JP2015142879A - Nonwoven fabric filter medium for pleat type filter having low ventilation resistance and production method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter medium where constituents such that the form of a pleat can be maintained for a long term without requiring the addition of a new step and the maintaining of the pleat for a long term can be achieved can be added by a simple method and to provide a production method of the same.SOLUTION: A filter medium has a first nonwoven fabric layer. A plurality of partially raised projections with the fiber bundle of a nonwoven fabric on one surface of the nonwoven fabric layer or a plurality of ribs formed with an array aligning a plurality of the projections exist regularly. The height of each projection is 1.2-5.5 mm and a basis weight is 180-550 g/m.

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 Literature 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 are in contact with each other to prevent surface contact and increase in airflow 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. Furthermore, when the embossed filter medium is subjected to pleating, it is difficult to reliably bring the protrusions into contact with each other. Further, in the protrusion, since the fibers are densified by embossing, it is difficult for air to flow out, and there is a risk of increasing the airflow resistance. 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 does not require the addition of a new process, can maintain the form of the pleats over a long period of time, and has a configuration that allows the pleats to be maintained for a long period of time. The provision of a filter medium and a method that can be applied in the above manner was raised as an issue.

  As a result of intensive studies to solve the above problems, the present inventor formed a plurality of convex portions or ridges with raised fiber bundles on the surface on the air outflow side in a filter medium composed of a nonwoven fabric, When the filter media is arranged so that the convex portions facing each other come into contact with each other when processed, when this filter medium is pleated so that the convex portions face each other, this convex portion (畝) serves as a support for the pleats, and the wind pressure during filtration It was found that the pleated form can be maintained over a long period of time and the present invention was completed.

That is, the filter medium according to the present invention is a filter medium having a first nonwoven fabric layer, and a plurality of convex portions in which a fiber bundle of the nonwoven fabric is partially raised on one side of the nonwoven fabric layer, or a plurality of the convex portions in one row. A plurality of wrinkles formed side by side are regularly present, the height of each convex portion is 1.2 to 5.5 mm, and the basis weight is 180 to 550 g / m ² . It is preferable that the wrinkles are present in the width direction of the filter medium so that there are 0.8 to 4.7 rows per 10 cm, or the protruding portions facing each other when pleated are in contact with each other. . Moreover, it has the laminated structure of two or more different layers by which the 2nd nonwoven fabric layer whose fiber density is lower than the said nonwoven fabric layer is laminated | stacked on the side in which the convex part of the said 1st nonwoven fabric layer is not formed. Is preferred. Furthermore, the first nonwoven fabric layer contains the first fibers and fibers having a melting point lower than that of the first fibers, and the blending ratio of the low melting point fibers is 40 to 100% by weight in 100% by weight of the filter medium. Preferably there is. In addition, it is preferable that the 1st fiber which comprises the said convex part or the collar is fuse | melted via the low melting point fiber, and the number of the said convex parts is 2-6 per 1 cm of collar length In a more preferred embodiment, the cross-sectional area of the convex portions is ² to 10 mm ² , and each convex portion is pleated so as to come into contact with the opposing convex portions.
Furthermore, the present invention also includes a method for producing a filter medium, which includes a step of performing a squeezing process on a nonwoven fabric serving as a base material. In the squeezing process, it is preferable to perform needle punching using a fork needle having a needle count of 25 to 40, and the needle depth of the needle is more preferably 5.2 to 9.5 mm. .

  According to the present invention, on one side of the filter medium, since the convex portions (ribs) in which the fiber bundles of the nonwoven fabric are partially raised are present so as to face each other, when pleating, Since this convex part (ridge) serves as a support for the pleats and can maintain the form of the pleats, the ventilation resistance can be suppressed at a low level, which makes it possible to extend the life of the filter medium. Moreover, when the low melting point fiber is mixed with the filter medium, the strength of the convex portion (rib) can be further increased.

  In the present invention, the “convex portion” is a state in which the fiber bundle protrudes from the nonwoven fabric surface, and more specifically refers to a state in which the fiber bundle protrudes once with a fork needle. In addition, “畝” is a series of a plurality of the convex portions. In addition, there are a case where the “ridge” is formed by the continuous continuous convex portions and a case where the convex portions appear at a predetermined cycle and a predetermined interval. Theoretically, if there are two convex portions, surface contact of the filter medium can be avoided, but there are a plurality of convex portions (for example, 6 to 10 or more per mountain when pleats are formed). It is preferable to form it. Further, the “convex portion” and the “ridge” are preferably a fiber bundle having a shape that makes a cord of a cord carpet smaller, or a fiber bundle formed continuously.

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 perspective view before the pleating process of the filter medium which concerns on this invention. It is a schematic sectional drawing which shows an example of the filter medium which concerns on this invention after a pleating process. It is a schematic sectional drawing which shows an example of the filter medium which concerns on this invention after a pleating process. It is a schematic sectional drawing which shows an example of the conventional type filter medium after a pleating process.

  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 (an arrow indicates a direction in which air flows into the filter medium). The filter medium 10 is a filter medium having a first non-woven fabric layer, and is characterized in that a plurality of convex portions 3 a in which a fiber bundle of the non-woven fabric is partially raised exist on one side of the non-woven fabric layer 1. As shown in FIG. 1, the protrusion 3 a may be formed by a plurality of protrusions 3 a gathering to form a row (in the present invention, the row formed by the plurality of protrusions 3 a is denoted as “畝”. Called). The convex portions 3a are formed on one side of the filter medium 10 at such an interval that the convex portions 3a existing on the opposed surfaces of the folded filter medium can be contacted with each other when the filter medium 10 is pleated. It may be. The convex portion 3a has a shape in which the center of the fiber bundle is most raised, and in particular, the convex portion 3a has a circular bell-shaped bottom and a fiber bundle in a loop-shaped bell shape or bowl shape (a shape that rises in a half-moon shape). Is preferred. Adjacent convex portions 3a may partially overlap the bases of the convex portions 3a, but may not overlap.

  The convex part 3a consists of the fiber which comprises a filter medium. Although the manufacturing method of the convex part 3a is not specifically limited, For example, it can form by extruding the fiber of each layer which comprises the filter medium 10. FIG. Thus, when the convex part 3a is formed by extruding a fiber, since the convex part 3a is finished rigidly, sufficient strength can be exhibited. In addition, unlike the method of forming a protruding portion by compressing a filter medium such as embossing, when the protruding portion 3a is formed by extruding the fiber as in the present invention, the air permeability is not lowered due to the presence of the protruding portion. Particularly preferred.

  FIG. 2 shows a perspective view of the filter medium 10 according to the present invention before pleating. In FIG. 2, ridges 3b are formed in the filter medium 10 in three rows on the surface 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 a direction in which the ridges 3b are arranged in a row (referred to as a brewing direction x) to form ridges.

  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 each ridge is opposed to itself, so that the fold of the valley fold (the brewed surface on which the ridge of the filter medium 10 is formed is front) On the processed surface, there is a contact point 4 where the convex portions present on one ridge contact each other. 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 shows an example in which the convex portion 3a is partially formed on one surface of the filter medium 10 and pleated so that the convex portions face each other and come into contact with each other. As long as the projecting parts 3a facing each other come into contact with each other, the contact point 4 serves as a support for the pleats. Therefore, the projecting part is formed on the mountain fold side of the pleats (the ridge of the filter medium 10 is formed). Even if the processed surface is not formed on the surface), the effect is sufficiently exhibited. Although the space | interval between convex parts is suitably adjusted according to a pleat width, For example, as for the top space | interval of the convex part 3a which contacts, the bottom face width +/- 1-5mm of a convex part is preferable.

  On the other hand, FIG. 5 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 convex portions facing each other contact each other. 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 a V shape to a U shape. 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.

  In other words, according to the present invention, since the convex portion 3 a is formed on the filter medium 10, the filter medium 10 does not come into surface contact with adjacent pleats due to the inflowing wind pressure due to the presence of the contact point 4 even without a fixture. Since the opening of the pleats can be suppressed, the shape of the pleats can be maintained for a long time. Therefore, various advantages such as a longer filter life of the filter medium 10 and easier recycling can be expected.

  The convex part formed by the squeezing process has a height of 1.2 to 5.5 mm, more preferably 1.5 to 4.5 mm, and still more preferably 1.7 to 3 mm. If the height of the convex portion is less than 1.2 mm, the contact point of the convex portion will not be clear even if pleating is performed, and the pleat will open, increasing the airflow resistance, which is not preferable. On the other hand, if the height of the convex part exceeds 5.5 mm, the contact area of the convex part increases, the convex part falls down, or the convex part is crushed by being pushed by another convex part that contacts the convex part. There is a risk of it.

  Moreover, when several convex part forms a wrinkle, the number of wrinkles is 0.8-4.7 row / 10cm, for example, More preferably, it is 1.5-4 row / 10cm, More preferably, it is 2 ~ 3 rows / 10 cm. If the number of wrinkles per 10 cm is less than 0.8 rows, the distance between the wrinkles becomes too wide, and the filter medium is likely to cause surface contact, which is not preferable. Moreover, when the number of hooks per 10 cm exceeds 4.7 rows, the area occupied by the hooks increases, and there is a possibility that the ventilation resistance increases. 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 addition, the number of convex portions in the protruding direction is preferably 2 to 6 / cm, more preferably 3 to 5 / cm, in relation to the cross-sectional area of the convex. If the number of projections occupying the brewing direction is less than 2 pieces / cm, the projections may not be in contact with each other when the pleating process is performed on the filter medium, and there is a possibility that no contact point will be generated. On the other hand, if it exceeds 6 pieces / cm, the filter medium impairs the mechanical strength, and a lot of through-holes are formed between the fibers by the squeezing process, which may reduce the collection efficiency.

Further, the cross-sectional area of the projections is preferably 2 to 10 mm ^2, more preferably 3 to 8 mm ^2. If the cross-sectional area of the convex portion is within the above range, it is preferable because a rigid convex portion that does not easily collapse can be formed. In addition, the cross-sectional area of a convex part can be measured by the method shown in the column of an Example.

  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 more than the first nonwoven fabric layer on the side where the convex portions of the first nonwoven fabric layer 1 are not formed. It is preferable to have a laminated structure of two or more different layers in which the second nonwoven fabric layer 2 having a low density 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. The first nonwoven fabric layer has a high density because fine fibers are mixed (dense layer), and fine particles that could not be captured by the second nonwoven fabric layer can be filtered. 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 lower density layer (coarse layer) than 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 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 low that it is difficult to form a desired rigid ridge (convex portion). 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>
The nonwoven fabric used as the base material of the filter medium will be described. The structure of the nonwoven fabric used as a base material is not specifically limited, It can change suitably with the use of the filter medium obtained, the required performance (size of to-be-filtered material), etc. 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, fine dust that could not be collected by the second nonwoven fabric layer can be collected, and the convex portion can be made rigid, so that the pleats of the filter medium 10 can be opened. Can be suppressed. However, when the fineness of the first non-woven fabric layer is less than 0.8 dtex, the rigidity of the convex portion becomes poor and it becomes difficult to form a rigid convex portion. 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 for 2nd nonwoven fabric layers 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 convex portions and wrinkles made of fiber bundles.

  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.) Polyamide fibers such as polyacrylonitrile fibers, acrylic fibers such as polyacrylonitrile-vinyl chloride copolymer fibers; polyolefin fibers such as polyethylene fibers and polypropylene fibers; various synthetic fibers such as polyphenylene sulfide fibers; rayon, polynosic, cupra, lyocell And the like; natural fibers such as cotton, pulp, kapok, hemp, hair, silk, etc. can be used. Among them, polyester fiber is preferably used because of a good balance between performance and price, and polyethylene terephthalate fiber is particularly preferable. 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 fibers that have been subjected to various treatments, since the effect can be obtained from the stage of manufacturing the nonwoven fabric.

  Further, in order to impart dimensional stability and necessary rigidity to the filter medium, the fibers constituting the filter medium include fibers forming a skeleton of the filter medium and fibers having a melting point lower than that of the fibers (low-melting fibers. A composite fiber having a portion 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. When the filter medium is formed from two or more layers of nonwoven fabric having a density gradient, it is preferable that the low melting point fiber is contained in at least one layer, and more preferably in all the nonwoven fabric layers constituting the filter medium. preferable.

  In the present invention, it is important to make the convex portion rigid in order to prevent the convex portion from falling or denting. The blending ratio of the low melting point fiber is preferably 40 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 because the melted and solidified low melting point fiber does not lower the air permeability of the filter medium more than necessary, and the convex part can be made rigid.

  The melting point of the low-melting fiber is preferably, for example, 30 ° C. or less from the melting point of the fiber that forms the skeleton of the filter medium. 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 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 fiber is preferably 150 ° C. or less, more preferably 100 ° C. or less from the melting point of the fiber so that the low-melting 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.

  Examples of the low-melting fiber include 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 modified polypropylene fibers can be used. In the present invention, the composite fiber is preferable so that the resin in the low melting point portion melts and acts as an adhesive, and the fiber in the high melting point portion functions as a fiber constituting the filter medium, and those having a core-sheath structure are particularly 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 is within the above range, 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 of manufacturing a nonwoven fabric to be a base material (nonwoven fabric manufacturing process),
A step of performing a squeezing process on the non-woven fabric obtained by the non-woven fabric manufacturing step (sieving step),
If necessary, a step of heating the filter medium obtained in the brewing step (heat treatment step),
It has the feature in the point containing. Thus, the method for producing a filter medium according to the present invention is characterized in that it includes brewing.
The squeezing process is similar to a method of forming a cord in a cord carpet. Specifically, a plurality of fibers constituting the nonwoven fabric are continuously converged and projected in the width direction and the length direction of the filter medium. A processing method for forming a part (). In addition, in this invention, it is not necessary to form a convex part (ridge) over the nonwoven fabric front surface. The squeezing process is not particularly limited as long as it can form a protrusion with high protruding fibers on the air outflow side surface of the substrate.

  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 or a spunlace method (a hydroentanglement method); 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. 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 .

  The method for forming the convex portion is not particularly limited as long as the method can form the convex portion. Above all, needle punching can be said to be a simple processing method because it is not necessary to introduce an apparatus other than the nonwoven fabric manufacturing apparatus because the apparatus for manufacturing the nonwoven fabric can be diverted compared to the surface processing of embossing. Further, unlike embossing, needle punching is preferable because the convex portions are not consolidated, and the interfiber gap does not become higher than necessary, and the ventilation resistance can be kept low.

  When carrying out squeezing by needle punching, it is preferable to use needles with needle numbers 25 to 40 (preferably 30 to 36). When it exceeds 40, a convex part will become small and the effect of convex part matching will become scarce. On the other hand, when the number is less than 25, the needle is too thick and a through-hole is easily formed, the collection efficiency is lowered, the surface of the filter medium is rough, and it is difficult to perform uniform filtration, which is not preferable. The needle is not particularly limited as long as it is a needle capable of protruding a fiber bundle, but a fork needle or a crown needle is preferable, and a fork needle is particularly preferable.

  The height of the convex portion of the filter medium depends on the needle depth of the squeezing process and the thickness of the non-woven fabric serving as the base. In order to adjust the height of the convex portion to a desired range, the needle depth of the needle is preferably, for example, 5.2 to 9.5 mm, more preferably 5.5 to 9 mm, and still more preferably 5.7. -7.5 mm.

Furthermore, if the needle is fixed to the needle board, a wide range of squeezing can be performed. In consideration of the number of ridges and the spacing between the convex portions of the board, when the ridges are formed by the convex portions, the number of ridges is 0.8 to 4.7 rows per 10 cm of the filter medium width, and 5 needles are arranged in one row of ridges. If it is fixed so that it is ˜15 (more preferably 6 to 10), it is easy to form a desired wrinkle. The number of penetrations is preferably 3 to 10 units / cm ² (more preferably 4 to 8 units / cm ² ). The squeezing process is performed by inserting a needle from the second nonwoven fabric layer side.

In order to make the texture of the filter medium harder and improve the strength of the filter medium, and to make the formed convex part more rigid, when blending low melting point fibers, heat treatment is performed after brewing . The heating temperature is preferably T _L +35 (° C.) to T _L +110 (° C.), more preferably T _L +55 (° C.) to T _L +90 (° C.) with respect to the melting point T _L of the low-melting fiber mixed. It is. Specifically, it is preferably 175 to 225 ° C, more preferably 190 to 220 ° C. 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. In the present invention, since the heat treatment is performed after the squeezing process, the first fibers constituting the convex portion or the heel are in a state of being fused via the low melting point fiber after the squeezing process.

  The formed filter medium may be heat-treated by passing through a heat treatment machine (for example, a circulating hot air dryer) adjusted to a desired temperature. At this time, in order to adjust the size of the filter medium, the width and Heat treatment is preferably performed while maintaining the thickness.

  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. Although the pleating method is not particularly limited, it is preferable to pleat with the convex forming surface of the filter medium on the inside because it is easy to confirm the butting of the convex. The pitch and the peak height are preferably 10 to 25 mm and the peak height is preferably 30 to 100 mm.

  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: Conforms to JIS L1913 6.2.
2. Thickness before and after squeezing processing; conforming to JIS L1913 6.1.
3. Projection area: Measure the bottom length of the projection with a JIS steel ruler or caliper, assume the bottom shape to be a circular cross-section, and use the measured length as the diameter of the circular cross-section. Was calculated.
4). 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 creation: After filtering the filter medium obtained by the method described in Examples and Comparative Examples with a width of 110 mm, the ridge was formed at a height of 50 mm and a pitch of 16 mm with the convex formation surface of the filter medium 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).

Example 1
(1) Production of Needle Punched Nonwoven Fabric A dense polyester fiber having a fineness of 2.2 dtex and a fiber length of 51 mm, 10% by weight of regular polyester, a fineness of 2.2 dtex, a fiber length of 51 mm, a melting point of 160 ° C. and a core-sheath type polyester composite fiber of 90% by weight A web for a layer (first nonwoven layer) was prepared. 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 160 ° C. Carding and lapping were performed to prepare a web for the coarse layer (second nonwoven fabric layer).
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 . To obtain a needle punched nonwoven fabric.
(2) Saddle processing Next, the obtained needle punched nonwoven fabric was planted with 2 forks / 10 cm in the width direction and 8 in the flow direction in a row using a fork needle (organ FPK2-25) with a needle count of 32. Using a board exclusively for brewing, scouring was performed from the coarse layer side with a needle depth of 5.5 mm and a penetrating number of 6 pcs / cm ² . As a result, a filter medium made of a fine cord-like needle punched nonwoven fabric was produced.
(3) Heat treatment Subsequently, 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, thereby producing a filter medium. An element was produced using this filter medium, and the ventilation resistance was measured.

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.

Examples 2-3 and Comparative Examples 2-3
A filter medium was produced in the same manner as in Example 1 except that the conditions of the squeezing process were changed as shown in the table to change the height of the convex portion, and the heat treatment was performed under the conditions shown in the table. In addition, even if the needle punch nonwoven fabric before the squeezing process obtained in the step (1) has the same basis weight, the thickness may vary.

Examples 4-6, Comparative Example 4
A filter medium was produced in the same manner as in Example 1 except that the conditions of the squeezing process were changed as shown in the table, the number of hooks was changed, and the heat treatment was performed under the conditions shown in the table. In addition, even if the needle punch nonwoven fabric before the squeezing process obtained in the step (1) has the same basis weight, the thickness may vary.

Examples 7-8, Comparative Examples 5-6
A filter medium was produced in the same manner as in Example 1 except that the basis weight of the dense layer / rough layer web was changed and the squeezing process and the heat treatment were performed under the conditions shown in the table.

In Comparative Example 1, since the squeezing process was not performed, the value of the ventilation resistance is large.
In Comparative Example 2, since the convex portion was too low and the filter media contacted each other, the value of the ventilation resistance was increased.
In Comparative Example 3, the convex portion was too high, and the convex portion fell down due to another convex portion that contacted.
In Comparative Example 4, the value of the separately measured tensile strength was lowered, and there was a problem in terms of strength.
In Comparative Example 5, the basis weight was small and the filter medium was thin, so that the particles could not be collected sufficiently.
In Comparative Example 6, since the basis weight was too large, the ventilation resistance was increased.

  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)
3a Convex 3b 畝 4 Contact point 10 Filter medium x Extruding direction

Claims (10)

A filter medium having a first nonwoven layer,
On one side of the non-woven fabric layer, there are regularly a plurality of protrusions in which the fiber bundles of the non-woven fabric are partially raised or a plurality of wrinkles formed in a row in the protrusions,
A filter medium characterized in that the height of each convex part is 1.2 to 5.5 mm and the basis weight is 180 to 550 g / m ² . The ridges are present in a row of 0.8 to 4.7 per 10 cm in the width direction of the filter medium, or
The filter medium according to claim 1, wherein the convex portions that face each other when pleated are in contact with each other.   2. The laminated structure of two or more different layers in which a second nonwoven fabric layer having a fiber density lower than that of the nonwoven fabric layer is laminated on the side where the convex portions of the first nonwoven fabric layer are not formed. Or the filter medium of 2.   The first nonwoven fabric layer includes a first fiber and a fiber having a melting point lower than that of the first fiber, and a blending ratio of the low melting point fiber is 40 to 100% by weight in 100% by weight of the filter medium. Item 4. The filter medium according to any one of Items 1 to 3.   The filter medium according to claim 4, wherein the first fibers constituting the convex portion or the ridge are fused via the low melting point fibers. The number of the convex portion is a 2-6 per Secho of 1 cm, the filter medium according to any one of claims 1 to 5 cross-sectional area of the convex portion is 2 to 10 mm ^2.   The filter medium according to any one of claims 1 to 6, wherein each convex portion is pleated so as to come into contact with a convex portion facing each other. A method for producing a filter medium according to any one of claims 1 to 7,
A method for producing a filter medium, comprising a step of subjecting a nonwoven fabric to be a base material to a squeezing process.   The method for producing a filter medium according to claim 8, wherein, in the squeezing process, needle punching is performed using a fork needle having a needle count of 25 to 40.   The method for producing a filter medium according to claim 8 or 9, wherein the needle depth of the needle is 5.2 to 9.5 mm.