MXPA99008604A

MXPA99008604A - Air filter

Info

Publication number: MXPA99008604A
Application number: MXPA/A/1999/008604A
Authority: MX
Inventors: Hollingsworth Anthony; Staudenmayer Oliver; Berkemann Ralph
Original assignee: Carl Freudenberg Kg
Priority date: 1998-09-21
Filing date: 1999-09-20
Publication date: 2000-10-01

Abstract

Fibers are intertwined by liquid-jetting from the clean-air side (8) before bonding. Compression caused, increases from the dirty-air side (7). Regions of differing density (A, B, C) are formed, where particles of differing sizes are separated, during use. Preferred Features:Fiber titer is 0.05-50 dtex. Fibers (6) are coarse and fine, the titers differing by a factor of 6 or more. The fine fibers comprise split fibers, produced by liquid-jetting. Median density of the fleece increases progressively in the flow direction (R). Of layers forming the construction, one or more is prefabricated;another is a pile applied to it and bonded by liquid-jetting. The pile is on the clean air side and includes split fibers. The side facing the dirty air has the greater proportion of coarse fibers. The fibers are electrostatically-charged. Fiber cohesion is a result of welding or adhesion using a binder. The filter material is liquid-jetted over its entire cross section. The finished material is pleated.

Description

AIR FILTER Description of the Invention Technical Field The invention relates to an air filter comprising a deep filtration material containing a nonwoven material having one side of virgin air and one side of purified air, the material being not Fabric is formed by adhesive bonded fibers and / or cohesively. STATE OF THE ART An air filter of this type is known from DE 44 27 817 Cl. In filters with a deep filtration material the particles to be separated are collected primarily in the filter material. The opposite of this happens with surface filters, in which the particles accumulate primarily on the surface of the filter material as filter cake. DE 41 25 250 A1 discloses a material for air filters consisting of a two-layer laminate of non-woven material. The layer facing the side of the purified air is reinforced by a water jet and has fibers of an average fineness of less than 2.2 dtex. The layer of nonwoven material facing the virgin air side has larger fibers compared to that. Both layers are linked to one another by mechanical interlacing. It is true that such a filtration medium has an improved effectiveness compared to a purely mechanical non-woven material. However, it is a drawback that when the needles are laminated by needling, they also form holes in the layer of the purified air, which negatively affect the efficiency of the filter in relation to the small particles. Non-woven materials have proven their effectiveness as filtering material for air filters and guarantee excellent filtration characteristics. However, the known filter materials do not satisfy all the wishes with regard to the stability and rigidity of the filter material. This is on the one hand symptomatic in the manufacture of air filters to manufacture a pleated or folded filter with a correspondingly large filtering surface. But also the stiffness is of great importance for the function of the air filter to prevent excessive deformation of the filter material during operation. A deformation would cause the filter material to come into intimate contact, which would result in a very high pressure differential and a short life of the air filter. Embodiment of the invention The object of the invention is to provide an air filter with a particularly rigid filtering material. This task is solved in a filter of the type under consideration by the fact that the fibers present bonds that are produced by means of a jet of liquid from the side of the purified air previously to the adhesive and / or cohesive bonding, and by the fact that by means of the Fluid jet fibers are increasingly appearing azan from the virgin air side to the purified air side, so that different caking areas are formed in which particles of various sizes can be collected. The liquid jet can consist in particular of a high pressure water jet treatment, which is known in the manufacture of non-woven materials. By highly concentrated high-pressure water jets that penetrate through the non-woven material and collide with a liquid-permeable substrate, the fibers swirl. As a result, the fibers picked up by the liquid jets adopt an interlaced arrangement. In this, according to the invention, the energy of the jet which is determined by the mass of liquid per unit of time and by the pressure of the liquid is calculated so that the fibers are increasingly flaccid from the side of the virgin air towards the side of the liquid. purified air. As a result, caked areas are produced in which you can collect particles of variable size. The liquid jet treatment from the virgin air side which is carried out in combination with the adhesive and / or cohesive bonding of the fibers provides a nonwoven material which has a surprisingly high stiffness and which simultaneously has excellent filtering properties. This is surprising because the high-pressure liquid jet is applied in the manufacture of non-woven materials to produce soft non-woven materials, textiles to the touch. Another advantage is that the thicknesses of 5 mm and less of the filter material that are achieved by the liquid jet treatment are suitable for an air filter and may make an additional calendering process unnecessary. In addition, manufacturing costs can be reduced by virtue of the fact that different areas of appeal can also be produced in a single stage of work in the case of a single layer nonwoven material. Conveniently it is envisaged that the fibers present bonds that are produced by liquid jet from the virgin air side prior to adhesive and / or cohesive ligation. By means of the additional liquid jet from the virgin air side, which is preferably applied with a jet energy different from that of the liquid jet from the purified air side, a particularly firm deep filtering material can be obtained. According to a favorable improvement it is foreseen that the fibers have a dtex number of 0.05 to 50. Another improvement of the filtering properties is achieved by proceeding so that the fibers contain coarse fibers and fine fibers, the number of coarse fibers being it is above the number of fine fibers by at least a factor of 6. Thus, the air filter can have for example fine fibers with a dtex number of about 1 and thick fibers with a dtex number of about 6 or greater. Particularly small particles can be collected in the air filter if the fine fibers are constituted at least partially by dissociated split synthetic fibers. The split synthetic fibers are fibers of several relatively coarse components in dtex numbers of usual cardable fibers, which are easily processed. By means of the dissociation of the split synthetic fibers, comparatively fine fibers are produced. In this way it is also possible to produce surface structures with microfiber structure with conventional processes. The manufacture of the air filter is simplified in particular by the fact that the split synthetic fibers are dissociated by the liquid jet treatment. A particularly good dust storage capacity is achieved in the filter material if the density of the medium of the non-woven material progressively increases in the direction of the flow circulation. Consequently, the air filter has a lower fiber density and large filtration pores on the virgin air side. In this area, the larger particles that must be segregated are intercepted. Making the side of the purified air the air filter progressively increases the density of the fibers; there are correspondingly smaller pores formed by the fibers. The smallest particles to be segregated penetrate first through the area with the lowest density of fibers found on the virgin air side and are subsequently collected in the area with the highest density of fibers. By means of this it is achieved that the air filter can be charged with particles to be segregated through the entire thickness of the filter material. As a result, it is possible to achieve high filter life intervals and a lower constant pressure loss over the entire life of the filter. According to a further development of the invention, it is provided that the non-woven material has at least one first layer of fibers facing the virgin air side and a second layer of fibers facing the side of the purified air. Manufacturing is particularly simplified if at least one of the fiber layers is substantially constituted by a fiber layer compacted in advance, and if at least one of the fiber layers is substantially formed by a fiber web applied to the layer of material. non-woven, wherein the fiber web and the non-woven layer are joined to one another by the liquid jet. Particularly good filtering properties are obtained if the fiber layer formed by the fiber web is arranged on the purified air side of the layer of non-woven material. Particularly small particles can be segregated in the filter if the fiber layer formed by the fiber web contains the unfolded synthetic fiber. In a further development of the invention, it is provided that the fiber layer facing the virgin air side contains a greater proportion of coarse fibers than the fiber layer facing the side of the purified air. Larger pores are formed there by the greater proportion of coarse fibers in the fiber layer oriented towards the virgin air side. In this case it can also be envisaged that the coarse fibers are only contained in the fiber layer facing the virgin air side. Another improvement of the filtering properties is achieved by the electrostatic charging of the fibers. This can be carried out in particular by means of an electret treatment, such as for example a corona treatment. The cohesive bonding of the fibers can be carried out particularly conveniently by melting a part of the fibers. The adhesive bond can be carried out in a particularly simple manner by gluing the fibers with a binder. Preferably, bicomponent adhesive fibers are used. In particular, the manufacturing costs of the air filter are reduced by proceeding in such a way that the filtering material is subjected to a jet of liquid through its entire cross section.

A particularly large filtering surface is obtained by pleating the deep filtration material. Brief description of the drawings. The object of the invention is illustrated below further on the basis of the drawings. They show: Figure 1 an air filter according to the invention, Figure 2 a schematic representation of a cross section through the filter material according to a first embodiment, Figure 3 a schematic representation of a cross section through Through the filtering material according to a second embodiment, Figure 4 is a cross-section through a split synthetic fiber. Embodiment of the invention Figure 1 shows an air filter 1 according to the invention, which is configured as a filter chassis. It presents a filtering material 2 which is pleated parallel to a lateral edge. The filtering material 2 is crimped around by a sealing strip 3.

The filtering material 2 is constituted by the non-woven material 5 shown in FIG. 2. It is formed by synthetic fibers 6 with a dtex number of 0.05 to 50 and can be manufactured (for example, carding) with the aid of carding machines. The fibers 6 are bonded to the nonwoven material by means of a jet of high-pressure water. The non-woven material 5 has seen in the direction R of flow circulation areas A, B, C with different characteristics, which allow to segregate particles of different sizes in the different areas A, B, C. The different characteristics of the areas A , B, C are achieved in the case of the embodiment shown in FIG. 2 by the fact that the density of the fibers increases progressively in the direction R of the flow flow from the side 7 of the virgin air to the side 8. of purified air. The increase in fiber density is obtained by subjecting the non-woven material 5 to a water jet treatment from the side 8 of the purified air. By means of a unilateral water jet treatment of this kind, the fibers 6 of the non-woven material 5 are more strongly caked by the side 8 of the purified air than by the side 7 of the virgin or inflowing air, far from the water jet. . Consequently, the density of the fibers is lower in the area A oriented towards the side 7 of virgin air than in the central region B, and in this again lower than in the area C oriented towards the side 8 of purified air. Correspondingly, the size of the intermediate spaces or pores of the non-woven material 5 delimited by the fibers 6 from the area A to the area C increases. Consequently, during the operation larger particles can be collected in the area A of the air filter, particles smaller in area B and finer particles in area C. The fibers 6 of the non-woven material 5 are adhesively bonded and / or cohesively after the liquid jet treatment. A cohesive bonding can be carried out by welding, the fibers 6 being temporarily softened at an elevated temperature and the adjacent fibers 6 being joined at their points of contact, possibly under pressure. An adhesive bond can be carried out by gluing the fibers 6 with a binder. This can be added to the mixture in the form of the so-called binder fibers already prior to the manufacture of the non-woven material. The agglutination is then carried out, for example, by a heat treatment, in which the binder fiber sheath softens and binds the adjacent fibers 6 together with one another. An adhesive bond can also be carried out by applying a liquid polymeric binder, which is hardened by a subsequent heat treatment. Figure 3 shows yet another embodiment example of the nonwoven material 5. The fibers 6 have 6 'thick fibers and fine 6"fibers, the number of the thick fibers being greater by the factor 6 than that of the fine fibers. The areas A 'B 'of the non-woven material 5 with different characteristics in the direction R of flow circulation are obtained by providing at least two layers of fibers with different fiber compositions. The fiber layer oriented towards the side 7 of virgin air which is disposed in the area A 'has a greater proportion of fibers 6' thicker than the layer of fibers oriented towards the side 8 of purified air, which is arranged in the area B '. The ratio by weight of the fine fibers with respect to the coarse fibers in the non-woven material 5 is for this from 5 to 95 to 40 to 60. By means of the liquid jet, the fibers 6 ', 6"are bonded, which connect the layers of fibers. To improve particle segregation, the fibers can be charged electrostatically. This can be done by means of an electret treatment, in particular by means of a corona treatment.

The fine fibers 6"may consist at least partially of unfolded synthetic fibers. A schematic tansversal section through a split synthetic fiber 9 of this kind is shown in FIG. 4. The split synthetic fiber 9 shown has a first component 10 formed by a first polymer and a second component 11 formed by a second polymer. In the case of the embodiment shown in FIG. 4, eight segments are formed with the component 10, wherein the component 11 is arranged in the form of a layer between the segments. By dividing or disassociating the split synthetic fiber 9, the eight components 10 each form one of the fibers 6 or 6"shown in FIGS. 2 and 3. The number dtex of the fine fibers 6" produced by the dissociation of the fibers. the split synthetic fibers 9 can arrive as low as 0.05. Conversely, the split synthetic fiber 9 is clearly thicker and therefore can be easily processed by intermixing it with the non-woven material. The dissociation of the split synthetic fiber 9 is produced by the pressure that the water jet treatment exerts on the split synthetic fiber 9.

The advantages of the air filter according to the invention and its method of manufacture are described below on the basis of exemplary embodiments. Example 1 The nonwoven material of Example 1 has a mass weight of 300 g / m2, and a thickness (measured according to DIN 53855) of 3 mm. It is produced from carded cut fiber. The composition of the fiber comprises 40% of 0.9 dtex, 10% of 6.7 dtex of polyester fiber and 50% of 2.2 dtex of bicomponent polyester fiber. The fiber links are produced by unilateral water jet with a water pressure between 50 and 100 bar. The non-woven material is then dried in a heat-diffusion furnace and ligated by activating the binder fiber. This non-woven material has a stiffness of 120 N «m2 in the longitudinal direction (measured at 20 ° of bending angle according to DIN 53350). This is about three times more than in the case of a nonwoven material with identical fiber, weight and thickness composition, which however was manufactured without the liquid jet treatment. Example 2 The non-woven material of Example 2 has a mass weight of 170 g / m2, and a thickness (measured according to DIN 53855) of 0.9 mm. This nonwoven material is produced from two webs of carded cut fiber. The fiber composition of the first web, which represents 17% of the total weight, comprises 50% of a split synthetic polyolefin fiber with dtex of 2.2 (undissociated) and 50% of a polypropylene fiber with dtex of 6.7. The composition of the fiber of the second web comprises 100% of a bicomponent polyolefin fiber of dtex 36. Bonding of the webs by binding the fibers contained therein is produced by water jet with a water pressure of between 50 and 150. bar, and then after this it is dried in a thermodifusion oven and is joined by activation of the binder fiber. The structure of the non-woven material resulting from this presents a continuous decrease of the fine fibers from the side of the fine fibers to the side of the coarse fibers. The structure of the non-woven material has a resistance to bending, in the direction of manufacture, of 38.0 N-m2 (measured at 20 ° of flexion angle according to DIN 53350). This is three times higher than that of comparative filtering material, which is composed of three layers produced in different stages of processing, which were produced without a liquid jet in the calendering process, with equal weight and equal thickness. A subsequent electrostatic charge of the structure of the non-woven material produces a filtering capacity exceeding by 78% in the air permeability (according to DIN 53887) that of a three-layer comparative filter medium, also electrostatically treated, in the case of a capacity identical segregation of fines (according to EN 143) and identical dust collection capacity.

Claims

CLAIMS Air filter comprising a deep filtration material containing a non-woven material having one side of virgin air and one side of purified air, the nonwoven being formed by adhesive and / or cohesively bonded fibers, characterized by the fact that the fibers present bonds that are produced by means of a jet of liquid from the side of the purified air previously to the adhesive and / or cohesive bonding, and by the fact that by means of the liquid jet the fibers are increasingly clogged from the virgin air side to the purified air side, so that different caking areas are formed in which particles of various sizes can be collected.
Air filter according to claim 1, characterized in that the fibers present bonds that are produced from the virgin air side by liquid jet prior to adhesive and / or cohesive ligation.
Air filter according to claim 1 or 2, characterized in that the fibers have a number of 0.05 to 50.
Air filter according to one of claims 1 to 3, characterized in that the fibers contain coarse fibers and fine fibers, the number of coarse fibers being greater by at least a factor of 6 than the number of coarse fibers. the fine fibers.
Air filter according to claim 4, characterized in that the fine fibers are constituted at least partially by dissociated split synthetic fibers.
Air filter according to claim 5, characterized in that the split synthetic fibers are dissociated by the liquid jet treatment.
Air filter according to one of claims 1 to 6, characterized in that the density of the medium of the non-woven material progressively increases in the direction of flow circulation.
Air filter according to one of claims 1 to 7, characterized in that the non-woven material has at least one first layer of fibers facing the virgin air side and a second fiber layer oriented towards the side of the purified air.
Air filter according to claim 8, characterized in that at least one of the layers of fiber is constituted substantially by a layer of non-woven material compacted beforehand, and that at least one of the layers of The fiber is substantially formed by a fiber web applied to the layer of non-woven material, the fiber web and the non-woven layer being joined to one another by the liquid jet.
Air filter according to claim 9, characterized in that the fiber layer formed by the fiber web is arranged on the purified air side of the layer of non-woven material.
Air filter according to claim 9 or 10, characterized in that the fiber layer formed by the fiber web contains the unfolded synthetic fiber.
Air filter according to one of claims 7 to 11, characterized in that the first layer of fiber oriented to the virgin air side contains a greater proportion of coarse fibers than the second layer of fiber oriented to the side of the purified air.
13. Air filter according to one of claims 1 to 12, characterized in that the fibers are electrostatically charged.
Air filter according to one of claims 1 to 13, characterized in that a cohesive bonding is carried out by welding the fibers.
15. Air filter according to one of claims 1 to 14, characterized in that the adhesive bond is carried out by bonding the fibers with a binder.
16. Air filter according to one of claims 1 to 15, characterized in that the filtering material is subjected to a jet of liquid over its entire cross section.
17. Air filter according to one of claims 1 to 16, characterized in that the deep filtering material is pleated.