WO2018221063A1

WO2018221063A1 - Nonwoven fabric filter

Info

Publication number: WO2018221063A1
Application number: PCT/JP2018/016211
Authority: WO
Inventors: 崇西谷; 直樹柳岡
Original assignee: 日本バイリーン株式会社
Priority date: 2017-05-31
Filing date: 2018-04-19
Publication date: 2018-12-06
Also published as: JP7077515B2; JPWO2018221063A1

Abstract

The purpose of the present invention is to provide a nonwoven fabric filter with high shape retention properties such that crushing in the direction of thickness is not easy, even if wind pressure is applied, by suppressing increases in pressure loss and increasing dirt holding capacity. Provided is a nonwoven fabric filter provided with microfibers having a smaller fiber diameter than the average fiber diameter of fibers constituting a nonwoven fabric base material in the direction of the nonwoven fabric base material thickness, wherein the microfibers are oriented with a depth of 10 – 100% with respect to the apparent thickness of the nonwoven fabric base material, and a net-like part is formed by the microfibers or a combination of the microfibers and the fibers constituting the nonwoven fabric base material.

Description

Nonwoven filter

The present invention relates to a nonwoven fabric filter suitable for mounting on an air conditioner provided in a vehicle or a living environment, and particularly to a technique capable of maintaining a low pressure loss over a long period of time.

Conventionally, as a non-woven filter for long-term use, a composite fiber composed of relatively thick constituent fibers and relatively thin constituent fibers is used as a base material, and the base material is processed into a pleated shape to obtain a filter medium. Nonwoven fabric filters with a large area and low pressure loss are known. Moreover, in patent document 1, it is mesh | network in each mesh | network of the flat net member (A) comprised by the linear body, the mesh-shaped base part melt | fused with respect to the linear body, and the flat net member (A). Comprising a non-woven member (B) composed of a plurality of bulges bulged in the opposite direction to the basal base, the mesh having an average pore diameter of 1 mm to 30 mm, A nonwoven fabric filter composed of a composite fiber sheet having an average diameter of 0.01 mm to 10 mm is disclosed.

JP 2009-263811 A

The non-woven fabric filter described in Patent Document 1 has a structure that collects dust at a bulging portion provided from one surface of the striate body toward the other surface to ensure a dust holding amount. . However, such a nonwoven fabric filter collects dust at a high density on the upstream surface as the collection proceeds, so that the pressure loss increases quickly and the time to reach a certain pressure loss is practical. Above, there was still a problem that it was short. Furthermore, when the pressure loss increases, there is a problem that the filter medium is compressed by the wind pressure and breaks through in a very short time.

Accordingly, an object of the present invention is to provide a non-woven fabric filter that is highly resistant to deformation in the thickness direction even when wind pressure is applied and suppresses an increase in pressure loss and increases dust retention, and has high shape maintainability. To do.

The inventors of the present invention have conducted extensive research in view of the above problems. As a result, in the nonwoven fabric filter which has a microfiber in a nonwoven fabric base material, it discovered that the said subject could be solved by adjusting the aspect of the microfiber with respect to a nonwoven fabric base material, and came to complete this invention. Specifically, the present invention provides the following.

(1) 1st aspect of this invention is a nonwoven fabric filter provided with the microfiber which has a fiber diameter smaller than the average fiber diameter of a nonwoven fabric base-material constituent fiber in the thickness direction of a nonwoven fabric base material, Comprising: The said microfiber Is oriented with a depth of 10% or more and 100% or less with respect to the apparent thickness of the non-woven fabric substrate, and is formed by the fine fibers or a combination of the fine fibers and the non-woven fabric substrate constituting fibers. It is characterized by forming.

In addition, the “apparent thickness” referred to in the present invention refers to a dimension measured in a state where no external force is applied to the nonwoven fabric filter.

(2) A second aspect of the present invention is the nonwoven fabric filter according to (1), wherein in a filtration performance test by a mass method using ASHRAE dust defined in ASHRAE 52.1-1992, the wind speed is 0.30 m. The average mass method efficiency is 80% or more and 99% or less at the time of / sec, and the dust holding amount when the pressure loss rises to 100 Pa is 10.0 g / m ² or more. To do.

(3) A third aspect of the present invention is the nonwoven fabric filter according to (1) or (2), wherein the microfiber is a polyacrylonitrile resin, a polyethersulfone resin, a polyolefin resin, a polyester resin, or polyvinyl alcohol. It is formed by either resin or cellulose.

(4) A fourth aspect of the present invention is the nonwoven fabric filter according to any one of (1) to (3), wherein the nonwoven fabric base-constituting fibers are made of a polyester resin and a modified polyester resin. It is characterized by comprising a composite fiber.

The nonwoven fabric filter of the present invention has a nonwoven fabric substrate and microfibers, and the microfibers are oriented with a depth of 10% or more and 100% or less with respect to the apparent thickness of the nonwoven fabric substrate, A mesh portion is formed by a combination of fine fibers and non-woven fabric base constituent fibers. Thus, the presence of the net-like portion oriented mainly in the thickness direction of the non-woven fabric base material serving as a base enables filtration utilizing the thickness, and clogging is less likely to occur. For this reason, the nonwoven fabric filter of the present invention suppresses an increase in pressure loss, increases the amount of dust, and is not easily crushed in the thickness direction even when wind pressure is applied, and has high shape maintainability.

It is the electron micrograph which image | photographed the general | schematic cross section of the nonwoven fabric filter which concerns on Example 1A of this invention. It is an electron micrograph of the surface equivalent to the filtration surface of the nonwoven fabric filter which concerns on Example 1A of this invention. It is the electron micrograph which expanded the cross section of the nonwoven fabric filter which concerns on Example 1A of this invention. It is an electron micrograph which shows the general | schematic cross section of the nonwoven fabric filter which concerns on Example 1B of this invention similarly to FIG. 1A. It is an electron micrograph which shows the general | schematic cross section of the nonwoven fabric filter which concerns on Example 1C of this invention similarly to FIG. 1A. It is an electron micrograph which shows the general | schematic cross section of the nonwoven fabric filter which concerns on Example 1D of this invention similarly to FIG. 1A. It is the electron micrograph which expanded and photographed paying attention only to a mesh part among the nonwoven fabric filters shown in FIG. 5 is an electron micrograph in which only the mesh portion of the nonwoven fabric filter shown in FIG. It is the electron micrograph which image | photographed the nonwoven fabric filter which concerns on the comparative example 1A similarly to FIG. 1A. It is the electron micrograph which image | photographed the nonwoven fabric filter which concerns on the comparative example 2 similarly to FIG. 1A. This is an electron micrograph of a cross-section of a non-woven fabric filter produced by another microfiber forming technique, focusing on the area of the mesh portion where a single microfiber is substantially formed on the non-woven fabric substrate. . FIG. 10 is an electron micrograph of a cross-section of a non-woven filter produced by a technique different from the microfiber formation technique shown in FIG. It is the electron micrograph which expanded the microfiber about Drawing 10A.

The nonwoven fabric filter of the present invention is a nonwoven fabric filter comprising fine fibers having a fiber diameter smaller than the average fiber diameter of the nonwoven fabric substrate constituting fibers in the thickness direction of the nonwoven fabric substrate, It is oriented with a depth of 10% or more and 100% or less with respect to the apparent thickness, and the mesh portion is formed by microfibers or a combination of microfibers and nonwoven fabric constituting fibers. The filtration performance was evaluated by the mass method using ASHRAE dust according to the test method specified in ASHRAE 52.1-1992. When the test condition was a wind speed of 0.30 m / sec, the average mass method efficiency was It is preferably 80% or more and 99% or less, and the dust holding amount at the time when the pressure loss rises to 100 Pa is preferably 10.0 g / m ² or more. The average mass method efficiency is 85% or more and 99% or less, the dust retention amount is more preferably 40.0 g / m ² or more, and the average mass method efficiency is 90%. More preferably, the amount of dust is 99% or less, and the dust holding amount is 60.0 g / m ² or more. Examples of suitable forms of each configuration are as follows.

[Nonwoven fabric substrate]
The nonwoven fabric filter of the present invention has a nonwoven fabric substrate that retains the form of the nonwoven fabric filter and can support fine fibers. The average fiber diameter of the nonwoven fabric base material constituting fiber is not particularly limited, but is preferably 7 μm or more, more preferably 10 μm or more, and further preferably 15 μm or more so as to be excellent in the above action. preferable. In particular, when the average fiber diameter is 15 μm or more, an increase in pressure loss is suppressed, the amount of dust retained is increased, and even if wind pressure is applied, the shape is not easily crushed and has high shape maintainability. In addition, although the upper limit of the average fiber diameter of a nonwoven fabric base constituent fiber is not specifically limited, It is preferable that it is 100 micrometers or less so that filtration efficiency may be excellent. The “fiber diameter” in the present invention is a value obtained when a fiber existing on the surface of the substrate or inside the substrate is photographed and observed using a scanning electron microscope (SEM: Scanning Electron Microscope; hereinafter referred to as SEM) and visually read. Means fiber diameter. The “average fiber diameter” means the number average value of fiber diameters obtained by reading 30 randomly extracted fibers in the same manner.

Nonwoven fabric base fibers include polyolefin resins (polyethylene, polypropylene, polymethylpentene, polyolefins having a structure in which a part of hydrocarbon is substituted with a cyano group or a halogen such as fluorine or chlorine), styrene resin, polyether resin (polyethylene). Ether ether ketone, polyacetal, phenol, melamine, urea, epoxy, modified polyphenylene ether, aromatic polyether ketone, etc.), polyester resin (polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, Polycarbonate, polyarylate, wholly aromatic polyester, unsaturated polyester, etc.), modified polyester resin, polyimide resin, polyamideimide resin , Polyamide resins (for example, aromatic polyamide, aromatic polyetheramide, nylon, etc.), resins having a nitrile group (for example, polyacrylonitrile, etc.), urethane resins, epoxy resins, polysulfone resins (polysulfone, polyethersulfone, etc.), Fluorine resin (polytetrafluoroethylene, polyvinylidene fluoride, etc.), cellulose resin, polybenzimidazole resin, acrylic resin (for example, polyacrylonitrile, acrylonitrile and vinyl chloride or vinylidene chloride copolymerized with acrylate or methacrylate) Organic fibers containing a known organic polymer, such as copolymerized modacrylic, and the like, and known inorganic fibers such as glass fibers and metal fibers can be used.

In addition, as the organic polymer that becomes the nonwoven fabric base-constituting fiber, either a linear polymer or a branched polymer may be used, and the organic polymer may be a block copolymer or a random copolymer. It does not matter whether the organic polymer has a three-dimensional structure or crystallinity.

As the nonwoven fabric substrate constituting fiber, one kind of resin component or a mixture of a plurality of resin components may be used. Also, it is possible to use a composite fiber in which a plurality of types of resin components are divided into different sections and combined non-uniformly. As the type of the composite fiber, any of a core-sheath type, a sea-island type, a side-by-side type, and an orange type may be used. If so, durability can be imparted because the adhesive strength is high when the nonwoven fabric substrate is produced and when the nonwoven fabric filter is used, which is most preferable. In addition, a combination of a composite fiber having a thermal adhesive component such as a thermoplastic resin and a general-purpose regular fiber having a single component, or a latent crimpable property having a plurality of resins having different thermal shrinkage rates. A composite fiber may be used.

Note that the nonwoven fabric base fiber is preferably composed of at least one kind of composite fiber made of a polyester resin and a modified polyester resin because the base material after heat bonding has high rigidity and is relatively inexpensive.

The basis weight of the nonwoven fabric base material is not particularly limited, but is preferably 50 g / m ² or more and 450 g / m ² or less so as to suppress an increase in pressure loss and increase the dust holding amount. It is more preferably 70 g / m ² or more and 300 g / m ² or less, and further preferably 100 g / m ² or more and 200 g / m ² or less. If the basis weight is lower than the lower limit of this preferable numerical range, the shape of the mesh portion becomes non-uniform, and it may be difficult to improve the dust holding amount. Moreover, when the said fabric weight is set higher than the said range, an early rise of pressure loss will be caused and the lifetime of a nonwoven fabric filter may become remarkably short.

[Microfiber]
The nonwoven fabric filter of the present invention is a nonwoven fabric filter comprising fine fibers having a fiber diameter smaller than the average fiber diameter of the nonwoven fabric substrate constituting fibers in the thickness direction of the nonwoven fabric substrate, Oriented with a depth of 10% or more and 100% or less with respect to the apparent thickness, and the net-like portion is formed by the microfiber or the combination of the microfiber and the non-woven fabric substrate constituent fiber. This is a non-woven fabric filter with high shape-maintainability that prevents clogging, prevents pressure clogging, suppresses increase in pressure loss, increases dust retention, and does not collapse in the thickness direction even when wind pressure is applied. is there. This shape maintaining property will be described in detail later, but the “thickness maintaining ratio” when subjected to the above-mentioned filtration performance test is preferably 95% or more, more preferably 97% or more, and still more preferably 98% or more. Thus, it is preferable to arbitrarily design the orientation and basis weight of the mesh portion.

The above-mentioned “thickness direction” means a direction substantially perpendicular to the main surface of the nonwoven fabric filter. The fine fibers may be present at any position on the nonwoven fabric substrate. For example, it can exist from at least one surface of the nonwoven fabric substrate to the inside, or can be present only within the nonwoven fabric substrate. In particular, if a form existing from at least one surface to the inside of the nonwoven fabric substrate is taken, a density gradient in which the upstream side becomes rough can be realized in the filter medium when the surface is used as the filtration downstream side. Furthermore, if the fiber diameter of the microfibers is smaller than the average fiber diameter of the nonwoven fabric base constituent fibers, dust that cannot be collected by the nonwoven fabric base material can be collected by the net-like portion. The fiber diameter of the microfibers is not particularly limited as long as it is smaller than the average fiber diameter of the nonwoven fabric base constituent fibers.
That is, when the average fiber diameter of the nonwoven fabric base constituent fiber is 7 μm or more, the fiber diameter of the microfiber is preferably 1 nm or more and less than 7 μm, and when the average fiber diameter of the nonwoven fabric base constituent fiber is 10 μm or more, The fiber diameter of the microfiber is preferably 1 nm or more and less than 10 μm. When the average fiber diameter of the nonwoven fabric base constituent fiber is 15 μm or more, the fiber diameter of the microfiber is preferably 1 nm or more and less than 15 μm, and preferably 1 nm or more. More preferably, it is 12 μm or less, and further preferably 0.1 μm or more and 10 μm or less. The electron micrograph of FIG. 6 shows the fiber diameter of the microfiber. Such microfibers are oriented with a depth of 10% or more and 100% or less with respect to the apparent thickness of the nonwoven fabric substrate, and form a net-like portion containing the microfibers, so that much dust is trapped. I can gather. The deeper the depth, the wider the range of the net-like portion containing the microfibers and the better the dust collecting ability. Therefore, the depth is 30% or more and 100% or less with respect to the apparent thickness of the nonwoven fabric substrate. It is preferably oriented with a depth, more preferably with a depth of 40% or more and 100% or less, and even more preferably with a depth of 50% or more and 100% or less. Here, “orientation with a depth of 10% or more and 100% or less with respect to the apparent thickness” means 10% or more and 100% or less of the value of the thickness with respect to the apparent thickness of the substrate. The state where the “net-like part” has reached the depth.

This microfiber depth measurement method uses 10 electron micrographs of a non-woven fabric filter cross section, and in each photo, select 10 points that are equal in the plane direction of the non-woven fabric filter, and stretch the mesh portion in the thickness direction. Is measured with three significant figures on the photograph. The 10-point average is calculated 10 times, and the average is defined as “depth” (2 significant digits). “Depth” as used herein does not necessarily match the length of the microfiber, and is defined as the deepest distance of the fiber from the surface closer to the microfiber existing portion at the location selected as the observation site of the cross-sectional photograph. To do. For example, when different microfibers are continuously observed from one surface to the other surface in the base material, the deepest portion is defined as “depth”. In addition, with respect to the “apparent thickness” of the nonwoven fabric substrate, the nonwoven fabric substrate is averaged using the same method as the average thickness of the nonwoven fabric substrate extending in the thickness direction. The apparent thickness of the substrate (2 significant digits) was used.

The net part in the present invention may be a case where the net part is composed of fine fibers and non-woven fabric base constituent fibers. More specifically, as the form of the “net-like part”,
(A) A state in which microfibers having branches are connected mainly in the thickness direction across the nonwoven fabric base constituent fibers as shown in FIGS. 10A and 10B described later, for example. (B) Microfibers having relatively few branches However, as shown in FIG. 9 to be described later, for example, a state (columnar shape) connected across the thickness direction of the nonwoven fabric substrate
(C) The state in which the branched microfibers are connected in the form of pockets within the nonwoven fabric substrate as shown in FIG.
It is possible to improve the shape maintaining property of the nonwoven fabric filter in any state. The microfibers can be bonded and connected, or can be simply contacted and connected without bonding. In addition, it is preferable that the microfibers are fixed to any of other microfibers or non-woven fabric base constituent fibers. Thereby, the movement of the mesh part accompanying ventilation | gas_flowing can be suppressed by the pressure loss rise at the time of dust load, and re-scattering of the collection dust can be suppressed. Moreover, the arrangement | positioning position in the thickness direction of this mesh part may be any of the deeper positions than the surface part of the nonwoven fabric filter. For example, the density gradient can be provided in the nonwoven fabric filter by variously selecting the arrangement position in the thickness direction of the mesh portion. When the microfibers have a low density surface with relatively few microfibers, the life of the filter can be improved by using this for the inflow surface. Furthermore, it is preferable that the average hole diameter read with the photograph by SEM in the surface (filtration surface) used for the inflow surface of a nonwoven fabric filter is 5 micrometers or more, and it is preferable that it is 10 micrometers or more. By taking a large average aperture diameter, the pressure loss is low, the space for holding the dust is increased, and clogging is less likely to occur. The “average hole diameter” as used herein refers to, for example, arbitrarily selecting 10 openings in an electron micrograph of the filtration surface taken at a predetermined magnification as shown in FIG. 1B, and configuring each opening. The diameter of a perfect circle inscribed in the fibers to be treated is regarded as “open hole diameter”, and the average value at 10 locations is defined as “average open hole diameter”. However, the perfect circle for reading the aperture diameter is to be read on a generally two-dimensional plane (front side in the electron micrograph), and the perfect circle for the aperture observed on the back side in the electron micrograph is from the object to be measured. Shall be excluded.

Although the constituent resin of the microfiber is not particularly limited, for example, polyvinylidene fluoride (PVDF) resin, polyvinylidene fluoride-hexafluoropropylene copolymer resin, polyacrylonitrile (PAN) resin, polyacrylonitrile-methacrylate copolymer Resin, polymethacrylic acid resin, polymethyl methacrylate resin, polyvinyl chloride resin, polyvinylidene chloride-acrylate copolymer resin, polycarbonate resin, polystyrene resin, polyethylene resin, polyethersulfone resin, polyolefin resin, polyester resin, polypropylene resin Nylon resin such as nylon 12, nylon-4, 6, etc., aramid resin, polyimide resin, polybenzimidazole resin, carbon nanotube, cellulose, cellulose acetate resin, acetic acid Rulose butyrate resin, polyvinylpyrrolidone-vinyl acetate resin, poly (bis- (2- (2-methoxy-ethoxyethoxy)) phosphazene) (poly (bis- (2- (2-methoxy-ethoxy))) phosphazene); MEEP ) Resin, polypropylene oxide resin, polyethylene imide (PEI) resin, polysuccinic acid ethylene (poly (ethylene succinate)) resin, polyaniline resin, polyethylene sulfide resin, polyoxymethylene-oligo-oxyethylene (poly (oxymethylene-oligo-oxyethylene)) ) Resin, SBS copolymer resin, polyhydroxybutyric acid resin, polyvinyl acetate resin, polyethylene glycol resin, polyvinyl alcohol Coal resin (partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol), polyvinyl pyrrolidone resin, polyethylene terephthalate resin, polyethylene oxide resin, collagen resin, polylactic acid resin, polyglycolic acid resin, poly D, L-lactic acid-glycolic acid copolymer Resins, polyarylate resins, polypropylene fumarate (poly (propylene fumarate)) resins, biodegradable polymers such as polycaprolactone, chitin and chitosan, water soluble resins such as polypeptides and proteins, coal tar pitch, petroleum pitch, etc. Examples of the pitch-based resin can be given. Among these, it is preferable that the resin is composed of any one selected from a polyacrylonitrile resin, a polyethersulfone resin, a polyolefin resin, a polyester resin, a polyvinyl alcohol resin, and a cellulose having good fiber-forming properties.

The basis weight of the microfiber is not particularly limited, but is preferably 0.1 g / m ² or more and 50 g / m ² or less so as to suppress an increase in pressure loss and to increase the dust holding amount. , 0.2 g / more preferably ^m is ² or more 40 g / ^{m 2} or less, further preferably 1.0 g / ^{m 2} or more 30 g / ^{m 2} or less, 2.0 g / ^{m 2} or more 15 g / ^{m 2} Most preferably:

[Method for producing nonwoven substrate]
As a manufacturing method of the nonwoven fabric base material used for the nonwoven fabric filter of the present invention, any means may be adopted as long as it is a well-known manufacturing method capable of realizing a nonwoven fabric as a base of a mesh portion containing microfibers. Specific nonwoven fabric substrate production methods include dry spinning, wet spinning, direct spinning (melt blow, spunbond, flash span), wet, or dry (eg card, airlay) ) After forming the fiber web (for example, a method in which the fibers constituting the fiber web are fused under pressure or no pressure, a method of bonding with a binder, a method of intertwining with a water stream or a needle, etc.) A known method such as the above can be used. Among these, after forming a fiber web by a dry method, the method of bonding fibers together can form a relatively bulky nonwoven fabric substrate and form a fine fiber network within the nonwoven fabric substrate. It is suitable because it is easy to do. By these production methods, it is preferable to prepare a nonwoven fabric substrate made of fibers having an average fiber diameter of 7 μm or more, more preferably a nonwoven fabric substrate made of fibers having an average fiber diameter of 10 μm or more, and an average fiber diameter of It is most preferable to prepare a nonwoven fabric substrate composed of fibers of 15 μm or more.

[Nonwoven fabric filter manufacturing method]
Next, the non-woven fabric filter of the present invention is formed by orienting the net-like portion containing microfibers with respect to the non-woven fabric substrate with a depth of 10% or more and 100% or less with respect to the apparent thickness of the non-woven fabric substrate. be able to. Examples of a method for forming a mesh-like portion containing microfibers include, for example, (a) a technique in which pulp-like microfibers are placed inside a substrate by a wet method and then fused and fixed (b) a solvent such as water or an organic solvent (C) A technique for discharging and spinning a synthetic resin dissolved in a base material by high-speed air and fixing it inside the base material (c) Dispersing fine fibers such as cellulose fibers having a nano-order fiber diameter in a solvent such as water, A technique of freeze-drying in a state in which at least a portion of the prepared nonwoven fabric base material is soaked (d) A resin material that is a raw material of microfibers is dissolved in a solvent, applied to at least a portion of the nonwoven fabric substrate, and freeze-dried Technology (e) A solution in which a resin material of microfibers is dissolved in a nonwoven fabric base material is applied, and an air flow is applied in the thickness direction of the base material to generate a mesh portion containing microfibers inside the nonwoven fabric base material. Technology Rukoto can. In selecting these technologies, by adopting a manufacturing method in which microfibers are easily oriented in the thickness direction of the base material, the shape maintenance property of the nonwoven fabric filter is increased, and the densification of the filter medium due to wind pressure is reduced. A manufacturing technique capable of preventing the decrease can be employed. As an example, when the technique (b) described above is employed, the structure of the above-described microfibers is formed by a die used for melt spinning or flash spinning, which is disposed at a distance of 100 mm or less from one surface of the nonwoven fabric substrate. While spraying the resin, suction may be performed from the other surface of the nonwoven fabric substrate. At this time, the constituent resin of the microfibers discharged from the base must be carried out in a state where the fluidity remains without solidifying until reaching the nonwoven fabric base constituent fibers, and the formation depth of the microfibers Therefore, the distance between the surface of the nonwoven fabric substrate and the die is more preferably 50 mm or less.

As mentioned above, although this invention was demonstrated using embodiment, it cannot be overemphasized that the technical scope of this invention is limited only to the range of the invention as described in said embodiment. It will be apparent to those skilled in the art that improvements can be made. Further, it is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

Hereinafter, the present invention will be described with reference to examples. In addition, this invention is not limited to the Example shown below at all.

[Preparation of nonwoven substrate]
Preparation of the bulky short fiber nonwoven fabric used as a nonwoven fabric base material is demonstrated.
(Examples 1 to 5, Comparative Example 1, Comparative Examples 3 and 4)
Commercially available core-sheath type composite fiber (fineness: 6.7.0), commercially available core-sheath type composite fiber (fineness: 17.0 dtex, fiber length: 51 mm) made of polyester resin and modified polyester resin, and commercially available core-sheath type composite fiber (fineness: 6. 6 decitex, fiber length 51 mm) and 20% by mass. This is applied to a card machine to form a web, entangled by a needle punch method, and then bonded between fibers with a hot air dryer at 150 ° C. to obtain a nonwoven fabric substrate. When the cross section of this base material was observed with an electron microscope and only 50 constituent fiber portions excluding the fusion point between the fibers were measured and observed, the average fiber diameter was about 37 μm. The nonwoven fabric substrate was used in Examples 1 to 5, Comparative Example 1, Comparative Examples 3 and 4.
(Example 6)
90% by mass of a commercially available core-sheath composite fiber (fineness 2.2 dtex, fiber length 51 mm) made of a polyester resin and a modified polyester resin, and a commercially available core-sheath composite fiber (fineness of 6. A non-woven fabric substrate (average fiber diameter of 15 μm) obtained by the same method as above using 6 dtex, fiber length 51 mm) and 10 mass% was used in Example 6.
(Example 7)
It consists of 50% by mass of a commercially available core-sheath type composite fiber (fineness 17.0 dtex, fiber length 51 mm) made of polyester resin and modified polyester resin, and 50% by mass of a commercially available polyester fiber (fineness 33 dtex, fiber length 76 mm). A nonwoven fabric substrate (average fiber diameter of 54 μm) was prepared by the same method as described above and used in Example 7.
(Comparative Example 2)
As a base material other than the non-woven fabric, a commercially available polyester resin mesh disclosed in Patent Document 1 described above (a pore diameter of 3 mm and a wire diameter of 0.8 mm defined by the mesh) is prepared. Using. In this comparative example 2, since the fine fibers come out to the back side of the substrate due to the mesh size, the suction condition is suppressed in the initial stage of discharging the fine fibers, and the discharge deposition is performed in several stages. By stacking and gradually increasing the suction conditions, the configuration shown in FIG. 8 was realized.

[Formation of microfibers by discharging solution]
The production apparatus disclosed in Japanese Patent Application Laid-Open No. 2012-154209 was used for the discharge formation of microfibers on the various substrates described above. For the spinning solution to be discharged, commercially available polyacrylonitrile resin is prepared in various predetermined viscosities using dimethylformamide (DMF) as a solvent, and the separation distance between the conveyor and the base disposed in the apparatus is changed, respectively. Nonwoven filter samples were prepared. In addition, about the nonwoven fabric filter which concerns on Example 1A, 1B, 1C, 1D and Comparative example 1A, 1B, and Comparative example 2, it image | photographed using the electron microscope and observed and confirmed the cross-sectional state over the thickness direction. As shown in FIG. 1A to FIG. 5, in the nonwoven fabric filters according to Examples 1A, 1B, 1C, and 1D, a net-like portion containing microfibers, that is, a net-like portion where fibers constituting the microfibers are bonded to each other is confirmed. it can. In particular, in Example 1D shown in FIG. 4 or FIG. 5 in which the main part of FIG. 5 is enlarged, a number of substantially bag-like nets are formed as pocket-shaped components on one surface side of the nonwoven fabric filter. On the other hand, as shown in FIG. 7, in the nonwoven fabric filter according to Comparative Example 1A, it is understood that the mesh portion is hardly formed, and the microfibers formed by ejection are laminated and deposited on the surface of the nonwoven fabric substrate. it can. Furthermore, as shown in FIG. 8, in the nonwoven fabric filter according to Comparative Example 2, the above-mentioned commercially available polyester resin mesh is used as a base material, and a net-like part containing microfibers in the thickness direction of the base material, that is, a microscopic part. A net-like portion in which fibers are bonded to each other is not formed, and is formed so that a convex protrusion rises on the back side of the base material on which fine fibers are discharged and deposited. In Comparative Example 3, the viscosity of the polymer solution for forming microfibers (hereinafter abbreviated as “viscosity”) was lower than that in each Example, or because the absolute resin concentration was low, the droplets were coated on the substrate. It was not possible to form a net-like part. In addition, the nonwoven fabric filter comprised only with the nonwoven fabric base material without having a microfiber was used for the comparative example 4 as a blank.

Among these non-woven fabric filter samples, the main one is a thickness when a compression load of 20 g / cm ² specified in JIS L 1096 is applied by a commercially available Maeda type compression elasticity measuring instrument, and a thickness without any load. The ratio with (apparent thickness) was obtained as a percentage and recorded as the thickness retention rate. Table 1 shows the configuration of the nonwoven fabric substrate described above, the discharge formation conditions and configuration of the mesh portion formed thereon, and the thickness maintenance ratio.

As shown in Table 1, in Example 1A, the basis weight of the mesh portion is 5 g / m ² , the depth of the mesh portion is 2.8 mm, the thickness maintenance rate is as high as 99.3%, and it is good without almost being crushed. Was in good condition. Further, Example 1D configured with the same basis weight as that of Example 1A has a thickness maintenance ratio of 97.0% even when the depth of the mesh part is relatively shallow, 0.8 mm. Like 1A, it was not crushed by the wind pressure and maintained a good state. As shown in FIG. 1B, such a small pressure loss means that a relatively large opening of 5 μm or more is formed and the pressure loss is low as seen from the filtration surface side. On the other hand, in Comparative Example 1B (mesh portion depth 0.26 mm) in which microfibers are provided only on the surface of the base material, the thickness of the mesh portion is small even if the basis weight of the microfibers is increased. The retention rate was as low as 93.5%. Furthermore, in Comparative Example 2 prepared by imitating the technique of Patent Document 1 described above, since there is no base material skeleton for maintaining the thickness of the entire microfiber, the thickness maintenance ratio is 37.5%, It was judged that good filtration performance could not be exhibited.

[Dust load test]
The filtration performance was carried out in accordance with the test method of ASHRAE 52.1-1992 specified in JIS B9908 type 1. First, commercially available ASHRAE dust (composition: 72% Arizona street dust, 23% carbon black, 5% cotton linter; particle size range 0.3 μm to 0.5 μm until the pressure loss reaches 100 Pa at a wind speed of 0.30 m / sec. ), The average mass method efficiency and the amount of dust retained were determined. In this test, the substrate was mounted on a test apparatus so that the surface side of the substrate on which the fine fibers were discharged and deposited was upstream, and the performance of the mesh portion as a prefilter was evaluated. The initial pressure loss (Pa) was a value measured without supplying dust at the above wind speed. Table 2 shows measurement results of average mass efficiency, initial pressure loss, and dust retention. In addition, in the judgment column shown in Table 2, any of ◎, ○, × is described according to the following criteria, and since Comparative Example 4 does not include microfibers, “-” is described in the evaluation column. is doing.
(Double-circle): Average mass method efficiency was 85% or more, and the dust holding amount was 40 g / m < ² > or more.
A: The average mass method efficiency was 80% or more, and the dust retention amount was 10 g / m ² or more and less than 40 g / m ² .
X: The average mass method efficiency was less than 80%, or the dust retention amount was less than 10 g / m ² .

As shown in Table 2, the numerical values of average mass method efficiency, initial pressure loss, and dust holding amount were determined according to the above-mentioned criteria. As a result, all of the examples were good results. In particular, Examples 1A, 1B, 1C, 1D, 1E, 1F, 1G, 4, 5 and 7 gave better results. In Comparative Examples 1A and 1B, the deposition position of the microfibers was very shallow, and filtration was performed on the upstream surface of the nonwoven fabric filter, so the dust retention amount was very small. In Comparative Example 2, as in the other samples, the dust load was carried out with the surface different from the rising surface of the fine protrusions, that is, the rising surface of the convex protrusion, as in the other samples. As in 1A and 1B, the dust holding amount was extremely small. In Comparative Example 3, since the viscosity prepared as described above is low or the absolute resin concentration is low, the microfibers cannot be ejected, and as a result, there is no network part. Equally low value.

As confirmed above, in each example to which the present invention is applied, a net-like portion is formed in the internal space in the thickness direction of the nonwoven fabric substrate, so that the volume for holding relatively small particle size dust is increased. And an efficient non-woven filter was realized. On the other hand, in each comparative example, the fiber aggregates with fine fibers were formed in a plane on the surface of the nonwoven fabric substrate, or the net-like portion was not formed. For this reason, both the average mass method efficiency and the dust holding amount are not satisfied, and it was easy to break through early due mainly to small dust.

A non-woven fabric filter using another technique for forming microfibers will be described with reference to FIG. 9, FIG. 10A, and FIG. 10B. FIG. 9 shows a case in which a solution of polyvinyl alcohol resin using water as a solvent is applied to the surface of a nonwoven fabric substrate made of a core-sheath type composite fiber used in the above-described embodiment, and high-speed air is applied by a commercially available blower. It is the photograph which image | photographed the sample cross section which fibrillated the said resin and formed the microfiber with the electron microscope. As can be seen from the region surrounded by the alternate long and short dash line in the same figure, microfibers with few branches are formed in a large number of columns between the nonwoven fabric constituting fibers. It was expected that a high thickness maintenance ratio and a collection performance could be improved by the configuration provided with the columnar microfibers, and the same excellent filtration performance could be exhibited by the above-described measurement test.

Furthermore, the nonwoven fabric filter shown as FIG. 10A and FIG. 10B is prepared by impregnating a commercially available nanocellulose fiber dispersion into the same nonwoven fabric substrate and then removing the water of the dispersion medium with a freeze vacuum dryer. . In the same figure, a net-like net-like portion was confirmed in a region surrounded by a one-dot chain line. From this, it can be expected that the present structure improves a high thickness maintenance rate and collection performance, and the same excellent filtration performance can be exhibited by the above-described measurement test. As described above, the form of the microfiber defined in the present invention can be obtained by arbitrarily selecting the viscosity of the solution in which the resin is dispersed and the technology for fiberizing, so that the columnar shape (see FIG. 9) and the mesh shape (see FIG. 1A, FIG. 1B, FIG. 1C, FIG. 2, FIG. 3, FIG. 10A, FIG. 10B, etc.) or a bag shape (see FIG. 5). Even if the thickness maintenance ratio is improved and the aperture diameter of the nonwoven fabric base material is increased, it is possible to collect fine dust by providing a net-like part, and to achieve excellent filtration performance. did it.

Claims

A nonwoven fabric filter comprising fine fibers having a fiber diameter smaller than the average fiber diameter of the nonwoven fabric substrate constituting fibers in the thickness direction of the nonwoven fabric substrate,
The microfibers are oriented with a depth of 10% or more and 100% or less with respect to the apparent thickness of the nonwoven fabric substrate,
A nonwoven fabric filter in which a net-like portion is formed by the microfibers or a combination of the microfibers and the non-woven fabric substrate-constituting fibers.
In the filtration performance test by the mass method using ASHRAE dust specified in ASHRAE 52.1-1992, when the wind speed is 0.30 m / sec, the average mass method efficiency is 80% or more and 99% or less, and the pressure loss is 100 Pa. The nonwoven fabric filter according to claim 1, wherein the dust retention amount at the time of rising to 10.0 g / m 2 or more.
The nonwoven fabric filter according to claim 1 or 2, wherein the microfiber is formed of any one of a polyacrylonitrile resin, a polyethersulfone resin, a polyolefin resin, a polyester resin, a polyvinyl alcohol resin, or cellulose.
The nonwoven fabric filter according to any one of claims 1 to 3, wherein the nonwoven fabric base-constituting fibers are composed of at least one kind of composite fibers composed of a polyester resin and a modified polyester resin.