JP2007098370A - Multi-layer filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-layer filter which can be an electrolet even in the case of a thick thickness and a high weight per unit surface area, scarcely causes dropping of fibers during its use, and has little pressure loss even after long time use. <P>SOLUTION: The multi-layer filter contains composite fibers as component fibers each of which comprises two or more kinds of thermoplastic resin components with different melting points of which the thermoplastic resin component having a relatively low melting point occupies a portion of the surface as a heat-adhesive component. A fiber bulk is composed by partially agglomerating and uniting a plurality of the composite fibers. The multi-layer filter is obtained by stacking and uniting a plurality of laminated nonwoven fabrics in a separable manner, wherein each of the laminated nonwoven fabrics consists of a melt blown nonwoven fabric A having projected parts in the surface by the fiber bulk formed in the above-mentioned manner and a nonwoven fabric B stacked and united on one face of the melt blown nonwoven fabric A and containing fibers with a fiber diameter of 15 μm as constituent fibers. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multilayer filter, and more particularly to a multilayer filter that can be suitably used as an air filter material such as a building air-conditioning filter, a dust-absorbing curtain, and a mask material by electret processing.

  Melt blown nonwoven fabrics composed of composite fibers composed of two different components are disclosed in Patent Documents 1 to 4, and specifically, melt blown using composite fibers having two thermoplastic resin components having different melting points. The present invention relates to a technique for manufacturing a nonwoven fabric by the law.

  However, the melt-blown nonwoven fabric obtained by the above-described conventional technology is manufactured by laminating the continuous fibers discharged from the nozzles as uniformly as possible on the conveyor belt, so that the thickness is smooth and paper-like. It was.

  And since such a melt blown nonwoven fabric is thin, there existed a problem that it was hard to catch on the gear roll of a pleat folder, and workability | operativity was bad. Moreover, since the melt blown nonwoven fabric is thin as described above, it is necessary to increase the basis weight in order to improve the collection efficiency of the filter. However, if the basis weight of the melt blown nonwoven fabric is increased, air circulation is increased. There was a problem that the pressure loss worsened and the pressure loss increased.

Furthermore, in the electret nonwoven fabric composed of fibers made of polyolefin resin as all components, the insulation resistance is large, and the basis weight of the nonwoven fabric exceeds 90 g / m ² in order to increase the thickness. There was a problem that the penetrability of the abruptly decreased.

JP-A-5-179511 JP-A-5-214655 JP-A-5-263307 JP 2001-98453 A

  The present invention provides a multilayer filter that can be electretized even if it is thick and has a high basis weight, and that there is little dropout of fibers during use and little pressure loss even during long-term use.

  The multilayer filter F of the present invention has two or more kinds of thermoplastic resin components having different melting points, and among these thermoplastic resin components, a thermoplastic resin component having a relatively low melting point is a surface as a thermal adhesive component. Is formed as a constituent fiber, and a plurality of composite fibers 1, 1... Are partially aggregated and integrated to form a fiber mass 2. A plurality of laminated nonwoven fabrics C comprising a melt blown nonwoven fabric A having convex portions 3 formed on the surface and a nonwoven fabric B laminated and integrated on one surface of the melt blown nonwoven fabric A and containing fibers having a fiber diameter of 15 μm or more as constituent fibers. , It is integrated so as to be peelable.

  Here, the thermoplastic resin component having a relatively low melting point among the two or more types of thermoplastic resin components refers to a thermoplastic resin component having a low melting point in the case of two types of thermoplastic resin components, and three or more types. In the case of the thermoplastic resin component, it means any one of the remaining thermoplastic resin components excluding the thermoplastic resin component having the highest melting point. The melting point of the thermoplastic resin means a peak temperature when a differential scanning calorimetry (DSC) measurement is performed under a temperature rising rate of 10 ° C./min in the plastic transition temperature measurement method specified in JIS K7121. .

  The composite fiber 1 constituting the multilayer filter of the present invention has two or more types of thermoplastic resin components having different melting points, and a thermoplastic resin component having a relatively low melting point among these thermoplastic resin components. Specifically, the thermoplastic adhesive component 11 occupies a part of the surface. Specifically, two types of thermoplastic resin components having different melting points as shown in FIG. a)], a cat-eye type (FIG. 1 (b)) or a three-layer type in which one component is separated into two by the other component (FIG. 1 (c)), The thermoplastic resin component having a low melting point of the two types of thermoplastic resin components is a fiber that occupies most of the surface of the composite fiber as the thermal adhesive component 11.

  Furthermore, the composite fiber 1 has two types of thermoplastic resin components having different melting points, and the other thermoplastic resin component is an island in the thermoplastic resin component having a low melting point among the thermoplastic resin components. It has a multi-core type with a cross-sectional shape dispersed in the form of two types and two types of thermoplastic resin components with different melting points, and is divided radially from the center, and the two types of thermoplastic resin components are arranged alternately. It may be a fiber having a cross-sectional shape. The cross-sectional shape of the composite fiber is basically a circular shape such as a circle or an ellipse, but may be an irregular shape with a rounded corner or a hollow fiber.

  And it does not specifically limit as a thermoplastic resin component which comprises the said composite fiber 1, For example, polyethylene-type resins, such as an ethylene-octene copolymer and a low density polyethylene, homopolypropylene, and a propylene contain 50 mass% or more. Polypropylene resin such as ethylene-propylene copolymer, polyolefin resin such as poly (butene-1); polyester resin such as low melting point ester copolymer and aliphatic polyester resin; polyamide resin; thermoplastic polyimide resin; A thermoplastic elastomer is preferred, polyolefin resin is preferred, and since the crystallization rate is slow, it has excellent heat-fusibility, and the fibers are adhesively adhered when sprayed from a nozzle and laminated at the collector part. When heat fusion and crystallization progress, Ri, because of high thermal adhesiveness between the fibers, poly (butene-1), more preferably polypropylene-based resin, it is preferably used in combination poly (butene-1) and a polypropylene resin. The thermoplastic resin may be a modified resin by polymer alloy, graft polymerization, low temperature plasma treatment or the like, for example, a polyester resin decomposable by microorganisms. Such a degradable polyester resin is commercially available from UCC under the trade name “TONE”.

Further, if the density of poly (butene-1) is low, melt spinning may be difficult because it is soft and increases in viscosity, whereas if it is high, spinnability may be reduced and melt spinning may not be possible. Therefore, 0.905 g / cm ³ or more and less than 0.930 g / cm ³ is preferable. In addition, the density of poly (butene-1) says what was measured based on the float-sink method prescribed | regulated to JISL1015-7.14.1.

  And if the melting point of the thermoplastic resin which occupies a part of the surface of the composite fiber 1 and becomes a heat-adhesive component is low, the composite fiber may be too heat-bonded and difficult to control. Since the combination with other thermoplastic resin components in the composite fiber may be restricted, it is preferably 60 ° C. or higher and lower than 270 ° C.

  On the other hand, if the melting point of poly (butene-1) is low, melt spinning becomes difficult because it is soft and increases in viscosity. On the other hand, if it is high, spinnability may be reduced and melt spinning may not be possible. Therefore, it is preferably higher than 115 ° C and lower than 130 ° C.

  The thermoplastic resin constituting the composite fiber 1 of the melt blown nonwoven fabric A has the same melt flow rate as the melt flow rate of the thermoplastic resin used for the staple fiber in order to have the same stiffness and hardness as the staple fiber. It is preferable to have a rate.

  Specifically, if the melt flow rate of the thermoplastic resin constituting the composite fiber 1 is small, it may be difficult to produce a composite fiber having a thin fiber diameter, whereas if the melt flow rate is large, the melt flow rate of the composite fiber having a large fiber diameter may be difficult. Manufacturing can be difficult. In the case of a thick composite fiber of 10 to 200 μm used for forming the fiber mass 2, 5 to 200 g / 10 min is preferable. When simply forming a thin composite fiber of 0.3 to 20 μm, 50 to 1000 g / 10 min is preferable. In addition, the melt flow rate of a thermoplastic resin means what was measured by the load 2.169Kg based on JISK-6767. However, the measurement temperature is 230 ° C. when the melting point of the thermoplastic resin is 200 ° C. or lower, and 290 ° C. when the melting point of the thermoplastic resin exceeds 200 ° C.

  On the other hand, if the average fiber diameter of the composite fiber 1 is thin, it is difficult to be collected by the collector part and may become a floating fiber. On the other hand, if the fiber is thick, the fibers are fused before reaching the collector part. Therefore, it is preferable to exceed 0.3 μm and less than 200 μm.

  And in the constituent fibers of the melt blown nonwoven fabric A, the thermoplastic resin component having two or more thermoplastic resin components having different melting points and having a relatively low melting point among these thermoplastic resin components is used as the thermal adhesive component. If the content of the composite fiber 1 occupying a part of the surface is small, the heat fusion between the constituent fibers may be insufficient. Therefore, the content is preferably 20% by mass or more, more preferably 30 to 100% by mass. Preferably, 100 mass% is particularly preferable.

  Furthermore, in the melt blown nonwoven fabric A, as shown in FIG. 2, a large number of fiber masses 2 formed by partially aggregating and integrating a plurality of composite fibers 1, 1,. A large number of convex portions 3 are formed on the surface of the melt blown nonwoven fabric A due to the presence of the fiber mass 2.

  Here, the fiber mass 2 is a mass formed by agglomerating and integrating the plurality of composite fibers 1, 1... By partially heat-sealing each other. When the temperature is low, the shape of the composite fiber 1 is partially retained, and the composite fibers 1, 1... Are aggregated and integrated to form a fiber lump 2. Although the composite fibers 1, 1... Are aggregated and integrated with each other in a state where the form of the composite fiber has completely disappeared at the wearing portion, the fiber bundle 2 may be formed in any form.

  Moreover, in the periphery of the fiber lump 2 in the meltblown nonwoven fabric A, the voids are formed larger than other portions in the meltblown nonwoven fabric due to the presence of this fiber lump 2, and the portion where the fiber lump 2 is present is The melt-blown nonwoven fabric A has a large thickness and a low fiber density, and is excellent in fluid permeability. Therefore, the melt-blown nonwoven fabric A can reduce its pressure loss and is bulky.

  And since the melt blown nonwoven fabric A has the structure which formed the space | gap partially by the presence of the fiber lump 2 and reduced the density as mentioned above, it improves the electric field permeability and electret processing It is easy to give.

In addition, if the ratio (thickness / weight) of the thickness (μm) and the basis weight (g / m ² ) in the melt blown nonwoven fabric A is small, the distribution density of the fiber mass is reduced, and the laminated nonwoven fabrics are integrated by thermal bonding. 8 or more is preferable.

  Furthermore, in the above description, the case where the melt blown nonwoven fabric A is a single layer has been described, but a plurality of melt blown nonwoven fabrics A, A, each of which is composed of different types of composite fibers are laminated and integrated. Alternatively, it may be a case where a plurality of melt blown nonwoven fabrics A, A... Composed of composite fibers having different average fiber diameters from each other are laminated and integrated, or a combination thereof. Good.

  A nonwoven fabric B including fibers having a fiber diameter of 15 μm or more as a constituent fiber is laminated and integrated on one surface of the melt blown nonwoven fabric A to form a laminated nonwoven fabric C. The nonwoven fabric B compensates for the insufficient strength of the meltblown nonwoven fabric A and plays a role in improving the hardness and waist strength of the laminated nonwoven fabric C. The meltblown nonwoven fabric A and the nonwoven fabric B are composites constituting the meltblown nonwoven fabric A The fibers 1 are laminated and integrated by the thermal adhesive force of the thermal adhesive component 11 of the fiber 1.

  Such a non-woven fabric B is not particularly limited as long as it has the above-described action, and examples thereof include a spunbond nonwoven fabric, a meltblown nonwoven fabric, a spunlace nonwoven fabric, a heat-bonded nonwoven fabric, a needle punched nonwoven fabric, and a resin-impregnated adhesive nonwoven fabric. When the layer filter is electretized, a spunbonded nonwoven fabric is preferable.

  The thermoplastic resin constituting the constituent fibers of the non-woven fabric B is not particularly limited. For example, ethylene-octene copolymer, polyethylene resin such as low density polyethylene, homopolypropylene, ethylene containing 50% by mass or more of propylene. -Polypropylene resin such as propylene copolymer, polyolefin resin such as poly (butene-1), polyester resin such as low melting point ester copolymer and aliphatic polyester resin, polyamide resin, thermoplastic polyimide resin, polycarbonate resin, A thermoplastic elastomer etc. are mentioned, Polyolefin resin is preferred, and ethylene-propylene copolymer containing 50% by mass or more of homopolypropylene and propylene is more preferred.

  And the nonwoven fabric B contains the fiber whose fiber diameter is 15 micrometers or more as a constituent fiber for the purpose of reduction of the pressure loss of a multilayer filter. The content of the fiber having a fiber diameter of 15 μm or more in the constituent fibers of the non-woven fabric B is preferably 30% by mass or more, and preferably 50 to 100% by mass because the pressure loss of the multilayer filter may increase if it is small. More preferred.

  Furthermore, since there exists a possibility that the surface of the constituent fiber of the nonwoven fabric B may inhibit electretization of the multilayer filter, it is preferable that a hydrophilic chemical substance such as a surfactant is not attached. Examples of such hydrophilic chemical substances include anionic surfactants such as alkylbenzene sulfonates and alkylnaphthalene sulfonates, cationic surfactants such as aliphatic amine salts and aliphatic quaternary ammonium salts, and amino acids. Examples thereof include amphoteric surfactants such as carboxylate and imidazolinium betaine, and nonionic surfactants such as polyoxyethylene alkyl ether and polyoxyethylene alkylphenyl ether.

  In the multilayer filter F of the present invention, a plurality of laminated nonwoven fabrics C having the above-described configuration are laminated and integrated so as to be peelable. As a laminated form of the plurality of laminated nonwoven fabrics C, C..., As shown in FIG. 3, the plurality of laminated nonwoven fabrics C, C. Alternatively, a plurality of laminated nonwoven fabrics C, C... May be laminated in a state where the melt blown nonwoven fabric A and the nonwoven fabric B are irregularly arranged in the thickness direction. As a specific example of the latter form, adjacent laminated nonwoven fabrics C and C are laminated and integrated in such a state that the melt blown nonwoven fabrics A and A are opposed to each other. , C are laminated in a state in which the nonwoven fabrics B and B are opposed to each other (B), and the laminated form (I) and the laminated form (B) are irregularly combined. It may be. The laminated nonwoven fabrics C and C are thermally bonded and integrated so as to be peelable by the heat bonding component 11 of the composite fiber 1 of the melt blown nonwoven fabric A or the heat bonding component of the constituent fibers of the nonwoven fabric B.

  In the multilayer filter F, the multilayer nonwoven fabric C, which is the outermost layer, is the main filter layer M, and the remaining laminated nonwoven fabrics C, C, etc. other than the main filter layer M are sub-filter layers S, respectively. The basis weight of the main filter layer M is configured to be equal to or more than the basis weight of the sub filter layer S, and the multilayer filter F is held by the main filter layer M having a large basis weight. The sub filter layer S having a small basis weight can effectively capture fine particles in the air and improve the electric field permeability while being configured so that it can be easily pleated. The filter F can be easily electretized.

Specifically, if the basis weight of the main filter layer M is small, the waist of the multilayer filter F may be weak and it may be difficult to pleat the multilayer filter F. Since electretization may become difficult, 50-200 g / m < ² > is preferable and 60-120 g / m < ² > is more preferable. In addition, when the composite strand D is included in the main filter layer M, the basis weight of the main filter layer M refers to the basis weight of the main filter layer M excluding the composite strand D.

When the basis weight of the melt blown nonwoven fabric A constituting the main filter layer M is small, the adhesiveness between the melt blown nonwoven fabric A and the nonwoven fabric B may be reduced. On the other hand, when the fabric weight is large, the multilayer filter is produced. Since the nonwoven fabric B becomes easy to form into a film, 30-110 g / m < ² > is preferable.

  Further, the average fiber diameter of the composite fiber 1 of the melt blown nonwoven fabric A constituting the main filter layer M is 0.8 μm or more and the average fiber diameter of the composite fiber 1 of the melt blown nonwoven fabric A constituting the sub filter layer S Is preferably smaller. This is because when the average fiber diameter of the composite fiber 1 of the melt blown nonwoven fabric A is thin, the thermoplastic resin component other than the thermal adhesive component of the molten resin is solidified when the molten resin is sprayed onto the nonwoven fabric B during the production of the laminated nonwoven fabric. In this case, the thermal adhesive component is also solidified, and the thermal fusion between the conjugate fiber and the nonwoven fabric B may be insufficient, and it may be possible to bring the jet nozzle closer to the nonwoven fabric B. This is because although the heat-bonding component of the molten resin is sufficiently softened, the thermoplastic resin component other than the heat-bonding component may be insufficiently solidified to maintain the fiber form. On the other hand, if the average fiber diameter of the composite fiber 1 of the melt-blown nonwoven fabric A is large, the fibers of the nonwoven fabric B are melted during the production of the laminated nonwoven fabric, and there is a possibility that the nonwoven fabric B may have holes.

  In the present invention, the average fiber diameter of the fibers refers to the number average fiber diameter. Specifically, the fiber cross section is magnified with a microscope to obtain a micrograph, and the fibers of each fiber shown in the micrograph. The diameter was measured, and the arithmetic average of the fiber diameters of these fibers was defined as the average fiber diameter of the fibers. In the case where a plurality of fibers are fusion-integrated, the fusion-integrated one is regarded as one fiber.

Further, if the basis weight of the non-woven fabric B constituting the sub-filter layer S is small, the sub-filter layer S may be broken when the sub-filter layer S is peeled off, so 10 g / m ² or more is preferable. 10 to 50 g / m ² is more preferable.

Further, if the basis weight of the melt blown nonwoven fabric A constituting the sub-filter layer S is small, the adhesion by heat fusion between the melt blown nonwoven fabric A and the nonwoven fabric B may be insufficient, so 10 g / m ² or more Is preferable, and 10 to 50 g / m ² is more preferable.

And although the fabric weight of the said sub filter layer S is based also on the number of layers of a sub filter layer, 20-100 g / m < ² > is preferable and 30-70 g / m < ² > is more preferable. In addition, when the composite strand D is included in the sub filter layer S, the basis weight of the sub filter layer S refers to the basis weight of the sub filter layer S excluding the composite strand D.

  Furthermore, the average fiber diameter of the composite fiber 1 of the melt blown nonwoven fabric A constituting the sub filter layer S is preferably 20 to 75 μm. This is because when the average fiber diameter of the composite fiber 1 of the melt blown nonwoven fabric A is thin, the thermoplastic resin component other than the thermal adhesive component of the molten resin is solidified when the molten resin is sprayed onto the nonwoven fabric B during the production of the laminated nonwoven fabric. In this case, the thermal adhesive component is also solidified, and the thermal fusion between the conjugate fiber and the nonwoven fabric B may be insufficient, and it may be possible to bring the jet nozzle closer to the nonwoven fabric B. This is because although the heat-bonding component of the molten resin is sufficiently softened, the thermoplastic resin component other than the heat-bonding component may be insufficiently solidified to maintain the fiber form. On the other hand, if the average fiber diameter of the composite fiber 1 of the melt-blown nonwoven fabric A is large, the fibers of the nonwoven fabric B are melted during the production of the laminated nonwoven fabric, and there is a possibility that the nonwoven fabric B may have holes.

  Further, the melt blown nonwoven fabric A of the sub-filter layer S may be a laminate of a plurality of melt-blown nonwoven fabrics so as to improve the filter action of the sub-filter layer S.

  In such a case, it is preferable that the composite fiber 1 constituting the melt blown nonwoven fabric laminated directly on the nonwoven fabric B is made thickest among the plurality of melt blown nonwoven fabrics.

  On the other hand, as described above, in the case where a plurality of meltblown nonwoven fabrics are laminated and integrated in the subfilter layer S, the composite fiber 1 constituting the meltblown nonwoven fabric A is used to reduce the pressure loss of the subfilter layer S. When the fiber diameter of the melt blown nonwoven fabric is increased and the number of melt blown nonwoven fabrics is increased, the basis weight of the melt blown nonwoven fabric that is laminated and integrated directly with the nonwoven fabric B is minimized and a large amount of fiber mass is generated. Further, a melt blown nonwoven fabric made of a composite fiber thicker than the composite fiber constituting the melt blown nonwoven fabric is laminated and integrated. The fiber diameter of the composite fiber of the melt blown nonwoven fabric that is further laminated and integrated on the melt blown nonwoven fabric that is directly laminated and integrated with the nonwoven fabric B is preferably 0.3 to 100 μm.

  And as shown in FIG.4 and FIG.5, the meltblown nonwoven fabric A and the nonwoven fabric B in the laminated nonwoven fabric C which comprises the main filter layer M at least between the meltblown nonwoven fabric A and the nonwoven fabric B in the laminated nonwoven fabric C, In the meantime, a plurality of composite strands D, D... Are arranged in parallel with each other at predetermined intervals, and the composite strand D, the melt blown nonwoven fabric A, and the nonwoven fabric B are formed by a thermal adhesive component described later of the composite strand D. And heat bonding may be integrated.

  FIG. 5 shows the multilayer filter F in which the composite strand D is interposed between the melt blown nonwoven fabric A and the nonwoven fabric B in all the laminated nonwoven fabrics C. The main filter layer M of the multilayer filter F is shown in FIG. The composite strands D, D... May be interposed only between the melt blown nonwoven fabric A and the nonwoven fabric B to be configured.

  Thus, by interposing the composite strand D between the melt blown nonwoven fabric A and the nonwoven fabric B in the laminated nonwoven fabric C, the mechanical strength of the laminated nonwoven fabric C can be reinforced, and the multilayer filter F is pleated. In this case, the pleated shape of the multilayer filter F can be more reliably maintained, and the adhesion and integration of the meltblown nonwoven fabric A and the nonwoven fabric B can be further strengthened.

  The composite strand D will be described in detail. The composite strand D has two or more kinds of thermoplastic resin components having different melting points, and a thermoplastic resin component having a relatively low melting point among these thermoplastic resin components. Occupies a part of the surface as a thermal bonding component.

  As the structure of the composite strand D, the composite strand D has the same structure as the composite fiber constituting the melt blown nonwoven fabric A described above. The thermoplastic resin constituting the composite strand D is also the same thermoplastic resin as the thermoplastic resin constituting the composite fiber of the meltblown nonwoven fabric A described above, but poly (butene-1) and high-density polyethylene. It is preferable to use at least one kind of thermoplastic resin selected from the group consisting of and a polypropylene-based resin in combination, which is easy to plastically deform and has excellent pleated shape retention of the multilayer filter F. More preferably, polyethylene and polypropylene resin are used in combination.

When the density of poly (butene-1) is low, melt spinning is sometimes difficult because it is soft and increases in viscosity. On the other hand, when it is high, spinnability is lowered and melt spinning cannot be performed. Therefore, 0.905 g / cm ³ or more and less than 0.930 g / cm ³ is preferable. In addition, the density of poly (butene-1) says what was measured based on the float-sink method prescribed | regulated to JISL1015-7.14.1.

  On the other hand, if the melting point of poly (butene-1) is low, melt spinning becomes difficult because it is soft and increases in viscosity. On the other hand, if it is high, spinnability may be reduced and melt spinning may not be possible. Therefore, it is preferably higher than 115 ° C and lower than 130 ° C.

  The thermoplastic resin constituting the composite strand D has the same melt flow rate as that of the thermoplastic resin used in the staple fiber in order to have the same stiffness and hardness as the staple fiber. It is preferable.

  Specifically, if the melt flow rate of the thermoplastic resin constituting the composite strand D is small, the extrusion pressure from the extruder may be too large, whereas if it is large, the fluidity of the molten resin increases. Since it may be impossible to obtain a composite strand having a desired thickness, 5 to 200 g / 10 min is preferable.

  And when the average diameter of the composite strand D is thin, the mechanical strength of the multilayer filter may be insufficient, or the shape retainability when the multilayer filter is formed into a pleated shape may be reduced. Since the filter performance of the multilayer filter may be lowered, it is preferably more than 100 μm and less than 2000 μm.

Furthermore, if the basis weight of the composite strand D is small, the mechanical strength of the multilayer filter may be insufficient, or the shape retainability when the multilayer filter is made pleated may decrease, Since the filter performance of a multilayer filter may fall, 50-1000 g / m < ² > is preferable. Note that the basis weight of the composite strands D, refer to the weight (g) of the composite strand D present in the multilayer filter F1m ² per.

In addition, if the basis weight of the multilayer filter F is small, the filter performance tends to deteriorate, whereas if it is large, penetration of the electric field during electret processing may be difficult, so 50 to 500 g / m ² is preferable. . In addition, in the basis weight of the multilayer filter F, when the composite strand D is included in the multilayer filter F, the basis weight of the multilayer filter F excluding the composite strand D is referred to.

  In addition, a nonwoven fabric made of activated carbon fibers may be laminated and integrated on the nonwoven fabric B constituting the main filter layer M to impart gas adsorption performance to the multilayer filter F. Such a nonwoven fabric made of activated carbon fibers can be obtained by firing a nonwoven fabric made of thermoplastic resin fibers in an oxygen-free environment at 650 to 700 ° C.

  A photocatalyst may be applied on the nonwoven fabric B constituting the main filter layer M. Thus, by apply | coating a photocatalyst on the nonwoven fabric B, the bacteria contained in the air which passes the multilayer filter F can be disinfected or inactivated, and environmental hygiene can be improved.

  And by making the fiber and / or composite strand which comprises the nonwoven fabric B which comprises the multilayer filter F contain a flame retardant, the nonwoven fabric B and / or the composite strand D are made flame-retardant, and a multilayer is carried out. The flame resistance of the filter F can be achieved.

In the present invention, when the unit of the fiber diameter is indicated by “dtex”, the unit of the fiber diameter can be converted to “μm” based on the following formula 1. However, in Formula 1, D is the fineness (dtex) of a fiber, and (rho) is the density (g / cm < ³ >) of the synthetic resin which comprises the fiber. In addition, when a fiber cross section is an irregular cross section, it converts into the fiber of the circular cross section which consists of the same area.

  Next, the manufacturing method of the multilayer filter F is demonstrated. First, the manufacturing apparatus E of the multilayer filter F is demonstrated. As shown in FIG. 6, the manufacturing apparatus E for the multilayer filter F includes a net-like conveyor E1 conveyed in a constant direction at a constant speed, and a nonwoven fabric B in a wound state disposed behind the conveyor E1. Non-woven fabric unwinding device E2 for unwinding and supplying onto the conveyor E1, and a predetermined interval in the width direction of the conveyor E1 (a direction perpendicular to the conveying direction of the conveyor E1), preferably disposed above the conveying start end of the conveyor E2, preferably Are arranged at equal intervals, and a plurality of strand extrusion nozzles E3 for continuously extruding a plurality of composite strands D onto the nonwoven fabric B, and above the conveyor E1 above the strand extrusion nozzles E3. It comprises a plurality of ejection nozzles E4 that are disposed in the front and are disposed at predetermined intervals, preferably at regular intervals, in the conveying direction and the width direction of the conveyor E1, respectively, and eject a molten resin forming a composite fiber. Although FIG. 6 shows the case where the ejection nozzles E4 are arranged in only one row in the conveyance direction of the conveyor E1, the ejection nozzles E4 may be arranged in a plurality of rows in the conveyance direction of the conveyor E1. Further, the net-like conveyor E1 is provided with a suction device (not shown) for sucking downward from above.

  First, the non-woven fabric B is continuously supplied from the non-woven fabric unwinding device E2 onto the conveyor E1 conveyed at a constant speed in a constant direction. Next, a plurality of composite strands D, D... Are continuously extruded onto the nonwoven fabric B from the strand extrusion nozzles E3, E3. D, D... Are arranged in parallel to each other. When the composite strand D is not interposed between the melt blown nonwoven fabric A and the nonwoven fabric B, the step of extruding the composite strand D from the strand extrusion nozzle E3 may be omitted.

  Thereafter, a continuous fibrous molten resin from each of the plurality of ejection nozzles E4 is sprayed toward the non-woven fabric B, and composite fibers formed by cooling the molten resin are deposited on the non-woven fabric B and combined. The fibers are entangled, and the composite fibers are further integrated at the entangled portion by the thermal adhesive force of their thermal adhesive components to form the meltblown nonwoven fabric A.

  Then, the melt-blown nonwoven fabric A and the nonwoven fabric B are laminated and integrated by the thermal adhesive force of the thermal bonding component 1 of the composite fiber 11 constituting the melt-blown nonwoven fabric A to form a laminated nonwoven fabric C.

  Here, in the multilayer filter F of the present invention, in order to form the fiber mass 2 in the melt blown nonwoven fabric A, the jet nozzles E4 and E4 adjacent to each other are brought close to each other and jetted from the jet nozzles E4 and E4 adjacent to each other. The fibrous molten resin is irregularly contacted and aggregated and integrated before falling onto the nonwoven fabric B to form a fiber lump 2. The fiber lump 2 is not formed on the entire meltblown nonwoven fabric A. It exists regularly and uniformly dispersed.

  Specifically, the interval between the ejection holes of the ejection nozzles E4 and E4 adjacent to each other in the transport direction of the conveyor E1 and the width direction of the conveyor E1 is preferably less than 1.5 mm, more preferably 1 mm or less. preferable.

  When a large amount of the fiber mass 2 is formed in the melt blown nonwoven fabric A, it is only necessary to increase the discharge amount of the molten resin from the ejection nozzle E4 and to reduce the hot air flow velocity. In the case of forming 2 less, it is only necessary to reduce the discharge amount of the molten resin from the ejection nozzle E4 and increase the hot air flow velocity.

  Furthermore, when the distance between the ejection hole of the ejection nozzle E4 and the nonwoven fabric B facing the ejection hole is short, a part of the constituent fibers constituting the nonwoven fabric B at the temperature of the molten resin ejected from the ejection nozzle E4. While there is a possibility that the nonwoven fabric B will be melted and formed into a film, if it is far away, thermal fusion between the composite fiber formed from the molten resin ejected from the ejection nozzle E4 and the nonwoven fabric B becomes insufficient, and the melt blown nonwoven fabric Since integration between A and the nonwoven fabric B may be insufficient, 5 to 25 cm is preferable.

  In this way, the fiber mass 2 is scattered in the meltblown nonwoven fabric A, and the meltblown nonwoven fabric A is thickened by increasing the thickness of the meltblown nonwoven fabric A portion where the fiber mass 2 exists.

  And the peripheral part of the fiber lump 2 in the melt blown nonwoven fabric A is a space | gap compared with the part in which the fiber lump 2 does not exist because the fiber lump 2 was formed by aggregation of the composite fibers 1 and 1. The melt blown nonwoven fabric A is formed with a bulky portion with a small fiber density (weight per unit area) where the fiber lump 2 is present, and a convex portion due to the fiber lump 2 on the surface. 3 is formed irregularly and entirely.

  Thus, in the melt blown nonwoven fabric A, the low density portion having a small fiber density is formed entirely and irregularly by the fiber lump 2, and the fluid permeability is improved by the presence of the low density portion, Reduces pressure loss.

  And the passage of the electric field is made good by the presence of the low density portion due to the fiber mass 2 of the melt blown nonwoven fabric A, and the laminated nonwoven fabric C is suitable for electret processing despite its high basis weight and bulkiness. It has become.

  Next, a plurality of laminated nonwoven fabrics C manufactured as described above are stacked in the thickness direction and heated and pressed to laminate the laminated nonwoven fabrics C, C,. Thus, the multilayer filter F can be obtained. In addition, the integration of the laminated nonwoven fabrics C and C is the thermal adhesive force of the thermal bonding component of the composite fiber constituting the melt blown nonwoven fabric A of the laminated nonwoven fabric C, or the thermal bonding of the constituent fibers of the nonwoven fabric B of the laminated nonwoven fabric C. By power.

  In this case, the lamination form of the plurality of laminated nonwoven fabrics C, C... Is not particularly limited, and the melt blown nonwoven fabric A and the nonwoven fabric B of the laminated nonwoven fabrics C, C. Alternatively, a plurality of laminated nonwoven fabrics C, C... May be laminated in a state where the melt blown nonwoven fabric A and the nonwoven fabric B are irregularly arranged in the thickness direction.

  As described above, when a plurality of laminated nonwoven fabrics C, C... Are overlapped and these laminated nonwoven fabrics C, C... Are heated and pressed in the thickness direction, either one of the laminated nonwoven fabrics C, C or When both the melt blown nonwoven fabrics A constitute a laminated surface of the laminated nonwoven fabrics C and C, the pressing force is applied to the convex portions 3, 3... Formed on the surface of the melt blown nonwoven fabric A of the laminated nonwoven fabric C. In particular, the laminated nonwoven fabrics C, C... Which are adjacent to each other are mainly heat-sealed and integrated at the convex portions 3, 3. The laminated nonwoven fabrics C and C adjacent to each other can be easily separated and separated simply by separating the portions.

  The multilayer filter F may be pleated to increase the filter area per unit area in use, but the multilayer filter F constitutes the multilayer nonwoven fabric C. Since the fiber lump 2 is formed in the meltblown nonwoven fabric A and the mass weight of the meltblown nonwoven fabric A is increased by the presence of the fiber lump 2, it is stiff and excellent in mechanical strength, and has a pleated shape. The form of the formed multilayer filter F can be stably maintained.

  Moreover, since the multilayer filter F is formed to be thick, it can be easily applied to the gear roll of the pleat folding machine, and the multilayer filter F can be formed into a desired pleated shape.

  And since the laminated nonwoven fabrics C and C of the multilayer filter F are firmly heat-sealed and integrated in the convex portion 3 of the melt blown nonwoven fabric A of the laminated nonwoven fabric C, the multilayer filter F is pleated as described above. Even when folded into a shape, the laminated nonwoven fabrics C and C are not completely separated from each other.

  Further, in the multilayer filter F, one laminated nonwoven fabric C as the outermost layer is used as the main filter layer M, and the remaining laminated nonwoven fabric C is used as the sub filter layer S. Although the case where C was comprised from the same laminated nonwoven fabric was demonstrated, even if the fabric weight of the laminated nonwoven fabric C which comprises the sub filter layer S is made smaller than the fabric weight of the laminated nonwoven fabric which comprises the main filter layer M, Good.

  In such a case, when producing the laminated nonwoven fabric C constituting the main filter layer M, the composite fibers are deposited on the nonwoven fabric B to produce the melt blown nonwoven fabric A, and then the composite fibers constituting the melt blown nonwoven fabric A The composite fibers having different kinds or different average fiber diameters are deposited on the melt blown nonwoven fabric A previously deposited on the nonwoven fabric B, whereby the melt blown nonwoven fabric A is laminated and integrated over the nonwoven fabric B over a plurality of layers. It is preferable.

  As described above, the basis weight of the main filter layer M is high, and the basis weight of the sub filter layer S is the same as or smaller than the basis weight of the main filter layer M, so that the sub filter layer S can ensure the passage of fluid while maintaining the passage of fine particles. In addition to capturing, fine particles that could not be captured by the sub-filter layer S can be captured by the main filter layer M, and the filter performance can be improved while maintaining the fluid permeability of the multilayer filter F. Can do.

  Further, the multilayer filter F can be easily electretized by subjecting the multilayer nonwoven fabric C, preferably the composite fiber 1 of the melt blown nonwoven fabric A of the multilayer nonwoven fabric C, to corona discharge treatment. By electretizing the filter F, it is possible to more effectively capture charged fine particles such as tobacco smoke.

  The multilayer filter of the present invention has two or more types of thermoplastic resin components having different melting points, and among these thermoplastic resin components, a thermoplastic resin component having a relatively low melting point is used as a thermal adhesive component on the surface. Melt blown containing a composite fiber that occupies a part as a constituent fiber, a plurality of composite fibers being partially aggregated and integrated to form a fiber lump, and a convex portion is formed on the surface by this fiber lump A plurality of laminated nonwoven fabrics composed of a nonwoven fabric A and a nonwoven fabric B that is laminated and integrated on one surface of the melt blown nonwoven fabric and includes fibers having a fiber diameter of 15 μm or more as a constituent fiber, and is laminated and integrated in a peelable manner. Therefore, it can be easily pleated without using reinforcing material, etc. due to its bulkiness, stiffness, and the form of the multilayer filter processed into a pleated shape is stable. It can be lifting, further, also the pressure loss is small by using falling even less long-term fiber during use.

  Furthermore, the multilayer filter according to the present invention can peel and remove the sub-filter layer exposed on the surface even when the sub-filter layer exposed on the surface is contaminated with use. The filter performance of the multilayer filter can be recovered and an excellent filter function can be exhibited over a long period of time.

  And since the laminated nonwoven fabric constituting the multilayer filter of the present invention is easy to perform electret processing, the multilayer filter is electretized to effectively capture and remove charged fine particles such as cigarette smoke. Can do.

Further, in the multilayer filter, the outermost laminated nonwoven fabric of the multilayer filters is a main filter layer, and the remaining laminated nonwoven fabric is a sub-filter layer, and the basis weight of the main filter layer is 50 to 200 g / m. ² and when the basis weight of the sub-filter layer is the same as or less than the basis weight of the main filter layer, the sub-filter layer captures fine particles while ensuring fluid passage, Fine particles that could not be captured by the sub-filter layer can be reliably captured by the main filter layer.

  In the multilayer filter, the melt-blown nonwoven fabric A and the nonwoven fabric B of the laminated nonwoven fabric constituting the main filter layer have two or more thermoplastic resin components having different melting points, and among these thermoplastic resin components A plurality of composite strands in which a thermoplastic resin component having a relatively low melting point occupies a part of the surface as a thermal adhesive component is disposed at predetermined intervals, and the composite strand includes the melt blown nonwoven fabric A and the above When integrated with non-woven fabric B, the main filter layer is strengthened by the composite strand to improve the handleability by making the entire multi-layer filter firm, and the pleatability of the multi-layer filter Multilayer filter that improves the shape of the multilayer filter that has been folded into a pleated shape and stably holds it over a long period of time. It can be exerted over the excellent filter performance for a long period of time.

In the multilayer filter, the composite fiber is a thermoplastic resin component having a density of 0.905 g / cm ³ or more and less than 0.930 g / cm ³ , a melting point of more than 115 ° C. and less than 130 ° C. and (butene-1), while containing the polypropylene-based resin, the composite strand, as a thermoplastic resin component, density of and less than 0.930 g / cm ³ at 0.905 g / cm ³ or more, the melting point In the case of containing at least one thermoplastic resin component selected from the group consisting of poly (butene-1) and high-density polyethylene having a temperature exceeding 115 ° C. and lower than 130 ° C., and a polypropylene resin While making the electret easier, the filter performance of the multi-layer filter can be further improved, while the thermal bonding between the composite fiber and the composite strand can be achieved. The melt-blown nonwoven fabric and the composite strand are improved in heat-fusability, and as a whole, the integration of the melt-blown nonwoven fabric A, the nonwoven fabric B, and the composite strand is strengthened, and the waist of the multilayer filter is strengthened. In addition, the pleatability of the multilayer filter can be improved.

(Examples 1-8, Comparative Examples 1 and 2)
A spunbonded nonwoven fabric B1 made of polypropylene fibers having the fiber diameters shown in Table 1 is first used from the nonwoven fabric unwinding device E2 using the same manufacturing apparatus as that shown in FIG. After being unwound and heated to 140 ° C., it was continuously fed onto the conveyor E1. The basis weight of the spunbond nonwoven fabric B1 was as shown in Table 1.

  Next, from each ejection hole of the ejection nozzle E4 having 850 ejection holes having a width of less than 70 cm capable of forming a composite fiber, the molten resin is maintained while maintaining the temperature of the ejection nozzle E4 at the temperature shown in Table 1. A spunbonded non-woven fabric is formed of a core-sheath type composite fiber that is discharged into a high-speed heated air flow and simultaneously formed into a continuous fiber shape by this high-speed heated air flow. A melt-blown nonwoven fabric A1 was formed by depositing on B1, and a laminated nonwoven fabric C1 obtained by laminating and integrating the melt-blown nonwoven fabric A1 on the spunbond nonwoven fabric B1 was obtained. A part of the composite fiber constituting the meltblown nonwoven fabric A1 entered the polypropylene fiber constituting the spunbond nonwoven fabric B1.

  In the melt blown non-woven fabric A1, a fiber lump 2 is formed irregularly, in which composite fibers are partially agglomerated and integrated, and the plurality of protrusions 3 are irregularly and entirely formed on the surface by the fiber lump 2. Was formed.

  The plurality of ejection holes of the ejection nozzle E4 are arranged in a lattice pattern by arranging a plurality of rows of ejection holes arranged in a direction perpendicular to the conveyance direction of the conveyor E1, and arranged in parallel in the conveyance direction. The distance between the ejection holes adjacent to each other in the ejection nozzle E4 (shown as “ejection hole interval” in Table 1) and the height from the conveyor E1 to the ejection hole of the ejection nozzle E4 (in Table 1, “ejection hole”). The height was indicated as shown in Table 1. Table 1 shows the average fiber diameter of the composite fibers constituting the melt blown nonwoven fabric A1, and the basis weight and thickness of the melt blown nonwoven fabric A1. In addition, in this invention, the thickness of the nonwoven fabric was measured based on JIS L-1913-6.1.2A method.

  On the other hand, using the same manufacturing apparatus as the manufacturing apparatus shown in FIG. 6 except that the strand extrusion nozzle is not provided, first, a spunbond made of polypropylene fibers having the fiber diameters shown in Table 1 from the nonwoven fabric unwinding apparatus E2. The nonwoven fabric B2 was unwound and heated to 140 ° C. and then continuously fed onto the conveyor E1. The basis weight of the spunbond nonwoven fabric B2 was as shown in Table 1.

  Next, the temperature of the ejection nozzle E4 is changed to the temperature shown in Table 1 from each ejection hole of the ejection nozzle E4 having 850 ejection holes having a width of less than 70 cm on which the composite fiber can be formed on the spunbond nonwoven fabric B2. While being held, the molten resin is discharged into the high-speed heating airflow and simultaneously formed into a continuous fiber shape by this high-speed heating airflow, and the core-sheath type composite fiber comprising the core component and the sheath component shown in Table 1 is spunbonded nonwoven fabric A meltblown nonwoven fabric A2 was integrally formed by being deposited on B2, and a laminated sheet G1 obtained by laminating and integrating the meltblown nonwoven fabric A2 on the spunbond nonwoven fabric B2 was obtained, and this laminated sheet G1 was wound up. A part of the composite fibers constituting the meltblown nonwoven fabric A2 had entered the polypropylene fibers constituting the spunbond nonwoven fabric B2.

  In the melt blown non-woven fabric A2, the fiber lump 2 formed by agglomerating and integrating the composite fibers partially was irregularly and entirely formed. The ejection holes of the ejection nozzle E4 have a plurality of rows of ejection holes arranged in a direction inclined by 30 ° with respect to the direction orthogonal to the conveyance direction of the conveyor E1, and are arranged in the conveyance direction in parallel with each other. It is arranged in a lattice pattern, and the distance between the ejection holes adjacent to each other in the ejection nozzle E4 (shown as “ejection hole interval” in Table 1) and the height from the conveyor E1 to the ejection holes of the ejection nozzle E4 ( In Table 1, “injection hole height” was as shown in Table 1. Further, the average fiber diameter of the composite fibers constituting the meltblown nonwoven fabric A2 and the basis weight and thickness of the meltblown nonwoven fabric A3 are as shown in Table 1.

  Further, the laminated sheet G1 is continuously supplied onto the conveyor E1 from the nonwoven fabric unwinding apparatus E2 using the same production apparatus as that shown in FIG. 6 except that the strand extrusion nozzle is not provided. The temperature of the ejection nozzle E4 is maintained at the temperature shown in Table 1 from each ejection hole of the ejection nozzle E4 having 850 ejection holes having a width of less than 70 cm on which the composite fiber can be formed on the melt blown nonwoven fabric A2. The molten resin is discharged into the high-speed heating airflow and simultaneously formed into a continuous fiber shape by this high-speed heating airflow, and the core-sheath type composite fiber comprising the core component and the sheath component shown in Table 1 is deposited on the melt blown nonwoven fabric A2. The meltblown nonwoven fabric A3 is integrally formed, and the meltblown nonwoven fabric A2 and the meltblown nonwoven fabric A3 are laminated and integrated in this order on the spunbond nonwoven fabric B2. To obtain a laminated nonwoven fabric C2 having a thickness shown in 1.

  On the surface of the meltblown nonwoven fabric A3, a plurality of convex portions 3 were irregularly and entirely formed by the fiber mass 2 formed in the meltblown nonwoven fabric A2 or in the meltblown nonwoven fabric A2 and A3.

  The ejection holes of the ejection nozzle E4 are arranged in a lattice pattern by arranging a plurality of rows of ejection holes arranged in a direction inclined by 30 ° with respect to the conveyance direction of the conveyor E1, and arranged in parallel in the conveyance direction. The distance between the ejection holes adjacent to each other in the ejection nozzle E4 (indicated as “ejection hole interval” in Table 1) and the height from the conveyor E1 to the ejection hole of the ejection nozzle E4 (in Table 1, “ Table 1 shows the “ejection hole height”. Further, the average fiber diameter of the composite fibers constituting the melt blown nonwoven fabric A3 and the basis weight and thickness of the melt blown nonwoven fabric A3 are as shown in Table 1. The ejection nozzle E4 used when manufacturing the melt blown nonwoven fabrics A2 and A3 was skewed in a direction intersecting each other.

In Table 1, PP1, PP2, PB1, PB2, PM, and PT mean the thermoplastic resins shown below.
PP1: polypropylene (melting point: 163 ° C., melt flow rate: 40 g / 10 min, Q
Value (weight average molecular weight / number average molecular weight = 4)
PP2: polypropylene (melting point: 163 ° C., melt flow rate: 300 g / 10 minutes,
Q value (weight average molecular weight / number average molecular weight) = 4)
PB1: Poly (butene-1) (trade name “Toughmer BL700” manufactured by Mitsui Chemicals, Inc., melting point:
123 ° C., density: 0.917 g / cm ³ , melt flow rate: 28 g / 10
Minute, Q value (weight average molecular weight / number average molecular weight) = 2)
PB2: Poly (butene-1) (trade name “Toughmer PB0800” manufactured by Mitsui Chemicals, Ltd., melting point
: 123 ° C., density: 0.915 g / cm ³ , melt flow rate: about 200 g
/ 10 minutes, Q value (weight average molecular weight / number average molecular weight) = 2)
PM: Polymethylpentene (trade name “TPX” manufactured by Mitsui Chemicals, Ltd., melting point: 240 ° C.
(Rutto flow rate: 120 g / 10 min)
PT: polyethylene terephthalate (melting point: 260 ° C., melt flow rate: 110
g / 10 min, conventional limiting viscosity IV value: 0.64)

  Next, the laminated nonwoven fabric C1 and the laminated nonwoven fabric C2 are superposed so that the melt-blown nonwoven fabric A3 of the laminated nonwoven fabric C2 and the spunbond nonwoven fabric B1 of the laminated nonwoven fabric C1 face each other, and the thickness direction is as shown in Table 1. The laminated nonwoven fabrics C1 and C2 are pressed at the indicated pressing temperature, and are laminated and integrated so as to be peelable by the thermal adhesive force of the thermal bonding component of the composite fiber constituting the meltblown nonwoven fabric A3, and the laminated nonwoven fabric C2 is main filter A multilayer filter F having the layer M and the laminated nonwoven fabric C1 as the sub-filter layer S was obtained. The thickness of the multilayer filter F is shown in Table 1.

  Next, the obtained multilayer filter F was supplied into a dryer at 120 ° C. and dried. In the dryer and immediately after leaving the dryer, the temperature shown in Table 1 between the applied electrodes in which the needles were embedded at regular intervals, the voltage in the heating tank (indicated simply as “voltage in the tank” in Table 1), and A DC high electric field is generated under the conditions of the cooling unit voltage outside the heating tank (indicated simply as “cooling unit voltage” in Table 1), and the melt-blown nonwoven fabrics A1 to A3 of the multilayer nonwoven fabrics C1 and C2 of the multilayer filter F are produced. Electret processing was given to the composite fiber which comprises.

  In Example 8, the meltblown nonwoven fabric A3 was not laminated and integrated on the meltblown nonwoven fabric A2. Further, in Comparative Example 1, the distance between the ejection holes adjacent to each other was increased, so that the composite fibers were not aggregated and integrated, and a fiber lump was not formed. In Comparative Examples 1 and 2, since the laminated nonwoven fabric C1 and the laminated nonwoven fabric C2 could not be integrated, the electret processing, the collection efficiency and the pressure loss were in a state where the laminated nonwoven fabric C1 and the laminated nonwoven fabric C2 were overlapped. It was measured.

Example 9
Using the production apparatus shown in FIG. 6, a core-sheath type composite strand in which the core component is polypropylene and the sheath component is poly (butene-1) is extruded from the strand extrusion nozzles E3, E3. Implemented except that composite strands were arranged on the width direction at intervals of 5 mm on the top, and the melt-blown nonwoven fabric A2 was laminated and integrated on the spunbonded nonwoven fabric B2 on which the composite strands were arranged. A multilayer filter was produced in the same manner as in Example 8. The basis weight of the composite strand D was 300 g / m ² .

(Example 10)
On the surface of the sub-filter layer S of the multilayer filter F obtained in Example 1, a multilayer filter F is obtained by laminating and integrating a spunbond nonwoven fabric having a basis weight of 40 g / m ² made of polypropylene fibers having an average fiber diameter of 2 dtex. Manufactured.

(Example 11)
A multilayer filter F was obtained in the same manner as in Example 9, using the laminated nonwoven fabric C2 obtained in Example 8 as the sub-filter layer S and the laminated nonwoven fabric C2 obtained in Example 1 as the main filter layer M.

  The obtained multilayer filter F was supplied into a dryer at 120 ° C. and dried. In this dryer and immediately after leaving the dryer, a DC high electric field is applied under the conditions shown in Table 1 between the applied electrodes in which the needles are embedded at regular intervals, the voltage in the heating tank, and the voltage outside the heating tank. The composite fiber constituting the laminated nonwoven fabric C2 of the multilayer filter F and the melt blown nonwoven fabric of C2 was subjected to electret processing.

(Example 12)
Rayon fibers are obtained by laminating a card web made of rayon fibers having an average fiber diameter of 2 dtex on a spunbonded nonwoven fabric made of polypropylene fibers having a basis weight of 15 g / m ² and an average fiber diameter of 7 dtex, The spunbond nonwoven fabric and the card web were laminated and integrated to produce a nonwoven fabric B. Then, the nonwoven fabric B was used in place of the spunbond nonwoven fabric B2, and the meltblown nonwoven fabrics A2 and A3 were laminated and integrated on the spunbond nonwoven fabric of the nonwoven fabric B in the same manner as in Example 1 to produce a laminated nonwoven fabric C2.

  Next, a suspension is prepared by dispersing and suspending titanium oxide photocatalyst fine particles coated with apatite having a particle size of about 25 nm in water and having a titanium oxide photocatalyst fine particle concentration of 1% by weight. After the liquid is thinly applied to the surface of the metal roll and the suspension is transferred from the metal roll to the surface of the rubber-coated roll, the entire surface of the suspension is applied to the surface of the nonwoven fabric B of the laminated nonwoven fabric C2 using the rubber-coated roll. Was applied.

  Then, the laminated nonwoven fabric C1 produced in the same manner as in Example 1 and the laminated nonwoven fabric C2 are placed so that the melt-blown nonwoven fabric A3 of the laminated nonwoven fabric C2 and the spunbond nonwoven fabric B1 of the laminated nonwoven fabric C1 face each other. After overlapping, pressing in the thickness direction at the pressing temperature shown in Table 1 allows the laminated nonwoven fabrics C1 and C2 to be peeled off by the thermal adhesive force of the thermal bonding component of the composite fibers that make up the meltblown nonwoven fabric A3 Thus, a multilayer filter F having the laminated nonwoven fabric C2 as the main filter layer M and the laminated nonwoven fabric C1 as the sub-filter layer S was obtained. The thickness of the multilayer filter F is shown in Table 1.

  Next, the obtained multilayer filter F was supplied into a dryer at 120 ° C. and dried. In the dryer and immediately after leaving the dryer, the temperature shown in Table 1 between the applied electrodes in which the needles were embedded at regular intervals, the voltage in the heating tank (indicated simply as “voltage in the tank” in Table 1), and A DC high electric field is generated under the conditions of the cooling unit voltage outside the heating tank (indicated simply as “cooling unit voltage” in Table 1), and the melt-blown nonwoven fabrics A1 to A3 of the multilayer nonwoven fabrics C1 and C2 of the multilayer filter F are produced. Electret processing was given to the composite fiber which comprises.

  When the surface of the main filter M of the obtained multilayer filter F, that is, the surface coated with the titanium oxide photocatalyst fine particles was irradiated with ultraviolet rays using an ultraviolet lamp and room air was passed from the subfilter S side, the pressure loss was Although it increased to 7 Pas, the collection efficiency was 45% as in Example 1.

  When intense smoking was carried out by several persons indoors, the sub-filter S of the multilayer filter F was slightly yellowed, but the main filter F was not discolored at all.

  Moreover, each of the air that passed through the multilayer filter F of Example 1 and the air that passed through the multilayer filter F of Example 12 was filtered with a membrane filter to concentrate the bacteria, and the general bacteria were counted on the agar medium. When measured based on the method, a large number of colonies were observed in Example 1, but no colonies were observed in Example 12, and sterilization or bacteria were inactivated by the titanium oxide photocatalyst fine particles irradiated with ultraviolet rays. .

  Further, a multilayer filter F is produced in the same manner as described above except that the titanium oxide photocatalyst fine particles are applied to the nonwoven fabric B before the melt blown nonwoven fabrics A2 and A3 are laminated and integrated. When the bacteria were measured on an agar medium based on the colony counting method, no colonies were observed.

  The collection efficiency, pressure loss, peelability and pleatability of the obtained multilayer filter F were measured in the manner shown below, and the results are shown in Table 1.

(Collection efficiency and pressure loss)
In accordance with JIS B-9909, a multilayer filter is attached instead of a filter unit, and the collection efficiency of atmospheric dust with a particle size of 0.5 μm under the conditions of a measurement flow rate of 5.3 cm / sec and a filtration surface of 100 mmφ. And the pressure loss at the time of the measurement was measured. The inflow direction of air when measuring the collection efficiency is shown as “inflow direction” in Table 1. In addition, the case where it flowed in from the main filter layer M side was set as "reverse", and the case where air was flowed in from the sub filter layer S side was set as "normal".

(Peelability)
The main filter layer and the sub filter layer of the multilayer filter F were peeled off by hand and judged based on the following criteria.
Excellent: Sub filter layer has enough waist, and both filter layers are easily separated from each other
I was able to.
Good: Separate both filter layers from each other without damaging the sub-filter layer
I was able to.
Impossible ... The sub-filter layer was damaged when separating both filters from each other.

(Pleated)
While the multilayer filters obtained in Examples 1 to 7, 9, 10 to 12 and Comparative Examples 1 and 2 are pleated with a rotary pleat folding machine, the multilayer filter obtained in Example 8 is a reciprocating type. Pleated with a pleat folding machine and judged based on the following criteria.

Excellent: I was able to pleat it cleanly.
Good: The pleating crease was slightly disturbed.
Impossible ・ The sub filter layer peels off from the main filter layer during pleating.
I couldn't do pleating.

It is sectional drawing which showed an example of the composite fiber. It is a schematic cross section showing a laminated nonwoven fabric. It is the schematic cross section which showed the multilayer filter of this invention. It is the schematic cross section which showed another example of the laminated nonwoven fabric. It is the schematic cross section which showed another example of the multilayer filter of this invention. It is the model side view which showed an example of the manufacturing apparatus of a multilayer nonwoven fabric.

Explanation of symbols

1 Composite fiber 2 Fiber mass 3 Convex part
11 Thermal bonding components A, A1 to A4 Melt blown nonwoven fabric B Nonwoven fabric
B1, B2 Spunbond nonwoven fabric C, C1, C2 Multilayer nonwoven fabric D Composite strand
E4 Ejection nozzle F Multi-layer filter M Main filter layer S Sub-filter layer

Claims (8)

A composite fiber having two or more types of thermoplastic resin components having different melting points and a thermoplastic resin component having a relatively low melting point among these thermoplastic resin components occupying a part of the surface as a thermal bonding component As a constituent fiber, a plurality of composite fibers are partially aggregated and integrated to form a fiber lump, and a convex part is formed on the surface by this fiber lump, and this melt blown non-woven fabric A A multilayer filter comprising a plurality of laminated nonwoven fabrics that are laminated and integrated on one surface and made of a nonwoven fabric B that includes fibers having a fiber diameter of 15 μm or more as constituent fibers. 2. The multilayer filter according to claim 1, wherein a plurality of laminated nonwoven fabrics are laminated and integrated so that the melt-blown nonwoven fabric A and the nonwoven fabric B are alternately separated from each other. The outermost layer non-woven fabric of the multi-layer filter is used as a main filter layer, and the remaining laminated non-woven fabric is used as a sub filter layer. The basis weight of the main filter layer is 50 to 200 g / m ² , and the sub filter The multilayer filter according to claim 1 or 2, wherein a basis weight of the layer is the same as or less than a basis weight of the main filter layer. Between the melt blown nonwoven fabric A and the nonwoven fabric B of the laminated nonwoven fabric constituting the main filter layer, it has two or more types of thermoplastic resin components having different melting points, and has a relatively low melting point among these thermoplastic resin components. A plurality of composite strands in which a thermoplastic resin component having a part of the surface as a thermal adhesive component is disposed at predetermined intervals, and the composite strand is integrated with the melt blown nonwoven fabric A and the nonwoven fabric B. The multilayer filter according to any one of claims 1 to 3, wherein the multilayer filter is provided. The composite fiber has, as its thermoplastic resin component, poly (butene-1) having a density of 0.905 g / cm ³ or more and less than 0.930 g / cm ³ and a melting point of more than 115 ° C. and less than 130 ° C .; On the other hand, the composite strand has a density of 0.905 g / cm ³ or more and less than 0.930 g / cm ³ , a melting point of over 115 ° C. and 130 ° C. 5. The multilayer filter according to claim 4, comprising at least one thermoplastic resin component selected from the group consisting of poly (butene-1) and high-density polyethylene, and a polypropylene resin. . The composite weight of the main filter layer and the sub filter layer is 50 to 500 g / m ² , and the weight of the composite strand is 50 to 1000 g / m ^2. Layer filter. The multilayer filter according to any one of claims 1 to 6, wherein the composite fiber of the meltblown nonwoven fabric A is electretized. The multilayer filter according to any one of claims 1 to 7, wherein a photocatalyst is applied to a surface.

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