JP2019099946A - Nonwoven fabric and filter medium for bag filter - Google Patents

Abstract

To provide a nonwoven fabric and a filter medium for a bag filter excellent not only in collection performance but also in pleat processability.SOLUTION: The non-woven fabric is characterized by containing an ultrafine fiber A having a fiber diameter D of 100 to 1000 nm and a fiber B having a fiber diameter larger than the ultrafine fiber A, and having a Gurley bending resistance of 2000 mgf or more.SELECTED DRAWING: None

Description

  TECHNICAL FIELD The present invention relates to a non-woven fabric and a filter medium for bag filters which are excellent not only in collecting performance but also in pleating property.

  The bag filter is, for example, suspended in the dust collection chamber of the dust collector and used for dust collection. By repeating the dust removal and dust collection, long-term dust collection can be performed.

  Conventionally, as such a bag filter, a non-woven fabric (felt) which has been entangled with a woven fabric or a needle punch has been used. And in recent years, the method of using a pleat type filter cloth for a pulse jet type dust collector has spread from the viewpoint of downsizing of the device. Furthermore, in order to collect finer dust due to air pollution problems such as PM 2.5, a filter of a type using nanofibers is used (see, for example, Patent Document 1).

  However, when a non-woven fabric containing nanofibers is used as a filter medium, there is a problem that the bending rigidity is low because the single fiber fineness of the fibers is small, and wrinkles are easily generated when pleating. On the other hand, although a non-woven fabric using a general-purpose type fiber of normal fineness is good in pleating processability, there is a problem that the collecting property is low.

JP, 2015-140495, A

  The present invention has been made in view of the above background, and an object thereof is to provide a non-woven fabric and a filter medium for bag filter which are excellent not only in collecting performance but also in pleating processability.

  As a result of intensive investigations to achieve the above-mentioned problems, the present inventors carefully design the constituent fibers and structure of the non-woven fabric to obtain a non-woven fabric and a filter medium for bag filter excellent not only in collecting performance but also in pleating properties. It came to complete this invention by finding that it was obtained and repeating earnestly examination.

  Thus, according to the present invention, “the ultrafine fibers A having a fiber diameter D of 100 to 1000 nm and the fibers B having a fiber diameter larger than that of the ultrafine fibers A are characterized in that the Gurley bending resistance is 2000 mgf or more. And a non-woven fabric.

At that time, it is preferable that the non-woven fabric further contains a binder fiber C. Moreover, it is preferable that a nonwoven fabric is a wet nonwoven fabric. Moreover, it is preferable that embossing is given to the nonwoven fabric. Moreover, it is preferable that the porosity of a nonwoven fabric exists in the range of 75 to 89%. Moreover, it is preferable that the thickness of a nonwoven fabric exists in the range of 0.5-2.5 mm. Moreover, it is preferable that the fabric weight of a nonwoven fabric exists in the range of 100-400 g / m < ² >.

  Moreover, according to this invention, the filter medium for bag filters which uses the said nonwoven fabric is provided. At that time, it is preferable that the 1 μm atmospheric dust collection rate is 60% or more. Moreover, it is preferable that pleating is given.

  ADVANTAGE OF THE INVENTION According to this invention, the nonwoven fabric and the filter medium for bag filters excellent in not only collection performance but also pleat processability are obtained.

In the present invention, it is a drawing substitute photograph of an embossed pattern (pattern 1, trans dotted line) that can be adopted. The vertical line pattern of 2.5 mm intervals is shown. In the present invention, it is a drawing substitute photograph of an embossing pattern (pattern 2, grid-like depth 1 mm) which can be adopted. The 1.5 mm lattice pattern is shown. It is a drawing substitute photograph of the embossing pattern (pattern 3, square pattern) which can be adopted in the present invention. A square pattern of 4 mm in width and 3 mm in length shows adjacent patterns. In the present invention, it is a drawing substitute photograph of the embossing pattern (pattern 4, grid-like depth 1.5 mm) which can be adopted. The 1.5 mm lattice pattern is shown. In the present invention, it is a drawing substitute photograph of an embossed pattern (pattern 5, cross hatching) that can be adopted. Vertical and diagonal line patterns are shown at 1 mm intervals.

  Hereinafter, embodiments of the present invention will be described in detail. In the present invention, the microfibers A have a fiber diameter D of 100 to 1000 nm (preferably 200 to 800 nm). The fiber diameter D is a single fiber diameter of an ultrafine fiber. If the fiber diameter is larger than 1000 nm, the collection performance may be reduced. On the other hand, if the fiber diameter is smaller than 100 nm, the dispersibility of the microfibers may be reduced and the collection performance may be reduced.

  The fiber diameter can be measured by photographing a single fiber cross-sectional photograph at a magnification of 30,000 with a transmission electron microscope TEM. At that time, in a TEM having a length measurement function, measurement can be performed utilizing the length measurement function. Further, in a TEM without a length measurement function, a photographed photograph may be enlarged and copied, and it may be measured with a ruler in consideration of the scale.

  At that time, when the cross-sectional shape of the single fiber is a modified cross-section other than a round cross-section, the diameter of the fiber shall be the diameter of the circumscribed circle of the cross-section of the single fiber.

  The ultrafine fiber A may be a long fiber, but a short fiber is preferable in order to enhance the dispersibility and obtain excellent collection performance. At that time, the fiber length (cut length) is preferably in the range of 0.3 to 1.5 mm (more preferably 0.4 to 0.7 mm). The ratio L / D of the fiber length L to the fiber diameter D is preferably in the range of 1000 or less (more preferably 200 to 800). If the ratio L / D is larger than 1000, there is a possibility that agglomerated fiber lumps will be formed due to poor dispersibility and the collection performance and strength may be reduced.

  As a fiber type of the said microfiber A, a polyester fiber or polyphenylene sulfide (PPS) fiber or polyolefin fiber or nylon (Ny) fiber or aramid fiber or glass fiber is preferable.

  Examples of polyesters that form polyester fibers include polyethylene terephthalate (PET), polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and aromatics such as isophthalic acid and metal salt of 5-sulfoisophthalic acid containing these as main repeating units. Aliphatic dicarboxylic acids such as dicarboxylic acids, adipic acid and sebacic acid, hydroxycarboxylic acid condensates such as ε-caprolactone, and copolymers with glycol components such as diethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, etc. preferable. The material may be polyester recycled by material recycling or chemical recycling, or polyethylene terephthalate as described in JP-A-2009-091694, which uses a monomer component obtained by using a biomass, that is, a substance of biological origin as a raw material. Furthermore, polyesters obtained using a catalyst containing a specific phosphorus compound and a titanium compound as described in JP-A-2004-270097 and JP-A-2004-211268 may be used.

  Any polyarylene sulfide resin forming a polyphenylene sulfide (PPS) fiber may be used as long as it belongs to a category called polyarylene sulfide resin. As a polyarylene sulfide resin, as its constituent unit, for example, p-phenylene sulfide unit, m-phenylene sulfide unit, o-phenylene sulfide unit, phenylene sulfide sulfone unit, phenylene sulfide ketone unit, phenylene sulfide ether unit, diphenylene sulfide unit And those containing a substituent-containing phenylene sulfide unit, a branched structure-containing phenylene sulfide unit, and the like. Among them, those containing 70 mol% or more, particularly 90 mol% or more of p-phenylene sulfide units are preferable, and poly (p-phenylene sulfide) is more preferable.

  Polyolefin fibers also include polypropylene fibers and polyethylene fibers. Also, nylon fibers include nylon 6 fibers and nylon 66 fibers. Further, aramid fibers include meta-aramid fibers and para-aramid fibers.

  The method for producing the ultrafine fibers A is not particularly limited, but the method disclosed in WO 2005/095686 is preferable. That is, in terms of fiber diameter and its uniformity, an island component comprising a fiber-forming thermoplastic polymer, and a polymer that is more easily soluble in an aqueous alkaline solution than the fiber-forming thermoplastic polymer (hereinafter referred to as “easily soluble” It is preferable that alkali reduction processing is applied to a composite fiber having a “sea component” (also referred to as “polymer”) and the above-mentioned sea component is dissolved and removed.

Here, when the dissolution rate ratio to the fiber-forming thermoplastic polymer forming the island component is 100 or more (preferably 300 to 3000), the island separation property is good. And is preferable. When the dissolution rate is less than 200 times, while the sea component in the central part of the fiber cross section is dissolved, the island component in the separated surface section of the fiber cross section is dissolved because the fiber diameter is small. Despite weight loss, the sea component at the center of the fiber cross section can not be completely dissolved away, leading to thickness spots on the island component or solvent erosion of the island component itself, and fibers of uniform fiber diameter can not be obtained There is a fear.

  Preferred examples of the easily soluble polymer for forming the sea component include polyesters having good fiber-forming properties, aliphatic polyamides, and polyolefins such as polyethylene and polystyrene. More specifically, polylactic acid, an ultrahigh molecular weight polyalkylene oxide condensation polymer, and a copolymer polyester of a polyalkylene glycol compound and 5-sodium sulfoisophthalic acid are preferable because they easily dissolve in an aqueous alkali solution. Here, the alkaline aqueous solution refers to potassium hydroxide, sodium hydroxide aqueous solution and the like. Besides this, as combinations of the sea component and the solution for dissolving the sea component, formic acid to aliphatic polyamide such as nylon 6 or nylon 66, trichloroethylene etc. to polystyrene, etc. (especially high pressure method low density polyethylene or linear (High density low density polyethylene), hot water, hydrocarbon based etching such as toluene and xylene, and hot water for polyvinyl alcohol and ethylene modified vinyl alcohol type polymer can be mentioned as an example.

  Among polyester polymers, polyethylene terephthalate copolymer having an intrinsic viscosity of 0.4 to 0.6 obtained by copolymerizing 6 to 12 mol% of 5-sodium sulfoisophthalic acid and 3 to 10% by weight of polyethylene glycol having a molecular weight of 4,000 to 12,000. Polymerized polyesters are preferred. Here, 5-sodium sulfoisophthalic acid contributes to the improvement of hydrophilicity and melt viscosity, and polyethylene glycol (PEG) improves the hydrophilicity. In addition, as the molecular weight of PEG is larger, it has a hydrophilicity-increasing effect that is considered to be attributed to its higher-order structure, but since the reactivity is deteriorated and it becomes a blend system, problems occur in heat resistance and spinning stability. there is a possibility. When the copolymerization amount is 10% by weight or more, the melt viscosity may be reduced.

  On the other hand, polyamides, polyesters, polyphenylene sulfides, polyolefins, etc. are mentioned as a suitable example as a poorly soluble polymer which forms an island component. Specifically, in applications requiring mechanical strength and heat resistance, polyesters include polyethylene terephthalate (PET), polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and isophthalic acid containing these as main repeating units Acids, aromatic dicarboxylic acids such as 5-sulfoisophthalic acid metal salts, aliphatic dicarboxylic acids such as adipic acid and sebacic acid, hydroxycarboxylic acid condensates such as ε-caprolactone, diethylene glycol, trimethylene glycol, tetramethylene glycol, hexa Copolymers with glycol components such as methylene glycol are preferred. Further, among polyamides, aliphatic polyamides such as nylon 6 (Ny-6) and nylon 66 (Ny-66) are preferable. In addition, polyolefins are characterized by being resistant to acids, alkalis, etc., and being able to be used as a binder component after being taken out as ultrafine fibers due to their relatively low melting point, high density polyethylene, medium density polyethylene, high pressure method Low density polyethylene, linear low density polyethylene, isotactic polypropylene, ethylene propylene copolymer, ethylene copolymer of vinyl monomers such as maleic anhydride, and the like can be mentioned as preferable examples. In particular, polyesters such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene terephthalate isophthalate having a copolymerization ratio of isophthalic acid of 20 mol% or less, polyethylene naphthalate, etc., or aliphatic polyamides such as nylon 6, nylon 66 etc. Since it has heat resistance and mechanical properties due to a high melting point, it can be applied to applications requiring heat resistance and strength as compared with ultrafine fibrillated fibers consisting of polyvinyl alcohol / polyacrylonitrile mixed spun fibers, which is preferable. The island component is not limited to the round cross section, but may be a modified cross section such as a triangular cross section or a flat cross section.

  With regard to the polymer forming the sea component and the polymer forming the island component, if necessary, a matting agent, an organic filler, and an antioxidant as long as the spinning properties and physical properties of the main fiber after extraction are not affected. Agents, heat stabilizers, light stabilizers, flame retardants, lubricants, antistatic agents, rust inhibitors, crosslinking agents, foaming agents, fluorescent agents, surface smoothing agents, surface gloss improvers, release agents such as fluorine resins, etc., And other additives may be included.

  In the sea-island composite fiber, the melt viscosity of the sea component at the time of melt spinning is preferably larger than the melt viscosity of the island component polymer. In such a relationship, even if the composite weight ratio of the sea component decreases to less than 40%, the islands will be joined together, or most of the island components will be joined and become different from the sea-island composite fiber. hard.

  The preferable melt viscosity ratio (sea / island) is in the range of 1.1 to 2.0, particularly 1.3 to 1.5. When this ratio is less than 1.1 times, the island component is joined during melt spinning. On the other hand, if it exceeds 2.0 times, the spinning tone tends to be reduced because the viscosity difference is too large.

  Next, the number of islands is preferably 100 or more (more preferably 300 to 1000). Moreover, the sea-island composite weight ratio (sea: island) is preferably in the range of 20:80 to 80:20. If it is this range, the thickness of the sea component between islands can be reduced, dissolution and removal of the sea component becomes easy, and conversion of the island component into microfibers becomes easy, which is preferable. Here, when the proportion of the sea component exceeds 80%, the thickness of the sea component becomes too thick, while when it is less than 20%, the amount of the sea component becomes too small and junction between islands is likely to occur. .

  As a nozzle used for melt spinning, arbitrary things, such as a thing having a hollow pin group for forming an island component, and a micropore group, can be used. For example, even with a spinneret in which a sea-island cross section is formed by joining a hollow pin or an island component extruded from a fine hole and a sea component flow whose flow path is designed to fill the gap and compressing this. Good. The discharged sea-island composite fiber is solidified by the cooling air, and pulled by a rotating roller or an ejector set to a predetermined take-up speed to obtain an undrawn yarn. The take-up speed is not particularly limited but is preferably 200 to 5000 m / min. If it is less than 200 m / min, the productivity may be deteriorated. At 5000 m / min or more, spinning stability may be deteriorated.

  The obtained fiber may be used as it is in the cutting step or the subsequent extraction step, or in order to match the target strength, elongation, and heat shrinkage characteristics, the cutting step or the heat treatment step may be used. It can be subjected to a subsequent extraction step. The drawing step may be a separate drawing method in which spinning and drawing are performed in separate steps, or a direct drawing method in which drawing is immediately performed after spinning in one step may be used.

  Next, the composite fiber is cut. It is preferable that such a cut be a tow bundled in units of several tens to several millions and cut with a guillotine cutter, a rotary cutter, or the like.

The microfibers C having the fiber diameter D can be obtained by subjecting the composite fiber to alkali reduction processing. At that time, in the alkali reduction processing, the ratio of the fiber to the alkali solution (bath ratio) is preferably 0.1 to 5%, and more preferably 0.4 to 3%. If the amount is less than 0.1%, the contact between the fiber and the alkaline solution is large, but the processability such as drainage may become difficult. On the other hand, if the amount is 5% or more, the amount of fibers is too large, so there is a possibility that the fibers will be entangled at the time of alkali reduction processing. The bath ratio is defined by the following equation.
Bath ratio (%) = (Fiber mass (gr) / alkaline aqueous solution mass (gr) x 100)

  Moreover, it is preferable that the processing time of alkali reduction processing is 5 to 60 minutes, and it is more preferable that it is 10 to 30 minutes. Less than 5 minutes may result in insufficient alkali reduction. On the other hand, in 60 minutes or more, even an island component may be reduced.

  Moreover, in alkali reduction processing, it is preferable that alkali concentration is 2 to 10%. If the amount is less than 2%, the alkali may be insufficient and the rate of weight loss may be extremely slow. On the other hand, if it exceeds 10%, alkali reduction proceeds too much, and there is a possibility that the island part may be reduced.

  In the ultrafine fiber A thus obtained, when the ultrafine fiber A is a drawn polyester fiber, the birefringence (Δn) becomes larger than 0.05.

  The non-woven fabric of the present invention includes not only the ultrafine fibers A but also fibers B having a fiber diameter larger than that of the ultrafine fibers A. In that case, it is preferable that the weight ratio of the said microfiber A exists in the range of 3 to 50 weight% with respect to nonwoven fabric weight. If the content of the ultrafine fibers C is less than 3% by weight, the collection performance may be reduced. Conversely, if the content of the microfibers is more than 50% by weight, the pressure loss may be large.

  As the fiber B, a fiber having a single fiber fineness of 0.05 dtex or more (more preferably 0.1 to 2.2 dtex) is preferable. If the single fiber fineness of the fiber B is smaller than 0.05 dtex, the bending resistance may be lowered and the pleating processability may be lowered. The length of the fiber B is preferably 3 to 8 mm.

  In the fiber B, as a fiber type, polyester fiber, polyphenylene sulfide (PPS) fiber, polyolefin fiber or nylon (Ny) fiber is preferable. Furthermore, it may be aramid fiber or glass fiber.

  In the nonwoven fabric of the present invention, it is preferable that the nonwoven fabric further contain a binder fiber C in order to increase the bending resistance and obtain excellent pleatability.

  In the binder fiber C, a fiber having a single fiber fineness of 0.05 dtex or more (more preferably 0.1 to 2.2 dtex) is preferable. If the single fiber fineness of the binder fiber C is smaller than 0.05 dtex, the bending resistance may be lowered and the pleating processability may be lowered. The length of the binder fiber C is preferably 3 to 8 mm.

  The binder fiber C is preferably a composite fiber or an undrawn fiber. In the case of undrawn fibers, the birefringence Δn is usually 0.05 or less. Further, the elongation of the undrawn fiber is usually 100% or more (preferably 100 to 800%).

  Here, as the composite fiber, a polymer component (for example, non-crystalline copolyester) which is fused by heat treatment at 80 to 170 ° C. applied after paper making and exhibits an adhesive effect is disposed in the sheath portion, and the melting point is higher than these polymers. Preferred is a core-sheath type composite fiber in which another polymer (for example, common polyester such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate) having a temperature of 20 ° C. or higher is disposed in the core.

  The binder fiber C may be a known binder fiber in which the binder component (low melting point component) forms all or part of the surface of the single fiber. For example, core-sheath composite fibers, eccentric core-sheath composite fibers, side-by-side composite fibers, etc. are exemplified.

  Here, the non-crystalline copolyester is terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodiumsulfoisophthalic acid, adipic acid, sebacic acid, azelaic acid, dodecanoic acid, 1,4-cyclohexane Acid components such as dicarboxylic acid, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, 1,4-cyclohexanediol, 1, It is obtained as a random or block copolymer with a diol component such as 4-cyclohexanedimethanol. Among them, use of terephthalic acid, isophthalic acid, ethylene glycol and diethylene glycol which are conventionally and widely used as main components is preferable in terms of cost. Such copolymerized polyester has a glass transition temperature in the range of 50 to 100 ° C. and does not exhibit a clear crystalline melting point.

  Moreover, as an undrawn fiber, the undrawn fiber spun at a spinning speed of preferably 800 to 1500 m / min (more preferably 900 to 1150 m / min) can be mentioned. Here, the undrawn fiber is preferably an undrawn fiber using, as at least one component, a polyester used for an island component or a sea component of the sea-island composite fiber. In particular, unstretched polyester fibers using polyester such as polyethylene terephthalate, polytrimethylene terephthalate and polybutylene terephthalate as at least one component, and unstretched polyphenylene sulfide (PPS) binder fiber using polyphenylene sulfide (PPS) as at least one component Preferred are unstretched nylon fibers using nylon such as nylon 6 and nylon 66 as at least one component, and unstretched polyolefin fibers using polyolefin such as polypropylene and polyethylene as at least one component. Undrawn yarn of sea-island composite fiber can also be used.

  As a polyarylene sulfide resin which forms an unstretched polyphenylene sulfide (PPS) binder fiber, any may be used as long as it belongs to a category called polyarylene sulfide resin. As a polyarylene sulfide resin, as its constituent unit, for example, p-phenylene sulfide unit, m-phenylene sulfide unit, o-phenylene sulfide unit, phenylene sulfide sulfone unit, phenylene sulfide ketone unit, phenylene sulfide ether unit, diphenylene sulfide unit And those containing a substituent-containing phenylene sulfide unit, a branched structure-containing phenylene sulfide unit, etc., among which those containing 70 mol% or more, particularly 90 mol% or more of p-phenylene sulfide unit Preferably, poly (p-phenylene sulfide) is more preferred.

  In the nonwoven fabric of the present invention, the structure and the production method are not particularly limited, and any of a needle punched nonwoven fabric, a spunlace nonwoven fabric, a wet nonwoven fabric and the like may be used, but a wet nonwoven fabric is preferable.

  As a method for producing a wet non-woven fabric, a production method is preferable in which a heat treatment is carried out after forming a multi-layer paper by combining a plurality of conventional fourdrinier paper machines, fourdrinier paper machines, round mesh paper machines or these. At that time, as the heat treatment process, either of the Yankee dryer or the air through dryer can be used after the paper making process. Also, after the heat treatment, calendering or embossing may be applied, such as metal / metal roller, metal / paper roller, metal / elastic roller and the like. In particular, when the non-woven fabric is embossed, the porosity of the non-woven fabric can be adjusted, which is preferable. In addition, embossing is a method of forming a pattern by thermocompression bonding with a pair of embossing rolls or an embossing roll and a flat roll. In the case where the flat rolls are thermocompression-bonded to each other, the thickness is too small, the bending resistance is too low, and the pleatability may be deteriorated.

  In the non-woven fabric thus obtained, it is important that the Gurley stiffness is at least 2000 mgf in at least one of the MD direction and the CD direction (preferably 2000 to 20000 mgf in at least one of the MD direction and the CD direction). If the Gurley type bending resistance is less than 2000 mgf in both the MD direction and the CD direction, wrinkles easily occur during pleating, which is not preferable. The Gurley stiffness is measured by the JIS L1913 general nonwoven fabric test method.

  Moreover, it is preferable that the porosity of this nonwoven fabric is in the range of 75 to 89% (more preferably 80 to 88%). When the porosity of the non-woven fabric is smaller than the above range, the pressure loss may be too large when the non-woven fabric is used as a bag filter medium. On the contrary, when the non-woven fabric has a porosity larger than the above range, when the non-woven fabric is used as a filter material for a bag filter, there is a possibility that the pleating processability and the collecting performance may be reduced.

  Moreover, it is preferable that the thickness of a nonwoven fabric exists in the range of 0.5-2.5 mm (more preferably 0.5-1.2 mm). If the thickness of the non-woven fabric is smaller than the above range, the bending resistance may be reduced, and the pleatability may be reduced. On the other hand, when the thickness of the non-woven fabric is larger than the above range, the pleats may be in close contact with each other and a sufficient filtration area may not be obtained.

Further, it is preferable that the basis weight of the nonwoven fabric is 100 to 400 g / ^{m 2} (more preferably 120~200g / ^{m 2)} is in the range of. If the basis weight of the non-woven fabric is smaller than the above range, the bending resistance may be reduced and the pleatability may be reduced. Conversely, if the basis weight of the non-woven fabric is larger than the above range, the pressure loss may be too large.

Next, the filter medium for bag filters of the present invention is a filter medium for bag filters which uses the non-woven fabric described above. Since this non-woven fabric is used for the bag filter filter medium, not only the collection performance but also the pleating processability is excellent.
In that case, as a collection performance, it is preferable that 1 micrometer air | atmosphere dust collection rate is 60% or more.

  In addition, the filter medium for bag filters is usually laminated | stacked and used for a base cloth. At that time, a needle punched non-woven fabric including a scrim is preferable as the base fabric. The scrim makes it possible to reduce the dimensional change even for the dust flow and the backwash pulse pressure.

It is preferable that it is in the range of 40-120 g / m < ² > as a fabric weight of this scrim. If the fabric weight is smaller than 40 g / m ² , plastic deformation with respect to wind pressure may cause blow leakage. Conversely, if the fabric weight is larger than 120 g / m ^2, resistance to the needle may occur in the needle punching process, and the scrim itself may cause an increase in pressure loss.

  As such a scrim, for example, a flat tissue woven fabric composed of long fibers or short fibers (preferably 5 to 20 doublets with a fiber length of 20 to 80 mm) having a single fiber fineness of 1.0 to 3.0 dtex is preferable. As fiber types, polyester fibers, polyphenylene sulfide (PPS) fibers, meta-type or para-type aromatic polyamide fibers and the like are preferable.

  Further, as the fibers constituting other than the scrim in the needle-punched nonwoven fabric, polyester fibers, polyphenylene sulfide fibers, meta-type wholly aromatic polyamide fibers, para-type wholly aromatic polyamide fibers, etc. are preferable.

The base fabric is also preferably a spunbonded nonwoven fabric. It is preferable that it is in the range of 100-400 g / m < ² > as a fabric weight of this spun bond nonwoven fabric. If the fabric weight is smaller than 100 g / m ² , rigidity at the time of forming a pleat may be insufficient, and shape deformation may occur due to wind pressure. Conversely, if the basis weight is larger than 400 g / m ² , the pressure loss may be large. Polyester fibers or polyphenylene sulfide fibers are preferable as fibers constituting such a spunbonded nonwoven fabric.

  A known method may be used as a method of laminating the non-woven fabric on the substrate. For example, any of a heat bonding method, a chemical bonding method using an adhesive, sewing and the like may be used.

  The bag filter can be sewn (for example, sewn into a bag) or pleated to be suitably used as a bag-shaped bag filter or a cartridge type bag filter in a dust collector or the like.

EXAMPLES The present invention will next be described in detail by way of Examples and Comparative Examples, which should not be construed as limiting the invention thereto. In addition, each measurement item in an Example was measured by the following method.
(1) Fiber diameter D
Using a transmission electron microscope TEM (with a length measuring function), a fiber cross-sectional photograph was taken at a magnification of 30,000 times, and the fiber diameter D (nm) was measured. However, the fiber diameter D used the diameter of the circumscribed circle in the monofilament cross section (average value of n number 5).
(2) Fiber length L
By means of a scanning electron microscope (SEM), the ultra-fine short fibers (short fibers A) before dissolution and removal of the sea component were placed on the base, and the fiber length L (mm) was measured at 20 to 500 times (n number 5) Average value of At that time, the fiber length L was measured utilizing the length measurement function of the SEM.
(3) Fabric weight The fabric weight (g / m < ² >) was measured based on JISP8124 (metric basis weight measurement method of paper).
(4) Thickness The thickness (mm) was measured based on JIS P8118 (Method of measuring thickness and density of paper and paperboard). The measurement load was measured at n = 5 at 75 g / cm ² and the average value was determined.
(5) Porosity The above-mentioned basis weight and thickness, the density of polyethylene terephthalate (PET) fiber were computed from the following formula, making 1.36 g / cm ³ .
Porosity (%) = 100-(((weight) / (thickness) / 1.36) x 100)

(6) Atmospheric dust collection rate The air velocity was adjusted to be 5.1 cm / sec, the atmospheric dust before and after the sample was counted with a particle counter, and the collection efficiency was calculated from the ratio.
Air dust collection efficiency (%) = (1-(number of air dust after sample passing / number of air dust before sample passing)) x 100
(7) Pressure loss The pressure (Pa) before and after passing the test piece was measured at the time of measuring the atmospheric dust collection efficiency, and the pressure difference was determined as a pressure loss.
(8) Pore diameter The minimum pore diameter (μm), the average pore diameter (μm), and the maximum pore diameter (μm) were determined by ASTM-F-316.
(9) Softness and hardness It measured based on the hardness and the Gurley method of a JIS L1913 general nonwoven fabric test method, and the softness-of-softness mgf was computed. 1 mgf is 0.98 × 10 ⁻³ cN.
(10) Dust holding amount: DHC · DHC distribution ratio
JIS 8 type dust is introduced into the filter at a concentration of 1 g / m ² and inflow velocity of 10 cm / sec, and the time until pressure loss reaches 2 kPa and the weight of dust held by the filter at that time are measured. As a result of converting into a holding amount, when it exceeds 40, x (failed) and 40 or less were made ○ (pass).
(11) Melt viscosity After setting the polymer after drying processing to the orifice set to the ruder temperature at spinning and holding it for 5 minutes, it is extruded by applying several levels of load and the shear rate and melt viscosity at that time are plotted Do. Based on the data, a shear rate-melt viscosity curve was prepared, and the melt viscosity at a shear rate of 1000 sec- ¹ was read.
(12) Alkali weight loss rate ratio Each polymer of sea component and island component is discharged from a spinneret with a circular hole with a diameter of 0.3 mm and a length of 0.6 mm, respectively, and taken at a spinning speed of 1000 to 2000 m / min. The undrawn yarn thus obtained was drawn to have a residual elongation in the range of 30 to 60% to produce a multifilament of 83 dtex / 24 filaments. The weight loss rate was calculated from the dissolution time and the dissolution amount, using a 1.5 wt% NAOH aqueous solution at 80 ° C. and a bath ratio of 100.

[Examples 1 to 4, Comparative Examples 1 to 14]
The island component is polyethylene terephthalate having a melt viscosity of 120 Pa · sec at 285 ° C, the sea component is 4% by weight of polyethylene glycol having an average molecular weight of 4,000 having a melt viscosity of 135 Pa · sec, and 5-sodium sulfoisophthalic acid The modified polyethylene terephthalate copolymerized with 9 mol% was used, and spinning was performed using an island number of 400 at a weight ratio of sea: island = 10: 90, and pulled at a spinning speed of 1500 m / min. The alkali weight loss rate difference was 1000 times. This was stretched 3.9 times and then cut to 1000 μm with a guillotine cutter to obtain a sea-island composite fiber for ultrafine fiber A. This was reduced by 10% with a 4% aqueous NaOH solution at 75 ° C., and this fiber was made into an ultrafine fiber A (fiber diameter 700 nm, fiber length 1 mm, aspect ratio 1400, round cross section).

  Next, microfiber A, polyethylene terephthalate fiber B having a fineness of 1.7 dtex × length 5 mm, and a core-sheath composite type thermoadhesive fiber as heat bonding fiber C, fineness of 1.7 dtex × length 5 mm, core polymer and sheath The polymer is formed by cross-sectional formation of a 50/50% by weight of an amorphous copolyester mainly composed of polyethylene terephthalate having a melting point of 256 ° C., terephthalic acid, isophthalic acid, ethylene glycol and diethylene glycol. These are compounded in the ratio of A: B: C = 30: 40: 30, an appropriate amount of dispersant / defoamer is added, and the dispersed slurry is wet-papered with a circular net, and after dewatering with a nip roller, I took it up. Subsequently, it was introduced while being unwound into a belt-type drier, and a network between binders was formed by heat shrinkage to form a fixed structure, and then it was wound up with a constant tension.

  Then, using a roller having an embossed pattern on one or both of the upper and lower sides, the distance between the upper and lower rollers was appropriately adjusted so as to obtain the target thickness at a temperature of about 100 ° C. to 200 ° C. in both upper and lower sides. Table 1 shows the evaluation results.

  ADVANTAGE OF THE INVENTION According to this invention, the nonwoven fabric and the filter medium for bag filters which were excellent not only in collection performance but in pleat processability are provided, The industrial value is very large.

Claims (10)

  A non-woven fabric comprising an ultrafine fiber A having a fiber diameter D of 100 to 1000 nm and a fiber B having a fiber diameter larger than that of the ultrafine fiber A and having a Gurley bending resistance of 2000 mgf or more.   The nonwoven fabric according to claim 1, wherein the nonwoven fabric further comprises a binder fiber C.   The nonwoven fabric according to claim 1 or 2, wherein the nonwoven fabric is a wet nonwoven fabric.   The nonwoven fabric according to any one of claims 1 to 3, wherein the nonwoven fabric is embossed.   The nonwoven fabric according to any one of claims 1 to 4, wherein the porosity of the nonwoven fabric is in the range of 75 to 89%.   The nonwoven fabric according to any one of claims 1 to 5, wherein the thickness of the nonwoven fabric is in the range of 0.5 to 2.5 mm. Woven cloth is in the range of 100 to 400 g / ^{m 2,} the nonwoven fabric according to any one of claims 1 to 6.   The filter medium for bag filters which uses the nonwoven fabric in any one of Claims 1-7.   The filter medium for bag filters according to claim 8, wherein the 1 μm atmospheric particulate matter collection rate is 60% or more.   The bag medium for filter according to claim 8 or 9, wherein pleating is applied.