WO2023163218A1 - Electret sheet and filter - Google Patents

Electret sheet and filter 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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WIPO (PCT)
Prior art keywords
electret sheet
layer
electret
sheet
filter
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PCT/JP2023/007350
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French (fr)
Japanese (ja)
Inventor
渉 佐藤
祐太郎 菅俣
洋介 廣井
Original Assignee
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/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
    • 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 OR LIGHT-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. .

Abstract

The present invention addresses the problem of providing: an electret sheet which has at least one functional property selected from an anti-bacterial property, an anti-viral property and an anti-fungal property and has excellent electrostatic charge retention properties; and a filter. Provided is an electret sheet provided with an electrically charged layer and a functional layer, in which the electrically charged layer has a porous structure, the functional layer contains a thermoplastic resin (B) and a functioning agent having at least one function selected from the group consisting of an anti-bacterial function, an anti-viral function and an anti-fungal function in a total amount of 1 to 40% by mass relative to the whole mass of the functional layer, and the water vapor permeability coefficient of the electret sheet is 0.01 to 5.0 g·mm/m2·24 hr. Also provided is a filter which is equipped with a flow path formed using the electret sheet, in which the flow path cross section ratio of the flow path is 10 to 99% and the space charge density in the filter is 10 to 5000 nC/cm3.

Description

エレクレットシート及びフィルターElectret sheet and filter
　本発明は、エレクレットシート及びフィルターに関する。 The present invention relates to electret sheets and filters.
　従来、空気中の塵や埃等の異物を捕集するフィルターに、エレクトレットシートを用いたフィルターが知られている。例えば、繰り返し折り曲げたエレクトレットシートと平板状のエレクトレットシートを交互に積層したフィルターであって、流路断面率が特定範囲にあるフィルターが開示されている（例えば、特許文献１参照）。 Conventionally, a filter using an electret sheet is known as a filter that collects foreign matter such as dust and dirt in the air. For example, disclosed is 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).
　上記エレクトレットシートとしては、帯電処理によって電荷を蓄積するポリプロピレン等の樹脂からなる不織布が提案されている（例えば、特許文献２参照）。また、内部に空孔を有する静電吸着フィルムも、電荷を保持しやすい構造を有することから、静電気力によって塵等を吸着するエレクトレットシートとして使用することができる（例えば、特許文献３参照）。 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). In addition, 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).
　また、空気中の塵や埃等の異物を捕集するフィルターは、塵や埃等の異物以外にも環境中に存在するダニ、花粉、細菌、又はウイルス等を捕集する。しかし、フィルターに捕集された細菌、ウイルスなどを不活化しないと、フィルター上での細菌などの増殖や、フィルターから再飛散したウイルスによる感染などを引き起こす懸念がある。これを回避するために、抗菌、抗ウイルス、及び防カビ性などの機能をエレクレットシートに付与することが検討されている。例えば、熱可塑性樹脂からなるメルトブロー不織布に難燃性、消臭性、抗菌性、防カビ性等の機能を備えた機能性材料を含む塗工剤の塗布により、機能性を付与させたエレクレットシートが開示されている（例えば、特許文献４参照）。 In addition, 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. However, if 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. In order to avoid this, it is being studied to impart functions such as antibacterial, antiviral and antifungal properties to the electret sheet. For example, an electret that imparts functionality to a melt-blown nonwoven fabric made of thermoplastic resin by applying a coating agent containing a functional material with functions such as flame retardancy, deodorant, antibacterial, and antifungal properties. A seat has been disclosed (see, for example, Patent Document 4).
特開２０１５－０９８０２２号公報JP 2015-098022 A 特開２００８－０１８３５０号公報JP 2008-018350 A 特開２０１０－０２３５０２号公報JP 2010-023502 A 特開平１１－２５３７１６号公報JP-A-11-253716
　しかしながら、機能性材料を含む塗工剤の塗布による機能付与は簡便であるが、塗工剤は一般的に極性基を含むバインダー等に機能性材料を分散させたものが多い。このような塗工剤を使用すれば、機能付与は可能であるものの、吸湿等により帯電保持性等のエレクトレット性能低下を招く懸念があった。 However, although it is easy to add functionality by applying a coating agent containing functional materials, most 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.
　本発明は、抗菌性、抗ウイルス性、及び防カビ性の少なくともいずれか一つの機能特性を有し、帯電保持性に優れたエレクトレットシート及びフィルターを提供することを目的とする。 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.
　本発明者らが上記課題を解決すべく鋭意検討を行った結果、帯電層と機能層とを備えるエレクトレットシートであって、機能層に抗菌、抗ウイルス、及び防カビからなる群より選択される少なくとも１つの機能を有する機能剤を特定の配合比率で含有すれば、上記課題を解決できることを見出し、本発明を完成した。
　すなわち、本発明は以下のとおりである。 As a result of intensive studies by the present inventors to solve the above problems, 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 inventors have found that the above problems can be solved by containing a functional agent having at least one function in a specific compounding ratio, and have completed the present invention.
That is, the present invention is as follows.
（１）帯電層と機能層とを備えるエレクトレットシートであって、
　前記帯電層が多孔質構造を有し、
　前記機能層が、熱可塑性樹脂及び抗菌、抗ウイルス、及び防カビからなる群より選択される少なくとも１つの機能を有する機能剤を機能層全体の質量に対して１～４０質量％の範囲で含み、
前記エレクトレットシートの水蒸気透過係数が０．０１～５．０ｇ・ｍｍ／ｍ２・２４ｈｒである
　エレクトレットシート。
　（２）
　前記帯電層の空孔率が１～７０％である
　（１）に記載のエレクトレットシート。
　（３）
　前記帯電層がポリオレフィン系樹脂を含む
　（１）又は（２）に記載のエレクトレットシート。
　（４）
　前記機能層が延伸樹脂フィルム層である、
　（１）～（３）のいずれか一項に記載のエレクトレットシート。
　（５）
　前記機能層の厚みが０．１～１０μｍである
　（１）～（４）のいずれか一項に記載のエレクトレットシート。
　（６）
　前記機能剤を、エレクトレットシート全体の質量に対して０．０１～３質量％の範囲で含む
　（１）～（５）のいずれか一項に記載のエレクトレットシート。
　（７）
　前記機能層が少なくとも一方向に延伸されている延伸樹脂フィルム層である
　（１）～（６）のいずれか一項に記載のエレクトレットシート。
　（８）
　前記機能層のＪＩＳ　Ｋ６９１１：２００６に準拠して測定した体積抵抗率が、１×１０１３～９×１０１７Ω・ｃｍである
　（１）～（７）のいずれか一項に記載のエレクトレットシート。
　（９）
　前記機能層の表面のＪＩＳ　Ｂ０６０１：２００３による算術平均粗さ（Ｒａ）が、０．０１～５μｍである、
　（１）～（８）のいずれか一項に記載のエレクトレットシート。
　（１０）
　前記エレクトレットシートのＪＩＳ　Ｌ１０９６：２０１０による曲げ反発Ａ法（ガーレ法）による剛軟度が、０．１～１ｍＮである
　（１）～（９）のいずれか一項に記載のエレクトレットシート。
　（１１）
　前記エレクトレットシートの比誘電率が１．１～２．５である
　（１）～（１０）のいずれか一項に記載のエレクトレットシート。
　（１２）
　（１）～（１１）のいずれか一項に記載のエレクトレットシートを備える
　フィルター。
　（１３）
　前記エレクトレットシートを用いて形成された流路を備え、前記流路の流路断面率が１０～９９％であり、前記フィルターの空間電荷密度が１０～５０００ｎＣ／ｃｍ３である
　（１２）に記載のフィルター。 (1) 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.
(2)
The electret sheet according to (1), wherein the charging layer has a porosity of 1 to 70%.
(3)
The electret sheet according to (1) or (2), wherein the charging layer contains a polyolefin resin.
(4)
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 μm.
(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.
(8)
The electret sheet according to any one of (1) to (7), wherein the functional layer has a volume resistivity of 1×10 13 to 9×10 17 Ω·cm as measured according to JIS K6911:2006. .
(9)
The surface of the functional layer has an arithmetic mean roughness (Ra) of 0.01 to 5 μm according to JIS B0601:2003.
The electret sheet according to any one of (1) to (8).
(10)
The electret sheet according to any one of (1) to (9), wherein the electret sheet has a bending resistance of 0.1 to 1 mN according to JIS L1096:2010 bending resistance A method (Gurley method).
(11)
The electret sheet according to any one of (1) to (10), wherein the electret sheet has a dielectric constant of 1.1 to 2.5.
(12)
A filter comprising the electret sheet according to any one of (1) to (11).
(13)
(12), wherein a flow channel is formed using the electret sheet, the flow channel has a flow channel cross-sectional ratio of 10 to 99%, and the filter has a space charge density of 10 to 5000 nC/cm 3 . filter.
　本発明によれば、抗菌性、抗ウイルス性、及び防カビ性の少なくともいずれか一つの機能特性を有し、帯電保持性に優れたエレクトレットシート及びフィルターを提供することができる。 According to the present invention, it is possible to provide 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.
本発明の一実施形態のエレクトレットシートの構成を示す断面図である。1 is a cross-sectional view showing the structure of an electret sheet according to an embodiment of the present invention; FIG. エレクトレット化装置の一例を示す図である。It is a figure which shows an example of an electret-ized apparatus. 本発明の一実施形態のフィルターの立体構造を示す側面図である。FIG. 3 is a side view showing the three-dimensional structure of the filter of one embodiment of the present invention; コルゲート加工装置の一例を示す図である。It is a figure which shows an example of a corrugating apparatus. 加工前のフルート用積層シートを示す図である。FIG. 4 is a diagram showing a laminated sheet for flutes before processing; 波板状に加工されたフルート用積層シートを示す図である。FIG. 3 is a view showing a laminated sheet for flutes processed into a corrugated plate shape. 波板状に加工されたフルート用積層シート上に積層された、平板状のライナー用積層シートを示す図である。FIG. 3 is a view showing a flat laminated liner sheet laminated on a corrugated laminated flute sheet. 本発明の実施例に使用した捕集率測定方法を示す図である。It is a figure which shows the collection rate measuring method used for the Example of this invention. 本発明の実施例において捕集率測定に使用した紛体供給ビンを示す図である。FIG. 3 is a diagram showing a powder supply bottle used for collection rate measurement in an example of the present invention;
　以下、本発明のエレクトレットシート及びフィルターについて詳細に説明するが、以下に記載する構成要件の説明は、本発明の一実施態様としての一例（代表例）であり、これらの内容に特定されるものではない。
　以下の説明において、「（メタ）アクリル」の記載は、アクリルとメタクリルの両方を示す。 Hereinafter, the electret sheet and filter of the present invention will be described in detail, but the description of the constituent elements described below is an example (representative example) as one embodiment of the present invention, and is specified by these contents. isn't it.
In the following description, the description of "(meth)acrylic" indicates both acrylic and methacrylic.
（エレクレットシート）
　図１は、本発明の一実施形態のエレクトレットシートの構成を示す断面図である。本発明のエレクトレットシートは、帯電層と、帯電層の少なくとも一方の面側に抗菌、抗ウイルス、及び防カビからなる群より選択される少なくとも１つの機能を有する機能剤を含む機能層と、を有する。少なくとも一方の面側に有するのであれば、本発明のエレクトレットシートは、帯電層の他方の面側にも機能層を有することができる。 (Electret sheet)
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.
　本発明のエレクトレットシートは、機能剤を含む機能層を備えるため、抗菌性、抗ウイルス性、及び防カビ性の少なくともいずれか一つの機能特性を有する。このとき、機能層が熱可塑性樹脂を含むことから、機能層の強度を高めて、耐環境性が向上できる。さらに、機能層が帯電層の表面を覆うため、吸湿等による帯電保持性等のエレクトレット性能低下を抑えることができる。また、本発明のエレクトレットシートは、帯電保持性能を帯電層に、抗菌、抗ウイルス又は防カビ等の機能を機能層に分離することにより、１つの層が帯電保持性能と上記機能とを有する場合と比べて、機能剤を機能層に濃縮して有することができる。したがって、本発明のエレクトレットシートは、エレクトレットシート全体における機能剤の含有量を抑えてコスト上の優位を得つつ、抗菌、抗ウイルス又は防カビ等の機能を得ることができる。 Since 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. At this time, since the functional layer contains a thermoplastic resin, the strength of the functional layer can be increased and the environmental resistance can be improved. Furthermore, since 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. Further, in the electret sheet of the present invention, 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.
＜帯電層＞
　本発明に使用される帯電層は、多孔質構造を有している。さらに、前記帯電層は多孔質構造を形成させるためには、フィラーを含有する熱可塑性樹脂を延伸した樹脂層であるのが好ましく、さらに前記延伸が、二軸延伸であるのが好ましい。前記帯電層は、フィラーを含有する熱可塑性樹脂を延伸した樹脂層等の多孔質構造体をエレクトレット化することによって、表面又は内部に電荷を保持して帯電し、塵、埃等の異物を吸着する静電吸着力をエレクトレットシートに付与する。前記帯電層を多孔質構造にすることにより、水蒸気透過係数を所望の範囲に制御しやすくなる。 <Charged layer>
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.
＜＜熱可塑性樹脂（Ａ）＞＞
　前記帯電層として用いることができる熱可塑性樹脂（Ａ）は、特に限定されないが、帯電層内部に蓄積した電荷が保持されやすいため、比誘電率が低く絶縁性に優れた熱可塑性樹脂（Ａ）が好ましい。 <<Thermoplastic resin (A)>>
The 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.
　前記熱可塑性樹脂（Ａ）として、例えば高密度ポリエチレン、中密度ポリエチレン、低密度ポリエチレン、プロピレン系樹脂、ポリメチル－１－ペンテン等のポリオレフィン系樹脂；エチレン・酢酸ビニル共重合体、エチレン・アクリル酸共重合体、マレイン酸変性ポリエチレン、マレイン酸変性ポリプロピレン等の官能基含有ポリオレフィン系樹脂；ナイロン－６、ナイロン－６，６等のポリアミド系樹脂；ポリエチレンテレフタレートやその共重合体、ポリブチレンテレフタレート、脂肪族ポリエステル等の熱可塑性ポリエステル系樹脂；ポリカーボネート系樹脂；アタクティックポリスチレン、シンジオタクティックポリスチレン等のポリスチレン系樹脂等が挙げられる。なかでも、絶縁性と加工性に優れるポリオレフィン系樹脂又は官能基含有ポリオレフィン系樹脂が好ましい。 Examples of the thermoplastic resin (A) 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 workability, are preferable.
　前記ポリオレフィン系樹脂の具体的な例としては、エチレン、プロピレン、ブチレン、ヘキセン、オクテン、ブタジエン、イソプレン、クロロプレン、メチル－１－ペンテン、環状オレフィン等のオレフィン類の単独重合体、これらオレフィン類を２種類以上組み合わせた共重合体等が挙げられる。 Specific examples of the polyolefin resin 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.
　前記官能基含有ポリオレフィン系樹脂の具体的な例としては、上記オレフィン類と共重合可能な官能基含有モノマーとの共重合体等が挙げられる。このような官能基含有モノマーとしては、例えばスチレン、α－メチルスチレン等のスチレン類；酢酸ビニル、ビニルアルコール、プロピオン酸ビニル、酪酸ビニル、ピバリン酸ビニル、カプロン酸ビニル、ラウリン酸ビニル、ステアリン酸ビニル、安息香酸ビニル、ブチル安息香酸ビニル、シクロヘキサンカルボン酸ビニル等のカルボン酸ビニルエステル類；アクリル酸、メタクリル酸、メチル（メタ）アクリレート、エチル（メタ）アクリレート、ブチル（メタ）アクリレート、ヘキシル（メタ）アクリレート、オクチル（メタ）アクリレート、２－エチルヘキシル（メタ）アクリレート、ステアリル（メタ）アクリレート、ベンジル（メタ）アクリレート、シクロヘキシル（メタ）アクリレート、イソボニル（メタ）アクリレート、ジシクロペンタニル（メタ）アクリレート、（メタ）アクリルアミド、Ｎ－メタロール（メタ）アクリルアミド等の（メタ）アクリル酸及びその誘導体類；メチルビニルエーテル、エチルビニルエーテル、プロピルビニルエーテル、ブチルビニルエーテル、シクロペンチルビニルエーテル、シクロヘキシルビニルエーテル、ベンジルビニルエーテル、フェニルビニルエーテル等のビニルエーテル類等が挙げられる。これら官能基含有モノマーのなかから、必要に応じて１種類又は２種類以上を適宜選択して共重合に用いることができる。 Specific examples of the functional group-containing polyolefin resin include copolymers of the above-mentioned olefins and functional group-containing monomers that can be copolymerized. Examples of such functional group-containing monomers include styrenes such as styrene and α-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)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, ( (Meth)acrylic acid and its derivatives such as meth)acrylamide and N-metalol (meth)acrylamide; Vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, cyclopentyl vinyl ether, cyclohexyl vinyl ether, benzyl vinyl ether, and phenyl vinyl ether etc. From these functional group-containing monomers, one or two or more can be appropriately selected and used for copolymerization as necessary.
　前記ポリオレフィン系樹脂及び官能基含有ポリオレフィン系樹脂を、必要に応じてグラフト重合したグラフト変性物として使用することも可能である。グラフト変性物を得るには公知の手法が用いることができる。具体的な例としては、不飽和カルボン酸又はその誘導体をグラフトモノマーとしてグラフト重合する方法等が挙げられる。前記不飽和カルボン酸としては、例えば、アクリル酸、メタクリル酸、マレイン酸、フマル酸、イタコン酸等が挙げられる。また、上記不飽和カルボン酸の誘導体としては、例えば酸無水物、エステル、アミド、イミド、金属塩等が挙げられる。前記不飽和カルボン酸の誘導体の具体例としては、例えば無水マレイン酸、無水イタコン酸、無水シトラコン酸、（メタ）アクリル酸メチル、（メタ）アクリル酸エチル、（メタ）アクリル酸ブチル、（メタ）アクリル酸グリシジル、マレイン酸モノエチルエステル、マレイン酸ジエチルエステル、フマル酸モノメチルエステル、フマル酸ジメチルエステル、イタコン酸モノメチルエステル、イタコン酸ジエチルエステル、（メタ）アクリルアミド、マレイン酸モノアミド、マレイン酸ジアミド、マレイン酸－Ｎ－モノエチルアミド、マレイン酸－Ｎ，Ｎ－ジエチルモノアミド、マレイン酸－Ｎ－モノブチルアミド、マレイン酸－Ｎ，Ｎ－ジブチルモノアミド、フマル酸モノアミド、フマル酸ジアミド、フマル酸－Ｎ－モノエチルアミド、フマル酸－Ｎ，Ｎ－ジエチルモノアミド、フマル酸－Ｎ－ブチルモノアミド、フマル酸－Ｎ，Ｎ－ジブチルモノアミド、マレイミド、Ｎ－ブチルマレイミド、Ｎ－フェニルマレイミド、（メタ）アクリル酸ナトリウム、（メタ）アクリル酸カリウム等が挙げられる。上記グラフト変性物中、ポリオレフィン系樹脂及び官能基含有ポリオレフィン系樹脂に対してグラフト重合された前記グラフトモノマーの割合は特に制限されないが、０．００５～１０質量％の範囲が好ましく、さらに０．０１～５質量％の範囲が好ましい。 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. Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid. Examples of the unsaturated carboxylic acid derivatives include acid anhydrides, esters, amides, imides, and metal salts. Specific examples of the 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, fumaric acid-N,N-diethylmonoamide, fumaric acid-N-butylmonoamide, fumaric acid-N,N-dibutylmonoamide, maleimide, N-butylmaleimide, N-phenylmaleimide, sodium (meth)acrylate, Potassium (meth)acrylate and the like can be mentioned. 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.
　前記帯電層に含まれる前記熱可塑性樹脂（Ａ）は、上記熱可塑性樹脂（Ａ）の中から１種を選択して単独で使用してもよいし、２種以上を選択して組み合わせて使用してもよい。 The 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
　また、前記ポリオレフィン系樹脂のなかでも、ポリプロピレン系樹脂が、絶縁性、加工性、耐水性、耐薬品性、コスト等の観点から好ましい。前記ポリプロピレン系樹脂としては、アイソタクティック、シンジオタクティック又は種々の程度の立体規則性を示すプロピレン単独重合体、モノマーとしてプロピレンを主成分（樹脂全体に含まれる割合が５０質量％以上）とし、エチレン、１－ブテン、１－ヘキセン、１－ヘプテン、４－メチル－１－ペンテン等のα－オレフィンとを共重合させた共重合体が挙げられる。前記プロピレンとα－オレフィンとの共重合体は、２元系でも３元系以上でもよく、またランダム共重合ブロック共重合体でもよい。前記ポリプロピレン系樹脂は、１種単独でも２種以上を混合して使用することができる。
　熱可塑性樹脂（Ａ）として前記ポリプロピレン系樹脂を用いる場合には、フィルム成形性の観点から、前記ポリプロピレン系樹脂又はプロピレン単独重合体よりも融点が低い樹脂を熱可塑性樹脂（Ａ）全体の質量に対して２～２５質量％配合して使用することが好ましい。そのような融点が低い樹脂としては、高密度又は低密度のポリエチレン等を例示することができる。 Among the above polyolefin resins, 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 α-olefins such as ethylene, 1-butene, 1-hexene, 1-heptene and 4-methyl-1-pentene can be mentioned. The copolymer of propylene and α-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.
When the polypropylene resin is used as the thermoplastic resin (A), from the viewpoint of film moldability, 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.
　前記帯電層における前記熱可塑性樹脂（Ａ）の配合量は、帯電層全体の質量に対して、５０質量％以上が好ましく、５１質量％以上がより好ましく、６０質量％以上がさらに好ましく、９９質量％以下が好ましく、９５質量％以下がより好ましい。前記熱可塑性樹脂（Ａ）の配合量が５０質量％以上であれば、帯電層を成形しやすく、得られた帯電層は、その熱可塑性樹脂（Ａ）の絶縁性から電荷を保持しやすい。 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. When 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).
　前記帯電層に用いられる熱可塑性樹脂（Ａ）として、帯電層全体の質量に対してポリプロピレン系樹脂５０～９８質量％と、ポリエチレン系樹脂１～４９質量％とを含むことが好ましく、ポリプロピレン系樹脂５０～９６質量％と、ポリエチレン系樹脂３～２９質量％とを含むことがより好ましい。 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.
＜＜フィラー＞＞
　前記帯電層に用いられるフィラーとして、例えば、無機フィラー及び有機フィラーが挙げられる、これらは、１種単独で、又は２種以上を混合して用いることができる。無機フィラー及び／又は有機フィラーの含有により、帯電層中に空孔（ボイド）を形成し、熱可塑性樹脂（Ａ）と空気との界面（表面積）を増加させることで、帯電層の帯電性が向上しやすくなる。また、帯電層の表面に無機フィラー又は有機フィラーに起因する起伏（突起構造）を形成して、帯電層の表面を粗面とすることができる。粗面化により、帯電層の表面積が増大し、エレクトレットシートの吸着面積が大きくなる結果、フィルターの集塵効果を高めることができる。 <<Filler>>
Examples of fillers used in the charging layer include inorganic fillers and organic fillers. These may be used singly or in combination of two or more. By containing the inorganic filler and/or the organic filler, 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. Further, 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.
　前記無機フィラーとしては、例えば炭酸カルシウム、焼成クレイ、シリカ、けいそう土、白土、タルク、酸化チタン、硫酸バリウム、アルミナ、ゼオライト、マイカ、セリサイト、ベントナイト、セピオライト、バーミキュライト、ドロマイト、ワラストナイト、及びガラスファイバー等が挙げられる。なかでも、重質炭酸カルシウム、軽質炭酸カルシウム、焼成クレイ又はタルクが、空孔の成形性が良く、安価なために好ましい。 Examples of the inorganic filler 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. Among them, heavy calcium carbonate, light calcium carbonate, calcined clay or talc is preferable because of good pore moldability and low cost.
　前記有機フィラーとしては、前記帯電層の主成分である前記熱可塑性樹脂（Ａ）とは異なる種類の樹脂からなる有機フィラーを選択することが好ましく、さらに、前記熱可塑性樹脂（Ａ）よりも高い融点を有する樹脂又は前記熱可塑性樹脂（Ａ）よりも高いガラス転移点を有する樹脂であって、前記可塑性樹脂と非相溶性の樹脂からなる有機フィラーを選択するのが好ましい。前記有機フィラーとして、例えば、前記熱可塑性樹脂（Ａ）がポリオレフィン系樹脂である場合には、ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリカーボネート、ナイロン－６、ナイロン－６，６、環状ポリオレフィン、ポリスチレン、ポリメタクリレート等の重合体であって、ポリオレフィン系樹脂の融点よりも高い融点（例えば１７０～３００℃）又はガラス転移温度（例えば１７０～２８０℃）を有するものを好ましく挙げられる。 As 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. Examples of 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.
　レーザー回折による粒度分布計で測定したフィラーの体積平均粒径は、０．１μｍ以上が好ましく、０．５μｍがより好ましく、１μｍ以上がさらに好ましい。一方、フィラーの体積平均粒径は、３０μｍ以下が好ましく、２０μｍ以下がより好ましく、１０μｍ以下がさらに好ましく、５μｍ以下が特に好ましい。また、フィラーの体積平均粒径は、好ましくは０．１～３０μｍの範囲が好ましく、さらに０．５～２０μｍの範囲、１～１０μｍの範が好ましく、１．０～５．０μｍの範囲が特に好ましい。前記フィラーの体積平均粒径が、０．１μｍ以上であれば、帯電層への空孔の形成の容易性の点で好ましく、前記フィラーの体積平均粒径が３０μｍ以下であれば、帯電層の耐久性及び帯電性の向上の点で好ましい。 The volume average particle size of the filler measured by a particle size distribution meter using laser diffraction is preferably 0.1 µm or more, more preferably 0.5 µm or more, and even more preferably 1 µm or more. On the other hand, the volume average particle size of the filler is preferably 30 µm or less, more preferably 20 µm or less, still more preferably 10 µm or less, and particularly preferably 5 µm or less. The volume average particle size of the filler is preferably in the range of 0.1 to 30 μm, more preferably in the range of 0.5 to 20 μm, preferably in the range of 1 to 10 μm, particularly in the range of 1.0 to 5.0 μm. preferable. When the volume average particle diameter of the filler is 0.1 μm 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.
　帯電層におけるフィラーの配合量は、帯電層中における空孔の成形性の観点からは、１質量％以上が好ましく、５質量％以上がより好ましい。また、帯電層の帯電量の制御の容易性及びフィルターの集塵効果の持続性という観点からは、同配合量が４９質量％以下であることが好ましく、４０質量％以下がより好ましい。 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.
＜＜他の添加剤＞＞
　帯電層は、必要に応じて、金属石鹸、熱安定剤（酸化防止剤）、光安定剤、分散剤、滑剤等の添加剤を含有することができる。 <<other additives>>
The charging layer may contain additives such as metallic soaps, heat stabilizers (antioxidants), light stabilizers, dispersants, and lubricants, if necessary.
　帯電層が金属石鹸を含有する場合、その含有量は、帯電層全体の質量に対して０．０１～１０．０質量％の範囲が好ましい。金属石鹸としては、例えば、オクタデカン酸ジヒドロキシアルミニウム、ジオクタデカン酸ヒドロキシアルミニウム、トリオクタデカン酸アルミニウム、ドデカン酸ジヒドロキシアルミニウム、ジドデカン酸ヒドロキシアルミニウム、トリドデカン酸アルミニウム、２－エチルヘキサン酸ジヒドロキシアルミニウム、ジ－２－エチルヘキサン酸ヒドロキシアルミニウム、トリ－２－エチルヘキサン酸アルミニウム等の飽和高級脂肪酸アルミニウム塩等が挙げられる。 When 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. Examples of metal soaps include dihydroxyaluminum octadecanoate, hydroxyaluminum dioctadecanoate, aluminum trioctadecanoate, dihydroxyaluminum dodecanoate, hydroxyaluminum didodecanoate, aluminum tridodecanoate, dihydroxyaluminum 2-ethylhexanoate, and di-2-ethyl. Examples include saturated higher fatty acid aluminum salts such as hydroxyaluminum hexanoate and aluminum tri-2-ethylhexanoate.
　帯電層が熱安定剤を含有する場合、その含有量は、帯電層全体の質量に対して０．００１～１質量％の範囲が好ましい。熱安定剤としては、例えば嵩高いフェノール系、リン系、アミン系等の安定剤等が挙げられる。 When 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. Examples of heat stabilizers include bulky phenol-based, phosphorus-based, and amine-based stabilizers.
　帯電層が光安定剤を含有する場合、その含有量は、帯電層全体の質量に対して０．００１～１質量％の範囲が好ましい。光安定剤としては、例えば嵩高いアミン系やベンゾトリアゾール系、ベンゾフェノン系の光安定剤等が挙げられる。 When 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. Examples of light stabilizers include bulky amine-based, benzotriazole-based, and benzophenone-based light stabilizers.
　分散剤又は滑剤は、例えば帯電層に添加されるフィラーを分散させる目的で含有させることができる。帯電層が分散剤又は滑剤を含有する場合、その含有量は、帯電層全体の質量に対して０．０１～４質量％の範囲が好ましい。分散剤又は滑剤としては、例えばシランカップリング剤、オレイン酸やステアリン酸等の高級脂肪酸、ポリアクリル酸、ポリメタクリル酸、それらの塩等が挙げられる。 A dispersant or lubricant can be contained, for example, for the purpose of dispersing a filler added to the charging layer. When the charging layer contains a dispersant or a lubricant, the content thereof is preferably in the range of 0.01 to 4% by weight based on the weight of the entire charging layer. Examples of dispersants or lubricants include silane coupling agents, higher fatty acids such as oleic acid and stearic acid, polyacrylic acid, polymethacrylic acid, and salts thereof.
＜＜多層構造＞＞
　帯電層は、単層構造であってもよいし、多層構造であってもよい。
　多層構造の帯電層は、エレクトレット化によって電荷を注入するときの耐電圧性能の向上、注入した電荷が外部に逃げないように封じこめる機能の向上、エレクトレットシート同士の接合等の２次加工適性、帯電防止性等の様々な機能を付与することが可能となる。 <<multilayer structure>>
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.
＜＜帯電層の製造方法＞＞
　帯電層は、押出成形によりフィルム成形されることが好ましい。押出成形としては、例えば帯電層の融点又はガラス転移温度よりも高い温度に設定した押出機で帯電層の原料を溶融混練し、Ｔダイ、Ｉダイ等を使用してシート状に押出し、金属ロール、ゴムロール、金属ベルト等で冷却するシート成形や、円形のダイを使用してチューブ状に押出しチューブ内の内圧力により一定の倍率に膨らませながら、空気や水で冷却するインフレーション成形等が挙げられる。帯電層をシート成形する場合は、冷却用の金属ロール又はゴムロールとして表面が凹凸形状を有するロールを使用して、表面を粗面化してもよい。粗面化により、エレクトレットシートの吸着面積が大きくなり、フィルターの集塵効果が向上する。 <<Manufacturing Method of Charged Layer>>
The charging layer is preferably film-formed by extrusion. In 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., and 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. When the charging layer is formed into a sheet, 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.
　多層構造の帯電層の場合の成形方法としては、フィードブロック、マルチマニホールドを使用した多層ダイス方式、複数のダイスを使用する押出しラミネーション方式等が挙げられる。多層ダイス方式と押出しラミネーション方式は組み合わせることも可能である。 Examples of 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.
＜＜延伸＞＞
　帯電層は、無延伸フィルムであってもよく、延伸フィルムであってもよいが、少なくとも一方向に延伸された延伸フィルムであることが好ましい。これにより、帯電層の厚みの均一性を高めることができる。帯電層の厚みの均一性が高いと、エレクトレット化時の高電圧下において薄い箇所への放電の局所集中を減らすことができ、帯電層の電気特性の均一性を向上させることができる。 <<Stretching>>
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.
　フィルムの延伸は、通常用いられる種々の方法のいずれかによって行うことができる。帯電層が単層である場合は、当該層が１軸延伸又は２軸延伸によって形成された層であることが好ましく、帯電層が多層構造である場合は、例えば各層の延伸軸数がそれぞれ、１軸／１軸、１軸／２軸、１軸／１軸／２軸、１軸／２軸／１軸、１軸／２軸／２軸、２軸／２軸／２軸等である積層構造を含むものが挙げられる。 The stretching of the film can be carried out by any of various commonly used methods. When the charged layer is a single layer, it is preferably a layer formed by uniaxial stretching or biaxial stretching. 1-axis/1-axis, 1-axis/2-axis, 1-axis/1-axis/2-axis, 1-axis/2-axis/1-axis, 1-axis/2-axis/2-axis, 2-axis/2-axis/2-axis, etc. One including a laminated structure is mentioned.
　延伸方法としては、ロール群の周速差を利用した縦延伸、テンターオーブンを使用した横延伸、縦延伸と横延伸の組み合わせによる逐次２軸延伸、圧延、テンターオーブンとリニアモーターの組み合わせによる同時２軸延伸、テンターオーブンとパンタグラフの組み合わせによる同時２軸延伸等が挙げられる。インフレーションフィルムの延伸方法としては、チューブラー法による同時２軸延伸等が挙げられる。なお、縦方向はフィルムの流れ方向（ＭＤ）であり、横方向はフィルムの幅方向（ＴＤ）である。 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, and the transverse direction is the width direction (TD) of the film.
　延伸倍率は、特に限定されず、帯電層に用いる熱可塑性樹脂（Ａ）の特性等を考慮して適宜決定する。例えば、熱可塑性樹脂（Ａ）としてプロピレン単独重合体又はその共重合体を使用し、その樹脂フィルムを１軸延伸する場合の延伸倍率は、通常１．２～１２倍、好ましくは２～１０倍である。２軸延伸の場合には、面積倍率で通常１．５～６０倍、好ましくは４～５０倍である。その他の熱可塑性樹脂（Ａ）を使用した樹脂フィルムを１軸延伸する場合の延伸倍率は、通常１．２～１０倍、好ましくは２～５倍であり、２軸延伸の場合の面積倍率は、通常１．５～２０倍、好ましくは４～１２倍である。 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. For example, when a propylene homopolymer or a copolymer thereof is used as the thermoplastic resin (A) and the resin film is uniaxially stretched, the draw ratio is usually 1.2 to 12 times, preferably 2 to 10 times. is. In the case of biaxial stretching, the area magnification is usually 1.5 to 60 times, preferably 4 to 50 times. When a resin film using other thermoplastic resin (A) is uniaxially stretched, 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.
　延伸の温度は、帯電層に主に用いる熱可塑性樹脂（Ａ）のガラス転移温度以上、結晶部の融点以下の範囲で、熱可塑性樹脂（Ａ）に好適な公知の温度範囲内で行うことができる。具体的には、例えば帯電層の熱可塑性樹脂（Ａ）がプロピレン単独重合体（融点１５５～１６７℃）の場合は１００～１６６℃、高密度ポリエチレン（融点１２１～１３６℃）の場合は７０～１３５℃であり、融点より１～７０℃低い温度である。また、延伸速度は２０～３５０ｍ／分が好ましい。 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. Specifically, for example, when 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. Moreover, the drawing speed is preferably 20 to 350 m/min.
＜機能層＞
　本発明のエレクトレットシートに含まれる機能層は、熱可塑性樹脂（Ｂ）及び抗菌、抗ウイルス、及び防カビからなる群より選択される少なくとも１つの機能を有する機能剤を前記機能層全体の質量に対して１～４０質量％の範囲で含む。機能層は、当該機能剤を含むことにより、抗菌性、抗ウイルス性、及び防カビ性の少なくともいずれか一つの機能特性をエレクレットシートに付与する。また、本発明のエレクトレットシートをフィルターとして用いた場合に、前記エレクトレットシートを空気の流れ方向の反対側の帯電層の表面に前記機能層を設けて積層構造とすることにより、前記帯電層に形成した空孔が外部と通じて内部に蓄えた電荷が大気放電してしまうことを防ぎやすくでき、前記エレクトレットシートの表面強度を向上させることができ、さらに、吸湿等により帯電保持性等のエレクトレット性能低下を抑えることができる。 <Function layer>
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. By containing the functional agent, the functional layer provides the electret sheet with at least one functional property of antibacterial, antiviral, and antifungal properties. Further, when 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.
＜＜機能剤＞＞
　機能層は、上述したように、抗菌、抗ウイルス、及び防カビからなる群より選択される少なくとも１つの機能を有する機能剤を含む。
　なお、本明細書において「抗菌」とは、例えば細菌、真菌類の殺菌、損傷、又は増殖防止を示し、「抗ウイルス」とは、例えばウイルスの不活化を示す。また、「防カビ」とは、例えばカビの発生、又は増殖防止を示す。 << functional agent >>
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.
As used herein, the term "antibacterial" refers to, for example, sterilization, damage, or growth prevention of bacteria and fungi, and the term "antiviral" refers to, for example, inactivation of viruses. In addition, "antifungal" indicates, for example, the prevention of the occurrence or growth of mold.
　抗菌性、抗ウイルス性、及び防カビ性の少なくともいずれか一つの特性を有する機能剤は、特に限定されず、公知の薬剤を用いることができる。機能剤としては、例えば、４級アンモニウム塩、金属担持体、光触媒、貝殻粉末、焼成貝殻粉末、アルデヒド系化合物、ヨード系化合物、ピグアニド化合物、及びアクリノール水和物（例えば、乳酸６，９－ジアミノ－２－エトキシアクリジン一水和物）等が挙げられる。なかでも、長期間電荷をさらに保持しやすくなることに加えて、取り扱い性が良好で、安全性も高く、入手し易い点で、金属担持体、貝殻粉末又は焼成貝殻粉末が好ましく、貝殻粉末又は焼成貝殻粉末がより好ましい。 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. Among them, 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.
　前記金属担持体は、金属と該金属を担持する担体とから構成される。金属としては、例えば、金、銀、銅、亜鉛、鉄、ビスマス、チタン、及びニッケル等が挙げられる。また、金属を含む抗菌剤に含まれる金属の態様は特に制限されず、金属粒子、金属イオン、及び金属塩（金属錯体を含む）の形態が挙げられる。なかでも、より優れた抗菌性、抗ウイルス性、又は防カビ性を得る観点から、金属は、金、銀、又は銅が好ましい。担体としては、例えば、無機酸化物（例えば、ゼオライト（結晶性アルミノケイサン塩）、シリカゲル、粘土鉱物等のケイ酸塩、ガラス（水溶性ガラスを含む）、リン酸ジルコニウム、及びリン酸カルシウム等）、活性炭、金属担体、及び有機金属等が挙げられる。金属担持体は、優れた抗菌性、抗ウイルス性又は防カビ性を得る観点から、銀担持体であることが好ましい。銀担持体における銀は、具体的には、硝酸銀、塩化銀、硫酸銀、乳酸銀、及び酢酸銀等の銀塩；銀アンモニア錯体、銀クロロ錯体、及び銀チオスルファト錯体等の銀錯体；銀粒子；又は、銀イオンであることができる。 The metal support is composed of a metal and a support that supports the metal. Examples of metals include gold, silver, copper, zinc, iron, bismuth, titanium, and nickel. In addition, 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). Among them, the metal is preferably gold, silver, or copper from the viewpoint of obtaining superior antibacterial, antiviral, or antifungal properties. Examples of carriers include inorganic oxides (e.g., zeolite (crystalline aluminosilicate), silica gel, silicates such as clay minerals, glass (including water-soluble glass), zirconium phosphate, calcium phosphate, etc.), activated carbon. , metal carriers, and organic metals. From the viewpoint of obtaining excellent 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.
　光触媒は光触媒作用を示す物質である。光触媒としては、特に限定されないが、例えば、ＳｒＴｉＯ２、ＺｎＯ、ＣｄＳ、ＳｎＯ２、及びＷＯ３等が挙げられる。貝殻粉末及び焼成貝殻粉末としては、例えば、ホタテ貝粉末及び牡蠣粉末等が挙げられる。 A photocatalyst is a substance that exhibits photocatalytic action. Examples of photocatalysts include, but are not limited to, SrTiO 2 , ZnO, CdS, SnO 2 and WO 3 . Examples of shell powder and baked shell powder include scallop powder and oyster powder.
　アルデヒド系化合物としては特に限定されないが、例えば、グルタラール、フタラール、及びホルマリン等が挙げられる。 Aldehyde compounds are not particularly limited, but include, for example, glutaral, phthalal, and formalin.
　ヨード系化合物としては特に限定されないが、例えば、ポピドンヨード、及びヨードチンキ等が挙げられる。 The iodine-based compound is not particularly limited, but examples include povidone-iodine and iodine tincture.
　ピグアニド化合物としては特に限定されないが、例えば、クロルヘキシジングルコン酸塩、クロルヘキシジン塩酸塩、及びクロルヘキシジン酢酸塩等が挙げられる。 Although the piguanide compound is not particularly limited, examples thereof include chlorhexidine gluconate, chlorhexidine hydrochloride, and chlorhexidine acetate.
　前記機能層における前記機能剤の含有量は、抗菌性、抗ウイルス性、防カビ性などの機能をより確実に発揮させる観点から、前記機能層全体の質量に対して１質量％以上であり、２質量％以上が好ましく、３質量％以上がより好ましく、４質量％以上がさらに好ましい。一方、前記機能層における前記機能剤の含有量は、前記機能層の強度及び対環境性を維持する観点から、機能層全体の質量に対して４０質量％以下であり、３０質量％以下が好ましく、１５質量％以下がより好ましく、７質量％以下がさらに好ましく、５質量％以下が特に好ましい。なお、本明細書において、機能剤が貝殻粉末又は焼成貝殻粉末である場合の前記機能剤の含有量は、貝殻粉末又は焼成貝殻粉末に含まれる水酸化カルシウムの量であるものとする。 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. On the other hand, 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. In this specification, when the functional agent is shell powder or calcined shell powder, the content of the functional agent is the amount of calcium hydroxide contained in the shell powder or calcined shell powder.
　また、前記機能剤の前記エレクトレットシート全体における含有量は、抗菌性、抗ウイルス性、防カビ性などの機能をより確実に発揮させる観点から、エレクトレットシート全体の質量に対して０．０１質量％以上が好ましく、０．０５質量％以上がより好ましく、０．１質量％以上がさらに好ましい。一方、前記機能剤の前記エレクトレットシート全体における含有量は、コスト軽減及び電荷保持の観点から、前記エレクトレットシート全体の質量に対して５質量％以下が好ましく、３質量％以下がより好ましく、１質量％以下がさらに好ましい。 In addition, 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. On the other hand, 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.
＜＜熱可塑性樹脂（Ｂ）＞＞
　前記機能層は熱可塑性樹脂（Ｂ）を含む。前記熱可塑性樹脂（Ｂ）としては、特に限定されないが、延伸特性の観点及び帯電層との層間強度の観点からは、帯電層と同種の樹脂が好ましく、具体的にはポリオレフィン系樹脂を使用することが好ましい。前記ポリオレフィン系樹脂としては、例えば、帯電層の項目で例示された具体例と同様のものが挙げられ、中でもポリプロピレン系樹脂が好ましい。ポリプロピレン系樹脂として、例えば、帯電層の項目で例示された具体例と同様のものが挙げられる。前記帯電層との層間強度の観点から、前記機能層中の前記熱可塑性樹脂（Ｂ）の含有量は、前記機能層全体の質量に対して６０質量％以上であることが好ましく、７０質量％以上であることがより好ましく、８０質量％以上であることがさらに好ましく、９０質量％以上であることが特に好ましい。 <<Thermoplastic resin (B)>>
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. From the viewpoint of interlayer strength with 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.
＜＜フィラー＞＞
　前記機能層は、無機フィラー又は有機フィラーを含有してもしなくてもよいが、前記機能層の誘電率等の電気的特性を改質する観点からは、含有することが好ましい。無機フィラー又は有機フィラーとしては、例えば前記帯電層の項目で例示したものと同様のものが挙げられる。なかでも、無機フィラーは、一般的に熱可塑性樹脂（Ｂ）よりも誘電率が高いために、前記機能層の電気的特性の改質に適している。特に、前記機能層の前記熱可塑性樹脂（Ｂ）としてポリオレフィン系樹脂等の誘電率が低い樹脂を使用する場合は、無機フィラーの含有により、エレクトレット化時に無機フィラーの誘電効果により前記帯電層まで電荷を到達させることができ、好ましい。 <<Filler>>
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. Examples of 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). In particular, 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.
＜＜他の添加剤＞＞
　前記機能層は、必要に応じて、熱安定剤（酸化防止剤）、光安定剤、分散剤、滑剤等の添加剤を含有することができる。これらの添加剤としては、例えば、前記帯電層の項目で例示したものと同様のものが挙げられる。 <<other additives>>
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.
　前記機能層は、無延伸フィルム層であってもよく、延伸フィルム層であってもよいが、厚みの均一性を高める観点から、少なくとも一方向に延伸された延伸フィルム層であることが好ましい。厚みの均一性が高いと、エレクトレット化時の高電圧下において薄い箇所への放電の局所集中を減らすことができ、機能層の電気特性の均一性を向上させることができる。前記機能層を延伸方法、延伸倍率、延伸温度等については、例えば、帯電層の項目で例示されたものと同様のものが挙げられる。 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.
　前記機能層は、帯電層と同様に多孔質構造を有することができる。多孔質構造を有することにより、機能剤がエレクトレットシート表面に露出しやすくなり、機能剤の効果が発現しやすくなる。また、前記機能層は前記帯電層よりも空孔率が低い構造であることが好ましい。この様な前記機能層の形成は、フィラーの含有量を帯電層よりも少なくする手法や、機能層に使用するフィラーの体積平均粒径を帯電層に使用するフィラーの体積平均粒径より小さくする手法や、帯電層を２軸延伸により形成し且つ機能層を１軸延伸で形成する等して両者の延伸倍率に差異をつける手法等により達成できる。 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.
　前記機能層は単層構造のみならず、２層構造以上の多層積層構造のものであってもよい。前記多層積層構造とする場合は、各層に使用する熱可塑性樹脂（Ｂ）、フィラー、機能剤の種類や含有量を変更することにより、より優れた機能特性及び帯電保持性を備えた前記エレクトレットシートとすることができる。 The functional layer may have not only a single-layer structure but also a multi-layer structure of two or more layers. In the case of the multilayer laminated structure, 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
　前記機能層を前記帯電層の両面に設ける場合は、前記機能層のそれぞれの組成、構成、厚み等は同一でもよいし、異なっていてもよい。 When the functional layers are provided on both sides of the charging layer, the composition, configuration, thickness, etc. of the functional layers may be the same or different.
（エレクトレットシートの製造）
　本発明のエレクトレットシートは、前記帯電層及び前記機能層を積層したシート（以下、積層シートということがある。）にエレクトレット化処理を施し、前記積層シートの表面又は内部に電荷を保持させることにより得られる。 (Manufacture of electret sheet)
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.
　前記積層シートは、フィードブロックやマルチレイヤーダイを使用した多層ダイ方式、前記帯電層に溶融した前記機能層を積層する押出ラミネート方式、前記帯電層に別途作成した前記機能層を接着剤を介して積層するドライラミネート方式等により製造することができる。なかでも、帯電性が良好な前記機能層を得やすい多層ダイス方式や押出ラミネート方式が好ましい。なお、積層シートの各層を単独でフィルム成形する場合、上述した帯電層と同様にしてフィルム成形することができる。 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.
　前記積層シートは、少なくとも一方向に延伸された層を有することが好ましい。前記積層シートは、例えば縦方向に延伸した前記帯電層に、前記機能層を積層することにより得てもよく、また縦方向に延伸した前記帯電層に前記機能層を積層した後、さらに横方向に延伸することにより、各々１軸／２軸（機能層／帯電層）に延伸された層を有する積層シートとしてもよい。好ましい延伸方法、延伸倍率、延伸温度等の条件は、上述した帯電層と同様である。 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.
＜エレクトレット化＞
　前記積層シートのエレクトレット化は、後述するフィルターの製造プロセスの前でも後でも途中でもよい。立体構造物を均一にエレクトレット化するためにはエレクトレット化装置の構成が複雑になる。そのため、簡易な構成の装置によりエレクトレット化する観点からは、あらかじめ前記積層シートをエレクトレット化し、得られたエレクトレットシートを用いてフィルターを構成することが好ましい。 <Electret conversion>
The laminate sheet may be electretized before, after, or during the filter manufacturing process, which will be described later. In order to uniformly electret a three-dimensional structure, 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.
　エレクトレット化の方法は特に制限されず、公知の方法にしたがって実施することができる。例えば、積層シートの表面にコロナ放電するか、又はパルス状高電圧を印加するエレクトロエレクトレット化法、積層シートの両面を誘電体で保持し、両面に直流高電圧を
加える方法、積層シートにγ線、電子線等の電離放射線を照射するラジオエレクトレット化法等が挙げられる。 The electretization method is not particularly limited, and can be carried out according to known methods. For example, 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 γ-ray is applied to the laminated sheet. , a radio electret method in which ionizing radiation such as an electron beam is applied.
＜＜エレクトロエレクトレット化法＞＞
　エレクトロエレクトレット化法としては、例えば直流高圧電源に接続された印加電極とアース電極の間に積層シートを固定するバッチ方式か、又は通過させる搬送方式が好ましい。エレクトロエレクトレット化方法では、針状の電極を等間隔で無数に配置するか、金属ワイヤーを使用し、アース電極には平らな金属板か金属ロールを使用することが好ましい。 << Electro electret method >>
As the electro-electretization 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. In 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.
　エレクトレット化には、直流式コロナ放電処理を用いることがより好ましい。
　図２は、直流式コロナ放電処理に使用される、バッチ方式のエレクトレット化装置の一例を示している。図２に示すように、エレクトレット化装置７０は、直流高圧電源７１に、針状の主電極（印加電極）７２と、平板状の対電極（アース電極）７３が接続されている。エレクトレット化装置７０では、主電極７２と対電極７３の間にエレクトレット化するシート１０（例えば前述の積層シート）を設置する。直流高圧電源７１により主電極７２と対電極７３間に直流高電圧を印加して、コロナ放電を生じさせることにより、シート１０に電荷を注入することができる。 DC corona discharge treatment is more preferably used for electretization.
FIG. 2 shows an example of a batch-type electretization apparatus used for DC corona discharge treatment. As shown in FIG. 2, 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 . In the electretization device 70 , 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 .
　主電極と対電極の間隔は、間隔が長いほど、電極間距離を均一に維持しやすいことから、１ｍｍ以上が好ましく、２ｍｍ以上がより好ましく、５ｍｍ以上がさらに好ましい。一方、主電極と対電極の間隔は、短いほどコロナ放電が発生しやすく、帯電層の帯電性の均一性が向上しやすいことから、５０ｍｍ以下が好ましく、３０ｍｍ以下がより好ましく、２０ｍｍ以下がさらに好ましい。そのため、主電極と対電極の間隔は１～５０ｍｍが好ましく、２～３０ｍｍがより好ましく、５～２０ｍｍがさらに好ましい。 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. On the other hand, 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. preferable. Therefore, 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.
　主電極と対電極との間に印加する電圧は、帯電層の絶縁性等の電気特性、エレクトレットシートに求める表面電位、比誘電率等の電気特性、主電極と対電極の形状や材質、主電極と対電極の間隔等により決定する。
　直流式コロナ放電処理によって帯電層に導入される電荷の量は、処理時に主電極と対電極に流れた電流量に依存する。電流量は両電極間の電圧が高いほど多くなる。そのため、印加電圧は、より高い処理効果を望む場合、帯電層が絶縁破壊しない程度に高く設定することが好ましい。一方、一般的な直流コロナ放電処理を想定した場合、印加電圧は、具体的には１～１００ｋＶが好ましく、３～７０ｋＶがより好ましく、５～５０ｋＶの範囲がさらに好ましく、１０～３０ｋＶが特に好ましい。 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. On the other hand, when assuming general DC corona discharge treatment, 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. .
　主電極側の極性はプラスでもマイナスでもよいが、主電極側をマイナス極性にした方が比較的安定したコロナ放電処理を行えるために好ましい。
　主電極と対電極の材質は、導電性の物質から適宜選択されるが、通常は鉄、ステンレス、銅、真鍮、タングステン等の金属製又はカーボン製の材料が用いられる。 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.
　前記積層シートは、エレクトレット化後に除電処理が施されていてもよい。除電処理において一時的に表面の電荷を減少又は除去することにより、エレクトレットシートからフィルターへの加工を含む製造工程での塵埃の吸着、シート同士の張り付き、シートと製造設備の張り付き等を回避しやすくなる。除電処理には、電圧印加式除電器（イオナイザ）、自己放電式除電器等の公知の除電装置を用いることができる。これら一般的な除電装置は、シート表面の電荷を減少又は除去することはできるが、シート内部に蓄積した電荷までは除去できないため、除電処理によりエレクトレットシートの静電吸着力が大きく影響を受けることはない。 The laminated sheet may be subjected to static elimination treatment after electretization. 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. Become. 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.
（積層シート及びエレクトレットシートの特性）
＜厚み＞
　前記帯電層の厚みは、好ましくは１０μｍ以上、より好ましくは２０μｍ以上、さらに好ましくは３０μｍ以上である。前記帯電層が厚いほど、帯電層に十分な電荷を蓄積できるため、帯電保持性の優れたエレクトレットシートが得られやすい。一方で、前記帯電層の厚みは、好ましくは３００μｍ以下、より好ましくは２００μｍ、より好ましくは１００μｍ以下である。帯電層が薄いほど、コルゲート加工等の波板状にするための曲げ加工の際に空孔がつぶれにくく、細かいピッチのコルゲート加工が容易となるため、集塵効果の高いフィルターが得られやすい。 (Characteristics of laminated sheet and electret sheet)
<Thickness>
The thickness of the charging layer is preferably 10 μm or more, more preferably 20 μm or more, still more preferably 30 μm 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. On the other hand, the thickness of the charging layer is preferably 300 μm or less, more preferably 200 μm or less, and more preferably 100 μm 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.
　前記機能層は、前記帯電層よりも薄いことが好ましい。前記機能層は前記帯電層よりも相対的に厚み方向の弾性変形がしにくい層であるため、前記機能層の厚みを抑えることで、前記積層シートの圧縮弾性率が低下せず、エネルギー変換効率を維持しやすくなる。
　前記機能層の厚みは、好ましくは０．１μｍ以上であり、より好ましくは１μｍ以上、さらに好ましくは２μｍ以上である。一方、前記機能層の厚みは、好ましくは１０μｍ以下、より好ましくは９μｍ以下、さらに好ましくは５μｍ以下である。前記機能層の厚みが０．１μｍ以上であれば、抗菌性、抗ウイルス性、及び防カビ性等の機能が発揮され易くなる傾向がある。また、前記機能層の厚みが１０μｍ以下であれば、前記積層シートに電荷注入する際に、フィルム内部の帯電層にまで電荷を到達させ易くなり、帯電性に優れる傾向がある。 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 μm or more, more preferably 1 μm or more, still more preferably 2 μm or more. On the other hand, the thickness of the functional layer is preferably 10 μm or less, more preferably 9 μm or less, still more preferably 5 μm or less. When the thickness of the functional layer is 0.1 μm 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 μm 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.
　また、前記帯電層の厚みと前記機能層の厚みの比率（帯電層／機能層）は、１．１～１０００であることが好ましく、２～３００であることがより好ましく、５～１５０であることがさらに好ましく、１０～５０であることが特に好ましい。なお同値は、前記帯電層及び前記機能層が多層構造の場合には、前期帯電層又は前記機能層を構成する各層の合計値から換算する。 The ratio of the thickness of the charging layer to the thickness of the functional layer (charging layer/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. When 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.
　前記エレクトレットシートの厚みは、好ましくは２０μｍ以上、より好ましくは３０μｍ以上、さらに好ましく４０μｍ以上である。前記エレクトレットシートが厚いほど、コルゲート加工した際に形状を維持しやすく、加工性に優れたエレクトレットシートが得られやすい。一方で、前記エレクトレットシートの厚みは、好ましくは４００μｍ以下、より好ましくは３００μｍ以下、さらに好ましくは２００μｍ以下である。前記エレクトレットシートが薄いと、コルゲート加工等によって折り曲げ加工がしやすく、形状の安定したフィルターが得られやすい。 The thickness of the electret sheet is preferably 20 µm or more, more preferably 30 µm or more, and even more preferably 40 µm 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. On the other hand, the thickness of the electret sheet is preferably 400 μm or less, more preferably 300 μm or less, and even more preferably 200 μm 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.
　前記エレクトレットシートの厚みは、ＪＩＳ－Ｋ７１３０：１９９９に準拠し、厚み計を用いて測定する。
　また、前記エレクトレットシートを構成する各層の厚みは、次のようにして測定することができる。測定対象試料を液体窒素にて－６０℃以下の温度に冷却する。ガラス板上に置いた試料に対して、カミソリ刃（シック・ジャパン（株）製、商品名：プロラインブレード）を直角に当てて切断し、断面観察用の試料を作成する。走査型電子顕微鏡（日本電子（株）製、商品名：ＪＳＭ－６４９０）を使用して、得られた試料の断面画像を観察し、空孔形状及び組成外観から各層の境界線を判別する。各層の境界線から、前記エレクトレットシートの総厚みに対する各層の厚み比率を算出する。厚み計で測定した前記エレクトレットシートの総厚みと、断面画像の倍率比及び各層の厚み比率から、各層の厚みを求める。 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. From the boundary line of each layer, 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.
＜空孔率＞
　前記積層シート及び前記エレクトレットシートは、内部に微細な空孔を有する。前記エレクトレットシート中、前記帯電層の空孔率が１～７０％のものが好ましい。上記空孔率は、電子顕微鏡で観察した前記エレクレットシートの断面の一定領域において、空孔が占める面積の比率より求められる。
　前記エレクトレットシートが内部に空孔を有することにより、空孔を含めた前記エレクトレットシート内部に電荷を閉じ込めやすく、前記エレクトレットシートから電荷が逃げにくいために、捕集効率が高く、捕集力の持続性に優れたフィルターが得られやすい。
　また、前記エレクトレットシート内部に空孔を有することは、前記エレクトレットシートの密度の低下につながるため、得られるフィルターの軽量化の観点からも好ましい。 <Porosity>
The laminated sheet and the electret sheet have fine pores inside. In the electret sheet, 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.
　前記帯電層の空孔率は、１％以上であることが好ましく、より好ましくは５％以上であり、さらに好ましくは２５％以上である。空孔率が大きいほど、帯電減衰速度が遅くなり、フィルター性能の持続性が向上しやすい。一方、前記帯電層の空孔率は、７０％以下であることが好ましく、より好ましくは６０％以下であり、さらに好ましくは５５％以下である。空孔率が小さいほど、互いに連通する空孔が減り、電荷の保持能力が向上する傾向がある。したがって、前記帯電層の空孔率は、上述したように１～７０％であることが好ましく、より好ましくは５～６０％であり、さらに好ましくは２５～５５％である。空孔率を上記範囲に制御することにより、埃等の吸着力が安定しやすい。 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. On the other hand, 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.
＜密度＞
　前記帯電層の真密度ρ０は、前記帯電層を構成している熱可塑性樹脂（Ａ）の融点あるいはガラス転移点温度よりも１０℃～１５０℃高い温度に設定した圧縮成形機を用いて、前記帯電層を３ＭＰａ以上の圧力で３分間以上加熱圧縮した後、２５℃以下に設定した圧縮成形機で３ＭＰａ以上の圧力で３分間以上冷却して、前記帯電層内の空孔を取り除き、次いで前記帯電層に使用している熱可塑性樹脂（Ａ）の融点あるいはガラス転移点温度よりも１０℃～７０℃低い温度に設定したオーブンを用いて２４時間以上状態調整した後、２３℃、相対湿度５０％の環境で２４時間以上状態調整を行い、ＪＩＳ－Ｋ－７１１２：１９９９に記載されている方法により測定する。 <Density>
The true density ρ 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.
　前記帯電層の密度は、前記帯電層を１０ｃｍ×１０ｃｍサイズに打ち抜き、その重量を測定することにより得られた坪量Ｗｆ（ｇ／ｃｍ２）と、ＪＩＳ－Ｋ－７１３０：１９９９に記載の定圧厚さ測定器を用いて測定した帯電層の厚みＴｆ（ｃｍ）を用い、下記の計算式によって求める。
      ρ ＝ Ｗｆ／Ｔｆ
        ρ  ：帯電層の密度（ｇ／ｃｍ３）
        Ｗｆ：帯電層の坪量（ｇ／ｃｍ２）
        Ｔｆ：帯電層の厚み（ｃｍ） The density of the charged layer is determined by the basis weight Wf (g/cm 2 ) obtained by punching the charged layer into a size of 10 cm×10 cm and measuring the weight thereof, and the constant pressure described in JIS-K-7130:1999. Using the thickness Tf (cm) of the charged layer measured with a thickness gauge, the thickness is obtained by the following formula.
ρ = Wf/Tf
ρ: Density of charged layer (g/cm 3 )
Wf: Basis weight of charging layer (g/cm 2 )
Tf: thickness of charging layer (cm)
＜剛軟度＞
　前記エレクレットシートの剛軟度は、好ましくは０．１～１ｍＮ、より好ましくは０．１２～０．８ｍＮ、さらに好ましくは０．１３～０．７ｍＮである。剛軟度が０．１ｍＮ以上であれば、前記エクレレットシート自体に腰があり、取り扱いが容易となる。一方、剛軟度が１ｍＮ以下であれば、高い搬送性が得られやすくなる。なお、本発明での剛軟度はＪＩＳ　Ｌ１０９６：２０１０による曲げ反発Ａ法（ガーレ法）に準拠して測定したものである。 <Bending resistance>
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.
＜体積抵抗率＞
　前記機能層は、体積抵抗率が１×１０１３～９×１０１７Ω・ｃｍであることが好ましく、１×１０１４～９×１０１５Ω・ｃｍであることがさらに好ましい。前記機能層の体積抵抗率が１×１０１３Ω・ｃｍ以上であると、エレクトレット化時に付与した電荷がフィルム表面を伝って移動しにくくなり、前記帯電層への電荷注入の効率の低下を抑えやすい。その結果、前記エレクトレットシート表面の電荷密度の低下、空間電荷密度の低下及び静電吸着性能の低下も抑えやすい。また、エレクトレット化に必要なエネルギーも減らすことができる。一方、前記機能層の体積抵抗率が９×１０１７Ω・ｃｍ以下であると、公知の材料を使用してこのような高絶縁性の表面を形成しやすく、コストも下げやすい。 <Volume resistivity>
The functional layer preferably has a volume resistivity of 1×10 13 to 9×10 17 Ω·cm, more preferably 1×10 14 to 9×10 15 Ω·cm. When the volume resistivity of the functional layer is 1×10 13 Ω·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. As a result, 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. Also, the energy required for electretization can be reduced. On the other hand, when the volume resistivity of the functional layer is 9×10 17 Ω·cm or less, it is easy to form such a highly insulating surface using a known material and to reduce the cost.
　前記機能層の表面抵抗率は、熱可塑性樹脂（Ｂ）として絶縁性に優れるポリオレフィン系樹脂の使用、熱可塑性樹脂（Ｂ）に配合する無機フィラーの種類又は量の調整等により、目的の範囲内に調整することができる。なお、本発明での体積抵抗率はＪＩＳ　Ｋ６９１１：２００６に準拠して測定したものである。 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.
＜水蒸気透過係数＞
　前記エレクトレットシートの水蒸気透過係数は、連通する空孔の有無を判断するものであり、水蒸気透過係数が大きければ、連通空孔表面や介在する水蒸気により電荷が放電されやすくなる。
　本発明のエレクトレットシートの水蒸気透過係数は、５．０ｇ・ｍｍ／ｍ２・２４ｈｒ以下が好ましく、４．０ｇ・ｍｍ／ｍ２・２４ｈｒ以下がより好ましく、３．０ｇ・ｍｍ／ｍ２・２４ｈｒ以下がさらに好ましい。水蒸気透過係数が５．０ｇ・ｍｍ／ｍ２・２４ｈｒ以下であると、電荷保持能力の低下を抑えやすく、フィルターとしての捕集効率が得られやすい。一方、前記エレクトレットシートを構成する各層が含有する熱可塑性樹脂、例えばポリオレフィン系樹脂からなるフィルムの水蒸気透過係数が０．１ｇ・ｍｍ／ｍ２・２４ｈｒ前後であることから、前記エレクトレットシートの水蒸気透過係数は、通常０．０１ｇ・ｍｍ／ｍ２・２４ｈｒ以上であり、０．０５ｇ・ｍｍ／ｍ２・２４ｈｒ以上であってもよく、０．１ｇ・ｍｍ／ｍ２・２４ｈｒ以上であってもよい。 <Water vapor permeability coefficient>
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. More preferred are: When the water vapor permeability coefficient is 5.0 g·mm/m 2 ·24 hr or less, it is easy to suppress the deterioration of the charge retention ability, and the collection efficiency as a filter can be easily obtained. On the other hand, since 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.
　水蒸気透過係数（ｇ・ｍｍ／ｍ２・２４ｈｒ）は、ＪＩＳ－Ｚ－０２０８：１９７６に準拠したカップ法により、温度４０℃、相対湿度９０％の条件にて透湿度（ｇ／ｍ２・２４ｈｒ）を測定し、シートの厚み（ｍｍ）から換算して求めた値である。前記エレクトレットシートの前記機能層は前記帯電層に蓄積した電荷が外部に逃げないように、絶縁する効果を有するが、その効果が低い場合は水蒸気透過係数が高くなり、電荷の保持能力が劣ることとなる。また、前記エレクトレットシート中の空孔の多くが連通している場合、同様に水蒸気透過係数が高くなり、電荷の保持能力が劣ることとなる。 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.
＜算術平均粗さ（Ｒａ）＞
　前記エレクトレットシートの表面は、フィルター製造時の加工性の観点からは平滑であることが好ましいことから、前記機能層の表面の算術平均粗さ（Ｒａ）は、５μｍ以下が好ましく、４μｍ以下がより好ましい。一方、フィルターが吸着した異物を保持する観点からは、前記エレクトレットシートの表面は凹凸を有することが好ましく、当該凹凸は前記機能剤が前記エレクトレットシートの表面に露出することにより形成されていることが好ましい。そのため、前記機能層の表面の算術平均粗さ（Ｒａ）は、０．０１μｍ以上が好ましく、０．０３μｍ以上がより好ましい。
　前記機能層の表面の算術平均粗さ（Ｒａ）を所望の値にするためには、素材自体が上記範囲のものを選定するか、或いはエンボス加工やシボ加工により、表面に上記範囲の起伏を加えることが好ましい。なお、本発明での算術平均粗さ（Ｒａ）はＪＩＳ－Ｂ－０６０１：２００３に準拠して測定したものである。 <Arithmetic mean roughness (Ra)>
Since the surface of the electret sheet is preferably smooth from the viewpoint of workability during filter production, the arithmetic mean roughness (Ra) of the surface of the functional layer is preferably 5 μm or less, more preferably 4 μm or less. preferable. On the other hand, 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 μm or more, more preferably 0.03 μm or more.
In order to set the arithmetic mean roughness (Ra) of the surface of the functional layer to a desired value, 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.
＜比誘電率＞
　前記エレクトレットシートは、フィルターを構成する部材であるとともに、電荷がフィルター外部に逃げないように封じこめる役割を有する。この電荷を封じ込める能力は前記、エレクトレットシートの比誘電率ε（エレクトレットシートの誘電率εＢと真空の誘電率ε０の比εＢ／ε０）で表すことができる。
　通常、前記エレクトレットシートの比誘電率が低いほど、同じ電荷量であっても表面電位が高くなる傾向があり、埃塵の集塵効果に優れたフィルターが得られやすい。エレクトレットシートの比誘電率は、誘電率が低い絶縁性の樹脂を含むこと、又はエレクトレットシートの内部に空孔を形成することにより、より低い所望の範囲とすることができる。 <Dielectric constant>
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 ε of the electret sheet (the ratio εB/ε0 of the dielectric constant εB of the electret sheet to the dielectric constant ε0 of vacuum).
Normally, the lower the dielectric constant of the electret sheet, the higher the surface potential tends to be, even if the charge amount is the same, and it is easy to obtain a filter with excellent dust collecting effect. 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.
　前記エレクトレットシートの比誘電率は、１．１以上が好ましく、１．２以上がより好ましく、１．２５以上がさらに好ましい。比誘電率が大きいほど、前記帯電層の空孔率が７０％以下の前記エレクトレットシートで、電荷の保持能力が低下しにくいフィルターが得られやすい。一方、前記エレクトレットシートの比誘電率は、２．５以下が好ましく、２．２以下がより好ましく、２．０以下がさらに好ましく、１．９以下が特に好ましい。比誘電率が小さいほど、エレクトレットシートが電荷を長期間保持しやすく、フィルターの静電吸着力が低下しにくくなる傾向がある。 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 higher the relative permittivity, the easier it is to obtain a filter in which the charge retention capacity is less likely to decrease with the electret sheet having the charging layer with a porosity of 70% or less. On the other hand, 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.
　前記エレクトレットシートの比誘電率の測定法は、測定周波数の範囲によって選択される。測定周波数が１０Ｈｚ以下の場合には超低周波ブリッジが用いられ、１０Ｈｚ～３ＭＨｚの場合には変成器ブリッジが用いられ、１ＭＨｚを越える場合には並列Ｔ型ブリッジ、高周波シェリングブリッジ、Ｑメーター、共振法、定在波法、空洞共振法等が用いられる。また、測定周波数の交流信号に対して、回路部品に対する電圧・電流ベクトルを測定し、この値から静電容量を算出するＬＣＲメーター等でも測定できる。 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, resonant method, standing wave method, cavity resonance method, etc. are used. 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.
　前記エレクトレットシートの比誘電率の測定装置としては、５Ｖ程度の電圧を印加でき、測定周波数が任意に選択できる測定装置が好ましい。このような測定装置によれば、周波数を変更することにより、試料の周波数依存性が把握でき、適正使用範囲の指標にできる。このような測定装置としては、例えばＡｇｉｌｅｎｔ　Ｔｅｃｈｎｏｌｏｇｉｅｓ社の「４１９２Ａ　ＬＦ　ＩＭＰＥＤＡＮＣＥ　ＡＮＡＬＹＺＥＲ」、横河電機（株）社の「ＬＣＲメーター４２７４Ａ」、日置電機（株）社の「ＨＩＯＫＩ　３５２２　ＬＣＲハイテスター」等が挙げられる。 As the 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.
　前記エレクトレットシートの比誘電率の測定時には、まずシートの両面に銀導電性塗料を塗工するか、真空金属蒸着をすることにより電極を形成して試料を得る。次いで、温度２３℃、相対湿度５０％の環境条件下で試料に５Ｖの電圧を印加し、１０Ｈｚ～１ＭＨｚの周波数で静電容量（Ｃｘ）を測定し、周波数１００ｋＨｚの静電容量（Ｃｘ）の測定値を代表値として得る。得られた静電容量（Ｃｘ）から、比誘電率（εｒ）を下記式により算出する。
      εｒ ＝ Ｃｘ × ｈ ／（ε０ × Ａ）
      εｒ：  エレクトレットシートの比誘電率（－）
      Ｃｘ：  エレクトレットシートの静電容量（ｐＦ）
      ｈ  ：  エレクトレットシートの厚み（ｍ）
      ε０ ：  真空の誘電率  ＝  ８．８５４（ｐＦ／ｍ）
      Ａ  ：  主電極の面積  ＝  ３．８４８×１０－４（ｍ２） When measuring the dielectric constant of the electret sheet, first, 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 (εr) is calculated by the following formula.
εr = Cx × h / (ε 0 × A)
εr: Relative permittivity of electret sheet (-)
Cx: Electrostatic capacity of electret sheet (pF)
h: Thickness of electret sheet (m)
ε 0 : Dielectric constant of vacuum = 8.854 (pF/m)
A: Area of main electrode = 3.848 × 10 -4 (m 2 )
＜表面電位＞
　前記エレクトレットシートのコロナ処理直後の表面電位（静的表面電位ＥＡ）は０．３ｋＶ以上が好ましく１．０ｋＶ以上であることがより好ましく、１５ｋＶ以下であることが好ましく、１０ｋＶ以下であることがより好ましい。 <Surface potential>
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.
　前記エレクトレットシートをコロナ処理後、温度４０℃、湿度５０％ＲＨの環境下で１週間間放置した時の表面電位（静的表面電位ＥＡ）は０．３ｋＶ以上が好ましく１．０ｋＶ以上であることがより好ましく、１５ｋＶ以下であることが好ましく、１０ｋＶ以下であることがより好ましい。 After the corona treatment, 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.
　表面電位測定器としては、例えば「（株）キーエンス製、高精度静電気センサＳＫ」や「トレック・ジャパン（株）製、高圧高速表面電位計　モデル３４１Ｂ」などが用いられる。測定は気温、湿度の影響を受けないように２３℃、相対湿度５０％の環境下で行う。また、周囲物品の影響を受けないように、エレクトレットシートを中吊にした状態で行う。 As 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. In addition, the electret sheet is suspended in the middle so as not to be affected by surrounding articles.
（フィルター）
　本発明のフィルターは、波板状の前記エレクトレットシートと、平板状の前記エレクトレットシートと、が交互に積層されて、空気の流路が形成され、積層された各エレクトレットシートが互いに熱融着された接合部を有する。前記フィルターに使用されるエレクトレットシートは、前記エレクトレットシートであるため、抗菌性、抗ウイルス性、及び防カビ性の少なくともいずれか一つの機能特性を有し、帯電保持性に優れる。 (filter)
In the filter of the present invention, 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.
　図３は、本発明の一実施形態であるフィルターの構成を示している。
　図３に示すように、本実施形態のフィルター５０は、波板状のエレクトレットシート１１と平板状のエレクトレットシート１１が交互に繰り返し積層されてなる。波板状と平板状の各エレクトレットシート１１の立体構造によって、フィルター５０には、空気の流路となる空間が設けられている。フィルター５０は、各エレクトレットシート１１がその接触部分で互いに熱融着された接合部１１ａを有する。 FIG. 3 shows the configuration of a filter that is one embodiment of the present invention.
As shown in FIG. 3, 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.
（フィルターの製造方法）
　空気の流路が設けられた前記フィルターの立体構造は、コルゲート加工等によって形成できる。立体構造を形成した後、積層した各エレクトレットシートが接触する部分のヒートシール層（Ｂ）を熱融着させることで、シート同士を接合し、フィルターの立体構造を固定できる。接合方法は特に限定されず、例えばコルゲート加工時にエレクトレットシートを積層し、加熱した加圧ロールでシート表面を加熱することにより、隣接するエレクトレットシートの接触部分を熱融着させて接合部を設けることができる。また、積層された各エレクトレットシートを電熱線カッター等で断裁することで断裁部分を熱融着させることができる。 (Filter manufacturing method)
The three-dimensional structure of the filter provided with air flow paths can be formed by corrugating or the like. After the three-dimensional structure is formed, 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. For example, 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. Also, by cutting the laminated electret sheets with a heating wire cutter or the like, the cut portions can be heat-sealed.
＜コルゲート加工＞
　前記エレクトレットシートをコルゲート加工して前記フィルターを製造する場合は、通常の紙製ハニカムコアの製造に使用するハニカムマシン等、通常の紙製段ボールの製造に使用するシングルフェーサー等のコルゲートマシンを、適宜利用して製造することができる。 <Corrugated processing>
When manufacturing the filter by corrugating the electret sheet, 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.
　紙製段ボールの製造に用いるシングルフェーサーを使用する場合は、前記エレクトレットシートを、噛み合った一対の歯車の間に供給して屈曲させることにより、波板状にコルゲート加工する。次いで、コルゲート加工した前記波板状のシート（以下、「フルート」と称することがある）の片面又は両面に、コルゲート加工されていない平板状の前記エレクトレットシート（以下、「ライナー」と称することがある）を熱融着させることによって、コルゲートコアが得られる。この時、ライナーとしては、Ｔダイから溶融押出成形等した別の樹脂シートを使用してもよいが、フィルターの空間電荷密度を向上させる観点から、フルートと同様に前記エレクトレットシートを使用することがより好ましい。 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.
（フィルターの特性）
＜流路断面率＞
　前記フィルターの空気の流路断面率は、フィルターの断面に対して空気の流路が占める割合である。したがって、流路断面率は、その値が低いほどフィルターの強度が増加するとともに、空気の流通に対する抵抗となって圧力損失が増加する傾向がある。
　具体的には、空気の流路断面率は、フィルターの断面積から、シート基材厚みと流路成形に使用したシート基材の長さの積であるシート基材の断面積を除算することで得られる。また、流路断面率は、断面の画像観察から求めることもできる。
　空気の流通に対する圧力損失を少なくする観点から、前記フィルターの空気の流路断面率は、１０％以上が好ましく、３０％以上がより好ましく、５０％以上がさらに好ましい。一方、フィルターの強度の観点から、前記フィルターの空気の流路断面率は、９９％以下が好ましく、９７％以下がより好ましく、９５％以下がさらに好ましい。 (Filter characteristics)
<Flow channel cross-sectional ratio>
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.
Specifically, 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.
From the viewpoint of reducing pressure loss in air circulation, 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. On the other hand, from the viewpoint of the strength of the filter, 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.
＜空間電荷密度＞
　前記フィルターの空間電荷密度は、フィルターの空間容積を占める電荷の総量を示す。空間電荷密度は、値が高いほど、塵や埃の捕集性能が高いことを示す。具体的には、前記フィルターの空間電荷密度は、前記フィルターのシート基材が有する電荷量を該シート基材が形成する空間容積で除算することで得られる。前記フィルターのシート基材が有する電荷量は実測値を用い、空間容積はフィルター形状から論理的に求めてもよく、前記フィルターの密度から求めてもよい。
　例えば、空間容積をフィルター形状から論理的に求める場合、その単位空間を縦１ｃｍ×横１ｃｍ×高さ１ｃｍの立方体と規定する。エレクトレットフィルターの流路と垂直に切断した断面の縦１ｃｍ×横１ｃｍの正方形（単位面積）当たりに存在するエレクトレットシートの総長さＬｓ（ｃｍ／ｃｍ２）を、フィルター形状から計算又は測定して求める。 <Space charge density>
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. Specifically, 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.
For example, when the spatial volume is logically obtained from the filter shape, 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. .
　単位空間容積当たりに存在するエレクトレットシートの総面積Ｓｓ（ｃｍ２／ｃｍ３）は、それぞれ断面正方形（単位面積）当たりに存在するエレクトレットシートの総長さＬｓに、シートの幅として単位空間の奥行きを乗じた値であるから、次式で表されるように、ＳｓとＬｓは同値である。
  Ｓｓ（ｃｍ２／ｃｍ３）＝ Ｌｓ（ｃｍ／ｃｍ２）×１ｃｍ／１ｃｍ
                      ＝ Ｌｓ（ｃｍ／ｃｍ２） 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.
Ss ( cm2 / cm3 ) = Ls (cm/ cm2 ) x 1 cm/1 cm
= Ls (cm/cm 2 )
　一方、エレクトレットシートの単位面積当たりの電荷量Ｑｓ（ｎＣ／ｃｍ２）は実測で求められる。従って、単位空間当たりに存在するエレクトレットシートの電荷量Ｑａ（ｎＣ／ｃｍ３）、すなわち空間電荷密度は、次式で表される。
  Ｑａ（ｎＣ／ｃｍ３）＝ Ｓｓ（ｃｍ２／ｃｍ３）× Ｑｓ（ｎＣ／ｃｍ２）
                     ＝ Ｌｓ（ｃｍ／ｃｍ２）× Ｑｓ（ｎＣ／ｃｍ２） On the other hand, 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 )
　上記の通り、空間電荷密度は、断面の単位面積当たりのエレクトレットシートの総長さＬｓと、エレクトレットシートの単位面積当たりの電荷量Ｑｓの積から求めることができる。なお、フィルターが多種類のエレクトレットシートから構成される場合、例えば１，２・・・ｎ種類のエレクトレットシートから構成される場合は、単位空間当たりに存在するエレクトレットシートの電荷量Ｑａは、それぞれのエレクトレットシートの単位空間当たりの電荷量Ｑａ１，Ｑａ２，・・・Ｑａｎの和で表される。 As described above, 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. When 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.
　前記フィルターの空間電荷密度が高いほど、同フィルターにおける捕集効率が高くなり、フィルターに求める捕集効率が一定であれば、空気の流路の長さ（フィルターの奥行き・厚み）を短くすることができる。一方、空気の流路の長さが一定であれば、フィルターの寿命を長くすることができる。
　前記フィルターの空間電荷密度は、捕集効率を高める観点から、その下限は１０ｎＣ／ｃｍ３以上が好ましく、５０ｎＣ／ｃｍ３以上がより好ましく、８０ｎＣ／ｃｍ３以上がさらに好ましく、１１０ｎＣ／ｃｍ３以上が特に好ましい。一方、前記エレクトレットシートが保有できる電荷量の制約から、その上限は５０００ｎＣ／ｃｍ３以下が好ましく、前記エレクトレットシートの製造上の簡便さから、２０００ｎＣ／ｃｍ３以下がより好ましく、１０００ｎＣ／ｃｍ３以下がさらに好ましい。 The higher the space charge density of the filter, the higher the collection efficiency of the filter. can be done. On the other hand, if the length of the air flow path is constant, the life of the filter can be lengthened.
From the viewpoint of increasing collection efficiency, 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. On the other hand, 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.
　以下に製造例、調製例、実施例、比較例及び試験例を用いて、本発明をさらに具体的に説明する。以下に示す材料、使用量、割合、操作等は、本発明の精神から逸脱しない限り適宜変更することができる。したがって、本発明の範囲は以下に示す具体例に制限されるものではない。なお、以下に記載される％は、特記しない限り質量％である。 The present invention will be explained more specifically below using Production Examples, Preparation Examples, Examples, Comparative Examples and Test Examples. The materials, amounts used, proportions, operations, etc. shown below can be changed as appropriate without departing from the spirit of the present invention. Accordingly, the scope of the invention is not limited to the specific examples shown below. In addition, % described below is mass % unless otherwise specified.
　各実施例及び比較例では下記原料を使用した。
（原料）
＜熱可塑性樹脂＞
・プロピレン単独重合体（日本ポリプロ（株）製、商品名：ノバテックＰＰ　ＦＹ４、ＭＦＲ（２３０℃、２．１６ｋｇ荷重）：５ｇ／１０分、融点：１６５℃）
＜フィラー＞
・重質炭酸カルシウム（備北粉化工業（株）製、商品名：ソフトン１８００、平均粒子径：１．２μｍ）
＜機能剤＞
・金属担持体（石塚硝子（株）製、商品名：イオンピュアＺＡＦ　ＨＳ、平均粒子径：１μｍ）
・ホタテ貝焼成粉末（（株）日研化学研究所、商品名：シェルナチュレ、平均粒子径：６．４μｍ、水酸化カルシウム３５質量％配合） The following raw materials were used in each example and comparative example.
(material)
<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 μm)
<Functional agent>
- Metal carrier (manufactured by Ishizuka Glass Co., Ltd., trade name: Ion Pure ZAF HS, average particle size: 1 μm)
・ Scallop calcined powder (Nikken Kagaku Kenkyusho Co., Ltd., trade name: Shell Nature, average particle size: 6.4 μm, containing 35% by mass of calcium hydroxide)
＜樹脂組成物の製造＞
［製造例］
（樹脂組成物（ａ））
　表１に記載のプロピレン単独重合体を単独でそのまま使用した。 <Production of resin composition>
[Manufacturing example]
(Resin composition (a))
Propylene homopolymers listed in Table 1 were used alone as they were.
（樹脂組成物（ｂ））
　プロピレン単独重合体、及び重質炭酸カルシウムを、表１に示すように配合し、２１０℃に設定した２軸混練機にて溶融混練した。次いで、２３０℃に設定した押出機にてストランド状に押し出し、冷却後にストランドカッターにて切断してペレットを作成し、以降の製造において使用した。 (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.
（樹脂組成物（ｃ）～（ｈ））
　プロピレン単独重合体、及び機能剤を、表１に示すように配合し、２１０℃に設定した２軸混練機にて溶融混練した。次いで、２３０℃に設定した押出機にてストランド状に押し出し、冷却後にストランドカッターにて切断してペレットを作成し、以降の製造において使用した。 (Resin Compositions (c) to (h))
A propylene homopolymer and a functional agent 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.
　表１は、樹脂組成物（ａ）～（ｈ）の組成を示す。
Figure JPOXMLDOC01-appb-T000001
 Table 1 shows the compositions of resin compositions (a) to (h).
Figure JPOXMLDOC01-appb-T000001
［製造例１］
　樹脂組成物（ｂ）を２３０℃に設定した押出機で溶融混練した後、２５０℃に設定した押出ダイスに供給してシート状に押し出し、これを冷却装置により６０℃まで冷却して無延伸シートを得た。この無延伸シートを１３５℃に加熱し、ロール群の周速差を利用して縦方向に５倍延伸して単層１軸延伸シートを得た。次いで、樹脂組成物（ｃ）を２３０℃に設定した押出機で溶融混練した後、押出ダイスよりシート状に押し出し、前記単層１軸延伸シートの第１面に積層し、２層構造の積層シートを得た。得られた２層構造の積層シートを６０℃まで冷却し、テンターオーブンを用いて再び約１５０℃に加熱して横方向に８．５倍延伸した後、さらにオーブンで１６０℃まで加熱して熱処理を行った。次いで、６０℃まで冷却し、耳部をスリットして２層構造（層構成：ｃ／ｂ、各層厚み：５／７５μｍ、各層延伸軸数：１軸／２軸）の積層シートを得た。同シートは厚みが８０μｍであった。 [Production Example 1]
After melt-kneading the resin composition (b) with an extruder set at 230 ° C., it is supplied to an extrusion die set at 250 ° C. and extruded into a sheet, which is cooled to 60 ° C. by a cooling device to form an unstretched sheet. got This non-stretched sheet was heated to 135° C. and stretched 5 times in the longitudinal direction by utilizing the difference in peripheral speed of the roll group to obtain a monolayer uniaxially stretched sheet. Next, 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. did Then, 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 μm, number of stretching axes of each layer: 1 axis/2 axes). The sheet had a thickness of 80 μm.
［製造例２～８］
　樹脂組成物（ｂ）及び（ｃ）の代わりに、それぞれ表２に記載の樹脂組成物を使用したこと、各層の厚みを表２に記載のとおり変更したこと以外は、製造例１と同様に２層構造の積層シートを得た。
　得られた積層シートはいずれも厚み８０μｍであった。 [Production Examples 2 to 8]
In the same manner as in Production Example 1, except that the resin compositions described in Table 2 were used instead of the resin compositions (b) and (c), respectively, and the thickness of each layer was changed as described in Table 2. A laminate sheet having a two-layer structure was obtained.
All of the laminated sheets thus obtained had a thickness of 80 μm.
［製造例９］
　樹脂組成物（ｅ）を用いてメルトブローン不織布（目付１０ｇ／ｍ２、繊維径６．５μｍ）を作製した。
　得られた不織布は厚みが８０μｍであった。 [Production Example 9]
A meltblown nonwoven fabric (basis weight: 10 g/m 2 , fiber diameter: 6.5 µm) was produced using the resin composition (e).
The obtained nonwoven fabric had a thickness of 80 μm.
［評価］
（厚み）
　積層シート及び不織布の厚み（全厚）は、ＪＩＳ Ｋ７１３０：１９９９に準拠し、定圧厚さ測定器（(株)テクロック製、商品名：ＰＧ－０１Ｊ）を用いて測定した。また、積層シートにおける各層の厚みは、測定対象試料を液体窒素にて－６０℃以下の温度に冷却し、ガラス板上に置いた試料に対してカミソリ刃（シック・ジャパン(株)製、商品名：プロラインブレード）を直角に当て切断し断面観察用の試料を作成し、得られた試料を走査型電子顕微鏡（日本電子(株)製、商品名：ＪＳＭ－６４９０）を使用して断面観察を行い、組成外観から熱可塑性樹脂組成物ごとの境界線を判別して、積層シートの全厚に観察される各層厚み比率を乗算して求めた。 [evaluation]
(thickness)
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.). In addition, 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. or lower and placing the sample on a glass plate with a razor blade (manufactured by Sic Japan Co., Ltd., product A sample for cross-sectional observation is prepared by cutting at a right angle with a proline blade), and the obtained sample is cross-sectioned using a scanning electron microscope (manufactured by JEOL Ltd., trade name: JSM-6490). Observation was performed, and the boundary line for each thermoplastic resin composition was determined from the appearance of the composition, and the total thickness of the laminated sheet was multiplied by the thickness ratio of each layer observed.
（空孔率）
　積層シート及び不織布における帯電層の空孔率（％）は、電子顕微鏡で観察した積層シート及び不織布の断面の一定領域において、空孔が占める面積の比率より求めた。測定対象の積層シート及び不織布の任意の一部を切り取り、エポキシ樹脂で包埋して固化させた後、ミクロトームを用いて測定対象の印刷用紙の面方向に垂直に切断し、その切断面が観察面となるように観察試料台に貼り付けた。観察面に金又は金－パラジウム等を蒸着し、電子顕微鏡にて１０００倍の拡大倍率において積層シート及び不織布の空孔を観察し、観察した領域を画像データとして取り込んだ。得られた画像データの画像処理を画像解析装置にて行い、各層間の境界を判別して帯電層の一定領域における空孔部分の面積率（％）を求めた。任意の１０箇所の観察における測定値を平均して、帯電層の空孔率（％）とした。 (Porosity)
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.
（剛軟度）
　積層シート及び不織布の剛軟度は、ＪＩＳ Ｌ１０９６：２０１０に準拠し、温度２３℃湿度５０％ＲＨの環境下で、ＭＤ方向について、ガーレ剛軟度試験機（大栄科学精器製作所(株)製、商品名：ＧＡＳ－１００）を用いて測定した。 (bending resistance)
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).
（体積抵抗率）
　積層シート及び不織布の体積抵抗率は、２３℃、相対湿度５０％の条件下で、ＪＩＳ　Ｋ６９１１：２００６に準拠し２重リング法の電極を用いて測定した。 (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.
（水蒸気透過係数）
　積層シート及び不織布の水蒸気透過係数はＪＩＳ－Ｚ－０２０８に準拠して、カップ法により、４０℃、９０％ＲＨにて測定した。得られた透湿度（ｇ／ｍ２・２４ｈｒ）と積層シート及び不織布の厚み（ｍｍ）とから、水蒸気透過係数（ｇ・ｍｍ／ｍ２・２４ｈｒ）を求めた。 (Water vapor permeability coefficient)
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.
（機能層表面の算術平均粗さ）
　積層シート及び不織布の機能層表面の算術平均粗さＲａ（μｍ）は、ＪＩＳ Ｂ０６０１：２００３に準拠し、三次元粗さ測定器（小坂研究所社製、商品名：ＳＥ－３ＡＫ）、及び解析装置（小坂研究所社製、商品名：ＳＰＡ－１１）を用いて測定した。 (Arithmetic mean roughness of functional layer surface)
The arithmetic mean roughness Ra (μm) 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).
　各実施例及び比較例の積層シート及び不織布の厚み、積層シート及び不織布における帯電層の空孔率、積層シート及び不織布の剛軟度、体積抵抗率、水蒸気透過係数、及び機能層表面の算術平均粗さを測定した結果を表２に示す。
Figure JPOXMLDOC01-appb-T000002
 Thickness of laminated sheet and nonwoven fabric, porosity of charged layer in laminated sheet and nonwoven fabric, bending resistance, volume resistivity, water vapor permeability coefficient of laminated sheet and nonwoven fabric, and arithmetic mean of functional layer surface of each example and comparative example Table 2 shows the results of roughness measurements.
Figure JPOXMLDOC01-appb-T000002
（エレクトレットシートの製造）
（実施例１）
　図３に示す構成と同様のエレクトレット化装置において、主電極の針間距離１０ｍｍ、主電極－アース電極間距離１０ｍｍに設定し、アース電極盤上に製造例１により得られた積層シートの裏面がアース電極面と接触するように置いた。次いで、表３に示す放電電圧にて積層シートに電荷注入を行って、実施例１のエレクトレットシートを得た。 (Manufacture of electret sheet)
(Example 1)
In an electret forming apparatus having the same configuration as shown in FIG. 3, the distance between the needles of the main electrodes was set to 10 mm, and the distance between the main electrode and the ground electrode was set to 10 mm, and 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.
（実施例２～７及び比較例１）
　製造例２～７により得られた樹脂フィルムを用いたこと及び機能層と帯電層の厚みを変更したこと以外は、実施例１と同様にして実施例２～７のエレクトレットシートを得た。また、製造例８により得られた樹脂フィルムを用いたこと以外は、実施例１と同様にして比較例１のエレクトレットシートを得た。 (Examples 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.
（比較例２）
　製造例９で得られた不織布を水流荷電方式にてエレクトレット化して、比較例２のエレクトレットシートを得た。 (Comparative example 2)
The nonwoven fabric obtained in Production Example 9 was electretized by a water current charging method to obtain an electret sheet of Comparative Example 2.
［評価］
（比誘電率）
　各実施例及び比較例で得たエレクトレットシートの一方の面に、導電性塗料（（株）藤倉化成製、製品名：ドータイトＤ－５００）を直径７０ｍｍの円となるようにスクリーン印刷し、常温で２４時間以上硬化させて主電極を形成し、次いで反対側の面に、同導電性塗料を直径１００ｍｍの同心円となるようにスクリーン印刷し、常温で２４時間以上硬化させて対電極を形成して、試料を得た。
　静電容量の測定装置としては、インピーダンスアナライザ（Ｋｅｙｓｉｇｈｔ　Ｔｅｃｈｎｏｌｏｇｉｅｓ社製、製品名：Ｅ４９９０Ａ）を使用した。温度２３℃、相対湿度５０％の環境条件下で各エレクトレットシートに１Ｖの電圧を印加し、２０Ｈｚ～１ＭＨｚの範囲の周波数で静電容量を測定し、周波数１００ｋＨｚでの静電容量（Ｃｘ）を代表値として測定した。次いで同値と別途測定した厚みを用いて、以下の式により比誘電率を計算により求めた。
      εｒ ＝ Ｃｘ × ｈ ／（ε０ × Ａ）
      εｒ：  エレクトレットシートの比誘電率（－）
      Ｃｘ：  エレクトレットシートの静電容量（ｐＦ）
      ｈ  ：  エレクトレットシートの厚み（ｍ）
      ε０ ：  真空の誘電率  ＝  ８．８５４（ｐＦ／ｍ）
      Ａ  ：  主電極の面積  ＝  ３．８４８×１０－４（ｍ２） [evaluation]
(relative permittivity)
Conductive paint (manufactured by Fujikura Kasei Co., Ltd., product name: Dotite D-500) was screen-printed on one side of the electret sheet obtained in each example and comparative example so as to form a circle with a diameter of 70 mm. to form a main electrode by curing at room temperature for 24 hours or more, then, on the opposite side, the same conductive paint is screen-printed so as to form a concentric circle with a diameter of 100 mm, and cured at room temperature for 24 hours or more to form a counter electrode. to obtain the sample.
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.
εr = Cx × h / (ε 0 × A)
εr: Relative permittivity of electret sheet (-)
Cx: Electrostatic capacity of electret sheet (pF)
h: Thickness of electret sheet (m)
ε 0 : Dielectric constant of vacuum = 8.854 (pF/m)
A: Area of main electrode = 3.848 × 10 -4 (m 2 )
（表面電位）
　アルミ板をアースとして、表面電位計（春日電機（株）製、製品名：ＫＳＤ－３０００）のプローブと紙面との間隔が１ｃｍとなるようにして、表面電位を５点測定し、その平均を値とした。以下、測定条件を示す。
　電荷注入直後の表面電位Ａ：バッチ式帯電装置で帯電させた直後の試料を、除電ブラシを用いて表面の電荷を除去し、直ちに前記アルミ板上に乗せ、表面電位を測定した。
　電荷注入して４０℃１週間経過後の表面電位Ｂ：容器に溜めたイオン交換水中にサンプルを浸漬して１分間静置し、サンプルを取り出してティッシュで余分な水をふき取り、温度４０℃、相対湿度５０％の条件下で1週間吊るして乾燥させた試料を前記アルミ板上に乗せ、表面電位を測定した。 (Surface potential)
Using an aluminum plate as a ground, the surface potential was measured at 5 points with a surface potential meter (manufactured by Kasuga Denki Co., Ltd., product name: KSD-3000) so that the distance between the probe and the paper surface was 1 cm, and the average was calculated. value. The measurement conditions are shown below.
Surface potential A immediately after charge injection: The surface charge of the sample immediately after being charged by the batch-type charging device was removed using a charge removing brush, and the surface potential was measured by immediately placing it on the aluminum plate.
Surface potential B after 1 week of charge injection at 40°C A sample dried by hanging for one week under conditions of relative humidity of 50% was placed on the aluminum plate, and the surface potential was measured.
（抗菌性）
　ＪＩＳＺ２８０１に準じた抗菌試験を、試験菌株として黄色ぶどう球菌、及び大腸菌を用いて行った。両試験菌株において、抗菌活性値が２．０以上である場合を（＋）、２．０未満である場合を（－）として抗菌性を評価した。 (antibacterial)
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.
（防カビ性）
　ＪＩＳＺ２９１１　プラスチック製品の試験　方法Ｂに準じたかび抵抗性試験を、試験カビとしてＡｓｐｅｒｇｉｌｌｕｓ　ｎｉｇｅｒ，　Ｐｅｎｉｃｉｌｌｉｕｍ　ｐｉｎｏｐｈｉｌｕｍ，　ｐａｅｃｉｌｏｍｙｃｅｓ　ｖａｒｉｏｔｉｉ，　Ｔｒｉｃｈｏｄｅｒｍａ　ｖｉｒｅｎｓ，　Ｃｈｅａｔｏｍｉｕｍ　ｇｌｏｂｏｓｕｍを用いて行った。各試験かびにおいて、４週後のかび発育状態が二軸延伸ポリプロピレンフィルム（フタムラ化学社製　ＦＯＳ－ＡＱ　非コロナ処理面）と比較し、発育が抑えられている場合を（＋）、同程度のレベルである場合を（－）として防カビ性を評価した。 (anti-mold)
A mold resistance test according to JISZ2911 Plastic Product Test Method B was performed using Aspergillus niger, Penicillium pinophilum, paecilomyces variotii, Trichoderma virens, and Cheatomium globosum as test fungi. In each test mold, the state of mold growth after 4 weeks is compared with a biaxially oriented polypropylene film (FOS-AQ non-corona-treated surface manufactured by Futamura Chemical Co., Ltd.), and (+) indicates that growth is suppressed. The mold resistance was evaluated with (-) indicating the level.
　各実施例及び比較例で得たエレクレットシートの比誘電率、表面電位、抗菌性、及び防カビ性を測定した結果を表３に示す。 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.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
（フィルターの製造）
　図４に示すように、金属製のラックギア２１（山ピッチ３．０ｍｍ、山高さ３．５ｍｍ）、金属製のピニオンギア２２及び加圧ロール２３を使用して、製造例６と製造例８の積層シートを次のようにしてコルゲート加工し、それぞれ２０枚のコルゲートシートを得た。 (Manufacture of filters)
As shown in FIG. 4, 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.
　コルゲート加工時、図５に示すように、ホットプレート２４上にラックギア２１を置き、ラックギア２１の表面温度が１２０℃になるように加熱し、幅１０ｃｍ、長さ２０ｃｍのフルート用積層シート２５をラックギア２１の上に置いた。次いで、図６に示すように、オーブンで６０℃に加熱したピニオンギア２２を手で転がして、フルート用積層シート２５の形状をラックギア２１の表面形状と同様の形状に変形させた。図７に示すように、幅１０ｃｍ長さ１５ｃｍライナー用積層シート２６を、先に変形させたフルート用積層シート２５上に配置し、オーブンで６０℃に加熱した加圧ロール２３を手で転がして、積層シート同士を熱融着した。なお、製造例１の積層シートは、フルート用積層シート２５とライナー用積層シート２６のいずれの場合においても、樹脂組成物（ｂ）の層を常に下側に配置して加工した。 During corrugating, as shown in FIG. 5, 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. Next, as shown in FIG. 6 , 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 . As shown in FIG. 7, 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. In both cases of the laminated sheet for flute 25 and the laminated sheet for liner 26 of Production Example 1, the layer of the resin composition (b) was always arranged on the lower side.
　次に、図２に示す構成と同様のエレクトレット化装置において、主電極の針間距離１０ｍｍ、主電極－アース電極間距離１０ｍｍに設定し、アース電極盤上に上記コルゲートシートの平坦な面がアース電極面と接触するように置いて、２０ｋｖの印加電圧にて電荷注入を行った。２０枚すべてのコルゲートシートを積層した後、厚みが２０ｍｍとなるように、約２００℃に設定した電熱線カッターを用いて熱融着しながら断裁して実施例８及び比較例３のフィルターを製造した。 Next, in an electret forming apparatus having a configuration similar to that shown in FIG. It was placed in contact with the electrode surface, and charge injection was performed with an applied voltage of 20 kv. After laminating all 20 corrugated sheets, a heating wire cutter set at about 200° C. was used to cut the corrugated sheet to a thickness of 20 mm while being heat-sealed to produce the filters of Example 8 and Comparative Example 3. did.
［評価］
（空間電荷密度）
　実施例８及び比較例３で得たフィルターを用いて、その空気の流路方向と垂直となる様にカッターを用いて断面を作成し、同断面のデジタルカメラ撮影により得た拡大画像を得て、これを画像解析装置（（株）ニレコ製　商品名：ＬＵＺＥＸＲ　ＡＰ）を使用して、エレクトレット化シートの単位面積当たりの総長さ（Ｌｓ）を得た。
　次いで、エレクトレット化シートの単位面積当たりの総長さ（Ｌｓ）とエレクトレット化シートの単位面積当たりの電荷量（Ｑｓ）から、下記の計算式よりフィルターの空間電荷密度（Ｑａ）を計算により求めた。
　　Ｑａ＝Ｌｓ×Ｑｓ
　　　Ｑａ：フィルターの空間電荷密度（ｎＣ／ｃｍ３）
　　　Ｌｓ：エレクトレットシートの単位面積当たりの総長さ（ｃｍ／ｃｍ２）
　　　Ｑｓ：エレクトレットシートの単位面積当たりの電荷量（ｎＣ／ｃｍ２） [evaluation]
(space charge density)
Using the filters obtained in Example 8 and Comparative Example 3, a cross section was created using a cutter so as to be perpendicular to the direction of the air flow path, and an enlarged image of the cross section obtained by photographing with a digital camera was obtained. , and an image analyzer (trade name: LUZEXR AP manufactured by Nireco Corporation) was used to obtain the total length (Ls) per unit area of the electret sheet.
Then, the space charge density (Qa) of the filter was calculated from the total length (Ls) per unit area of the electretized sheet and the charge amount (Qs) per unit area of the electretized sheet by the following formula.
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 )
（フィルター性能補集率）
　実施例８及び比較例３で得たフィルターを用いて、幅５０ｍｍ、高さ５０ｍｍ、長さ５０ｍｍの正立方体になる様に、段ボール用カッターで断裁して、評価用フィルター３８を作成した。
　次いで図８に示す捕集率測定装置に評価用フィルター３８を開口断面が上を向く様に設置し、その下には評価用フィルター３８との間隔が５ｍｍとなる様に受け皿４１を設置し、更にその上にφ４０ｍｍ×長さ１００ｍｍのガラス管４０を設置した。
　評価用粉体として表面処理炭酸カルシウム（丸尾カルシウム（株）製、商品名：カルファイン２００）を１．０ｇ充填した粉体供給ビン３９から、評価用フィルター３８に評価用粉体が均一に落下する様に全量供給し、粉体供給後にガラス管４０の上部から風速が１ｍ／ｓｅｃとなる様に乾燥空気を１分間流した後に、評価用フィルター３８、粉体供給ビン３９、ガラス管４０、受け皿４１の各重量を測定して、下記の計算式より捕集率（Ｅｐ）を求めた。
　　Ｅｐ＝（Ｗｆａ－Ｗｆ０）／（（Ｗｂ０－Ｗｂａ）－（Ｗｐａ－Ｗｐ０））×１００
　　　　Ｅｐ：捕集率（％）
　　　Ｗｆ０：評価用フィルターの試験前重量
　　　Ｗｆａ：評価用フィルターの試験後重量
　　　Ｗｂ０：紛体供給ビンの試験前重量
　　　Ｗｂａ：紛体供給ビンの試験後重量
　　　Ｗｐ０：ガラス管の試験前重量
　　　Ｗｐａ：ガラス管の試験後重量
　尚、粉体供給ビン３９は図９に示す様な構造であり、ビン４２に取り付けた蓋４３には開口部が設けてあり、蓋４３の開口部には２００メッシュの平織金網４４を取り付けて使用した。 (Filter performance collection rate)
Using the filters obtained in Example 8 and Comparative Example 3, 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. After supplying the powder, dry air was flown for 1 minute from the upper part of the glass tube 40 so that the wind speed was 1 m / sec, and then the evaluation filter 38, the powder supply bottle 39, the glass tube 40 Each weight of the receiving tray 41 was measured, and the collection rate (Ep) was obtained from the following formula.
Ep=(Wfa−Wf0)/((Wb0−Wba)−(Wpa−Wp0))×100
Ep: collection rate (%)
Wf0: Weight of evaluation filter before test Wfa: Weight of evaluation filter after test Wb0: Weight of powder supply bottle before test Wba: Weight of powder supply bottle after test Wp0: Weight of glass tube before test Wpa: Glass tube test After weight The powder supply bottle 39 has a structure as shown in FIG. Installed and used.
　実施例８及び比較例３で得たフィルターの空間電荷密度、フィルター性能補集率、抗菌性、及び防カビ性を測定した結果を表４に示す。
Figure JPOXMLDOC01-appb-T000004
 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.
Figure JPOXMLDOC01-appb-T000004
　表３及び表４に示すように、実施例１～７のエレクトレットシート及び実施例８のフィルターは、抗菌性及び防カビ性を有し、比誘電率に優れるものであった。また、表面電位Ａ及び表面電子Ｂの値に差が認められなかったことから、吸湿等により帯電保持性等のエレクトレット性能低下が抑制されていることがわかる。一方、比較例１のエレクトレットシート及び比較例３のフィルターは、抗菌性及び防カビ性を有さなかった。また、比較例２のエレクトレットシートでは電荷注入直後の表面電位Ａに対して電荷注入して４０℃１週間経過後の表面電位Ｂの値が大きく低下しており、帯電保持性能を有さなかった。 As shown in Tables 3 and 4, 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. On the other hand, 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. .
　本出願は、２０２２年２月２８日に出願された日本特許出願である特願２０２２－０２９７５５号に基づく優先権を主張し、当該日本特許出願のすべての記載内容を援用する。 This application claims priority based on Japanese Patent Application No. 2022-029755, which is a Japanese patent application filed on February 28, 2022, and all descriptions of the Japanese patent application are incorporated.
１１　　エレクトレットシート
２　　　帯電層
３　　　機能層
５０　　フィルター

  11 electret sheet 2 charging layer 3 functional layer 50 filter

Claims (13)

  1. 　帯電層と機能層とを備えるエレクトレットシートであって、
    　前記帯電層が多孔質構造を有し、
    　前記機能層が、熱可塑性樹脂及び抗菌、抗ウイルス、及び防カビからなる群より選択される少なくとも１つの機能を有する機能剤を前記機能層全体の質量に対して１～４０質量％の範囲で含み、
    　前記エレクトレットシートの水蒸気透過係数が０．０１～５．０ｇ・ｍｍ／ｍ２・２４ｈｒである
    　エレクトレットシート。     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 based on the total mass of the functional layer. including
    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.
  2. 　前記帯電層の空孔率が１～７０％である
    　請求項１に記載のエレクトレットシート。     The electret sheet according to claim 1, wherein the charging layer has a porosity of 1 to 70%.
  3. 　前記帯電層がポリオレフィン系樹脂を含む
    　請求項１又は２に記載のエレクトレットシート。     The electret sheet according to claim 1 or 2, wherein the charging layer contains a polyolefin resin.
  4. 　前記機能層が延伸樹脂フィルム層である、
    　請求項１～３のいずれか一項に記載のエレクトレットシート。     The functional layer is a stretched resin film layer,
    The electret sheet according to any one of claims 1 to 3.
  5. 　前記機能層の厚みが０．１～１０μｍである
    　請求項１～４のいずれか一項に記載のエレクトレットシート。     The electret sheet according to any one of claims 1 to 4, wherein the functional layer has a thickness of 0.1 to 10 µm.
  6. 　前記機能剤を、エレクトレットシート全体の質量に対して０．０１～３質量％の範囲で含む
    　請求項１～５のいずれか一項に記載のエレクトレットシート。     The electret sheet according to any one of claims 1 to 5, containing the functional agent in a range of 0.01 to 3 mass% with respect to the mass of the entire electret sheet.
  7. 　前記機能層が少なくとも一方向に延伸されている延伸樹脂フィルム層である
    　請求項１～６のいずれか一項に記載のエレクトレットシート。     The electret sheet according to any one of claims 1 to 6, wherein the functional layer is a stretched resin film layer stretched in at least one direction.
  8. 　前記機能層のＪＩＳ　Ｋ６９１１：２００６に準拠して測定した体積抵抗率が、１×１０１３～９×１０１７Ω・ｃｍである
    　請求項１～７のいずれか一項に記載のエレクトレットシート。     The electret sheet according to any one of claims 1 to 7, wherein the functional layer has a volume resistivity of 1 × 10 13 to 9 × 10 17 Ω·cm as measured according to JIS K6911:2006.
  9. 　前記機能層の表面のＪＩＳ　Ｂ０６０１：２００３による算術平均粗さ（Ｒａ）が、０．０１～５μｍである、
    　請求項１～８のいずれか一項に記載のエレクトレットシート。     The surface of the functional layer has an arithmetic mean roughness (Ra) of 0.01 to 5 μm according to JIS B0601:2003.
    The electret sheet according to any one of claims 1-8.
  10. 　前記エレクトレットシートのＪＩＳ　Ｌ１０９６：２０１０による曲げ反発Ａ法（ガーレ法）による剛軟度が、０．１～１ｍＮである
    　請求項１～９のいずれか一項に記載のエレクトレットシート。     The electret sheet according to any one of claims 1 to 9, wherein the electret sheet has a bending resistance according to JIS L1096:2010 bending resistance A method (Gurley method) of 0.1 to 1 mN.
  11. 　前記エレクトレットシートの比誘電率が１．１～２．５である
    　請求項１～１０のいずれか一項に記載のエレクトレットシート。     The electret sheet according to any one of claims 1 to 10, wherein the electret sheet has a dielectric constant of 1.1 to 2.5.
  12. 　請求項１～１１のいずれか一項に記載のエレクトレットシートを備える
    　フィルター。     A filter comprising the electret sheet according to any one of claims 1 to 11.
  13. 　前記エレクトレットシートを用いて形成された流路を備え、前記流路の流路断面率が１０～９９％であり、前記フィルターの空間電荷密度が１０～５０００ｎＣ／ｃｍ３である
    　請求項１２に記載のフィルター。     13. The method according to claim 12, comprising a channel formed using the electret sheet, wherein the channel has a channel cross-sectional ratio of 10 to 99%, and the filter has a space charge density of 10 to 5000 nC/cm 3 . filter.
PCT/JP2023/007350 2022-02-28 2023-02-28 Electret sheet and filter WO2023163218A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03186309A (en) * 1989-12-13 1991-08-14 Shinagawa Nenryo Kk Air filter
JP2011038195A (en) * 2009-08-07 2011-02-24 Kuraray Kuraflex Co Ltd Composite fiber sheet
WO2018164207A1 (en) * 2017-03-10 2018-09-13 株式会社ユポ・コーポレーション Electret-treated sheet and filter
WO2019189349A1 (en) * 2018-03-30 2019-10-03 株式会社ユポ・コーポレーション Electretized sheet and filter

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03186309A (en) * 1989-12-13 1991-08-14 Shinagawa Nenryo Kk Air filter
JP2011038195A (en) * 2009-08-07 2011-02-24 Kuraray Kuraflex Co Ltd Composite fiber sheet
WO2018164207A1 (en) * 2017-03-10 2018-09-13 株式会社ユポ・コーポレーション Electret-treated sheet and filter
WO2019189349A1 (en) * 2018-03-30 2019-10-03 株式会社ユポ・コーポレーション Electretized sheet and filter

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