JP7631789B2 - Spunbond nonwoven fabric, filter media for pleated filters of dust collectors, pleated filters of dust collectors, and high-volume pulse jet type dust collectors - Google Patents

Description

The present invention relates to a spunbond nonwoven fabric used for pleated filter substrates, etc., and a filter medium for pleated dust collector filters, pleated dust collector filters, and high-volume pulse jet type dust collectors that use the nonwoven fabric.

Conventionally, dust collectors have been used to remove and collect dust in working environments where dust is generated. Among them, pulse jet type dust collectors that can reduce the frequency of filter replacement are known. In this pulse jet type dust collector, the outside of the filter becomes the filtering surface, and the filter is attached to a filter gauge and operated. The pulse jet type dust collector has a mechanism that can perform backwashing by sending compressed air into the filter when the filter reaches a certain pressure. The filter is used repeatedly after dust accumulated on the outer surface of the filter is brushed off by backwashing. In addition, it is known that the filter of this pulse jet type dust collector is used in a pleated folded shape, and the pleated shape makes it possible to significantly increase the filtering area, reduce pressure loss, and improve collection performance. Therefore, the characteristics required for the nonwoven fabric used as a pleated filter are high rigidity for pleating, breathability for suppressing pressure loss, and the ability to filter dust at the surface layer and have the ability to brush off dust, and various woven and nonwoven fabrics have been proposed so far.

For example, it has been proposed to use a long-fiber nonwoven fabric that has been heat-sealed with an embossing roll as a pleated filter (see Patent Document 1).

On the other hand, as a heat-sealing method other than the embossing roll method, the so-called air-through method has been proposed, in which hot air is passed through the nonwoven fabric to heat-seal it (see Patent Document 2).

In addition, methods have been proposed that involve laminating nonwoven fabrics (see Patent Document 3) and combining nonwoven fabrics with a mixed layer of ultrafine fibers (filter material) (see Patent Document 4).

Patent No. 3534043 Japanese Unexamined Patent Publication No. 7-157960 Patent No. 4543332 Patent No. 5918641

However, the technology of heat fusing with an embossing roll as disclosed in Patent Document 1 has the problem that dust easily accumulates in the heat-sealed parts that have no breathability, resulting in a short service life. In addition, in the case of nonwoven fabric obtained by the air-through method as disclosed in Patent Document 2, there is no heat-sealed part as with an embossing roll, and there is no problem of impairing breathability, but there is a problem that dust easily gets inside due to the poor density due to the manufacturing process, and dust cannot be removed by backwashing, resulting in a short service life. Furthermore, even with the technologies disclosed in Patent Documents 3 and 4, although pressure loss can be reduced, there is a problem that accumulated dust cannot be sufficiently removed, making it difficult to extend the service life.

By the way, in the above-mentioned pulse jet type dust collector, in places such as chemical plants where it is necessary to process a large amount of air containing fine powder dust at 300 to 1500 L per minute, a high-volume pulse jet type dust collector is used. In order to improve the collection performance of the filter of the dust collector, a filter made of a porous film made of polytetrafluoroethylene (hereinafter sometimes written as "PTFE") and a nonwoven fabric is also known. However, since the filter used in the high-volume pulse jet type dust collector is subjected to high airflow and repeated backwashing, a base material such as a PTFE film that is likely to peel off is not bonded, and a spunbond nonwoven fabric alone is used as the spunbond nonwoven fabric for the filter. In addition, the spunbond nonwoven fabric for the filter used needs to have the rigidity to have the pleat shape retention to withstand dust collection under high airflow and repeated backwashing. However, conventional spunbond nonwoven fabrics for filters used for dust collection and removal have not been able to achieve both dust collection performance and breathability while also having sufficient rigidity to maintain the pleat shape and pleat processability under high airflow. In other words, if the fusion between the fibers is strengthened in an attempt to improve collection performance, the mesh size becomes smaller, leading to reduced breathability, while if the fusion between the fibers is loosened in an attempt to improve breathability, the mesh size becomes larger, not only reducing dust collection performance, but also making it impossible to maintain the pleat shape under high airflow due to the reduced rigidity, and causing fuzzing, which also causes problems with appearance.

In view of the above problems, the object of the present invention is to provide a spunbond nonwoven fabric, a pleated filter for a dust collector, and a high-volume pulse jet type dust collector that balance dust collection performance with breathability, has high rigidity with excellent pleat shape retention and pleat processability even under large capacity, and also has excellent dust removal properties.

The present invention employs the following means to solve the above problems. That is, the spunbond nonwoven fabric of the present invention is composed of thermoplastic continuous filaments consisting of a high melting point component and a low melting point component, has a partially fused fused portion and a non-fused portion that is not fused, has a basis weight CV value of 5% or less, and has angles R1 and R2 of the curves from the fused portion to the non-fused portion, which are different surfaces, and are both 15° or more, and R1<R2.

In a preferred embodiment of the spunbond nonwoven fabric of the present invention, the thermoplastic continuous filaments use polyethylene terephthalate as the high melting point component and a copolymer polyester or polybutylene terephthalate as the low melting point component.

In a preferred embodiment of the spunbond nonwoven fabric of the present invention, the area ratio of the fused portion is in the range of 5% to 20%.

In a preferred embodiment of the spunbond nonwoven fabric of the present invention, the thermoplastic continuous filaments have an average single fiber diameter of 12 μm or more and 26 μm or less.

The fused portion is fused from both the top and bottom of the spunbond nonwoven fabric.

The filter material for the pleated filter of the dust collector of the present invention is made using the above-mentioned spunbond nonwoven fabric.

The dust collector pleated filter of the present invention is made using the filter material for the dust collector pleated filter.

A preferred embodiment of the high-volume pulse jet type dust collector of the present invention uses the filter material for the dust collector pleated filter described above.

According to the present invention, a spunbond nonwoven fabric is obtained that has an excellent balance between dust collection performance and breathability, has high rigidity with excellent pleating processability and pleat shape retention, and also has excellent dust removal properties. Therefore, the spunbond nonwoven fabric of the present invention can be suitably used as a filter material for pleated filters that is used in combination with pleated filters, PTFE membranes, nanofibers, etc.

FIG. 1 is a cross-sectional view of a spunbond nonwoven fabric according to one embodiment of the present invention. FIG. 2 is a schematic perspective view showing an example of the filter material for a pleated filter of a dust collector of the present invention. FIG. 3 is a diagram for explaining the configuration of a test system for carrying out a collection performance test according to an embodiment of the present invention. FIG. 4 is a diagram for explaining the configuration of a test system for carrying out a dust brushing off property test according to an embodiment of the present invention.

The spunbond nonwoven fabric of the present invention is composed of thermoplastic continuous filaments consisting of a high melting point component and a low melting point component, has a partially fused fused portion and a non-fused portion, has a basis weight CV value of 5% or less, and has angles R1 and R2 of the curves from the fused portion to the non-fused portion, which are different surfaces, each of which is 15° or more and satisfies R1<R2. The following describes in detail the embodiments for carrying out the present invention. Note that the present invention is not limited to the following embodiments.

(Thermoplastic continuous filament)
As the thermoplastic resin that is the raw material of the thermoplastic continuous filaments that constitute the spunbonded nonwoven fabric of the present invention, polyester is particularly preferably used. Polyester is a polymer having an acid component and an alcohol component as monomers. As the acid component, aromatic carboxylic acids such as phthalic acid (ortho form), isophthalic acid, and terephthalic acid, aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and alicyclic dicarboxylic acids such as cyclohexane carboxylic acid can be used. As the alcohol component, ethylene glycol, diethylene glycol, polyethylene glycol, and the like can be used.

Examples of polyesters include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate, polylactic acid, and polybutylene succinate. Of the polyesters used as high melting point polymers described below, PET is the most preferred, as it has a high melting point, excellent heat resistance, and excellent rigidity.

Additives such as crystal nucleating agents, matting agents, pigments, mildew inhibitors, antibacterial agents, flame retardants, metal oxides, aliphatic bisamides and/or aliphatic monoamides, and hydrophilic agents can be added to these polyester raw materials, provided that the effects of the present invention are not impaired. Among these, metal oxides such as titanium oxide reduce surface friction of the fibers and prevent fusion between the fibers, thereby improving spinnability, and also improve the fusion properties of the nonwoven fabric by increasing thermal conductivity during fusion molding of the nonwoven fabric with a heated roll. Furthermore, aliphatic bisamides such as ethylene bisstearic acid amide and/or alkyl-substituted aliphatic monoamides have the effect of increasing the releasability between the heated roll and the nonwoven fabric web, thereby improving transportability.

Next, the thermoplastic continuous filaments constituting the spunbonded nonwoven fabric for filters of the present invention are composed of a high melting point component and a low melting point component. In a preferred embodiment, the high melting point component is polyethylene terephthalate, and the low melting point component is copolymerized polyester or polybutylene terephthalate. In a preferred embodiment, the thermoplastic continuous filaments are composite filaments in which a polyester-based low melting point polymer, which is a low melting point component having a melting point 10°C to 140°C lower than the melting point of the polyester-based high melting point polymer, is arranged around the polyester-based high melting point polymer, which is a high melting point component. In this way, when the spunbonded nonwoven fabric is formed by fusion, the composite polyester fibers (filaments) constituting the spunbonded nonwoven fabric are firmly fused to each other, so that the spunbonded nonwoven fabric for filters has excellent mechanical strength and can fully withstand dust processing under high airflow.

In the present invention, the melting point of a thermoplastic resin is measured using a differential scanning calorimeter (for example, "DSC-2" model manufactured by PerkinElmer Japan Co., Ltd.) at a heating rate of 20°C/min and a measurement temperature range of 30°C to 300°C, and the temperature at which the obtained melting endothermic curve gives an extreme value is taken as the melting point of the thermoplastic resin. For resins whose melting endothermic curve does not show an extreme value in the differential scanning calorimeter, the resin is heated on a hot plate, and the temperature at which the resin melts under a microscope is taken as the melting point.

When the thermoplastic resin is polyester, examples of combinations of a pair of a polyester-based high melting point polymer and a polyester-based low melting point polymer (hereinafter, the order may be polyester-based high melting point polymer/polyester-based low melting point polymer) include combinations such as PET/PBT, PET/PTT, PET/polylactic acid, and PET/copolymerized PET, and among these, the combination of PET/copolymerized PET is preferably used because of its excellent spinnability. In addition, isophthalic acid copolymerized PET is preferably used as the copolymerization component of copolymerized PET, because of its particularly excellent spinnability.

Examples of the composite form of the composite filament include a concentric core-sheath type, an eccentric core-sheath type, and an island-in-the-sea type. Of these, the concentric core-sheath type is preferred because it allows the filaments to be fused uniformly and firmly. Furthermore, the cross-sectional shape of the composite filament may be a circular cross-section, a flat cross-section, a polygonal cross-section, a multi-lobal cross-section, a hollow cross-section, and the like. Of these, a circular cross-sectional shape is a preferred embodiment of the filament.

The composite filament can be produced by, for example, blending fibers made of polyester-based high melting point polymers with fibers made of polyester-based low melting point polymers. However, in the blending method, uniform fusion is difficult, and for example, fusion is weak where the fibers made of polyester-based high melting point polymers are densely packed, resulting in poor mechanical strength and rigidity, making the fabric unsuitable for use as a spunbonded nonwoven fabric for filters. On the other hand, there is also a method in which low melting point polymers are applied to fibers made of polyester-based high melting point polymers by immersion or spraying, but in either case, it is difficult to apply the low melting point polymer uniformly on the surface or in the thickness direction, and the mechanical strength and rigidity are poor, making the fabric unsuitable for use as a spunbonded nonwoven fabric for filters.

The melting point of the polyester-based low melting point polymer in the present invention is preferably 10°C or more and 140°C or less lower than the melting point of the polyester-based high melting point polymer. By making it 10°C or more, preferably 20°C or more, more preferably 30°C or more lower, it is possible to obtain appropriate fusion properties in the spunbonded nonwoven fabric. On the other hand, by making the melting point of the polyester-based low melting point polymer 140°C or less, preferably 120°C or less, more preferably 100°C or less lower than the melting point of the polyester-based high melting point polymer, it is possible to suppress a decrease in the heat resistance of the spunbonded nonwoven fabric.

The melting point of the polyester-based high melting point polymer is preferably in the range of 200°C or more and 320°C or less. By setting the melting point of the polyester-based high melting point polymer to preferably 200°C or more, more preferably 210°C or more, and even more preferably 220°C or more, a filter with excellent heat resistance can be obtained. On the other hand, by setting the melting point of the polyester-based high melting point polymer to preferably 320°C or less, more preferably 300°C or less, and even more preferably 280°C or less, a large consumption of thermal energy for melting during nonwoven fabric production and a decrease in productivity can be suppressed.

The melting point of the polyester-based low melting point polymer is preferably in the range of 160°C or higher and 250°C or lower. By setting the melting point of the polyester-based low melting point polymer to preferably 160°C or higher, more preferably 170°C or higher, and even more preferably 180°C or higher, the filter has excellent shape retention even when it goes through a process in which heat is applied during the production of the pleated filter, such as heat setting during pleating. On the other hand, by setting the melting point of the polyester-based low melting point polymer to preferably 250°C or lower, more preferably 240°C or lower, a filter having excellent fusion properties during the production of the nonwoven fabric and excellent mechanical strength can be obtained.

The content ratio of the polyester-based high melting point polymer to the polyester-based low melting point polymer is preferably in the range of 90:10 to 60:40 by mass, and more preferably in the range of 85:15 to 70:30. By making the polyester-based high melting point polymer 60% by mass or more and 90% by mass or less, the rigidity and heat resistance of the spunbonded nonwoven fabric can be excellent. On the other hand, by making the low melting point polyester 10% by mass or more and 40% by mass or less, when the spunbonded nonwoven fabric is formed by fusion and used, the composite polyester fibers (filaments) constituting the spunbonded nonwoven fabric can be firmly fused to each other, resulting in excellent mechanical strength and sufficient resistance to dust collection under medium airflow.

The composite form of the composite polyester fiber may be, for example, a concentric core-sheath type, an eccentric core-sheath type, or an island-in-the-sea type. Of these, the concentric core-sheath type is preferred because it allows the filaments to be fused uniformly and firmly. Furthermore, the cross-sectional shape of the filament (single fiber) may be a circular cross-section, a flat cross-section, a polygonal cross-section, a multi-lobal cross-section, or a hollow cross-section. Of these, it is preferable to use a filament (single fiber) with a circular cross-sectional shape.

The average single fiber diameter of the thermoplastic continuous filaments constituting the spunbonded nonwoven fabric of the present invention is preferably in the range of 12 μm or more and 26 μm or less. By making the average single fiber diameter of the thermoplastic continuous filaments 12 μm or more, preferably 13 μm or more, more preferably 14 μm or more, the breathability of the spunbonded nonwoven fabric can be improved and the pressure loss can be reduced. In addition, the number of thread breaks when forming the thermoplastic continuous filaments can be reduced, and the stability during production can be improved. On the other hand, by making the average single fiber diameter of the thermoplastic continuous filaments 26 μm or less, preferably 25 μm or less, more preferably 24 μm or less, the uniformity of the spunbonded nonwoven fabric can be improved, the surface of the nonwoven fabric can be made dense, and the collection performance can be improved, such as making it easier to filter dust at the surface layer.

In the present invention, the average single fiber diameter (μm) of the spunbonded nonwoven fabric is determined by the following method.
(i) Ten small sample pieces are randomly taken from the spunbond nonwoven fabric.
(ii) The surface of the collected small sample is photographed using a scanning electron microscope or the like at a magnification of 500 to 2000 times, enabling the thickness of the fibers to be measured.
(iii) From the photographs taken from each small sample, 10 fibers are randomly selected (100 fibers in total) and their thickness is measured. The cross section of the fiber is assumed to be circular, and the thickness is taken as the fiber diameter.
(iv) The arithmetic average value is rounded off to one decimal place to obtain the average single fiber diameter.

(Method of manufacturing spunbond nonwoven fabric)
Next, a method for producing the spunbonded nonwoven fabric of the present invention will be described. The spunbonded nonwoven fabric of the present invention is produced by sequentially carrying out the following steps (a) to (c).
(a) A process in which a thermoplastic polymer is molten and extruded from a spinneret, and then pulled and drawn by an air sucker to obtain a thermoplastic continuous filament.
(b) Opening the resulting filaments and depositing them onto a moving net conveyor to form a fibrous web.
(c) subjecting the resulting fibrous web to partial fusion bonding.
Each of the above steps will now be described in more detail.

(a) Thermoplastic continuous filament forming step First, a thermoplastic polymer is melt-extruded from a spinneret. In particular, when a composite filament in which a polyester-based low-melting point polymer having a melting point lower than that of a polyester-based high-melting point polymer is used as a thermoplastic continuous filament, the polyester-based high-melting point polymer and the polyester-based low-melting point polymer are melted at a temperature higher than or equal to the melting point and lower than or equal to (melting point + 70°C), respectively, and a composite filament in which a polyester-based low-melting point polymer having a melting point lower than that of the polyester-based high-melting point polymer by 10°C to 140°C is disposed around the polyester-based high-melting point polymer is spun out from a fine hole by a spinneret having a temperature higher than or equal to the melting point (melting point + 70°C), and then the filament is pulled and stretched by an air sucker at a spinning speed of 4000m/min to 6000m/min to spin a filament having a circular cross-sectional shape.

(b) Fiber web forming process The spunbond nonwoven fabric of the present invention has a process in which spun thermoplastic continuous filaments are opened and sprayed, and then deposited on a moving net conveyer to obtain a fiber web. The opening method includes, for example, an electrically charged opening method or a method using a fiber opening plate, and the method using a fiber opening plate is particularly preferable. The use of a fiber opening plate increases the uniformity of the nonwoven fabric and provides excellent filter performance.

Even when composite polyester fibers are used, it is important that the nonwoven fabric is a spunbonded fabric made of the filaments (long fibers) described above. This makes it possible to increase the rigidity and mechanical strength compared to short fiber nonwoven fabrics made of discontinuous fibers, making it preferable for use as a pleated filter.

In the manufacturing method of the spunbonded nonwoven fabric of the present invention, it is also a preferred embodiment to temporarily fuse the fiber web collected on the net conveyer. For the temporary fusion, a method is preferably used in which the collected fiber web is fused with a pair of flat rolls, or a flat roll is placed on the net conveyer and fused between the net conveyer and the flat roll. Fusion with a flat roll is preferably performed by placing the web in an S-shape against a calendar roll consisting of a flat roll. In this way, the thickness of the nonwoven fabric can be guaranteed, and a filter with high air permeability can be obtained.

The linear pressure for temporary fusion is preferably 30 kg/cm or more and 70 kg/cm or less. By setting the linear pressure for temporary fusion to 30 kg/cm or more, more preferably 40 kg/cm or more, the strength required for pleating can be imparted to the nonwoven fabric when used as a spunbond nonwoven fabric for filters. By setting the linear pressure for fusion to 70 kg/cm or less, more preferably 60 kg/cm or less, the fabric can be made to have an appropriate thickness and ensure breathability as a filter.

The fusion temperature for temporary fusion is preferably 70°C to 120°C lower than the melting point of the polyester-based low melting point polymer. By setting the temperature in this way, transportability can be improved without excessively fusing the fibers together.

(c) Partial fusion process The spunbonded nonwoven fabric for filters of the present invention is partially fused, but the method of partial fusion is not particularly limited. Here, the fused part of the spunbonded nonwoven fabric for filters is called the fused part, and the other unfused part is called the nonfused part. Fusion by a hot embossing roll or a combination of an ultrasonic oscillator and an embossing roll is preferred. In particular, fusion by a hot embossing roll is most preferred from the viewpoint of improving the strength of the nonwoven fabric. The partial fusion process is preferably processed continuously from the web forming process. By processing continuously from the web forming process, the density of the fused part is increased, and a nonwoven fabric with excellent waist strength and excellent pleat moldability can be obtained as a spunbonded nonwoven fabric for filters. The temperature of fusion by a hot embossing roll is preferably 5°C to 60°C lower than the melting point of the polymer with the lowest melting point present on the fiber surface of the nonwoven fabric, and more preferably 10°C to 50°C lower. Excessive fusion can be prevented by setting the temperature difference between the melting points of the polymers with the lowest melting points present on the fiber surface of the nonwoven fabric by the hot embossing roll to 5° C. or more, more preferably 10° C. or more. On the other hand, uniform fusion can be achieved within the nonwoven fabric by setting the temperature difference between the melting points to 60° C. or less, more preferably 50° C. or less.

The line pressure for fusion is preferably 30 kg/cm or more and 90 kg/cm or less. By setting the line pressure for fusion to 30 kg/cm or more, more preferably 40 kg/cm or more, the strength required for pleating can be imparted to the nonwoven fabric when it is used as a spunbond nonwoven fabric for filters. By setting the line pressure for fusion to 90 kg/cm or less, more preferably 80 kg/cm or less, excessive fusion can be prevented.

The area ratio of the fused parts of the spunbonded nonwoven fabric of the present invention (hereinafter sometimes simply referred to as the fused area ratio) refers to the ratio of the fused parts (recesses) to the total area of the nonwoven fabric, and is preferably in the range of 5% to 20% of the total area of the nonwoven fabric. If the fused area ratio is 5% or more, more preferably 6% or more, and even more preferably 8% or more, the nonwoven fabric will have sufficient mechanical strength and will not be prone to fluffing on the surface. On the other hand, if the fused area ratio is 20% or less, more preferably 19.5% or less, and even more preferably 19% or less, the voids between the fibers will be reduced, increasing pressure loss and preventing a decrease in collection performance.

The fusion area ratio of the spunbonded nonwoven fabric is measured using a digital microscope (for example, "VHX-5000" manufactured by Keyence Corporation) and 100 rectangular frames of 1.0 cm x 1.0 cm parallel to the longitudinal and transverse directions of the nonwoven fabric are taken from any part of the spunbonded nonwoven fabric at a magnification of 20 times, and the area of the fusion part within the rectangular frame relative to the area of each of the 100 frames is measured and averaged, and the average is expressed as a percentage and rounded off to the nearest tenth place to obtain the fusion area ratio (%). When not expressed as a percentage, the fusion area ratio can be calculated by dividing the area ( ^cm2 ) of the fusion part within the rectangular frame by the area of the rectangular frame, 1.0 ^cm2 , and then rounding off to the nearest tenth place.

The fused portion forms a depression, and is formed by fusing the thermoplastic continuous filaments that make up the nonwoven fabric together with heat and pressure. In other words, the fused portion is the portion where the thermoplastic continuous filaments are fused and aggregated compared to other portions. When fusing by a heat embossing roll is adopted as the fusing method, the portion where the thermoplastic continuous filaments are fused and aggregated by the convex portion of the embossing roll becomes the fused portion. For example, when a roll having a predetermined pattern of unevenness only on the upper or lower side is used, and the other roll is a flat roll without unevenness, the fused portion refers to the portion where the thermoplastic continuous filaments of the nonwoven fabric are fused and aggregated by the convex portion of the roll having unevenness and the flat roll. Also, for example, when an embossing roll is used that is composed of a pair of upper and lower rolls on whose surface a plurality of linear grooves arranged in parallel are formed, and the grooves of the upper roll and the grooves of the lower roll are arranged so as to intersect at a certain angle, the fused portion refers to the portion where the thermoplastic continuous filaments of the nonwoven fabric are fused and aggregated by the convex portion of the upper roll and the convex portion of the lower roll. In this case, the fused portion between the upper convex portion and the lower concave portion, or the fused portion between the upper concave portion and the lower convex portion, is not included in the fused portion.

The area of each fused portion is preferably 0.3 ^mm2 or more and 5.0 ^mm2 or less. By making it ^{0.3 mm2} or more, sufficient mechanical strength as a spunbonded nonwoven fabric for filters can be obtained, and fuzzing on the surface of the nonwoven fabric can be suppressed. By making it 5.0 ^mm2 or less, in addition to the mechanical strength as a spunbonded nonwoven fabric for filters, breathability can be maintained, and sufficient collection performance can be obtained.

The shape of the fused portion is not particularly specified, and even when a roll having a predetermined pattern of unevenness only on the upper or lower side is used and the other roll is a flat roll without unevenness, or when an embossing roll is made up of a pair of upper and lower rolls with multiple parallel linear grooves formed on the surface, and the grooves of the upper roll and the grooves of the lower roll are arranged so as to intersect at a certain angle, and the convex parts of the upper roll and the convex parts of the lower roll are fused, the shape of the fused part may be a circle, a triangle, a rectangle, a parallelogram, an ellipse, a rhombus, etc. The arrangement of these fused parts is not particularly specified, and they may be arranged regularly at equal intervals, randomly, or a mixture of different shapes. Among them, fused parts arranged at equal intervals are preferable from the viewpoint of uniformity of the nonwoven fabric. Furthermore, in terms of partially fusing the nonwoven fabric without peeling it off, it is preferable to use an embossing roll consisting of a pair of upper and lower rolls on whose surfaces multiple parallel linear grooves are formed, with the grooves of the upper roll and the grooves of the lower roll intersecting at a certain angle, and to form a parallelogram-shaped fused portion formed by fusing the convex parts of the upper roll and the convex parts of the lower roll.

(Spunbond nonwoven fabric)
Next, the spunbonded nonwoven fabric of the present invention will be described.
The spunbonded nonwoven fabric of the present invention is made of the above-mentioned thermoplastic continuous filaments, and has a fused part which is partially fused and a non-fused part which is not fused. Fig. 1 is a cross-sectional view of a spunbonded nonwoven fabric according to one embodiment of the present invention. The spunbonded nonwoven fabric shown in Fig. 1 is ventilated from top to bottom during use. The spunbonded nonwoven fabric is partially fused. Specifically, the spunbonded nonwoven fabric has a fused part 101 formed by fusing the nonwoven fabric, and a non-fused part 102 which is not fused.

Furthermore, in the spunbond nonwoven fabric of the present invention, the angles R1 and R2 on the different surfaces of the curve extending from the fused portion 101 to the non-fused portion 102 (the angles between the boundary surfaces of the fused portion 101 and the non-fused portion 102) are both 15° or more, and R1<R2.

When the curve angles on both the upper and lower sides from the fused portion to the non-fused portion thus fused are R1 and R2, it is necessary that both the curve angle R1 and the curve angle R2 are 15° or more and R1<R2. Here, the curve angles R1 and R2 are angles formed by the boundary surfaces between the fused portion and the non-fused portion on different surfaces. If either the curve angle R1 or R2 is 15° or less, sufficient dust removability cannot be obtained, and even if R1=R2, sufficient dust removability cannot be obtained, and the rigidity and strength of the nonwoven fabric may be reduced. In order to obtain sufficient removability and rigidity and strength of the nonwoven fabric, it is necessary that both the curve angle R1 and the curve angle R2 are 15° or more and R1<R2. More preferably, the curve angle R1 is 15° or more and 30° or less, and the curve angle R2 is 45° or more and 75° or less. The curve angle R1 is the angle of the surface that takes in air before filtration, and the curve angle R2 is the angle of the surface that releases air after filtration (after passing through the nonwoven fabric).
In the present invention, the angles R1 and R2 (°) of the curves extending from the recesses to the protrusions of the fused portion of the spunbonded nonwoven fabric are measured and calculated as follows.
(i) In any fused portion, the intersection of the center line in the MD direction and the center line in the CD direction is defined as the center point of the fused portion.
(ii) Draw a straight line parallel to the CD direction through the center point of the fused portion.
(iii) Starting from two points on the line 0.5 cm away from the center point of the fused portion, a straight line is drawn 1.0 cm long along the MD direction, and a straight line is drawn connecting the end points of the straight line.
(iv) Cut out with a razor blade the area bounded by the 1.0 cm x 1.0 cm squares formed in (i)-(iii).
(v) In the same manner, a total of 100 measurement samples of 1.0 cm x 1.0 cm for the fused portion are taken from any positions within the spunbonded nonwoven fabric.
(vi) Using a scanning electron microscope (SEM) (for example, "VHX-D500" manufactured by Keyence Corporation), the cross section of the fused portion in the measurement sample for the fused portion is observed at a magnification of 100 times.
(vii) Draw tangent lines from two points on the bottom of adjacent fused portions (recesses).
(viii) Starting from the tangent line drawn in (vii) from the boundary between the fused portion (concave portion) and the non-fused portion (convex portion), a tangent line is drawn along the non-fused portion.
(ix) The angle formed by (vii) and (viii) is measured, and the average value obtained is rounded off to the first decimal place to form the angle (°) of the curve extending from the recess to the protrusion of the spunbond nonwoven fabric.
(x) The above steps (vii) to (ix) are carried out on one side and the other side of the spunbonded nonwoven fabric, respectively, and the angles obtained are designated as R1 and R2 (R1<R2).
In the present invention, the MD direction refers to the sheet conveying direction during the production of the spunbond nonwoven fabric for powder coating filters, i.e., the winding direction of the nonwoven fabric roll, and the CD direction refers to the direction perpendicular to the sheet conveying direction, i.e., the winding direction of the nonwoven fabric roll. If the spunbond nonwoven fabric is not in a rolled state due to being cut, for example, the MD direction and CD direction are determined by the following procedure.
(a) Within the plane of the spunbond nonwoven fabric, an arbitrary direction is determined, and a test piece 38.1 mm long and 25.4 mm wide is taken along that direction.
(b) Similarly, test pieces measuring 38.1 mm in length and 25.4 mm in width are taken in directions rotated 30 degrees, 60 degrees, and 90 degrees from the direction in which the test piece was taken.
(c) For the test pieces in each direction, the bending resistance of each test piece is measured based on the method for measuring the bending resistance of a spunbond nonwoven fabric described below.
(d) The direction in which the measured value is highest is defined as the MD direction of the spunbond nonwoven fabric, and the direction perpendicular to this is defined as the CD direction.

The basis weight of the spunbond nonwoven fabric in the present invention is preferably in the range of 150 to 300 g/ ^m2 . If the basis weight is 150 g/ ^m2 or more, the rigidity required for pleats can be obtained. Furthermore, if the basis weight is 300 g/m2 or ^less , an increase in pressure loss can be suppressed, and this is also a preferred embodiment from the viewpoint of cost. A more preferred basis weight range is 150 to 260 g/ ^m2 , and even more preferably 180 to 230 g/ ^m2 .

The basis weight referred to here is determined by taking three samples measuring 50 cm in length x 50 cm in width, measuring the mass of each, converting the average value (g) obtained into the mass per unit area (1 ^m2 ), and rounding off to the first decimal place.

The CV value of the basis weight of the spunbonded nonwoven fabric of the present invention is 5% or less. It is preferably 4.5% or less, and more preferably 4% or less, since the nonwoven fabric can be made dense with improved uniformity of the nonwoven fabric, which improves the collection performance and makes it easier to obtain a satisfactory filter life. On the other hand, in order to ensure a certain amount of air permeability of the spunbonded nonwoven fabric and reduce pressure loss to extend the filter life, it is more preferable that the CV value of the basis weight is 1% or more.
In the present invention, the basis weight CV value (%) of the spunbond nonwoven fabric is determined as follows.
(i) A total of 100 small pieces of 5 cm x 5 cm are taken from the spunbond nonwoven fabric.
(ii) The mass (g) of each small piece is measured and converted into a mass per unit area (1 m ² ).
(iii) The average value (W _ave ) and standard deviation (W _sdv ) of the conversion results in (ii) are calculated.
(iv) Based on the results of (i) to (iii), calculate the basis weight CV value (%) using the following formula, and round off to one decimal place.
Weight CV value (%) = W _{sdv /} W _ave × 100

The thickness of the spunbond nonwoven fabric in the present invention is preferably 0.50 mm or more and 0.80 mm or less, and more preferably 0.51 mm or more and 0.78 mm or less. By making the thickness 0.50 mm or more, the rigidity can be improved and the nonwoven fabric can be made suitable for use as a filter. In addition, by making the thickness 0.80 mm or less, the spunbond nonwoven fabric can be made excellent in handleability and processability as a filter.

In the present invention, the thickness (mm) of the spunbond nonwoven fabric is determined by the following method.
(i) Using a thickness meter (for example, "TECLOCK" (registered trademark) SM-114 manufactured by TECLOCK Corporation), the thickness of the nonwoven fabric is measured at 10 equally spaced points in the CD direction.
(ii) The arithmetic mean value is rounded off to two decimal places to obtain the thickness (mm) of the nonwoven fabric.

The apparent density of the spunbonded nonwoven fabric in the present invention is preferably 0.25 g/ ^cm3 or more and 0.40 g/ ^cm3 or less. When the apparent density is 0.25 g/ ^cm3 or more and 0.40 g/cm3 or ^less , the spunbonded nonwoven fabric has a dense structure, which makes it difficult for dust to enter the inside, and has excellent dust brushing properties. A more preferable apparent density range is 0.26 g/ ^cm3 or more and 0.38 g/ ^cm3 or less.

In the present invention, the apparent density (g/cm ³ ) of the spunbond nonwoven fabric is calculated from the basis weight and thickness of the spunbond nonwoven fabric using the following formula, and rounded off to two decimal places.
Apparent density (g/cm ³ )=weight per unit area (g/m ² )/thickness (mm)/1000

The air permeability of the spunbond nonwoven fabric in the present invention is preferably 10 ( ^cm3 /( ^cm2 ·sec)) or more and 130 ( ^cm3 /( ^cm2 ·sec)) or less. When the air permeability is 10 ( ^cm3 /( ^cm2 ·sec)) or more, preferably 13 ( ^cm3 /( ^cm2 ·sec)) or more, an increase in pressure loss can be suppressed. Furthermore, when the air permeability is 130 ( ^cm3 /( ^cm2 ·sec)) or less, preferably 105 ( ^cm3 /( ^cm2 ·sec)) or less, dust is less likely to remain inside, and the filter has good collection performance.

In the present invention, the air permeability ( ^cm3 /( ^cm2 ·sec)) of a spunbond nonwoven fabric is determined based on JIS L1913:2010 "Testing methods for general nonwoven fabrics" 6.8 "Air permeability (JIS method)" 6.8.1 "Fragile method" as follows.
(i) Ten test pieces measuring 150 mm length x 150 mm width are taken at equal intervals in the CD direction of the spunbond nonwoven fabric.
(ii) After attaching a test specimen to one end of the cylinder of the testing machine, adjust the suction fan and air hole so that the inclined barometer indicates a pressure of 125 Pa using the lower limit resistor, and measure the pressure indicated by the vertical barometer at that time.
(iii) From the measured pressure and the type of air hole used, the amount of air passing through the test piece (cm ³ /(cm ² ·sec)) is calculated using a conversion table provided with the tester.
(iv) The arithmetic mean value of the air permeabilities of the 10 test pieces obtained is rounded off to one decimal place to calculate the air permeability (cm ³ /(cm ² ·sec)) of the spunbond nonwoven fabric.

The spunbond nonwoven fabric of the present invention has a bending resistance of 40 mN or more and 80 mN or less in the MD direction of the nonwoven fabric. If the bending resistance is 40 mN or more, more preferably 45 mN or more, and even more preferably 50 mN or more, the strength and shape retention of the nonwoven fabric can be maintained while pleating. On the other hand, if the bending resistance is 80 mN or less, more preferably 75 mN or less, and even more preferably 70 mN or less, the folding resistance during pleating is reduced, and the pleats have a sharp peak-valley shape.

The bending resistance in the present invention is a value obtained as follows in accordance with JIS L1913:2010 “General nonwoven fabric testing methods” 6.7 “Bending resistance (JIS method and ISO method)” 6.7.4 “Gurley method (JIS method)”.
(i) Test pieces having a length of 38.1 mm (effective sample length L = 25.4 mm) and a width d = 25.4 mm are taken from any five points on the sample. Here, in the present invention, the longitudinal direction of the nonwoven fabric is defined as the warp direction of the sample.
(ii) Each sampled test piece is attached to a chuck and the chuck is fixed so that it is aligned with the 1-1/2" (1.5 inches = 38.1 mm) scale on the movable arm A. In this case, 1/2" (0.5 inches = 12.7 mm) of the sample length is applied to the chuck by 1/4" (0.25 inches = 6.35 mm), and 1/4" (0.25 inches = 6.35 mm) is applied to the tip of the pendulum at the free end of the sample, so the effective sample length L for measurement is the test piece length minus 1/2" (0.5 inches = 12.7 mm).
(iii) Next, attach suitable weights _Wa , _Wb , _Wc (g) to the weight mounting holes a, b, c (mm) below the fulcrum of pendulum B, rotate movable arm A at a constant speed, and read the scale RG (mgf) when the test piece leaves pendulum B. Read the scale to one decimal place. The weights attached to the weight mounting holes can be selected as appropriate, but it is preferable to set the scale RG to be 4 to 6.
(iv) Measurements are performed on five test pieces, five times on each side, for a total of 50 times.
(v) The bending resistance value was calculated from the obtained RG scale value by using the following formula (3), rounding off to one decimal place. The average value of 50 measurements was rounded off to one decimal place to calculate the bending resistance in the MD direction.

As described above, the spunbond nonwoven fabric of the present invention has a good balance between dust collection performance and breathability, and is excellent in rigidity and pleat processability, and therefore can be suitably used as a filter material for pleated filters in dust collectors and pleated filters in dust collectors. In particular, the nonwoven fabric alone can be suitably used as a filter material for pleated filters in high-volume pulse jet type dust collectors and filters for high-volume pulse jet type dust collectors, which require dust collection under high airflows of more than 300 L/min and pleat shape retention that can withstand repeated backwashing. Such filter material for pleated filters in dust collectors can be obtained, for example, by forming the spunbond nonwoven fabric into a pleated shape.

Figure 2 is a schematic perspective view showing an example of a filter material for a pleated filter of a dust collector according to the present invention. The filter material for a pleated filter of a dust collector 1 shown in Figure 2 has peaks 2 and valleys 3 formed by folding back a spunbond nonwoven fabric. When determining the MD and CD directions from a filter material for a pleated filter of a dust collector that has been pleated, in the case of the filter material for a pleated filter of a dust collector 1 as exemplified in Figure 2, the direction parallel to the ridge of the peaks 2 (broken arrow 5) is the CD direction, and the direction perpendicular to the CD direction (broken arrow 4) is the MD direction.

This filter material for pleated filters can be made into a cylindrical filter, in which the upper and lower ends of the filter material are fixed to the cylinder after the entire filter material is shaped into a cylinder, or into a panel filter, in which the ends of the filter material for pleated filters are fixed to the inner wall of a rectangular or round frame made of a metal material or a polymer resin material.

The pulse jet type dust collector of the present invention uses the pleated filter for dust collectors described above, and is a high-volume pulse jet type dust collector that performs dust capture and repeated backwashing under a high air volume of more than 300 L/min. In this high-volume pulse jet type dust collector, the dust collector filter described above is used in an atmosphere in which the flow rate per dust collector filter is 3.0 L/min or more and 5.0 L/min or less, and the pressure of the processing air applied to each dust collector filter is 0.5 MPa or more and 0.7 MPa or less.

The pulse jet type dust collector of the present invention is equipped with at least one dust collector filter that filters the dust collected from the equipment to be collected, and is equipped with a pulse jet mechanism that injects compressed air in a pulsed manner onto the inner surface of the dust collector filter to remove dust adhering to the outer surface of the filter. This pulse jet mechanism may be an online pulse type mechanism that can operate while the dust collector blower motor is operating, or an offline pulse type mechanism that can operate while dust collection is interrupted.

Next, the spunbond nonwoven fabric of the present invention will be specifically described based on examples. However, the present invention is not limited to these examples.

(Measurement method)
The respective characteristic values in the following examples were measured by the following methods. However, in the measurement of each physical property, unless otherwise specified, the measurement was carried out based on the above-mentioned method.

(1) Melting point of polyester (℃)
A differential scanning calorimeter, "DSC-2 type" manufactured by PerkinElmer Japan Co., Ltd., was used for the measurement under the conditions of a heating rate of 20°C/min and a measurement temperature range of 30°C to 300°C, and the temperature giving an extreme value in the obtained melting endothermic curve was taken as the melting point of the thermoplastic resin. In addition, for resins whose melting endothermic curves did not show an extreme value in the differential scanning calorimeter, the resin was heated on a hot plate, and the temperature at which the resin melted under a microscope was taken as the melting point.

(2) Intrinsic Viscosity (IV) of Polyester
The intrinsic viscosity (IV) of the polyester was measured by the following method.
8 g of a sample was dissolved in 100 mL of orthochlorophenol, and the relative viscosity _ηr was calculated at 25° C. using an Ostwald viscometer according to the following formula:
η _r = η/η ₀ = (t×d)/(t ₀ ×d ₀ )
(Here, η represents the viscosity of the polymer solution, η ₀ represents the viscosity of orthochlorophenol, t represents the drop time of the solution (seconds), d represents the density of the solution (g/cm ³ ), t ₀ represents the drop time of orthochlorophenol (seconds), and d ₀ represents the density of orthochlorophenol (g/cm ³ ).)
Next, the intrinsic viscosity (IV) was calculated from the relative viscosity _ηr according to the following formula.
Intrinsic viscosity (IV) = 0.0242η _r +0.2634

(3) Basis weight (g/m ² ) and basis weight CV value (%) of spunbond nonwoven fabric
The basis weight and basis weight CV value of the spunbond nonwoven fabric were calculated by the above-mentioned method.

(4) Thickness of spunbond nonwoven fabric (mm)
The thickness of the spunbond nonwoven fabric was measured and calculated by the above-mentioned method using a thickness gauge "TECLOCK" (registered trademark) SM-114 manufactured by TECLOCK Corporation.

(5) Apparent density of spunbond nonwoven fabric (g/cm ³ )
The apparent density of the spunbond nonwoven fabric was calculated by the method described above from the basis weight of the spunbond nonwoven fabric obtained in "(3) Basis weight (g/ ^m2 ) and basis weight CV value (%) of the spunbond nonwoven fabric" and the thickness of the spunbond nonwoven fabric obtained in "(4) Thickness of the spunbond nonwoven fabric (mm)".

(6) Bending resistance (mN) of spunbond nonwoven fabric
The bending resistance of the spunbond nonwoven fabric was measured and calculated by the above-mentioned method using a Gurley flexibility tester "GAS-10" manufactured by Daiei Seiki Seisakusho Co., Ltd.

(7) Angle (°) of the curve from the concave portion to the convex portion of the fused portion of the spunbond nonwoven fabric
The scanning electron microscope used was a VHX-D500 manufactured by Keyence Corporation, and measurements and calculations were performed according to the above-mentioned methods.

(8) Fused area ratio (%) of spunbonded nonwoven fabric
The fusion area ratio of the spunbonded nonwoven fabric was measured using a digital microscope "VHX-5000" manufactured by Keyence Corporation, and was measured and calculated by the above-mentioned method.

(9) Pleating Processability of Spunbond Nonwoven Fabric A sample having a width of 50 cm and a length of 1 m was pleated at a pitch of 3 cm using a rotary pleating machine, and evaluated according to the following criteria.
A: The pleats are sharp and uniform, and no meandering can be seen in the sheet. B: The pleats are slightly uneven, and slight meandering can be seen in the sheet. C: The pleats are uneven, and meandering can be seen in the sheet.

(10) Air permeability of spunbond nonwoven fabric ( ^cm3 /( ^cm2 ·sec))
The air permeability of the spunbond nonwoven fabric was measured using a breathability tester "FX3300-III" manufactured by Textest, Switzerland.

(11) Collection performance of spunbond nonwoven fabric (%)
FIG. 3 is a diagram for explaining the configuration of a test system for carrying out a collection performance test according to an embodiment of the present invention. The test system 6 shown in FIG. 3 includes a sample holder 7 for setting a test sample M, a flowmeter 8, a flow rate control valve 9, a blower 10, a dust supply device 11, a changeover cock 12, and a particle counter 13. The dust supply device 11, the flowmeter 8, the flow rate control valve 9, the blower 10, and the dust supply device 11 are connected to the sample holder 7. The flowmeter 8 is connected to the blower 10 via the flow rate control valve 9. Dust is supplied from the dust supply device 11 to the sample holder 7 by the intake of the blower 10. The particle counter 13 is connected to the sample holder 7, and the number of dust particles on the upstream side and the downstream side of the test sample M can be measured via the changeover cock 12. First, three samples of 15 cm×15 cm are taken from any part of the nonwoven fabric, and the taken test sample M is set in the sample holder 7. The evaluation area of the test sample was 115 ^cm2 . In measuring the collection performance, a 10 wt% solution of polystyrene 0.309U (manufactured by Nacalai Tesque, Inc.) was diluted 200 times with distilled water and filled into the dust supply device 11. The air volume was adjusted with the flow control valve 9 so that the filter passing speed was 3.0 m/min, the dust concentration was stabilized in the range of 20,000 to 70,000 particles/(2.83 ^{×10 −4} m ³ (0.01 ft ³ )), and the number of dust particles upstream and downstream of the test sample M was measured with a particle counter 13 (manufactured by Rion Co., Ltd., KC-01D) for dust particle sizes in the range of 0.3 to 0.5 μm. The collected values were substituted into the following calculation formula, and the obtained value was rounded off to the nearest tenth to obtain the collection performance (%).
Collection performance (%) = [1-(D1/D2)] x 100
Here, D1 is the number of dust particles downstream (total of three measurements), and D2 is the number of dust particles upstream (total of three measurements).

(11) Dust Removability of Spunbond Nonwoven Fabric Figure 4 is a diagram for explaining the configuration of a test system for carrying out a dust removal property test according to an embodiment of the present invention. The same components as those in Figure 3 are given the same reference numerals. The test system 14 shown in Figure 4 includes a sample holder 7 for setting a test sample M, a flowmeter 8, a flow control valve 9, a blower 10, a dust supply device 11, a pulse jet device 15, and a pressure gauge 16. The flowmeter 8, the dust supply device 11, the pulse jet device 15, and the pressure gauge 16 are connected to the sample holder 7. The flowmeter 8 is connected to the blower 10 via the flow control valve 9. Dust is supplied from the dust supply device 11 to the sample holder 7 by the intake of the blower 10. The pulse jet device 15 ejects compressed air to remove dust adhering to the test sample M. First, three samples of 15 cm x 15 cm are taken from any part of the nonwoven fabric, and the taken test sample M is set in the sample holder 7. The evaluation area of the test sample is 115 ^cm2 . At this time, a pressure gauge 16 is connected to the sample holder 7 so that the pressure loss of the test sample M can be measured. In the test of the brushability, 15 types of standard powders specified by JIS are supplied from the dust supply device 11 so as to have a concentration of 205 g/ ^m3 , and the air volume is adjusted by the flow control valve 9 so that the filter passing speed is 1.5 m/min, and the dust is continuously supplied at a constant concentration. After the pressure loss of the test sample M reaches 1500 Pa, 0.5 MPa compressed air is sprayed from the pulse jet device 15 for 0.1 sec to brush off the dust attached to the test sample M.
The operation time (hr) required for the number of brush-offs to reach 200 was measured, and the operation time (hr) was calculated by averaging the results of three tests and rounding off the average value to the nearest 1 digit.

(Resin used)
The resins used in the examples and comparative examples are as follows.
Polyester resin A: polyethylene terephthalate (PET) dried to a moisture content of 50 ppm by mass or less, having an intrinsic viscosity (IV) of 0.66 and a melting point of 260°C.
Polyester resin B: Copolymerized polyethylene terephthalate (CO-PET) dried to a moisture content of 50 mass ppm or less, having an intrinsic viscosity (IV) of 0.68, an isophthalic acid copolymerization rate of 11 mol%, and a melting point of 230° C.

Example 1
The polyester resin A and the polyester resin B were melted at temperatures of 295°C and 280°C, respectively. Then, the polyester resin A was used as the core component and the polyester resin B was used as the sheath component, and the spinneret temperature was 300°C, and the core:sheath mass ratio was 80:20. The core-sheath type filaments were melt-spun at a discharge rate set so that the average single fiber diameter was 17 μm, and the spinneret temperature was 300°C. A high-speed drawing of about 5000 m/min was continuously performed with air pressure. Subsequently, the filaments were sprayed and opened with air pressure, and deposited on a moving net to form a nonwoven fabric web, which was fused by a pair of heated embossing rolls under conditions of a linear pressure of 60 kg/cm, a roll surface temperature of 200°C, and a fusion area ratio of 10%, to obtain nonwoven fabrics with basis weights of 150, 200, and 250 g/ ^m2 , respectively. The configuration and results of Example 1 are shown in Table 1.

Example 2
The discharge rate was set so that the average single fiber diameter of the core-sheath filaments was 24 μm, and the fusion conditions of the heated embossing roll were a linear pressure of 70 kg/cm, a roll surface temperature of 205° C., and a fused area ratio of 20%, with all other conditions being the same as in Example 1, to obtain nonwoven fabrics with basis weights of 150, 200, and 250 g/ ^m2 , respectively. The configuration and results of Example 2 are shown in Table 1.

Example 3
The amount of polyester resin A discharged was adjusted so that the average single fiber diameter was 17 μm, and a single component filament was obtained. The amount of polyester resin B discharged was adjusted so that the average single fiber diameter was 17 μm, and a single component filament was obtained. The single component filament made of polyester resin A and the single component filament made of polyester resin B were mixed and spun, and continuously pulled at a high speed of about 5000 m/min by air pressure. The filament was then sprayed, opened, and deposited on a moving net to form a nonwoven web, which was fused by a pair of heated embossing rolls under conditions of a linear pressure of 60 kg/cm, a roll surface temperature of 200° C., and a fusion area ratio of 18%, to obtain mixed fiber nonwoven fabrics made of single component filaments made of polyester resin A and single component filaments made of polyester resin B with basis weights of 150 g/m ² , 200 g/m ² , and 250 g/m ² . The configuration and results of Example 3 are shown in Table 1.

The results of evaluation of the bending resistance, basis weight CV value, angle of the curve from the fused portion to the non-fused portion, and pleatability of the nonwoven fabrics described in Examples 1 to 3 are shown in Table 1. As is clear from Table 1, all of the nonwoven fabrics of Examples 1 to 3 had bending resistance of 25 mN or more, basis weight CV value of 5% or less, and also had good pleatability and dust removal properties, and had satisfactory properties as a filter substrate.

(Comparative Example 1)
The discharge rate was set so that the average single fiber diameter of the core-sheath filaments was 27 μm, and the fusion conditions of the heated embossing roll were a linear pressure of 70 kg/cm, a roll surface temperature of 205° C., and a fusion area ratio of 23%, with all other conditions being the same as those of Example 1, to obtain nonwoven fabrics with basis weights of 150, 200, and 250 g/m ² , respectively. The evaluation results of various properties of this nonwoven fabric are shown in Table 1. As is clear from Table 1, this nonwoven fabric had slightly uneven pleat processability at a basis weight of 150 g/m ² , and dust brushing off properties were insufficient at all basis weights. In addition, since the thickness of the nonwoven fabric was low and the apparent density was high, when it was used as a filter substrate, the air permeability was low, and pressure increase occurred due to dust adhesion over time, so the collection performance was also unfavorable.

(Comparative Example 2)
The polyester resin A was discharged at a rate adjusted so that the average single fiber diameter was 11 μm, and the polyester resin B was discharged at a rate adjusted so that the average single fiber diameter was 11 μm, and each single component filament was obtained, and the filaments were mixed to obtain a nonwoven fabric. The other conditions were all the same as those in Example 3, and nonwoven fabrics with basis weights of 150, 200, and 250 g/m ² were obtained, respectively. The evaluation results of various properties of this nonwoven fabric are shown in Table 1. As is clear from Table 1, this nonwoven fabric had uneven pleat processability at a basis weight of 150 g/m ² , and the sheet was meandering, and even at 200 g/m ² , the pleat processability was somewhat uneven, and the dust brushing off property was insufficient at all basis weights. In addition, since the thickness of the nonwoven fabric was low and the apparent density was high, when it was used as a filter substrate, the air permeability was low, pressure increased due to the adhesion of dust over time, the collection performance was inferior, and the pleat processability was also inferior, which was undesirable.

1 Filter material for pleated filter of dust collector 2 Peak portion 3 Valley portion 4 Arrow indicating MD direction (broken line arrow)
5 Arrow indicating CD direction (dashed arrow)
Reference Signs List 6, 14 Test system 7 Sample holder 8 Flow meter 9 Flow rate control valve 10 Blower 11 Dust supply device 12 Switching cock 13 Particle counter 15 Pulse jet device 16 Pressure gauge 101 Fused portion 102 Non-fused portion M Test sample

Claims (6)

It is composed of thermoplastic continuous filaments consisting of a high melting point component and a low melting point component,
The thermoplastic continuous filament has an average single fiber diameter of 12 μm or more and 26 μm or less,
The sheet has a fused portion that is partially fused and a non-fused portion that is not fused,
The basis weight CV value is 5% or less,
The ratio of the area of the fused portion is 5% or more and 20% or less,
The apparent density of the spunbond nonwoven fabric is 0.25 g/cm3 ^or more and 0.40 g/cm3 ^or less,
A spunbond nonwoven fabric, wherein angles R1 and R2 formed by boundary surfaces between the fused portion and the non -fused portion are different from each other , angle R1 being 15° or more and 31° or less, and angle R2 being 45° or more and 75° or less . The spunbond nonwoven fabric according to claim 1, wherein the thermoplastic continuous filaments are made of polyethylene terephthalate as the high melting point component and copolymer polyester or polybutylene terephthalate as the low melting point component. 3. The spunbonded nonwoven fabric according to claim 1 , wherein the fused portion is formed by fusion bonding from both the top and bottom sides of the spunbonded nonwoven fabric. A filter material for a pleated filter of a dust collector, comprising the spunbond nonwoven fabric according to any one of claims 1 to 3 . A pleated filter for a dust collector, comprising the filter material for a pleated filter for a dust collector according to claim 4 . A high volume pulse jet type dust collector using the pleated filter according to claim 5 .

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