JP2017131853A - Manufacturing method of nonwoven fabric filter material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonwoven fabric filter material of a filter material capable of effectively restraining dust slipping-out by pulsation.SOLUTION: A nonwoven fabric filtration material 1 of a multilayer structure is manufactured so as to adjacently include a first nonwoven fabric layer 12 positioned on the upstream side and s span bond nonwoven fabric layer 13 positioned on the downstream side. The first nonwoven fabric layer 12 is constituted with fiber being 5-20 μm in an average fiber diameter as a main body, and porosity is set to 87-95%. Integration of the first nonwoven fabric layer 12 and a span bond layer 13 is executed so as to include a needle punch process of driving a needle N so as to penetrate through both layers and a binder processing process to at least the first nonwoven fabric layer 12 after the needle punch process.SELECTED DRAWING: Figure 4

Description

The present invention relates to a method for producing a nonwoven fabric filter material. It is related with the manufacturing method of the nonwoven fabric filter material especially used for the filtration of the dust in air.

Nonwoven fabric filter materials are used for air filtration as filter materials for air cleaners such as internal combustion engines and fuel cells used in automobiles and the like. In such applications, it is required to efficiently remove fine dust from a large amount of air. Nonwoven filter media are required to have high cleaning efficiency, long life that can remove dust without clogging for a long period of time, and compactness that can exhibit sufficient filtration performance in a limited space. .

Furthermore, when filtering the combustion air supplied to the internal combustion engine by the non-woven filter material, an intake air pulsation corresponding to the intake cycle of the internal combustion engine is generated in the air flow passing through the filter material. It is necessary to endure and hold the trapped air dust. If the holding is insufficient, so-called dust omission occurs in which dust moves to the downstream side and permeates through the nonwoven fabric filtering material due to intake pulsation.

For example, Patent Literature 1 discloses a nonwoven fabric filtering material composed of a plurality of nonwoven fabric layers not impregnated with oil, and the nonwoven fabric filtering material on the downstream side is smaller than the upstream nonwoven fabric layer in terms of the space ratio of the nonwoven fabric filtering material. Of the downstream nonwoven fabric layer in the range of 85 to 92%, the average fineness of the fibers constituting the downstream nonwoven fabric layer is 3 dtex or less, and the fibers constituting the upstream nonwoven fabric layer It is disclosed that the average fineness is 3 dtex or more. According to the nonwoven fabric filtering material, dust permeation due to intake pulsation is suppressed, and an effect that carbon dust cleaning efficiency and carbon dust retention amount can be maintained well is obtained.

JP 2005-349389 A

However, even with the nonwoven fabric filtering material of Patent Document 1, it is still difficult to completely prevent dust removal against the intake pulsation, and a nonwoven fabric filtering material that can more effectively suppress dust removal due to pulsation has been demanded. Yes. Even if it tries to suppress dust removal simply, it is difficult to achieve both ventilation resistance and life.
An object of the present invention is to provide a filtering material nonwoven fabric filtering material that can effectively suppress dust removal due to pulsation.

The inventor has conceived that a spunbond nonwoven fabric layer is provided on the downstream side of the nonwoven fabric filtering material, and dust that escapes from the upstream nonwoven fabric layer due to pulsation is captured by the spunbond nonwoven fabric layer. That is, the idea was to integrate a spunbonded nonwoven fabric downstream of the nonwoven fabric filter material.

However, it has been difficult to integrate with other nonwoven fabric layers while maintaining the filtration function (dust capturing performance) of the spunbond nonwoven fabric. For example, although integration was attempted using heat-adhesive fibers, the bond strength was weak, and the spunbonded nonwoven fabric was easily peeled and pulsated while the integrated nonwoven filter material was folded and used. It was not a nonwoven filter material that could be used under such severe conditions.

We considered using the needle punch method to integrate the nonwoven fabric layer. However, when needle punching is performed on a spunbond nonwoven fabric, a hole is formed in the portion through which the needle has passed. It becomes full, and the filtration function of the spunbond layer is impaired. This makes it impossible to expect the effect of suppressing dust removal due to pulsation by the spunbond layer.

The inventor conducted further studies, and as a result, in the nonwoven fabric filter material having a multilayer structure, a spunbond layer was provided on the downstream side of the nonwoven fabric layer having a specific fiber configuration, and then the needle punching step and the subsequent binder treatment step were performed. If it did, it discovered that a spunbonded nonwoven fabric layer could be integrated with another nonwoven fabric layer, improving the performance which hold | maintains dust against inhalation pulsation, and completed this invention.

The present invention relates to a method for producing a nonwoven fabric filter material having a multilayer structure, in which a first nonwoven fabric layer located on the upstream side and a spunbond nonwoven fabric layer located on the downstream side are included adjacent to each other. The first nonwoven fabric layer is mainly composed of fibers having an average fiber diameter of 5 to 20 μm, and the first nonwoven fabric layer has a space ratio of 87 to 95%. And the spunbond layer include a needle punching step in which a needle is pierced through both layers, and a binder treatment step for at least the first nonwoven fabric layer after the needle punching step. It is a manufacturing method of the nonwoven fabric filter material characterized by this (1st invention).

In the first invention, in the needle punching process, at least a part of the needle that is struck through the first nonwoven fabric layer and the spunbond layer is struck from the first nonwoven fabric layer side toward the spunbond layer side. It is preferable (the second invention). In the first invention or the second invention, it is preferable that the spunbond layer is positioned on the most downstream side in the nonwoven fabric filtering material (third invention). Moreover, in 3rd invention, it is preferable to provide the 2nd nonwoven fabric layer whose spatial rate is higher than a 1st nonwoven fabric layer in an upstream rather than a 1st nonwoven fabric layer (4th invention).

According to the nonwoven fabric filtering material manufacturing method of the first invention, the spunbond layer is well integrated with the upstream nonwoven fabric layer. In addition, according to the nonwoven fabric filtering material obtained by the first invention, the spunbond layer effectively captures dust transmitted through the pulsation from the nonwoven fabric layer disposed upstream, and dust removal due to the intake pulsation is suppressed. The

Moreover, according to the nonwoven fabric filter material manufacturing method of the second invention, it is easy to adjust the space ratio of the first nonwoven fabric layer, and the effect of suppressing dust removal due to pulsation is more effectively exhibited.
In addition, the nonwoven fabric filter material obtained by the third invention is an upstream nonwoven fabric layer, and while the cleaning efficiency and life of the filter material are increased, the spunbond nonwoven fabric layer provided on the most downstream side suppresses dust removal due to pulsation. The roles can be shared, and the life and cleaning efficiency of the nonwoven fabric filter material can be improved in a well-balanced manner while suppressing the removal of dust from the suction pulsation of the nonwoven fabric filter material.
Furthermore, the non-woven filter medium obtained by the fourth invention can improve the life and cleaning efficiency of the filter medium in a well-balanced manner.

It is a schematic diagram which shows the cross-section of the nonwoven fabric filter material of 1st Embodiment of invention. It is a schematic diagram which shows the structure of the air cleaner element using a nonwoven fabric filter material. It is a schematic diagram which shows the manufacturing process of the nonwoven fabric filter material of 1st Embodiment. It is a schematic diagram which shows the example of the change which arises in a nonwoven fabric layer by a needle punch. It is a schematic diagram which shows the other example of the change which arises in a nonwoven fabric layer by a needle punch.

Hereinafter, embodiments of the invention will be described with reference to the drawings, taking as an example a nonwoven fabric filter material that can be used as a filter material of an air cleaner for filtering air supplied to an internal combustion engine (engine) of an automobile. The invention is not limited to the individual embodiments shown below, and can be carried out by changing the form.

Drawing 1 is a mimetic diagram showing the section structure of nonwoven fabric filter material 1 of a 1st embodiment concerning the invention. The nonwoven fabric filtering material of this embodiment is a sheet-like nonwoven fabric, and when used for an air cleaner of an automobile engine, it is usually used as an air cleaner element 2 fixed to a frame in a folded state. FIG. 2 is a cross-sectional view schematically showing the structure of the air cleaner element. The air cleaner element 2 is formed by surrounding a folded nonwoven fabric filtering material 1 with a frame body 21 so as to be integrated, and providing sealing members 22, 22 around the frame body 21. As a specific configuration of the air cleaner element, a known configuration can be adopted and is not particularly limited. The air cleaner element 2 may be configured without the frame body 21 or the sealing material 22.

The nonwoven fabric filtering material 1 is a nonwoven fabric filtering material having a multilayer structure in which a plurality of nonwoven fabric layers are laminated. And it has the spun bond nonwoven fabric layer 13 as one of the nonwoven fabric layers. As shown by the arrows in FIG. 1, the flow of the air flow when the nonwoven fabric filter material is used, the layer to be used on the upstream side and the layer to be used on the downstream side are predetermined in this nonwoven fabric filter material. Yes. On the upstream side of the spunbond layer 13, nonwoven fabric layers 11 and 12 that are dry layers are provided. In the nonwoven fabric filtering material 1, most of the dust is captured by the nonwoven fabric layers 11 and 12 which are these dry layers. In the present embodiment, in particular, the spunbond layer 13 is provided so as to be located on the most downstream side, and the layers are integrated with each other.

The nonwoven fabric layers 11 and 12 which are dry layers will be described. The nonwoven fabric filtering material 1 of this embodiment has the rough layer part 11 located in an upstream, and the dense layer part 12 located in a downstream. The coarse layer portion 11 has a lower bulk density of the nonwoven fabric layer than the dense layer portion 12. In other words, the coarse layer portion 11 has a higher non-woven fabric layer space ratio than the dense layer portion 12. That is, the nonwoven fabric filtering material 1 has a coarse layer portion 11 on the upstream side and a dense layer portion 12 on the downstream side, and has a density gradient. In addition, as will be described later, the coarse layer portion 11 is not essential.

Here, the space ratio of the nonwoven fabric layer is a value indicating the volume of space per unit volume of the nonwoven fabric layer (volume obtained by subtracting the volume occupied by fibers from the volume occupied by the whole nonwoven fabric layer). That the nonwoven fabric layer is coarse means that the space ratio is large, and that the nonwoven fabric layer is dense means that the space ratio is small. A preferable space ratio of the coarse layer portion 11 is about 90 to 99.5%. Moreover, the preferable space ratio of the dense layer part 12 is about 80 to 95%. In the present embodiment, the spatial ratio of the coarse layer portion 11 is 96.6%, and the spatial ratio of the dense layer portion 12 is 93.4%.

The basis weight of the nonwoven fabric layer of the nonwoven fabric filtering material 11 and the dense layer portion 12 is not particularly limited, but the basis weight of the coarse layer portion 11 is about 40 to 200 g / square meter, and the basis weight of the dense layer portion 12 is 70 to 300 g. / M 2 is preferable. In the present embodiment, the basis weight of the coarse layer portion 11 is 75 g / square meter, and the basis weight of the dense layer portion 12 is 110 g / square meter.

The nonwoven fabric filtering material 1 may have layers other than the rough layer part 11 and the dense layer part 12 which are dry layers. For example, a prefilter layer may be provided on the upstream side of the coarse layer portion 11. Alternatively, an intermediate layer may be provided between the coarse layer portion 11 and the dense layer portion 12. It is not essential to provide these other layers.
Or you may comprise the nonwoven fabric layer upstream of a spunbond layer with a single nonwoven fabric layer.

Here, the dry layer is a layer in which the nonwoven fabric layer is not substantially impregnated / coated with oil. When these layers are dry layers, volume filtration that retains a large amount of dust inside these nonwoven fabric layers is realized, and the dust trapping performance is improved. The nonwoven fabric layers 11 and 12 may be so-called viscous layers, but these layers are preferably dry layers from the viewpoint of fine particle dust capturing performance.

Known techniques can be used for the material of the fibers constituting the coarse layer portion 11 and the dense layer portion 12, the average fiber diameter, the degree of crimping, the non-woven fabric method, and the like. A core-sheath fiber or a composite fiber may be used. When the rough layer portion and the dense layer portion are provided as in the nonwoven fabric filtering material of the present embodiment, the coarse layer portion is compared with each other, the coarse layer portion is configured with a high space ratio with thick fibers, and the dense layer portion 12 is thin. It is preferable that the fiber is configured to have a low space ratio.

The dense layer portion 12 will be described in more detail. The nonwoven fabric filter material of 1st Embodiment is a nonwoven fabric filter material of a multilayer structure, and the dense layer part 12 and the spunbond nonwoven fabric layer 13 are contained in the nonwoven fabric filter material 1 adjacently. The dense layer portion 12 is located on the upstream side of the spunbond nonwoven fabric layer 13, and the spunbond nonwoven fabric layer 13 is located on the downstream side of the dense layer portion 12.
The dense layer portion (also referred to as a first nonwoven fabric layer) 12 is mainly composed of fibers having an average fiber diameter of 5 to 20 μm. The average fiber diameter of the main fibers constituting the dense layer portion is preferably 7 to 15 μm. Further, the space ratio of the dense layer portion 12 is set to 87 to 95%. The space ratio of the dense layer portion 12 is preferably 89 to 94%. In the present embodiment, the average fiber diameter of the fibers constituting the dense layer portion is 14 μm, and the space ratio of the dense layer portion is 93.4%.

Here, the average fiber diameter of the fibers will be described. When the fiber is a single material / type, the average fiber diameter is directly calculated from the fineness of the fiber, such as denier and decitex, and the density of the material that makes up the fiber, assuming that the fiber has a circular cross section. It is the fiber diameter. When there are multiple types of fibers in the fiber group for which the average fiber diameter is to be obtained, or when the fibers are composed of multiple constituent materials, the average fiber diameter is determined from the fineness and density for each fiber and constituent material. In addition, a value obtained by taking a weighted average of the average fiber diameters according to the blending ratio of each fiber and constituent material may be handled as the average fiber diameter. In addition, when the fiber has an irregular cross section or a hollow structure, the fiber width is measured at a plurality of positions from a micrograph of the fiber, and an arithmetic average of the widths may be treated as the average fiber diameter of the fiber.

The spunbond layer 13 will be described. The spunbond layer 13 is a layer made of a spunbond nonwoven fabric provided on the downstream side of the coarse layer portion 11 and the dense layer portion 12. The spunbond layer 13 functions to stop dust transmitted from the coarse layer portion 11 and the dense layer portion 12 by the intake pulsation. Preferably, the basis weight of the spunbond layer is 5 to 50 g / square meter. Particularly preferably, the basis weight of the spunbond layer is 10 to 30 g / square meter.

The spunbond layer 13 may be embossed in a form in which a plurality of dots are scattered. By embossing, the fibers are thermally welded at the dot portions, and the dust collection performance of the spunbond layer can be enhanced. The shape of the dot may be circular or rectangular, and is not particularly limited. Dots of different sizes may be interspersed. Note that embossing is not essential.

The material used for the spunbond layer 13 is typically a chemical fiber material that can be thermally welded. Typical chemical fiber materials include polyester resin such as polyethylene terephthalate (PET) resin, polyamide resin such as nylon 6, acrylic resin such as polyacrylonitrile resin, and polyolefin resin such as polypropylene resin. it can. A core-sheath fiber having a PET resin on the inside and a polyethylene resin on the outside may be used for the spunbond layer.

The average fiber diameter of the fibers contained in the spunbond layer 13 is preferably 5 to 30 μm. The average fiber diameter is particularly preferably 8 to 25 μm.

In the present embodiment, the spunbond layer 13 is formed by embossing PET fibers having an average fiber diameter of 15 μm as a spunbond nonwoven fabric with a basis weight of 15 g / square meter so that dots are provided at a density of 20 pieces / square centimeter. ing.

The manufacturing method of the nonwoven fabric filter material 1 of 1st Embodiment is demonstrated. The nonwoven fabric filtering material 1 includes a first step of laminating each fiber assembly (web or spunbond nonwoven fabric) to be the coarse layer portion 11, the dense layer portion 12, and the spunbond layer 13, and a needle punch on the laminate. And a non-woven fabric manufacturing method including a second step of performing a binder treatment and integrating them.

The manufacturing process of the nonwoven fabric filter material 1 is schematically shown in FIG.
In the first step, first, the raw fiber constituting the coarse layer portion is opened and blended, and the coarse layer web 11W to be the coarse layer portion is obtained through the metering and cotton feeding steps. Similarly, the raw material fibers constituting the dense layer portion are opened and mixed, and a dense layer web 12W to be the dense layer portion is obtained through a metering and cotton feeding process. As the spunbond layer 13, a spunbond nonwoven fabric 13 produced in advance can be used (FIG. 3A). Next, the dense layer web 12W to be the dense layer portion and the coarse layer web 11W to be the coarse layer portion are laminated in this order on the spunbond nonwoven fabric 13 to be the spunbond layer (FIG. 3B). . The above is the first step.

Next, the second step is performed. In the second step, first, the obtained laminate is subjected to a needle punching step, and the layers of the laminate are integrated with each other while controlling the coarse layer portion and the dense layer portion to have a predetermined space ratio ( FIG. 3 (c)). In the needle punching process, the needles are struck so that at least some of the needles N and N penetrate the spunbond layer 13 and the first nonwoven fabric layer (dense layer portion 12).
Preferably, at least a part of the needle that is struck so as to penetrate both layers is struck toward the spunbond layer 13 from the side of the first nonwoven fabric layer (dense layer portion 12).
It should be noted that some of the needles penetrating both layers may be struck from the spunbond layer 13 side toward the first nonwoven fabric layer (dense layer portion 12) side.

The needle punching process may include a needle that does not penetrate both the spunbond layer 13 and the first nonwoven fabric layer (dense layer portion 12). For example, a needle that penetrates only the coarse layer portion 11 and the dense layer portion 12 or a needle that penetrates only the coarse layer portion 11 may be included in the needle punching process.
By passing through the needle punching process, the constituent fibers of each layer are entangled with each other and the layers are tightly integrated, so that the coarse layer web 11W and the dense layer web 12W are the coarse layer portion 11 and the dense layer portion having a predetermined space ratio and thickness. 12 (FIG. 3C).

Subsequent to the needle punching step, a binder treatment for immersing the non-woven filter material in a binder solution is performed to fix the intersections of the fibers. The binder to be used is not particularly limited. When fibers that require heat treatment such as hot melt fibers and core-sheath fibers are included, heat treatment may be performed. The binder treatment may be performed on the entire nonwoven fabric, but at least the binder treatment is performed so that the dense layer portion (first nonwoven fabric layer) 12 is immersed in the binder liquid.

Subsequent to the needle punching process, prior to the binder treatment or after the binder treatment, the surface of the nonwoven fabric filtering material on the side of the spunbond layer may be subjected to roller treatment or calendar treatment.
By passing through such an integration process including the needle punching process and the binder processing process, the nonwoven fabric filtering material 1 in which the coarse layer part 11, the dense layer part 12, and the spunbond layer 13 are firmly integrated is obtained.

The effect | action and effect of the nonwoven fabric filter material 1 obtained by the said manufacturing method are demonstrated.
When the dense layer portion 12 and the spunbond layer 13 are integrated, there is a needle punching process in which a needle is pierced through both layers so that the constituent fibers of the spunbond layer and the dense layer portion are entangled with each other. Thus, the spunbond layer 13 is firmly integrated as a part of the nonwoven fabric filtering material. That is, in the obtained nonwoven filter material 1, the spunbond layer 13 is difficult to peel off.

Further, in the above manufacturing method, after the needle punching process in which the needle N is hit so as to penetrate through the spunbond layer 13 and the dense layer portion 12, at least a binder treatment is performed on the first nonwoven fabric layer (dense layer portion). Thus, dust removal due to intake air pulsation in the obtained non-woven filter material 1 is suppressed.

According to the common technical knowledge so far, if the needle punching process is performed on the spunbond layer, the spunbond layer becomes full of holes, and the filtration function can no longer be expected. On the other hand, according to the manufacturing method described above, the integrated spunbond layer exerts a filtration function despite the needle punching process, and dust removal due to intake pulsation is suppressed. The reason for this is that when the needle punch and the binder treatment are combined as in the above manufacturing method, the following fiber arrangement structure changes in the spunbond layer 13 and the dense layer portion 12, and the spunbond layer has a hole. Presumably because the dust is less likely to leak.

FIG. 4 schematically shows the state of the spunbond layer 13 and the dense layer portions (12W, 12) before and after the needle punching process. For simplicity, other layers are not shown. The left diagram of FIG. 4 shows the front of the needle punching process, and the center diagram of FIG. 4 schematically shows the fiber arrangement structure after the needle punching process. When the needle N is struck so as to penetrate both layers toward the spunbond layer 13 side from the dense layer portion (first nonwoven layer) 12 side, a part of the fibers constituting the dense layer portion 12 is spunbonded. It is drawn to the side of the layer and entangled with the constituent fibers of the spunbond layer. In addition, the spunbond layer 13 has a hole in a portion where the needle has passed, but the constituent fiber of the dense layer portion 12 is pulled at the tip of the needle N, and the hole portion opened in the spunbond layer 13 by the needle. Therefore, the constituent fibers of the dense layer portion 12 are concentrated near the hole opened in the spunbond layer.

As a result, as shown in the center diagram of FIG. 4, a hole is opened in the spunbond layer at the site where the needle N is struck and pulled out, while the dense layer near the hole has a spunbond layer. A portion C where the constituent fibers of the dense layer portion are densely formed is formed so as to cover the hole. In this part, the constituent fibers are arranged more densely than the other part of the dense layer part, and for example, it is formed in a lid shape or a test tube opened upstream.

When the binder treatment is performed on at least the dense layer portion after the needle punching process, a lot of binder liquid is deposited on the portion C where the constituent fibers are densely packed, and the portion C is a portion where the fibers are dense and solidified by the binder. Become.
Such a portion C is formed so as to cover and cover each of the perforated portions of the spunbond layer by covering the upstream side of the hole. Therefore, even if the dust trapped in the coarse layer portion 11 or the dense layer portion 12 tries to move due to pulsation, the moving dust does not pass through the densely consolidated portion C and is difficult to reach the hole of the spunbond layer 13. . Therefore, although the spunbond layer 13 has a hole due to the needle punch, the spunbond layer 13 maintains the filtration function, and the presence of the spunbond layer has the effect of suppressing dust removal due to pulsation. Arise.

Further, when the needle N penetrating both layers is struck from the side of the dense layer portion 12 toward the spunbond layer as in the manufacturing method of the present embodiment, the thickness and the space ratio of the dense layer portion 12 are reduced. From the viewpoint of facilitating control and enhancing the cleaning efficiency and life of the resulting nonwoven fabric filter material, a more preferable nonwoven fabric filter material can be produced.

When the needle N penetrating both layers is struck from the dense layer portion 12 side toward the spunbond layer, particularly after the needle punching process, prior to the binder treatment or after the binder treatment, It is preferable to perform roller treatment or calendar treatment on the surface of the non-woven filter medium on the bond layer side. When the roller process or the calendar process is performed, as shown in the diagram on the right side of FIG. 4, the holes opened in the spunbond layer are reduced, and the constituent fibers of the dense layer portion protruding from the spunbond layer are pushed back. As a result, the fiber density of the portion C where the fibers formed in the vicinity of the hole of the spunbond layer are concentrated is further increased, and it becomes difficult for the dust to pass through this portion, and the effect of suppressing the dust omission due to pulsation is more conspicuous. It will be a thing.

Even if the needle penetrating both layers is struck from the spunbond layer 13 side toward the dense layer portion 12 side, the effect of suppressing dust detachment due to pulsation is produced.
FIG. 5 schematically shows the state of the spunbond layer 13 and the dense layer portions (12W, 12) before and after the needle punching process. The diagram on the left side of FIG. 5 shows before the needle punching process, and the diagram on the right side of FIG. 5 schematically shows the fiber arrangement structure after the needle punching process. When the needle N is struck so as to penetrate both layers from the spunbond layer 13 side toward the dense layer portion 12 side, the spunbond layer 13 has a hole in the portion through which the needle has passed, and the spunbond. Part of the fibers constituting the layer is drawn toward the dense layer portion 12 and entangled with the constituent fibers of the dense layer portion. Further, the constituent fibers of the dense layer portion 12 are also pulled toward the coarse layer portion 11 by the needle N and are drawn into the vicinity of the hit needle N.

As a result, as shown in the diagram on the right side of FIG. 5, a hole is opened in the spunbond layer at the site where the needle N is drawn and pulled out, while the dense layer portion covers the hole of the spunbond layer. In addition, a portion C in which the constituent fibers of the dense layer portion are concentrated in a cap shape is generated. In this portion, the constituent fibers are arranged more densely than the other portions of the dense layer portion.

When the binder treatment is performed on the dense layer portion after the needle punching step, a lot of binder liquid is applied to the portion C where the constituent fibers are densely packed, and the portion C becomes a portion where the fibers are dense and solidified by the binder. .
Such a portion C is formed so as to cover and cover each of the perforated portions of the spunbond layer with a cap on the upstream side of the hole. Therefore, even if the dust trapped in the coarse layer portion 11 or the dense layer portion 12 tries to move due to pulsation, the moving dust does not pass through the densely consolidated portion C and is difficult to reach the hole of the spunbond layer 13. . Therefore, although the spunbond layer 13 has a hole due to the needle punch, the spunbond layer 13 maintains the filtration function, and the presence of the spunbond layer has the effect of suppressing dust removal due to pulsation. Arise.

Furthermore, if the spunbond layer is positioned on the most downstream side of the nonwoven fabric filter material, the nonwoven fabric filter material's basic performance, such as cleaning efficiency and life against general dust and fine particle dust, in the nonwoven fabric layer upstream of the spunbond layer. It is possible to effectively suppress the pulsation in the most downstream spunbond layer, improving the life of the non-woven filter material and improving the cleaning efficiency in a well-balanced manner while suppressing the removal of dust against the intake pulsation. it can.

Furthermore, like the nonwoven fabric filtering material of the said embodiment, the 2nd nonwoven fabric layer (coarse layer part) whose space rate is higher than a 1st nonwoven fabric layer upstream from a 1st nonwoven fabric layer (dense layer part). Can improve the basic performance of non-woven filter media such as cleaning efficiency and life against general dust and fine particle dust, while suppressing the loss of dust against intake pulsation, especially in a well-balanced non-woven filter medium life And cleaning efficiency can be increased.

The invention is not limited to the embodiment described above, and can be implemented with various modifications. Although other embodiments of the invention will be described below, in the following description, portions different from the above-described embodiment will be mainly described, and detailed descriptions of the same portions will be omitted.

There are no particular restrictions on the number and density of needles N that are pierced through the spunbond layer and the dense layer, and the needles are struck to the extent that they are integrated and the spatial rate and thickness of each layer are adjusted accurately. That's fine.
Further, when the needle penetrating both layers is struck from the spunbond layer toward the dense layer portion, the needle N preferably protrudes from the dense layer portion while penetrating both layers. It is preferable that the punch is struck to a depth that does not occur. This is because the dense portion C covering the hole of the spunbond layer is more reliably formed in the dense layer portion 12.

Further, it is not necessary to perform all of the needle punching process with the needle N which is struck so as to penetrate the spunbond layer and the dense layer portion. For example, when manufacturing a nonwoven fabric filtering material having a coarse layer portion and a dense layer portion as in the first embodiment, first, needle punching is performed from the coarse layer portion web 11W toward the dense layer portion web 12W. Then, the both of the coarse layer portion 11 and the dense layer portion 12 are integrated while adjusting the space ratio and the like, and then the needle N is hit in the opposite direction, that is, from the spunbond layer toward the dense layer portion. And the dense layer portion may be integrated.

In addition, in order to integrate the nonwoven filter material and maintain the fiber arrangement structure, means other than needle punching or binder treatment may be used in combination. For example, a core-sheath fiber containing a low-temperature melting component may be blended in the coarse layer portion, or a hot press treatment or the like may be used in combination with the binder treatment.

Moreover, according to the use etc. with which a nonwoven fabric filter material is used, you may perform a water-repellent process and an oil-repellent process to the nonwoven fabric filter material 1 as needed.

Examples of the present invention will be described below. In addition, this invention is not limited by these Examples.
Further, in the examples and comparative examples shown below, the filter material in any of the examples is substantially the same in the configuration of the fiber material, thickness, basis weight, etc., which is not described as different, and is used for the test. The shape of the filter element formed at the time and the specifications of the folding are the same. Tables 1 and 2 show fiber configurations and performance evaluation results of Examples and Comparative Examples.

Example 1
Example 1 is the nonwoven fabric filtering material 1 described as the first embodiment. The coarse layer portion 11 is made of PET fiber, has a basis weight of 75 g / square meter, a spatial rate of 96.6%, and the average fiber diameter of the fibers constituting the coarse layer portion 11 is 21 μm. The dense layer portion 12 is made of PET fiber, has a basis weight of 110 g / square meter, a space ratio of 93.4%, and an average fiber diameter of fibers constituting the dense layer portion 12 is 14 μm. The nonwoven fabric filtering material 1 of Example 1 has a spunbond nonwoven fabric layer 13 on the downstream side of the dense layer portion 12, and the spunbond nonwoven fabric layer 13 has a basis weight of 15 g / square meter, an average fiber diameter of 15 μm, and an embossed finish. The density of the dots is adjusted to 20 pieces / square centimeter.
In the manufacture of the nonwoven fabric filter material of Example 1, the dense layer portion (first nonwoven fabric layer) 12 and the spunbond layer were integrated by a needle punching step and a subsequent binder treatment step. In the needle punching process, a needle that is struck through the dense layer portion 12 and the spunbond layer 13 is struck from the dense layer portion (first layer) side toward the spunbond layer.

(Example 2)
Compared to Example 1, the dense layer portion (first non-woven fabric layer) was changed so that the space ratio was 91.2% and the average fiber diameter was 18 μm, and the other non-woven filter material was the same as Example 1. Obtained.

(Example 3)
For Example 1, the direction in which the needle penetrating the dense layer part (first nonwoven layer) and the spunbond layer is changed from the spunbond layer side to the dense layer (first nonwoven layer) side, The other was the same as in Example 1 to obtain a nonwoven filter material.

(Comparative Example 1)
In contrast to Example 1, except that there was no binder treatment step after the needle punching step, a nonwoven fabric filter material similar to Example 1 was obtained except for the point.

(Comparative Example 2)
For Example 1, the integration of the dense layer portion (first nonwoven layer) and the spunbond layer is performed using an adhesive sheet containing a heat-meltable fiber without performing a needle punching process or a binder processing process, A nonwoven fabric filtering material similar to that in Example 1 was obtained.

(Comparative Example 3)
For Example 1, the dense layer part (first nonwoven layer) and the spunbond layer were integrated by a binder treatment process without performing the needle punching process, and the other nonwoven fabric filtering material was the same as in Example 1. Obtained.

(Comparative Example 4)
Compared to Example 1, the dense layer portion (first non-woven fabric layer) was changed so that the space ratio was 94.5% and the average fiber diameter was 25 μm, and the other non-woven fabric filter material was the same as Example 1. Obtained.

(Comparative Example 5)
Compared to Example 1, the dense layer portion (first non-woven fabric layer) was changed so that the space ratio was 97.1% and the average fiber diameter was 16 μm, and the other non-woven fabric filter material was the same as Example 1. Obtained.

(Comparative Example 6)
Compared to Example 1, the spunbond layer was eliminated, and a non-woven fabric filter material having the same structure as that of Example 1 in the dense layer portion and the coarse layer portion was obtained. As the spunbond layer is eliminated, the basis weight of the dense layer portion is set to 125 g / square meter.

Experiment: Performance evaluation was carried out on delamination of filter media and general dust (JIS-8 type dust). The obtained non-woven filter material was formed into a folded structure, and a frame was attached to make an air cleaner element, which was used for the test. Each air cleaner element was subjected to a dust trapping amount test and a pulsation performance test for JIS-8 type dust according to JIS D1612 (Automobile Air Cleaner Test Method). The test conditions are shown below.

Filter material effective filtration area: 0.18 square m
Test dust: General dust (JIS-8 type dust)
Dust supply rate: 4.2 g / min Test flow rate: 4.2 cubic m / min Ventilation resistance: Differential pressure between upstream and downstream of filter medium (at start of test)
The time when the increased ventilation resistance reaches 2.94 kPa is defined as full life, and the amount of dust captured so far (dust trapping amount) is defined as the life (dust holding amount).

In addition, an experiment for evaluating dust removal with respect to intake pulsation was performed, and pulsation transmittance was measured.
In the pulsation performance evaluation test, the rated flow rate (4.2 cubic m / min) was measured using an air cleaner element in which dust was adhered until clogging to reach the full life through the measurement test of the dust trapping amount. A pulsation evaluation test was performed in which a cyclic pressure fluctuation of plus or minus 33 kPa was applied at a frequency of 167 Hz for 30 minutes while air was flowing. When the pulsation evaluation test is performed, the dust trapped in the air cleaner element flows out to the downstream side due to dust removal, and the amount of dust trapped in the air cleaner element decreases. From the weight change of the air cleaner element before and after the pulsation evaluation test, calculate the weight of the dust that has been removed by pulsation, and divide it by the amount of dust retained at the start of the pulsation evaluation test (the amount of dust trapped during full life). Pulsation permeability (%) was calculated.

The test results are shown in Tables 1 and 2 in terms of scores.
The evaluation of layer separation of the nonwoven fabric filter material is such that when the filter element is pleated, or when a dust test is performed using the filter element, the layer that does not peel between the dense layer portion and the spunbond layer is ○ In the case of pleating or dust test, the case where peeling occurred between the dense layer portion and the spunbond layer is indicated by △, and when the pleated processing or dust test, the dense layer The thing which was easy to produce peeling between a part and a spunbond layer was shown by x.
In addition, the score of dust omission shows how much the dust omission suppression performance has been improved / deteriorated on the basis of the test value of the pulsation evaluation rate of Comparative Example 1 (10 points). The larger the value is, the better performance (the pulsation transmittance becomes lower). For example, an increase in the pulsation transmittance score from 10 to 15 indicates that the pulsation transmittance is halved.

In any of the Examples, the score for suppressing dust omission is greatly improved as compared with Comparative Example 1. It can be seen that by performing the binder treatment step after the needle punching step, the effect of suppressing dust removal is greatly enhanced. Moreover, there is no delamination and the spunbond layer and the dense layer are well integrated.
In Comparative Example 1, since the binder treatment was not performed after the needle punching process, dust leaked from the holes formed in the spunbond layer in the needle punching process, and it was considered that the effect of suppressing dust removal was not so enhanced. .
Moreover, when Example 1 and Example 2 are compared, it turns out that the one where the average fiber diameter of a dense layer part (1st nonwoven fabric layer) is thin improves the suppression effect of dust omission more.
Further, when Example 1 and Example 3 are compared, it can be seen that, even if needle punching is performed from any direction, if the binder treatment step is performed after the needle punching step, the effect of suppressing dust removal is similarly enhanced.

In Comparative Example 2 and Comparative Example 3, the dense layer portion and the spunbond layer were not sufficiently integrated, and a nonwoven fabric filtering material that could be mass-produced was not obtained. In these comparative examples, since the spunbond layer does not undergo the needle punching process, no hole is opened in the spunbond layer, and the effect of suppressing dust removal is high.

In Comparative Example 4, since the average fiber diameter of the fibers constituting the dense layer portion was 25 μm, the effect of suppressing dust omission was not so enhanced from Comparative Example 1.
In Comparative Example 5, since the space ratio of the dense layer portion was as high as 97.1%, the effect of suppressing dust omission was equivalent to that of Comparative Example 1.

Since Comparative Example 6 does not have a spunbond layer, the effect of suppressing dust removal is lower than that of Comparative Example 1.

As described above, the first nonwoven fabric layer having a specific average fiber diameter and a specific space ratio and a spunbond layer are laminated adjacent to each other, passed through a needle punching process, and then a binder treatment process is performed for both layers. It has been demonstrated that integrating the two layers firmly integrates the two layers and enhances the effect of suppressing dust removal.

The nonwoven fabric filtering material according to the present invention can be used, for example, for the purpose of filtering air supplied to an automobile engine. In particular, the nonwoven fabric filtering material is excellent in the effect of suppressing dust removal with respect to intake pulsation, and has high industrial utility value.

DESCRIPTION OF SYMBOLS 1 Nonwoven fabric filter material 11 Coarse layer part 12 Dense layer part 13 Spunbond layer 2 Air cleaner element 21 Frame body 22 Seal member 11W Coarse layer web 12W Dense layer web N Needle C Fiber dense part

Claims (4)

A method for producing a multilayer nonwoven fabric filtering material comprising a first nonwoven fabric layer located on the upstream side and a spunbond nonwoven fabric layer located on the downstream side adjacent to each other,
In the nonwoven fabric filtering material, the first nonwoven fabric layer is mainly composed of fibers having an average fiber diameter of 5 to 20 μm, and the first nonwoven fabric layer has a space ratio of 87 to 95%,
Integration of the first nonwoven layer and the spunbond layer
A needle punching process in which a needle is struck so as to penetrate both layers;
And a binder treatment step for at least the first nonwoven fabric layer after the needle punching step. In the needle punching process,
2. The nonwoven fabric filtering material according to claim 1, wherein at least a part of the needle that is struck through the first nonwoven fabric layer and the spunbond layer is struck from the first nonwoven fabric layer side toward the spunbond layer side. Production method. The method for producing a nonwoven fabric filter material according to claim 1 or 2, wherein the spunbond layer is located on the most downstream side in the nonwoven fabric filter material. The manufacturing method of the nonwoven fabric filter material of Claim 3 which provided the 2nd nonwoven fabric layer with a higher space rate than a 1st nonwoven fabric layer in the upstream rather than the 1st nonwoven fabric layer.

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