WO2023163218A1 - Feuille d'électret et filtre - Google Patents

Feuille d'électret et filtre Download PDF

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Publication number
WO2023163218A1
WO2023163218A1 PCT/JP2023/007350 JP2023007350W WO2023163218A1 WO 2023163218 A1 WO2023163218 A1 WO 2023163218A1 JP 2023007350 W JP2023007350 W JP 2023007350W WO 2023163218 A1 WO2023163218 A1 WO 2023163218A1
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Prior art keywords
electret sheet
layer
electret
sheet
filter
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PCT/JP2023/007350
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English (en)
Japanese (ja)
Inventor
渉 佐藤
祐太郎 菅俣
洋介 廣井
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株式会社ユポ・コーポレーション
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Publication of WO2023163218A1 publication Critical patent/WO2023163218A1/fr

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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/28—Plant or installations without electricity supply, e.g. using electrets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/02—Physical, chemical or physicochemical properties
    • B32B7/025—Electric or magnetic properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G7/00—Capacitors in which the capacitance is varied by non-mechanical means; Processes of their manufacture
    • H01G7/02—Electrets, i.e. having a permanently-polarised dielectric

Definitions

  • the present invention relates to electret sheets and filters.
  • a filter using an electret sheet is known as a filter that collects foreign matter such as dust and dirt in the air.
  • a filter in which repeatedly-folded electret sheets and flat-plate electret sheets are alternately laminated, and has a flow passage cross-sectional ratio within a specific range (see, for example, Patent Document 1).
  • an electret sheet As the electret sheet, a nonwoven fabric made of a resin such as polypropylene that accumulates electric charge by charging treatment has been proposed (see, for example, Patent Document 2).
  • an electrostatic adsorption film having pores inside can also be used as an electret sheet that adsorbs dust and the like by electrostatic force because it has a structure that easily retains electric charges (see, for example, Patent Document 3).
  • filters that collect foreign substances such as dust and dirt in the air also collect mites, pollen, bacteria, viruses, etc. that exist in the environment in addition to foreign substances such as dust and dirt.
  • the bacteria, viruses, etc., collected by the filter are not inactivated, there is a concern that the bacteria may proliferate on the filter, or infection may occur due to viruses re-entrained from the filter.
  • functions such as antibacterial, antiviral and antifungal properties to the electret sheet.
  • a seat has been disclosed (see, for example, Patent Document 4).
  • coating agents are generally made by dispersing functional materials in binders containing polar groups. If such a coating agent is used, functions can be imparted, but there is a concern that electret properties such as charge retention may be deteriorated due to moisture absorption and the like.
  • An object of the present invention is to provide an electret sheet and a filter that have at least one functional property of antibacterial, antiviral, and antifungal properties and that are excellent in charge retention.
  • an electret sheet comprising a charging layer and a functional layer, wherein the functional layer is selected from the group consisting of antibacterial, antiviral, and antifungal
  • the present invention is as follows.
  • An electret sheet comprising a charging layer and a functional layer, the charging layer has a porous structure,
  • the functional layer contains a thermoplastic resin and a functional agent having at least one function selected from the group consisting of antibacterial, antiviral, and antifungal functions in a range of 1 to 40% by mass relative to the mass of the entire functional layer.
  • the electret sheet wherein the water vapor permeability coefficient of the electret sheet is 0.01 to 5.0 g ⁇ mm/m 2 ⁇ 24 hr.
  • the functional layer is a stretched resin film layer, The electret sheet according to any one of (1) to (3). (5) The electret sheet according to any one of (1) to (4), wherein the functional layer has a thickness of 0.1 to 10 ⁇ m. (6) The electret sheet according to any one of (1) to (5), containing the functional agent in a range of 0.01 to 3% by mass with respect to the mass of the entire electret sheet. (7) The electret sheet according to any one of (1) to (6), wherein the functional layer is a stretched resin film layer stretched in at least one direction.
  • the surface of the functional layer has an arithmetic mean roughness (Ra) of 0.01 to 5 ⁇ m according to JIS B0601:2003.
  • an electret sheet and a filter that have at least one functional property of antibacterial, antiviral, and antifungal properties and are excellent in charge retention.
  • FIG. 1 is a cross-sectional view showing the structure of an electret sheet according to an embodiment of the present invention
  • FIG. It is a figure which shows an example of an electret-ized apparatus.
  • FIG. 3 is a side view showing the three-dimensional structure of the filter of one embodiment of the present invention; It is a figure which shows an example of a corrugating apparatus.
  • FIG. 4 is a diagram showing a laminated sheet for flutes before processing;
  • FIG. 3 is a view showing a laminated sheet for flutes processed into a corrugated plate shape.
  • FIG. 3 is a view showing a flat laminated liner sheet laminated on a corrugated laminated flute sheet.
  • FIG. 3 is a diagram showing a powder supply bottle used for collection rate measurement in an example of the present invention.
  • FIG. 1 is a cross-sectional view showing the structure of an electret sheet according to one embodiment of the present invention.
  • the electret sheet of the present invention comprises a charged layer and a functional layer containing a functional agent having at least one function selected from the group consisting of antibacterial, antiviral, and antifungal functions on at least one side of the charged layer. have. As long as it is provided on at least one side, the electret sheet of the present invention can also have a functional layer on the other side of the charging layer.
  • the electret sheet of the present invention has a functional layer containing a functional agent, it has at least one functional property of antibacterial, antiviral, and antifungal properties.
  • the functional layer contains a thermoplastic resin, the strength of the functional layer can be increased and the environmental resistance can be improved.
  • the functional layer covers the surface of the charging layer, it is possible to suppress deterioration in electret performance such as charge retention due to moisture absorption.
  • one layer has the charge retention performance and the above functions by separating the charge retention performance into the charge layer and the antibacterial, antiviral, or antifungal functions into the functional layer. can have the functional agent concentrated in the functional layer. Therefore, the electret sheet of the present invention can obtain functions such as antibacterial, antiviral, or antifungal functions while suppressing the content of the functional agent in the entire electret sheet and obtaining an advantage in terms of cost.
  • the charging layer used in the present invention has a porous structure. Furthermore, in order to form a porous structure, the charging layer is preferably a resin layer obtained by stretching a filler-containing thermoplastic resin, and the stretching is preferably biaxial stretching.
  • the charged layer is formed by electretizing a porous structure such as a resin layer obtained by stretching a thermoplastic resin containing a filler, so that the charged layer retains electric charges on the surface or inside and is charged, and adsorbs foreign matter such as dust and dirt.
  • the electret sheet is provided with an electrostatic attraction force to be applied.
  • the porous structure of the charging layer facilitates control of the water vapor permeability coefficient within a desired range.
  • thermoplastic resin (A) that can be used as the charging layer is not particularly limited, but is a thermoplastic resin (A) having a low relative dielectric constant and excellent insulating properties because the charge accumulated in the charging layer is easily retained. is preferred.
  • thermoplastic resin (A) examples include high-density polyethylene, medium-density polyethylene, low-density polyethylene, propylene-based resins, polyolefin-based resins such as polymethyl-1-pentene; ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, Functional group-containing polyolefin resins such as polymers, maleic acid-modified polyethylene, and maleic acid-modified polypropylene; polyamide-based resins such as nylon-6 and nylon-6,6; polyethylene terephthalate and its copolymers, polybutylene terephthalate, aliphatic Thermoplastic polyester resins such as polyester; polycarbonate resins; polystyrene resins such as atactic polystyrene and syndiotactic polystyrene. Among them, polyolefin-based resins or functional group-containing polyolefin-based resins, which are excellent in insulating properties and
  • polystyrene resin examples include homopolymers of olefins such as ethylene, propylene, butylene, hexene, octene, butadiene, isoprene, chloroprene, methyl-1-pentene, and cyclic olefins; Examples include copolymers in which more than one type is combined.
  • the functional group-containing polyolefin resin include copolymers of the above-mentioned olefins and functional group-containing monomers that can be copolymerized.
  • functional group-containing monomers include styrenes such as styrene and ⁇ -methylstyrene; vinyl acetate, vinyl alcohol, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl caproate, vinyl laurate, and vinyl stearate; , vinyl benzoate, vinyl butyl benzoate, vinyl cyclohexanecarboxylate and other carboxylic acid vinyl esters; acrylic acid, methacrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acryl
  • the polyolefin-based resin and functional group-containing polyolefin-based resin can be used as a graft-modified product obtained by graft polymerization, if necessary.
  • a known method can be used to obtain the graft-modified product.
  • a specific example is a method of graft polymerization using an unsaturated carboxylic acid or a derivative thereof as a graft monomer.
  • the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid.
  • the unsaturated carboxylic acid derivatives include acid anhydrides, esters, amides, imides, and metal salts.
  • unsaturated carboxylic acid derivatives include maleic anhydride, itaconic anhydride, citraconic anhydride, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, (meth) Glycidyl acrylate, maleic acid monoethyl ester, maleic acid diethyl ester, fumaric acid monomethyl ester, fumaric acid dimethyl ester, itaconic acid monomethyl ester, itaconic acid diethyl ester, (meth)acrylamide, maleic acid monoamide, maleic diamide, maleic acid -N-monoethylamide, maleic acid -N,N-diethylmonoamide, maleic acid -N-monobutylamide, maleic acid -N,N-dibutylmonoamide, fumaric acid monoamide, fumaric acid diamide, fumaric acid -N-mono ethylamide, fuma
  • the ratio of the graft monomer graft-polymerized to the polyolefin-based resin and the functional group-containing polyolefin-based resin in the graft-modified product is not particularly limited, but is preferably in the range of 0.005 to 10% by mass, more preferably 0.01%. A range of ⁇ 5% by weight is preferred.
  • thermoplastic resin (A) contained in the charging layer may be selected from among the thermoplastic resins (A) and used alone, or two or more may be selected and used in combination. You may
  • polypropylene resins are preferred from the viewpoints of insulation, workability, water resistance, chemical resistance, cost, and the like.
  • the polypropylene-based resin may be isotactic, syndiotactic, or a propylene homopolymer exhibiting various degrees of stereoregularity, and propylene as a monomer as a main component (the proportion contained in the entire resin is 50% by mass or more), Copolymers obtained by copolymerizing ⁇ -olefins such as ethylene, 1-butene, 1-hexene, 1-heptene and 4-methyl-1-pentene can be mentioned.
  • the copolymer of propylene and ⁇ -olefin may be a binary system, a ternary system or higher, or a random copolymer block copolymer.
  • the polypropylene-based resins may be used singly or in combination of two or more.
  • a resin having a lower melting point than the polypropylene resin or propylene homopolymer is added to the total mass of the thermoplastic resin (A). It is preferable to use it by blending 2 to 25% by mass.
  • High-density or low-density polyethylene, etc. can be exemplified as such a resin having a low melting point.
  • the content of the thermoplastic resin (A) in the charging layer is preferably 50% by mass or more, more preferably 51% by mass or more, still more preferably 60% by mass or more, and 99% by mass with respect to the mass of the entire charging layer. % or less, and more preferably 95 mass % or less.
  • the amount of the thermoplastic resin (A) is 50% by mass or more, the charged layer is easily formed, and the obtained charged layer easily retains electric charge due to the insulating properties of the thermoplastic resin (A).
  • the thermoplastic resin (A) used in the charging layer preferably contains 50 to 98% by mass of a polypropylene resin and 1 to 49% by mass of a polyethylene resin with respect to the mass of the entire charging layer. More preferably, it contains 50 to 96% by mass and 3 to 29% by mass of polyethylene resin.
  • fillers used in the charging layer include inorganic fillers and organic fillers. These may be used singly or in combination of two or more.
  • voids are formed in the charging layer to increase the interface (surface area) between the thermoplastic resin (A) and the air, thereby improving the chargeability of the charging layer. easier to improve.
  • the surface of the charging layer can be roughened by forming undulations (projection structure) caused by the inorganic filler or the organic filler on the surface of the charging layer. By roughening the surface, the surface area of the charging layer increases, and as a result, the adsorption area of the electret sheet increases, so that the dust collecting effect of the filter can be enhanced.
  • the inorganic filler examples include calcium carbonate, calcined clay, silica, diatomaceous earth, clay, talc, titanium oxide, barium sulfate, alumina, zeolite, mica, sericite, bentonite, sepiolite, vermiculite, dolomite, wollastonite, and glass fiber.
  • heavy calcium carbonate, light calcium carbonate, calcined clay or talc is preferable because of good pore moldability and low cost.
  • the organic filler it is preferable to select an organic filler made of a resin different from the thermoplastic resin (A), which is the main component of the charging layer. It is preferable to select an organic filler composed of a resin having a melting point or a resin having a glass transition point higher than that of the thermoplastic resin (A) and incompatible with the plastic resin.
  • the organic filler include polyethylene terephthalate, polybutylene terephthalate, polycarbonate, nylon-6, nylon-6,6, cyclic polyolefin, polystyrene, and polymethacrylate when the thermoplastic resin (A) is a polyolefin resin. , which have a higher melting point (eg, 170 to 300° C.) or a glass transition temperature (eg, 170 to 280° C.) than the melting point of the polyolefin resin.
  • the volume average particle size of the filler measured by a particle size distribution meter using laser diffraction is preferably 0.1 ⁇ m or more, more preferably 0.5 ⁇ m or more, and even more preferably 1 ⁇ m or more.
  • the volume average particle size of the filler is preferably 30 ⁇ m or less, more preferably 20 ⁇ m or less, still more preferably 10 ⁇ m or less, and particularly preferably 5 ⁇ m or less.
  • the volume average particle size of the filler is preferably in the range of 0.1 to 30 ⁇ m, more preferably in the range of 0.5 to 20 ⁇ m, preferably in the range of 1 to 10 ⁇ m, particularly in the range of 1.0 to 5.0 ⁇ m. preferable.
  • the volume average particle diameter of the filler is 0.1 ⁇ m or more, it is preferable in terms of easiness of formation of pores in the charging layer. It is preferable in terms of improvement in durability and chargeability.
  • the amount of the filler compounded in the charging layer is preferably 1% by mass or more, more preferably 5% by mass or more, from the viewpoint of moldability of pores in the charging layer. From the viewpoints of ease of control of the charge amount of the charged layer and durability of the dust collecting effect of the filter, the content is preferably 49% by mass or less, more preferably 40% by mass or less.
  • the charging layer may contain additives such as metallic soaps, heat stabilizers (antioxidants), light stabilizers, dispersants, and lubricants, if necessary.
  • the charging layer contains a metal soap
  • its content is preferably in the range of 0.01 to 10.0% by mass relative to the mass of the charging layer as a whole.
  • metal soaps include dihydroxyaluminum octadecanoate, hydroxyaluminum dioctadecanoate, aluminum trioctadecanoate, dihydroxyaluminum dodecanoate, hydroxyaluminum didodecanoate, aluminum tridodecanoate, dihydroxyaluminum 2-ethylhexanoate, and di-2-ethyl.
  • saturated higher fatty acid aluminum salts such as hydroxyaluminum hexanoate and aluminum tri-2-ethylhexanoate.
  • the charging layer contains a heat stabilizer
  • its content is preferably in the range of 0.001 to 1% by mass with respect to the mass of the charging layer as a whole.
  • heat stabilizers include bulky phenol-based, phosphorus-based, and amine-based stabilizers.
  • the charging layer contains a light stabilizer
  • its content is preferably in the range of 0.001 to 1% by mass with respect to the mass of the charging layer as a whole.
  • light stabilizers include bulky amine-based, benzotriazole-based, and benzophenone-based light stabilizers.
  • a dispersant or lubricant can be contained, for example, for the purpose of dispersing a filler added to the charging layer.
  • the content thereof is preferably in the range of 0.01 to 4% by weight based on the weight of the entire charging layer.
  • dispersants or lubricants include silane coupling agents, higher fatty acids such as oleic acid and stearic acid, polyacrylic acid, polymethacrylic acid, and salts thereof.
  • the charging layer may have a single layer structure or a multilayer structure.
  • the multi-layered charging layer has improved withstand voltage performance when electret is injected, improved function to contain the injected charge so that it does not escape to the outside, suitability for secondary processing such as bonding between electret sheets, Various functions such as antistatic properties can be imparted.
  • the charging layer is preferably film-formed by extrusion.
  • extrusion molding for example, an extruder set to a temperature higher than the melting point or glass transition temperature of the charging layer is used to melt and knead the raw material of the charging layer.
  • sheet molding that cools with a rubber roll, metal belt, etc.
  • inflation molding that cools with air or water while extruding into a tube shape using a circular die and inflating it to a certain magnification by the internal pressure inside the tube.
  • a roll having an uneven surface may be used as a cooling metal roll or rubber roll to roughen the surface. Roughening the surface increases the adsorption area of the electret sheet, thereby improving the dust collecting effect of the filter.
  • molding methods for charging layers with a multilayer structure include a feed block, a multilayer die method using a multi-manifold, and an extrusion lamination method using multiple dies. It is also possible to combine the multi-layer die method and the extrusion lamination method.
  • the charging layer may be a non-stretched film or a stretched film, but is preferably a stretched film stretched in at least one direction. Thereby, the uniformity of the thickness of the charging layer can be improved. If the uniformity of the thickness of the charged layer is high, it is possible to reduce the local concentration of discharge at thin portions under high voltage during electretization, and to improve the uniformity of the electrical properties of the charged layer.
  • the stretching of the film can be carried out by any of various commonly used methods.
  • the charged layer is a single layer, it is preferably a layer formed by uniaxial stretching or biaxial stretching.
  • One including a laminated structure is mentioned.
  • Stretching methods include longitudinal stretching using a difference in circumferential speed between rolls, transverse stretching using a tenter oven, sequential biaxial stretching by combining longitudinal stretching and transverse stretching, rolling, and simultaneous 2 stretching by combining a tenter oven and a linear motor.
  • Axial stretching, simultaneous biaxial stretching using a combination of a tenter oven and a pantograph, and the like can be mentioned.
  • a method for stretching the blown film includes simultaneous biaxial stretching by a tubular method.
  • the longitudinal direction is the machine direction (MD) of the film
  • the transverse direction is the width direction (TD) of the film.
  • the draw ratio is not particularly limited, and is appropriately determined in consideration of the properties of the thermoplastic resin (A) used for the charging layer.
  • the draw ratio is usually 1.2 to 12 times, preferably 2 to 10 times. is.
  • the area magnification is usually 1.5 to 60 times, preferably 4 to 50 times.
  • the stretch ratio is usually 1.2 to 10 times, preferably 2 to 5 times, and the area ratio in the case of biaxial stretching is , usually 1.5 to 20 times, preferably 4 to 12 times.
  • the stretching temperature is in the range of not less than the glass transition temperature of the thermoplastic resin (A) mainly used in the charging layer and not more than the melting point of the crystalline portion, and can be performed within a known temperature range suitable for the thermoplastic resin (A). can.
  • the thermoplastic resin (A) of the charging layer is a propylene homopolymer (melting point 155-167°C), it is 100-166°C, and when it is a high-density polyethylene (melting point 121-136°C), it is 70-100°C. 135° C., which is 1 to 70° C. lower than the melting point.
  • the drawing speed is preferably 20 to 350 m/min.
  • the functional layer contained in the electret sheet of the present invention comprises a thermoplastic resin (B) and a functional agent having at least one function selected from the group consisting of antibacterial, antiviral, and antifungal functions, which is added to the mass of the entire functional layer. It is contained in the range of 1 to 40% by mass.
  • the functional layer provides the electret sheet with at least one functional property of antibacterial, antiviral, and antifungal properties.
  • the electret sheet of the present invention is used as a filter, the electret sheet is formed on the charging layer by providing the functional layer on the surface of the charging layer on the opposite side of the air flow direction to form a laminated structure.
  • the voids communicate with the outside, making it easy to prevent the electric charge stored inside from being discharged to the atmosphere, improving the surface strength of the electret sheet, and electret performance such as charge retention due to moisture absorption. decline can be suppressed.
  • the functional layer contains a functional agent having at least one function selected from the group consisting of antibacterial, antiviral, and antifungal functions, as described above.
  • antibacterial refers to, for example, sterilization, damage, or growth prevention of bacteria and fungi
  • antiviral refers to, for example, inactivation of viruses.
  • antifungal indicates, for example, the prevention of the occurrence or growth of mold.
  • the functional agent having at least one of antibacterial, antiviral, and antifungal properties is not particularly limited, and known agents can be used.
  • Functional agents include, for example, quaternary ammonium salts, metal supports, photocatalysts, shell powder, calcined shell powder, aldehyde compounds, iodine compounds, piguanide compounds, and acrinol hydrates (e.g., 6,9-diamino lactic acid -2-ethoxyacridine monohydrate) and the like.
  • a metal carrier, shell powder, or calcined shell powder is preferable in that it is easy to hold an electric charge for a long period of time, is easy to handle, is highly safe, and is easily available. Calcined shell powder is more preferred.
  • the metal support is composed of a metal and a support that supports the metal.
  • metals include gold, silver, copper, zinc, iron, bismuth, titanium, and nickel.
  • the form of the metal contained in the metal-containing antibacterial agent is not particularly limited, and examples thereof include forms of metal particles, metal ions, and metal salts (including metal complexes).
  • the metal is preferably gold, silver, or copper from the viewpoint of obtaining superior antibacterial, antiviral, or antifungal properties.
  • the metal carrier is preferably a silver carrier.
  • Silver in the silver carrier is specifically silver salts such as silver nitrate, silver chloride, silver sulfate, silver lactate, and silver acetate; silver complexes such as silver ammonia complex, silver chloro complex, and silver thiosulfato complex; silver particles; or can be silver ions.
  • a photocatalyst is a substance that exhibits photocatalytic action.
  • photocatalysts include, but are not limited to, SrTiO 2 , ZnO, CdS, SnO 2 and WO 3 .
  • shell powder and baked shell powder include scallop powder and oyster powder.
  • Aldehyde compounds are not particularly limited, but include, for example, glutaral, phthalal, and formalin.
  • the iodine-based compound is not particularly limited, but examples include povidone-iodine and iodine tincture.
  • piguanide compound is not particularly limited, examples thereof include chlorhexidine gluconate, chlorhexidine hydrochloride, and chlorhexidine acetate.
  • the content of the functional agent in the functional layer is 1% by mass or more with respect to the mass of the entire functional layer from the viewpoint of more reliably exhibiting functions such as antibacterial, antiviral, and antifungal properties, 2% by mass or more is preferable, 3% by mass or more is more preferable, and 4% by mass or more is even more preferable.
  • the content of the functional agent in the functional layer is 40% by mass or less, preferably 30% by mass or less, relative to the mass of the entire functional layer from the viewpoint of maintaining the strength and environmental resistance of the functional layer. , is more preferably 15% by mass or less, more preferably 7% by mass or less, and particularly preferably 5% by mass or less.
  • the content of the functional agent is the amount of calcium hydroxide contained in the shell powder or calcined shell powder.
  • the content of the functional agent in the entire electret sheet is 0.01% by mass with respect to the mass of the entire electret sheet from the viewpoint of more reliably exhibiting functions such as antibacterial, antiviral, and antifungal properties. 0.05% by mass or more is more preferable, and 0.1% by mass or more is even more preferable.
  • the content of the functional agent in the entire electret sheet is preferably 5% by mass or less, more preferably 3% by mass or less, and 1% by mass relative to the mass of the entire electret sheet, from the viewpoint of cost reduction and charge retention. % or less is more preferable.
  • the functional layer contains a thermoplastic resin (B).
  • the thermoplastic resin (B) is not particularly limited, but from the viewpoint of stretchability and interlayer strength with the charging layer, the same type of resin as that of the charging layer is preferable. Specifically, a polyolefin resin is used. is preferred. As the polyolefin-based resin, for example, the same specific examples as exemplified in the item of the charging layer can be mentioned, and among them, the polypropylene-based resin is preferable. Examples of the polypropylene-based resin include those similar to the specific examples given in the section on the charging layer.
  • the content of the thermoplastic resin (B) in the functional layer is preferably 60% by mass or more, more preferably 70% by mass, relative to the mass of the entire functional layer. It is more preferably 80% by mass or more, and particularly preferably 90% by mass or more.
  • the functional layer may or may not contain an inorganic filler or an organic filler, but it is preferable to contain it from the viewpoint of modifying the electrical properties such as the dielectric constant of the functional layer.
  • the inorganic filler or organic filler include those exemplified in the charge layer section. Among them, the inorganic filler is suitable for modifying the electrical properties of the functional layer because it generally has a higher dielectric constant than the thermoplastic resin (B).
  • thermoplastic resin (B) of the functional layer when a resin with a low dielectric constant such as a polyolefin resin is used as the thermoplastic resin (B) of the functional layer, the inclusion of the inorganic filler allows the dielectric effect of the inorganic filler during electretization to increase the charge to the charging layer. can be reached, which is preferable.
  • the functional layer may contain additives such as heat stabilizers (antioxidants), light stabilizers, dispersants, and lubricants, if necessary. Examples of these additives are the same as those exemplified in the charge layer section.
  • the functional layer may be a non-stretched film layer or a stretched film layer, but from the viewpoint of improving thickness uniformity, it is preferably a stretched film layer stretched in at least one direction.
  • a high thickness uniformity can reduce the local concentration of discharge to a thin portion under a high voltage during electretization, and improve the uniformity of the electrical properties of the functional layer.
  • the stretching method, stretching ratio, stretching temperature, etc. of the functional layer are, for example, the same as those exemplified in the section on the charging layer.
  • the functional layer can have a porous structure like the charging layer. Having a porous structure makes it easier for the functional agent to be exposed on the surface of the electret sheet, making it easier for the effect of the functional agent to manifest. Moreover, it is preferable that the functional layer has a structure with a lower porosity than the charging layer.
  • Such formation of the functional layer can be achieved by making the filler content smaller than that of the charging layer, or by making the volume average particle diameter of the filler used in the functional layer smaller than that of the filler used in the charging layer. It can be achieved by a method of forming the charging layer by biaxial stretching and forming the functional layer by uniaxial stretching, etc., to make a difference between the two stretch ratios.
  • the functional layer may have not only a single-layer structure but also a multi-layer structure of two or more layers.
  • the electret sheet having better functional properties and charge retention properties by changing the type and content of the thermoplastic resin (B), filler, and functional agent used in each layer. can be
  • the composition, configuration, thickness, etc. of the functional layers may be the same or different.
  • the electret sheet of the present invention is obtained by subjecting a sheet obtained by laminating the charged layer and the functional layer (hereinafter sometimes referred to as a laminated sheet) to an electret treatment to retain an electric charge on the surface or inside of the laminated sheet. can get.
  • the lamination sheet can be formed by a multilayer die method using a feed block or a multi-layer die, an extrusion lamination method in which the functional layer is laminated on the charged layer, or the functional layer separately prepared on the charged layer via an adhesive. It can be produced by a dry lamination method or the like. Among them, the multi-layer die method and the extrusion lamination method are preferable because the functional layer having good chargeability can be easily obtained. When each layer of the laminated sheet is film-formed independently, it can be film-formed in the same manner as the charging layer described above.
  • the laminated sheet preferably has a layer stretched in at least one direction.
  • the laminated sheet may be obtained, for example, by laminating the functional layer on the charged layer stretched in the longitudinal direction, or by laminating the functional layer on the charged layer stretched in the longitudinal direction, followed by A laminated sheet having layers stretched uniaxially/biaxially (functional layer/charging layer) may be obtained by stretching the film in the direction of 100 degrees.
  • Preferred stretching method, stretching ratio, stretching temperature and other conditions are the same as those for the charging layer described above.
  • the laminate sheet may be electretized before, after, or during the filter manufacturing process, which will be described later.
  • the configuration of the electretization apparatus becomes complicated. Therefore, from the viewpoint of electretization by a simple-structured device, it is preferable to electretize the laminated sheet in advance and use the obtained electret sheet to form a filter.
  • the electretization method is not particularly limited, and can be carried out according to known methods.
  • an electro electret method in which a corona discharge is applied to the surface of the laminated sheet or a pulsed high voltage is applied, a method in which both surfaces of the laminated sheet are held by a dielectric and a DC high voltage is applied to both surfaces, and a ⁇ -ray is applied to the laminated sheet.
  • a radio electret method in which ionizing radiation such as an electron beam is applied.
  • Electro electret method for example, a batch method in which the laminated sheet is fixed between an application electrode connected to a DC high-voltage power supply and a ground electrode, or a conveying method in which the laminated sheet is passed through is preferred.
  • the electro-electretization method it is preferable to use needle-like electrodes arranged at equal intervals or to use metal wires, and to use a flat metal plate or a metal roll as the ground electrode.
  • FIG. 2 shows an example of a batch-type electretization apparatus used for DC corona discharge treatment.
  • the electretization device 70 has a direct current high voltage power source 71 connected to a needle-like main electrode (applying electrode) 72 and a plate-like counter electrode (earth electrode) 73 .
  • the sheet 10 to be electretized (for example, the above-mentioned laminated sheet) is placed between the main electrode 72 and the counter electrode 73 .
  • a high DC voltage is applied between the main electrode 72 and the counter electrode 73 by the DC high voltage power source 71 to generate corona discharge, thereby injecting charge into the sheet 10 .
  • the distance between the main electrode and the counter electrode is preferably 1 mm or more, more preferably 2 mm or more, and even more preferably 5 mm or more, because the longer the distance between the electrodes, the easier it is to maintain a uniform distance between the electrodes.
  • the distance between the main electrode and the counter electrode is preferably 50 mm or less, more preferably 30 mm or less, and even more preferably 20 mm or less, because the shorter the distance between the main electrode and the counter electrode, the easier it is for corona discharge to occur and the easier it is to improve the uniformity of the charging property of the charging layer.
  • the distance between the main electrode and the counter electrode is preferably 1 to 50 mm, more preferably 2 to 30 mm, even more preferably 5 to 20 mm.
  • the voltage applied between the main electrode and the counter electrode depends on the electrical properties such as the insulation of the charged layer, the surface potential required for the electret sheet, the electrical properties such as the dielectric constant, the shape and material of the main electrode and the counter electrode, the main It is determined by the distance between the electrode and the counter electrode.
  • the amount of charge introduced into the charged layer by DC corona discharge treatment depends on the amount of current flowing through the main and counter electrodes during treatment. The amount of current increases as the voltage between both electrodes increases. Therefore, when a higher treatment effect is desired, the applied voltage is preferably set to a level high enough not to cause dielectric breakdown of the charged layer.
  • the applied voltage is specifically preferably 1 to 100 kV, more preferably 3 to 70 kV, still more preferably 5 to 50 kV, and particularly preferably 10 to 30 kV. .
  • the polarity on the main electrode side may be positive or negative, but it is preferable to make the main electrode side negative because relatively stable corona discharge treatment can be performed.
  • Materials for the main electrode and the counter electrode are appropriately selected from conductive substances, but metals such as iron, stainless steel, copper, brass, and tungsten or carbon materials are usually used.
  • the laminated sheet may be subjected to static elimination treatment after electretization.
  • static elimination treatment By temporarily reducing or removing the surface charge in the static elimination process, it is easy to avoid the adsorption of dust, sticking between sheets, sticking between sheets and manufacturing equipment, etc. in the manufacturing process including processing from electret sheets to filters.
  • a known static eliminator such as a voltage application type static eliminator (ionizer) or a self-discharge type static eliminator can be used for the static elimination process. These general static eliminators can reduce or remove the charge on the surface of the sheet, but they cannot remove the charge accumulated inside the sheet. no.
  • the thickness of the charging layer is preferably 10 ⁇ m or more, more preferably 20 ⁇ m or more, still more preferably 30 ⁇ m or more.
  • the thicker the charging layer the more charge can be accumulated in the charging layer, and the easier it is to obtain an electret sheet with excellent charge retention.
  • the thickness of the charging layer is preferably 300 ⁇ m or less, more preferably 200 ⁇ m or less, and more preferably 100 ⁇ m or less. The thinner the charged layer, the less likely the voids are to be crushed during corrugation or other bending to form a corrugated sheet, and the easier it is to corrugate with fine pitches, making it easier to obtain a filter with a high dust collecting effect.
  • the functional layer is preferably thinner than the charging layer. Since the functional layer is a layer that is relatively resistant to elastic deformation in the thickness direction as compared to the charging layer, by suppressing the thickness of the functional layer, the compression elastic modulus of the laminated sheet does not decrease, and the energy conversion efficiency is improved. easier to maintain.
  • the thickness of the functional layer is preferably 0.1 ⁇ m or more, more preferably 1 ⁇ m or more, still more preferably 2 ⁇ m or more. On the other hand, the thickness of the functional layer is preferably 10 ⁇ m or less, more preferably 9 ⁇ m or less, still more preferably 5 ⁇ m or less.
  • the thickness of the functional layer When the thickness of the functional layer is 0.1 ⁇ m or more, functions such as antibacterial, antiviral, and antifungal properties tend to be exhibited more easily. Further, when the thickness of the functional layer is 10 ⁇ m or less, the charge tends to reach the charged layer inside the film when the charge is injected into the laminated sheet, and the charging property tends to be excellent.
  • the ratio of the thickness of the charging layer to the thickness of the functional layer is preferably 1.1 to 1000, more preferably 2 to 300, and more preferably 5 to 150. is more preferred, and 10-50 is particularly preferred.
  • the charging layer and the functional layer have a multi-layer structure, the same value is converted from the total value of each layer constituting the charging layer or the functional layer.
  • the thickness of the electret sheet is preferably 20 ⁇ m or more, more preferably 30 ⁇ m or more, and even more preferably 40 ⁇ m or more.
  • the thicker the electret sheet the easier it is to maintain its shape when corrugated, and the easier it is to obtain an electret sheet with excellent workability.
  • the thickness of the electret sheet is preferably 400 ⁇ m or less, more preferably 300 ⁇ m or less, and even more preferably 200 ⁇ m or less. When the electret sheet is thin, it can be easily bent by corrugating or the like, and a filter with a stable shape can be easily obtained.
  • the thickness of the electret sheet is measured using a thickness meter in accordance with JIS-K7130:1999. Moreover, the thickness of each layer constituting the electret sheet can be measured as follows. The sample to be measured is cooled to ⁇ 60° C. or below with liquid nitrogen. A razor blade (manufactured by Sic Japan Co., Ltd., trade name: Proline blade) is applied at right angles to the sample placed on the glass plate to cut it, thereby preparing a sample for cross-sectional observation. Using a scanning electron microscope (manufactured by JEOL Ltd., trade name: JSM-6490), a cross-sectional image of the obtained sample is observed, and the boundary lines of each layer are determined from the pore shape and compositional appearance.
  • a scanning electron microscope manufactured by JEOL Ltd., trade name: JSM-6490
  • the thickness ratio of each layer to the total thickness of the electret sheet is calculated.
  • the thickness of each layer is obtained from the total thickness of the electret sheet measured with a thickness meter, the magnification ratio of the cross-sectional image, and the thickness ratio of each layer.
  • the charging layer preferably has a porosity of 1 to 70%.
  • the porosity is obtained from the ratio of the area occupied by pores in a certain region of the cross section of the electret sheet observed with an electron microscope. Since the electret sheet has pores inside, it is easy to confine the charge inside the electret sheet including the pores, and since the charge is difficult to escape from the electret sheet, the collection efficiency is high and the collection power is maintained. It is easy to obtain a filter with excellent properties. In addition, having pores inside the electret sheet leads to a decrease in the density of the electret sheet, and is therefore preferable from the viewpoint of weight reduction of the resulting filter.
  • the porosity of the charging layer is preferably 1% or more, more preferably 5% or more, and still more preferably 25% or more. The higher the porosity, the slower the charge attenuation speed, and the longer the filter performance is likely to improve.
  • the porosity of the charging layer is preferably 70% or less, more preferably 60% or less, and still more preferably 55% or less. The smaller the porosity, the fewer the holes communicating with each other, and the more the charge retention capacity tends to improve. Therefore, the porosity of the charging layer is preferably 1 to 70%, more preferably 5 to 60%, still more preferably 25 to 55%, as described above. By controlling the porosity within the above range, the dust adsorption force tends to be stable.
  • the true density ⁇ 0 of the charged layer is obtained by using a compression molding machine set at a temperature 10° C. to 150° C. higher than the melting point or glass transition temperature of the thermoplastic resin (A) constituting the charged layer. After heating and compressing the charged layer at a pressure of 3 MPa or higher for 3 minutes or longer, it is cooled for 3 minutes or longer at a pressure of 3 MPa or higher in a compression molding machine set at 25° C. or lower to remove pores in the charged layer. After conditioning for 24 hours or more using an oven set to a temperature 10° C. to 70° C. lower than the melting point or glass transition temperature of the thermoplastic resin (A) used in the charging layer, the temperature is 23° C. and relative humidity. Conditioning is performed for 24 hours or more in a 50% environment, and measurement is performed by the method described in JIS-K-7112:1999.
  • the bending resistance of the electret sheet is preferably 0.1 to 1 mN, more preferably 0.12 to 0.8 mN, still more preferably 0.13 to 0.7 mN. If the bending resistance is 0.1 mN or more, the eclaret sheet itself has stiffness and is easy to handle. On the other hand, when the bending resistance is 1 mN or less, high transportability is likely to be obtained.
  • the bending resistance in the present invention is measured according to the bending resistance A method (Gurley method) according to JIS L1096:2010.
  • the functional layer preferably has a volume resistivity of 1 ⁇ 10 13 to 9 ⁇ 10 17 ⁇ cm, more preferably 1 ⁇ 10 14 to 9 ⁇ 10 15 ⁇ cm.
  • the volume resistivity of the functional layer is 1 ⁇ 10 13 ⁇ cm or more, the charge imparted during electretization is less likely to migrate along the film surface, thereby suppressing a decrease in the efficiency of charge injection into the charging layer. Cheap.
  • it is easy to suppress a decrease in charge density on the surface of the electret sheet, a decrease in space charge density, and a decrease in electrostatic adsorption performance.
  • the energy required for electretization can be reduced.
  • the volume resistivity of the functional layer is 9 ⁇ 10 17 ⁇ cm or less, it is easy to form such a highly insulating surface using a known material and to reduce the cost.
  • the surface resistivity of the functional layer is within the desired range by using a polyolefin resin with excellent insulating properties as the thermoplastic resin (B), adjusting the type or amount of the inorganic filler blended in the thermoplastic resin (B), etc. can be adjusted to In addition, the volume resistivity in the present invention is measured according to JIS K6911:2006.
  • the water vapor permeability coefficient of the electret sheet determines the presence or absence of communicating pores. If the water vapor permeability coefficient is large, the electric charge is easily discharged by the surface of the communicating pores and the intervening water vapor.
  • the water vapor permeability coefficient of the electret sheet of the present invention is preferably 5.0 g ⁇ mm/m 2 ⁇ 24 hr or less, more preferably 4.0 g ⁇ mm/m 2 ⁇ 24 hr or less, and 3.0 g ⁇ mm/m 2 ⁇ 24 hr.
  • each layer constituting the electret sheet contains a thermoplastic resin, for example, a film made of a polyolefin resin has a water vapor transmission coefficient of about 0.1 g ⁇ mm/m 2 ⁇ 24 hr, the water vapor transmission of the electret sheet is
  • the modulus is usually 0.01 g ⁇ mm/m 2 ⁇ 24 hr or more, may be 0.05 g ⁇ mm/m 2 ⁇ 24 hr or more, and may be 0.1 g ⁇ mm/m 2 ⁇ 24 hr or more. good.
  • the water vapor permeability coefficient (g mm/ m 2 24 hr) is determined by the cup method in accordance with JIS-Z-0208:1976 at a temperature of 40 ° C and a relative humidity of 90%. ) is measured and converted from the thickness (mm) of the sheet.
  • the functional layer of the electret sheet has an insulating effect so that the charge accumulated in the charged layer does not escape to the outside. becomes. Further, when many of the pores in the electret sheet are interconnected, the water vapor permeability coefficient similarly increases, resulting in poor charge retention capability.
  • the arithmetic mean roughness (Ra) of the surface of the functional layer is preferably 5 ⁇ m or less, more preferably 4 ⁇ m or less. preferable.
  • the surface of the electret sheet preferably has unevenness from the viewpoint of retaining foreign substances adsorbed by the filter, and the unevenness is preferably formed by exposing the functional agent to the surface of the electret sheet. preferable. Therefore, the arithmetic mean roughness (Ra) of the surface of the functional layer is preferably 0.01 ⁇ m or more, more preferably 0.03 ⁇ m or more.
  • the material itself is selected within the above range, or the surface is undulated within the above range by embossing or texturing. preferably added.
  • the arithmetic mean roughness (Ra) in the present invention is measured according to JIS-B-0601:2003.
  • the electret sheet is a member constituting the filter and has a role of confining electric charges so that they do not escape to the outside of the filter.
  • the charge confinement ability can be represented by the dielectric constant ⁇ of the electret sheet (the ratio ⁇ B/ ⁇ 0 of the dielectric constant ⁇ B of the electret sheet to the dielectric constant ⁇ 0 of vacuum).
  • the dielectric constant of the electret sheet can be set to a lower desired range by including an insulating resin with a low dielectric constant or by forming pores inside the electret sheet.
  • the dielectric constant of the electret sheet is preferably 1.1 or higher, more preferably 1.2 or higher, and even more preferably 1.25 or higher.
  • the dielectric constant of the electret sheet is preferably 2.5 or less, more preferably 2.2 or less, still more preferably 2.0 or less, and particularly preferably 1.9 or less.
  • the smaller the relative dielectric constant the easier it is for the electret sheet to retain electric charge for a longer period of time, and the less the electrostatic adsorption force of the filter tends to decrease.
  • the method for measuring the dielectric constant of the electret sheet is selected according to the range of measurement frequencies.
  • Ultra-low frequency bridges are used for measurement frequencies below 10 Hz
  • transformer bridges are used for measurement frequencies between 10 Hz and 3 MHz
  • parallel T bridges high frequency Schering bridges
  • Q-meters Q-meters
  • resonant method standing wave method
  • cavity resonance method etc.
  • It can also be measured by an LCR meter or the like that measures the voltage/current vector for the circuit component with respect to the AC signal of the measurement frequency and calculates the capacitance from this value.
  • a device for measuring the dielectric constant of the electret sheet a device that can apply a voltage of about 5 V and can arbitrarily select a measurement frequency is preferable. According to such a measuring device, by changing the frequency, the frequency dependence of the sample can be grasped, and can be used as an index of the proper usage range. Examples of such measuring devices include "4192A LF Impedance Analyzer” from Agilent Technologies, "LCR Meter 4274A” from Yokogawa Electric Corporation, and "Hioki 3522 LCR High Tester” from Hioki Electric Corporation. mentioned.
  • both sides of the sheet are coated with a silver conductive paint or vacuum metal vapor deposition is performed to form electrodes to obtain a sample. Then, a voltage of 5 V is applied to the sample under environmental conditions of a temperature of 23 ° C. and a relative humidity of 50%, the capacitance (Cx) is measured at a frequency of 10 Hz to 1 MHz, and the capacitance (Cx) at a frequency of 100 kHz. Measurements are taken as representative values. From the obtained capacitance (Cx), the dielectric constant ( ⁇ r) is calculated by the following formula.
  • ⁇ r Cx ⁇ h / ( ⁇ 0 ⁇ A) ⁇ r: Relative permittivity of electret sheet (-)
  • A: Area of main electrode 3.848 ⁇ 10 -4 (m 2 )
  • the surface potential (static surface potential EA) of the electret sheet immediately after corona treatment is preferably 0.3 kV or more, more preferably 1.0 kV or more, preferably 15 kV or less, and more preferably 10 kV or less. preferable.
  • the surface potential (static surface potential EA) when the electret sheet is left for one week in an environment of 40° C. and 50% RH is preferably 0.3 kV or more, preferably 1.0 kV or more. is more preferably 15 kV or less, and more preferably 10 kV or less.
  • the surface potential measuring instrument for example, "Keyence Corporation, high-precision static electricity sensor SK" or “Trek Japan Corporation, high-voltage high-speed surface potential meter Model 341B" is used.
  • the measurement is performed in an environment of 23° C. and relative humidity of 50% so as not to be affected by temperature and humidity.
  • the electret sheet is suspended in the middle so as not to be affected by surrounding articles.
  • the corrugated electret sheets and the flat electret sheets are alternately laminated to form air flow paths, and the laminated electret sheets are heat-sealed to each other. have a joint. Since the electret sheet used in the filter is the electret sheet, it has at least one functional characteristic of antibacterial, antiviral, and antifungal properties, and is excellent in charge retention.
  • FIG. 3 shows the configuration of a filter that is one embodiment of the present invention.
  • the filter 50 of the present embodiment is formed by alternately and repeatedly laminating corrugated electret sheets 11 and flat electret sheets 11 . Due to the three-dimensional structure of each of the corrugated and flat electret sheets 11, the filter 50 is provided with a space serving as an air flow path.
  • the filter 50 has joints 11a in which the electret sheets 11 are heat-sealed to each other at their contact portions.
  • the three-dimensional structure of the filter provided with air flow paths can be formed by corrugating or the like.
  • the heat-seal layer (B) at the portion where the laminated electret sheets are in contact is heat-sealed to join the sheets and fix the three-dimensional structure of the filter.
  • the joining method is not particularly limited.
  • the electret sheets are laminated during corrugating, and the surface of the sheets is heated with a heated pressure roll to heat-seal the contact portions of the adjacent electret sheets to form a joining portion. can be done.
  • the cut portions can be heat-sealed.
  • a corrugating machine such as a honeycomb machine used for manufacturing a normal paper honeycomb core, a single facer used for manufacturing a normal paper corrugated board, etc. It can be manufactured by using it appropriately.
  • the electret sheet When using a single facer used for manufacturing paper cardboard, the electret sheet is supplied between a pair of meshed gears and bent to be corrugated into a corrugated sheet. Next, on one or both sides of the corrugated corrugated sheet (hereinafter sometimes referred to as "flute"), the flat plate electret sheet (hereinafter sometimes referred to as "liner") that is not corrugated A corrugated core is obtained by heat-sealing (a). At this time, another resin sheet melt-extruded from a T-die may be used as the liner, but from the viewpoint of improving the space charge density of the filter, it is possible to use the electret sheet as in the case of the flute. more preferred.
  • the air channel cross-sectional ratio of the filter is the ratio of the air channel to the cross section of the filter. Therefore, the lower the cross-sectional ratio of the flow path, the stronger the filter, and the more the pressure loss tends to increase due to the resistance to the flow of air.
  • the cross-sectional area of the air flow path is obtained by dividing the cross-sectional area of the sheet substrate, which is the product of the thickness of the sheet substrate and the length of the sheet substrate used for forming the flow path, from the cross-sectional area of the filter. is obtained by Further, the flow channel cross-sectional ratio can also be obtained from image observation of the cross section.
  • the air passage cross-sectional ratio of the filter is preferably 10% or more, more preferably 30% or more, and even more preferably 50% or more.
  • the air channel cross-sectional ratio of the filter is preferably 99% or less, more preferably 97% or less, and even more preferably 95% or less.
  • the spatial charge density of the filter indicates the total amount of charge that occupies the spatial volume of the filter. Space charge density shows that the higher the value, the higher the dust and dust collection performance.
  • the space charge density of the filter is obtained by dividing the charge amount of the sheet base material of the filter by the space volume formed by the sheet base material.
  • the amount of charge possessed by the sheet base material of the filter may be obtained by using an actually measured value, and the spatial volume may be obtained logically from the shape of the filter, or may be obtained from the density of the filter.
  • the unit space is defined as a cube of 1 cm long ⁇ 1 cm wide ⁇ 1 cm high.
  • the total length Ls (cm/cm 2 ) of the electret sheet existing per square (unit area) of 1 cm long ⁇ 1 cm wide cross section cut perpendicular to the flow path of the electret filter is obtained by calculating or measuring from the shape of the filter. .
  • the total area Ss (cm 2 /cm 3 ) of the electret sheets existing per unit space volume is obtained by adding the total length Ls of the electret sheets existing per square cross section (unit area) to the depth of the unit space as the width of the sheet. Since it is a multiplied value, Ss and Ls have the same value as expressed by the following equation.
  • the charge amount Qs (nC/cm 2 ) per unit area of the electret sheet can be obtained by actual measurement. Therefore, the charge amount Qa (nC/cm 3 ) of the electret sheet existing per unit space, that is, the space charge density is expressed by the following equation.
  • Qa (nC/cm 3 ) Ss (cm 2 /cm 3 ) x
  • Qs (nC/cm 2 ) Ls (cm/cm 2 ) ⁇ Qs (nC/cm 2 )
  • the space charge density can be obtained from the product of the total length Ls of the electret sheet per unit area of the cross section and the charge amount Qs per unit area of the electret sheet.
  • the filter is composed of many kinds of electret sheets, for example, when it is composed of 1, 2, . It is represented by the sum of the charge amounts Qa1, Qa2, . . . Qan per unit space of the electret sheet.
  • the space charge density of the filter has a lower limit of preferably 10 nC/cm 3 or more, more preferably 50 nC/cm 3 or more, still more preferably 80 nC/cm 3 or more, and 110 nC/cm 3 or more. is particularly preferred.
  • the upper limit is preferably 5000 nC/cm 3 or less due to restrictions on the amount of charge that the electret sheet can hold, and more preferably 2000 nC/cm 3 or less and 1000 nC/cm 3 or less due to the simplicity of manufacturing the electret sheet. is more preferred.
  • Thermoplastic resin> Propylene homopolymer (manufactured by Japan Polypropylene Corporation, trade name: Novatec PP FY4, MFR (230°C, 2.16 kg load): 5 g/10 minutes, melting point: 165°C)
  • ⁇ Filler> Heavy calcium carbonate (manufactured by Bihoku Funka Kogyo Co., Ltd., trade name: Softon 1800, average particle size: 1.2 ⁇ m)
  • ⁇ Functional agent> Metal carrier (manufactured by Ishizuka Glass Co., Ltd., trade name: Ion Pure ZAF HS, average particle size: 1 ⁇ m)
  • Scallop calcined powder Nikken Kagaku Kenkyusho Co., Ltd., trade name: Shell Nature, average particle size: 6.4 ⁇ m, containing 35% by mass of calcium hydroxide)
  • Resin composition (b) A propylene homopolymer and heavy calcium carbonate were blended as shown in Table 1 and melt-kneaded in a twin-screw kneader set at 210°C. Then, it was extruded in a strand shape by an extruder set at 230° C., cooled and then cut by a strand cutter to prepare pellets, which were used in the subsequent production.
  • Table 1 shows the compositions of resin compositions (a) to (h).
  • the resin composition (c) is melt-kneaded with an extruder set at 230° C., extruded into a sheet form from an extrusion die, and laminated on the first surface of the single-layer uniaxially stretched sheet to form a two-layer structure lamination. got a sheet.
  • the resulting laminated sheet having a two-layer structure was cooled to 60°C, heated again to about 150°C using a tenter oven, stretched 8.5 times in the horizontal direction, and then heated to 160°C in an oven for heat treatment.
  • the sheet was cooled to 60° C., and the edge portions were slit to obtain a laminated sheet having a two-layer structure (layer structure: c/b, thickness of each layer: 5/75 ⁇ m, number of stretching axes of each layer: 1 axis/2 axes).
  • the sheet had a thickness of 80 ⁇ m.
  • a meltblown nonwoven fabric (basis weight: 10 g/m 2 , fiber diameter: 6.5 ⁇ m) was produced using the resin composition (e).
  • the obtained nonwoven fabric had a thickness of 80 ⁇ m.
  • the thickness (total thickness) of the laminated sheet and the nonwoven fabric was measured according to JIS K7130:1999 using a constant pressure thickness measuring instrument (trade name: PG-01J, manufactured by Teclock Co., Ltd.).
  • the thickness of each layer in the laminated sheet was measured by cooling the sample to be measured with liquid nitrogen to a temperature of ⁇ 60° C.
  • the porosity (%) of the charged layer in the laminated sheet and nonwoven fabric was obtained from the ratio of the area occupied by the pores in a given region of the cross section of the laminated sheet and nonwoven fabric observed with an electron microscope.
  • An arbitrary part of the laminated sheet and non-woven fabric to be measured is cut, embedded in epoxy resin and solidified, then cut perpendicular to the surface direction of the printing paper to be measured using a microtome, and the cut surface is observed It was affixed to the observation sample stand so as to be a plane.
  • Gold, gold-palladium, or the like was vapor-deposited on the observation surface, and pores in the laminated sheet and the nonwoven fabric were observed with an electron microscope at a magnification of 1000 times, and the observed regions were captured as image data.
  • the obtained image data was subjected to image processing by an image analyzer, and the boundary between each layer was discriminated to obtain the area ratio (%) of the pore portion in a given area of the charged layer.
  • the porosity (%) of the charged layer was obtained by averaging the measured values obtained at arbitrary 10 observation points.
  • the bending resistance of the laminated sheet and non-woven fabric conforms to JIS L1096: 2010 and is measured using a Gurley bending resistance tester (manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd.) in the MD direction in an environment with a temperature of 23 ° C and a humidity of 50% RH. , trade name: GAS-100).
  • volume resistivity The volume resistivity of the laminated sheet and the nonwoven fabric was measured under the conditions of 23° C. and 50% relative humidity using an electrode of the double ring method according to JIS K6911:2006.
  • the water vapor transmission coefficient of the laminated sheet and nonwoven fabric was measured at 40° C. and 90% RH by the cup method according to JIS-Z-0208. From the obtained moisture permeability (g/m 2 ⁇ 24 hr) and the thickness (mm) of the laminated sheet and the nonwoven fabric, the water vapor permeability coefficient (g ⁇ mm/m 2 ⁇ 24 hr) was determined.
  • the arithmetic mean roughness Ra ( ⁇ m) of the functional layer surface of the laminated sheet and nonwoven fabric conforms to JIS B0601: 2003, using a three-dimensional roughness measuring instrument (manufactured by Kosaka Laboratory Co., Ltd., trade name: SE-3AK), and analysis Measurement was performed using an apparatus (manufactured by Kosaka Laboratory Co., Ltd., trade name: SPA-11).
  • Example 1 Manufacture of electret sheet (Example 1)
  • the distance between the needles of the main electrodes was set to 10 mm
  • the distance between the main electrode and the ground electrode was set to 10 mm
  • the back surface of the laminated sheet obtained in Production Example 1 was placed on the ground electrode board. placed in contact with the ground electrode surface. Then, charge was injected into the laminated sheet at the discharge voltage shown in Table 3 to obtain an electret sheet of Example 1.
  • Example 2 to 7 and Comparative Example 1 Electret sheets of Examples 2 to 7 were obtained in the same manner as in Example 1, except that the resin films obtained in Production Examples 2 to 7 were used and the thicknesses of the functional layer and charging layer were changed.
  • An electret sheet of Comparative Example 1 was obtained in the same manner as in Example 1, except that the resin film obtained in Production Example 8 was used.
  • An impedance analyzer manufactured by Keysight Technologies, product name: E4990A was used as a capacitance measuring device.
  • a voltage of 1 V is applied to each electret sheet under environmental conditions of a temperature of 23 ° C. and a relative humidity of 50%, and the capacitance is measured at a frequency in the range of 20 Hz to 1 MHz, and the capacitance (Cx) at a frequency of 100 kHz. Measured as a representative value. Then, using the same value and the separately measured thickness, the dielectric constant was obtained by calculation according to the following formula.
  • ⁇ r Cx ⁇ h / ( ⁇ 0 ⁇ A) ⁇ r: Relative permittivity of electret sheet (-)
  • A: Area of main electrode 3.848 ⁇ 10 -4 (m 2 )
  • antibacterial test An antibacterial test according to JISZ2801 was performed using Staphylococcus aureus and Escherichia coli as test strains. In both test strains, the antibacterial activity was evaluated as (+) when the antibacterial activity value was 2.0 or more and as (-) when the antibacterial activity value was less than 2.0.
  • Table 3 shows the results of measuring the dielectric constant, surface potential, antibacterial properties, and antifungal properties of the electret sheets obtained in each example and comparative example.
  • metal rack gears 21 peak pitch: 3.0 mm, peak height: 3.5 mm
  • metal pinion gears 22, and pressure rolls 23 were used to produce manufacturing examples 6 and 8.
  • the laminated sheets were corrugated in the following manner to obtain 20 corrugated sheets each.
  • the rack gear 21 is placed on a hot plate 24, heated so that the surface temperature of the rack gear 21 reaches 120° C., and a flute laminated sheet 25 having a width of 10 cm and a length of 20 cm is placed on the rack gear. Placed on 21.
  • the pinion gear 22 heated to 60° C. in an oven was rolled by hand to deform the laminated sheet 25 for flute into a shape similar to the surface shape of the rack gear 21 .
  • a liner laminate sheet 26 having a width of 10 cm and a length of 15 cm was placed on the previously deformed laminate sheet for flute 25, and a pressure roll 23 heated to 60° C. in an oven was rolled by hand.
  • the laminated sheets were heat-sealed to each other.
  • the layer of the resin composition (b) was always arranged on the lower side.
  • Qa Ls x Qs Qa: Filter space charge density (nC/cm 3 ) Ls: Total length per unit area of electret sheet (cm/cm 2 ) Qs: Charge amount per unit area of electret sheet (nC/cm 2 )
  • the filter 38 for evaluation was prepared by cutting it into a regular cube of 50 mm in width, 50 mm in height and 50 mm in length with a cardboard cutter. Next, the evaluation filter 38 is installed in the collection rate measuring device shown in FIG. Further, a glass tube 40 having a diameter of 40 mm and a length of 100 mm was placed thereon. Evaluation powder uniformly falls from a powder supply bottle 39 filled with 1.0 g of surface-treated calcium carbonate (manufactured by Maruo Calcium Co., Ltd., trade name: Calfine 200) as evaluation powder to an evaluation filter 38.
  • surface-treated calcium carbonate manufactured by Maruo Calcium Co., Ltd., trade name: Calfine 200
  • Ep (Wfa ⁇ Wf0)/((Wb0 ⁇ Wba) ⁇ (Wpa ⁇ Wp0)) ⁇ 100
  • the powder supply bottle 39 has a structure as shown in FIG. Installed and used.
  • Table 4 shows the results of measuring the space charge density, filter performance collection rate, antibacterial properties, and antifungal properties of the filters obtained in Example 8 and Comparative Example 3.
  • the electret sheets of Examples 1 to 7 and the filter of Example 8 had antibacterial and antifungal properties and were excellent in relative permittivity. In addition, no difference was observed between the surface potential A and the surface electron B, indicating that deterioration in electret performance such as charge retention due to moisture absorption was suppressed.
  • the electret sheet of Comparative Example 1 and the filter of Comparative Example 3 did not have antibacterial and antifungal properties. Further, in the electret sheet of Comparative Example 2, the value of the surface potential B after one week of charge injection at 40° C. after the charge injection was greatly reduced with respect to the surface potential A immediately after the charge injection, and the electret sheet did not have charge retention performance. .

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Filtering Materials (AREA)
  • Electrostatic Separation (AREA)
  • Laminated Bodies (AREA)

Abstract

La présente invention aborde le problème consistant à fournir : une feuille d'électret qui a au moins une propriété fonctionnelle choisie parmi une propriété antibactérienne, une propriété antivirale et une propriété antifongique et a d'excellentes propriétés de rétention de charge électrostatique ; et un filtre. L'invention concerne une feuille d'électret pourvue d'une couche électriquement chargée et d'une couche fonctionnelle, la couche électriquement chargée ayant une structure poreuse, la couche fonctionnelle contenant une résine thermoplastique (B) et un agent de fonctionnement ayant au moins une fonction choisie dans le groupe constitué d'une fonction antibactérienne, d'une fonction antivirale et d'une fonction antifongique dans une quantité totale de 1 à 40 % en masse par rapport à la masse totale de la couche fonctionnelle, et le coefficient de perméabilité à la vapeur d'eau de la feuille d'électret étant de 0,01 à 5,0 g · mm/m2·24 h. L'invention concerne également un filtre qui est équipé d'un trajet d'écoulement formé à l'aide de la feuille d'électret, le rapport de section transversale de trajet d'écoulement du trajet d'écoulement étant de 10 à 99 % et la densité de charge d'espace dans le filtre étant de 10 à 5 000 nC/cm3.
PCT/JP2023/007350 2022-02-28 2023-02-28 Feuille d'électret et filtre WO2023163218A1 (fr)

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JP2022029755 2022-02-28

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03186309A (ja) * 1989-12-13 1991-08-14 Shinagawa Nenryo Kk エアーフィルター
JP2011038195A (ja) * 2009-08-07 2011-02-24 Kuraray Kuraflex Co Ltd 複合繊維シート
WO2018164207A1 (fr) * 2017-03-10 2018-09-13 株式会社ユポ・コーポレーション Feuille traitée par électret et filtre
WO2019189349A1 (fr) * 2018-03-30 2019-10-03 株式会社ユポ・コーポレーション Feuille traitée par électret et filtre

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03186309A (ja) * 1989-12-13 1991-08-14 Shinagawa Nenryo Kk エアーフィルター
JP2011038195A (ja) * 2009-08-07 2011-02-24 Kuraray Kuraflex Co Ltd 複合繊維シート
WO2018164207A1 (fr) * 2017-03-10 2018-09-13 株式会社ユポ・コーポレーション Feuille traitée par électret et filtre
WO2019189349A1 (fr) * 2018-03-30 2019-10-03 株式会社ユポ・コーポレーション Feuille traitée par électret et filtre

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