JP2021098195A - Spun-bonded nonwoven fabric for filter, filter medium for powder coating filter, and powder coating filter - Google Patents

Abstract

To provide spun-bonded nonwoven fabric for a filter which has excellent balance between powder dust collecting performance and permeability, has high rigidity and is excellent in fluff resistance.SOLUTION: Spun-bonded nonwoven fabric for a filter is composed of a thermoplastic continuous filament composed of a high melting point component and a low melting component, and is partially fused. Bending resistance in an MD direction is 15 mN or more and 30 mN or less. A ratio of reflected light average luminance (S1) of a fused part in a cross section represented by the following formula (1) to average luminance (S2) of a non-fused part is 0.02 or more and less than 1.0, and a ventilation amount (q) (cm3/(cm2 sec))/(g/m2) per unit basis weight is 0.05 or more and 0.5 or less.SELECTED DRAWING: None

Description

The present invention relates to a spunbonded nonwoven fabric for a filter having excellent rigidity and breathability, a filter medium for a powder coating filter, and a powder coating filter.

Powder coating booths such as automobile bodies have a structure in which air is taken in from the ceiling surface of the powder coating booth and air inside the booth is exhausted from the floor surface of the powder coating booth. It is used by enclosing the work area where painting is done so as not to adversely affect it. Generally, the air supplied to the powder coating booth is the air taken in from the outside air, and the air supplied to the powder coating booth completely removes the dust and dirt contained in the air taken in from the outside air. It is necessary. If there is any dust or dirt in the air supplied to the powder coating booth, it will adhere to the coating surface and cause deterioration of coating quality. Therefore, cleaning the supply air is extremely important, and a powder coating filter is used in the powder coating booth to clean the supply air.

Non-woven fabric has been proposed as a material for such a powder coating booth filter, and in particular, a long-fiber non-woven fabric in which continuous long fibers are partially fused in order to prevent fibers and dust from falling off from the air outflow surface. Is pleated. The spunbonded non-woven fabric for filters used in powder coating booths requires breathability to process a large amount of air in a short time and pleating workability in order to increase the specific surface area as a filter. Spun-bonded non-woven fabric is used. For example, Patent Documents 1 and 2 disclose a non-woven fabric in which thermoplastic continuous filaments are previously heat-pressed with a pair of flat rolls and then partially fused with a pair of engraved embossed rolls. Further, Patent Document 3 includes a non-woven fabric in which a thermoplastic continuous filament having a high melting point component and a thermoplastic continuous filament having a low melting point component are mixed, and a non-woven fabric made of a multi-leaf composite fiber composed of a high melting point component and a low melting point component. It is disclosed.

Japanese Patent No. 5422874 Japanese Patent No. 5298803 Japanese Patent No. 4522671

The powder coating filter for spunbond nonwoven processes the air containing dust and dirt of 100-2000 m ³ per minute in a powder coating booth, it is necessary to supply the processing air in the coating booth .. The non-woven fabric for a powder coating filter used in such a powder coating booth needs to have air permeability and rigidity having pleated shape retention for processing a large amount of air in a short time. However, when trying to achieve both breathability and rigidity, a spunbonded non-woven fabric for a powder coating filter having sufficient breathability has not been obtained. That is, when the fusion of the fibers is loosened in order to improve the air permeability, the rigidity of the non-woven fabric is lowered, the pleating processability and the shape retention property are lowered, and the fibers fall off due to the generation of fluff. On the other hand, if the fusion between the fibers is strengthened in order to improve the pleating processability, the shape retention property and the fluff resistance, the opening of the fibers becomes small and the air permeability of the non-woven fabric is lowered.
For example, with the techniques disclosed in Patent Documents 1 and 2, it has been difficult to achieve both sufficient air permeability and pleating workability.

On the other hand, in Patent Document 3, the fusion between fibers is weak, and the rigidity of the non-woven fabric is lowered or fluff is generated due to the breakage of the fused portion during pleating, and the shape of the pleats is formed under high air volume when used as a powder coating filter. Could not be retained, and there were problems such as deterioration of air permeability and shedding of fluff.
Therefore, in view of the above problems, an object of the present invention is a spunbonded non-woven fabric for a filter and a powder coating filter, which have both high rigidity and excellent fluff resistance while achieving a balance between dust collection performance and air permeability. To provide filter media and powder coating filters.

As a result of diligent studies to achieve the above object, the present inventors have obtained the average brightness of reflected light of the fused portion and the specific fused portion obtained from the cross section of the non-woven fabric made of partially fused thermoplastic continuous filaments. It was found that a non-woven fabric within the specified range can be used to obtain a spunbonded non-woven fabric for filters that has sufficient rigidity and fluff resistance for pleating while achieving a balance between dust collection performance and breathability. It was.
The present invention has been completed based on these findings, and the following inventions are provided according to the present invention.

That is, the spunbonded nonwoven fabric for filters of the present invention is a spunbonded nonwoven fabric for powder coating, which is composed of a thermoplastic continuous filament composed of a high melting point component and a low melting point component and is partially fused. The rigidity in the direction is 15 mN or more and 30 mN or less, and the ratio of the average brightness of reflected light (S1) of the fused portion and the average brightness of reflected light (S2) of the non-woven fabric in the cross section represented by the following formula (1). Is 0.20 or more and less than 1.00, and the air flow rate (q) (cm ³ / (cm ² · sec)) / (g / m ² ) per unit is 0.05 or more and 0.50 or less. Is.
R = 1-S2 / S1 ... (1)

According to a preferred embodiment of the spunbonded non-woven fabric for a filter of the present invention, the basis weight CV value is 5.0% or less.
According to a preferred embodiment of the spunbonded non-woven fabric for a filter of the present invention, the ratio of the area of the fused portion is 5% or more and 20% or less.
According to a preferred embodiment of the spunbonded nonwoven fabric for filters of the present invention, the average single fiber diameter of the thermoplastic continuous filament is 12.0 μm or more and 26.0 μm or less.
The spunbonded nonwoven fabric for filters of the present invention is a spunbonded nonwoven fabric for powder coating filters.
The spunbonded non-woven fabric for a filter of the present invention is used as a filter medium for a powder coating filter.
The filter medium for a powder coating filter of the present invention is used for a powder coating filter.

According to the present invention, a spunbonded non-woven fabric for a filter, a filter medium for a powder coating filter, and a powder coating filter having an excellent balance between dust collection performance and air permeability and excellent pleating workability, rigidity, and fluff resistance can be obtained. can get.

FIG. 1 is a schematic perspective view illustrating the filter medium for a filter of the present invention. FIG. 2 is a cross-sectional photograph illustrating the structure of the spunbonded nonwoven fabric for a filter according to the present invention. FIG. 3 is a diagram for explaining a configuration of a test system for carrying out a collection performance test according to an embodiment of the present invention.

The spunbonded non-woven fabric for a filter of the present invention is a spunbonded non-woven fabric for a filter composed of a thermoplastic continuous filament composed of a high melting point component and a low melting point component and partially fused, and is rigid and soft in the MD direction. The degree is 15 mN or more and 30 mN or less, and the ratio of the average brightness of reflected light (S1) of the fused portion and the average brightness of reflected light (S2) of the non-woven fabric in the cross section represented by the following formula (1) is 0. It is 02 or more and less than 1.00, and the air flow rate (q) (cm ³ / (cm ² · sec)) / (g / m ² ) per unit is 0.05 or more and 0.50 or less.
R = 1-S2 / S1 ... (1)
Hereinafter, each constituent requirement of the spunbonded nonwoven fabric for a filter of the present invention will be described in detail.

(Thermoplastic continuous filament)
Polyester is particularly preferably used as the thermoplastic resin which is a raw material of the thermoplastic continuous filament constituting the spunbonded nonwoven fabric for a filter of the present invention. Polyester is a polymer polymer having an acid component and an alcohol component as monomers. As the acid component, aromatic carboxylic acids such as phthalic acid (ortho), isophthalic acid and terephthalic acid, aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and alicyclic dicarboxylic acids such as cyclohexanecarboxylic acid are used. be able to. Further, as the alcohol component, ethylene glycol, diethylene glycol, polyethylene glycol and the like can be used.

Examples of the polyester include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate, polylactic acid and polybutylene succinate. As the polyester used as the high melting point polymer described later, PET having a high melting point, excellent heat resistance, and excellent rigidity is most preferably used.

These polyester raw materials include crystal nucleating agents, matting agents, pigments, fungicides, antibacterial agents, flame retardants, metal oxides, aliphatic bisamides and / or aliphatic monoamides, as long as the effects of the present invention are not impaired. And additives such as hydrophilic agents can be added. Among them, metal oxides such as titanium oxide improve spinnability by reducing surface friction of fibers and preventing fusion between fibers, and also increase thermal conductivity during fusion molding by a thermal roll of a non-woven fabric. This has the effect of improving the meltability of the non-woven fabric. In addition, aliphatic bisamides such as ethylene bisstearic acid amide and / or alkyl-substituted aliphatic monoamides have the effect of enhancing the releasability between the thermal roll and the non-woven fabric web and improving the transportability.

The thermoplastic continuous filament used in the present invention comprises a high melting point component and a low melting point component. The thermoplastic continuous filament is a polyester which is a low melting point component having a melting point of 10 ° C. or more and 140 ° C. or less lower than the melting point of the polyester-based high melting point polymer around the polyester-based high melting point polymer which is a high melting point component. It is preferable that the filament is a composite filament in which a low melting point polymer is arranged. By doing so, 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 the filter has excellent mechanical strength. It can withstand dust treatment under high air volume.

The melting point of the polyester-based low melting point polymer in the present invention is 10 ° C. or higher, more preferably 20 ° C. or higher, still more preferably 30 ° C. or higher, so that the melting point is desired. Wearability can be ensured. On the other hand, the heat resistance of the spunbonded non-woven fabric for a filter is obtained by lowering the melting point of the polyester-based low melting point polymer to 140 ° C. or lower, more preferably 120 ° C. or lower, and further preferably 100 ° C. or lower than the melting point of the polyester-based high melting point polymer. Can be prevented from decreasing.

The melting point of the polyester-based high melting point polymer in the present invention is preferably in the range of 200 ° C. or higher and 320 ° C. or lower. By setting the melting point of the polyester-based high melting point polymer to preferably 200 ° C. or higher, more preferably 210 ° C. or higher, and further preferably 220 ° C. or higher, a powder coating filter having 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 lower, more preferably 300 ° C. or lower, and further preferably 280 ° C. or lower, a large amount of thermal energy for melting during the production of the non-woven fabric is consumed for production. It is possible to suppress the deterioration of the sex.

On the other hand, 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 further preferably 180 ° C. or higher, a step of applying heat during pleating filter manufacturing, such as heat setting during pleating, is performed. Excellent morphological stability even after passing. 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 powder coating filter having excellent meltability during the production of a non-woven fabric and excellent mechanical strength can be obtained. Can be done.

In the present invention, the melting point of the thermoplastic resin is a differential scanning calorimeter (for example, "DSC-2" type manufactured by Perkin Elmer Co., Ltd.), a temperature rise rate of 20 ° C./min, and a measurement temperature range of 30 ° C. to 300 ° C. The melting point of the thermoplastic resin is defined as the temperature at which an extreme value is given in the obtained melting heat absorption curve measured under the condition of ° C. Further, for a resin whose melting endothermic curve does not show an extreme value in a differential scanning calorimeter, it is heated on a hot plate and the temperature at which the resin is melted by microscopic observation is defined as the melting point.

When the thermoplastic resin is polyester, a combination of a pair of polyester-based high-melting point polymer and polyester-based low-melting point polymer (hereinafter, may be described in the order of polyester-based high-melting point polymer / polyester-based low-melting point polymer). Examples thereof include combinations of PET / PBT, PET / PTT, PET / polylactic acid, PET / copolymerized PET, and the like. Among these, the combination of PET / copolymerized PET is excellent in spinnability. Is preferably used. Further, as the copolymerization component of the copolymerized PET, isophthalic acid copolymerized PET is preferably used because it is particularly excellent in spinnability.

Examples of the composite form of the composite filament include a concentric sheath type, an eccentric sheath type, and a sea island type. Among them, the concentric sheath type can be used because the filaments can be fused uniformly and firmly. Is preferable. Further, examples of the cross-sectional shape of the composite filament include a circular cross section, a flat cross section, a polygonal cross section, a multi-leaf cross section, and a hollow cross section. Among them, it is preferable to use a filament having a circular cross section as the cross-sectional shape.

By the way, in the form of the composite filament, for example, there is a method of mixing a fiber made of a polyester-based high melting point polymer and a fiber made of a polyester-based low melting point polymer, but in the case of the method of mixing, the fiber is uniform. Fusing is difficult. For example, where fibers made of a polyester-based refractory polymer are densely packed, the fusion is weakened, and the mechanical strength and rigidity are inferior, which makes it unsuitable as a pleated filter. On the other hand, there is also a method of applying the low melting point polymer to the fiber made of the polyester-based high melting point polymer by dipping or spraying, but it is difficult to uniformly apply the low melting point polymer in the surface layer and the thickness direction, and the mechanical strength and rigidity are increased. It is inferior and unfavorable as a pleated filter.

The content ratio of the polyester-based high melting point polymer and the polyester-based low melting point polymer in the thermoplastic continuous filament is preferably in the range of 90: 10 to 60:40 in terms of mass ratio, and is preferably in the range of 85: 15 to 70: A range of 30 is a more preferred embodiment. By setting the polyester-based refractory polymer to 60% by mass or more and 90% by mass or less, the rigidity and heat resistance of the spunbonded non-woven fabric can be improved. On the other hand, when the polyester-based low melting point polymer is 10% by mass or more and 40% by mass or less to form a spunbonded nonwoven fabric by heat fusion and used, the composite filaments constituting the spunbonded nonwoven fabric are firmly fused to each other. It can be worn, has excellent mechanical strength, and can withstand dust collection under high air volume.

The average single fiber diameter of the thermoplastic continuous filament constituting the spunbonded nonwoven fabric for a filter of the present invention is preferably in the range of 12.0 μm or more and 26.0 μm or less. By setting the average single fiber diameter of the thermoplastic continuous filament to 12.0 μm or more, preferably 13.0 μm or more, more preferably 14.0 μm or more, the air permeability of the spunbonded non-woven fabric for a filter is improved and the pressure loss is reduced. Can be made to. It is also possible to reduce the number of yarn breaks when forming the thermoplastic continuous filament and improve the stability during production. On the other hand, by setting the average single fiber diameter of the thermoplastic continuous filament to 26.0 μm or less, preferably 25.0 μm or less, more preferably 24.0 μm or less, the uniformity of the spunbonded non-woven fabric for filtration is improved, and the surface of the non-woven fabric is improved. Can be made dense, and dust can be easily filtered on the surface layer, and the collection performance can be improved.

In the present invention, the average single fiber diameter (μm) of the spunbonded nonwoven fabric for a filter is a value obtained by the following method.
(I) Randomly collect 10 small piece samples from the spunbonded non-woven fabric for the filter.
(Ii) Take a photograph of the surface of the collected small piece sample with a scanning electron microscope or the like capable of measuring the fiber thickness in the range of 500 to 2000 times.
(Iii) A total of 100 fibers, 10 fibers each, are arbitrarily selected from the photographs taken of each small piece sample, and the thickness thereof is measured. The fiber is assumed to have a circular cross section, and the thickness is the fiber diameter.
(Iv) The value calculated by rounding off the second decimal place of those arithmetic mean values is taken as the average single fiber diameter.

(Manufacturing method of spunbonded non-woven fabric for filters)
Next, the spunbonded nonwoven fabric for a filter of the present invention and a method for producing the same will be described. The spunbonded nonwoven fabric for a filter of the present invention is produced by sequentially performing the following steps (a) to (c).
(A) A step of melt-extruding a thermoplastic polymer from a spinneret, and then pulling and drawing the thermoplastic polymer by air soccer to obtain a thermoplastic continuous filament.
(B) A step of forming a fiber web by regulating and depositing a fiber arrangement with a fiber-spreading plate on a net conveyor that moves the obtained filament.
(C) A step of partially fusing the obtained fiber web.
Further details of each of the above steps will be described below.

(A) Thermoplastic continuous filament forming step First, the thermoplastic polymer is melt-extruded from the spinneret. In particular, when a composite filament in which a polyester-based low-melting-melting polymer having a melting point lower than the melting point of the polyester-based high-melting-melting polymer is arranged around a polyester-based high-melting-melting polymer is used as the thermoplastic continuous filament, A polyester-based high-melting point polymer and a polyester-based low-melting-melting polymer are melted at a temperature equal to or higher than the melting point (melting point + 70 ° C.), respectively, and around the polyester-based high-melting-melting polymer to the melting point of the polyester-based high-melting-melting polymer. On the other hand, as a composite filament in which a polyester-based low melting point polymer having a low melting point of 10 ° C. or higher and 140 ° C. or lower is arranged, after spinning from the pores with a spinning mouthpiece having a base temperature of 10 ° C. or higher and (melting point + 70 ° C.) or lower. , The filament with a circular cross section is spun by pulling and stretching at a spinning speed of 4000 m / min or more and 6000 m / min or less by air soccer.

(B) Fiber web forming step The non-woven fabric of the present invention is a so-called spunbonded non-woven fabric for a filter, and the spun thermoplastic continuous filament is sucked by an ejector and sprayed from an open fiber plate having a slit shape at the lower part of the ejector. It has a step of depositing on a moving net conveyor to obtain a fibrous web.
Even when the composite polyester fiber is used, it is important that the spunbonded non-woven fabric for a filter made of the above-mentioned filament (long fiber) is used. By doing so, the rigidity and mechanical strength can be increased as compared with the case of a non-woven fabric made of short fibers composed of discontinuous fibers, which can be preferable as a pleated filter. In the method for producing a spunbonded non-woven fabric for a filter of the present invention, it is also a preferable embodiment to temporarily fuse the fiber webs collected on the net conveyor. For temporary fusion, a method of fusing the collected fiber webs with a pair of flat rolls or installing a flat roll on a net conveyor and fusing between the net conveyor and the flat roll is preferably used. Be done.

The temperature of fusion for tentative fusion is preferably 70 ° C. or higher and 120 ° C. or lower lower than the melting point of the polyester-based low melting point polymer. By setting the temperature in this way, the transportability can be improved without excessively fusing the fibers to each other.
Further, 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, it is possible to impart the mechanical strength required for transporting the fiber web to the next step. By setting the linear pressure for temporary fusion to 70 kg / cm or less, more preferably 60 kg / cm or less, excessive fusion between the fibers can be prevented.

(C) Partial fusion step The spunbonded nonwoven fabric for a filter of the present invention is partially fused, but the method of partial fusion is not particularly limited. The partial fusion step is preferably processed continuously from the web forming step. By continuing the processing from the web forming step, the density of the fused portion can be increased, and a non-woven fabric having a waist strength excellent in pleated formability can be obtained as a spunbonded non-woven fabric for a filter. Fusion by a thermal emboss roll or fusion by a combination of an ultrasonic oscillator and an emboss roll is preferable. In particular, fusion by embossing roll is most preferable from the viewpoint of improving the strength of the non-woven fabric. The temperature of fusion by the thermal embossing roll is preferably 5 ° C. or higher and 60 ° C. or lower lower than the melting point of the polymer having the lowest melting point existing on the fiber surface of the non-woven fabric, and more preferably 10 ° C. or higher and 50 ° C. or lower. Excessive fusion can be prevented by setting the temperature difference of the melting points of the polymer having the lowest melting point existing on the fiber surface of the non-woven fabric by thermal embossing to 5 ° C. or higher, more preferably 10 ° C. or higher. On the other hand, by setting the temperature difference to 60 ° C. or lower, more preferably 50 ° C. or lower, uniform fusion can be performed in the non-woven fabric.
Further, the linear pressure for fusion is preferably 30 kg / cm or more and 90 kg / cm or less. By setting the linear pressure for fusion to 30 kg / cm or more, more preferably 40 kg / cm or more, it is possible to impart the mechanical strength required for pleating processability to the non-woven fabric when used as a spunbonded non-woven fabric for a filter. it can. Excessive fusion can be prevented by setting the linear pressure for fusion to 90 kg / cm or less, more preferably 80 kg / cm or less.

The ratio of the partially fused fused area of the spunbonded nonwoven fabric for filters of the present invention (hereinafter, may be simply referred to as the fused area ratio) is the ratio of the fused portion to the total area of the nonwoven fabric. The preferred range is 5% or more and 20% or less with respect to the total area of the non-woven fabric. When the fused area ratio is 5% or more, more preferably 6% or more, still more preferably 8% or more, sufficient mechanical strength of the non-woven fabric can be obtained, and the surface does not easily fluff. On the other hand, if the fused area ratio is 20% or less, more preferably 19% or less, still more preferably 18% or less, the voids between the fibers are reduced, the pressure loss is increased, and the collection performance may be lowered. Absent.
A digital microscope (for example, "VHX-5000" manufactured by Keyence Co., Ltd.) is used to measure the fused area ratio of the spunbonded non-woven fabric, and the magnification of the microscope is 20 times from any part of the spunbonded non-woven fabric. 100 rectangular frames of 1.0 cm × 1.0 cm parallel to the MD direction and the CD direction of the non-woven fabric were taken, and the area of the fused portion in the rectangular frame was measured for each of the 100 points and the average value was taken. The fused area ratio (%) is calculated by rounding off the first digit after the decimal point as a percentage. If it is not expressed as a percentage, the area (cm ^{2 ) of the fused portion in the rectangular frame is divided by 1.0 cm 2} , which is the area of the rectangular frame, and then the third decimal place is rounded off. The landing area ratio can be calculated.

Here, in the present invention, the MD direction refers to the sheet transport direction at the time of manufacturing the spunbonded non-woven fabric, that is, the winding direction in the non-woven fabric roll, and the CD direction is the sheet transport direction, that is, the winding direction in the non-woven fabric roll. It refers to the direction of vertical intersection. When the spunbonded non-woven fabric is not in the rolled state due to cutting or the like, the MD direction and the CD direction are determined by the following procedure.
(A) In the plane of the spunbonded non-woven fabric, an arbitrary direction is determined, and a test piece having a length of 38.1 mm and a width of 25.4 mm is collected along that direction.
(B) Similarly, a test piece having a length of 38.1 mm and a width of 25.4 mm is collected in the directions rotated by 30, 60, and 90 degrees from the collecting direction.
(C) The rigidity and softness of each test piece is measured based on the method for measuring the rigidity and softness of the spunbonded non-woven fabric described later for the test pieces in each direction.
(D) The direction in which the value obtained by the measurement is the highest is the MD direction of the spunbonded non-woven fabric, and the direction orthogonal to this is the CD direction.
Further, when determining the MD direction and the CD direction from the filter medium for the powder coating filter, in the case of the filter medium for the powder coating filter as illustrated in FIG. 1, the direction 25 parallel to the ridgeline of the mountain portion 22 is set. It is assumed that the CD direction and the direction 24 orthogonal to the CD direction are the MD directions.

The fused portion forms a recess, and the thermoplastic continuous filaments constituting the non-woven fabric are fused by heat and pressure. That is, the portion where the thermoplastic continuous filaments are fused and aggregated as compared with the other portions is the fused portion. When fusion by a thermal emboss roll is adopted as the method of fusion, the portion where the thermoplastic continuous filament is fused and aggregated by the convex portion of the emboss roll becomes the fusion portion. For example, when a roll having a predetermined pattern of unevenness is used only on the upper side or the lower side and a flat roll having no unevenness is used as the other roll, the fused portion is a convex portion of the roll having unevenness and a flat roll. It refers to the portion where the thermoplastic continuous filaments of the non-woven fabric are aggregated by being fused with and. Further, for example, it is composed of a pair of upper rolls and lower rolls in which a plurality of linear grooves arranged in parallel are formed on the surface, and the grooves of the upper roll and the grooves of the lower roll intersect at a certain angle. When an embossed roll provided so as to be used is used, the fused portion means a portion where the thermoplastic continuous filaments of the non-woven fabric are aggregated by being fused by the convex portion of the upper roll and the convex portion of the lower roll. In this case, the portion fused between the upper convex portion and the lower concave portion or the upper concave portion and the lower convex portion is not included in the fusion portion referred to here.

The area of each fused portion ^{is preferably 0.3 mm 2} or more and 5.0 mm ² or less. By setting the thickness to 0.3 mm ² or more, sufficient mechanical strength can be obtained as a spunbonded non-woven fabric for a filter, and fluffing on the surface of the non-woven fabric can be suppressed. When the ^{thickness is 5.0 mm 2} or less, the air permeability can be maintained in addition to the mechanical strength as a spunbonded non-woven fabric for a powder coating filter, and sufficient collection performance can be obtained.

The shape of the fused portion in the spunbonded non-woven fabric for a filter of the present invention is not particularly specified. A roll having a predetermined pattern of unevenness only on the upper side or the lower side is used, and the other rolls are flat rolls without unevenness. It consists of a pair of upper rolls and lower rolls in which a plurality of linear grooves arranged in parallel are formed on the surface, and the groove of the upper roll and the groove of the lower roll intersect at a certain angle. Even when the convex portion of the upper roll and the convex portion of the lower roll are fused, the shape of the fused portion is circular, triangular, quadrangular, parallelogram, etc. It may be oval or rhombic. The arrangement of these fused portions is not particularly specified, and may be regularly arranged at equal intervals, randomly arranged, or a mixture of different shapes. Among them, from the viewpoint of uniformity of the non-woven fabric, it is preferable that the fused portions are arranged at equal intervals. Further, in terms of partial fusion without peeling the non-woven fabric, it is composed of a pair of upper rolls and lower rolls in which a plurality of linear grooves arranged in parallel are formed on the surface, and the grooves of the upper rolls are formed. Using an embossed roll provided so as to intersect with the groove of the lower roll at a certain angle, a parallelogram fusion formed by fusing the convex portion of the upper roll and the convex portion of the lower roll. The wearing part is preferable.

(Spanbond non-woven fabric for filters)
The spunbonded non-woven fabric for a filter of the present invention has a rigidity of 15 mN or more and 30 mN or less in the MD direction of the non-woven fabric. When the rigidity is 15 mN or more, more preferably 17.5 mN or more, and further preferably 20 mN or more, pleating can be performed while maintaining the strength and shape retention of the non-woven fabric. On the other hand, if it is 30 mN or less, more preferably 27.5 mN or less, and further preferably 25 mN or less, the folding resistance during pleating is relaxed, and the pleated mountain valley shape is sharply finished.

The rigidity in the present invention is in accordance with JIS L1913: 2010 "General non-woven fabric test method" 6.7 "Rigidity and softness (JIS method and ISO method)" 6.7.4 "Gare method (JIS method)". , The value obtained by doing as follows.
(I) A test piece having a length of 38.1 mm (effective sample length L = 25.4 mm) and a width d = 25.4 mm is collected from any five points of the sample. Here, in the present invention, the longitudinal direction of the non-woven fabric is the vertical direction of the sample.
(Ii) Attach the collected test pieces to the chucks, and fix the chucks according to the scale 1-1 / 2 "(1.5 inches = 38.1 mm) on the movable arm A. In this case, the sample length is 1 / 2 "(0.5 inch = 12.7 mm) is 1/4" (0.25 inch = 6.35 mm) on the chuck and 1/4 "(0.25 inch) on the tip of the pendulum at the free end of the sample. = 6.35 mm), so the effective sample length L required for measurement is the test piece length minus 1/2 "(0.5 inch = 12.7 mm).
_{(Iii) Next, attach appropriate weights W a} , W _b , W _c (g) from the fulcrum of the pendulum B to the lower weight mounting holes a, b, c (mm), and rotate the movable arm A at a constant speed. Read the scale RG (mgf) when the test piece separates from the pendulum B. Read the scale with the first decimal place. Here, the weight to be attached to the weight mounting hole can be appropriately selected, but it is preferable to set the scale RG to be 4 to 6.
(Iv) The measurement is carried out 5 times on the front and back sides for 5 points of the test piece, for a total of 50 times.
(V) From the obtained scale RG value, the value of rigidity and softness is rounded to the second decimal place using the following formula to obtain each. The value calculated by rounding off the second decimal place from the average value of 50 measurements was taken as the flexibility in the MD direction.

In the spunbonded non-woven fabric for a filter in the present invention, the ratio of the average brightness of reflected light (S1) of the fused portion and the average brightness of reflected light (S2) of the non-fused portion in the cross section represented by the following formula (1) is 0. .Spanbonded non-woven fabric for filters of 20 or more and less than 1.0. FIG. 2 is a cross-sectional photograph illustrating the structure of the spunbonded nonwoven fabric for a filter according to the present invention. As shown in FIG. 2, when the cross section of the spunbonded non-woven fabric for a filter according to the present invention is observed with a scanning electron microscope (SEM), the fused portion where the thermoplastic continuous filament is fused is the thermoplastic continuous filament. Are densely present, and the brightness is increased by the reflected light of the irradiated light, and the brightness is reduced because the thermoplastic continuous filaments are sparsely present in the non-fused portion. The present inventors capture when the ratio of the average reflected light brightness (S1) of the fused portion and the average reflected light brightness (S2) of the non-fused portion in the cross section represented by the formula (1) is within a predetermined range. We have found that it is possible to obtain a spunbonded non-woven fabric for a filter, which has an excellent balance between collecting performance and breathability, and also has excellent rigidity and fluff resistance with excellent pleating workability. When the value of the formula (1) is 0.20 or more, more preferably 0.33 or more, still more preferably 0.50 or more, the fusion between the fibers becomes loose and excellent air permeability can be obtained. On the other hand, when the value of the formula (1) is less than 1.00, more preferably 0.90 or less, still more preferably 0.80 or less, the fusion between the fibers becomes strong and the fiber is used as a powder coating filter. In some cases, excellent shape retention can be obtained even under high air volume.
R = 1-S2 / S1 ... (1)

Here, as the values of the reflected light average brightness (S1) of the fused portion, the reflected light average brightness (S2) of the non-fused portion, and the equation (1) in the present invention, the values obtained as follows are adopted. To do.
(1) Average brightness of reflected light at the fusion site (S1)
(I) In an arbitrary fusion zone, the intersection of the center line in the MD direction and the center line in the CD direction is set as the center point of the fusion zone.
(Ii) Draw a straight line passing through the center point of the fused portion and parallel to the CD direction.
(Iii) Starting from two points on the straight line 0.5 cm away from the center point of the fused portion, a straight line is drawn 1.0 cm along the MD direction, and a straight line connecting the end points is drawn.
(Iv) The area surrounded by the 1.0 cm × 1.0 cm square formed by (i) to (iii) is cut with a razor blade.
(V) In the same manner, a total of 100 measurement samples for the fused portion of 1.0 cm × 1.0 cm are collected from an arbitrary place of the spunbonded non-woven fabric for the filter.
(Vi) Using a scanning electron microscope (SEM) (for example, "VHX-D500" manufactured by KEYENCE CORPORATION), observe the cross section of the fused portion of the measurement sample for the fused portion at a magnification of 150 times. ..
(Vii) Visually draw a line perpendicular to the cross section of the non-woven fabric sheet at the lowest thickness of the fused portion of each observation image, multiply the center position by 500, and measure the photograph for each fused portion. Take a total of 100 photographs, one for each sample, and save in JPG format.
(Viii) An image of 1000 × 1000 pixels is cut out from the saved image.
(Ix) Divide into 40 × 40 pixel grid units.
(X) In each lattice, the average value of the reflected light brightness (reflected light average brightness S1) defined in the YUV color space is calculated for each pixel by using the following formula.
(Reflected light brightness of each pixel) = 0.29891 × R + 0.58661 × G + 0.11448 × B
Here, R, G, and B represent the reflected light brightness of red, green, and blue of the RGB color model, respectively.

(2) Average brightness of reflected light in the non-fused portion (S2)
(I) The center point of the non-fused portion is defined as the midpoint between the center point of the arbitrary fused portion and the center point of the fused portion closest to the adjacent fused portion.
(Ii) Draw a straight line passing through the center point of the non-fused portion and parallel to the CD direction.
(Iii) Starting from two points on the straight line 0.5 cm away from the center point of the non-fused portion, a straight line is drawn 1.0 cm along the MD direction, and a straight line connecting the end points is drawn.
(Iv) The area surrounded by the 1.0 cm × 1.0 cm square formed by (i) to (iii) is cut with a razor blade.
(V) Similarly, a total of 100 measurement samples of 1.0 cm × 1.0 cm are collected from an arbitrary place in the span-bonded non-woven fabric for a filter.
(Vi) Using a scanning electron microscope (SEM) (for example, "VHX-D500" manufactured by KEYENCE CORPORATION), the cross section of the non-fused portion in the non-fused portion sample is adjusted to a magnification of 150 times. Observe.
(Vii) Visually draw a line perpendicular to the cross section of the non-woven fabric sheet at the thickest part of the non-fused portion of each observation image, multiply the center position by 500 times, and take a photograph of each non-fused portion. Take a total of 100 photographs, one for each measurement sample, and save in JPG format.
(Viii) An image of 1000 × 1000 pixels is cut out from the saved image.
(Ix) Divide into 40 × 40 pixel grid units.
(X) In each lattice, the average value of the reflected light brightness (reflected light average brightness S2) defined in the YUV color space is calculated for each pixel by using the following formula.
(Reflected light brightness of each pixel) = 0.29891 × R + 0.58661 × G + 0.11448 × B
Here, R, G, and B represent the reflected light brightness of red, green, and blue of the RGB color model, respectively.

(3) Ratio of average brightness Reflection obtained by calculating the average brightness of reflected light (S2) obtained by the above-mentioned "average brightness of reflected light of non-fused portion (S2)" by "average brightness of reflected light of fusion portion (S1)". The value (S2 / S1) divided by the light average brightness (S1) was substituted into the following equation (1), and the calculated value (R) was used as the ratio of the average brightness.
R = 1- (S2 / S1) ... (1)

The basis weight of the spunbonded non-woven fabric for a filter in the present invention is preferably in the range of ^{150 g / m 2} or more and 300 g / m ^{2 or less.} When the basis weight is 150 g / m ² or more, the rigidity required for pleats can be obtained, which is preferable. On the other hand, when the basis weight is 300 g / m ² or less, preferably 270 g / m ² or less, more preferably 260 g / m ² or less, it is possible to suppress an increase in pressure loss, which is also preferable in terms of cost.
The basis weight here is to collect three samples with a size of 50 cm in length and 50 cm in width, measure each mass, convert the average value of the obtained values per unit area, and place the first decimal place. Obtained by rounding.

Further, the basis weight CV value of the spunbonded nonwoven fabric for filters of the present invention is preferably 5.0% or less. If it is preferably 4.5% or less, and more preferably 4.0% or less, the non-woven fabric can be made denser as the uniformity of the non-woven fabric is improved, so that the collection efficiency is likely to be improved. This is preferable because a satisfactory filter life can be easily obtained. On the other hand, it is more preferable that the basis weight CV value is 1.0% or more because the life of the filter is extended by securing a certain amount of airflow of the spunbonded non-woven fabric for the filter and reducing the pressure loss.

In the present invention, as the basis weight CV value (%) of the spunbonded nonwoven fabric for a filter, a value obtained by measuring as follows is adopted.
(I) Collect a total of 100 small pieces of 5 cm x 5 cm from the spunbonded non-woven fabric for the filter.
(Ii) The mass (g) of each small piece is measured and converted per ^{unit area (1 m 2).}
Convert the result of the average value of _{(iii) (ii) (W} ave), and calculates the standard deviation _{(W sdv)} respectively.
(Iv) Based on the results of (i) to (iii), the basis weight CV value (%) is calculated by the following formula, and the second decimal place is rounded off.
Basis weight CV value _{(%) = W sdv / W} ave × 100

The thickness of the spunbonded nonwoven fabric for a filter 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 setting the thickness to 0.50 mm or more, the rigidity can be improved and a spunbonded non-woven fabric for a filter suitable for use as a filter can be obtained. Further, by setting the thickness to 0.80 mm or less, a spunbonded non-woven fabric for a filter having excellent handleability and workability as a filter can be obtained.

In the present invention, the thickness (mm) of the spunbonded nonwoven fabric for a filter shall be a value obtained by measuring by the following method.
(I) Using a thickness gauge (for example, "TECLOCK" (registered trademark) SM-114 manufactured by Teclock Co., Ltd.), the thickness of the non-woven fabric is measured at 10 points in the CD direction at equal intervals.
(Ii) The thickness of the non-woven fabric (mm) is obtained by rounding off the third decimal place from the above arithmetic mean value.

The apparent density of the spunbonded nonwoven fabric for filters in the present invention ^{is preferably 0.25 g / cm 3} or more and 0.40 g / cm ³ or less. When the apparent density is 0.25 g / cm ³ or more and 0.40 g / cm ³ or less, the spunbonded non-woven fabric has a dense structure, and dust does not easily enter the inside, and the dust removal property is excellent. A more preferable range of apparent density is 0.26 g / cm ³ or more and 0.38 g / cm ³ or less.
In the present invention, the apparent density (g / cm ³ ) of the spunbonded non-woven fabric for a filter is a value obtained by the following formula from the basis weight and thickness of the spunbonded non-woven fabric for a filter. ..
Apparent density (g / cm ³ ) = basis weight (g / m ² ) / thickness (mm) / 1000

The air permeability per unit grain of the spunbonded non-woven fabric for filters in the present invention is 0.05 ((cm ³ / (cm ² · sec)) / (g / m ² )) or more and 0.50 ((cm ³ / ()). It is preferably cm ² · sec)) / (g / m ² )) or less. The air flow rate per unit is 0.05 ((cm ³ / (cm ² · s)) / (g / m ² )) or more, preferably 0.06 ((cm ³ / (cm ² · s))). When it is / (g / m ² )) or more, it is possible to suppress an increase in pressure loss. In addition, the air flow rate per unit is 0.50 ((cm ³ / (cm ² · sec)) / (g / m ² )) or less, preferably 0.48 ((cm ³ / (cm ² · sec)). )) / (G / m ² )) or less, the dust is less likely to stay inside, and the dust removal property is good.

In the present invention, the air flow rate ((cm ³ / (cm ² · sec)) / (g / m ² )) per unit of the spunbonded non-woven fabric for the filter is as follows: JIS L1913: 2010 “General non-woven fabric”. The value obtained by dividing the value measured based on the 6.8.1 "Frazil type method" of "Test method" 6.8 "Breathability (JIS method)" by the above-mentioned scale shall be adopted.
(I) Collect 10 test pieces of 150 mm in length × 150 mm in width at equal intervals in the CD direction of the spunbonded non-woven fabric for the filter.
(Ii) After attaching the test piece to one end of the cylinder of the testing machine, adjust the suction fan and air holes so that the inclined barometer shows a pressure of 125 Pa by the lower limit resistor, and then adjust the suction fan and the air hole of the vertical barometer at that time. Measure the indicated pressure.
(Iii) From the measured pressure and the type of air holes used, the amount of air passing through the test piece (cm ³ / (cm ² · sec)) is obtained from the conversion table attached to the tester.
(Iv) The value obtained by rounding off the first decimal place of the average value obtained from the air flow rate of 10 test pieces is the air flow rate (cm ³ / (cm ² seconds)) of the spunbonded non-woven fabric for the filter. did.
(V) Using the obtained air flow rate of the spunbonded non-woven fabric for filter (cm ³ / (cm ² · sec)), calculate the air flow rate per unit by the following formula, and round off the third digit after the decimal point. Then, the air flow rate per unit grain of the spunbonded non-woven fabric for the filter ((cm ³ / (cm ² · sec)) / (g / m ² )) was calculated.
Air volume per unit grain ((cm ³ / (cm ² · sec)) / (g / m ² )) = Air volume (cm ³ / (cm ² · sec)) / Grain (g / m ² )

The spunbonded non-woven fabric for a filter of the present invention has an excellent balance between dust collection performance and air permeability, and also has excellent rigidity and fluff resistance with excellent pleating workability. Therefore, air containing dust and dust taken in from the outside air. Can be suitably used as a powder coating filter in a powder coating booth that processes 100 to 2000 m ^{3 per minute.} In such a powder coating filter, for example, the above-mentioned spunbonded non-woven fabric for a filter is pleated to obtain a filter medium for a powder coating filter, and then the entire filter medium for the powder coating filter is centered on the axis of the element. For a cylindrical powder coating filter in which the upper and lower ends of the cylinder are fixed after being made into a cylinder, or for the inner wall of a frame material such as a square or round shape made of a metal material or a polymer resin material. It can be a panel-type powder coating filter in which the end of the filter medium is fixed, or a bag-type powder coating filter obtained by processing a spunbonded non-woven fabric for a filter into a bag shape.

The powder coating filter of the present invention uses the above-mentioned filter medium for powder coating filter, and the powder coating filter is, for example, a forced air supply type (push-pull type) in which fans are attached to exhaust and intake air. , Used in natural air supply type powder coating booths with fans attached only to the exhaust. The powder coating filter of the present invention is a forced air supply type (push-pull type) powder that can keep the inside of the powder coating booth at a positive pressure by controlling the air supply and exhaust fans and prevent the intrusion of outside air from other than the air supply port. It can be suitably used for a body painting booth.

The powder coating booth in which the powder coating filter of the present invention is used has an exhaust recycling system that recycles a part of the air exhausted from the powder coating booth and mixes it with the air taken in from the outside air. It may be a powder coating booth.

Next, the present invention will be specifically described based on Examples. However, the present invention is not limited to these examples.

[Measuring method]
Each characteristic value in the following examples is measured by the following method. However, in the measurement of each physical property, if there is no particular description, the measurement is performed based on the above method.
(1) Melting point of polyester (° C)
As a differential scanning calorimeter, "DSC-2 type" manufactured by PerkinElmer Japan Co., Ltd. was used.
(2) Intrinsic viscosity of polyester (IV)
The intrinsic viscosity (IV) of polyester was measured by the following method.
8 g of the sample was dissolved in 100 mL of orthochlorophenol, and the relative viscosity η _r was determined by the following formula using an Ostwald viscometer at a temperature of 25 ° C.
η _r = η / η ₀ = (t × d) / (t ₀ × d ₀ )
(Here, η is the viscosity of the polymer solution, η ₀ is the viscosity of orthochlorophenol, t is the drop time of the solution (seconds), d is the density of the solution (g / cm ³ ), and t ₀ is the drop of orthochlorophenol. Time (seconds) and d ₀ represent the density of orthochlorophenol (g / cm ³ ), respectively.)
Next, the intrinsic viscosity (IV) was calculated from the relative viscosity η _{r by the following formula.}
Intrinsic viscosity (IV) = 0.0242η _r +0.2634.

(3) Average single fiber diameter (μm) of thermoplastic continuous filament
The average single fiber diameter of the thermoplastic continuous filament was calculated by the above method using "VHX-D500" manufactured by KEYENCE CORPORATION as a scanning electron microscope (SEM).
(4) Metsuke of spunbonded non-woven fabric for filter (g / m ² )
The basis weight of the spunbonded non-woven fabric for the filter was calculated by the above method.
(5) Metsuke CV value (%) of spunbonded non-woven fabric for filters
The basis weight CV value of the spunbonded non-woven fabric for a filter was calculated by the above method.
(6) Thickness of spunbonded non-woven fabric for filter (mm)
As a thickness gauge, "TECLOCK" (registered trademark) SM-114 manufactured by Teklock Co., Ltd. was used and evaluated by the above method.
(7) Flexibility (mN) of spunbonded non-woven fabric for filters in the MD direction
The rigidity and softness were measured by the above method using a Gale / flexibility tester "GAS-10" manufactured by Daiei Seiki Seisakusho Co., Ltd.

(8) Average brightness of reflected light at the fused portion of the spunbonded non-woven fabric for filter (S1)
Using "VHX-D500" manufactured by KEYENCE CORPORATION as a scanning electron microscope (SEM), the average brightness (S1) of the reflected light of the fused portion of the spunbonded non-woven fabric for a filter was calculated by the above method.
(9) Average brightness of reflected light at the non-fused portion of the spunbonded non-woven fabric for filter (S2)
Using "VHX-D500" manufactured by KEYENCE CORPORATION as a scanning electron microscope (SEM), the average brightness (S2) of the reflected light of the non-fused portion of the spunbonded non-woven fabric for a filter was calculated by the above method.
(10) Average brightness ratio (R)
The ratio of the average brightness of the non-woven fabric is the average brightness of the reflected light (S2) obtained in the above "(9) Average brightness of reflected light (S2) of the non-fused portion of the spunbonded non-woven fabric". The value (S2 / S1) divided by the reflected light average brightness (S1) obtained in "Reflected light average brightness (S1) of the fused portion of the non-woven fabric" is substituted into the following formula (1), and the calculated value (R) is used. The ratio of average brightness was used.
R = 1- (S2 / S1) ... (1)

(11) Aeration rate of spunbonded non-woven fabric for filter (cm ³ / (cm ² · sec))
The air permeability of the spunbonded non-woven fabric for the filter was measured using a breathability tester "FX3300-III" manufactured by Textest.
(12) Pleating processability of spunbonded non-woven fabric for filter (i) The spunbonded non-woven fabric for filter is cut to a width of 240 mm, and the apex of the pleated molded body is compressed by heating the spunbonded non-woven fabric for filter to 150 ° C. A pleated molded body was obtained by pleating so that the distance from the ridge line of the above to the ridge line of the next apex was 35 mm.
(Ii) This pleated molded product is wound around a porous cylindrical core made of polypropylene by 45 threads, the ends of the pleated molded product are heat-sealed, and then caps made by injection molding are adhered to both ends of the cylindrical shape to pleat. A filter was made.
(Iii) The appearance of the pleated filter produced by 20 panelists was visually confirmed, and the pleated processability of the spunbonded non-woven fabric for the powder coating filter was judged on a 5-point scale based on the following criteria. Therefore, the total score increased from a minimum of 0 to a maximum of 100, and a score of 80 or higher was judged to be acceptable.
5 points: Very good (there is no contact between the pleated piles or the pleated shape is distorted, and the adjacent ridges are lined up in a straight line in parallel).
4 points: Good (between 5 and 3 points)
3 points: Normal (There is no contact between the pleated parts, but the pleated shape is distorted.)
2 points: Bad (between 3 points and 2 points)
1 point: Very bad (the pleated shape is distorted and the pleated parts are in contact with each other)

(13) Fluffing property of spunbonded non-woven fabric for filter (points)
(I) From the filter spunbonded non-woven fabric, cut 5 points of the sample of MD direction 250 mm × CD direction 25 mm at equal intervals in the CD direction of the filter spunbonded non-woven fabric, and cut out a total of 10 sheets of each of the front and back sides of the filter spunbonded non-woven fabric.
(Ii) Using a Gakushin-type dyed product abrasion fastness tester, the fabric is abraded at a load of 300 gf and a number of abrasions of 200 reciprocations.
(Iii) The fluffing on the surface of the spunbonded non-woven fabric for the filter was judged on a 5-point scale based on the following criteria based on the texture when 20 panelists visually and touched the spunbonded non-woven fabric for the filter after the test. The total score judged by each panelist was used to evaluate the fluffiness of the spunbonded non-woven fabric for filters. Therefore, the total score increased from a minimum of 0 to a maximum of 100, and a score of 80 or higher was judged to be acceptable.
5 points: Very good (no fluff is generated on the surface of the spunbonded non-woven fabric for the filter, and the surface of the spunbonded non-woven fabric for the filter has a smooth feel when touched with a finger, and no resistance is felt to the finger.)
4 points: Good (between 5 and 3 points)
3 points: Normal (There is no fluff on the surface of the spunbonded non-woven fabric for the filter, but when touched with a finger, the surface of the spunbonded non-woven fabric for the filter has a rough feel, and the finger feels resistance.)
2 points: Bad (between 3 points and 1 point)
1 point: Very bad (fluffing occurs on the surface of the spunbonded non-woven fabric for the filter, and when touched with a finger, the surface of the spunbonded non-woven fabric for the filter has a rough feel, and the finger feels resistance).

(14) Collection efficiency (%) of spunbonded non-woven fabric
FIG. 3 is a diagram for explaining a configuration of a test system for carrying out a collection performance test according to an embodiment of the present invention. The test system 51 shown in FIG. 3 includes a sample holder 52 for setting the test sample M, a flow meter 53, a flow rate adjusting valve 54, a blower 55, a dust supply device 56, a switching cock 57, and a particle counter 58. Be prepared. It has a flow meter 53, a flow rate adjusting valve 54, a blower 55, and a dust supply device 56, and the dust supply device 56 is connected to a sample holder 52. The flow meter 53 is connected to the blower 55 via a flow rate adjusting valve 54. Dust is supplied to the sample holder 52 from the dust supply device 56 by the intake air of the blower 55. A particle counter 58 is connected to the sample holder 52, and the number of dusts on the upstream side and the number of dusts on the downstream side of the test sample M can be measured via the switching cock 57, respectively. First, three 15 cm × 15 cm samples are collected from an arbitrary part of the spunbonded non-woven fabric, and the collected test sample M is set in the sample holder 52. The evaluation area of the test sample M was 115 cm ² . In measuring the collection performance, a polystyrene 0.309U 10% by mass solution (manufactured by Nacalai Tesque, Inc.) was diluted with distilled water up to 200 times and filled in the dust supply device 56. The air volume is adjusted by the flow rate adjusting valve 54 so that the filter passing speed becomes 3.0 m / min, and the dust concentration is 20,000 to 70,000 / ^{(2.83 × 10 -4} m ³ (0.01 ft ³ )). The number of dusts D2 upstream and D1 downstream of the test sample M were measured with a particle counter 58 (manufactured by Rion Co., Ltd., KC-01D) in the range of dust particle size of 0.3 to 0.5 μm. Each was measured. The obtained value was substituted into the following formula, and the first decimal place of the calculated value was rounded off to obtain the collection performance (%).
Collection performance (%) = [1- (D1 / D2)] x 100
Here, D1: the number of dusts downstream (total of 3 times), D2: the number of dusts upstream (total of 3 times).

(15) Pressure loss (Pa)
The static pressure difference between the upstream and downstream of the test sample M at the time of measuring the collection performance was read by a pressure gauge 59, and the average value of the values obtained from the three samples was rounded off to the first decimal place.

[Resin used]
Next, the details of the resins used in Examples and Comparative Examples will be described.
-Polyester resin A: Polyethylene terephthalate (PET) dried to a moisture content of 50 mass ppm or less, having an intrinsic viscosity (IV) of 0.65 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 0.64, an isophthalic acid copolymerization rate of 11 mol%, and a melting point of 230 ° C. ..

[Example 1]
The polyester-based resin A and the polyester-based resin B were melted at temperatures of 295 ° C. and 280 ° C., respectively. After that, polyester resin A is used as a core component, polyester resin B is used as a sheath component, the base temperature is 295 ° C., and the core: sheath = 80:20 is spun from the pores, and then spun by air soccer. A filament having a circular cross-sectional shape was spun at a speed of 4900 m / min, and the fiber arrangement was regulated and deposited by a fiber-spreading plate on a moving net conveyor, and a fiber web composed of fibers having an average single fiber diameter of 14.8 μm was collected. .. The collected fiber webs were tentatively fused to the collected fiber webs by a calendar roll composed of a pair of flat rolls under the conditions of a temperature of 140 ° C. and a linear pressure of 50 kg / cm. Further, subsequently, by embossing rolls composed of a pair of engraving rolls having a fused area ratio of 10% and an area of 1.6 mm ² per fused portion, the upper and lower temperatures are 200 ° C. and the linear pressure is 70 kg / cm. By fusing under the conditions, a spunbonded non-woven fabric for a filter having a basis weight of 200 g / m ^{2 was obtained.} The obtained spunbonded non-woven fabric for filter has a grain CV value of 3.3%, a thickness of 0.70 mm, a rigidity in the MD direction of 27 mN, and an average brightness ratio (R) of 0.57. The air volume (q) per unit number was 0.11 (cm ³ / (cm ² · sec)) / (g / m ² ). The results are shown in Table 1.

[Example 2]
The upper and lower embossed rolls are made of a pair of engraving rolls having a fusion area ratio of 10% and an area of 1.6 mm ² per fusion portion, and the fusion area ratio is 18% and one fusion portion. A spunbonded non-woven fabric for a filter ^{having a grain size of 200 g / m 2} was obtained under the same conditions as in Example 1 except that it was used instead of an embossed roll composed of a pair of engraving rolls having an area of 0.7 mm ^2. The obtained spunbonded non-woven fabric for filters had a CV value of 4.8%, a thickness of 0.54 mm, a rigidity of 22 mN in the MD direction, and an average brightness ratio (R) of 0.41. The air volume (q) per unit number was 0.10 (cm ³ / (cm ² · sec)) / (g / m ² ). The results are shown in Table 1.

[Example 3]
The temperature of the upper and lower embossed rolls was changed from 200 ° C. to 180 ° C., respectively, and a spunbonded non-woven fabric for a filter ^{having a basis weight of 200 g / m 2 was obtained under the same conditions as in Example 1 except that they were fused.} The obtained spunbonded non-woven fabric for filters had a CV value of 3.6%, a thickness of 0.91 mm, a rigidity of 24 mN in the MD direction, and an average brightness ratio (R) of 0.72. The air volume (q) per unit number was 0.13 (cm ³ / (cm ² · sec)) / (g / m ² ). The results are shown in Table 1.

[Example 4]
The temperature of the upper and lower embossed rolls was changed from 200 ° C. to 210 ° C., respectively, and a spunbonded non-woven fabric for a filter ^{having a basis weight of 200 g / m 2 was obtained under the same conditions as in Example 1 except that they were fused.} The obtained spunbonded non-woven fabric for filter has a grain CV value of 3.4%, a thickness of 0.70 mm, a rigidity in the MD direction of 23 mN, and an average brightness ratio (R) of 0.50. The air volume (q) per unit number was 0.12 (cm ³ / (cm ² · sec)) / (g / m ² ). The results are shown in Table 1.

[Example 5]
While the spinning speed was changed so that the average single fiber diameter was 24.6 μm, the basis weight was changed under the same conditions as in Example 1 except that the speed of the net conveyor was changed to make the basis weight the same as in Example 1. A 200 g / m ² filter spunbonded non-woven fabric was obtained. The obtained spunbonded non-woven fabric for filter has a CV value of 4.3%, a thickness of 0.90 mm, a rigidity of 29 mN in the MD direction, an average brightness ratio (R) of 0.66, and a unit grain. The per-ventilation amount (q) was 0.15 (cm ³ / (cm ² · sec)) / (g / m ² ). The results are shown in Table 1.

The characteristics of the obtained non-woven fabric are as shown in Table 1. All of the spunbonded non-woven fabrics of Examples 1, 2, 3, 4, and 5 have a rigidity of 15 mN or more in the MD direction and a basis weight CV value of 5. % Or less, excellent in rigidity and basis weight uniformity, and exhibited good characteristics as a spunbonded non-woven fabric for filters. In addition, the results of the pleating processability and the fluffing property were also good, with the pleating processability being 90 points or more and the fluffing property being 87 points or more. The results are shown in Table 1.

[Comparative Example 1]
In the manufacturing process of Example 1, after the sheet obtained in the temporary fusion step is once wound between the step of temporarily fusionizing the collected fiber web and the step of fusion using an embossed roll. Examples except that the step of cooling to room temperature and feeding this sheet to the embossed roll is provided, that is, the step of fusing using the embossed roll is not performed following the temporary fusing step. Under the same conditions as in No. 1, a spunbonded non-woven fabric for a filter ^{having a grain size of 200 g / m 2 was obtained.} The obtained spunbonded non-woven fabric for filter has a CV value of 5.9%, a thickness of 0.66 mm, a rigidity of 32 mN in the MD direction, and a ratio (R) of the average brightness of reflected light of 0.18. The air volume (q) per unit number was 0.13 (cm ³ / (cm ² · sec)) / (g / m ² ). The results are shown in Table 1.

[Comparative Example 2]
The upper and lower embossed rolls are made of a pair of engraving rolls having a fusion area ratio of 10% and an area of 1.6 mm ² per fusion portion, and a fusion area ratio of 15% and a fusion portion per fusion portion. Same as in Example 1 except that the embossed roll consisting of an engraving roll and a flat roll having an area of 1.6 mm ^{2 was fused and the net conveyor was adjusted so that the grain size was 260 g / m 2.} As a condition, a spunbonded non-woven fabric for a filter was obtained. The obtained spunbonded non-woven fabric for filter has a grain CV value of 3.5%, a thickness of 0.62 mm, a rigidity of 24 mN in the MD direction, and a ratio (R) of reflected light average brightness of 0.16. The air volume (q) per unit was 0.04 (cm ³ / (cm ² · sec)) / (g / m ² ). The results are shown in Table 1.

[Comparative Example 3]
Under the same conditions as in Example 1 except that the discharge rate and spinning speed were changed so that the average single fiber diameter was 29.2 μm, while the speed of the net conveyor was changed to make the basis weight the same as in Example 1. , A spunbonded non-woven fabric for a filter having a basis weight of 150 g / m ^{2 was obtained.} The obtained filter spunbonded non-woven fabric has a basis weight CV value of 6.1%, a thickness of 1.00 mm, a rigidity in the MD direction of 35 mN, and an average brightness ratio (R) of 0.57. The air flow rate (q) per basis weight was 0.60 (cm ³ / (cm ² · sec)) / (g / m ² ). The results are shown in Table 1.

[Comparative Example 4]
Under the same conditions as in Example 1 except that the discharge rate and spinning speed were changed so that the average single fiber diameter was 11.2 μm, while the speed of the net conveyor was changed to make the basis weight the same as in Example 1. , A spunbonded non-woven fabric for a filter having a basis weight of 200 g / m ^{2 was obtained.} The obtained filter spunbonded non-woven fabric has a basis weight CV value of 2.6%, a thickness of 0.55 mm, a rigidity in the MD direction of 9 mN, and an average brightness ratio (R) of 0.57. The air flow rate (q) per basis weight was 0.04 (cm ³ / (cm ² · sec)) / (g / m ² ). The results are shown in Table 1.

[Comparative Example 5]
The polyester-based resin A and the polyester-based resin B were melted at temperatures of 295 ° C. and 280 ° C., respectively. After that, polyester resin A is used as a core component, polyester resin B is used as a sheath component, the base temperature is 300 ° C., and the core: sheath = 80:20 is spun from the pores, and then spun by air soccer. A filament having a circular cross section is spun at a speed of 4400 m / min, the filament is made to collide with a metal collision plate installed at an air soccer outlet, and the fiber is charged and opened by friction charging, and the average single fiber diameter is 14.8 μm. A fiber web of fibers was collected on a moving net conveyor. Further, subsequently, by embossing rolls composed of a pair of engraving rolls having a fused area ratio of 24% and an area of 0.7 mm ² per fused portion, the upper and lower temperatures are 205 ° C. and the linear pressure is 70 kg / cm. By fusing under the conditions, a spunbonded non-woven fabric for a filter having a basis weight of 200 g / m ^{2 was obtained.} The obtained filter spunbonded non-woven fabric has a basis weight CV value of 12.1%, a thickness of 0.52 mm, a rigidity in the MD direction of 14 mN, and an average brightness ratio (R) of 0.41. The air volume (q) per basis weight was 0.04 (cm ³ / (cm ² · sec)) / (g / m ² ). The results are shown in Table 1.

The characteristics of the obtained spunbonded nonwoven fabric for filters are as shown in Table 1, but in Comparative Example 1, the air permeability of the nonwoven fabric was low, and the pleating and fluffing properties were inferior. In Comparative Example 2, the ratio of the average brightness was low, the air permeability of the non-woven fabric was low, and the pleating workability was inferior. Comparative Example 3 had high rigidity and softness of the non-woven fabric and was inferior in pleating workability, and Comparative Example 4 had low rigidity and low air permeability, and was inferior in pleating workability and fluffing property. In Comparative Example 5, the non-woven fabric had low rigidity and softness, and the pleating workability was inferior.

21: Filter material for powder coating filter 22: Mountain part 23: Tani part 24: Arrow indicating MD direction 25: Arrow indicating CD direction M: Test sample 51: Collection performance measuring device 52: Sample holder 53: Flow meter 54 : Flow rate adjustment valve 55: Blower 56: Dust supply device 57: Switching cock 58: Particle counter 59: Pressure gauge

Claims (7)

A spunbonded non-woven fabric for a filter composed of a thermoplastic continuous filament composed of a high melting point component and a low melting point component and partially fused.
The rigidity in the MD (vertical) direction is 15 mN or more and 30 mN or less, and the average reflected light brightness (S1) of the fused portion and the average reflected light brightness (S1) of the non-woven fabric in the cross section represented by the following formula (1). The ratio of S2) is 0.20 or more and less than 1.0, and the air volume (q) (cm ³ / (cm ² · sec)) / (g / m ² ) per unit is 0.05 or more and 0. A spunbonded non-woven fabric for filters that is 5.5 or less.
R = 1-S2 / S1 ... (1) The spunbonded non-woven fabric for a filter according to claim 1, wherein the basis weight CV value is 5.0% or less. The spunbonded non-woven fabric for a filter according to claim 1 or 2, wherein the ratio of the area of the fused portion is 5% or more and 20% or less. The spunbonded nonwoven fabric for a filter according to any one of claims 1 to 3, wherein the average single fiber diameter of the thermoplastic continuous filament is 12.0 μm or more and 26.0 μm or less. The spunbonded nonwoven fabric for a filter according to any one of claims 1 to 4, which is a spunbonded nonwoven fabric for a powder coating filter. A filter medium for a powder-coated filter using the spunbonded non-woven fabric for a filter according to any one of claims 1 to 4. A powder coating filter using the filter medium for the powder coating filter according to claim 6.

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