WO2023210759A1 - Electret and electret filter - Google Patents

Electret and electret filter Download PDF

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Publication number
WO2023210759A1
WO2023210759A1 PCT/JP2023/016690 JP2023016690W WO2023210759A1 WO 2023210759 A1 WO2023210759 A1 WO 2023210759A1 JP 2023016690 W JP2023016690 W JP 2023016690W WO 2023210759 A1 WO2023210759 A1 WO 2023210759A1
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Prior art keywords
electret
filter
liquid
present
pentene
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PCT/JP2023/016690
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French (fr)
Japanese (ja)
Inventor
義幸 北川
Original Assignee
東洋紡エムシー株式会社
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Publication of WO2023210759A1 publication Critical patent/WO2023210759A1/en

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Classifications

    • 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
    • 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
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H3/00—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length
    • D04H3/005—Synthetic yarns or filaments
    • D04H3/007—Addition polymers

Definitions

  • the present invention relates to electrets and electret filters.
  • Patent Document 1 Poly-4-methyl-1-pentene is known as a resin material suitable for electretization and having low surface tension.
  • electrets and electret filters that are used not only as a single resin but also as a mixture with polypropylene are known.
  • the present invention consists of the following configuration.
  • 1. An electret comprising poly-4-methyl-1-pentene, another type of polyolefin, and at least one hindered amine compound, characterized in that the electret is imparted with a charge by contact with a liquid. 2.
  • 4. The electret filter according to 3 above, which is a melt-blown nonwoven fabric. 5.
  • a method for producing an electret comprising:
  • an electret can be obtained that has excellent functions originally possessed by an electret and has reduced surface tension. Moreover, an electret filter can be obtained using this.
  • the electret of the present invention contains poly-4-methyl-1-pentene and polyolefins other than poly-4-methyl-1-pentene (other types of polyolefins), and is charged by a liquid contact method.
  • the poly-4-methyl-1-pentene used in the present invention is a polymer consisting only of 4-methyl-1-pentene units, or a copolymer mainly composed of poly-4-methyl-1-pentene. It means. There is no particular restriction as long as the required properties can be obtained, but the molar fraction of poly-4-methyl-1-pentene contained in the copolymer mainly composed of poly-4-methyl-1-pentene is It is preferably 80 mol% or more. It is more preferably 85 mol% or more, still more preferably 90 mol% or more, and most preferably 95 mol% or more. Within the above range, the properties of poly-4-methyl-1-pentene can be effectively expressed.
  • olefins may be included as components of the above copolymer, and examples thereof include ethylene, propylene, and ⁇ -olefins having 4 to 20 carbon atoms. More specific examples include propylene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene. It is also preferable that the above copolymer contains one or more types. In order to improve flame retardancy and rigidity, halogenated olefins and alicyclic olefins are also preferably used.
  • polyolefins used in the present invention include polyolefins that do not contain poly-4-methyl-1-pentene as a main component, and polyolefins that contain polyethylene, polypropylene, polybutene, polystyrene, alicyclic olefin, etc. as main components. It is preferable. From the viewpoint of melting point and electret properties, it is more preferable to use polystyrene or polypropylene as the main component, and most preferably to use polypropylene as the main component.
  • the mole fraction in the main component in copolymerization is preferably 80 mol% or more, more preferably 85 mol% or more, and even more preferably It is 90 mol% or more, most preferably 95 mol% or more. This is because it has excellent strength and workability as well as electret.
  • the degree of stereoregularity is preferably 85% or more, more preferably 90% or more, still more preferably 90% or more, and most preferably It is 95% or more.
  • isotactic or syndiotactic can be preferably used.
  • two or more types of polypropylene it is preferable that one or more types are contained in the contained polyolefin.
  • the content of other polyolefins in the electret of the present invention is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more. It is particularly preferable that the amount is 97% by mass or more, and most preferably 97% by mass or more.
  • the upper limit of the content ratio of other types of polyolefin resins is not particularly limited, and is, for example, 99.5% by mass or less, preferably 99% by mass or less.
  • the electret of the present invention is characterized in that it further contains a nitrogen-containing compound that promotes charging by contact with a liquid.
  • a nitrogen-containing compound is added to at least one of the polyolefin mainly composed of poly-4-methyl-1-pentene and the other polyolefin not mainly composed of poly-4-methyl-1-pentene. include.
  • the content of the nitrogen-containing compound in 100% by mass of the polyolefin resin is preferably 0.1 to 5% by mass, more preferably 0.5 to 3% by mass, and 0.75% by mass. Most preferably ⁇ 1.5% by weight.
  • the content of the nitrogen-containing compound in 100% by mass of the polyolefin resin is preferably 0.1 to 5% by mass, more preferably 0.5 to 3% by mass, and 0.75% by mass. Most preferably ⁇ 1.5% by weight.
  • the electret contains resins other than polyolefins, they can be distinguished because they dissolve in solvents/acids and bases, and have different dyeing properties, and quantitative methods such as DSC and NMR can be used. Even polyolefin resins can be identified.
  • the content of the nitrogen-containing compound is lower than 0.1 part by mass, the charge amount will be low, resulting in a decrease in filtration properties, and if it is higher than 5 parts by mass, the stability as an electret will be lost due to increased hydrophilicity. be exposed.
  • the nitrogen-containing compound is not particularly limited as long as it can obtain the above-mentioned desired properties, but is preferably a hindered amine compound containing at least one of a 2,2,6,6-tetramethylpiperidyl structure and a triazine structure. More preferably, the hindered amine compound includes a 2,2,6,6-tetramethylpiperidine structure and a triazine structure.
  • the hindered amine compound is not particularly limited, but for example, poly[ ⁇ 6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl ⁇ (2,2,6,6-tetramethyl-4-piperidyl)imino ⁇ hexamethylene ⁇ 2,2,6,6-tetramethyl-4-piperidyl)imino ⁇ ] (Kimasorb (registered trademark) 944LD, BASF Japan) ), dimethyl-1-(2hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethyl-4-piperidine polycondensate succinate (Tinuvin (registered trademark) 622LD, manufactured by BASF Japan), 2-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-2-butylpropanedioic acid bis[1,2,2,6,6-pentamethyl-4-piperidinyl] (Tinuvin (registered trademark
  • Chimasorb (registered trademark) 944LD or Chimasorb (registered trademark) 2020FD containing a 2,2,6,6-tetramethylpiperidine structure and a triazine structure are preferable.
  • the hindered amine compound one type is used alone. or two or more types may be used in combination.
  • the nitrogen-containing compound that promotes electrification used in the present invention may be present at least on the surface of the molded body, such as by applying a solution to the surface of the molded body, adhering powder, mixing a solution to polyolefin, mixing during polymerization, melt mixing, etc. It can be introduced by
  • the melt mixing method is superior from the viewpoint of homogeneity and processability, and it is a method of directly mixing with the resin during melt molding into the final shape, or a pre-prepared resin compound containing a charge enhancer can be used as is or diluted. It can be used as
  • the electret in the present invention contains a polyolefin mainly composed of poly-4-methyl-1-pentene, thereby achieving low surface tension even in the electret containing a charge enhancer made of a nitrogen-containing compound.
  • the charge enhancer is contained in either or both of the polyolefin containing poly-4-methyl-1-pentene as the main component and the polyolefin not containing poly-4-methyl-1-pentene as the main component, that is, other types of polyolefins. That's fine.
  • polyolefins It is preferably added as a diluent compound with other types of polyolefins, or added at the time of mixing polyolefins containing poly-4-methyl-1-pentene as a main component and other types of polyolefins. Particularly in the case where polyolefins are not compatible with each other, this is to make distribution to other types of polyolefins advantageous and to reduce surface tension.
  • the electret of the present invention can be used as a filter. Therefore, electret filters are also included in the scope of the present invention.
  • the electrets and electret filters of the present invention can be of any shape required.
  • the function of electret can be utilized as a surface coating layer for fibrous materials, films, extruded materials, porous membranes, powders, and other materials.
  • fibrous materials are particularly preferably used for electret filter applications.
  • the above-mentioned fibrous material is preferably a fiber aggregate, and examples of the fiber aggregate include fibrous materials such as woven or knitted fabrics made of long or short fibers, nonwoven fabrics, cotton-like materials, or fibrous materials obtained from stretched films. Examples include things.
  • a fiber aggregate is one that is recognized to have a fibrous form when the surface of the electret is observed using a device such as a scanning electron microscope or an optical microscope, and that at least some of the fibers constituting the fiber aggregate are Refers to a state in which the fibers are integrated by melting or entanglement between fibers.
  • the fiber aggregate is preferably a nonwoven fabric.
  • Methods for obtaining nonwoven fabrics include methods of forming single-component fibers, composite fibers such as core-sheath fibers and side-by-side fibers, and short fibers such as split fibers into sheets by carding, air-laid, wet paper-making methods, etc., and spunbond method using continuous fibers. It is possible to use conventionally known methods, such as forming a sheet using a melt-blowing method, an electrospinning method, or a force-spinning method.
  • Nonwoven fabrics obtained by spunbond method, melt blown method, melt electrospinning method, or melt force spinning method are more preferable from the viewpoint of not requiring treatment of residual solvent or spinning oil adhering to the surface, and spunbond method or melt blown method. Particularly preferred are nonwoven fabrics obtained by this method.
  • melt extrusion is preferably carried out at a temperature in the range of 150°C to 350°C, more preferably in the range of 170°C to 330°C, even more preferably in the range of 200 to 310°C. , most preferably 230°C to 300°C.
  • a temperature in the range of 150°C to 350°C more preferably in the range of 170°C to 330°C, even more preferably in the range of 200 to 310°C. , most preferably 230°C to 300°C.
  • the average fiber diameter of the fibers used in the fibrous material is preferably 0.001 to 100 ⁇ m, more preferably 0.05 to 50 ⁇ m, even more preferably 0.1 to 30 ⁇ m, and .3 to 25 ⁇ m is particularly preferred, and 0.5 to 20 ⁇ m is most preferred.
  • the average fiber diameter of the fibers is thicker than 100 ⁇ m, it is difficult to obtain a practical collection efficiency, and the efficiency decreases significantly when the charge decays.
  • the average fiber diameter of the fibers is smaller than 0.001 ⁇ m, it is difficult to produce a charged electret.
  • the above-mentioned fineness is calculated by measuring the diameters of 50 fibers in the same field of view using a scanning electron microscope so that there is no overlap of the fibers, and taking the geometric mean.
  • the above-mentioned fibrous material may be a uniform product made using a single manufacturing method and material, or may be a mixture using two or more materials with different manufacturing methods, materials, and fiber diameters.
  • the electret formation method in the present invention is not particularly limited as long as desired characteristics can be obtained when using the electret, but a method in which the fibrous material is brought into contact with or collides with a liquid (liquid contact charging method) is preferable.
  • the method makes it possible to obtain electrets with high filtration properties. More specifically, it is preferable to use a method in which a liquid is brought into contact with or collided with the fiber aggregate by a method such as suction, pressurization, or jetting.
  • the liquid to be brought into contact or collided with in the liquid contact charging method is not particularly limited as long as the desired characteristics can be obtained, but from the viewpoint of handling and performance, water is preferable. Instead of water, a liquid obtained by adding a subcomponent (component other than water) to water may be used, and the conductivity and pH of the liquid can be adjusted by adjusting the type and amount of the subcomponent added.
  • a subcomponent component other than water
  • the liquid to be contacted or collided with in the liquid contact charging method preferably has a pH of 1 to 11, more preferably a pH of 3 to 9, and even more preferably a pH of 5 to 7. Further, the liquid that is contacted or collided with in the liquid contact charging method preferably has an electrical conductivity of 100 ⁇ S/cm or less, more preferably 10 ⁇ S/cm or less, and even more preferably 3 ⁇ S/cm or less.
  • the QF value is 1.0 mmAq-1 or more, preferably 0.11 mmAq-1 or more, more preferably 0.12 mmAq-1 or more, and 0. It is more preferably 13 mmAq-1 or more, and most preferably 0.14 mmAq-1 or more.
  • an electret filter manufactured by a melt blowing method having an average fiber diameter of 0.5 to 5 ⁇ m exceeds the above QF value. If it is less than 1.00 mmAq-1, particles are not sufficiently captured by the electret, resulting in insufficient performance as a filter.
  • the QF value in this specification is calculated based on the ventilation resistance when aerating in the thickness direction of the filter at a wind speed of 10 cm/s and the number of particles counted in the particle size category of 0.3 to 0.5 ⁇ m using a laser particle counter. .
  • the particle collection efficiency at a wind speed of 10 cm/s can be adjusted in various ways depending on the required characteristics, but it is preferably 50% or more, and preferably 70% or more. More preferably, it is 90% or more, and most preferably 95% or more.
  • the particle collection efficiency refers to the number of particles counted in the particle size category 0.3 to 0.5 ⁇ m by a laser particle counter before and after passing through the filter, when the air is ventilated in the thickness direction of the filter at a wind speed of 10 cm/s. Calculated based on.
  • the ventilation resistance at a wind speed of 10 cm/s is preferably in the range of 0.05 to 50 mmAq, more preferably 0.2 to 30 mmAq, and most preferably 0.5 to 50 mmAq. It is 20mmAq. If the ventilation resistance is too small, the performance as a filter will be insufficient, and if the ventilation resistance is too large, the advantages as an electret filter will be lost.
  • the value of the filter medium quality factor (QF) in the above is generally 0.1 or less when a non-electret fibrous material is used, and for filter use, it is preferably 0.5 or more, and more preferably 1.0. or more, more preferably 1.1 or more, and most preferably 1.2 or more.
  • the material may be passed through a heat drying step, and in filter applications, a pleating step or long-term storage may be performed. Therefore, it is preferable that the above-mentioned filter medium quality factor (QF) is maintained not only immediately after electret formation but also after heat treatment.
  • a permeability test is performed using a test liquid with a surface tension of 30 to 58 mN/m consisting of a formamide-ethylene glycol monoethyl ether mixed system used according to JIS K6768. Defined by what you do. The standard also discloses the composition of a water-methanol mixed system, but because the composition and results lack continuity, a formamide system is used for evaluation. In addition, the inventor's studies have shown that the water-methanol mixed system has higher apparent liquid repellency.
  • the liquid repellency preferably achieved in the present invention is the surface tension of the test liquid that allows penetration within 10 seconds, and the representative value for PP melt blown is 36 mN/m in the unprocessed state and 36 mN/m, which is a polar substance. It is preferable that the liquid repellency is higher than the state of exceeding 37 mN/m when a nitrogen compound is added. Specifically, it is preferably 36 mN/m or less, more preferably 35 mN/m or less, and most preferably 34 mN/m or less. By reducing this value, it is possible to obtain liquid repellency equivalent to or higher than that of polypropylene that does not contain a nitrogen-containing compound.
  • the electret and electret filter of the present invention can be used in combination with other constituent members as necessary. That is, it can be used in combination with a pre-filter layer, a fiber protection layer, a reinforcing member, a functional fiber layer, etc.
  • a pre-filter layer and the fiber protective layer include spunbond nonwoven fabric, thermal bonded nonwoven fabric, and urethane foam.
  • the reinforcing member include thermal bond nonwoven fabric and various nets.
  • the functional fiber layer include antibacterial, antiviral, and colored fiber layers for identification and design purposes.
  • the electret and electret filter of the present invention can be widely used due to its functions such as dust collection, protection, ventilation, antifouling, and waterproofing.
  • functions such as antibacterial, antifungal, antiviral, and antiallergenic properties with separately added chemicals, we have developed products that are designed to protect dust masks, various air conditioning elements, air purifiers, cabin filters, and various other equipment. It can be suitably used as a filter.
  • Ventilation resistance A sample punched to 72 mm ⁇ was attached to an adapter with an effective ventilation diameter of 50 mm ⁇ , and piping with an inner diameter of 50 mm connected to a differential pressure gauge was connected above and below, and ventilation was conducted in the thickness direction of the sample at a speed of 10 cm/s without restriction. The pressure difference between the top and bottom of the sample was measured as ventilation resistance (pressure loss). The unit of ventilation resistance was mmAq.
  • Liquid repellency/penetration test Gently drop 100 ⁇ L of a wetting tension test liquid consisting of formamide and glycol monoethyl ether used in JIS K 6768 from 1 cm directly above the sample, and check the situation after 10 seconds. Confirm the surface tension value of the test liquid at which the difference between penetration and non-penetration occurs while changing the location so that the droplets do not come into contact with each other. Among the non-penetrating test liquids, the value with the smallest surface tension value was used as the value indicating the liquid repellency of the sample.
  • Example 1 90 parts by mass of polypropylene homopolymer, 10 parts by mass of polymethylpentene (brand name: DX820) manufactured by Mitsui Chemicals, Inc. as poly-4-methyl-1-pentene, and Chimassorb (registered trademark) 944 manufactured by BASF as a nitrogen-containing compound.
  • a mixture of 1 part by mass of the above was mixed in a blender and spun using a melt blowing device at a nozzle temperature of 330°C and an air temperature of 330°C to obtain a fiber sheet with a basis weight of 30 g/m 2 .
  • the fiber diameter was 5.3 ⁇ m.
  • the test liquid of 33 mN/m did not penetrate, but the test liquid of 32 mN/m penetrated, so the liquid repellency was 33 mN/m.
  • the obtained fiber sheet was charged by a contact charging method in which water having an electrical conductivity of 0.7 ⁇ S/cm and a pH of 6.8 was passed from the surface layer to the back surface. Thereafter, the electret sheet was obtained by air drying at 25°C.
  • the obtained electret sheet had a fiber diameter of 5.2 ⁇ m, and a filter medium quality factor QF obtained from ventilation resistance and particle permeability of 1.38.
  • Example 1 The same procedure as in Example 1 was carried out except that the nitrogen-containing compound Chimassorb (registered trademark) 944 manufactured by BASF was not added.
  • the fiber diameter was 5.4 ⁇ m, and as a result of the permeability test, a test liquid of 33 mN/m did not permeate, a test liquid of 32 mN/m permeated, and the liquid repellency was 33 mN/m.
  • the filter medium quality factor QF after electretization was 0.38.
  • Comparative example 2 The procedure was the same as Comparative Example 1 except that charging was performed using a corona discharge method instead of the liquid contact method.
  • the filter medium quality factor QF after electretization was 0.68.
  • Example 4 The procedure was the same as in Example 1, except that 100 parts by mass of polypropylene homopolymer and 1 part by mass of Chimassorb (registered trademark) 944 manufactured by BASF were used as the nitrogen-containing compound.
  • the fiber diameter was 4.8 ⁇ m, and as a result of the permeability test, the test liquid of 38 mN/m did not penetrate, but the test liquid of 37 mN/m penetrated, so the liquid repellency was 38 mN/m.
  • the filter medium quality factor QF after electretization was 1.25.
  • Example 1 has the same oil mist resistance and liquid repellency as an indicator of barrier properties, and is superior in filter medium quality factor.
  • Example 1 and Comparative Example 4 it was found that Example 1, by containing poly-4-methyl-1-pentene, achieved liquid repellency while obtaining a filter material quality factor equivalent to or higher than that of polypropylene alone. is found to be significantly superior.
  • the electret and electret filter of the present invention suppress performance deterioration when collecting mist-like substances or during contact, and have excellent barrier properties and collection properties.
  • it can be suitably used as a filter for dust-proof clothing, dust-proof masks, air purifiers, and the like.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Filtering Materials (AREA)
  • Electrostatic Separation (AREA)

Abstract

Conventional electret filters are produced using corona charging or liquid contact charging in which a pre-corona-charged filter is then charged by being brought into contact with water. Nevertheless, electret filters obtained by these methods have insufficient filtration performance and are a problematic alternative for a polypropylene electret. Moreover, electrets produced by liquid contact, which contain an agent for increasing electrification, pose a problem of elevated surface tension and increased wettability with liquids.　An electret according to the present invention contains poly-4-methyl-1-pentene, another type of polyolefin, and at least one hindered amine compound and is charged by liquid contact.　The above-mentioned problems can be solved by the electret according to the present invention.

Description

エレクトレット及びエレクトレットフィルターElectret and electret filter
　本発明はエレクトレット及びエレクトレットフィルターに関する。 The present invention relates to electrets and electret filters.
　従来、エレクトレットやエレクトレットフィルターが空気浄化や保護用途に広く用いられている。エレクトレットやエレクトレットフィルターはミスト状粒子を捕集した場合や液体がぬれ広がった場合には、バリア性や捕集性能が失われる。したがって、エレクトレットの遮蔽や中和、閉塞を抑制するために表面張力が小さく、液滴の濡れ広がりを抑制する素材が求められている。 Conventionally, electrets and electret filters have been widely used for air purification and protection purposes. Electrets and electret filters lose their barrier properties and collection performance when they collect mist-like particles or when liquid gets wet and spreads. Therefore, in order to suppress shielding, neutralization, and blockage of electrets, there is a need for a material that has low surface tension and suppresses wetting and spreading of droplets.
　エレクトレット化に適し、かつ表面張力の小さな樹脂素材としては、ポリ－４－メチル－１－ペンテンが知られている。また、単一樹脂で用いられるのみならず、ポリプロピレンとの混合物から得られるエレクトレット及びエレクトレットフィルターが知られている。（特許文献１及び特許文献２） Poly-4-methyl-1-pentene is known as a resin material suitable for electretization and having low surface tension. In addition, electrets and electret filters that are used not only as a single resin but also as a mixture with polypropylene are known. (Patent Document 1 and Patent Document 2)
日本国特許第２６３４２２４号Japanese Patent No. 2634224 日本国特許第３７３５６８７号Japanese Patent No. 3735687
　従来のエレクトレットフィルターは、コロナ荷電法もしくは予めコロナ荷電を行った後に、水を接触させて荷電する液体接触法が用いられる。しかしながら、当該方法により得られたエレクトレットフィルターは、ろ過性能が不足しており、ポリプロピレン製エレクトレットの代替を行うことは困難であった。また、液体接触法による帯電増強剤を含むエレクトレットは表面張力が上昇し、液体への濡れ性が増加するという問題がある。 Conventional electret filters use a corona charging method or a liquid contact method in which corona charging is performed in advance and then water is contacted to charge the filter. However, the electret filter obtained by this method lacks filtration performance, and it has been difficult to replace the polypropylene electret. Furthermore, electrets containing a charge enhancer produced by a liquid contact method have a problem in that their surface tension increases and their wettability to liquids increases.
　そこで、本発明者が鋭意検討したところ、下記手段により上記課題が解決できることを見出し、本発明に到達した。すなわち、本発明は以下の構成からなる。
１．ポリ－４－メチル－１－ペンテンと、他種ポリオレフィンと、少なくとも１種のヒンダードアミン化合物と含んで成るエレクトレットであり、液体接触により電荷付与されていることを特徴とするエレクトレット。
２．前記他種ポリオレフィンがポリプロピレンである上記１に記載のエレクトレット。
３．上記１または２のエレクトレットを用いたエレクトレットフィルター。
４．メルトブロー不織布である上記３に記載のエレクトレットフィルター。
５．ポリ－４－メチル－１－ペンテンと、他種ポリオレフィンと、少なくとも１種のヒンダードアミン化合物と含んで成るシート状物を形成する工程と、前記シート状物に液体接触により電荷付与する工程と、を含むこと特徴とするエレクトレットの製造方法。 Therefore, the inventor of the present invention made extensive studies and found that the above-mentioned problem could be solved by the following means, and thus arrived at the present invention. That is, the present invention consists of the following configuration.
1. 1. An electret comprising poly-4-methyl-1-pentene, another type of polyolefin, and at least one hindered amine compound, characterized in that the electret is imparted with a charge by contact with a liquid.
2. The electret according to 1 above, wherein the other polyolefin is polypropylene.
3. An electret filter using the above electret 1 or 2.
4. 3. The electret filter according to 3 above, which is a melt-blown nonwoven fabric.
5. a step of forming a sheet-like material comprising poly-4-methyl-1-pentene, another type of polyolefin, and at least one hindered amine compound; and a step of imparting a charge to the sheet-like material by liquid contact. A method for producing an electret, comprising:
　本発明により、エレクトレットの本来有する機能に優れ、かつ表面張力を低減したエレクトレットが得られる。また、これを用いたエレクレットフィルターを得られる。 According to the present invention, an electret can be obtained that has excellent functions originally possessed by an electret and has reduced surface tension. Moreover, an electret filter can be obtained using this.
　以下、本発明に関して具体的に説明する。しかしが、本発明は下記に限定される訳ではなく前・後記の趣旨に適合し得る範囲で適当に変更を加えて実施することも可能であり、それらはいずれも本発明の技術的範囲に包含される。 Hereinafter, the present invention will be specifically explained. However, the present invention is not limited to the following, and it is possible to carry out the invention by making appropriate changes within the scope compatible with the spirit of the preceding and following, and any of these may fall within the technical scope of the present invention. Included.
　本発明のエレクトレットは、ポリ－４－メチル－１－ペンテン及びポリ－４－メチル－１－ペンテン以外のポリオレフィン（他種ポリオレフィン）を含んでおり、液体接触法により電荷付与されている。 The electret of the present invention contains poly-4-methyl-1-pentene and polyolefins other than poly-4-methyl-1-pentene (other types of polyolefins), and is charged by a liquid contact method.
　本発明において用いられるポリ－４－メチル－１－ペンテンとは、４－メチル－１－ペンテン単位のみからなる重合体、もしくは、ポリ－４－メチル－１－ペンテンを主成分とする共重合体を意味するものである。必要特性が得られるものであれば特に制限されないが、ポリ－４－メチル－１－ペンテンを主成分とする共重合体中に含まれるポリ－４－メチル－１－ペンテンのモル分率としては８０モル％以上が好ましい。より好ましくは８５モル％以上であり、更に好ましくは９０モル％以上であり、最も好ましくは９５モル％以上である。上記範囲であると、ポリ－４－メチル－１－ペンテンとしての特性を有効に発現させることができる。 The poly-4-methyl-1-pentene used in the present invention is a polymer consisting only of 4-methyl-1-pentene units, or a copolymer mainly composed of poly-4-methyl-1-pentene. It means. There is no particular restriction as long as the required properties can be obtained, but the molar fraction of poly-4-methyl-1-pentene contained in the copolymer mainly composed of poly-4-methyl-1-pentene is It is preferably 80 mol% or more. It is more preferably 85 mol% or more, still more preferably 90 mol% or more, and most preferably 95 mol% or more. Within the above range, the properties of poly-4-methyl-1-pentene can be effectively expressed.
　上記の共重合体の成分としては各種オレフィンが含まれていてもよく、エチレン、プロピレン、炭素原子数４～２０のα－オレフィンなどを例示することができる。より具体的にはプロピレン、１－デセン、１－ドデセン、１－テトラデセン、１－ヘキサデセン、１－オクタデセン、１－エイコセンなどを例示することができる。上記共重合体においては１種以上含まれることも好ましい。難燃性や剛性を向上させるために、ハロゲン化オレフィン、脂環族オレフィンも好ましく用いられる。 Various olefins may be included as components of the above copolymer, and examples thereof include ethylene, propylene, and α-olefins having 4 to 20 carbon atoms. More specific examples include propylene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene. It is also preferable that the above copolymer contains one or more types. In order to improve flame retardancy and rigidity, halogenated olefins and alicyclic olefins are also preferably used.
　本発明に用いられる他種ポリオレフィンとしては、ポリ－４－メチル－１－ペンテンを主成分としないポリオレフィンであり、ポリエチレン、ポリプロピレン、ポリブテン、ポリスチレン、脂環族オレフィンなどを主成分とするポリオレフィンを用いることが好ましい。融点ならびにエレクトレット特性の観点から、ポリスチレンもしくはポリプロピレンを主成分とするものであることがより好ましく、最も好ましくはポリプロピレンを主成分とするものである。 Other polyolefins used in the present invention include polyolefins that do not contain poly-4-methyl-1-pentene as a main component, and polyolefins that contain polyethylene, polypropylene, polybutene, polystyrene, alicyclic olefin, etc. as main components. It is preferable. From the viewpoint of melting point and electret properties, it is more preferable to use polystyrene or polypropylene as the main component, and most preferably to use polypropylene as the main component.
　所望の特性が得られるものであれば特に制限されないが、他種ポリオレフィンにおいて、共重合における主たる成分におけるモル分率として８０モル％以上が好ましく、より好ましくは８５モル％以上であり、更に好ましくは９０モル％以上であり、最も好ましくは９５モル％以上である。エレクトレットならびに強度や加工性に優れるためである。 There is no particular restriction as long as the desired properties can be obtained, but in other types of polyolefins, the mole fraction in the main component in copolymerization is preferably 80 mol% or more, more preferably 85 mol% or more, and even more preferably It is 90 mol% or more, most preferably 95 mol% or more. This is because it has excellent strength and workability as well as electret.
　本発明において、他種ポリオレフィンとしてポリプロピレン樹脂が用いられる場合、立体規則性度が８５％以上であることが好ましく、より好ましくは９０％以上であり、更に好ましくは９０％以上であり、最も好ましくは９５％以上である。この場合、アイソタクチック、シンジオタクチックいずれでも好ましく用いることができる。２種以上のポリプロピレンを用いる場合には、含有されるポリオレフィン中に１種以上含まれることが好ましい。 In the present invention, when a polypropylene resin is used as the other polyolefin, the degree of stereoregularity is preferably 85% or more, more preferably 90% or more, still more preferably 90% or more, and most preferably It is 95% or more. In this case, either isotactic or syndiotactic can be preferably used. When using two or more types of polypropylene, it is preferable that one or more types are contained in the contained polyolefin.
　本発明のエレクトレット中における他種ポリオレフィンの含有率は８０質量％以上であることが好ましく、８５質量％以上であることがより好ましく、９０質量％以上であることがさらに好ましく、９５質量％以上であることが特に好ましく、９７質量％以上であることが最も好ましい。他種ポリオレフィン樹脂の含有割合の上限は特に限定されず、例えば９９．５質量％以下であり、９９質量％以下であることが好ましい。なお、シースコア繊維やサイドバイサイド繊維など繊維の左右や芯鞘で含有している樹脂を変えている場合には、ポリオレフィン樹脂が含まれている部分のみを本発明のエレクトレットとする。 The content of other polyolefins in the electret of the present invention is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more. It is particularly preferable that the amount is 97% by mass or more, and most preferably 97% by mass or more. The upper limit of the content ratio of other types of polyolefin resins is not particularly limited, and is, for example, 99.5% by mass or less, preferably 99% by mass or less. In addition, when the resin contained in the left and right sides of the fiber or the core and sheath, such as sheath core fiber or side-by-side fiber, is changed, only the portion containing the polyolefin resin is considered to be the electret of the present invention.
　本発明のエレクトレットは、さらに、液体接触による帯電を促進する含窒素化合物を含んでなることを特徴とする。本発明のエレクトレットにおいて、ポリ－４－メチル－１－ペンテンを主成分とするポリオレフィン、及び、ポリ－４－メチル－１－ペンテンを主成分としない他種ポリオレフィンの少なくとも一方に、含窒素化合物を含む。 The electret of the present invention is characterized in that it further contains a nitrogen-containing compound that promotes charging by contact with a liquid. In the electret of the present invention, a nitrogen-containing compound is added to at least one of the polyolefin mainly composed of poly-4-methyl-1-pentene and the other polyolefin not mainly composed of poly-4-methyl-1-pentene. include.
　本発明のエレクトレットにおいて、ポリオレフィン樹脂１００質量％中に対する含窒素化合物の含有率は０．１～５質量％であることが好ましく、０．５～３質量％であることが更に好ましく、０．７５～１．５質量％であることが最も好ましい。なお、エレクトレットにおいて２種類以上の繊維を混ぜている場合や一つの繊維に２種類以上の樹脂を混ぜている場合には、ポリオレフィン樹脂に含まれている含窒素化合物の割合のことを指す。エレクトレット中にポリオレフィン以外の樹脂が含まれている場合であっても、ポリオレフィン以外の樹脂は溶媒・酸塩基に溶解したり、染色性が異なるため、判別可能であり、ＤＳＣやＮＭＲなどの定量法でもポリオレフィン樹脂を判別可能である。含窒素化合物の含有割合が０．１質量部より低い場合には電荷量が低くなるため濾過特性が低下してしまい、５質量部より高い場合には親水性増大によりエレクトレットとしての安定性が失われる。 In the electret of the present invention, the content of the nitrogen-containing compound in 100% by mass of the polyolefin resin is preferably 0.1 to 5% by mass, more preferably 0.5 to 3% by mass, and 0.75% by mass. Most preferably ˜1.5% by weight. In addition, when two or more types of fibers are mixed in the electret or two or more types of resin are mixed in one fiber, it refers to the proportion of nitrogen-containing compounds contained in the polyolefin resin. Even if the electret contains resins other than polyolefins, they can be distinguished because they dissolve in solvents/acids and bases, and have different dyeing properties, and quantitative methods such as DSC and NMR can be used. Even polyolefin resins can be identified. If the content of the nitrogen-containing compound is lower than 0.1 part by mass, the charge amount will be low, resulting in a decrease in filtration properties, and if it is higher than 5 parts by mass, the stability as an electret will be lost due to increased hydrophilicity. be exposed.
　含窒素化合物は上述の所望の特性が得られるものであれば特に制限されないが、２，２，６，６－テトラメチルピペリジルの構造及びトリアジン構造の少なくとも一方を含むヒンダードアミン化合物であることが好ましく、ヒンダードアミン化合物は２，２，６，６－テトラメチルピペリジン構造及びトリアジン構造を含むことがより好ましい。 The nitrogen-containing compound is not particularly limited as long as it can obtain the above-mentioned desired properties, but is preferably a hindered amine compound containing at least one of a 2,2,6,6-tetramethylpiperidyl structure and a triazine structure. More preferably, the hindered amine compound includes a 2,2,6,6-tetramethylpiperidine structure and a triazine structure.
　ヒンダードアミン化合物としては、特に限定するわけではないが、例えば、ポリ［｛６－（１，１，３，３－テトラメチルブチル）アミノ－１，３，５－トリアジン－２，４－ジイル｝｛（２，２，６，６－テトラメチル－４－ピペリジル）イミノ｝ヘキサメチレン｛２，２，６，６－テトラメチル－４－ピペリジル）イミノ｝］（キマソーブ（登録商標）９４４ＬＤ、ＢＡＳＦジャパン社製）、コハク酸ジメチル－１－（２ヒドロキシエチル）－４－ヒドロキシ－２，２，６，６－テトラメチル－４－ピペリジン重縮合物（チヌビン（登録商標）６２２ＬＤ、ＢＡＳＦジャパン社製）、２－［［３，５－ビス（１，１－ジメチルエチル）－４－ヒドロキシフェニル］メチル］－２－ブチルプロパン二酸ビス［１，２，２，６，６－ペンタメチル－４－ピペリジニル］（チヌビン（登録商標）１４４、ＢＡＳＦジャパン社製）、ジブチルアミン１，３，５－トリアジン・Ｎ，Ｎ－ビス（２，２，６，６－テトラメチル－４－ピペリジル－１，６－ヘキサメチレンジアミン・Ｎ－（２，２，６，６－テトラメチル－４－ピペリジル）ブチルアミンの重縮合物（キマソーブ（登録商標）２０２０ＦＤＬ、ＢＡＳＦジャパン社製）、２－（４，６－ジフェニル－１，３，５－トリアジン－２－イル）－５－（ヘキシルオキシ）－フェノール（チヌビン（登録商標）１５７７ＦＦ、ＢＡＳＦジャパン社製）、（ＳＡＢＯ ＳＴＡＢ（登録商標） ＵＶ１１９、ＳＡＢＯ社製）などが挙げられる。中でも、２，２，６，６－テトラメチルピペリジン構造及びトリアジン構造を含むキマソーブ（登録商標）９４４ＬＤ又はキマソーブ（登録商標）２０２０ＦＤであることが好ましい。ヒンダードアミン化合物としては１種を単独で用いてもよく、２種以上を併用してもよい。 The hindered amine compound is not particularly limited, but for example, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{ (2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene {2,2,6,6-tetramethyl-4-piperidyl)imino}] (Kimasorb (registered trademark) 944LD, BASF Japan) ), dimethyl-1-(2hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethyl-4-piperidine polycondensate succinate (Tinuvin (registered trademark) 622LD, manufactured by BASF Japan), 2-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-2-butylpropanedioic acid bis[1,2,2,6,6-pentamethyl-4-piperidinyl] (Tinuvin (registered trademark) 144, manufactured by BASF Japan), dibutylamine 1,3,5-triazine/N,N-bis(2,2,6,6-tetramethyl-4-piperidyl-1,6-hexa Polycondensate of methylenediamine/N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine (Kimasorb® 2020FDL, manufactured by BASF Japan), 2-(4,6-diphenyl-1 , 3,5-triazin-2-yl)-5-(hexyloxy)-phenol (Tinuvin (registered trademark) 1577FF, manufactured by BASF Japan), (SABO STAB (registered trademark) UV119, manufactured by SABO), etc. Among them, Chimasorb (registered trademark) 944LD or Chimasorb (registered trademark) 2020FD containing a 2,2,6,6-tetramethylpiperidine structure and a triazine structure are preferable.As the hindered amine compound, one type is used alone. or two or more types may be used in combination.
　本発明において用いられる帯電を促進する含窒素化合物は、少なくとも成型体表面に存在していればよく、成型体表面への溶液塗布、粉末付着、ポリオレフィンへの溶液混合、重合時混合、溶融混合などにより導入することができる。 The nitrogen-containing compound that promotes electrification used in the present invention may be present at least on the surface of the molded body, such as by applying a solution to the surface of the molded body, adhering powder, mixing a solution to polyolefin, mixing during polymerization, melt mixing, etc. It can be introduced by
　上記のうち、均質性や加工性の観点から溶融混合法が優れており、最終形状への溶融成型時に樹脂とともに直接混合する方法もしくは、予め作成された帯電増強剤含有樹脂コンパウンドとしてそのまま、もしくは希釈して用いることができる。 Among the above, the melt mixing method is superior from the viewpoint of homogeneity and processability, and it is a method of directly mixing with the resin during melt molding into the final shape, or a pre-prepared resin compound containing a charge enhancer can be used as is or diluted. It can be used as
　本発明におけるエレクトレットは、ポリ－４－メチル－1－ペンテンを主成分とするポリオレフィンを含むことにより、含窒素化合物からなる帯電増強剤を含むエレクトレットにおいても低表面張力を実現する。帯電増強剤はポリ－４－メチル－1－ペンテンを主成分とするポリオレフィン、及び、ポリ－４－メチル－１－ペンテンを主成分としないポリオレフィンすなわち他種ポリオレフィンの両者もしくは一方いずれに含まれていればよい。好ましくは他種ポリオレフィンとの希釈用コンパウンドとして添加するか、ポリ－４－メチル－1－ペンテンを主成分とするポリオレフィンと他種ポリオレフィンとの混合時に、添加することが好ましい。特に、ポリオレフィン同士が相溶しない場合において、他種ポリオレフィンへの分配を有利とし、表面張力を低減するためである。 The electret in the present invention contains a polyolefin mainly composed of poly-4-methyl-1-pentene, thereby achieving low surface tension even in the electret containing a charge enhancer made of a nitrogen-containing compound. The charge enhancer is contained in either or both of the polyolefin containing poly-4-methyl-1-pentene as the main component and the polyolefin not containing poly-4-methyl-1-pentene as the main component, that is, other types of polyolefins. That's fine. It is preferably added as a diluent compound with other types of polyolefins, or added at the time of mixing polyolefins containing poly-4-methyl-1-pentene as a main component and other types of polyolefins. Particularly in the case where polyolefins are not compatible with each other, this is to make distribution to other types of polyolefins advantageous and to reduce surface tension.
　本発明のエレクトレットはフィルターとして用いることができる。よって、エレクトレットフィルターも本発明の範疇に含まれる。本発明のエレクトレット及びエレクトレットフィルターは、必要とされる必要なあらゆる形状とすることが可能である。例えば繊維状物、フィルム、押出成形材、多孔膜、粉末、他材料への表面コート層などとしてエレクトレットの機能を利用することができる。このうち、エレクトレットフィルター用途としては繊維状物が特に好ましく用いられる。 The electret of the present invention can be used as a filter. Therefore, electret filters are also included in the scope of the present invention. The electrets and electret filters of the present invention can be of any shape required. For example, the function of electret can be utilized as a surface coating layer for fibrous materials, films, extruded materials, porous membranes, powders, and other materials. Among these, fibrous materials are particularly preferably used for electret filter applications.
　上記繊維状物は繊維集合体であることが好ましく、繊維集合体としては、例えば、長繊維または短繊維からなる織編物、不織布、綿状物等の繊維状物や延伸フィルムから得られる繊維状物などが挙げられる。繊維集合体とは、エレクトレットを走査型電子顕微鏡、光学顕微鏡などの装置で表面観察した際に繊維状の形態であることが認められ、かつ、繊維集合体を構成する繊維同士の少なくとも一部が溶融もしくは繊維間の交絡により一体化している状態のことを指す。 The above-mentioned fibrous material is preferably a fiber aggregate, and examples of the fiber aggregate include fibrous materials such as woven or knitted fabrics made of long or short fibers, nonwoven fabrics, cotton-like materials, or fibrous materials obtained from stretched films. Examples include things. A fiber aggregate is one that is recognized to have a fibrous form when the surface of the electret is observed using a device such as a scanning electron microscope or an optical microscope, and that at least some of the fibers constituting the fiber aggregate are Refers to a state in which the fibers are integrated by melting or entanglement between fibers.
　エレクトレットをフィルターとして利用する場合は、繊維集合体は不織布であることが好ましい。不織布を得る方法としては、単成分繊維、芯鞘繊維やサイドバイサイド繊維といった複合繊維、分割繊維等の短繊維をカーディング、エアレイド、湿式抄紙法などによりシート化する方法、連続繊維よりなるスパンボンド法、メルトブローン法、エレクトロスピニング法、フォーススピニング法を用いてシート化する方法など、従来公知の方法を用いることが可能である。残溶剤の処理ならびに表面に付着する紡績油剤の処理などを必要としない観点からスパンボンド法、メルトブローン法、溶融エレクトロスピニング法、又は溶融フォーススピニング法で得られる不織布がより好ましく、スパンボンド法又はメルトブローン法で得られる不織布が特に好ましい。 When using the electret as a filter, the fiber aggregate is preferably a nonwoven fabric. Methods for obtaining nonwoven fabrics include methods of forming single-component fibers, composite fibers such as core-sheath fibers and side-by-side fibers, and short fibers such as split fibers into sheets by carding, air-laid, wet paper-making methods, etc., and spunbond method using continuous fibers. It is possible to use conventionally known methods, such as forming a sheet using a melt-blowing method, an electrospinning method, or a force-spinning method. Nonwoven fabrics obtained by spunbond method, melt blown method, melt electrospinning method, or melt force spinning method are more preferable from the viewpoint of not requiring treatment of residual solvent or spinning oil adhering to the surface, and spunbond method or melt blown method. Particularly preferred are nonwoven fabrics obtained by this method.
　上記溶融法による繊維もしくは不織布化においては、１５０℃～３５０℃の範囲で溶融押出することが好ましく、より好ましくは１７０℃～３３０℃の範囲であり、更に好ましくは２００～３１０℃の範囲であり、最も好ましくは２３０℃～３００℃である。この範囲とすることで、エレクトレットとしての電荷量ならびにろ過特性に優れたエレクトレットフィルターを得ることができる。 In producing fibers or non-woven fabrics by the above-mentioned melting method, melt extrusion is preferably carried out at a temperature in the range of 150°C to 350°C, more preferably in the range of 170°C to 330°C, even more preferably in the range of 200 to 310°C. , most preferably 230°C to 300°C. By setting it as this range, it is possible to obtain an electret filter with excellent charge amount and filtration characteristics as an electret.
　上記繊維状物に用いられる繊維の平均繊維直径は、０．００１～１００μｍであることが好ましく、０．０５～５０μｍであることがより好ましく、０．１～３０μｍであることがさらに好ましく、０．３～２５μｍであることが特に好ましく、０．５～２０μｍであることが最も好ましい。繊維の平均繊維直径が１００μｍよりも太い場合には実用的な捕集効率を得ることが困難であり、電荷減衰時の効率低下が大きい。繊維の平均繊維直径が０．００１μｍよりも細い場合には電荷を付与したエレクトレットを作製することが困難である。上記繊度は、走査型電子顕微鏡を使用し、同一視野で繊維の重複が無いように５０本の繊維径を計測し幾何平均にて算出する。 The average fiber diameter of the fibers used in the fibrous material is preferably 0.001 to 100 μm, more preferably 0.05 to 50 μm, even more preferably 0.1 to 30 μm, and .3 to 25 μm is particularly preferred, and 0.5 to 20 μm is most preferred. When the average fiber diameter of the fibers is thicker than 100 μm, it is difficult to obtain a practical collection efficiency, and the efficiency decreases significantly when the charge decays. When the average fiber diameter of the fibers is smaller than 0.001 μm, it is difficult to produce a charged electret. The above-mentioned fineness is calculated by measuring the diameters of 50 fibers in the same field of view using a scanning electron microscope so that there is no overlap of the fibers, and taking the geometric mean.
　上記繊維状物は単独の製法、素材からなる均一物であってもよく、製法、素材及び繊維径の異なる２種以上の素材を用いてなる混合物であってもよい。 The above-mentioned fibrous material may be a uniform product made using a single manufacturing method and material, or may be a mixture using two or more materials with different manufacturing methods, materials, and fiber diameters.
　本発明におけるエレクトレット化法はエレクトレットの使用時に所望の特性が得られるものであれば特に制限されないが、上記繊維状物に液体を接触又は衝突させる方法（液体接触荷電法）が好ましく、液体接触荷電法により高い濾過特性を有するエレクトレットを得ることができる。より具体的には、繊維集合体に吸引、加圧、噴出などの方法により液体を接触又は衝突させる方法であることが好ましい。 The electret formation method in the present invention is not particularly limited as long as desired characteristics can be obtained when using the electret, but a method in which the fibrous material is brought into contact with or collides with a liquid (liquid contact charging method) is preferable. The method makes it possible to obtain electrets with high filtration properties. More specifically, it is preferable to use a method in which a liquid is brought into contact with or collided with the fiber aggregate by a method such as suction, pressurization, or jetting.
　液体接触荷電法において接触又は衝突させる液体は所望の特性が得られるものであれば特に制限されないが、取扱い性ならびに性能面から鑑みて水であることが好ましい。水に代えて水に副成分（水以外の成分）を添加した液体を用いてもよく、該液体の導電率及びｐＨは、添加する副成分の種類や添加量等で調整可能である。 The liquid to be brought into contact or collided with in the liquid contact charging method is not particularly limited as long as the desired characteristics can be obtained, but from the viewpoint of handling and performance, water is preferable. Instead of water, a liquid obtained by adding a subcomponent (component other than water) to water may be used, and the conductivity and pH of the liquid can be adjusted by adjusting the type and amount of the subcomponent added.
　液体接触荷電法において接触又は衝突させる液体は、ｐＨが１～１１であることが好ましく、ｐＨが３～９であることがより好ましく、ｐＨが５～７であることがさらに好ましい。また、液体接触荷電法において接触又は衝突させる液体は、導電率が１００μＳ／ｃｍ以下であることが好ましく、１０μＳ／ｃｍ以下であることがより好ましく、３μＳ／ｃｍ以下であることがさらに好ましい。 The liquid to be contacted or collided with in the liquid contact charging method preferably has a pH of 1 to 11, more preferably a pH of 3 to 9, and even more preferably a pH of 5 to 7. Further, the liquid that is contacted or collided with in the liquid contact charging method preferably has an electrical conductivity of 100 μS/cm or less, more preferably 10 μS/cm or less, and even more preferably 3 μS/cm or less.
　本発明のエレクトレットをフィルターとして用いた場合、ＱＦ値は１．０ｍｍＡｑ-1以上であり、０．１１ｍｍＡｑ-1以上であることが好ましく、０．１２ｍｍＡｑ-1以上であることがより好ましく、０．１３ｍｍＡｑ-1以上であることが更に好ましく、０．１４ｍｍＡｑ-1以上であることが最も好ましい。とりわけ、メルトブロー法により製造された平均繊維径０．５～５μｍのエレクトレットフィルターにて上記のＱＦ値を上回ることが特に好ましい。１．００ｍｍＡｑ-1を下回るとエレクトレットによって粒子が十分に捕捉されておらずフィルターとしての性能が不十分となる。本明細書におけるＱＦ値は風速１０ｃｍ／ｓにてフィルター厚み方向に通気させた場合における通気抵抗及びレーザーパーティクルカウンターの粒子径区分０．３～０．５μｍでの個数計数値を基に計算される。 When the electret of the present invention is used as a filter, the QF value is 1.0 mmAq-1 or more, preferably 0.11 mmAq-1 or more, more preferably 0.12 mmAq-1 or more, and 0. It is more preferably 13 mmAq-1 or more, and most preferably 0.14 mmAq-1 or more. In particular, it is particularly preferable that an electret filter manufactured by a melt blowing method having an average fiber diameter of 0.5 to 5 μm exceeds the above QF value. If it is less than 1.00 mmAq-1, particles are not sufficiently captured by the electret, resulting in insufficient performance as a filter. The QF value in this specification is calculated based on the ventilation resistance when aerating in the thickness direction of the filter at a wind speed of 10 cm/s and the number of particles counted in the particle size category of 0.3 to 0.5 μm using a laser particle counter. .
　本発明のエレクトレットをフィルターとして用いた場合、風速１０ｃｍ／ｓにおける粒子捕集効率は必要特性に応じて種々調整することができるが、５０％以上であることが好ましく、７０％以上であることがより好ましく、９０％以上であることがさらに好ましく、９５％以上であることが最も好ましい。本明細書における粒子捕集効率は、風速１０ｃｍ／ｓにてフィルターの厚み方向に通気させた場合における、フィルター通過前後におけるレーザーパーティクルカウンターの粒子径区分０．３～０．５μｍでの個数計数値を基に計算される。 When the electret of the present invention is used as a filter, the particle collection efficiency at a wind speed of 10 cm/s can be adjusted in various ways depending on the required characteristics, but it is preferably 50% or more, and preferably 70% or more. More preferably, it is 90% or more, and most preferably 95% or more. In this specification, the particle collection efficiency refers to the number of particles counted in the particle size category 0.3 to 0.5 μm by a laser particle counter before and after passing through the filter, when the air is ventilated in the thickness direction of the filter at a wind speed of 10 cm/s. Calculated based on.
　本発明のエレクトレットをフィルターとして用いた場合、風速１０ｃｍ／ｓにおける通気抵抗は０．０５～５０ｍｍＡｑの範囲であることが好ましく、より好ましくは０．２～３０ｍｍＡｑであり、最も好ましくは０．５～２０ｍｍＡｑである。通気抵抗が小さすぎる場合にはフィルターとしての性能が不十分となり、通気抵抗が大きすぎる場合にはエレクトレットフィルターとしての利点が失われる。 When the electret of the present invention is used as a filter, the ventilation resistance at a wind speed of 10 cm/s is preferably in the range of 0.05 to 50 mmAq, more preferably 0.2 to 30 mmAq, and most preferably 0.5 to 50 mmAq. It is 20mmAq. If the ventilation resistance is too small, the performance as a filter will be insufficient, and if the ventilation resistance is too large, the advantages as an electret filter will be lost.
　上記における濾材品質係数（ＱＦ）の値は、エレクトレット化されていない繊維状物を用いた場合には概ね０．１以下であり、フィルター用途としては０．５以上が好ましくより好ましくは１．０以上であり、更に好ましくは１．１以上であり、最も好ましくは１．２以上である。水を用いた液体接触によるエレクトレット化法の場合においては、加熱乾燥工程を通過させる場合があり、またフィルター用途においてはプリーツ工程や長期保管が行われる場合がある。したがって、上記の濾材品質係数（ＱＦ）は、エレクトレット化直後のみならず加熱処理後に維持してなることが好ましい。 The value of the filter medium quality factor (QF) in the above is generally 0.1 or less when a non-electret fibrous material is used, and for filter use, it is preferably 0.5 or more, and more preferably 1.0. or more, more preferably 1.1 or more, and most preferably 1.2 or more. In the case of the electretization method by liquid contact using water, the material may be passed through a heat drying step, and in filter applications, a pleating step or long-term storage may be performed. Therefore, it is preferable that the above-mentioned filter medium quality factor (QF) is maintained not only immediately after electret formation but also after heat treatment.
　本発明における表面張力、撥液性に対応する指標としては、ＪＩＳ　Ｋ６７６８により用いられるホルムアミド－エチレングリコールモノエチルエーテル混合系からなる表面張力３０から５８ｍＮ／ｍの試験液を用いて浸透性の試験を行うことにより定義される。当該規格には水－メタノール混合系の組成も開示されているが、組成及び結果の連続性を欠くためにホルムアミド系を評価に用いる。なお、本発明者の検討においては水－メタノール混合系の方が見かけの撥液性が高くなる結果を与える。 As an index corresponding to surface tension and liquid repellency in the present invention, a permeability test is performed using a test liquid with a surface tension of 30 to 58 mN/m consisting of a formamide-ethylene glycol monoethyl ether mixed system used according to JIS K6768. Defined by what you do. The standard also discloses the composition of a water-methanol mixed system, but because the composition and results lack continuity, a formamide system is used for evaluation. In addition, the inventor's studies have shown that the water-methanol mixed system has higher apparent liquid repellency.
　なお、本発明において好ましく達成する撥液性としては、１０秒以内の浸透を与える試験液の表面張力として、ＰＰメルトブローンにおける代表値としては無加工状態である３６ｍＮ／ｍ及び、極性物質である含窒素化合物を添加した場合における３７ｍＮ／ｍを超える状態よりも撥液性が高められていることが好ましい。具体的には、３６ｍＮ／ｍ以下が好ましく、より好ましくは３５ｍＮ／ｍ以下、最も好ましくは３４ｍＮ／ｍ以下である。この数値が小さくなることにより、含窒素化合物を含まないポリプロピレンと同等もしくはそれ以上の撥液性を得ることができる。 In addition, the liquid repellency preferably achieved in the present invention is the surface tension of the test liquid that allows penetration within 10 seconds, and the representative value for PP melt blown is 36 mN/m in the unprocessed state and 36 mN/m, which is a polar substance. It is preferable that the liquid repellency is higher than the state of exceeding 37 mN/m when a nitrogen compound is added. Specifically, it is preferably 36 mN/m or less, more preferably 35 mN/m or less, and most preferably 34 mN/m or less. By reducing this value, it is possible to obtain liquid repellency equivalent to or higher than that of polypropylene that does not contain a nitrogen-containing compound.
　かかる撥液性を得ることにより、液体荷電時の乾燥が容易となり生産性及びろ過性能、水を代表とする液体へのバリア性に優れ、オイルミスト負荷時の劣化抑制を実現することが可能となる By obtaining such liquid repellency, drying when liquid is charged becomes easy, and it is possible to achieve excellent productivity, filtration performance, and barrier properties against liquids such as water, and to suppress deterioration when loaded with oil mist. Become
　本発明のエレクトレット及びエレクトレットフィルターは必要に応じて他の構成部材と併用して用いることができる。すなわち、プレフィルター層、繊維保護層、補強部材、機能性繊維層などと組み合わせて用いることができる。プレフィルター層及び繊維保護層としては、例えばスパンボンド不織布、サーマルボンド不織布、発泡ウレタンなどを例示することができる。補強部材としては、例えばサーマルボンド不織布、各種ネットを例示することができる。また、機能性繊維層としては例えば抗菌、抗ウイルス及び識別や意匠を目的とした着色繊維層などを例示することもできる。 The electret and electret filter of the present invention can be used in combination with other constituent members as necessary. That is, it can be used in combination with a pre-filter layer, a fiber protection layer, a reinforcing member, a functional fiber layer, etc. Examples of the pre-filter layer and the fiber protective layer include spunbond nonwoven fabric, thermal bonded nonwoven fabric, and urethane foam. Examples of the reinforcing member include thermal bond nonwoven fabric and various nets. Examples of the functional fiber layer include antibacterial, antiviral, and colored fiber layers for identification and design purposes.
　本発明のエレクトレット及びエレクトレットフィルターは集塵、保護、通気、防汚、防水などの機能により幅広く用いることができる。また別途添加する薬剤による抗菌性、抗カビ性、抗ウイルス性、抗アレルゲン性などの機能を組み合わせて、防塵マスク、各種空調用エレメント、空気清浄機、キャビンフィルター、各種装置の保護を目的としたフィルターとして好適に用いることができる。 The electret and electret filter of the present invention can be widely used due to its functions such as dust collection, protection, ventilation, antifouling, and waterproofing. In addition, by combining functions such as antibacterial, antifungal, antiviral, and antiallergenic properties with separately added chemicals, we have developed products that are designed to protect dust masks, various air conditioning elements, air purifiers, cabin filters, and various other equipment. It can be suitably used as a filter.
　以下、本発明の実施例、比較例について説明するが、本発明は以下の実施例に限定されるものではない。 Examples and comparative examples of the present invention will be described below, but the present invention is not limited to the following examples.
　まず、実施例及び比較例に対して行った性能の評価方法について説明する。
　（粒子透過率・粒子捕集効率）
　７２ｍｍφに打ち抜いたサンプルを有効通気径５０ｍｍφのアダプターに装着し、サンプル厚さ方向に風速１０ｃｍ／ｓにて通風し、光散乱式粒子計数装置リオン社製ＫＣ－０１Ｅを用いて以下の方法にて、粒子透過率、粒子捕集効率を計測した。
　評価粒子：大気塵粒子
　評価風速：１０ｃｍ／ｓ
　評価方法：光散乱法計数法
　効率算出：光散乱計数法による０．３～０．５μｍ間の粒子個数
　粒子透過率[－]＝（試料下流側の粒子個数個数÷試料上流側の粒子個数） First, a method for evaluating the performance of Examples and Comparative Examples will be described.
(Particle transmittance/particle collection efficiency)
A sample punched to 72 mmφ was attached to an adapter with an effective ventilation diameter of 50 mmφ, and ventilation was conducted in the thickness direction of the sample at a speed of 10 cm/s. , particle transmittance, and particle collection efficiency were measured.
Evaluation particles: Atmospheric dust particles Evaluation wind speed: 10cm/s
Evaluation method: Light scattering counting method Efficiency calculation: Number of particles between 0.3 and 0.5 μm by light scattering counting method Particle transmittance [-] = (Number of particles on the downstream side of the sample / Number of particles on the upstream side of the sample)
　（粒子捕集効率[％]＝（１－粒子透過率[－]）×１００
　なお、荷電後の風乾直後に測定した数値を初期捕集効率とした。 (Particle collection efficiency [%] = (1-particle transmittance [-]) x 100
Note that the value measured immediately after air drying after charging was defined as the initial collection efficiency.
　（通気抵抗）
　７２ｍｍφに打ち抜いたサンプルを有効通気径５０ｍｍφアダプターに装着し、微差圧計を接続した内径５０ｍｍの配管を上下に連結、サンプル厚さ方向に風速１０ｃｍ／ｓにて通風し、絞りの無い状態でのサンプル上下の差圧を通気抵抗（圧力損失）として計測した。通気抵抗の単位は、ｍｍＡｑとした。 (ventilation resistance)
A sample punched to 72 mmφ was attached to an adapter with an effective ventilation diameter of 50 mmφ, and piping with an inner diameter of 50 mm connected to a differential pressure gauge was connected above and below, and ventilation was conducted in the thickness direction of the sample at a speed of 10 cm/s without restriction. The pressure difference between the top and bottom of the sample was measured as ventilation resistance (pressure loss). The unit of ventilation resistance was mmAq.
　（濾材品質係数（ＱＦ））
　エレクトレット電荷量及びフィルター性能の指標としては下記で定められる濾材品質係数であるＱＦ値を用いた。
　ＱＦ[ｍｍＡｑ-１]＝－（ｌｎ（粒子透過率[－]）／（通気抵抗[ｍｍＡｑ]）） (Filter media quality factor (QF))
As an index of the electret charge amount and filter performance, the QF value, which is a filter medium quality factor defined below, was used.
QF [mmAq -1 ] = - (ln (particle transmittance [-]) / (ventilation resistance [mmAq]))
　（平均繊維径）
　走査型顕微鏡を用い、画像の視野サイズとして９０μｍ×９０μｍとなるように複数の画像取得を行った後、同一繊維にて重複しないように５０本の繊維直径を計測した。得られた各々の数値を幾何平均することで平均繊維径とした。 (Average fiber diameter)
Using a scanning microscope, a plurality of images were acquired so that the image field size was 90 μm x 90 μm, and then the diameters of 50 fibers were measured so as not to overlap among the same fibers. The obtained values were geometrically averaged to obtain the average fiber diameter.
　（撥液性・浸透試験）
　ＪＩＳ　Ｋ　６７６８にて用いられるホルムアミド及びグリコールモノエチルエーテルからなるぬれ張力試験液を試料直上１ｃｍより１００μＬを穏やかに滴下し、１０秒後の状況を確認する。液滴同士が接触しないように場所を変えながら浸透／非浸透の差異が発生する試験液の表面張力値を確認する。浸透しない試験液のうち最も表面張力値の小さな値を試料の撥液性を示す値として用いた。 (Liquid repellency/penetration test)
Gently drop 100 μL of a wetting tension test liquid consisting of formamide and glycol monoethyl ether used in JIS K 6768 from 1 cm directly above the sample, and check the situation after 10 seconds. Confirm the surface tension value of the test liquid at which the difference between penetration and non-penetration occurs while changing the location so that the droplets do not come into contact with each other. Among the non-penetrating test liquids, the value with the smallest surface tension value was used as the value indicating the liquid repellency of the sample.
＜実施例１＞
　ポリプロピレンホモポリマーを９０質量部、ポリ－４－メチル－１－ペンテンとして三井化学株式会社製ポリメチルペンテン（銘柄：ＤＸ８２０）を１０質量部、及び含窒素化合物としてＢＡＳＦ社製Ｃｈｉｍａｓｓｏｒｂ（登録商標）９４４を１質量部ブレンダー混合したものを、メルトブローン装置を用い、ノズル温度３３０℃、空気温度３３０℃にて紡糸し目付３０ｇ／ｍ２の繊維シートを得た。繊維径５．３μｍであった。浸透性試験の結果、３３ｍＮ／ｍの試験液は浸透せず、３２ｍＮ／ｍの試験液は浸透したため、撥液性は３３ｍＮ／ｍであった。得られた繊維シートに対して、電気伝導度０．７μＳ／ｃｍ、ｐＨ６．８の水を表層から背面に通過させる接触帯電法により荷電を行った。その後２５℃にて風乾することでエレクトレットシートを得た。得られたエレクトレットシートは、繊維径５．２μｍであり、通気抵抗及び粒子透過率より得られる濾材品質係数ＱＦは１．３８であった。 <Example 1>
90 parts by mass of polypropylene homopolymer, 10 parts by mass of polymethylpentene (brand name: DX820) manufactured by Mitsui Chemicals, Inc. as poly-4-methyl-1-pentene, and Chimassorb (registered trademark) 944 manufactured by BASF as a nitrogen-containing compound. A mixture of 1 part by mass of the above was mixed in a blender and spun using a melt blowing device at a nozzle temperature of 330°C and an air temperature of 330°C to obtain a fiber sheet with a basis weight of 30 g/m 2 . The fiber diameter was 5.3 μm. As a result of the permeability test, the test liquid of 33 mN/m did not penetrate, but the test liquid of 32 mN/m penetrated, so the liquid repellency was 33 mN/m. The obtained fiber sheet was charged by a contact charging method in which water having an electrical conductivity of 0.7 μS/cm and a pH of 6.8 was passed from the surface layer to the back surface. Thereafter, the electret sheet was obtained by air drying at 25°C. The obtained electret sheet had a fiber diameter of 5.2 μm, and a filter medium quality factor QF obtained from ventilation resistance and particle permeability of 1.38.
＜比較例１＞
　含窒素化合物であるＢＡＳＦ社製Ｃｈｉｍａｓｓｏｒｂ（登録商標）９４４を添加しなかった他は実施例１と同様とした。繊維径５．４μｍ、浸透性試験の結果３３ｍＮ／ｍの試験液は浸透せず、３２ｍＮ／ｍの試験液は浸透し、撥液性は３３ｍＮ／ｍであった。エレクトレット化後の濾材品質係数ＱＦは０．３８であった。 <Comparative example 1>
The same procedure as in Example 1 was carried out except that the nitrogen-containing compound Chimassorb (registered trademark) 944 manufactured by BASF was not added. The fiber diameter was 5.4 μm, and as a result of the permeability test, a test liquid of 33 mN/m did not permeate, a test liquid of 32 mN/m permeated, and the liquid repellency was 33 mN/m. The filter medium quality factor QF after electretization was 0.38.
＜比較例２＞
　液体接触法に代えてコロナ放電法を用いて荷電を行った他は比較例１と同様とした。エレクトレット化後の濾材品質係数ＱＦは０．６８であった。 <Comparative example 2>
The procedure was the same as Comparative Example 1 except that charging was performed using a corona discharge method instead of the liquid contact method. The filter medium quality factor QF after electretization was 0.68.
＜比較例３＞
　液体接触法による荷電を行う前にコロナ放電法を用いて荷電を行った他は比較例１と同様とした。液体接触によるエレクトレット化後の濾材品質係数ＱＦは０．９８であった。 <Comparative example 3>
The procedure was the same as in Comparative Example 1 except that charging was performed using a corona discharge method before charging using a liquid contact method. The filter medium quality factor QF after electret formation by liquid contact was 0.98.
＜比較例４＞
　ポリプロピレンホモポリマー１００質量部及び含窒素化合物としてＢＡＳＦ社製Ｃｈｉｍａｓｓｏｒｂ（登録商標）９４４を１質量部とした他は実施例１と同様とした。繊維径４．８μｍ、浸透性試験の結果３８ｍＮ／ｍの試験液は浸透せず、３７ｍＮ／ｍの試験液は浸透したため、撥液性は３８ｍＮ／ｍであった。エレクトレット化後の濾材品質係数ＱＦは１．２５であった。 <Comparative example 4>
The procedure was the same as in Example 1, except that 100 parts by mass of polypropylene homopolymer and 1 part by mass of Chimassorb (registered trademark) 944 manufactured by BASF were used as the nitrogen-containing compound. The fiber diameter was 4.8 μm, and as a result of the permeability test, the test liquid of 38 mN/m did not penetrate, but the test liquid of 37 mN/m penetrated, so the liquid repellency was 38 mN/m. The filter medium quality factor QF after electretization was 1.25.
　実施例１と比較例１～３とを比較することにより、実施例１は、オイルミスト耐性やバリア性の指標としての撥液性は同等かつ、濾材品質係数に優れることがわかる。実施例１と比較例４とを比較することにより、実施例１は、ポリ－４－メチル－１－ペンテンを含有することで、ポリプロピレン単体と同等以上の濾材品質係数を得ながら、撥液性は大幅に優れることがわかる。 By comparing Example 1 and Comparative Examples 1 to 3, it can be seen that Example 1 has the same oil mist resistance and liquid repellency as an indicator of barrier properties, and is superior in filter medium quality factor. By comparing Example 1 and Comparative Example 4, it was found that Example 1, by containing poly-4-methyl-1-pentene, achieved liquid repellency while obtaining a filter material quality factor equivalent to or higher than that of polypropylene alone. is found to be significantly superior.
　本発明のエレクトレット及びエレクトレットフィルターはミスト状物捕集時や接触時における性能低下を抑制し、かつバリア性、捕集特性に優れる。特に防塵衣、防塵マスク、空気清浄機等のフィルター用途として好適に用いることができる。 The electret and electret filter of the present invention suppress performance deterioration when collecting mist-like substances or during contact, and have excellent barrier properties and collection properties. In particular, it can be suitably used as a filter for dust-proof clothing, dust-proof masks, air purifiers, and the like.

Claims (5)

  1. 　ポリ－４－メチル－１－ペンテンと、他種ポリオレフィンと、少なくとも１種のヒンダードアミン化合物と含んで成るエレクトレットであり、
    　液体接触により電荷付与されていることを特徴とするエレクトレット。     An electret comprising poly-4-methyl-1-pentene, other polyolefins, and at least one hindered amine compound,
    An electret characterized by being charged by contact with a liquid.
  2. 　前記他種ポリオレフィンがポリプロピレンであることを特徴とする請求項１に記載のエレクトレット。 The electret according to claim 1, wherein the other polyolefin is polypropylene.
  3. 　請求項１または２のエレクトレットを用いたエレクトレットフィルター。 An electret filter using the electret according to claim 1 or 2.
  4. 　メルトブロー不織布である請求項３に記載のエレクトレットフィルター。 The electret filter according to claim 3, which is a melt-blown nonwoven fabric.
  5. 　ポリ－４－メチル－１－ペンテンと、他種ポリオレフィンと、少なくとも１種のヒンダードアミン化合物と含んで成るシート状物を形成する工程と、
    　前記シート状物に液体接触により電荷付与する工程と、を含むこと特徴とするエレクトレットの製造方法。     forming a sheet-like material comprising poly-4-methyl-1-pentene, other polyolefins, and at least one hindered amine compound;
    A method for producing an electret, comprising the step of imparting an electric charge to the sheet-like material by contact with a liquid.
PCT/JP2023/016690 2022-04-28 2023-04-27 Electret and electret filter WO2023210759A1 (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008538532A (en) * 2005-04-22 2008-10-30 スリーエム イノベイティブ プロパティズ カンパニー Vehicle cabin air filter device
JP2022034381A (en) * 2020-08-18 2022-03-03 東洋紡株式会社 Electret filter

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008538532A (en) * 2005-04-22 2008-10-30 スリーエム イノベイティブ プロパティズ カンパニー Vehicle cabin air filter device
JP2022034381A (en) * 2020-08-18 2022-03-03 東洋紡株式会社 Electret filter

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