JP5846621B2 - Filter material and method for producing the same - Google Patents

Description

  The present invention relates to a filter medium composed of a fiber assembly using an electrospinning method (electrospinning method).

  Conventionally, as filtration media composed of fiber aggregates, synthesis of polyester fibers such as polyethylene terephthalate (PET), polyamide fibers such as nylon, polyolefin fibers such as polyethylene and polypropylene, etc., which are generally produced by melt spinning. Melt blown nonwoven fabrics and wet nonwoven fabrics using fibers are used. However, such non-woven fabrics are usually composed of fibers having a fiber diameter of about 1 to 2 μm, and the ability to capture fine particles is not sufficient. However, there is a problem that clogging is accelerated or fluid passage is hindered.

  In order to solve such a problem, various filter media made of a nonwoven fabric using ultrafine fibers obtained by an electrospinning method have been proposed. For example, Japanese Patent Application Laid-Open No. 2005-218909 discloses an ultrafine fiber assembly layer having an average fiber diameter of 0.01 to 0.5 μm and a fine fiber having an average fiber diameter of 0.5 to 5 μm manufactured by an electrospinning method. A filter medium provided with an aggregate layer and integrated by applying pressure with a calendar is disclosed (Patent Document 1). Japanese Patent Application Laid-Open No. 2007-30175 discloses a filter medium comprising a laminate in which a nonwoven fabric produced by an electrostatic spinning method and a breathable sheet are bonded and integrated with an adhesive (Patent Document 2). ). JP 2009-28617 A discloses a filter nonwoven fabric in which a nanofiber layer obtained by an electrospinning method and a support base material are integrated by partial thermal bonding (Patent Document 3). Further, JP-A-2009-233550 discloses an organic polymer having an average fiber diameter of 10 to 1000 nm that is electrospun using a melt of an organic polymer on a non-nanofiber layer having an average fiber diameter of more than 5 μm. A filter medium for a gas filter in which an aggregate of combined nanofibers is deposited and a nanofiber layer is laminated is disclosed (Patent Document 4).

JP-A-2005-218909 JP 2007-30175 A JP 2009-28617 A JP 2009-233550 A

  However, the filter medium has the following problems. Since the electrospinning methods disclosed in Patent Documents 1 to 4 are ultrafine fibers obtained by a method generally called a solution method, the ultrafine fibers are hardly self-adhered to each other, and other filtration layers (supports) If the layer is not disposed on both sides, practical strength cannot be obtained even as a filter medium. Also, between the ultrafine fiber layer and the other filtration layer (support layer), it is necessary to integrate with pressure by calendering, integration with adhesive, or integration by partial thermal bonding. Tend to be impeded. Patent Document 4 proposes that an ultrafine fiber layer is obtained using a melt electrospinning method, and that nanofibers in a semi-dry state are finely agglomerated and non-nanofiber layers are agglomerated. However, since the ultrafine fiber obtained is a single component, it cannot be said that self-adhesion between nanofibers and non-nanofiber layers is sufficient, and in order to obtain practical strength as a filtering material, pressure integration with a calendar is required. It was necessary.

  The present invention has been made in view of the above-described problems, and provides a filtering material using ultrafine fibers obtained by an electrospinning method having good fluid permeability, high filtration accuracy, and high practical strength. With the goal.

The filter medium of the present invention includes a fiber assembly including at least two components of polymer, and a collection of ultrafine composite fibers stretched by melt electrospinning, and another filter sheet on at least one surface of the fiber assembly. A filter medium in which materials are laminated, wherein at least one component of the polymer has a volume resistivity of 10 ¹⁵ Ω · cm or less, and one component of the polymer has a temperature lower than that of the other components. The ultrafine composite fiber is self-adhering with the adhesive component, and the fiber assembly and another filter sheet material are bonded with the adhesive component. .

The method for producing a filter medium according to the present invention includes a fiber assembly that includes at least two components of polymer, and in which ultrafine composite fibers stretched by melt electrospinning are accumulated, and at least one surface of the fiber assembly. The filter sheet material is laminated, and at least one component of the polymer has a volume resistivity of 10 ¹⁵ Ω · cm or less, and one component of the polymer is A step of melting a polymer of at least two components that are adhesive components to be bonded at a temperature lower than that of the other components, a step of stretching the molten polymer by an electrospinning method to form an ultrafine composite fiber, Heat treatment at a temperature at which the adhesive component constituting the laminate is adhered, and a step of forming a laminate with the fiber assembly layer by accumulating on the filter sheet material Was carried out, characterized in that it comprises a step of adhering the ultrafine composite fibers and fiber assembly and the other filter sheet material.

  The filter medium of the present invention uses ultra-fine composite fibers stretched by melt electrospinning, and the ultra-fine composite fibers are self-adhering to each other and are also bonded to other filter sheet materials, so that gas and liquid fluid permeability is good. The filtration accuracy is high and the practical strength is high. In addition, since the ultrafine composite fiber is formed by a melt electrospinning method, there is no residue such as an organic solvent as a spinning dope as in the solution method, and it is safe and has a low environmental burden.

It is a schematic explanatory drawing of the electrospinning apparatus of one Embodiment in this invention. It is the schematic of the fiber cross section of the ultrafine composite fiber of one Embodiment of this invention. It is the schematic of the fiber cross section of the ultrafine composite fiber of other one Embodiment of this invention. It is a photograph of the surface of the nonwoven fabric of Example 1 of this invention of the scanning electron microscope (SEM, magnification 5000 times). It is a photograph of the scanning electron microscope (SEM, magnification 1500 times) of the cross section of the nonwoven fabric of Example 1 of this invention.

In the fiber assembly used in the present invention, a voltage is applied between the supply-side electrode and the collection-side electrode, a charge is applied to the molten resin body containing at least two components of the polymer, and it is elongated by electrospinning to form an ultrafine composite. A fiber assembly obtained by collecting and collecting fibers. In general, in melt electrospinning as described above, the resin charged when passing through the supply-side electrode is stretched at high speed toward the collection-side electrode by electric attraction, so that the volume resistivity value is 10 ^15. Those exceeding Ω · cm tend not to be charged, and tend to be difficult electrospinning resins unsuitable for electrospinning. However, in the present invention, it has been found that an ultrafine composite fiber can be obtained by using a resin having a volume resistivity of 10 ¹⁵ Ω · cm or less as at least one polymer component. In particular, even if it is a hardly electrospinning resin having a high volume resistivity, such as a polyolefin-based resin that is preferably used mainly as an adhesive component, an easily electrospinning resin having a volume resistivity of 10 ¹⁵ Ω · cm or less. It has been found that good electrospinning can be obtained by stretching following the resin. This is because when at least two component polymers are heated and melted before and / or between the supply-side electrodes between the electrodes, for example, until the raw material composite fiber has a certain charge or more, it stays in the vicinity of the supply-side electrodes. In the cross section at the tip of the raw composite fiber heated and melted at that time, the cross-sectional shape is instantaneously alloyed, and among the composite polymer components, the volume resistivity value of 10 ¹⁵ Ω · cm or less is easily electrospun. It is presumed that the resin is strongly charged and combined and spun at that momentum.

In the present invention, the component that is the raw material of the ultrafine composite fiber includes at least two polymers, and one of the polymer components has a volume resistivity of 10 ¹⁵ Ω · cm or less (hereinafter also referred to as the first component). ). This is because when the volume resistivity value of the first component is 10 ¹⁵ Ω · cm or less, the molten polymer component is easily charged when passing through the supply-side electrode. Preferably, it is 10 ⁶ to 10 ¹⁴ Ω · cm, more preferably 10 ⁷ to 10 ¹³ Ω · cm.

In addition, even in a polymer having a high volume resistivity such that the volume resistivity exceeds 10 ¹⁵ Ω · cm, a masterbatch kneading (for example, carbon or metal salts) that reduces the volume resistivity in the polymer. Master batches containing fillers such as), corona processing, fluorine processing, electret processing, and other treatment techniques that lower the resistance value of the resin, or oil agents that reduce the volume resistivity (for example, anionic surfactants) , Cationic surfactants, nonionic surfactants, etc.) on the surface of the composite resin, by using a single or a combination of treatment techniques, apparent volume resistivity before electrospinning. By lowering the value, a resin suitable for electrospinning can be obtained. In the case of resin, the volume resistivity is usually measured by ASTM D-257.

  The apparent volume resistivity value is a value obtained by measuring a volume resistivity (ASTM D-257), which is generally measured with a resin, with a sample obtained by treating the resin portion with the above-described treatment technique. That is, the apparent volume specific resistance value indicates not the volume specific resistance value of the resin itself but the volume specific resistance value of the treated resin.

It is preferable that content of the 1st component in the said raw material component is 10 mass% or more. More preferably, it is 30 mass% or more, More preferably, it is 50 mass% or more. If it is this range, an ultrafine composite fiber can be obtained stably. If the content of the first component is 10% by mass or more, a resin having a volume resistivity value of 10 ¹⁵ Ω · cm or less even if a resin having a volume resistivity value exceeding 10 ¹⁵ Ω · cm is added. When the material is electrospun by electrification, it can be simultaneously electrospun and stretched by its influence to form an ultrafine composite fiber. Moreover, since either a 1st component or another component is used as an adhesion | attachment component, it is preferable that content of a 1st component is 90 mass% or less.

Even when the raw material component is blended with a resin having a volume resistivity of more than 10 ¹⁵ Ω · cm, such as polyolefin (for example, polypropylene, polyethylene) or the like, a resin having a resistance of 10 ¹⁵ Ω · cm or less. If 10 mass% or more is blended, good electrospinning can be performed. Specifically, when a resin having a volume resistivity of 10 ¹⁶ Ω · cm or more such as polyolefin and a resin having a volume resistivity of 10 ¹⁵ Ω · cm or less are used, a preferable volume resistivity is 10 ^15. The content of the resin of Ω · cm or less is 10 to 90% by mass, more preferably 30 to 70% by mass. If the content of the resin having a volume resistivity of 10 ¹⁵ Ω · cm or less is 10% by mass or more, it is easy to make it fine as described above. On the other hand, if it is 90% by mass or less, a stable raw material component is supplied. be able to.

The polymer having a volume resistivity of 10 ¹⁵ Ω · cm or less is not particularly limited, and examples thereof include ethylene vinyl alcohol copolymer (hereinafter also referred to as EVOH), polyesters such as polyethylene terephthalate, nylon, and polyurethane. Among them, EVOH is preferable because it is highly charged and has high extensibility by electrospinning. The volume resistivity value of the EVOH is preferably 10 ⁶ to 10 ¹⁵ Ω · cm, more preferably 10 ⁷ to 10 ⁹ Ω · cm, and still more preferably 10 ^7.5 to 10 ^8.5 Ω · cm.

  The EVOH can be obtained by saponifying an ethylene vinyl acetate copolymer. The content of ethylene in the EVOH is not particularly limited, but is generally 29 to 47 mol (mol)%. Examples of commercially available products include Kuraray's trade name “EVAL”, Nippon Synthetic Chemical Industry's trade name “Soarnol”, and the like, and these commercially available products can be used in the present invention. The melting point of EVOH varies depending on the contents of ethylene and vinyl alcohol contained therein. For example, when 38 mol% of ethylene is contained, the melting point is 171 ° C. In addition, EVOH having a different ethylene content may be appropriately selected and used depending on the combination with other components contained in the raw material components.

The first component may have a volume resistivity value of 10 ¹⁵ Ω · cm or less, and is not particularly limited. However, the melting point is preferably 100 to 300 ° C, and more preferably 120 to 200 ° C.

In the present invention, one polymer component of the polymers is an adhesive component that adheres at a lower temperature than the other polymer components. The polymer component, if functions as an adhesive component may be either a volume resistivity 10 ¹⁵ Ω · cm or less of the polymer component or a volume resistivity of a polymer component of more than 10 ¹⁵ Ω · cm,. The term “adhesive component” as used herein refers to a polymer component that exhibits adhesive performance when heat is applied, and refers to a polymer component that adheres at a lower temperature than other polymer components. The bonding process at this time may be either dry heat or wet heat (including steam).

Examples of the adhesive component include homopolymers or copolymers of polyolefins such as polyethylene, polypropylene, and polybutene, polyesters such as copolyester, polylactic acid, and polybutylene succinate or copolymers thereof. In particular, polyolefins such as polyethylene, polypropylene, and polybutene are polymer components having a volume resistivity exceeding 10 ¹⁵ Ω · cm, but as described above, combined with a polymer component having a volume resistivity of 10 ¹⁵ Ω · cm or less. Thus, it functions as an adhesive component for ultrafine composite fibers. Among these, linear low density polyethylene, low density polyethylene, high density polyethylene, ethylene-propylene copolymer, and polypropylene are preferable.

  The adhesive component preferably has a bonding temperature of 60 ° C. or higher and lower than the melting point of the first component. More preferably, the bonding temperature is 80 ° C. or higher and the melting point of the first component is −10 ° C. or lower. When the bonding temperature is within the above range, the ultra-fine composite fibers described later are sufficiently self-bonded and can be bonded well to other filter sheet materials.

  Further, as the adhesive component, it is preferable to use a polymer component having a melting point lower by 10 ° C. or more than the first component. With this configuration, the first component does not form a film while maintaining the fiber shape, and the ultrafine composite fibers can be self-adhered to each other by the adhesive component, and the peel strength from other filter sheet materials and the tensile strength Thus, a filter medium having an appropriate practical strength such as can be obtained.

  The raw material component may be in a molten state when it is charged. Although the state at the time of supply of a raw material component is not specifically limited, It is preferable that it is a solid state or a molten state. When the raw material components are supplied in a solid state, an ultrafine composite fiber containing at least two polymers can be easily obtained. Further, when the raw material component is supplied in a molten state, the raw material component is easily charged, and an ultrafine composite fiber containing at least two polymers can be easily obtained. In order to stably perform the melt electrospinning, the raw material component is more preferably in a fiber state. As used herein, the fiber state includes not only solid state fibers or filaments but also melted fibers or filaments. When the raw material component is in a fiber state, the cross-sectional shape of the ultrafine composite fiber tends to be similar to the cross-sectional shape of the supplied fibrous raw material component, and the cross-sectional shape of the ultrafine composite fiber obtained by electrospinning is controlled. Cheap. In addition, when self-adhering ultrafine composite fibers described later, from the viewpoint of easily obtaining a sea-island type and / or a core-sheath type composite fiber as the ultrafine composite fiber, the raw material component is a sea-island type and / or as viewed from the fiber cross section. A core-sheath type composite fiber is more preferable.

  The fibrous raw material component (hereinafter also referred to as raw material composite fiber) is preferably a monofilament, a multifilament in which a plurality of monofilaments are converged, or a tow. A multifilament refers to one having 2 to 100 filaments. Tow means that the number of filaments exceeds 100. Among these, from the viewpoint of electrospinning properties, a multifilament or tow in which 10 to 1000 monofilaments are converged is preferable. As another means, a melt spinning machine may be directly connected in front of the electrospinning apparatus, a melted filament may be supplied, and an electric charge may be applied for spinning.

  Examples of the cross-sectional shape of the raw composite fiber include a composite cross-section such as a mixed type (including alloy), a core-sheath type, a parallel type, a split type, and a sea-island type. It may be. In particular, in order to effectively bond the ultrafine composite fiber obtained from the adhesive component, it is preferable that the adhesive component in the raw composite fiber is exposed at least 10% on the fiber surface. More preferably, 30% or more of the adhesive component is exposed on the fiber surface, and still more preferably 80% or more is exposed on the fiber surface. Specifically, the sea-island type and / or the core-sheath type are more preferable as viewed from the fiber cross section. It is preferable that the first component is an island component and / or a core component, and the adhesive component is a sea component and / or a sheath component. In particular, when the island-type (first component) is dispersed in the sea-island type, the cross-sectional shape is instantaneous in the tip cross-section of the raw fiber when heating and melting before and / or between the supply-side electrodes. It is presumed that the composite resin component containing the sea component is well electrospun following the first polymer component in the composite polymer component, which is easily charged. From the viewpoint of remarkably obtaining this effect, the number of segments of the island component per sea-island type raw composite fiber is more preferably 15 to 70 in the sea-island type raw composite fiber.

  The raw material components are heated and melted before and / or between the supply-side electrodes between the electrodes, and are elongated by electrospinning to become ultrafine composite fibers. The ultrafine composite fiber preferably includes a fiber having an adhesive component exposed at least 10% on the fiber surface. More preferably, the adhesive component includes fibers exposed on the fiber surface by 30% or more, and still more preferably includes fibers exposed on the fiber surface by 80% or more. The fiber assembly preferably contains 10% by mass or more of the ultrafine composite fiber in which the adhesive component is exposed at least 10% on the fiber surface. More preferably, the ultrafine composite fiber is contained in an amount of 30% by mass or more, and more preferably 50% by mass or more. Specifically, it is more preferable to include a sea-island type and / or a core-sheath type composite fiber as viewed from the fiber cross section of the ultrafine composite fiber. In the process of extending the raw composite fiber by electrospinning, the ultra-fine composite fiber is a sea component (sheath component) and an island component (core) in the case of a raw composite fiber having an alloy shape or a sea-island type and / or a core-sheath type. In some cases, the shape of the component is reversed. Even in this case, the ultrafine composite fiber preferably contains 10% by mass or more of the sea-island type and / or the core-sheath type composite fiber as viewed from the fiber cross section. More preferably, the ultrafine composite fiber contains 50% by mass or more of sea-island type and / or core-sheath type composite fiber, and still more preferably, the ultrafine composite fiber consists of 100% by mass of sea-island type and / or core-sheath type composite fiber. Moreover, the sea-island type and / or the core-sheath type composite fiber included in the ultrafine composite fiber may have an irregular shape such as a polygon, an ellipse, and an indefinite shape. Furthermore, when the raw composite fiber is a multifilament or tow, it may be an ultrafine fiber having a cross-sectional shape such that the multifilament or tow becomes one fiber. The sea-island type and / or core-sheath type composite fiber referred to in the present invention includes such an ultrafine fiber having a cross-sectional shape. For example, when a tow obtained by bundling 600 core-sheath type composite fibers is used as the raw material composite fiber, a sea-island type composite fiber with an apparent number of island component segments of 600 may be obtained. The first component is an island component and / or a core component, and the second component is a sea component and / or a sheath component. The content of the island component and / or the core component in the ultrafine composite fiber is 10% by mass or more, preferably 30% by mass or more, and more preferably 50% by mass or more. In the ultrafine composite fiber, the melting point of the sea component and / or the sheath component is preferably 10 ° C. or more lower than the melting point of the island component and / or the core component, and the ultrafine composite fibers are easily thermally bonded to each other in the subsequent heat treatment. it can. FIG. 2 shows a schematic cross-sectional view of a sea-island type composite fiber, and FIG. 3 shows a schematic cross-sectional view of a core-sheath type composite fiber.

  When the fiber assembly is heat-treated, if it is heat-treated at a temperature lower than the melting point of the first component (for example, the island component and / or the core component), only the adhesive component (for example, the sea component and / or the sheath component) is bonded. The first component (island component and / or core component) can maintain the fiber shape and does not form a film. Moreover, the fiber assembly of this invention has few heat shrinks compared with a general nonwoven fabric. From the viewpoint of obtaining these effects more remarkably, it is more preferable to use a polymer component whose melting point is 20 ° C. or lower than that of the first component.

The basis weight of the fiber aggregate is preferably 0.1 to 100 g / m ² . More preferably 1 to 50 g / m ^2. If the basis weight is 0.1 g / m ² or more, the practical strength of the fiber assembly can be maintained. On the other hand, if the basis weight is 100 g / m ² or less, a filtration layer having a high collection efficiency can be obtained while keeping air permeability or water permeability appropriately.

  The thickness of the fiber aggregate is preferably 0.1 to 100 μm. More preferably, it is 1-50 micrometers. When the thickness is 0.1 μm or more, the practical strength of the fiber assembly can be maintained. When the thickness is 100 μm or less, it is possible to obtain a filtration layer that maintains air permeability or water permeability appropriately and has high collection efficiency. Here, the thickness of a nonwoven fabric means what was measured according to JISB7502.

  The other filter sheet material is not particularly limited as long as it has a filtration function. For example, a thermal bond nonwoven fabric, a hydroentangled nonwoven fabric, a needle punched nonwoven fabric, a wet nonwoven fabric, a melt blown nonwoven fabric, a spun band nonwoven fabric, a membrane film, a mesh and the like can be mentioned. In particular, when the fiber aggregate containing the ultrafine composite fiber of the present invention is used as the main filtration layer, it is preferable to use a sheet material having a larger air permeability or water permeability than the fiber aggregate. For example, a nonwoven fabric having an average fiber diameter of 0.5 to 100 μm is preferable because it functions as a prefiltration layer. The nonwoven fabric is also preferable because it functions as a reinforcing layer for the fiber assembly. Specifically, a nonwoven fabric having an average fiber diameter of 1 to 50 μm and a tensile strength of 10 N / 5 cm or more, for example, a wet nonwoven fabric is more preferable. The tensile strength was measured according to JIS L 1096 8.12.1 (strip method) 2006. Moreover, the average fiber diameter was obtained by enlarging the sheet cross section with an electron microscope or the like, measuring the fiber diameters of 30 fibers, and calculating the average.

The basis weight of the other filter sheet material is not particularly limited, but is preferably ¹ to 1000 g / m ² . More preferably, it is 5-500 g / m < ² >. When it is within the above range, it can function as a prefiltration layer and / or a reinforcing layer. The basis weight means that measured according to JIS L 1906 (2000).

  Next, the manufacturing method of the molten electrospinning of this invention is demonstrated. FIG. 1 is a schematic explanatory diagram of an electrospinning apparatus according to an embodiment of the present invention. The electrospinning device 11 applies a voltage from the voltage generator 3 between the supply-side electrode 1 and the collection-side electrode 2, and a laser beam along the arrow A from the laser irradiation device 4 immediately below the supply-side electrode 1. Irradiate. The raw composite fiber 7 is drawn from the fiber deposit 6 put in the container 5, passes through the guides 8 and 9, and is supplied from the supply roller 10 to the electrospinning device 11. The raw composite fiber may be supplied from a bobbin wound on a bobbin. The raw composite fiber 7 is charged when passing through the supply side electrode. In this charged state, the raw material composite fiber 7 is heated and melted by being irradiated with a laser beam along the arrow A from the laser irradiation device 4 immediately below the supply side electrode 1, and is expanded to the collection side electrode together with the electric attractive force. The At this time, the raw composite fiber 7 extends in the direction of the arrow B to become ultrafine, and becomes an ultrafine composite fiber. Reference numeral 12 denotes a fiber assembly in which ultrafine composite fibers are accumulated.

  First, a voltage is applied between the supply-side electrode and the collection-side electrode between the electrodes. A preferable applied voltage is 20 to 100 kV, and more preferably 30 to 50 kV. If the voltage is 20 kV or more, the resistance between the electrodes is small in the space (between the electrodes) in the atmosphere, the flow of electrons is good, and the resin is easily charged. Moreover, if it is 100 kV or less, a spark does not occur between electrodes and there is no possibility of igniting resin.

  The distance between the electrodes is preferably 2 to 25 cm, more preferably 5 to 20 cm. If the distance between the electrodes is 2 cm or more, no spark occurs between the electrodes, and there is no possibility of igniting the resin. Moreover, if it is 25 cm or less, the resistance between electrodes is not high, the flow of electrons is not deteriorated, and the resin is easily charged.

  When supplying to a supply side electrode, you may supply a raw material component in a solid state or a molten state. For example, it is supplied in a fiber state (raw material composite fiber). When the raw material component is solid, for example, it may be supplied using a guide roll. On the other hand, when passing through the supply-side electrode, it may be heated to be a plurality of raw material polymer components that are molten or semi-molten (softened). Further, when the raw material component is in a molten state, it can be supplied, for example, by its own weight, pressing from the upstream side of supply, or injection of high-pressure airflow. In particular, from the viewpoint of easily adjusting the degree of melting, it is preferable to provide a melt spinning machine in front of the electrospinning apparatus and supply a composite resin molded product in a molten state by pressing the resin extruded from the melt spinning machine.

  The raw material component (for example, raw material composite fiber) immediately after passing through the supply-side electrode may be irradiated with, for example, a laser beam or near infrared ray, and heated and melted so that the raw material component has a viscosity that facilitates electrospinning. Here, the raw composite fiber is preferably a sea-island type and / or a core-sheath type composite fiber as viewed from the fiber cross section. Even when the raw material component is supplied in a molten state, or when the solid raw material component is supplied and the raw material component is previously melted or semi-molten, the raw material component is reduced by heating and melting between the electrodes. Viscosity can be achieved and extensibility can be increased. As the heating and melting method, spot heating is preferable because the viscosity of the raw material components is instantaneously reduced. Specifically, near-infrared point condensing type spot heating or laser beam irradiation is more preferable. For the near-infrared spot condensing type spot heating, a method described in JP-A-2007-32246 may be used.

The case of irradiating with a laser beam will be described as an example of the heating and melting method. The laser beam includes a laser beam generated from a light source such as a YAG laser, a carbon dioxide (CO ₂ ) laser, an argon laser, an excimer laser, or a helium-cadmium laser. Of these laser beams, a laser beam using a carbon dioxide laser is preferable because of its high power efficiency and high meltability of the composite fiber. The wavelength of the laser beam is, for example, 200 nm to 20 μm, preferably 500 nm to 18 μm, more preferably 1 to 16 μm, and even more preferably 5 to 15 μm. The method of irradiating the laser beam is not particularly limited. For example, a method of irradiating a spot laser beam or a method of irradiating the laser beam on a reflecting plate and controlling the reflecting plate to irradiate linearly or planarly. A method is mentioned. Among these, a method of irradiating the raw composite fiber with a laser beam in a spot shape is preferable because it can be irradiated locally. The size of the beam diameter for irradiating the raw composite fiber with the spot laser beam can be selected according to the shape of the raw composite fiber. For example, in the case of linear resin (for example, monofilament, multifilament, tow, etc.), the specific beam diameter may be larger than the average diameter of the linear resin, for example, 0.5 to 30 mm. The thickness is preferably 1 to 20 mm, more preferably 2 to 15 mm, still more preferably about 3 to 10 mm. The ratio between the average diameter of the linear resin and the beam diameter may be about 1 to 100 times the average diameter of the linear resin, preferably 2 to 50 times, more preferably The beam diameter is about 3 to 30 times, more preferably about 5 to 20 times.

  When the raw material component is heated and melted (for example, irradiated with a laser beam) after passing through the supply side electrode, the end portion of the supply side electrode on the side where the raw material component exits, and spot heating on the raw material component (irradiation with the laser beam) The distance between the parts is preferably 1 to 6 mm. More preferably, it is 2-4 mm. If the distance is 1 mm or more, for example, the laser beam irradiation part is not too close to the electrode, the temperature of the electrode does not increase, and resin decomposition may not occur. On the other hand, if the thickness is 6 mm or less, the charge amount of the raw material component charged when passing through the supply side electrode does not attenuate, and if it is spot-heated, the molten resin tends to easily extend toward the collection side electrode.

  The output of the laser beam necessary for melting the raw material component to an extent that can be extended is equal to or higher than the melting point of the first component constituting the raw material component, and the temperature at which any resin constituting the raw material component does not ignite or decompose What is necessary is just to control to the range which becomes. That is, the raw material component only needs to be in a viscous state. The temperature at which the raw material component is heated to have viscosity is appropriately set depending on the supply speed of the raw material component, the output of the laser beam, the distance between the laser and the raw material component, and the thickness of the raw material component. For example, the heating temperature in the case of a laser beam is preferably 160 to 1200 ° C, more preferably 600 to 800 ° C. If the heating temperature is 160 ° C. or higher, the amount of heat to be heated is sufficient, so that the melting is good, the viscosity is easily obtained, and it is easy to make it ultrafine. Moreover, if it is 1200 degrees C or less, since it is instantaneous heating, resin will not ignite or decompose | disassemble and the fiberization of resin will become favorable. Further, the specific output of the laser beam can be appropriately selected according to the physical property value (melting point), shape, thickness, supply speed, etc. of the raw material component to be used, but it is preferably 3 to 100 mA, for example. Is about 3 to 50 mA, and more preferably about 6 to 40 mA. If the output of the laser beam is less than 3 mA, the irradiation condition of the laser beam for bringing the resin into a molten state may be controlled based on the melting point of the raw material component, but the raw material component is a linear body having a small diameter. In the case where a high voltage is applied, it is preferable to control by the output of the laser beam from the viewpoint of simplicity. You may irradiate a laser beam from one place or multiple places from the circumference | surroundings of a raw material component.

  The raw material component melted to such an extent that it can be stretched is stretched to the collecting side electrode together with the electric attractive force, and becomes an ultrafine composite fiber. The expansion ratio at this time is 100 to 1000 times, preferably 200 to 800 times, and more preferably about 300 to 500 times. By being stretched at this stretch ratio, ultrafine fibers are obtained.

  The fiber diameter of the ultrafine composite fiber of the present invention is preferably 0.1 to 10 μm. More preferably, it is 0.3-5 micrometers, More preferably, it is 0.5-3 micrometers, Most preferably, it is 0.8-1.5 micrometers. Here, the fiber diameter is obtained from the diameter of the fiber in the case of a circular fiber. The fiber diameter (diameter) is measured from the fiber cross section or from the fiber side surface. In addition, in irregular cross-section fibers such as polygons, ellipses, hollows, C-types, Y-types, X-types, and irregular shapes, the fiber diameter is determined by measuring the diameter assuming that the fiber cross-sectional shape is a circle having the same area. Ask. Therefore, in the case of a modified cross-section fiber, the fiber diameter cannot be obtained from the fiber side surface.

  The ultrafine composite fiber is accumulated on the collection side electrode to obtain a fiber aggregate. The fiber aggregate may be collected directly on the collection side electrode, or the collection side electrode has a conveyor shape, and the continuous accumulation position is moved to move the sheet-like fiber. You may enable it to produce an aggregate continuously. Further, as another method for collecting fiber aggregates, by placing a metal mesh, woven fabric, non-woven fabric, paper, etc. on the collection side electrode, and by accumulating ultra-fine composite fibers on the sheet-like material, A fiber assembly having a laminated structure can be obtained. In the present invention, when another filtration sheet material is arranged on the collection side electrode and the ultrafine composite fibers are accumulated on the sheet material, the ultrafine composite fibers enter the voids of the other filtration sheet materials. Practical strengths such as peel strength are increased when the adhesion treatment described below is performed, which is more preferable.

  The objects to be accumulated are preferably grounded to eliminate the potential difference from the collection side electrode. However, if there is no particular problem in production, there is no need to take a separate ground, and the object may be held in a state of being slightly lifted from the collection side electrode.

  Although the obtained fiber aggregate is in a state in which the ultrafine composite fibers are lightly bonded due to the residual heat when accumulated, practical strength is not obtained. Therefore, it is advisable to apply an adhesion treatment to the fiber assembly to self-adhere the ultrafine composite fibers. You may perform an adhesion | attachment process after laminating | stacking a fiber assembly alone or a fiber assembly and another filter sheet material. After laminating the fiber aggregate and other filtration sheet material, and applying an adhesion treatment, the fine composite fibers can be self-adhered to each other, and the interlayer between the fiber aggregate and the other filtration sheet material can be favorably adhered, More preferred.

  In the present invention, as long as another filter sheet material is laminated on at least one surface of the fiber assembly, for example, another filter sheet material may be laminated on both surfaces of the fiber assembly, and another sheet is laminated. May be.

  The adhesion treatment method is not particularly limited, and examples thereof include a drying method using an air-through dryer, a cylinder dryer, a hot roll (including an embossing roll), and the like. It is preferable to use an air-through dryer or a cylinder dryer.

  The bonding treatment may be performed at a temperature at which the bonding component constituting the ultrafine composite fiber is bonded. The adhesion treatment temperature is preferably set to a temperature equal to or higher than the adhesion temperature of the adhesive component and lower than the melting point of the first component. More preferably, the bonding treatment temperature is the bonding temperature (melting point) of the bonding component + 1 ° C. or higher and the melting point of the first component is −5 ° C. or lower. When the bonding treatment temperature is within the above range, the ultrafine composite fibers are sufficiently self-bonded and can be bonded well to other filter sheet materials. The fiber aggregate is preferably formed into a sheet by heat-adhering ultrafine composite fibers by thermal fusion of a sheath component and / or a sea component. For example, the sheath component and / or the sea component are heat-sealed by heat treatment at a temperature below the melting point of the island component and / or the core component, and the ultrafine composite fibers are self-adhering to each other, which is good with other filter sheet materials. A filter medium adhered to the substrate can be obtained. When the adhesive component is high-density polyethylene, the adhesion treatment temperature is preferably 120 to 150 ° C, and when the adhesive component is an ethylene-propylene copolymer, the adhesion treatment temperature is preferably 110 to 140 ° C.

  The air permeability of the filter medium obtained in this manner is appropriately set according to the required filtration performance, but is preferably 0.1 to 100 ccs. More preferably, it is 0.5-20 ccs. If the air permeability is in the above range, it can be suitably used in fields requiring air permeability, for example, air filters, masks and the like. The air permeability of the nonwoven fabric refers to that measured according to JIS L 1096 (Fragile method).

  The average pore size and the maximum pore size of the filter medium of the present invention are appropriately set according to the required filtration performance. The average pore diameter is preferably 10 μm or less, more preferably 5 μm or less. When the average pore diameter is 10 μm or less, it can be suitably used for filters, masks and the like. Moreover, it is preferable that the maximum hole diameter of the said micropore is 15 micrometers or less, More preferably, it is 10 micrometers or less. The average flow diameter (mean flow pore diameter) and the maximum pore diameter (bubble point pore diameter) are those measured by the bubble point method according to ASTM F31686. In the present invention, the average pore diameter and the maximum pore diameter can be further reduced without excessively forming a film by adhering with the adhesive component of the ultrafine composite fiber constituting the fiber assembly.

  The peel strength between the fiber aggregate and the other filter sheet in the filter medium of the present invention is preferably 0.01 N or more. More preferably, it is 0.03N or more, and still more preferably 0.08N or more. When the peel strength is 0.01 N or more, the practical strength when used as a filter medium is satisfied. Peel strength is determined by peeling the fiber assembly from other filter sheet material to 75 mm, then setting it to a tensile tester so that the grip width on one side is 25 mm, pulling speed from 30 mm / min, and gripping interval from 100 mm Pull to 130 mm to obtain a stress-strain curve. Next, in the obtained stress-strain curve, three points were selected from the largest point of the tensile strength, and three points were selected from the smallest point of the minimum, and the average value of the tensile strengths at these six points was taken as the peel strength.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited to the following Example.

The measuring methods used in Examples and Comparative Examples are as follows.
<Fiber diameter>
Using a scanning electron microscope (SEM, trade name “S-3500N” manufactured by Hitachi, Ltd., magnification of 1500 times), the fiber side surface was observed, and an average value was obtained from the measurement results of arbitrary 30 single fibers.

<Tensile strength>
According to JIS L 1096 6.12.1 (strip method), the tensile strength in the length direction of the sheet was measured using a test piece of a sheet having a width of 5 cm and a length of 15 cm.

<Gas collection efficiency>
According to JIS B 9908, air dust is filtered at a measurement speed of 5.3 cm / second by a measurement method in which a non-woven fabric test piece is attached instead of a filter unit and the filtration surface is 100 mmφ, and before and after filtration. Particles of ˜2.0 μm were fractionated, the number of particles was measured, and the collection efficiency was calculated according to the following formula. In addition, the average value of 3 samples was used.
Gas collection efficiency (%) = (1-C2 / C1) × 100
In the above formula, C1 is the number of particles before filtration, and C2 is the number of particles after filtration.

<Gas pressure loss>
The upstream pressure and the downstream pressure of the nonwoven fabric test piece mounted instead of the filter unit at the time of the collection efficiency measurement were measured, and the difference between the upstream pressure and the downstream pressure was taken as the pressure loss.

<Air permeability>
Measurement was performed according to JIS P 8117. A B-type Gurley Densometer (manufactured by Toyo Seiki Co., Ltd.) was used as a measuring device. A non-woven fabric test piece is clamped in a circular hole having a diameter of 28.6 mm and an area of 645 mm ² . With the inner cylinder weight of 567 g, the air in the cylinder is allowed to pass out of the cylinder from the test circular hole. The time required for 100 cc of air to pass through was measured and used as the air permeability (Gurley value).

<Liquid collection efficiency>
Dust for testing Dust mixed with the same amount of JIS 11 and JIS 8 is poured into water, and 1 liter of suspension adjusted to a concentration of 50 ppm is suction filtered through a filter medium with an area of 9.2 cm ² and filtered. The subsequent suspension was dried and the contained dust weight (A) was measured. From this and the dust weight (B) in the suspension before filtration, it was calculated by the following equation.
Filtration efficiency (%) = [(B−A) / B] × 100

<Liquid filtration accuracy>
In the same manner as the measurement of the filtration efficiency, the suspension is suction filtered, and the number of particles (N) by the particle size in the suspension after filtration is measured using a particle size distribution meter (trade name Coulter Counter ZM type). And measured. Similarly, the number of particles (M) for each particle size in the suspension before filtration is measured, and the blocking rate for each particle size is calculated from the formula [(MN) ÷] × 100. The particle diameter at which the rate was 80% was defined as filtration accuracy (μm).

<Liquid filtration flow rate>
In the same manner as the measurement of the filtration accuracy, 1 liter of the suspension was filtered by suction, and the time required for the entire amount of the suspension to pass through the filter medium from the start of filtration was measured. The flow rate per hour was calculated.

<Raw resin>
(1) Polypropylene (PP): “SA03” manufactured by Nippon Polypro Co., Ltd., melting point 161 ° C., melt flow rate measured according to JIS-K-7210 (MFR; measuring temperature 230 ° C., load 21.18 N (2.16 kgf) ) 30g / 10min
(2) High density polyethylene (PE): “HE490” manufactured by Nippon Polyethylene Co., Ltd., melting point 130 ° C., melt flow rate measured according to JIS-K-7210 (MFR; measurement temperature 190 ° C., load 21.18 N (2. 16kgf)) 20g / 10min
(3) Ethylene-vinyl alcohol copolymer (EVOH): “K3835BN” manufactured by Nippon Synthetic Chemical Co., Ltd., melting point 171 ° C., measured according to JIS-K-7210 (MFR; measurement temperature 230 ° C., load 21.18 N) (2.16 kgf)) 35 g / 10 min
(4) Ethylene-propylene copolymer (EP): “WXK1183” manufactured by Nippon Polypro Co., Ltd., melting point 128 ° C., melt flow rate measured according to JIS-K-7210 (MFR; measuring temperature 230 ° C., load 21.18 N (2 .16 kgf)) 25 g / 10 min
(5) Polyvinyl alcohol (PVA): A 10% by mass aqueous solution of “JP-18S” manufactured by Nippon Vinegar Poval Co., Ltd. was used.

<Other filter sheet materials>
As another filter sheet material, fiber length is 5mm, fineness is 0.9dtex, core component is polypropylene, sheath component is a core-sheath type composite fiber ("NBF (H)" manufactured by Daiwabo Polytech Co., Ltd.) 100% A wet papermaking nonwoven fabric having a basis weight of 10 g / m ² and a thickness of 50 μm was prepared. The tensile strength in the machine direction of this wet papermaking nonwoven fabric was 20.2 N / 5 cm.

<Manufacture of raw composite fibers>
The raw material component was melt-spun according to a conventional method to obtain an undrawn yarn to obtain a raw composite fiber.

<Electrospinning method>
The electrospinning apparatus used the apparatus shown in FIG. 1, and the conditions were as follows.
Voltage between electrodes: 32.5 kV
Distance between electrodes: 10cm
Spinning speed: 30mm / min
Atmospheric temperature: 23 ° C
Laser device: PIN-30R manufactured by Onizuka Glass Co., Ltd. (rated output 30 W, wavelength 10.6 μm, beam diameter 6 mm)
Distance between supply side electrode and laser irradiation part: 4mm
Supply-side electrode: UNI series 20G × 15 manufactured by Unicontrols Co., Ltd. Laser intensity: 20 mA.

(Production Examples 1 to 3)
Island component, sea component, blending ratio, cross-sectional structure, single fiber diameter of one fiber, total number of fibers, and spinning discharge amount of raw composite fibers used for production of ultrafine composite fibers of Production Examples 1 to 3 Is shown in Table 1 below. Using the raw composite fibers shown in Table 1, ultrafine composite fibers of Production Examples 1 to 3 were obtained under the above spinning conditions. In addition, the ultrafine composite fibers of Production Examples 1 to 3 included a cross-sectional shape similar to the fiber cross-sectional shape of the raw composite fibers.

(Production Example 4)
<Electrospinning method>
Manufactured by a normal solution electrospinning method using an aqueous solution of 10% by mass of PVA at a voltage of 25 kV between electrodes, a distance between electrodes of 8 cm, and an ambient temperature of 23 ° C. with a spinning discharge rate of 0.0051 g / min. did.

Table 1 shows the fiber diameters of the ultrafine composite fibers after spinning in Production Examples 1 to 4. As is clear from Table 1, in the production examples 1 to 3, since the volume specific resistance value of the island component or the sea component in the raw material composite fiber as the raw material component is 10 ¹⁵ Ω · cm or less, good spinning properties are obtained. And an ultrafine composite fiber was obtained. In addition, in the case of Production Example 8 using a liquid raw material resin, ultrafine fibers were obtained by the solution electrospinning method.

(Example 1)
Using the raw material composite fiber of Production Example 1, another filtration sheet material (wet paper making nonwoven fabric having a basis weight of 10 g / m ² and a thickness of 50 μm) is placed on the collection-side electrode under the above spinning conditions, and melt electrospinning. The raw material laminated sheet adjusted to the fabric weight and thickness of Table 2 was obtained by accumulating on the fiber assembly containing the ultrafine composite fiber of Production Example 1 and other filter sheet materials. A heat-bonded nonwoven fabric (hereinafter referred to as an air-through dryer nonwoven fabric) heat-treated by blowing hot air from the surface of the fiber assembly by an air-through dryer method at 145 ° C. for 30 seconds, or 140 ° C., 30 seconds. By using the cylinder dryer method, heat-bonded nonwoven fabric (hereinafter referred to as “cylinder dryer nonwoven fabric”) was produced by heat treatment so that the fiber aggregate surface became the cylinder surface.

  A photograph of the surface of the air-through dryer nonwoven fabric thus obtained is shown in FIG. 4 using a scanning electron microscope (SEM, magnification 5000 times). Moreover, the photograph of the scanning electron microscope (SEM, magnification 1500 times) of the cross section of an air through dryer nonwoven fabric is shown in FIG.

(Examples 2-3)
The raw material composite fibers of Production Examples 2 to 3 were electrospun and accumulated as they were to obtain a fiber assembly (hereinafter referred to as a nonwoven fabric after spinning). Next, the fiber aggregate is laminated on another filter sheet material (wet paper making nonwoven fabric having a basis weight of 10 g / m ² and a thickness of 50 μm), and hot air is blown from the fiber aggregate surface by an air-through dryer method at 145 ° C. for 30 seconds. An air-through dryer nonwoven fabric heat-treated by spraying or a cylinder dryer nonwoven fabric heat-treated so that the fiber aggregate surface becomes a cylinder surface by a cylinder dryer system at 140 ° C. for 30 seconds. In addition, the filtration performance of the nonwoven fabric after spinning was evaluated by simply superimposing another filtration sheet material on the nonwoven fabric after spinning.

(Comparative Example 1)
The ultrafine fiber nonwoven fabric of Comparative Example 1 was produced by the solution electrospinning method of Production Example 4. Although heat treatment was performed in the same manner as in Examples 2 and 3, the ultrafine fiber nonwoven fabric contracted violently to form a film, and thus a predetermined sample could not be obtained. The filtration performance was evaluated by simply superposing other filtration sheet material on this ultrafine fiber nonwoven fabric.

  Table 2 shows the material properties of the basis weight, thickness, tensile strength (longitudinal direction), average pore diameter, and maximum pore diameter of the nonwoven fabrics of Examples 1 to 3 and Comparative Example 1.

As is apparent from Table 2, the ultrafine composite of Production Examples 1 and 2 including an island component having a volume resistivity value of 10 ¹⁵ Ω · cm or less and a sea component having a volume resistivity value exceeding 10 ¹⁵ Ω · cm. In Examples 1 and 2 using fibers, the tensile strength of the air-through dryer nonwoven fabric and the cylinder dryer nonwoven fabric of any weight and thickness was higher than that of the spun nonwoven fabric after heat treatment. Moreover, in Examples 1-2, the average hole diameter and the maximum hole diameter of the air through dryer nonwoven fabric and cylinder dryer nonwoven fabric of any fabric weight and thickness were small compared with the post-spinning nonwoven fabric which was not heat-processed, and the denseness was improving. In particular, the maximum pore diameter could be reduced to about 1/2 to 1/10 before and after the heat treatment, and the uniformity of the pore diameter was improved.

Further, in Example 3 using the ultrafine composite fiber of Production Example 3 including a sea component having a volume resistivity value of 10 ¹⁵ Ω · cm or less and an island component having a volume resistivity value exceeding 10 ¹⁵ Ω · cm. The tensile strength and puncture strength of the air-through dryer nonwoven fabric and the cylinder dryer nonwoven fabric tended to be higher to some extent than the spun nonwoven fabric that was not heat-treated. This is because some ultrafine composite fibers have a cross section similar to the cross section of the raw composite fibers when the raw composite fibers are melt electrospun, but some of them are exposed on the fiber surface. Estimated. On the other hand, in Comparative Example 1 using the ultrafine fiber of Production Example 4 produced by a solution electrospinning method using a liquid raw material resin, the nonwoven fabric was formed into a film in both the air-through dryer nonwoven fabric and the cylinder dryer nonwoven fabric.

  Next, the results of evaluating the gas filtration performance of the filter media of Examples 1 to 3 and Comparative Example 1 are shown in Table 3.

  It was confirmed that the filtration media of Examples 1 to 3 can adjust the filtration performance by adjusting the basis weight or adjusting the adhesion state. In particular, it was confirmed that the filter media of Examples 1 and 2 were suitable for high-accuracy filtration because of high practical strength and high density. On the other hand, the filter medium of Comparative Example 1 obtained high filtration performance despite its low basis weight, but it was difficult to adjust the filtration performance according to the purpose.

(Production Example 5)
Using the raw composite fiber of Production Example 1 shown in Table 1, other filtration sheet material was placed on the collection-side electrode under the above spinning conditions, and melt electrospinning was performed. The raw material laminated sheet adjusted to the fabric weight and thickness of Table 4 was obtained by accumulating on the fiber assembly containing fibers and other filter sheet materials (Production Examples 5-1, 5-2, 5-3). . The ultrafine composite fiber of Production Example 5 contained a cross-sectional shape similar to the fiber cross-sectional shape of the raw composite fiber. Table 4 shows the material characteristics of the obtained raw material sheet.

  When the heat-bonded sheet was produced by heat-treating the raw material laminated sheets of Production Examples 5-1 to 3 at a temperature of 120 ° C. and 145 ° C. for 30 seconds using a cylinder dryer method, the sheet had good peel strength. It was confirmed that the ultrafine composite fibers were self-adhered to each other, and the interlayer between the fiber aggregate and the other filter sheet material was adhered by the adhesive component (ethylene-propylene copolymer).

Example 4
The following filter media were produced as liquid filters. The raw material sheet of Production Example 5 was heat-treated by a cylinder dryer method at 145 ° C. for 30 seconds to produce a heat-bonded nonwoven fabric.

(Comparative Example 2)
The raw material sheet of Production Example 5 was directly prepared as a filtering material.

(Comparative Example 3)
As a polypropylene melt blown nonwoven fabric, “SYNTEX NANO3” (nominal average fiber diameter 0.6 μm) manufactured by Mitsui Chemicals, Inc. was prepared.

(Comparative Example 4)
Using the PVA spinning stock solution of Production Example 4 adjusted to the basis weight and thickness of Table 1, it was accumulated on another filter sheet material by the solution electrospinning method. Next, the same other filter sheet material was placed on the PVA surface of the obtained laminate, and bonded at 120 ° C. using a hot press machine to obtain a filter material.

  Next, Table 5 shows the results of evaluating the liquid filtration performance of the filter media of Example 4 and Comparative Examples 2 to 4.

  It was confirmed that the filtration media of Examples 4-1 to 3 can adjust the filtration performance by adjusting the basis weight. Moreover, since the practical strength was high and the denseness was high, it was confirmed that it was suitable for high-precision filtration. On the other hand, since the filter medium of Comparative Example 2 was not heat-treated, the layers were easily peeled off and the practical strength was not sufficient. Further, the filtration performance was inferior to that of Example 4. In Comparative Example 3, the filtration performance was equivalent to that of Example 4-2, but the filtration flow rate was small and inferior. Although the filter medium of Comparative Example 4 obtained high filtration performance despite having a low basis weight, it was inferior in terms of low filtration flow rate when compared with the same collection efficiency as Example 4, and the fiber diameter of PVA was also low. Since it is thin, it is necessary to reduce the basis weight, so that the variation in the pore size of the filter medium (maximum pore size) becomes large, and it is difficult to use in applications where absolute accuracy is required.

  The filter medium of the present invention is useful as a filter base material for filter membranes for gas and liquid applications, pleated filters, honeycomb filters, cartridge filters and the like. As liquid filters, it is suitable for filtration of water, beverages, solvents, sewage, hypochlorous acid, paints, etc., and as gas filters, HEPA, ULPA, membrane membrane alternative filters, air conditioning filters, mask filters, etc. Is preferred.

DESCRIPTION OF SYMBOLS 1 Supply side electrode 2 Collection side electrode 3 Voltage generator 4 Laser irradiation apparatus 5 Container 6 Fiber deposit 7 Raw material composite fiber 8,9 Guide 10 Supply roller 11 Electrospinning device 12 Fiber aggregate of ultrafine composite fiber 20 Sea-island type composite Fiber 21 Island component 22 Sea component 30 Core-sheath type composite fiber 31 Core component 32 Sheath component

Claims (3)

A fiber assembly including at least two component polymers, a fiber diameter of 0.1 to 10 μm, and a collection of sea-island- type ultrafine composite fibers as viewed from the fiber cross section;
A filter medium in which another filter sheet material is laminated on at least one surface of the fiber assembly,
ShimaNaru fraction is apparent volume resistivity 10 ¹⁵ Ω · cm or less of the easily electrospinning resin,
And marine fraction is hardly electrospinning resin apparent volume resistivity Ru exceed 10 ¹⁵ Ω · cm,
Is an adhesive component marine content adhered at a temperature lower than the island component,
The ultra-fine composite fibers are self-adhering with the adhesive component,
The said fiber aggregate and other filter sheet material are the filter media which have adhere | attached with the said adhesive component. The marine component melting point is lower 10 ° C. or higher than the melting point of the island Ingredients, filtration media according to claim 1. A fiber assembly including at least two components of polymer, and an island- type ultrafine composite fiber collected from a cross section of the fiber stretched by melt electrospinning, and another filter sheet on at least one surface of the fiber assembly A method for producing a filtering material in which materials are laminated,
Apparent volume resistivity of ShimaNaru content is not more than 10 ¹⁵ Ω · cm, and the apparent volume resistivity of marine content exceeds 10 ¹⁵ Ω · cm,
Step of melting a polymer of at least two components marine content is an adhesive component for bonding at a lower temperature than the other components,
A process in which a melted polymer is stretched by an electrospinning method to form an ultrafine composite fiber;
A step of stacking the ultrafine composite fiber on another filter sheet material to form a laminate with a fiber assembly layer;
And adhesive component adheres constituting the laminate, and subjected to heat treatment at a temperature below the melting point of ShimaNaru component, comprising the step of adhering the ultrafine composite fibers and fiber assembly and the other filter sheet material, filtering material Manufacturing method.