JP2021098196A - Spun-bonded nonwoven fabric for filter, filter medium for automobile oil filter, and automobile oil filter - Google Patents

Abstract

To provide spun-bonded nonwoven fabric for a filter, a filter medium for an automobile oil filter and an automobile oil filter which are excellent in oil liquid permeability and pleat processability, and shape retention.SOLUTION: A filter medium is composed of a thermoplastic continuous filament composed of a high melting point component and a low melting component, is partially fused, has a non-fused projection 11 and a fused recess 12, has an average single fiber diameter of 8.0 μm or more and 15.0 μm or less, and has bending resistance in an MD direction of 20 mN or more and 80 mN or less. When a thickness from one surface to the other surface of the projection in the cross section of the non-woven fabric is represented by tA, a thickness from one surface to the other surface of the projection is represented by tB, and distances between one surface of the projection and one surface of the recess are represented by tC and tD (tC<tD), the following formula (1): 0.35≤1-tB/tA<1.00, and the following formula (2): 0.3<tC/tD<1.0 are satisfied.SELECTED DRAWING: Figure 1

Description

The present invention relates to a spunbonded nonwoven fabric for a filter, a filter medium for an automobile oil filter, and an automobile oil filter, which are excellent in liquid permeability and pleated workability.

Conventionally, engine oil has been used in automobiles for the purpose of efficiently operating the engine. Engine oil circulates inside the engine of an automobile and is used repeatedly. The engine oil that circulates inside the engine contains contaminants such as carbon particles and metal powder generated by dirt and wear, and it is necessary to recover these contaminants in order to send this engine oil back into the engine. is there.

Further, conventionally, an oil filter made of a non-woven fabric has been applied for the purpose of recovering contaminants contained in automobile engine oil. Such a non-woven fabric is a non-woven fabric made by mixing cotton linter pulp or wood pulp with chemical fibers such as polyester, rayon, and acrylic and processed with a phenol resin to impart physical strength, or a fusion-type non-woven fabric. Long fiber non-woven fabric is used. In particular, in recent years, spunbonded non-woven fabrics that do not use thermosetting resins such as phenol resins have been attracting attention from the viewpoint of environmental load. Nonwoven fabrics for automobile oil filters are known to be used in a pleated shape, and by pleating, the filtration area can be significantly improved, pressure loss can be reduced, and collection efficiency can be improved. It is possible.

Among the non-woven fabrics used for such automobile oil filters, spunbonded non-woven fabrics are particularly excellent in lint-free properties and strong performance with respect to short-fiber non-woven fabrics, so they are installed in engine oil. It is used as a filter. For example, Patent Document 1 and Patent Document 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 describes 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 multi-leaf composite fiber composed of a high melting point component and a low melting point component. Non-woven fabric is disclosed. The spunbonded non-woven fabric used for automobile oil filters needs to have both oil permeability and pleating workability.

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

By the way, the conventional spunbonded non-woven fabric for an oil filter used for removing impurities in automobile engine oil has not been obtained having sufficient rigidity for pleating when the liquid permeability of the oil is increased. That is, if the fusion of the fibers is strengthened in order to improve the rigidity, the opening becomes smaller, which leads to a decrease in liquid permeability. On the other hand, if the fusion between the fibers is loosened in order to improve the liquid permeability, the opening becomes large, the oil circulates at a hydraulic pressure of 300 to 500 kPa, and the pleated shape retention is lowered at a high flow rate of filtration. There was a problem that the outflow of impurities into the oil had an adverse effect on the engine.

For example, in the techniques disclosed in Patent Documents 1 and 2, fibers or non-woven fabrics formed by heat treatment are fused, and it is difficult to achieve both sufficient liquid permeability and rigidity.
On the other hand, in Patent Document 3, the fusion between fibers is weak, the rigidity of the non-woven fabric is reduced due to the breakage of the fused portion during pleating, and when used as a filter, the shape retention of the pleats is reduced at high flow rates. There was a challenge.

Therefore, in view of the above problems, an object of the present invention is to provide a spunbonded non-woven fabric that has both a balance between the ability to collect contaminants in automobile engine oil and liquid permeability, has high rigidity, and is excellent in pleating workability. The purpose of the present invention is to provide filter media for automobile oil filters and automobile oil filters.

As a result of diligent studies to achieve the above object, the present inventors have obtained the ratio of the thickness of the convex portion to the thickness of the concave portion and the convexity obtained from the cross section of the non-woven fabric composed of the partially fused thermoplastic continuous filament. By setting the ratio of the distance from the surface of the part to the surface of the recess within a specific value range, a spunbonded non-woven fabric for automobile oil filters that has excellent liquid permeability and sufficient rigidity to pleat and retain its shape can be obtained. I got the finding that it can be obtained.

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 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 non-fused. The average single fiber diameter constituting the spunbonded non-woven fabric for an automobile oil filter is 8.0 μm or more and 15.0 μm or less, and the rigidity and softness in the MD direction are It is 20 mN or more and 80 mN or less, and in the non-woven fabric cross section, the thickness t _{A from one surface of the convex portion to the other surface, the thickness t B} from one surface of the concave portion to the other surface, and one surface of the convex portion. A spunbonded non-woven fabric for a filter having a relationship represented by the following formulas (1) and (2), where the distances to one surface of the recess are t _C and t _D (t _C <t _{D), respectively.}
0.35 ≤ 1-t _B / t _A <1.00 ... (1)
0.3 <t _C / t _D <1.0 ... (2)

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 fused area of the recess is 5% or more and 20% or less.

The spunbonded non-woven fabric for a filter of the present invention is a spunbonded non-woven fabric for an automobile oil filter.

The spunbonded non-woven fabric for an automobile oil filter of the present invention is used as a filter medium for an automobile oil filter.

The filter medium for an automobile oil filter of the present invention is used for an automobile oil filter.

According to the present invention, it is possible to obtain a spunbonded non-woven fabric for a filter which has both the balance of impurity collection performance in automobile engine oil and liquid permeability, has high rigidity, and is excellent in pleating workability.

FIG. 1 is a cross-sectional photograph of a spunbonded nonwoven fabric for a filter according to an embodiment of the present invention. FIG. 2 is a schematic perspective view showing an example of a filter medium for an automobile oil filter of 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.

Hereinafter, embodiments for carrying out the present invention will be described in detail. The present invention is not limited to the following embodiments.

The spunbonded non-woven fabric for a filter of the present invention is a non-woven fabric made of a thermoplastic continuous filament. The thermoplastic continuous filament is composed of a high melting point component and a low melting point component. FIG. 1 is a cross-sectional photograph of a spunbonded nonwoven fabric for a filter according to an embodiment of the present invention. The filter spunbonded non-woven fabric shown in FIG. 1 is ventilated from top to bottom during use. The spunbonded non-woven fabric for a filter is partially fused, and the average single fiber diameter constituting the non-woven fabric is 8.0 μm or more and 15.0 μm or less, and the rigidity in the MD direction is 20 mN or more and 80 mN or less. It has a non-fused convex portion 11 (non-fused portion) and a fused concave portion 12 (fused portion), and has a thickness from one surface to the other surface of the convex portion in the non-woven fabric cross section. (T _A ), the thickness from one surface of the concave portion to the other surface (t _B ), and the distance from one surface of the convex portion to one surface of the concave portion are (t _C ), (t _D ) (t), respectively. _C <t _D ), which is a spunbonded non-woven fabric for a filter having the following formula.
0.35 ≤ 1-t _B / t _A <1.00 ... (1)
0.3 <t _C / t _D <1.0 ... (2)
Here, in the present invention, the MD direction refers to the sheet transporting direction at the time of manufacturing the spunbonded nonwoven fabric for a filter, that is, the winding direction in the nonwoven fabric roll, and the CD direction described later is the sheet conveying direction, that is, winding in the nonwoven fabric roll. It refers to the direction that intersects perpendicularly to the taking direction. If the filter spunbonded non-woven fabric is not in the rolled state due to cutting, the MD direction and the CD direction are determined by the following procedure.
(A) In the plane of the spunbonded non-woven fabric for a filter, 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 for a filter, which will be 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 for the filter, and the direction orthogonal to this is the CD direction.

Further, the spunbonded non-woven fabric for a filter of the present invention is used for a filter, for example, a filter medium for an automobile oil filter. FIG. 2 is a schematic perspective view showing an example of a filter medium for an automobile oil filter of the present invention. The filter medium 21 for an automobile oil filter shown in FIG. 2 has a peak portion 22 and a valley portion 23 formed by folding back a spunbonded non-woven fabric. When determining the MD direction and the CD direction from an automobile oil filter filter medium or the like, in the case of the automobile oil filter filter medium 21 as illustrated in FIG. 2, the direction parallel to the ridgeline of the mountain portion 22 (broken line arrow 25). Is the CD direction, and the direction orthogonal to the CD direction (broken line arrow 24) is the MD direction.

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

In addition, these polyester raw materials include crystal nucleating agents, matting agents, pigments, fungicides, antibacterial agents, flame retardants, metal oxides, aliphatic bisamides and / or fats, as long as the effects of the present invention are not impaired. Additives such as group monoamides and 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.

Next, the thermoplastic continuous filament constituting the spunbonded non-woven fabric for a filter of the present invention has a temperature of 10 ° C. around the polyester-based refractory polymer, which is a refractory component, with respect to the melting point of the polyester-based refractory polymer. It is preferable that the filament is a composite filament in which a polyester-based low melting point polymer, which is a low melting point component having a low melting point of 140 ° C. or lower, 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 oil treatment under high flow rate.

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 Japan Co., Ltd.), a temperature rise rate of 20 ° C./min, and a measurement temperature range of 30 ° C. The temperature at which an extreme value is given in the obtained melting heat absorption curve is defined as the melting point of the thermoplastic resin. 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, the combination of the paired polyester-based high-melting-melter polymer and the polyester-based low-melting-point polymer (hereinafter, polyester-based high-melting-melter polymer / polyester-based low-melting-melter polymer may be described in this order. ) Examples include combinations of PET / PBT, PET / PTT, PET / polylactic acid, PET / copolymerized PET, and the like. Among these, PET / copolymerized PET has excellent spinnability. The combination 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. Uniform fusion is difficult, for example, where fibers made of polyester-based refractory polymer are densely fused, the fusion becomes weak, and the mechanical strength and rigidity are inferior, making it unsuitable as a spunbonded non-woven fabric for filters. .. 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 improved. Is inferior, which is not preferable as a spunbonded non-woven fabric for a filter.

The melting point of the polyester-based low melting point polymer in the present invention is preferably 10 ° C. or higher and 140 ° C. or lower lower than the melting point of the polyester-based high melting point polymer. By lowering the temperature by 10 ° C. or higher, preferably 20 ° C. or higher, more preferably 30 ° C. or higher, an appropriate fusion property can be obtained in the spunbonded nonwoven fabric for filters. On the other hand, the melting point of the polyester-based low melting point polymer is 140 ° C. or lower, preferably 120 ° C. or lower, more preferably 100 ° C. or lower than the melting point of the polyester-based high melting point polymer, so that the heat resistance of the spunbonded non-woven fabric for a filter is reduced. Can be suppressed.

The melting point of the polyester-based high melting point polymer 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 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.

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 shape retention 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 filter having excellent meltability during the production of a non-woven 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 in terms of mass ratio, and more preferably in the range of 85: 15 to 70:30. This is a 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 for a filter can be improved. On the other hand, when the low melting point polyester is 10% by mass or more and 40% by mass or less to form a spunbonded non-woven fabric for a filter by fusion, the composite polyester fibers (filaments) constituting the spunbonded non-woven fabric for a filter are used. Can be firmly fused, has excellent mechanical strength, and can sufficiently withstand oil treatment under a high flow rate.

Examples of the composite form of the composite polyester fiber include a concentric sheath type, an eccentric core sheath type, a sea island type, and the like. Among them, the concentric sheath type because the filaments can be fused uniformly and firmly. Is preferable. Further, examples of the cross-sectional shape of the filament (single fiber) 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 (single fiber) having a circular cross section as the cross-sectional shape.

The average single fiber diameter of the thermoplastic continuous filament constituting the spunbonded nonwoven fabric for a filter of the present invention is in the range of 8.0 μm or more and 15.0 μm or less. By setting the average single fiber diameter of the thermoplastic continuous filament to 8.0 μm or more, preferably 8.2 μm or more, more preferably 8.5 μm or more, the liquid permeability of the spunbonded non-woven fabric for a filter is improved and the pressure loss is reduced. It can be reduced. 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 15.0 μm or less, more preferably 14.8 μm or less, the uniformity of the spunbonded non-woven fabric for a filter is improved and the surface of the non-woven fabric is made dense. When used as a spunbonded non-woven fabric for an automobile oil filter, for example, the collection performance can be improved by facilitating the filtration of engine oil on the surface layer.

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 from 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 single fiber diameter.
(Iv) The value calculated by rounding off the second decimal place of those arithmetic mean values was 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 opening the obtained filament and forming a fiber web by regulating and depositing the fiber arrangement with a fiber opening plate on a moving net conveyor.
(C) A step of partially fusing the obtained fiber web.
The details of each step will be described below.

(1) (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 the polyester-based high-melting-melting polymer is used as the thermoplastic continuous filament, there is no case. 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, the melting point of the polyester-based high-melting-melting polymer 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, air is spun from the pores with a spinning mouthpiece having a base temperature of 10 ° C. or higher and 140 ° C. or lower. A filament having 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 soccer.

(2) (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 from an open fiber plate having a slit shape at the lower part of the ejector. It has a step of obtaining a fiber web by depositing it on a net conveyor that is jetted and moved.

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 is preferable as a spunbonded non-woven fabric for a filter. it can.

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 65 kg / cm or less, excessive fusion between the fibers can be prevented.

(3) (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. Here, the fused portion of the spunbonded non-woven fabric for the filter is referred to as a fused portion, and the other non-fused portion is referred to as a non-fused portion. 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 heat embossing roll is most preferable from the viewpoint of improving the strength of the non-woven fabric. 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 is increased, and a non-woven fabric having a waist strength excellent in pleating workability can be obtained as a spunbonded non-woven fabric for a filter. 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 of the melting points 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, the strength required for pleating processability can be imparted to the non-woven fabric when used as a spunbonded non-woven fabric for a filter. 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 fusion area of the partial fusion of the spunbonded nonwoven fabric for filters of the present invention (sometimes referred to simply as the fusion area ratio) is the ratio of the fusion portion (recess) to the total area of the nonwoven fabric. That is, 5% or more and 20% or less with respect to the total area of the non-woven fabric is a preferable range. 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, when 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 is not deteriorated. ..

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 transporting direction at the time of manufacturing the spunbonded nonwoven fabric for a filter, that is, the winding direction in the nonwoven fabric roll, and the CD direction is the sheet conveying direction, that is, the winding direction in the nonwoven fabric roll. It points in a direction that intersects perpendicularly to. When the spunbonded non-woven fabric for the filter 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 for the filter, 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 an automobile oil filter or the like, in the case of the filter medium 21 for an automobile oil filter as illustrated in FIG. 2, the direction 25 parallel to the ridgeline of the mountain portion 22 is the CD. It is assumed that the direction 24 orthogonal to the direction and the CD direction is the MD direction.

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. By setting the thickness to 5.0 mm ² or less, not only the mechanical strength of the spunbonded non-woven fabric for a filter but also the air permeability can be maintained, 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, and a roll having a predetermined pattern of unevenness is used only on the upper side or the lower side, and the other rolls are flat rolls without unevenness. 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 groove of the upper roll and the groove of the lower roll are at an angle. In the embossed rolls provided so as to intersect, 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, or parallelogram. , Oval, rhombus, etc. 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 that the non-woven fabric is partially fused without peeling, 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 of the upper roll. A parallelogram formed by fusing the convex portion of the upper roll and the convex portion of the lower roll using an embossed roll provided so that the groove and the groove of the lower roll intersect at a certain angle. The fused portion is preferable.

(4) Spunbonded Nonwoven Fabric for Filter The spunbonded nonwoven fabric for filter of the present invention has a rigidity of 20 mN or more and 80 mN or less in the MD direction of the non-woven fabric. When the rigidity is 20 mN or more, more preferably 25 mN or more, and further preferably 30 mN or more, pleating can be performed while maintaining the strength of the non-woven fabric. On the other hand, if it is 80 mN or less, more preferably 75 mN or less, and further preferably 70 mN or less, the folding resistance during pleating is relaxed, and the pleated mountain valley shape is sharply finished.

Here, the rigidity in the present invention is set to 6.7.4 "Gare method (JIS method)" of JIS L1913: 2010 "General non-woven fabric test method" 6.7 "Rigidity and softness (JIS method and ISO method)". According to this, the value obtained by doing the following.
(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 MD 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 off to the second decimal place using the following formula (3). 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 nonwoven fabric for filters in the present invention, the thickness (t _A ) from one surface of the convex portion to the other surface and the thickness (t _B ) from one surface of the concave portion to the other surface in the cross section of the nonwoven fabric are the above formulas (1). ) Is a spunbonded non-woven fabric for filters. When the value of the above formula (1) is 0.35 or more, more preferably 0.38 or more, still more preferably 0.40 or more, the fusion between the fibers becomes strong, and when used as an automobile oil filter, for example. Excellent pleated shape retention can be obtained even under high flow rate. On the other hand, when the value of the above formula (1) is 1.00 or less, more preferably 0.90 or less, still more preferably 0.80 or less, the fusion between the fibers becomes loose and excellent liquid permeability is obtained. Be done.

In the spunbonded nonwoven fabric for filters in the present invention, the distances from one surface of the convex portion to one surface of the concave portion in the cross section of the nonwoven fabric are (t _C ) and (t _D ) (t _C <t _D ), respectively, and the above formula (2) It is a spunbonded non-woven fabric for a filter having a relationship of. When the value of the above equation (2) is 0.65 or more, more preferably 0.66 or more, and further preferably 0.67 or more, the unevenness of the non-woven fabric becomes small, and the mountain valley shape of the pleats becomes sharp during pleating. Finished. On the other hand, if the value of the formula (2) is 1.00 or less, more preferably 0.90 or less, still more preferably 0.80 or less, the fused portion and the specific fused portion coexist in the non-woven fabric, and the liquid permeates. A non-woven fabric having a good balance between properties and rigidity can be obtained.

Here, in the present invention, the thickness from one surface of the convex portion to the other surface (t _A ) in the present invention, the thickness from one surface of the concave portion to the other surface (t _B ), and the value of the above equation (1). , And the distances from one surface of the convex portion to one surface of the concave portion (t _C ), (t _D ) (t _C <t _D ) and the values of the above equation (2) are obtained as follows. The value will be adopted.

(I) In any fusion portion (recess), 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 portion (recess).
(Ii) A straight line is drawn that passes through the center point of the fused portion (recess) and is 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 (recess), draw a straight line 1.0 cm along the MD direction, and draw a straight line connecting the end points. ..
(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 of 1.0 cm × 1.0 cm are collected from an arbitrary location in the spunbonded non-woven fabric.
(Vi) Using a scanning electron microscope (SEM) (for example, "VHX-D500" manufactured by KEYENCE CORPORATION), the cross section of the measurement sample is adjusted to a magnification of 100 times and photographed. To do.
(Vii) A tangent line is drawn from the two top points of the adjacent non-fused portion (convex portion), and the cross-sectional thickness t _{A to t D} of the following spunbonded non-woven fabric is obtained from the distance between the parallel lines with respect to the tangent line. Measure (t _C <t _D ).
t _A : Distance between the tops of non-fused parts (convex parts) _{from one surface to the other surface t B} : Distance between the tops of fused parts (concave parts) from one surface to the other surface t _C , t _D : One surface Distance between the top of the non-fused part (convex part) and the top of the fused part (concave part) (t _C <t _D )
(Viii) The ratio of _{t B} / t _A and t _C / t _D is calculated from the measurement result.
_{(Ix) Calculate the arithmetic mean value of t B} / t _A and t _C / t _D obtained from each measurement sample, and adopt the value obtained by rounding off the third decimal place.

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 referred to here is to collect three samples with a size of 50 cm in length and 50 cm in width, measure each mass, and convert ^{the average value (g) of the obtained values per unit area (1 m 2).} , Obtained by rounding off the first decimal place.

Further, the basis weight CV value of the spunbonded nonwoven fabric for filters of the present invention is preferably 5.0% or less. More preferably, the basis weight CV value is 4.8% or less, and further preferably 4.5% 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 preferable because the filter life is easily improved and a satisfactory filter life is easily obtained. On the other hand, for example, when the spunbonded non-woven fabric for a filter of the present invention is used as a spunbonded non-woven fabric for an automobile oil filter, the filter life is extended by securing a certain amount of liquid permeation of the spunbonded nonwoven fabric for a filter and reducing the pressure loss. In order to make it longer, it is more preferable that the grain CV value is 1% or more.

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 × 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 for a filter 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

Since the spunbonded non-woven fabric for a filter of the present invention is excellent in liquid permeability and pleated workability, it can be suitably used as an automobile oil filter for filtering impurities (mixtures) in oil circulating at a hydraulic pressure of 300 to 500 kPa. Such a filter medium for an automobile oil filter is, for example, a cylindrical type in which the upper end and the lower end of the cylinder are fixed after pleating the above-mentioned spunbonded non-woven fabric for the filter and making the whole cylindrical shape centering on the axis of the element. It can be an automobile oil filter.

The automobile oil filter of the present invention uses the above-mentioned filter medium for an automobile oil filter, and the automobile oil filter has a structure in which a filter element is housed in, for example, a metal or resin pressure resistant container. .. As the engine oil filtration method, for example, there are a full flow type that filters metal powder mainly generated by friction, a bypass type that removes carbon particles generated by incomplete combustion, and a combination type that uses both types in combination. The filter is particularly suitable for a combination type automobile oil filter that is widely used in automobiles in recent years.

As described above, the spunbonded non-woven fabric for a filter of the present invention has both a balance between the ability to collect contaminants in automobile engine oil and liquid permeability, has high rigidity, and is excellent in pleating workability. Since the non-woven fabric alone can be used as an automobile oil filter without using a thermosetting resin such as a phenol resin, it can be suitably used as an automobile oil filter having a small environmental load.

Next, the spunbonded nonwoven fabric for a filter of the present invention will be specifically described based on Examples. However, the present invention is not limited to these examples. In addition, in the measurement of each physical property, if there is no particular description, the measurement is performed based on the above method.

[Measuring method]
(1) Melting point of polyester (° C)
Using a differential scanning calorimeter "DSC-2 type" manufactured by PerkinElmer Co., Ltd., the temperature was measured under the condition of a temperature rise rate of 20 ° C./min, and the temperature at which an extreme value was given in the obtained melting endothermic curve was defined as the melting point.

(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)
The average single fiber diameter of the thermoplastic continuous filament was calculated by the above method using a scanning electron microscope of "VHX-D500" manufactured by KEYENCE CORPORATION.

(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) Rigidity and softness (mN) of spunbonded non-woven fabric for filters
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) Span-bonded non-woven fabric sheet for filter Cross-sectional thickness (mm)
As a scanning electron microscope, "VHX-D500" manufactured by KEYENCE CORPORATION was used, and the measurement was carried out by the above method.

(9) Pleat workability (points) of spunbonded non-woven fabric for filters
(1) The distance from the ridgeline of the apex of the pleated compact to the ridgeline of the next apex while cutting the spunbonded non-woven fabric for a filter to a width of 240 mm and heating the spunbonded non-woven fabric for a filter to 150 ° C. to compress it. The pleated fabric was obtained by pleating so that the thickness was 35 mm.
(2) 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 fused to both ends on the cylindrical shape. A pleated filter was prepared.
(3) The appearance of the pleated filter produced by 20 panelists was visually confirmed, and the pleated processability of the non-woven fabric 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 (There is no contact between the pleated parts, but the pleated shape is distorted.)
2 points (between 3 points and 1 point)
1 point (The pleated shape is distorted, and the pleated parts are in contact with each other.)

(10) Liquid permeability of spunbonded non-woven fabric for filter (sec / cm ³ )
(1) From the span-bonded non-woven fabric for the filter, a total of 5 samples having a length in the MD direction × a length in the CD direction of 100 mm × 100 mm are cut out at 5 points at intervals in the CD direction of the non-woven fabric. The CD direction is a direction orthogonal to the MD direction.
(2) A cylinder having a diameter of 2 cm is fixed on a spunbonded non-woven fabric for a filter, and 1 cm ³ of rapeseed oil having a viscosity of 43 mPa · sec (30 ° C.) is poured from the upper part of the cylinder.
(3) ^{The time until 1 cm 3 of} rapeseed oil completely soaked into the spunbonded non-woven fabric for the filter was measured, and the first decimal place was rounded off, and this value was taken as the liquid permeability.

The apparent density of the spunbonded non-woven fabric for the filter was calculated by the above method.

(11) 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 31 shown in FIG. 3 includes a sample holder 32 for setting the test sample M, a flow meter 33, a flow rate adjusting valve 34, a blower 35, a dust supply device 36, a switching cock 37, and a particle counter 38. To be equipped. The flow meter 33, the flow rate adjusting valve 34, the blower 35, and the dust supply device 36 are connected to the sample holder 32. The flow meter 33 is connected to the blower 35 via the flow rate adjusting valve 34. Dust is supplied to the sample holder 32 from the dust supply device 36 by the intake air of the blower 35. A particle counter 38 is connected to the sample holder 32, 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 37, respectively. First, three 15 cm × 15 cm samples are collected from an arbitrary part of the non-woven fabric, and the collected test sample M is set in the sample holder 32. The evaluation area of the test sample was 115 cm ² . In measuring the collection performance, a polystyrene 0.309U 10 wt% solution (manufactured by Nacalai Tesque, Inc.) was diluted with distilled water up to 200 times and filled in the dust supply device 36. The air volume is adjusted by the flow rate adjusting valve 34 so that the filter passing speed is 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 dust upstream and the number of dust downstream of the test sample M were measured with a particle counter 38 (manufactured by Rion Co., Ltd., KC-01D) in the range of dust particle size of 0.3 to 0.5 μm. .. 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).

(12) 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 39, 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 a 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. ^They were fused under the conditions to obtain a spunbonded non-woven fabric for a filter having a basis weight of 260 g / m 2. The sheet cross-sectional thicknesses 1-t _B / t _A and t _C / t _{D of the} obtained spunbonded non-woven fabric for filters are 0.67 and 0.68, respectively, the sheet thickness is 0.74 mm, and the rigidity in the MD direction is rigid. The softness was 53 mN. The results are shown in Table 1.

[Example 2]
A spunbonded non-woven fabric for a filter ^{having a basis weight of 260 g / m 2} was obtained under the same conditions as in Example 1 except that the linear pressure of the embossed roll was changed from 70 kg / cm to 60 kg / cm and fused. The sheet cross-sectional thicknesses of 1-t _B / t _A and t _C / t _{D of the} obtained spunbonded non-woven fabric for filter are 0.40 and 0.69, respectively, the sheet thickness is 0.70 mm, and the rigidity in the MD direction. The softness was 37 mN. The results are shown in Table 1.

[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 10.0 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 260 g / m ^{2 was obtained.} The sheet cross-sectional thicknesses 1-t _B / t _A and t _C / t _{D of the} obtained spunbonded non-woven fabric for filters are 0.67 and 0.69, respectively, the sheet thickness is 0.61 mm, and the rigidity in the MD direction is rigid. The softness was 42 mN. The results are shown in Table 1.

[Example 4]
A spunbonded non-woven fabric for a filter ^{having a basis weight of 260 g / m 2} was obtained under the same conditions as in Example 1 except that the temperatures of the upper and lower embossed rolls were both changed from 200 ° C. to 180 ° C. and fused. The sheet cross-sectional thicknesses 1-t _B / t _A and t _C / t _{D of the} obtained spunbonded non-woven fabric for filters are 0.53 and 0.66, respectively, the sheet thickness is 1.02 mm, and the rigidity in the MD direction is rigid. The softness was 57 mN. The results are shown in Table 1.

[Example 5]
The upper and lower embossed rolls are made from a pair of engraving rolls having a fused area ratio of 10% and an area of 1.6 mm ² per fused portion, and the fused area ratio is 6% and one fused portion. A spunbonded non-woven fabric for a filter ^{having a grain size of 260 g / m 2} was provided under the same conditions as in Example 1 except that the embossed rolls composed of a pair of engraving rolls having an area of 2.0 mm ^{2 were fused.} Obtained. The sheet cross-sectional thicknesses of 1-t _B / t _A and t _C / t _{D of the} obtained spunbonded non-woven fabric for filters are 0.79 and 0.66, respectively, the sheet thickness is 1.21 mm, and the rigidity in the MD direction. The softness was 73 mN. The results are shown in Table 1.

[Example 6]
The upper and lower embossed rolls are made from 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 18% and one fusion portion. A spunbonded non-woven fabric for a filter ^{having a grain size of 260 g / m 2} was provided under the same conditions as in Example 1 except that the embossed rolls composed of a pair of engraving rolls having an area of 0.7 mm ^{2 were fused.} Obtained. The sheet cross-sectional thicknesses of 1-t _B / t _A and t _C / t _{D of the} obtained spunbonded non-woven fabric for filters were 0.68 and 0.73, respectively, the sheet thickness was 0.73 mm, and the rigidity in the MD direction. The softness was 41 mN. The results are shown in Table 1.

[Example 7]
A spunbonded non-woven fabric for a filter ^{having a basis weight of 260 g / m 2} was obtained under the same conditions as in Example 1 except that the temperatures of the upper and lower embossed rolls were both changed from 200 ° C. to 180 and 210 ° C., respectively, and fused. It was. The sheet cross-sectional thicknesses of 1-t _B / t _A and t _C / t _{D of the} obtained spunbonded non-woven fabric for filters are 0.70 and 0.82, respectively, the sheet thickness is 0.96 mm, and the rigidity in the MD direction. The softness was 61 mN. The results are shown in Table 1.

[Example 8]
The upper and lower embossed rolls are made from 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 one fusion portion. A spunbonded non-woven fabric for a filter ^{having a grain size of 260 g / m 2} was provided under the same conditions as in Example 1 except that the embossed rolls composed of a pair of engraving rolls having an area of 0.5 mm ^{2 were fused.} Obtained. The sheet cross-sectional thicknesses 1-t _B / t _A and t _C / t _{D of the} obtained spunbonded non-woven fabric for filters are 0.61 and 0.45, respectively, the sheet thickness is 0.61 mm, and the rigidity in the MD direction is rigid. The softness was 25 mN. 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 for filters of Examples 1 to 8 have a vertical rigidity of 20 mN or more, a grain CV value of 11.0% or less, and a pressure. The loss was 50 Pa or less, the collection efficiency was 50% or more, the rigidity and the uniformity of the texture were excellent, and the spunbonded non-woven fabric for a filter showed good characteristics. The results of pleating workability and liquid permeability were also good, with the pleating workability being 83 points or more and the liquid permeability being 23 seconds / cm ³ or less.

[Comparative Example 1]
In the manufacturing process of Example 1, the sheet obtained in the temporary fusion step was once wound up between the step of temporary fusion of the collected fiber webs and the step of partial fusion using an embossed roll. After that, the sheet was cooled to room temperature and changed to provide a step of feeding the sheet to the embossed roll, that is, the step of partial fusion using the embossed roll was not performed following the temporary fusion step. The embossed roll is an embossed roll consisting of a pair of engraving rolls having a fusion area ratio of 18% and an area of 0.7 mm ² per fused portion, except that the upper and lower temperatures are each fused at 240 ° C. Under the same conditions as in Example 1, a spunbonded non-woven fabric for a filter ^{having a grain size of 260 g / m 2 was obtained.} The sheet cross-sectional thicknesses 1-t _B / t _A and t _C / t _{D of the} obtained spunbonded non-woven fabric for filters are 0.32 and 0.25, respectively, the sheet thickness is 0.82 mm, and the rigidity in the MD direction is rigid. The softness was 18 mN. The results are shown in Table 2.

[Comparative Example 2]
While the discharge rate and spinning speed were changed so that the average single fiber diameter was 29.2 μm, the speed of the net conveyor was changed to make the texture the same as in Example 1, and the fused area ratio was 18% and fused. An embossed roll consisting of a pair of engraving rolls having an area of 0.7 mm ² per landing portion has a texture of 260 g / g under the same conditions as in Comparative Example 1 except that the upper and lower parts are fused at a temperature of 205 ° C. to obtain a filter for spunbond nonwoven m ^2. The sheet cross-sectional thicknesses of 1-t _B / t _A and t _C / t _{D of the} obtained spunbonded non-woven fabric for filters are 0.45 and 0.57, respectively, the sheet thickness is 1.01 mm, and the rigidity in the MD direction. The softness was 43 mN. The results are shown in Table 2.

[Comparative Example 3]
The upper and lower embossed rolls are made of a pair of engraving rolls having a fused area ratio of 10% and an area of 1.6 mm ² per fused portion, and the fused area ratio is 16% and one fused portion is provided. For a filter with a ^{grain size of 260 g / m 2 under} the same conditions as in Example 1 except that the embossed rolls composed of a pair of engraving rolls having an area per area of 0.5 mm ^{2 were heat-sealed at 180 ° C. on both the top and bottom.} A spunbonded non-woven fabric was obtained. The sheet cross-sectional thicknesses of the obtained spunbonded non-woven fabric for filters 1-t _B / t _A and t _C / t _D were 0.57 and 0.20, respectively, the sheet thickness was 0.64 mm, and the hardness in the MD direction was rigid. The degree was 12 mN. The results are shown in Table 2.

[Comparative Example 4]
The upper and lower embossed rolls are made from a pair of engraving rolls having a fused area ratio of 10% and an area of 1.6 mm ² per fused portion, and the fused area ratio is 24% and one fused portion. A spunbonded non-woven fabric for a filter ^{having a grain size of 260 g / m 2} was provided under the same conditions as in Example 1 except that the embossed rolls composed of a pair of engraving rolls having an area of 0.5 mm ^{2 were fused.} Obtained. The sheet cross-sectional thicknesses 1-t _B / t _A and t _C / t _{D of the} obtained spunbonded non-woven fabric for filters are 0.65 and 0.55, respectively, the sheet thickness is 0.62 mm, and the rigidity in the MD direction is rigid. The softness was 18 mN. The results are shown in Table 2.

The characteristics of the obtained non-woven fabric are as shown in Table 2, but in Comparative Example 1, the sheet cross-sectional thickness (1-t _B / t _A ) was low and the liquid permeability was inferior. In Comparative Example 2, the average single fiber diameter was large, the thickness was large, and the liquid permeability was inferior. In Comparative Example 3, the sheet cross-sectional thickness (t _C / t _D ) was low, and the pleating workability was inferior. When embossing was performed with a fused area ratio of 24% in Comparative Example 4, the thickness was thin, the rigidity and softness were low, and the pleating workability was inferior.

11 Convex part 12 Concave part 21 Filter material for automobile oil filter 22 Mountain part 23 Valley part 24 Arrow indicating MD direction (broken line arrow)
25 Arrow indicating the CD direction (dashed arrow)
U Evaluation unit M Test sample 31 Test system 32 Sample holder 33 Flow meter 34 Flow control valve 35 Blower 36 Dust supply device 37 Switching cock 38 Particle counter 39 Pressure gauge

Claims (6)

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.
It has a non-fused convex portion and a fused concave portion.
The average single fiber diameter constituting the spunbonded non-woven fabric for the filter is 8.0 μm or more and 15.0 μm or less.
The rigidity in the MD direction is 20 mN or more and 80 mN or less.
In the cross section of the non-woven fabric, the thickness t _{A from one surface of the convex portion to the other surface, the thickness t B} from one surface of the concave portion to the other surface, and one surface of the convex portion to one surface of the concave portion. A spunbonded non-woven fabric for a filter having a relationship represented by the following formulas (1) and (2), where the distances are t _C and t _D (t _C <t _{D), respectively.}
0.35 ≤ 1-t _B / t _A <1.00 ... (1)
0.3 <t _C / t _D <1.0 ... (2) 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 nonwoven fabric for a filter according to claim 1 or 2, wherein the ratio of the fused area of the recess is 5% or more and 20% or less. The spunbonded nonwoven fabric for a filter according to any one of claims 1 to 3, which is a spunbonded nonwoven fabric for an automobile oil filter. A filter medium for an automobile oil filter using the spunbonded non-woven fabric for a filter according to any one of claims 1 to 4. An automobile oil filter using the filter medium for an automobile oil filter according to claim 5.

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