PCT/JP2023/034051 2022-12-05 2023-09-20 Filter material for air filter, and method for manufacturing same WO2024122160A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006167659A (en) * 2004-12-17 2006-06-29 Mitsubishi Paper Mills Ltd Filter material
JP2011036763A (en) * 2009-08-07 2011-02-24 Tomoegawa Paper Co Ltd Air filter medium and method for manufacturing the same
JP2014221456A (en) * 2013-05-13 2014-11-27 北越紀州製紙株式会社 Filter medium for air filter, and method of manufacturing the same

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006167659A (en) * 2004-12-17 2006-06-29 Mitsubishi Paper Mills Ltd Filter material
JP2011036763A (en) * 2009-08-07 2011-02-24 Tomoegawa Paper Co Ltd Air filter medium and method for manufacturing the same
JP2014221456A (en) * 2013-05-13 2014-11-27 北越紀州製紙株式会社 Filter medium for air filter, and method of manufacturing the same

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