DE60219293T2 - Non-woven fabric for a filter and filter for a motor - Google Patents

Description

These The invention relates to nonwoven fabrics for Filters adapted for separating and removing dusts in the air, etc. are, and in particular nonwoven fabrics for filters, which are an excellent Retention volume for captured Materials such as e.g. dusts and carbon particles, and have a high purification efficiency for one can sustain for a long time, a method of making such nonwoven fabrics and filters where such fiber webs are used.

So far was used as a method of providing clean air used a method in which air, dusts, etc., contains, for Removal of dusts, etc., was passed through filters. The power needed for filters is required depends from using the filters. In view of this, as Materials for Filter various materials, such as Paper and fibers, used. If filter for Air-absorbing engines for Motor vehicles used is a fortune to maintain one high cleaning efficiency and to achieve a high cleaning efficiency required.

In Recently, nonwoven fabrics of the density gradient type have been used as filters with a better fortune to Maintain cleaning efficiency by removing and holding of dusts proposed. A non-woven fabric of the density gradient type is a non-woven fabric, in the fibrous layers, each one different Have fiber density, one such layer over the other are arranged so that the density in the lamination direction of fibrous layers is gradually varied. Each fibrous Layer is composed of fibers with different fiber diameters. In particular, a nonwoven fabric of the density gradient type is constructed that the density of each fibrous layer in the lamination direction the fibrous layers from a surface of the nonwoven fabric to the opposite surface of which gradually increases that the mixing ratio of the Fibers constituting the fibrous layer with respect to each changed fibrous layer becomes. In such a nonwoven fibers are by connecting or Adhering with various binders or by adding adhesive Fibers and by fusing a portion of the adherent fibers, so that the fused adherent fibers on the other fibers stick together, tied together.

Even the above-described non-woven fabric of the density gradient type can not provide sufficient cleaning efficiency of removing microparticles, such as. Carbon particles, provide. Accordingly, became a technique for improving the cleaning efficiency by increasing the Density of the fibrous layers proposed. Some examples for techniques of elevating The fiber density is such that the size of the pore (dimension of the Space) defined by adjacent fibers Use of fibers with a very small diameter reduced is, and that the pore size by impregnation is reduced by resin in the fibers. If such a fiber fleece is used as a filter, it is very likely that at the filter clogging the gaps (pores) in the fibrous layers results, even if a cleaning efficiency of removing Microparticles, e.g. of carbon particles becomes. As a result, the life of such a filter is shortened. Furthermore, can the increase the density of the fibrous layer, the retention volume of the filter for trapped dusts and Reduce carbon particles, resulting in a reduction in the lifetime of the filter leads.

In an attempt to solve the above-mentioned problems, various nonwoven fabrics for filters have recently been proposed. For example, this describes Japanese Unexamined Patent Publication No. HEI 9-192427 the following technique. More specifically, at least two fibrous layers each composed of thermosetting hydrophobic fibers and non-thermosetting hydrophobic fibers are layered one over the other so that the fibrous layer on an air outlet side has an average fineness smaller than that of the fibrous layer on an air intake side. The nonwoven fabric thus prepared is washed with water to reduce the content of oil agent adhering to the fibers. Thereby, a nonwoven fabric having an improved cleaning performance of capturing sand dusts is generated, while clogging in the fibrous layers is suppressed by the accumulated dusts.

The Japanese Unexamined Patent Publication No. SHO 50-31476 describes a nonwoven fabric prepared by preparing a web containing at least 30% of composite fibers so constructed that fibers made of a polymer which can form two kinds of fibers having a melting point difference of 20 ° C or more in a series, subjecting the web to a needling process under conditions wherein the active needle count is in the range of 40 to 150, and subjecting the thus processed web to a heat treatment at a temperature not lower than a melting point of the low melting point and below the composite fiber the melting point of the Kom component of the high melting point composite fiber.

The Filter for Motor vehicle engines require a high retention volume of dusts, etc., as well as a cleaning efficiency with respect to dusts, etc. considering the requirement that the filters used for a long time become. Furthermore, in view of the recent Requirement for a reduction in the need for a production of fiber webs, which has a high cleaning efficiency and a high retention volume for dusts, etc., with a lower number of fibrous layers and an excellent Can provide moldability and integrated formability increased.

in the In view of the foregoing, it is an object of this invention Fiber fleece for Filters that have a high capture rate with respect to dusts and carbon particles for one can sustain for a long time, with a great Retention volume in terms of Dust and carbon particles while a clogging suppressed is a method for producing such nonwoven fabrics and filters for engines, in which such nonwoven fabrics are used to provide.

According to one aspect of this invention, the nonwoven fabric is constructed of two or more different types of fibrous layers arranged one above the other. The nonwoven fabric has an average pore size of from 30 μm to 60 μm inclusive and a total pore area of 0.011 cm ² / cm ² or more with respect to the entire surface of the nonwoven fabric. The average pore size is calculated according to the bubble point method defined in ASTM F-316-80 using a Coulter Porometer II. Each fibrous layer is composed of adhesive fibers and fibers to be bonded to each other, and the adhesive fibers and the fibers to be bonded to each other are bonded to each other by a heat treatment.

The Inventive nonwoven fabric represents an excellent initial Cleaning efficiency of trapping dusts, especially carbon particles, the for Fiber fleece for Filter is required in various air purification and Fluid processing devices are used, in particular for filters for air-intake Engines of motor vehicles, as well as a large retention volume with respect to trapped Materials such as e.g. Dust and carbon particles, ready. Therefore, it is less likely that the nonwoven fabric according to the invention causes a clogging and it can be a large amount of dusts and Catch carbon particles and cleaning efficiency for a long time Time maintained. Furthermore, the inventive nonwoven fabric the outstanding cleaning efficiency with only three layers ready and has an excellent formability, which in terms of Reduction of production costs is advantageous. The nonwoven fabric according to the invention is as a filter for an air-intake engine of a motor vehicle suitable at which requires a high cleaning performance in a compact size is.

As a result of extensive research and investigation, the inventors of this application have found that nonwoven fabrics having an average pore size of 30 to 60 μm and a total pore area of 0.011 cm ² / cm ² or more are produced by arranging at least two fibrous layers one above the other provide excellent cleaning efficiency of removing dusts and carbon particles contained in a gas, as well as a large retention volume of holding the trapped dusts and carbon particles.

The average pore size of the nonwoven fabric is the value calculated according to the bubble point method in ASTMF-316-80, using a Coulter Porometer II (a Product of Coulter, Inc.). The measurement by the Coulter porometers II is made by immersing a piece of non-woven fabric in a liquid, while the surface of the nonwoven fabric having a high fiber density at a lower fiber density Side of the measuring device is arranged, and the opposite surface of which has a low fiber density, on an upper side of which is arranged, blowing bubbles of gas on the upper surface of the Nonwoven fabric while the gas pressure increases is, and measuring the pore size as a relationship between the pressure of the supplied Gas and the surface tension the liquid, on the bottom surface (other side) of the non-woven fabric is performed. Regarding the Operation and measurement of the Coulter Porometer II followed The personnel involved in the experiments are given the operating manual the measuring device.

It should be noted that the "total pore area" is the value calculated using the Coulter Porometer II and the total area of the pores per unit area (unit: cm ² / cm ² ) obtained by integrating the areas of the pores with the same diameter based on each pore size (diameter) and summing up the integration results.

If the average pore size exceeds 60 μm, microparticles, e.g. Carbon particles, easily through the pores through, so no sufficient initial Cleaning efficiency of the capture of the microparticles provided can be. In contrast, if the average pore size smaller than 30 μm It is likely that the nonwoven fabric is such average pore size, Clogged in a short time, although the initial Cleaning efficiency of the capture of microparticles can be increased can. As a result, the nonwoven fabric with such a small average pore size none high cleaning efficiency for maintained a long time.

When the total pore area is less than 0.011 cm ² / cm ² , a nonwoven fabric having such a small total pore area can not provide a sufficient retention volume with respect to trapped dusts and microparticles such as carbon particles. Preferably, the total pore area is 0.012 cm ² / cm ² or more, more preferably 0.013 cm ² / cm ² or more and especially 0.018 cm ² / cm ² or more. The larger the total pore area, the larger the dusts / carbon particle retention volume of the nonwoven fabric, thereby improving the ability to maintain a high cleaning efficiency for a long time. Accordingly, there is no value for the upper limit of the total pore area as long as the average pore size is in the above-mentioned range.

The filter using the nonwoven fabric of the present invention has an initial cleaning efficiency defined by JIS D 1612 of 95% or more, preferably 96% or more, and a final dust / carbon particle trapping rate determined by JIS D 1612, of 99.4% or more, preferably 96% or more. The filter also has a retention volume of dusts defined by JIS Z 8901 of 230 g / 0.1 m ³ or more, and a retention volume for carbon particles defined by JIS Z 8901 of 3.6 g / 0 , 1 m ³ or more. With these characteristics, the filter can maintain a high cleaning performance for a long time.

The Inventive nonwoven fabric with the above average pore size and the The aforementioned total pore area can preferably by Arranging a plurality of fibrous sheets (webs), respectively composed of adhesive fibers and fibers to be bonded together are those described below, these two types of fibers uniformly distributed, one over the other, joining the fibrous leaves to an integrated fiber web part by physical bonding, such as. a needling process, subjecting the fiber web part a heat treatment by thermally adhering the fibers to each other, applying a liquid on the surface the nonwoven fabric having a high fiber density and treating of the nonwoven fabric are produced with a heat roller.

below will be an example of a method for producing the fiber webs according to the invention for filters described in detail. As long as the fiber webs according to the invention can be produced with the above properties is the process for producing the fiber webs according to the invention not on the Limited production method described below.

Preferably are the fiber components, which are each fibrous layer of the nonwoven fabric according to the invention such that part of one type of fiber is fused, so that it sticks to the other fiber, causing them in the application a heat treatment, The later is described to be interconnected. Connecting the Fibers using the fused fibers allows the Providing a fiber fleece that has sufficient rigidity against bending in the production of wrinkles, described later (hereinafter, this type of property of the nonwoven fabric of the present invention as "moldability"), and in forming the fibrous web into an integrated fibrous nonwoven article with a support frame in that a part of the fiber fleece is formed as a carrier frame (Hereinafter, this type of property of the nonwoven fabric of the present invention will be described as "integrated formability").

It is understood that there is a method of adhering the fibers to each other using a known binder such as an emulsion type binder. However, the use of the emulsion type binder has the following disadvantages. Adding an excessive amount of the binder makes it difficult to adjust the pore size in an appropriate range. Further, it is likely that the use of a binder causes clogging, thereby shortening the life of the filter. In addition, cracks are likely to be generated in the production of nonwoven fabric articles, thereby creating defective nonwoven fabric articles. In particular, in the case of using a binder, integrated molding can not be performed as described later. In view of the above, in the embodiment of this Invention, a binder not used.

in the In view of the above circumstances, the fibrous layer becomes of the fibrous web according to the invention of an adhesive fiber and a fiber to be bonded together produced.

The Adherent fiber is a fiber that has the property that it starts to melt in the temperature range of 100 to 220 ° C. A Such adhesive fiber may be a single fiber or a composite or Be mixed fiber. The single fiber comprises a polypropylene fiber, a polyethylene fiber and a copolymer fiber of ethylene-vinyl acetate. The composite fiber comprises a side by side type or a sheath-and-core type. Because an excessive melting of fibers reduces the bond strength between fibers it prefers to use a composite fiber instead of the single fiber. If the adhesive fiber is formed from a composite fiber, is recommended to use a composite fiber of the sheath-and-core type, composed of a high melting point component (corresponding to a Core of the fiber), which has a melting point of around 30 ° C or more is higher as the melting point of a low melting point component, and the low melting point component (corresponding to a Cover of the Fiber) having a melting point in the range of 100 to 220 ° C, is composed. A combination of a modified polyester and a polyester is preferred as such a sheath-and-core type composite fiber. It goes without saying such a sheath-and-core type composite fiber is a composite fiber made of polypropylene (core) and polyethylene (shell), a composite fiber Nylon-66 (core) and nylon-6 (shell) and a composite fiber of polyester (core) and polyethylene (shell).

The mixing ratio of the high melting point component to the low component Melting point in the composite fiber is not specifically limited. When Such a composite fiber will be available on the market Fibers used.

The fiber to be bonded, which is a fiber of a type which is is different from the adhesive fiber, is a fiber used in the Melt-starting temperature of the above-mentioned adhesive fiber not begins to melt. Preferably, the melting point difference is between the adhesive fiber and the fiber to be bonded together at least 30 ° C or more. Preferably, the fiber to be joined is one Single fiber. The monofilament comprises polyamide fibers such as e.g. Nylon, and polyester fibers.

The mass ratio the adherent fiber to the fiber to be joined, the each fibrous layer is preferably in the range of 50:50 to 30:70. The higher the Proportion of adherent fiber is, the more the pores can be clogged or the total pore area be reduced due to excessive melting of the adhesive Fiber. It should be noted that the length of each fiber is not special limited is. It can known fibers of any fiber length are used.

According to the embodiment This invention may be a fibrous layer according to a known methods are produced as long as the mixing ratio of the adhesive fiber to the fiber to be bonded in the above mentioned area lies. The nonwoven fabric according to the invention is arranged by arranging at least two fibrous layers, each of them by mixing obtained the above-mentioned fibers in the ratio indicated one over the other made. As long as the aforementioned average Pore size and the above-mentioned total pore area are available, are the thickness of the fibrous web, the thickness of each fibrous layer and the number the fibrous layers forming the fibrous web are not limited. Therefore can the thickness and the number of fibrous layers according to their Application to be set optimally. An increase in the Thickness and the number of fibrous layers over a permissible range however, the manufacturing cost of the nonwoven fabric may increase. Accordingly, it is preferably, the density of the fibrous layer and the diameter of To adjust fibers in such a way that the average Pore size and the Total pore area, which are defined in the manner described above, with a lower number of fibrous layers can be obtained.

According to the embodiment of this invention, it is preferable to form the nonwoven fabric such that the density of the fibrous layer is gradually or continuously increased in the lamination direction of the fibrous layers from an inlet side of the feed gas of the nonwoven fabric through which a supplied gas is drawn to an outlet side the supplied gas through which the supplied gas is discharged, increases. Hereinafter, the fibrous layer having a high fiber density will be referred to as a "high density layer" and the fibrous layer having a low fiber density will be referred to as a "low density layer". In the nonwoven fabric having such a density gradient, part can With a relatively large diameter, such as dusts, are trapped in the fibrous layer of the inlet side of the gas supplied (namely in the low-density layer). Thereby, clogging in the fibrous layer can be suppressed from the outlet side of the supplied gas (namely, the high-density layer). Further, in this arrangement, dusts may be retained in a manner that disperses dusts having different particle sizes (diameter) in the thickness direction (lamination direction) of the nonwoven fabric in accordance with the size of the particles. With this arrangement, the retention volume of dusts per unit area can be increased.

It is preferred, a fiber with a small average denier or denier as a component for the high-density layer to use to increase the fiber density of the high-density layer increase, while the layer thickness as low as possible is held. Further, it is preferable to have a fiber with a large average Denier value as a component for to use the low density layer to the requirement the capture of relatively large To fulfill particles. In view of this, it is preferable to the average denier value the fibrous layers gradually or continuously in the Thickness direction or layering direction of the nonwoven fabric of the Inlet side of the supplied Gas (side of the low density layer) to the outlet side of the supplied Gas (side of the high-density layer) to reduce.

The method of bonding the layered fibrous layers to produce the nonwoven fabric of the present invention is not particularly limited. However, an integrated formation by physical bonding is employed to ensure the formability of the nonwoven fabric. Physical bonding means that the fibrous layers are joined together by interweaving the fibers in the adjacent layers. Preferred examples of methods of interweaving the fibers according to such physical bonding are a needle punching method and a water jet processing method. As for the physical bonding such as needle punching method and water jet processing method, it is preferable to perform a needle punching method (water jet processing method) on the high-density layer side of the nonwoven fabric for the following reasons. As compared with the case where a needle punching operation is performed on the side of the low-density layer, the needle punching process on the high-density layer side may be accompanied by collapse or deformation of the pores accompanied with the braiding, as well as by the interlacing suppress unwanted expansion of pore size. By this arrangement, the average pore size and the total pore area defined above can be ensured, thereby reducing the initial cleaning efficiency with respect to microparticles such as microparticles. As carbon particles, is suppressed. The requirements for performing a needling process are not particularly limited. However, excessive increase in needling depth may undesirably increase pore size (diameter). On the contrary, if the needling depth is excessively reduced, sufficient braiding can not be obtained. In view of this, it is generally preferable to set the needling depth in the range of 8 to 15 mm. As needle for the needling process, any type of needle used in the known needling can be used. However, since the needle diameter is larger than the diameter of the pores in the high density layer, the pore diameter in the high density layer may increase by the needling process. In view of this, it is preferable to set the number of needles (the number for penetration) per unit area in the range of 40 to 100 parts / cm ² in order to suppress undesirable widening of the pore diameter and to perform a sufficient entangling operation.

The Nonwoven fabric becomes after physically bonding a heat treatment subjected to which the adhesive fiber and to be bonded together Fiber are bound together. The heat treatment process is not specifically limited. As long as the temperature for the heat treatment identical to the melting start temperature of the adherent fiber or higher than this is and is lower than the melt start temperature of the joints to be bonded Fiber, can these fibers are bound together.

It is likely that the surface of the high-density layer after the heat treatment is in a fuzzy state. In view of this, after the heat treatment, calendering processing is performed in which the high-density layer of the non-woven fabric contacts a heating roller which is heated at a temperature identical to or higher than the melt-starting temperature of the low melting point component of the fiber to make the surface configuration smooth, to ensure certain dimensions for the nonwoven fabric and to increase the fiber density. Contacting the heating roller with the surface of the high-density layer in the calendering processing enables the provision of a desired surface state by bonding the fuzzy fibers in the layer high density and increases the fiber density of the surface of the high-density layer.

It is likely that the contact of the heating roller with the surface of the High-density layer in calendering processing the adhesive Part of the adherent fiber and the fiber to be bonded merges, so that they are bound (of course, will be another adhesive part, such as the adherent part of an adherent fiber and an adherent fiber, fused). Then the merged Part cause a re-binding of the fibers. Because the surface of the High density layer through the roller in a pressed state can be brought, an excessive bond caused or the fuzzy fibers bound to the roll surface can to the fibers of the surface bonded to the high-density layer. As a result of this operations For example, the contact of the heating roller with the surface of the high-density layer in calendering processing to a reduction of the pore diameter, a reduction in the number of pores or clogging of the Pores on the surface lead the high-density layer, or he can the pore diameter by re-bonding the Fibers in unwanted Expand way. Because the fiber fleece, which is such a treatment has undergone a reduced total pore area, can the use of such a nonwoven fabric as a filter, so as it is present, not a sufficiently large retention volume for dusts, in particular Carbon particles, as described below becomes.

to solution of the above problem, it is preferable before the calendering processing a liquid on the surface Apply the layer with high density. Applying a liquid on the surface the high-density layer allows microparticles of the liquid evaporated by heating the liquid have been generated to adhere to the fibers which the surface of the Forming a high-density layer. The adherence of the evaporated microparticles the liquid blocks the reduction of the pore diameter, the reduction the number of pores and the clogging of the pores resulting from fusing the adhesive part of the adhesive fiber and the adherend to each other Fiber results in re-binding and bonding the fuzzy fibers on other fibers, such as e.g. the one to be connected Fibers accompanied by a merger. The fiber fleece that after the heat treatment the liquid application and the calendering processing described above have been subjected in this order has a suitable one surface condition on, while a desired one high fiber density on the surface the high-density layer is maintained, the pore size in the defined area lies. Furthermore, such a nonwoven fabric is in Essentially free from a decrease in the total pore area on the entire surface of the fiber fleece. Accordingly, presents such a fiber fleece a big one Retention volume for captured dusts and carbon particles ready. The application of liquid fixes and / or forms a plurality of micro air passages (air channels) in the nonwoven fabric, resulting in a high cleaning efficiency for dusts and Carbon particles for a long time is maintained.

The in the application of the liquid used liquid is not specifically limited. An oil agent, such as. Water and an electrostatic inhibitor are preferred. In in the case of using an oil agent it prefers the oil agent in the form of a solution to use. The concentration of the oil solution is preferably in the Range of 0.05 to 10 mass% and more preferably in the range of 0.1 to 5% by mass.

The liquid can be in any desired Be applied, such. by coating or spraying or Spraying, as long as the liquid the surface the high-density layer of the non-woven fabric can contact. spray Spraying is preferred to uniformly apply the liquid to the Surface of the Apply layer with high density.

The amount of liquid for application can be optimally adjusted according to the temperature of the heating roller in the calendering processing. The amount for applying the liquid when the temperature of the heat roller is set in the range mentioned below is preferably 1 to 20 g / m ^2, and more preferably 2 to 10 g / m ² . The application of the liquid above the upper limit of the allowable range can not provide a sufficient effect due to the application of the liquid. When the liquid is applied below the lower limit of the allowable range, the temperature of the heat roller must be set high to ensure the above effect. However, raising the temperature of the heating roller contacted with the surface of the high-density layer may cause fusion and re-bonding of the fibers constituting the high-density layer of the nonwoven fabric, even if when the liquid is applied to the high-density layer as mentioned above. This is not preferable because the heat transfer from the heat roller can clog the pores of the high density layer.

The Temperature of the heating roller is not particularly limited. Preferably is the temperature of the heating roller, which coincides with the surface of the High density layer is in contact with the melt start temperature of the adherent fiber identical or higher as these and lower than the melt start temperature of the bound Fiber, and is e.g. in the range of 190 to 230 ° C. There are no requirements in terms of the pore size and the surface condition the surface the low density layer. Accordingly, the temperature of the roller, those with the surface the low-density layer is in contact, the ambient temperature be. In other words, there is no need to heat the Roller, with the surface of the Low density layer is in contact.

Of the Distance between the rollers (gap between the rollers) is not specifically limited. The gap may be in accordance with the requirements changed in an optimal way become.

The execution of the above-described steps makes it possible to produce the nonwoven fabric of the present invention for a filter having an average pore size in the range of 30 to 60 μm and a total pore area of 0.011 cm ² / cm ² or more.

The thus produced nonwoven fabric can be used as a filter, that the nonwoven according to the configuration the parts to which the filter is to be applied to a suitable one Shape is cut. It is preferable to use different methods such as. a folding method to apply to the nonwoven fabric. Especially in the case of using the nonwoven fabric as a filter for use in an engine of a vehicle, such as e.g. of a motor vehicle it prefers, in terms of maintaining the cleaning performance the filter and ensuring the cleaning efficiency a folding process perform. The folding can be done according to one carried out known methods become.

Further can be a support frame (Flange portion) of the filter can be formed integrally by that a portion of the filter after the filter is subjected to a folding process is subjected to a compression molding. Because when tying the Fibers of the nonwoven fabric according to the invention no binder is used, it is not likely that in the formation of the support frame As an integrated part, cracks are generated in the filter.

The Integrated formation method is not particularly limited. One example for a method is such that the nonwoven fabric after the folding process is placed on a mold of a pressing machine. Then is the mold on which the nonwoven fabric is arranged in a press contact with a mold counterpart brought in a Temperature has been heated, which is lower than the temperature fusing the adherent fibers of the nonwoven fabric. Then be the four outer sides of the Nonwoven pressed to form a flange. To this Way becomes the carrier frame of the nonwoven fabric after the folding process integrated with the nonwoven fabric shaped.

In other words, the nonwoven fabric of the present invention provides easy forming by fusing the bonded portions of the fibers with heat and re-adhering the fibers in a cooling process following the molding process, thereby providing a reinforced support frame. That in the Japanese Unexamined Patent Publication No. HEI 8-309136 described molding method can be applied as an example of a molding method in this invention. Since a support frame can be integrally molded by the use of a part of a filter formed of the nonwoven fabric, there is no need for the use of additional parts such as a frame made of rubber. Accordingly, the filter of the present invention can be manufactured at a reduced cost.

below Examples of the nonwoven fabric according to the invention are with reference to Table 1. "L-m-p-polyester" in Table 1 means polyester with low melting point.

example 1

in the Example 1 was the combination of fibrous layers known as Layered Part No. 1 in Table 1 shown is used. The composition of the layered arranged Part No. 1 is as follows.

Composition of the layer with high Density:

Fibrous layer containing 170 g / m ² "Metsuke" (average fineness: 1.625 denier) made from
50% by weight of polyester fiber (fineness: 1.25 denier, fiber length: 44 mm, melting point: 260 ° C), and
50% by mass of a composite fiber made of polyester and low melting point polyester (fineness: 2 denier, fiber length: 51 mm, melting point of low melting point polyester: 160 ° C).

Note: "Metsuke" is the weight fiber per unit area.

Composition of the middle class:

Fibrous layer containing 90 g / m ² Metsuke (average fineness: 3.0 denier) made from
50% by weight of polyester fiber (fineness: 2 denier, fiber length: 51 mm, melting point: 260 ° C), and
50% by mass of a composite fiber made of polyester and low melting point polyester (fineness: 4 denier, fiber length: 51 mm, melting point of low melting point polyester: 160 ° C).

Composition of the layer with lower Density:

Fibrous layer containing 60 g / m ² Metsuke (average fineness: 5.0 denier) prepared from
50% by weight of polyester fiber (fineness: 6 denier, fiber length: 51 mm, melting point: 260 ° C), and
50% by mass of a composite fiber made of polyester and low melting point polyester (fineness: 4 denier, fiber length: 51 mm, melting point of low melting point polyester: 160 ° C).

The above-described fibrous layers were placed one above the other in the order of the high density layer, the middle layer and the low density layer, and a needle punching method (needling depth: 11 mm, number of needles: 63 parts / cm ² ) was applied to the stacked layer applied from the side of the high-density layer. After a heat treatment (210 ° C, 47 seconds) by a pin-tenter type heat processing machine, water was sprayed onto the surface of the high-density layer (amount of water: 10 g / m ² ). Then, calendering processing was performed by contacting the high-density layer with a heating roller having a surface temperature of 215 ° C, and the low-density layer with an ambient-temperature roller having a gap between the rollers of 2.5 mm in Contact was brought. After the calendering processing, the stacked layers were air-cooled. In this way, a piece of a nonwoven fabric for a filter was produced.

Example 2

A piece of a nonwoven fabric for a filter was produced in the same manner as in Example 1 except that 10 g / m ^{2 of} an anionic type electrostatic inhibitor (2 mass%) was sprayed on the surface of the high-density layer instead of water.

Example 3

in the Example 3, the combination of fibrous layers was used shown in Table 1 as a layered arranged part number 2 is. The composition of the layered part No. 2 is as follows.

Composition of the layer with high Density:

Fibrous layer containing 170 g / m ² Metsuke (average fineness: 1.78 denier) made from
30% by weight of polyester fiber (fineness: 1.25 denier, fiber length: 44 mm, melting point: 260 ° C), and
70% by mass of a composite fiber made of polyester and low melting point polyester (fineness: 2 denier, fiber length: 51 mm, melting point of low melting point polyester: 160 ° C).

Composition of the middle class:

Fibrous layer containing 90 g / m ² Metsuke (average fineness: 2.6 denier) made from
70% by weight of polyester fiber (fineness: 2 denier, fiber length: 51 mm, melting point: 260 ° C), and
30% by mass of a composite fiber made of polyester and low melting point polyester (fineness: 4 denier, fiber length: 51 mm, melting point of low melting point polyester: 160 ° C).

Composition of the layer with lower Density:

Fibrous layer containing 60 g / m ² Metsuke (average fineness: 3.0 denier) made from
70% by weight of polyester fiber (fineness: 6 denier, fiber length: 51 mm, melting point: 260 ° C), and
30% by mass of a composite fiber made of polyester and low melting point polyester (fineness: 4 denier, fiber length: 51 mm, melting point of low melting point polyester: 160 ° C).

One Piece of one Fiber fleece for a filter was produced in the same manner as in Example 1, however For example, the fibrous layers described above were used.

Example 4

One Piece of one Fiber fleece for a filter was produced in the same manner as in Example 1, however Water was not sprayed on the high density layer.

Example 5

A piece of a nonwoven fabric for a filter having the composition shown by the layered part No. 3 in Table 1 was produced in the same manner as in Example 4 except that 90 g / m ^{2 of} Metsuke was used to form the layer high-density and 170 g / m ² Metsuke used to form the middle layer.

Example 6

A piece of a nonwoven fabric for a filter having the composition shown by the layered member No. 4 in Table 1 was produced in the same manner as in Example 4, but as a high-density layer, a fibrous layer became 170 g / m ² Metsuke (average fineness: 1,738 denier) and having the following composition was used.

Composition of the layer with high Density:

• 25% by weight of polyester fiber (fineness: 1.25 denier, fiber length: 44 mm, melting point: 260 ° C),
• 25% by weight of a composite fiber made of polyester and polyester low melting point (fineness: 2 denier, Fiber length: 44 mm, melting point of the low melting point polyester: 160 ° C), and
• 50% by mass of a composite fiber made of polyester and polyester low melting point (fineness: 1.7 denier, Fiber length: 51 mm, melting point of low melting point polyester: 160 ° C).

It should be noted that the composition described above the high-density layer for reducing the number of contact points between fibers was made.

The Properties of the nonwoven fabrics obtained in Examples 1 to 6 were re of the following features. The gas supplied was through the layer pulled with low density of each fiber fleece and out of the layer discharged with high density of the fiber fleece. The results of Studies are shown in Table 2.

Characteristics to be examined

• - Average Pore size (unit: μm): Calculated with a Coulter Porometer II (a product of Coulter, Inc.) in a state where the inlet side of the supplied gas every fiber fleece, viz the surface the low-density layer was arranged at the top, and according to one Bubble point method defined in ASTMF-361-80.
• Total pore area (unit: cm ² / cm ² ): Calculated with a Coulter Porometer II (a product of Coulter, Inc.) in a state where the inlet side of the supplied gas of each nonwoven fabric, namely, the surface of the low-density layer was above, and according to a bubble point method defined in ASTMF-361-80, wherein the total pore area was calculated by integrating the areas of the pores of the same diameter with respect to each pore size (diameter) and summing up the integration results ,
• - Metsuke (unit: g / m ² ): measured according to JIS 11906 4.2.
• - thickness (Unit: mm): Measured according to JIS 11906 4.2 in a condition where a load of 2 kPa on each piece of non-woven fabric exercised has been.
• - Cleaning efficiency (initial Capture rate and end capture rate): Calculated according to JIS D1612 at a test wind speed of 60 m / s and in a state where a powder, designated as No. 8 defined in JIS Z8901, applied to each piece of the nonwoven fabric has been.
• - ΔP (unit: Pa): Measured according to JIS D 1612
• - Dust retention volume (g / 0.1 m ³ ): Measured according to JIS D 1612
• - Carbon retention volume (g / 0.1 m ³ ): Measured according to JIS D 1612
• - moldability: Moldability in molding a frame by hot pressing the outer peripheral portion of the folded nonwoven fabric

Table 2 unit Example 1 Ex. 2 Example 3 Example 4 Example 5 Example 6 Average pore size microns 44.7 48.2 43.6 48.7 47.8 56.3 Total pore area cm ² / cm ² 0.0184 0.0132 0.0132 0.0097 0.0099 0.0107 Metsuke g / m ² 322 312 302 327 313 370 thickness mm 5.5 5.5 4.4 5.5 4.6 4.3 .DELTA.P Pa 112 118 125 127 117 131 Initial capture rate % 97.9 97.7 97.4 97.2 96.0 98 Endeinfangrate % 99.7 99.6 99.4 99.7 99.5 99.6 Dust retention volume g / 0.1 m ³ 242 241.4 235 225 164 152 Carbon retention volume g / 0.1 m ³ 3.77 3.7 3.6 2.9 2.8 2.0 malleability Good Good Good Good sufficient sufficient

The The following is an analysis of the test results

in the Example 1 was water on the surface of the calendering before the calendering Applied layer of high density of the nonwoven fabric. The application from water vapor could clogging the pores and deforming the pores, e.g. forming reduced dimensions of the pores, suppress. As a result, a sufficiently large total pore area of the Nonwoven fabric could be ensured and a suitable pore size could to be obtained. In contrast, in Example 4, in which Water has not been applied before calendering, some of the pores are clogged after calendering, and the pores, which were not blocked, had become bigger, with the result, that the total pore area was reduced. In a comparison of game 1 with the example 4 was Example 1 with respect to the pressure loss, the initial Trapping rate of dusts and carbon particles, as well as the dust retention volume and the carbon retention volume consider Example 4.

In Example 2, before the calendering processing, a solution containing an oil agent was applied to the surface of the high density layer instead of water. The average pore size of the Nonwoven fabric in Example 2 is generally identical to that in Example 4. However, the nonwoven fabric in Example 2 showed less clogging and less deformation of pores, such as reduced pore size, after the calendering processing as compared with Example 4 because the oil solution was used in Example 2. The nonwoven fabric in Example 2 could also achieve a large total pore area, with the result that the nonwoven fabric in Example 2 could provide a lower pressure loss, a high initial trapping rate, and a large dust and carbon particle retention volume.

in the Example 3 was the content of the low melting point component the adherent fibers forming the high-density layer, elevated. As a result, the average pore size was relatively small and the pore size was due of hot pressing relatively small in calendering processing. However, because the calender processing was carried out in Example 3 after the application of water, Clogging of the pores was suppressed and the same level the total pore area as in example 2 could be ensured. In a comparison of Example 3 and Example 4, Example 3 provided a larger dust and Kohlenstoffteilchenrückhaltevolumen as example 4 ready.

in the Example 5 was the content of fibers containing the layer with high Dense, diminished. As a result, the total pore area did not reach the defined area and the dust and carbon particle retention volume was small, although the average pore size was relatively large.

in the Example 6 was an attempt to determine the average pore size in the defined area and ensure a large total pore area, by adjusting the adhesion or bond between the Fibers that form the high-density layer. The example However, 6 could not reach a sufficiently large total pore area, because a water / oil solution is not was applied before calendering. The fiber fleece in Example 6, no sufficiently large dust retention volume and carbon retention volume could be achieved provide.

As can be seen from the examples, the nonwoven fabrics prepared by disposing at least two fibrous layers one above the other meet the requirements of the average pore size of 30 to 60 μm and the total pore area of 0.011 cm ² / cm ² or more Provide satisfactory cleaning performance required for filters.

When The result of the investigation of the formability of the fiber webs was obtained that the nonwoven fabrics in Examples 1 to 4, the formability requirement fulfilled. However, the nonwoven fabrics in Examples 5 and 6 were poor, because unevenly folded portions at an end portion or a Eckenendabschnitt of the fiber fleece templates.

In summary, in accordance with one aspect of this invention, a nonwoven fabric for a filter is constructed of two or more different types of fibrous layers arranged one above the other and has an average pore size of 30 to 60 microns inclusive and a total pore area of 0.011 cm ² / cm ² or more with respect to the entire surface of the nonwoven fabric. The average pore size is calculated according to the bubble point method as defined in ASTM F-316-80 using a Coulter Porometer II.

each fibrous layer is made of adherent fibers and to be bonded together Built up fibers.

According to one Another aspect of this invention is the fibrous layers one over the other arranged such that the fiber density of the layer gradually or continuously increases and the average Denier value of fibers forming the fibrous layer, step by step or decreases continuously.

The fibrous layers are made by physically connecting one over the other arranged differently. The physical connection is preferably by interlacing the fibers making up the fibrous layers form, received. The physical connection is preferably one Needling method or a water jet processing method.

Although the method for producing the nonwoven fabric of the present invention is not particularly limited, the following method is preferable. In particular, the method comprises arranging two or more different types of fibrous layers one above the other, wherein the fibrous layer is composed of fibers mixed in a certain ratio, subjecting the fibrous layers to physical bonding by interlacing the fibers, Subject the fibrous Schich a heat treatment while a part of the fibers fuses for bonding to build a multi-layer part of a certain shape, applying a liquid to a surface of the multi-layer part having a greater fiber density than the opposite surface of the multi-layer part, and performing calendering processing with the multi-layered one Part by processing the part through a gap between a pair of rollers, in particular by allowing the one surface of the multi-layer part in contact with the roller (first roller), which is heated to a certain temperature, while allowing the opposite surface thereof will come into contact with a mating roll (second roll) at ambient temperature. That is, the multi-layer part is processed by the rollers in the state where the temperature of the first roller is higher than the temperature of the second roller.

It should be noted, all the nonwoven fabrics according to the invention, the above have been described as a filter for air-intake engines of motor vehicles are suitable.

There This invention can be embodied in many forms without being to deviate from the essential characteristics of the invention is the present embodiment therefore illustrative and not restrictive, since the scope of protection of the invention by the attached claims and is not determined by the foregoing description.

Claims (14)

A nonwoven fabric for a filter having excellent detergency and trapped material retention volume constructed by two or more different types of fibrous layers, one above the other, the nonwoven fabric having an average pore size of from 30 μm to 60 μm inclusive has a total pore area at 0.011 cm ² / cm ² or more with respect to the entire surface of the nonwoven fabric, the average pore size being calculated by the bubble point method as in ASTM F-316-80 using a Coulter Porometer II, each fibrous layer of adhesive fibers and fibers to be bonded is constructed and the adhesive fibers and the fibers to be bonded to each other are bonded together by a heat treatment. Fiber fleece for A filter according to claim 1, wherein the fibrous layers are above the Others are arranged in such a way that a fiber density the layer stepwise or continuously in a thickness direction of the nonwoven fabric from a surface of the nonwoven fabric the one fed Gas is drawn in, and to the opposite surface thereof, through the one fed Gas is pulled out, increases. Fiber fleece for A filter according to claim 1 or 2, wherein the fibrous layers one over the others are arranged in such a way that an average Denier the fibers that build up the fibrous layer, gradually or continuously in a thickness direction of the nonwoven fabric of a surface the fibrous web through which a supplied gas is drawn in, and to the opposite surface of it, by which the supplied Gas is pulled out, decreases. Fiber fleece for A filter according to any one of claims 1 to 3, wherein the fibrous ones Layers one over the others are arranged by physical connection. Fiber fleece for a filter according to any one of claims 1 to 4, wherein the physical Bonding by interlacing the fibers which are the fibrous ones Build layers, is preserved. Fiber fleece for A filter according to claim 5, wherein said physically connecting by a needle punching method or a water jet processing method is obtained. Filter for an engine of an automobile made of a non-woven fabric according to one of the claims 1 to 6. A process for producing a nonwoven fabric according to claim 1, comprising the steps of: arranging two or more different kinds of fibrous layers one above the other, the fibrous layer being composed of fibers mixed in a certain ratio, subjecting the fibrous layers to one physical bonding by interweaving the fibers, subjecting the fibrous layers to heat treatment while a part of the fibers fuse to bond to form a multi-layer part of a certain shape, wherein applying a liquid to a surface of the multi-layer part wherein the surface has a larger fiber density than the opposite surface of the multi-layer part is preferable, and performing a calendering processing step to the multi-layer part by allowing the one surface of the multi-layer part in contact with a first roller; heated to a certain temperature, while the opposite surface thereof is allowed to come into contact with a second counter roll at ambient temperature, the temperature of the first roll being higher than the temperature of the second roll. A method for producing a nonwoven fabric according to Claim 8, wherein each fibrous layer of adhesive fibers and connected to each other fibers is constructed. A method for producing a nonwoven fabric according to Claim 8 or 9, wherein the fibrous layers over the Others are arranged in such a way that a fiber density the layer stepwise or continuously in a thickness direction of the nonwoven fabric from a surface of the nonwoven fabric to the opposite surface of it increases. A method for producing a nonwoven fabric according to one of the claims 8 to 10, wherein the fibrous layers one above the other in such a Manner are arranged such that an average denier of the fibers constituting the fibrous layer, stepwise or continuously in a thickness direction of the nonwoven fabric of a surface of the fibrous web to the opposite surface it decreases. A method for producing a nonwoven fabric according to one of the claims 8 to 11, wherein the physical bonding by a needling process or a water jet processing method is obtained. A method for producing a nonwoven fabric according to one of the claims 8 to 12, wherein the temperature of the first roller in a range from 190 ° C up to 230 ° C lies. A method for producing a nonwoven fabric according to one of the claims 8 to 13, wherein the liquid is water or an oil agent is.