JP2015147199A - Filter medium made of nonwoven fabric for pleat type filter with low ventilation resistance and production method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter medium capable of maintaining the form of a pleat for a long term and adding a constituent capable of maintaining the pleat for a long term by a simple method and to provide a production method of the same.SOLUTION: In a filter medium,: a plurality of parallel linear ridges extending in a longitudinal direction and/or a plurality of semicylindrical ridges regularly repeating in both width and longitudinal directions are formed on one surface of a first nonwoven fabric layer constituted by at least a synthetic fiber; the heights of the semicylindrical and linear ridges are 1-7 mm; the semicylindrical and linear ridges are formed at 0.8-5.7 column/10 cm intervals in a width direction; and further the length of the ridge is 7-50 mm and the basis weight of the filter medium is 180-550 g/min the case of the semicylindrical ridge.

Description

  The present invention relates to a non-woven filter medium for pleated type filters, and more particularly to a filter medium having a low airflow resistance.

  Conventionally, various filter media are required to have a low airflow resistance, a high collection efficiency for fine dust, and a material that exhibits a long filter life. In general, in order to exhibit high collection efficiency, the fiber diameter of fibers to be used is reduced, or the number of fibers is increased to make the gap for capturing dust smaller. However, as the number of fibers increases and the inter-fiber gap decreases, the ventilation resistance increases, resulting in a problem that the filter life is shortened and the total amount of dust that can be collected decreases.

  On the other hand, if the fiber diameter of the filter medium is increased, the airflow resistance is reduced, but the interfiber gap is increased, so that minute dust cannot be captured and the collection efficiency cannot be increased. Therefore, a method of pleating the filter medium to increase the filtration area is employed. However, even in the case of a pleated filter medium, it is necessary to increase the amount of fibers and make the filter medium thicker in order to further increase the amount collected. For this reason, such a thick filter medium comes into contact with the adjacent pleats when the pleats are applied, and causes a new problem that the ventilation resistance increases.

  Various improvements have been attempted to solve this problem. For example, Patent Document 1 discloses a method in which a filter medium is equipped with a spacer, the spacers are in contact with each other, and the filter medium is not in contact with each other. Patent Document 2 discloses a method of maintaining a shape by inserting a plate on a comb into a pleat-shaped crest and trough. Patent Documents 3 to 4 disclose a method in which embossing is performed on the filter medium, and the embossed protrusions come into contact with each other to prevent surface contact and prevent increase in ventilation resistance.

JP 2000-107526 A JP 2012-125683 A JP 2009-11887 A JP 2013-52321 A

  However, when a non-breathable spacer or comb is attached to the filter medium, there is a problem that the filtration area is reduced by that portion, and there is a problem that the collection efficiency and the collection amount are lowered. There is a problem such as. Further, the embossed filter medium may change the size of the filter medium during molding or use, and it is difficult to reliably bring the protrusions into contact with each other. In addition, any of the above-described methods requires the addition of a new process and processing equipment other than the filter medium manufacturing apparatus, which may increase the cost.

  Under such circumstances, the present invention provides a filter medium that can maintain the configuration of the pleats over a long period of time, and can provide a structure that enables the long-term maintenance of the pleats by a simple method, and a method for producing the same. As an issue.

  As a result of intensive research in order to solve the above problems, the present inventor has obtained a plurality of parallel linear wrinkles extending in the longitudinal direction on one side of the nonwoven fabric and / or both in the width direction and the longitudinal direction. By forming a plurality of kamaboko-shaped ridges that repeat regularly, if the pleats are processed so that the opposing heels come into contact, the heels will support the pleats and withstand the wind pressure during filtration, The present invention has been completed by finding that the shape can be maintained over a long period of time.

That is, the filter medium according to the present invention has a plurality of parallel straight wrinkles extending in the longitudinal direction and / or both the width direction and the longitudinal direction on one side of the first nonwoven fabric layer composed of at least synthetic fibers. A plurality of kamaboko-shaped ridges that are regularly repeated are formed, and the kamaboko-shaped ridge or the linear ridge has a height of 1 to 7 mm, and the kamaboko-shaped ridge or the straight line Are formed at intervals of 0.8 to 5.7 rows / 10 cm in the width direction, and in the case of a kamaboko-shaped ridge, the length of the ridge is 7 to 50 mm and the basis weight of the filter medium is 180 to It is characterized by being 550 g / m ² . The kamaboko-shaped ridge or the linear ridge preferably has a width of 1 to 10 mm. Furthermore, it is a more preferable aspect that it contains 2nd fiber whose melting | fusing point is lower than the said synthetic fiber, and the compounding ratio of this 2nd fiber is 30-100 weight% in 100 weight% of filter media. Moreover, it is more desirable that the synthetic fiber constituting the ridge is fused via the second fiber. Furthermore, it is desirable that a second nonwoven fabric layer having a fiber density smaller than that of the first nonwoven fabric layer is laminated on the side where the wrinkles of the first nonwoven fabric layer are not formed.
Furthermore, the present invention is a method for producing the filter medium, the step of heating a non-woven fabric for a filter composed of synthetic fibers to a temperature lower than the melting point of the synthetic fibers and above the glass transition temperature, and a rotating roll having a pressing part, A process of passing a heat-treated non-woven fabric for a filter between a pair of upper and lower rotating rolls configured with a rotating roll having a groove corresponding to the pressing portion, and forming the ridge by the pressing portion and the groove of the rotating roll. And a method for producing a filter medium characterized by comprising: It is preferable that the means for pressing the filter nonwoven fabric is a disk provided in the rotating roll, and the disk is a disk having a circular disk and / or a convex part. Furthermore, when supplying the nonwoven fabric for a filter between a pair of upper and lower rotating rolls, it is a preferable aspect that the first nonwoven fabric layer is supplied in contact with the groove of the rotating roll.

  According to the present invention, it becomes possible to increase the amount of dust collected while maintaining the collection efficiency at a high level without increasing the airflow resistance in the pleated type nonwoven fabric for a filter, thereby increasing the life of the filter medium. Can be achieved.

It is a schematic sectional drawing which shows an example of the embodiment of the filter medium which concerns on this invention. It is a schematic perspective view before the pleating process of the filter medium which concerns on this invention. It is a schematic sectional drawing after the pleating process of the filter medium which concerns on this invention. It is a schematic perspective view which shows another example before the pleating process of the filter medium which concerns on this invention. It is a schematic sectional drawing which shows another example after the pleating process of the filter medium which concerns on this invention. It is a schematic sectional drawing which shows an example of the conventional type filter medium after a pleating process. It is a schematic perspective view which shows a brewing processing apparatus. It is the schematic which shows a circular disk. It is the schematic which shows the squeezing process when using a circular disk. It is the schematic which shows the disk which has a convex part. It is the schematic which shows the squeezing process when using the disk which has a convex part.

  Hereinafter, the filter medium according to the present invention will be described in detail with reference to the drawings showing the embodiments. However, the present invention is not limited to the illustrated examples, but within a range that can be adapted to the purpose described above and below. The present invention can be carried out with appropriate modifications, and all of them are included in the technical scope of the present invention.

<Filter media>
FIG. 1 is a schematic cross-sectional view showing an example of an embodiment of a filter medium according to the present invention (the arrow in FIG. 1 indicates the direction of air passing through the filter medium). The filter medium 10 is made of fibers with fine fineness on the air outflow side, and the high-density first nonwoven fabric layer (dense layer) 1 in which fiber entanglement is promoted and increased in density by needle punching is provided on the air ingress side. Is composed of a laminate in which a low-density second non-woven fabric layer (coarse layer) 2 blended with fibers having a thick fineness is laminated.

  The filter medium 10 is regularly formed in at least one side of the first nonwoven fabric layer composed of synthetic fibers on a plurality of parallel linear wrinkles extending in the longitudinal direction and / or in both the width direction and the longitudinal direction. It is characterized in that a plurality of kamaboko-shaped ridges are formed repeatedly. The flange 3b has a shape in which the center of the fiber bundle is most raised, and preferably has a conical section, an elliptical section, or a rectangular section in the thickness direction. Further, it is preferable that the ridges 3b are formed so that the ridges 3b existing on the opposed surfaces of the folded filter medium can come into contact with each other when the filter medium 10 is pleated.

  Although the manufacturing method of the eaves 3b will be described in detail later, the eaves 3b are formed by extruding the fibers of each layer constituting the filter medium 10. Thus, when the fiber is extruded and the heel 3b is formed, since the heel 3b can be finished rigidly, sufficient strength can be exhibited. In particular, in the present invention, it is preferable to manufacture the heel 3b using a disk to be described later because a heel having a uniform height and width can be easily formed.

  FIG. 2 shows a schematic perspective view of the filter medium 10 according to the present invention before pleating. FIG. 2 shows a state in which two linear ridges 3b are formed on the filter medium 10 on the air outflow side. When the filter medium 10 is pleated, the filter medium 10 is bent from the end of the filter medium 10 in the direction in which the ridges 3b are formed (referred to as the brewing direction x, synonymous with the long direction) to form ridges. To do. In the present invention, a state in which the ridges are continuously present on one side of the filter medium is referred to as a “linear ridge”.

  FIG. 3 shows the pleated filter medium 10 formed in this way. As shown in FIG. 3, the filter medium 10 is pleated so that the linear ridges 3b are opposed to itself, so that the valley fold (the squeezed surface on which the ridges of the filter medium 10 are formed is shown). The contact point 4 where the ridges existing in one ridge contact each other exists on the squeezed surface. Since the contact point 4 exists, even if air flows into the filter medium 10, the contact point 4 serves as a support for the pleats, and can withstand wind pressure and maintain the pleat shape of the filter medium 10.

  FIG. 4 is a perspective view of the filter medium 10 before pleating when the ridge 3b is partially formed on one surface of the filter medium 10. FIG. In the present invention, the state where the cocoons are scattered on one side of the filter medium is referred to as a “kamaboko-shaped cocoon” based on the shape of the cocoon. The “kamaboko type” is a half-moon shape or a rectangle in which the cross section when the ridge is cut in the width direction is raised at the center, and when the ridge is viewed from directly above, the long direction is a rectangle longer than the width direction. State. FIG. 5 shows an example in which the filter medium 10 shown in FIG. 4 is pleated so that the kamaboko-shaped ridges face each other and come into contact with each other. Since the contact point 4 serves as a support for the pleats as long as the opposing kamaboko-shaped ridges come into contact with each other in this way, the effect of the present invention is sufficiently exhibited even if the ridges are not linear. Is done.

  On the other hand, FIG. 6 is a schematic sectional view showing an example of a conventional filter medium after pleating. Since the conventional type filter medium is not subjected to squeezing processing, there is no contact point 4 where the facing ridges come into contact. Therefore, when air flows into the filter medium in the direction indicated by the arrow, the fibers of the filter medium are dense, so the air stays on the air inflow side, and the filter medium comes into contact with the adjacent pleats on the surface, or the pleats There is a risk of opening from V to U. When the pleat shape is U-shaped, filtration is performed only at the bottom of the U-shape, and filtration using the entire filter medium becomes difficult. In addition, problems such as increased ventilation resistance occur. Then, the collection efficiency decreases and it becomes difficult to lengthen the filter life. Usually, hot melt resin is discharged linearly along the pleats to form beads, ribs, etc. The pleats are fixed with the fixing tool.

  That is, according to the present invention, the filter medium 10 is formed with the ridge 3b, so that even if the filter medium 10 does not have a fixture, the presence of the contact point 4 prevents the pleats from coming into contact with each other due to the incoming wind pressure. Since the opening can be suppressed, the shape of the pleat can be maintained over a long period of time. Therefore, various advantages such as a longer filter life of the filter medium 10 and easier recycling can be expected.

  The width of the wrinkles (straight wrinkles and kamaboko-shaped wrinkles) formed by the squeezing process is preferable since the wrinkles are likely to abut each other when pleated. For this reason, the width of the ridge is preferably, for example, 1 to 10 mm, more preferably 1.5 to 8 mm, and still more preferably 1.8 to 4 mm. When the width of the ridge is less than the lower limit, the air permeability of the filter medium can be secured, so although the reduction in filtration efficiency can be prevented, it is difficult for the ridge to overlap with the heel that faces the pleat when pleated, and the heel supports the pleat. This is not preferable because there is a possibility that it cannot be fully exhibited. Moreover, when the width | variety of a ridge exceeds an upper limit, the area of a press part will become large and there exists a possibility that the ventilation resistance of a filter medium may increase. The width of the ridge is approximately the same as the ring width of the disk described later.

  The height of the ridges formed by brewing (linear ridges and kamaboko-shaped ridges) is, for example, preferably 1 to 7 mm, more preferably 1.5 to 4.5 mm, still more preferably 1. .7-3 mm. If the height of the ridge is less than the lower limit, the contact point of the heel will not be clear even if pleated, and the pleat will open and the air flow resistance will increase, which is not preferable. On the other hand, if the height of the ridge exceeds the upper limit value, the contact area of the heel increases, and the heel may fall down or be crushed by being pushed by the contacting heel in contact with the heel.

  Moreover, in the case of a kamaboko-shaped ridge, the length of the ridge is, for example, preferably 7 to 50 mm, more preferably 10 to 40 mm, and still more preferably 10 to 30 mm. If the length of the ridge is within the above range, it is preferable because the filter medium does not come into surface contact and the ventilation resistance of the filter medium is not increased more than necessary.

  Moreover, it is preferable that the ridges (linear ridges and kamaboko-shaped ridges) are formed, for example, in the width direction, 0.8 to 5.7 rows / 10 cm, more preferably 1.5 to 5 rows / 10 cm, more preferably 1.8 to 4 rows / 10 cm. If the number of wrinkles per 10 cm is less than the above range, the distance between the wrinkles becomes too large, and the filter medium is liable to cause surface contact, which is not preferable. On the other hand, if the number of hooks per 10 cm exceeds the above range, the area occupied by the hooks may increase, and the ventilation resistance may increase. If the ventilation resistance is increased, the fluid to be filtered passes through the gap between the small fibers through which air can pass due to the pressure difference, which may cause a decrease in the collection efficiency.

  In the present invention, a straight ridge or a kamaboko-shaped ridge, or both, are formed on one side of the filter medium, but only a linear ridge is provided on one side of the filter medium for ease of pleating. It is preferable that only kamaboko-shaped ridges are formed.

  Next, the configuration of the filter medium 10 will be described. In applications where high collection efficiency and fine dust collection are not required, it is not essential to make layers of the filter medium, and the filter medium may be a single layer. However, when enhancing the performance as a filter medium, as shown in FIG. 1, the filter medium 10 has a fiber density lower than that of the first nonwoven fabric layer on the side where the wrinkles of the first nonwoven fabric layer are not formed. It is preferable to have a laminated structure of two or more different layers in which the second nonwoven fabric layer is laminated. It is particularly preferable that the first nonwoven fabric layer and the second nonwoven fabric layer are integrated.

  When two or more nonwoven fabric layers are laminated, the first nonwoven fabric layer is a layer provided on the air outflow side. Since the first nonwoven fabric layer is mixed with fine fibers, the first nonwoven fabric layer has a high density (dense layer) and can capture fine particles that could not be captured by the second nonwoven fabric layer. On the other hand, the second nonwoven fabric layer is a layer provided on the air inflow side of the filter medium 10. Since thick fibers are mixed in the second nonwoven fabric layer, it is a low-density layer (coarse layer) as compared to the first nonwoven fabric layer. In the present invention, the layers constituting the filter medium 10 are not limited to two layers, and the filter medium may be formed of three or more different layers. Even when three or more layers are stacked in this manner, each layer may have a stacked structure in which the fiber density increases in order from the air inflow side to the outflow side. It is preferable that the filter nonwoven fabric used as a base material has a different laminated structure of 2 to 5 layers.

  The configuration of the filter medium (weight per unit, thickness, fiber fineness, degree of layer density, etc.) can be appropriately changed according to the size, number, and application of the target dust, and is not particularly limited. Absent. However, since it is essential that the filter medium according to the present invention is pleated, the structure of the filter medium and the like is naturally included in a conventionally used range.

The basis weight of the filter medium 10 is, for example, preferably 180 to 550 g / m ² , more preferably 230 to 500 g / m ² , and still more preferably 280 to 450 g / m ² . If the basis weight of the filter medium 10 is within the above range, a filter medium having an appropriate air permeability can be obtained, and both the collection efficiency and the filter life can be achieved. When it is less than 180 g / m ² , the dust collection efficiency is lowered, and the amount of fibers for squeezing processing is so small that it is difficult to form a desired rigid soot. On the other hand, if it exceeds 550 g / m ² , the filter medium becomes too thick, the pleat peaks and valleys cannot be folded sharply, and the effect of the squeezing process may not be sufficiently exhibited.

  For example, the thickness of the filter medium 10 is preferably 0.7 to 8.5 mm, more preferably 2 to 8 mm, and still more preferably 4 to 8 mm. If the thickness of the filter medium 10 is less than 0.7 mm, the rigidity of the filter medium 10 is not sufficient, and there is a concern that the pleats may be deformed or easily damaged. Moreover, when it exceeds 8.5 mm, there exists a possibility that the filter medium 10 may be too thick and it may become difficult to form a pleat.

  Moreover, the filter medium 10 needs to have rigidity required as a filter medium. In consideration of pleating, it is preferable that the filter medium 10 is harder because the shape of the filter medium after the pleat formation becomes sharper and the swelling due to wind pressure during use can be reduced. Therefore, the bending hardness of the filter medium 10 measured by JIS L1913 6.7.1 cantilever method is preferably 120 mm or more, and more preferably 150 mm or more.

  The ventilation resistance described in JIS D1612, measured by pleating the filter medium and producing an element, is preferably 100 to 600 Pa, more preferably 150 to 500 Pa, and still more preferably 200 to 340 Pa. is there. The ventilation resistance of the filter medium needs to be adjusted as appropriate according to the product size. For example, it is 200 Pa or less for a product with a thickness of about 4 mm or less, 330 Pa or less for a product with a thickness of 6 mm, or 600 Pa for a product with a thickness of about 8 mm or more. It is good to make it below.

  Hereafter, each structure of the filter medium 10 and the manufacturing method of the filter medium 10 are explained in full detail.

<Nonwoven fabric for filters>
A non-woven fabric for a filter that is a base material for a filter medium will be described. The structure of the filter nonwoven fabric used as the substrate is not particularly limited, and can be appropriately changed depending on the intended use of the obtained filter medium, the required performance (size of an object to be filtered), and the like. The substrate may be a single non-woven fabric layer, or may be a laminate composed of two or more layers having different blending ratios of fibers having different fineness, or entanglement (density) and pressure density.

  The fibers of the first nonwoven fabric layer preferably have a fineness of, for example, 0.8 to 5 dtex, more preferably 1 to 4 dtex, and still more preferably 1.5 to 3 dtex. If the fineness of the first nonwoven fabric layer fiber is within the above range, the filter medium can be made dense. Furthermore, when the filter medium is a laminate of two or more layers, it is possible to collect fine dust that could not be collected by the second nonwoven fabric layer, and to make the ridges rigid, so that the pleats of the filter medium 10 can be opened. Can be suppressed. However, when the fineness of the first nonwoven fabric layer is less than 0.8 dtex, the rigidity of the heel becomes poor and it becomes difficult to form a rigid ridge. Therefore, a contact point is not formed, the filter medium 10 causes surface contact, and the pleats are easily opened, which is not preferable.

  Moreover, it is preferable that the fiber of a 2nd nonwoven fabric layer is 2-33 dtex, for example, More preferably, it is 3-27 dtex, More preferably, it is 4-22 dtex. If the fineness of the second nonwoven fabric layer fiber is within the above range, air can be allowed to pass through without excessively increasing the pressure loss of the filter medium while filtering dust having a relatively large particle size. It is possible to simultaneously improve the collection efficiency and extend the life of the filter medium. However, if it exceeds 33 dtex, the fibers become difficult to be entangled, so that the collection efficiency is deteriorated, and it is difficult to uniformly form the wrinkles made of the fiber bundle.

  Examples of fibers constituting the filter medium include polyester fibers such as polyethylene terephthalate fibers, polybutylene terephthalate fibers, polylactic acid fibers, and polyarylate; nylon 6, nylon 66, aramid fibers (para-aramid fibers, meta-aramid fibers, etc.) And various synthetic fibers such as polyamide fibers such as polyacrylonitrile fibers, acrylic fibers such as polyacrylonitrile-vinyl chloride copolymer fibers, polyolefin fibers such as polyethylene fibers and polypropylene fibers, and polyphenylene sulfide fibers. Among them, polyester fiber is preferably used because of a good balance between performance and price, and polyethylene terephthalate fiber is particularly preferable. In addition to synthetic fibers, the fibers that make up the filter media are made of synthetic fibers, recycled fibers such as rayon, polynosic, cupra, and lyocell; natural fibers such as cotton, pulp, kapok, hemp, hair, and silk. Etc. may be included. When the filter medium 10 is formed by laminating two or more layers having different densities, the layers constituting the filter medium 10 may be composed of the same type of fibers or may be different between the layers. In the present invention, since the disposal after use is easy, it is preferable that all layers constituting the filter medium 10 are made of the same type of fiber.

  Further, as the fibers constituting the filter medium, either solid fibers or hollow fibers can be used. Moreover, the cross-sectional shape of the fiber is not particularly limited, and a round cross-section; The modified cross-section fiber is effective as a means for adjusting the density of the filter medium.

  Moreover, in order to accelerate | stimulate the entanglement of the fiber at the time of needle punching, and in order to prevent the cutting | disconnection of a fiber, the fiber which provided various oil agents can also be used. The use of an oil containing silicon is particularly effective for promoting slippage between fibers. It is also possible to use fibers that are flame retardant, antibacterial and antifouling according to the required quality. The application of such various functions may be performed after the filter medium is manufactured, but it is preferable to use the fibers that have been subjected to various treatments because the effect can be obtained from the stage of manufacturing the filter nonwoven fabric.

  In order to impart dimensional stability and necessary rigidity to the filter medium, the fibers constituting the filter medium include a fiber that forms the skeleton of the filter medium and a second fiber having a lower melting point than the fibers (also referred to as a low-melting fiber). For example, a composite fiber having a low melting point or the like may be blended. Since a low melting point fiber melts part or all of the fiber by heat treatment, the melted fiber (resin) bonds the fibers constituting the filter medium. By cooling after the heat treatment, the melted low melting point fiber is solidified to increase the adhesive strength of the fiber and impart appropriate strength to the filter medium, so that the size of the filter medium is stable and the filter medium has appropriate rigidity. Can be given. In addition, when forming a filter medium from two or more nonwoven fabric layers with a density gradient, it is preferable that the low melting-point fiber is contained in at least 1 layer, and it is contained in all the nonwoven fabric layers which comprise a filter medium. More preferred.

  In the present invention, it is important to make the heel rigid in order to prevent the heel from falling or denting. The blending ratio of the low-melting fiber is preferably 30 to 100% by weight, more preferably 60 to 95% by weight, and further preferably 70 to 90% by weight in 100% by weight of the filter medium. If the blending ratio of the low melting point fiber is within the above range, it is preferable that the melted and solidified low melting point fiber does not unnecessarily reduce the air permeability of the filter medium and makes the brim portion rigid.

  The melting point of the low-melting fiber is preferably, for example, 30 ° C. or lower from the melting point of the fiber whose upper limit is the skeleton. When the difference in melting point is small (for example, 30 ° C. or less), when heat treatment is performed to melt the low melting point fiber, if the temperature becomes abnormal due to some trouble, the fiber is softened or melted. This is not preferable because it may cause The upper limit of the melting point of the low melting point fiber is more preferably 50 ° C. or less from the melting point of the fiber. On the other hand, the lower limit of the melting point of the low melting point fiber is preferably 150 ° C. or less, more preferably from the melting point of the fiber to 100 ° C. or less so that the low melting point fiber is sufficiently softened or melted. The melting point of the low-melting fiber is, for example, preferably 50 to 150 ° C, more preferably 70 to 120 ° C.

  The low-melting fiber includes a composite fiber having a core-sheath structure, an eccentric structure, or a side-by-side structure composed of a plurality of resins having different melting points such as polyethylene-polypropylene and polyester-low-melting polyester; modified polyester fiber; modified polyamide fiber; Modified polyolefin fibers such as polypropylene fibers can be used. In the present invention, a composite fiber is preferable so that the resin of the low melting point portion functions as an adhesive and the fiber of the high melting point portion functions as a fiber constituting the filter medium, and those having a core-sheath structure particularly excellent in mechanical properties are preferable. .

The fineness of the low melting point fiber is, for example, preferably 1 to 15 dtex, more preferably 1.5 to 10 dtex. When the fineness of the low-melting fiber is within the above range, the low-melting fiber is easily melted and the heat treatment time can be shortened.
In addition, when forming a filter medium from two nonwoven fabric layers with a density gradient, 1-5 dtex is preferable and, as for the low melting fiber of a 1st nonwoven fabric layer, More preferably, it is less than 1.5-3 dtex. Moreover, 2-15 dtex is preferable and, as for the low melting point fiber of a 2nd nonwoven fabric layer, More preferably, it is 3-10 dtex.

The basis weight of the base material is, for example, preferably 180 to 550 g / m ² , more preferably 230 to 500 g / m ² , and still more preferably 280 to 450 g / m ² . If the basis weight of the filter medium 10 is within the above range, a filter medium having an appropriate air permeability can be obtained, and both the collection efficiency and the filter life can be achieved. In addition, when forming a filter medium from two nonwoven fabric layers with a density gradient, 100-330 g / m < ² > is preferable and the fabric weight of a 1st nonwoven fabric layer is more preferable 150-300 g / m < ² >. The basis weight of the second nonwoven layer is preferably 60~240g / m ^2, and more preferably 100 to 200 g / m ^2. The weight ratio of the basis weight is preferably 80 to 400% by weight, more preferably 100 to 300% by weight, and still more preferably 110 to 240% by weight for the first nonwoven fabric layer with respect to 100% by weight of the second nonwoven fabric layer. % By weight. Increasing the weight ratio of the first nonwoven layer further improves the efficiency of collecting fine dust.

<Method for producing filter medium>
Next, a method for producing the filter medium will be described. The method for producing the filter media is as follows:
A process for heating a non-woven fabric for filters composed of synthetic fibers to a temperature lower than the melting point of the synthetic fibers and above the glass transition temperature (heat treatment process), a rotating roll having a pressing part, and a groove corresponding to the pressing part A process of passing the heat-treated non-woven fabric for filter between a pair of upper and lower rotating rolls composed of rotating rolls, and forming the wrinkles by pressing portions and grooves of the rotating rolls (scouring process);
It has the feature in the point containing. This will be described in detail below.

<Nonwoven fabric manufacturing process>
The manufacturing method of the nonwoven fabric used for the leaching process is not particularly limited. For example, nonwoven fabrics such as dry nonwoven fabrics, wet nonwoven fabrics, and spunbond nonwoven fabrics can be used as appropriate. The web bonding method is not particularly limited, for example, a mechanical entanglement method such as a needle punch method, a spunlace method (a water entanglement method), or the like. Various bonding methods such as a method of thermally melting part or all of the melting point fibers and fixing the fiber intersection (thermal bond method) can be employed. Among these, the combined type of the needle punch method and the thermal bond method in which fibers are entangled by the needle punch method and then heat treatment is preferable.

When the filter medium is a laminate of two or more webs, the first nonwoven fabric layer web and the second nonwoven fabric layer web are produced in advance, and after these are laminated, needle punching is preferably performed. When a spunbond nonwoven fabric is used, (i) a plurality of spunbond nonwoven fabrics having different fiber diameters are laminated, or (ii) a meltblown nonwoven fabric having a fiber diameter smaller than the fibers constituting the spunbond nonwoven fabric. Etc., and then needle punching may be performed on the resulting laminate. In order to increase the bonding strength between the layers, heat treatment may be performed after needle punching. In addition, it is preferable to puncture a needle from the 1st nonwoven fabric layer side (air outflow side) for the needle punch process at the time of integrating a some web. This is because when the needle punching is performed from the first nonwoven fabric layer side, the fibers in the web are entangled so as to protrude toward the second nonwoven fabric layer side, so that the passage of dust can be suppressed. The needle punching process at this time is preferably performed under conditions of a needle punch needle count 36 to 42, a needle depth of 7 to 12 mm, and a penetrating number of 50 to 70 pieces / cm ² .

<Heat treatment>
In this invention, in order to form the wrinkles excellent in form stability, the heat processing process which heat-processes to the nonwoven fabric for filters is implemented before a brewing process. By heating the non-woven fabric for the filter in advance to the melting point of the synthetic fiber and above the glass transition temperature and softening the fibers constituting the base material, it becomes easier to form wrinkles in the brewing process described later, and further the wrinkles formed Can be made rigid.

  Various methods are known as a method for heating a nonwoven fabric (softening fibers). For example, a method in which a nonwoven fabric is passed through a hot-air circulating dryer having two upper and lower endless belt conveyors, and the nonwoven fabric is heated. Examples thereof include a method of passing through a cylinder drum (preferably a plurality), a method of passing between calendar rolls and embossing rolls installed in a hot air circulation dryer, or a plurality of free rolls. Among these, in order to keep the width and thickness of the filter medium constant, it is preferable to use an endless belt conveyor or the like and perform heat treatment while sandwiching the filter nonwoven fabric.

The heating temperature is not higher than the melting point of the synthetic fiber of the nonwoven fabric and exceeds the glass transition temperature. Specifically, it is preferably 175 to 225 ° C, more preferably 190 to 220 ° C. Further, when the firmer texture of the filter medium, blending a low melting point fiber in order to make more rigid the ridges, the heating temperature is, with respect to the melting point T _L of the low-melting fibers are cotton mixing, T _L +5 (° C.) to T _L +15 (° C.) is preferable. A heating temperature within the above range is preferable because the low melting point fiber can be appropriately melted. The heating time may be appropriately set in consideration of the melting point and blending ratio of the low-melting fiber to be mixed, but is preferably 15 to 180 seconds, and more preferably 40 to 120 seconds, for example.

<Feeding processing>
A method for forming a straight wrinkle and / or a kamaboko-shaped wrinkle on the nonwoven fabric is not particularly limited as long as it is a method capable of forming a wrinkle. For example, a pair of rotating rolls 20 and 30 shown in FIG. 7 are used. A method is mentioned. A disk 21 is preferably attached to the main body 22 as a pressing means for the rotary roll 20, and the other rotary roll 30 is positioned at a position corresponding to the disk 21 in consideration of the thickness of the filter nonwoven fabric. It is preferable that a groove 31 wider than the width of the disk 21 is formed. In this invention, it is preferable that the means to press the said filter nonwoven fabric is the disk 21 with which the said rotating roll 20 was equipped. By passing the heat-treated non-woven fabric for filter between the pair of upper and lower rotary rolls 20 and 30, the non-woven fabric for filter is sandwiched between the pressing portion (disk 21) of the rotary roll 20 and the groove 31 of the rotary roll 30. The wrinkles can be formed by deforming the nonwoven fabric by pressing at this time.
In particular, when the second fiber is blended in the non-woven fabric for the filter, since the heat treatment is performed before the squeezing process, the synthetic fiber constituting the slag is passed through the second fiber after the squeezing process. It becomes a fused state. In addition, the second fiber that has been in direct contact with the disk 21 during the squeezing process may have a smooth surface after cooling and solidification due to the pressing of the disk 21 during the squeezing process.

  The disk 21 provided in the rotating roll 20 will be described. The shape of the disk 21 is not particularly limited, and is preferably a shape that can press the nonwoven fabric for filter. As the disk 21, for example, a circular shape in which the entire outer periphery of the disk can press the nonwoven fabric or a disk having a convex portion can be used.

  FIG. 8 shows a circular disk 21 having no defect. FIG. 9 shows a method for manufacturing a filter medium when the disk shown in FIG. 8 is used. In addition, the arrow which goes to the near side shown in FIG. 9 shows the direction which introduce | transduces the nonwoven fabric for filters used as a base material. As shown in FIG. 9, when a circular disk is used, the filter nonwoven fabric can be pressed over the entire circumference of the disk, so that the filter medium produced using the circular disk is linear as shown in FIG. It will have a habit of.

  On the other hand, FIG. 10 shows a disk 21 having convex portions 40. The disk having the convex portion 40 cannot press the nonwoven fabric for filter by the convex portion 40 and cannot press the nonwoven fabric by the concave portion 50. FIG. 11 shows a method for producing a filter medium in the case of using the disk shown in FIG. 10 (the arrow toward the front shown in FIG. 11 indicates the direction in which the filter nonwoven fabric used as the base material is introduced). As shown in FIG. 11, when a disk having convex portions 40 is used, wrinkles are formed at the points where the convex portions 40 and the nonwoven fabric contact each other, and no wrinkles are formed when the concave portions 50 pass over the nonwoven fabric. Therefore, the filter medium formed using the disk having the convex portions 40 as described above has a kamaboko-shaped ridge as shown in FIG. In the figure, X1 and X2 represent the length of the pressable portion, and Y1 and Y2 represent the length of the non-pressable portion, but the length of the pressable portion is preferably, for example, 7 to 50 mm, more preferably It is 10-40 mm, More preferably, it is 10-30 mm. X1 and X2 may be the same length or different, and Y1 and Y2 may be the same length or different.

  The ring width (thickness) of the disk 21 is appropriately changed depending on the width of the ridge to be formed, but is preferably 1 to 10 mm, more preferably 1.5 to 8 mm, still more preferably 1. 8-4 mm. If the ring width is less than the lower limit value, it is not possible to form a ridge having a desired width, and it is difficult to overlap with the ridges that face each other when pleating, and there is a possibility that the heel cannot sufficiently exert the support function of the pleats. is there. On the other hand, if the ring width exceeds the upper limit, the area of the pressing part increases, and the ventilation resistance of the filter medium may increase.

  Further, the distance between the disks when the disks 21 are arranged on the rotary roll 20 should be appropriately adjusted according to the number in the width direction of the ridges. For example, 0.8 to 5.7 rows / 10 cm is preferable. Preferably it is 1.5-5 rows / 10cm, More preferably, it is 1.8-4 rows / 10cm.

  In addition, the method for forming the ridge is not limited to the above-described disk, and the rotary roll 20 may be provided with triangular protrusions having a predetermined height and width on the roll surface in a linear or kamaboko shape. Can be used. In this case, it is important that the corners of the triangular protrusions are rounded so that the edges do not cut the filter nonwoven fabric.

  Next, the rotating roll 30 will be described. The rotating roll 30 is a support body on the side that receives pressure from the rotating roll 20. Usually, as such a support, a flat plate provided with lanes with a predetermined groove depth, width and pitch, or a groove with a predetermined groove depth, width and pitch formed on a metal cylinder (shaft). A rotating roll is used. In the present invention, it is preferable to use a rotating roll from the viewpoint of space saving. The rotary roll 30 shown in FIG. 7 is provided with a groove 31 having a predetermined groove depth and width corresponding to the disk 21.

  The shape of the groove is appropriately adjusted depending on the shape of the disk 21, and examples thereof include a rectangle and an inverted conical shape.

  Further, the groove depth may be adjusted according to the height of the ridge to be formed, but is preferably 1 to 7 mm, more preferably 1.5 to 4.5 mm, and still more preferably 1.7 to 3 mm. It is.

  The width of the groove can also be adjusted as appropriate according to the width of the ridge to be formed, and is preferably 1 to 10 mm, more preferably 1.5 to 8 mm, and still more preferably 1.8 to 4 mm.

  When the filter nonwoven fabric is supplied to the pair of rotary rolls 20 and 30, the temperature of the rotary roll is not particularly limited, but is preferably heated to facilitate the formation of wrinkles. For example, the temperature of the rotating roll is preferably 60 ° C. or more higher than the melting point of the low-melting fiber, more preferably the melting point of the synthetic fiber or less and the glass transition temperature above. Specifically, 175 to 225 ° C is preferable. In addition, when heating a rotary roll, it is good to heat and / or press to such an extent that air permeability can be hold | maintained so that a fiber may soften too much and a fiber may not become dense.

  When the filter nonwoven fabric is supplied between the pair of upper and lower rotary rolls 20 and 30, the first nonwoven fabric layer is supplied so as to be in contact with the groove 31 of the rotary roll 30, and the lower density nonwoven fabric layer (density) When the two layers of non-woven fabrics having different layers are laminated, the second non-woven fabric layer) is supplied in contact with the pressing portion of the rotary roll 20.

The wrinkles thus formed are fundamentally different from embossing (a processing method in which the fibers of the nonwoven fabric are heated and fixed). The first difference is in the pressed area and the arrangement of the ridges formed by pressing. In the case of embossing, the formed convex part has a pressing area of about ² to 7 mm ² and is regularly formed at intervals of 1 to 10 mm in the width direction and the length direction of the filter medium. On the other hand, the bag of the present invention has a pressing area of 20 mm ² or more and is overwhelmingly less than about 0.8 to 5.7 rows / 10 cm in the width direction of the filter medium. In other words, the present invention is characterized in that wrinkles having a relatively large pressing area are formed with a wide interval, whereby the holding power of the pleats can be increased. Further, as a second difference, the present invention does not press the nonwoven fabric with the disk 21 to be consolidated as in the embossing process, but arranges the groove 31 so that the nonwoven fabric is made into the groove when pressing with the disk 21. The point that a cocoon appears by bending along is mentioned. For example, as shown in FIG. 2, the filter medium manufactured by such a method has wrinkles on one side of the filter medium, and the back surface thereof (the surface on the second nonwoven fabric layer side in FIG. 2). There will be a corresponding recess. That is, unlike the embossing, the soot is not easily consolidated, and there is no possibility that the air permeability of the filter medium is lowered due to the presence of the soot. Therefore, according to the filter medium of the present invention, the advantage that the pressure loss during use can be reduced and the filter life can be extended is exhibited. As a third difference, the height of the convex portion is usually 0.5 mm or less in embossing, whereas the height of the collar of the present invention is 1 mm or more, compared to the convex portion formed by embossing, It is also different in that it has a height.

  Moreover, after the squeezing process, the nonwoven fabric may be once cooled in order to solidify the softened or melted fiber.

  In addition, the squeezing process may be performed after the heat treatment process described above is performed. (I) The method of performing the squeeze process following the heat treatment process, or (ii) the heat treatment process is performed once. After the nonwoven fabric is cooled and wound up, the woven fabric may be heated again to soften or melt the woven fabric, and then subjected to brewing.

<Pleated processing>
When the pleating process is performed on the filter medium, the filter medium obtained by the above-described method is cut after being cut into a predetermined size according to the application. The pleating method is not particularly limited. However, it is preferable to pleat the ridge-forming surface of the filter medium on the inside because it is easy to confirm the butting of the ridges. The pitch and the peak height are preferably 10 to 25 mm and the peak height is preferably 30 to 100 mm.

  In addition, when forming a kamaboko-shaped ridge, the length of the ridge formed by brewing is preferably 7 to 25 mm at both ends of the top in one pleat sandwiching one top. Preferably it is 10-20 mm. In addition, the length of the ridge which exists on both sides across one top part of a pleat may be the same, or may differ.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

Measurement methods in the examples are as follows.
1. Weight per unit: according to JIS L1913 6.2 2. Thickness before and after squeezing; according to JIS L1913 6.1 Ventilation resistance;
According to JIS D1612 (automobile air cleaner test method), a ventilation resistance test was performed under the following conditions.
Effective filtration area: 1760 cm ²
Projection area: 281 cm ²
Air amount: 5.7 cm ³ / min Air velocity: 54 cm / sec The difficulty of air flow depending on the presence or absence of a filter medium is expressed in Pa.

The element was created by the following method.
Element preparation: The filter media obtained by the methods described in Examples and Comparative Examples were cut at a width of 110 mm, and then pleated at a height of 50 mm and a pitch of 16 mm with the wrinkle-forming surface of the filter media inside. The periphery of the filter material after pleating obtained in this way was sealed and fixed to a plastic board using a sealing material to prepare an element (width 110 mm × length 255 mm × height 50 mm).

Examples 1-3
(1) Preparation of Needle Punch Nonwoven Fabric Consisting of 10% by weight of regular polyester having a fineness of 2.2 dtex and a fiber length of 51 mm, and 90% by weight of a core-sheath type polyester composite fiber having a fineness of 2.2 dtex, a fiber length of 51 mm and a melting point of 160 ° C. A web for a dense layer (first nonwoven fabric layer) having a basis weight of 170 g / m ² was produced. In the same manner, 10% by weight of regular polyester having a fineness of 17 dtex and a fiber length of 51 mm, 90% by weight of a core-sheath type polyester composite fiber having a fineness of 4.4 dtex, a fiber length of 51 mm, and a melting point of 130 ° C. Carding and lapping were performed to prepare a web for a coarse layer (second nonwoven fabric layer) having a basis weight of 150 g / m ² .
After laminating the dense layer web and the coarse layer web, needle punching is performed from the dense layer side with needle punch needle number 40 (organ FPD1-40) with a needle depth of 8.5 mm and a penetrating number of 60 pcs / cm ² . And a needle punched nonwoven fabric having a basis weight of 325 g / m ² was obtained.
(2) Heat treatment Next, heat treatment was carried out for 47 seconds in a conveyor type continuous heat treatment machine maintained at a hot air temperature of 215 ° C. to melt and fix the low melting point fibers.
(3) Unwinding processing The table shows the rotary roll 20 in which disks (diameter: 153 mm, ring width: 2 mm) are installed at intervals of 10 cm at the outlet of the conveyor type continuous heat treatment machine, and the position of the disk and the pair. A rotary roll 20 provided with a groove having a groove depth of 2 mm in width and set, with the nonwoven fabric after heat treatment set so that the dense layer side faces the rotary roll 30 side, the rotary roll 20 heated to 220 ° C., By passing between 30, a filter medium having a weight per unit area of 325 g / m ² having the ridge height shown in the table was obtained. In addition, the formed wrinkles were continuous. An element was produced using this filter medium, and the ventilation resistance was measured.

Examples 4-6
About the conditions of the squeezing process, the filter material was manufactured by the same method as Example 1 except having adjusted the ring width and disk space | interval of the disk 21 as shown in a table | surface, and having changed the depth of the groove | channel 31.

Examples 7-8
The disk 21 (diameter 153 mm) provided on the rotating roll is provided with both a pressing force possible part and a pressing non-pressing part (defect part), and the depth of the groove 31 is changed. A filter medium was produced in the same manner. As shown in FIG. 10, the outer periphery 480 mm of the disk 21 has a pressing forceable portion and a pressing pressure impossible portion. In the seventh embodiment, X1 = X2 (both pressing forceable portions) = 20 mm, Y1 = Y2 (both In the eighth embodiment, X1 = X2 = 10 mm and Y1 = Y2 = 110 mm are provided so that the pressing force impossibility portion) = 100 mm.

Examples 9-10
The weight of the coarse layer and the dense layer was changed as shown in the table, the depth of the groove 31 was changed, and a filter medium was manufactured by the same method as in Example 1 based on the conditions shown in the table.

Comparative Example 1
A filter medium was produced in the same manner as in Example 1 except that the heat treatment was performed under the conditions shown in the table without performing squeezing.

Comparative Example 2
A disk 21 (diameter: 153 mm) provided on the rotating roll was provided with both a pressing-capable portion and a pressing-impossible portion (defect portion), and a filter medium was produced in the same manner as in Example 2 based on the conditions shown in the table. In addition, as the disk 21, the thing in which the pressing force possible part provided in the disk outer periphery 480mm and the pressing pressure impossible part are X1 = X2 = 5mm and Y1 = Y2 = 115mm shown in FIG. 10 was used.

Comparative Example 3
The rotary roll 20 used in the squeezing process is changed to a rotary roll in which a disk 21 (diameter: 153 mm, ring width: 1 mm) is installed at an interval of 6 pieces per 10 cm, and has a groove depth shown in the table at a position corresponding to the disk. A rotary roll 30 provided with a groove having a width of 1 mm is installed, and the nonwoven fabric after the heat treatment is passed between the rotary rolls. By the same method as in Example 1 based on the conditions shown in the table, the ridge height shown in the table is set. A filter medium having a basis weight of 325 g / m ² was obtained. An element was produced using this filter medium, and the ventilation resistance was measured.

Comparative Examples 4-5
As the rotating roll 20 used in the squeezing process, a rotating roll in which two disks 21 (diameter: 153 mm, ring width: 2 mm) are installed per 10 cm, and a width having a groove depth shown in the table at the position of the pair with the disk. A rotating roll 30 provided with a 2 mm groove is installed, and the non-woven fabric after the heat treatment is passed between the rotating rolls, and has the ridge height shown in the table by the same method as in Example 1 based on the conditions shown in the table. A filter medium having a basis weight of 325 g / m ² was obtained. An element was produced using this filter medium, and the ventilation resistance was measured.

Comparative Examples 6-7
The basis weight of the coarse layer and the dense layer was changed as shown in the table, and a filter medium was produced by the same method as in Example 1 based on the conditions shown in the table.

  The filter medium according to the present invention is preferably used as a filter medium for various pleating filters used as pleats, and is particularly preferably used as a filter medium for, for example, an engine filter and an air conditioner filter.

1 First non-woven fabric layer (dense layer)
2 Second nonwoven layer (coarse layer)
3b 畝 4 Contact point 10 Filter medium 20, 30 Rotating roll 21 Disc 31 Groove 22, 32 Body 40 Convex part 50 Concave part x Extruding direction

Claims (8)

A plurality of parallel linear ridges extending in the longitudinal direction on one side of the first nonwoven fabric layer composed of at least a synthetic fiber, and / or a plurality of kamaboko-types that repeat regularly in both the width direction and the longitudinal direction Shaped folds are formed,
The kamaboko shaped ridge or the linear ridge has a height of 1 to 7 mm,
The kamaboko-shaped ridges or the linear ridges are formed in the width direction at intervals of 0.8 to 5.7 rows / 10 cm,
Furthermore, in the case of a kamaboko shaped cocoon, the cocoon length is 7 to 50 mm,
A filter medium having a basis weight of 180 to 550 g / m ² .   The filter medium according to claim 1, wherein the kamaboko-shaped ridge or the linear ridge has a width of 1 to 10 mm.   The filter medium according to claim 1 or 2, further comprising a second fiber having a melting point lower than that of the synthetic fiber, wherein a mixing ratio of the second fiber is 30 to 100% by weight in 100% by weight of the filter medium.   The filter medium according to claim 3, wherein synthetic fibers constituting the ridges are fused via the second fibers.   5. The second nonwoven fabric layer having a fiber density smaller than that of the first nonwoven fabric layer is laminated on the side where the wrinkles of the first nonwoven fabric layer are not formed. Filter media. A method for producing a filter medium according to any one of claims 1 to 5,
A process comprising heating a non-woven fabric for a filter composed of synthetic fibers to a temperature equal to or lower than the melting point of the synthetic fibers and exceeding the glass transition temperature, and a rotating roll having a pressing portion and a rotating roll having a groove corresponding to the pressing portion. A process of passing the heat-treated non-woven fabric for the filter between a pair of upper and lower rotating rolls, and forming the ridges by the pressing portion and the groove of the rotating roll;
A method for producing a filter medium, comprising: The means for pressing the nonwoven fabric for a filter is a disk provided in the rotating roll,
The method for producing a filter medium according to claim 6, wherein the disk is a circular disk and / or a disk having a convex portion.   The method for producing a filter medium according to claim 6 or 7, wherein when the filter nonwoven fabric is supplied between the pair of upper and lower rotating rolls, the first nonwoven fabric layer is supplied so as to be in contact with the groove of the rotating roll.