Spun-bonded fabric material, object comprising a spun-bonded fabric material, filter medium, filter element, and use thereof

Abstract

A filter medium (10) for filtering a fluid, in particular for use in an interior air filter (32), comprises a spun-bonded nonwoven formed at least in part of multi-component segmented pie fibers (1) having at least a first plastic component (2) and a second plastic component (3). The multi-component fibers (1) are largely non-split and in order to manufacture same, segmented pie filaments are spun in a spun-bonding process (S4) to form a spun-bonded nonwoven (10). The segmented pie filaments then form the multi-component fibers (4), the first plastic component (2) and/or the second plastic component (3) being made in particular of a polypropylene.

Claims

1. A spun-bonded nonwoven which is formed at least partially from multi-component segmented fibers formed of segmented pie fibers (1), the multi-component segmented fibers comprising: at least a first plastic component (2) forming one or more first pie segments, and a second plastic component (3) forming one or more second pie segments, wherein the multi-component segmented fibers have a circular cross-section; wherein the first and second pie segments have a pie-shaped cross-section, wherein the multi-component segmented fibers have an outer sheath surface (7), wherein at least a portion of the first and the second pie segments of the multi-component segmented fibers are joined together at inner segment boundaries (4) of the pie segments, wherein the outer sheath surface (7) has one or more longitudinal grooves (6′) formed along one or more of the inner segment boundaries (6) where adjacent pie segments abut side by side and are joined together, wherein the pie segments of at least 50% of the multi-component segmented fibers are joined together side by side over at least 70% of a respective fiber length of each multi-component segmented fiber, such that the joined pie segments are split apart over no more than 30% the respective fiber length of any individual multi-component segmented fiber, wherein the spun-bonded nonwoven is thermally solidified such that the multi-component segmented fibers are interconnected to form the spun-bonded nonwoven, wherein the first plastic component (2) and the second plastic component (3) consist of a polypropylene.

2. The spun-bonded nonwoven of claim 1, wherein at least 70% of the of multi-component segmented fibers (1) have adjoining pie segments (2,3) joined together at inner segment boundaries (4) over at least 70% of the respective fiber length of the multi-component segmented fibers (1).

3. The spun-bonded nonwoven according to claim 1, wherein the outer sheath surface (7) along a circumference (5) of the sheath surface has an average roughness depth (R.sub.Z) of less than 2 μm.

4. The spun-bonded nonwoven according to claim 1, wherein the multi-component segmented fibers (1) have an average diameter (D) of at least 10 μm.

5. The spun-bonded nonwoven according to claim 1, wherein the multi-component segmented fibers (1) have at least four pie segments (2, 3).

6. The spun-bonded nonwoven according to claim 1, wherein the pie segments (2, 3) of the multi-component segmented fibers (1) do not split apart under the influence of a waterjet treatment.

7. The spun-bonded nonwoven according to claim 1, wherein the spun-bonded nonwoven (1) has a machine direction (M), and the multi-component segmented fibers (1) are oriented along the machine direction (M).

8. The spun-bonded nonwoven according to claim 1, wherein the multi-component segmented fibers (1) are thermally interconnected together exclusively by hot-air bonding to form the spun-bonded nonwoven.

9. The spun-bonded nonwoven according to claim 1, wherein the spun-bonded nonwoven (10) has a thickness (D) between 1.0 mm and 2.0 mm.

10. The spun-bonded nonwoven according to claim 8, wherein the multi-component segmented fibers (1) are thermally interconnected to form a nonwoven material.

11. The spun-bonded nonwoven according to claim 1, wherein the spun-bonded nonwoven (10) has a thickness between 0.5 mm and 1.5 mm.

12. The spun-bonded nonwoven according to claim 1, wherein the plastic components (2, 3) of the multi-component segmented fibers (1) are charged as electrets.

13. The spun-bonded nonwoven according to claim 1, wherein the spun-bonded nonwoven (10) has a grammage of between 80 g/m2 and 160 g/m2.

14. The spun-bonded nonwoven according to claim 1, wherein the first plastic component (2) has a first melting point (T2) and the second plastic component (3) has a second melting point (T3), wherein the first melting point (T2) is higher than the second melting point (T3) and there is a difference between the first and the second melting point (T2, T3) of at least 8 degrees K.

15. The spun-bonded nonwoven according to claim 14, wherein a mass fraction of the first plastic component is between 20% and 80%.

16. The spun-bonded nonwoven according to claim 1, wherein the first plastic component (2) and/or the second plastic component (3) has a first portion of a first thermoplastic material (MA) having a first melting point (TA) and a second portion of a second thermoplastic material (MB) having a second melting point (TB), wherein the first melting point (TA) is higher than the second melting point (TB).

17. The spun-bonded nonwoven of claim 16, wherein the second thermoplastic material (MB) of adjacent multi-component fibers (1) are partially fused together to solidify the spun-bonded nonwoven (10).

18. The spun-bonded nonwoven according to claim 16, wherein the first thermoplastic material (MA) is a polypropylene homopolymer and/or the second thermoplastic material (MB) is a metallocene polypropylene.

19. The spun-bonded nonwoven according to claim 15, wherein the mass fraction of the first thermoplastic material (MA) is between 40% and 60%.

20. The spun-bonded nonwoven according to any of claim 18, wherein the first thermoplastic material (MA) and/or the second thermoplastic material (MB) have a melt flow index (MFI) between 20 g/10 min and 30 g/10 min.

21. The spun-bonded nonwoven according to claim 20, wherein the spun-bonded nonwoven (10) is thermally solidified in a respective area of 10 cm.sup.2 in such a way that it is self-supporting.

22. The spun-bonded nonwoven according to claim 1, wherein the spun-bonded nonwoven (10) has an air permeability of between 1,300 l/m.sup.2 s and 1,700 l/m.sup.2 s.

23. The spun-bonded nonwoven according to claim 1, wherein the spun-bonded nonwoven (10) has a NaCl retention capacity at 0.3 μm of greater than 20%.

24. The spun-bonded nonwoven according to claim 1, wherein the spun-bonded nonwoven (10) has a dust storage capacity at 50 Pa of more than 20 g/m.sup.2.

25. The spun-bonded nonwoven according to claim 7, wherein the spun-bonded nonwoven (10) has a flexural rigidity in the machine direction (M) of more than 170 mN.

26. The spun-bonded nonwoven according to claim 18, wherein the spun-bonded nonwoven (10) comprises pleats (21) with a plurality of pleat sections (23) arranged between pleat edges (22).

27. The spun-bonded nonwoven of claim 26, wherein the pleats (21) extend transversely to a machine direction (M).

28. An insulating material for a building insulation, motor vehicles, household appliances, beverage packaging and/or a packing material comprising a spun-bonded nonwoven according to claim 1.

29. A filter medium comprising the spun-bonded nonwoven of claim 1.

30. The filter medium of claim 29, wherein the filter medium (11) further comprises a melt-blown material (9).

31. A filter element comprising a spun-bonded nonwoven according to claim 29.

32. The filter element according to claim 31, wherein the filter element comprises an adsorbent layer.

33. The filter element according to claim 32, wherein the filter element is treated with flame resistant additives or flame retardants.

34. The filter element (32) according to claim 33, wherein the filter medium is pleated in a zigzag to form a pleat pack (20).

35. The filter element (32) according to claim 34, comprising sidebands (26, 27) attached to opposite pleat profiles of the pleat pack (20) and headbands (28, 29) attached to opposite end pleats (30, 31) of the pleat pack (20).

36. The filter element according to claim 35, wherein the filter element (32) is an interior air filter element for a motor vehicle (14).

37. The filter element according to claim 35, wherein outer boundary surfaces (A1, A2, A3) of the pleat pack (20) include a cuboidal volume and at least two opposing boundary surfaces each have an area between 0.05 and 0.066 m2.

38. The filter element according to claim 35, wherein the filter medium (10) has a filtration area between 0.458 and 0.472 m.sup.2.

39. The filter element according to claim 35, wherein the pleat pack (20) in the machine direction (M) has a length of between 285 and 300 mm and between 38 and 46 pleats (21), the pleat heights (H) being between 25 and 31 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The figures are as follows:

(2) FIG. 1: shows a schematic view of an exemplary embodiment of a filter medium made of a spun-bonded nonwoven;

(3) FIG. 2: shows a schematic perspective view of an exemplary embodiment of a multi-component fiber for use in a filter medium;

(4) FIG. 3A to 3C: show schematic cross-sectional views of further embodiments of multi-component fibers;

(5) FIG. 4A to 4C: shows scanning electron micrographs of sections of embodiments of spun-bonded nonwovens;

(6) FIG. 5: shows a diagram for explaining a roughness depth of multi-component fibers;

(7) FIG. 6: shows a schematic representation of an exemplary embodiment of partially split multi-component fibers;

(8) FIG. 7: shows a schematic representation of method steps of an exemplary embodiment for producing a web of segmented pie filaments;

(9) FIG. 8: shows a schematic representation of method steps of an embodiment for producing a filter medium with the aid of a web, as described in FIG. 7;

(10) FIG. 9: shows a schematic sectional view of an exemplary embodiment of a multilayer filter medium;

(11) FIG. 10: shows a schematic sectional view of a further exemplary embodiment of a multilayer filter medium;

(12) FIG. 11: shows a perspective view of an exemplary embodiment of a pleat pack formed from a filter medium;

(13) FIG. 12: shows a schematic representation of a general motor vehicle with a filter arrangement;

(14) FIG. 13: shows a perspective view of the filter arrangement from FIG. 12, comprising a filter housing with a passenger compartment filter accommodated therein;

(15) FIG. 14: shows a perspective view of the interior filter of FIG. 13 including a frame and a pleat pack; and

(16) FIG. 15: shows pressure difference curves for filter elements with different filter media.

(17) In the figures, identical reference signs designate identical or functionally equivalent elements, provided that no information is provided to the contrary.

EMBODIMENT(S) OF THE INVENTION

(18) Spun-Bonded Nonwoven Made of Multi-Component Fibers as a Filter Medium

(19) FIG. 1 shows a schematic view of an exemplary embodiment of a filter medium made of a spun-bonded nonwoven. A nonwoven is a structure of fibers which are joined together to form a nonwoven or a fibrous layer or a fibrous web. One speaks also of so-called nonwoven materials, because in nonwovens there is usually no crossing or entangling of the fibers, as is the case with webs or other, in particular textile, tissues. In a spun-bonded nonwoven, in particular continuous filaments, which are also referred to as filaments, are joined together to form the nonwoven, which is indicated in FIG. 1 by the irregular arrangement of the fibers 1. Compared with known staple fiber nonwovens, the proposed nonwovens 10, as indicated in FIG. 1, have advantages when used as filter media.

(20) In a spin-blown process or a spun-bonding process, the nonwoven 10 is produced by melting polymers and spinning them through a nozzle system into continuous filaments. These endless filaments are then exposed to an air stream which swirls the fibers or filaments. Subsequently, a deposition takes place to the web. Optionally, solidification methods can then be used, so that a flat material is produced, for example, for filtering particles in a gas stream.

(21) The nonwoven material 10 shown in FIG. 1 comprises continuous fibers which are segmented. That is, a respective fiber, which may be referred to as a multi-component or poly-component fiber, is formed from a first and a second plastic component. In the production process, the liquid plastic components are led separately through nozzles or holes and combined to form a single continuous fiber.

(22) In FIG. 2, an example of a multi-component fiber 1 is indicated. In the schematic illustration of FIG. 2, one can see a fiber 1 which has a sheath surface 7 along its length extension Z. In FIG. 2, the fiber 1 is indicated idealized as a cylinder. In fact, the fiber 1, as indicated in FIG. 1, may have irregular bends and curves.

(23) In FIG. 2, a cross-sectional area of the multi-component fiber 1 is visible on the front side. One can see first pie segments 2, which extend along the length Z of the fiber 1, and second segments 3, which also extend along the length Z. The segments 2 consist of a first plastic component, and the segments 3, which are shown dotted, consist of a second plastic component. Due to the nature of the production in the spin-blowing process, molten plastic components nestle together as continuous filaments to the multi-component fiber 1. In the example of FIG. 2 there are six segments which are arranged in the manner of pie pieces in cross-section. They are also known as so-called segmented pie fibers.

(24) The two plastic components 2, 3, which are also referred to below as segments, lie side by side and adhere to one another. Along the length extension Z, there are outer segment boundaries 6 between the two plastic components or the segments 2, 3. Since the multi-component fiber 1 is formed as a solid material, internal segment boundaries 4 also result between the segments 2, 3. Other geometries of multi-component fibers are also conceivable. In addition to the pie segments, an expression as a core-sheath structure with an additional plastic component or one of the plastic components of the pie segments in the interior of the fiber or a fiber with pie segments is also conceivable, which has a cavity inside, yet having outer segment boundaries present on the outer surface.

(25) FIG. 3 shows by way of example schematic cross-sectional views of further exemplary embodiments. In FIG. 3A, the cross-section of a multi-component fiber 1, as indicated in FIG. 2, is shown in cross-section. (Pie) segments 2 can be seen again in cross-section 3 of a first plastic material and second segments 3 of a second plastic material. The composition can be the same. The circumference of the fiber 1 is denoted by 5. In FIG. 3A, six segments are indicated with six outer boundary lines 6. Of these, only one is provided with reference numerals for the sake of clarity. It is also possible to provide multi-component fibers with a different segmental division. For example, juxtaposed segments can be created so that outer segment boundaries result at the resulting sheath surface.

(26) FIG. 3B shows a multi-component fiber 1′ in cross-section having four segments 2, 3. In the production, for example, four nozzles are combined in a spinning beam in such a way that fibers with a corresponding cross-section are formed.

(27) In FIG. 3C, yet another multi-component fiber 1″ is indicated in cross-section. The multi-component fiber 1″ has eight segments 2, 3 and accordingly also eight outer segment boundaries 6. The diameter of the fiber is denoted by D. The multi-component fiber 1″ has, for example, a diameter of 10 μm. In known spun-bonded nonwovens, the segments 2, 3 are split after the production of the continuous filaments in order to produce smaller or thinner fibers. This is not desired in the nonwoven material proposed herein and is therefore rather or even as far as possible avoided. In the nonwoven material 10 shown in FIG. 1, the fibers retain their segmented composition, i.e., the fibers are substantially non-split.

(28) FIGS. 4A to 4C show scanning electron micrographs of sections of such spun-bonded nonwovens for use as a filter medium. The plastic components of the fibers in region I shown in FIG. 4 are both formed from a thermoplastic polyolefin provided with a lower meltable additive. The segments 2, 3 can be seen on the marked fiber in cross-section on the example of FIG. 4A. The representation essentially corresponds to the schematic representation, as it is indicated in FIG. 3C, in which case the segments 2 are smaller than the segments 3. There are 16 segments in total in FIG. 4A which are visible. Grooves 6′ can be seen along the length extension of the respective peripheral surface at the outer segment boundaries 6 of the fibers 1. The diameter D of the fiber is about 30 μm. The fibers 1 indicated in FIG. 4A are solidified into a spun-bonded nonwoven. I.e. the web, which was deposited by the spin-blown process, is thermally treated in such a way that, at the boundary points 8 or contact surfaces between separate fibers, they are fused together. This is indicated by the arrows 8 in FIG. 4A. It can be seen in particular in the lower marked area II, as the two adjacent fibers or segments are fused together.

(29) The thermoplastic polypropylene material used for the preparation is thus provided with an additive, for example a polypropylene metallocene homopolymer, which has a lower melting point than the base propylene. For example, the polypropylene PPH 9099 can be used, available from Total Research & Technology, Feluy, which is a homopolymer, and as additive, a polypropylene available under the name Lumicene MR 2001 from the same manufacturer can be used. To adjust the melting point, it is also conceivable to use a polypropylene copolymer, for example Adflex Z 101 H, which is available from Lyondell-Basell Industries Holdings B.V.

(30) It is possible to perform differential scanning calorimetry on the fibers to detect, for example, two different melting points. In a corresponding investigation, which is also referred to as DDK analysis or differential scanning calorimetry (DSC) analysis, a thermal analysis is carried out to measure the amount of heat emitted or absorbed by a sample during heating, cooling or an isothermal process. The sample is, for example, a certain amount of the spun-bonded nonwoven. By means of DDK analyzes in accordance with DIN EN ISO 11357-1, several melting points or melting temperatures of the polymer mixtures can be detected.

(31) As a result of using corresponding thermoplastic materials as plastic components, spun-bonded nonwovens, as shown in FIGS. 4A to 4C, can first be simply spun and then solidified. FIG. 4B shows another spun-bonded nonwoven as an SEM (Scanning Electron Microscope) image. The diameter D of the fibers is less than shown in FIG. 4a and is about 10 to 15 μm. In the marked area III, it can be seen how three of the endless fibers stick together and yet are completely non-split. The choice of materials and the production ensures that the fibers are present as non-split as possible. Outer segment boundaries can also be seen in FIG. 4B extending along the fibers 1 emerging as grooves 6′.

(32) FIG. 4C shows a further section of a nonwoven with even thinner multi-component fibers 1. Also in FIG. 4C it can be seen how the fibers 1 were solidified together by thermal exposure. That is, at the interface between the fibers 1, the materials are fused together.

(33) Compared to nonwovens formed from split multi-component fibers, the multi-component fibers proposed herein have a relatively smooth surface. However, for example, due to the thermal treatment on the sheath surfaces, grooves are formed between segments by the material transition. Along a circumference 5 (see FIG. C) of a corresponding multi-component fiber 1, a certain roughness is created through the grooves 6′. This is indicated schematically in FIG. 5.

(34) FIG. 5 shows a diagram in which the circumference U of a single multi-component fiber is indicated on the x-axis and the respective radius r on the y-axis. The radius r has 6 minima at the locations of the outer segment boundaries and deviates from the average radius D/2. It is thus possible to indicate a roughness along a respective circumference of a fiber.

(35) A possible measure of the roughness or smoothness of the sheath surface along a circumferential line is the average roughness depth R.sub.Z. In the investigated multi-component fibers, the average roughness depth R.sub.Z is less than 2 μm. For example, the average surface roughness R.sub.Z can be determined according to ISO 4287/1. For example, a circumferential line of a fiber is considered as a measuring section. The circumference is then divided into seven individual measuring sections, whereby the middle five measuring sections are selected to be the same size. For each of these individual measuring sections, the difference between the maximum and minimum values is determined on the circumference of the profile.

(36) Partially Split Multi-Component Fibers

(37) In FIG. 5, the minima and maxima of the radius would result in a respective minimum and maximum. The mean value is then formed for these determined single roughness depths. Due to the relatively smooth surface of the sheath surface 7 in the multi-component fibers 1, this average roughness depth is rather low. The spun-bonded nonwovens usable as filter medium (see FIG. 1), are the multi-component fibers preferably non-split and have a rather smooth peripheral line or sheath surface.

(38) The known applications of segmented pie or otherwise differently multi-component segmented fibers require splitting them into the segments in order to achieve smaller fiber units. This is done for example by an influence of a waterjet. They are also known as a hydrodynamic needling of corresponding fragmentary fibers. Usually, as explained in US 2002/0013111 A1, certain polymer materials are used for the various segments, which enable easy splitting after the spinning process. For example, polyester materials having aromatic or polylactic acid moieties are known.

(39) The investigations of the applicant have revealed that thermoplastic polymer materials, such as polyolefins, and in particular polypropylenes, are particularly well-suited to produce multi-component fibers which are less split and are also particularly resistant to known split processes. It can already be seen in FIGS. 4A to 4C that even in the thermally solidified state the multi-component fibers have coherent segments. Preferably, the proportion of partially split fibers is small.

(40) In FIG. 6, for example, a fiber is indicated schematically. The dark curves represent contiguous segments 2, 3 of a multi-component fiber 1. The length extension of the multi-component fiber 1 is indicated by Z. It can be seen in a length range Z1 that the segments 2/3 are stuck together and non-split. These segments are indicated with 2/3. As a result of impacts during the production process or during the further processing of the nonwoven materials, the fibers can basically split up. This means that individual segments are formed, which are then detached from the rest. This is designated in section Z2 by 2′/3′.

(41) In the example of FIG. 6, the ratio between the portion Z1 and the portion Z2 may be selected as a measure for splitting on the one hand or for a non-split length fraction of a fiber. Assuming that the total length of the examined fiber is Z1+Z2, there is a length fraction of the multi-component fiber 1 of Z1/(Z1+Z2) in which the segments 2, 3 of the multi-component fiber are not split or separated. In the example of FIG. 6, approximately 60% length fraction is seen to be non-split. Conversely, the length fraction of the multi-component fiber 1 indicated in FIG. 6, in which the pie segments 2′/3′ of the fiber is split from each other, is at about 40%. Preference is given to filter media in which the spun-bonded nonwoven is composed of as many non-split multi-component fibers as possible.

(42) A corresponding determination of the length fraction of one or more multi-component fibers which are not split can be effected, for example, by a sample of a predetermined section, for example 1 mm.sup.2 or 1 cm.sup.2, of the flat spun-bonded nonwoven.

(43) An alternative way of determining the splitting portion in a spun-bonded nonwoven of multi-component fibers may be the proportion of multi-component fibers in a sample that are non-split. For example, the spun-bonded nonwovens shown in the cutouts in FIGS. 4A to 4C are formed almost entirely of non-split multi-component fibers. A multi-component fiber can be classified as split if several segments detach, as is the case in the length range Z2 of the fiber 1 of FIG. 6, for example. For example, in a volume or area section of a spun-bonded nonwoven, the proportion of multi-component fibers having split-off or split segments can be counted. This is preferably not more than 50%.

(44) The more non-split multi-component fibers exist in the spun-bonded nonwoven, the better the filtration properties. What is desired is a very high proportion of multi-component fibers, in which the segments are connected to one another along their segment boundaries in the length extension.

(45) Steps in the Production Process of the Spun-Bonded Nonwoven

(46) FIGS. 7 and 8 schematically show method steps in a production method for a filter medium made of a spun-bonded nonwoven. In FIG. 7, the steps are shown in order to produce a web from first and second plastic components, and in FIG. 8, the processes for forming a solidified filter medium from the web are indicated.

(47) In a first step, the starting materials for the first plastic component and the second plastic component are provided. This is indicated in FIG. 7 by method steps S1 and S2. In the exemplary embodiment of a production method indicated below, the first component and the second component have a different composition. For example, the starting material of the first plastic component is a thermoplastic polyolefin. In particular, the PPH 9099 polypropylene available from Fa. TOTAL has proven to be suitable. PPH 9099 is a homopolymer polypropylene with a melting point of 165° C. More characteristics of possible thermoplastic polyolefins AM, MB, MC are shown in this table.

(48) TABLE-US-00001 TABLE 1 Melting point Melt Flow Index Name Manufacturer Type (ISO 3146) (ISO 1133) MA PPH 9099 Total ho-PP 165° C. 25 g/10 min MB Lumicene MR2001 Total m-PP 151° C. 25 g/10 min MC Adflex Z101H LyondellBasell co-PP 142° C. 27 g/10 min

(49) The starting material of the second component is chosen to have a lower melting point. For this purpose, for example, several portions of thermoplastic polyolefins can be used. A mixture of a polypropylene available from Fa. TOTAL has proven to be suitable under the names Lumicene MR 2001, in the following MR2001. The melting point is 151° C. MR 2001 is a metallocene homopolymer made from polypropylene. The second component may be added to another polypropylene, such as, for example, the Adflex Z 101 H available from LyondellBasell, hereinafter Adflex, having a melting point of 142° C. The mass fraction of the starting materials of the first component with the second component is for example 70% to 30%. For the first component, which consists of a single thermoplastic material, for example the aforementioned PPH 9099, one can also speak of a base material.

(50) The mass ratio between the ratio of MR 2001 to Adflex Z 101 H in the starting material of the second component is for example about 75 to 25%. In this case, the starting materials can be prepared by mixing appropriate granules of the thermoplastic materials.

(51) The starting materials of the first and second components are correspondingly metered in steps S1 and S2 and fed to an extrusion device in step S3. The molten starting materials are fed by means of an extruder in step S3 to a bonding beam with corresponding nozzles for forming the segment geometry. Optionally, filters and pumping devices may be present in the stream of the liquefied respective thermoplastic polymer.

(52) In step S4, a spun-bonding or spin-blown process is carried out in which endless filaments with the segmented pie structures are formed from the nozzles. From the spinning process, in step S4, segmented pie filaments are obtained from the first and second plastic components. By an air stream effect, the filaments are stretched and swirled and then deposited in particular on a screen belt. This is indicated in the method steps S5, S6 and S7.

(53) The stretching S5 is done by a suitable primary air supply, and the swirling S6 down-stream in the manufacturing process by secondary air. This results in a web during the dropping S7 of segmented filaments, which can also be referred to as multi-component filaments. The resulting web then has a thickness of between 1 and 2 mm.

(54) In an optional step, it is possible to thermally pre-solidify the web by sucking the filaments on the one hand through the filing screen or screen belt, and on the other hand by solidifying or pre-solidifying with the aid of, for example, hot air or other thermal exposure. One can call this web a semi-finished product that already has spun-bonded nonwoven properties. In principle, this semi-finished product can already be used for filtering fluids.

(55) In order to achieve an even better, also mechanical property of the spun-bonded nonwoven from multi-component segmented pie filaments, a further solidification takes place. This is indicated schematically in FIG. 8. The pre-solidified web is guided in a bonding or solidification step S9 between spaced screen belts, rolls or rollers and simultaneously exposed to a temperature which is higher than the melting temperature of at least one of the two plastic components. For example, when using the polypropylene materials previously listed in the table, thermal bonding can occur at temperatures between 150° C. and 158° C. The thermally solidified spun-bonded nonwoven then has a thickness of between 0.5 and 1.5 mm, for example. The thickness can be adjusted by the spacing of the screen belts or heatable rolls or rollers.

(56) In the proposed production method, in particular no apparatus for hydrodynamic solidification, needling or chemical solidification or bonding are used. This reduces the amount of split multi-component fibers in the spun-bonded nonwoven.

(57) In a subsequent step S10, the solidified spun-bonded nonwoven is charged. Charging takes place, for example, with the aid of wire or rod electrodes, which opposite rollers, over which the flat and rollable spun-bonded nonwoven is guided. In particular, an apparatus and a charging method can be used for this purpose, as explained in U.S. Pat. No. 5,401,446. U.S. Pat. No. 5,401,446 is hereby incorporated by reference (“incorporation by reference”). Investigations by the applicant have shown that in particular a stage charge, as shown for example in FIG. 1 of U.S. Pat. No. 5,401,446, is favorable with the aid of two successively connected charging drums and charging electrodes.

(58) Subsequently, the obtained charged spun-bonded nonwoven is provided as a filter medium, for example, in roll form (step S11). Throughout the entire production path of the spun-bonding process, the multi-component fibers remain non-split or largely non-split. In the case of thermal solidification in step S9, for example, only a part of the thermoplastic material is melted from the starting materials and leads to the interconnection of different multi-component fibers.

(59) The flat filter medium of a single-layer spun-bonded nonwoven is now provided in particular in roll form. High quality filter media can be achieved from the sheet material due to the filtration properties, but also due to the mechanical handling in terms of its flexural rigidity.

(60) Comparison of the Mechanical Properties of the Filter Medium with Comparative Nonwovens

(61) The applicant has carried out comparative investigations, for example on the flexural rigidity of spun-bonded nonwoven made according to the proposed method, with materials processed in commercially available filter elements. A filter element of the type CU 3054 distributed by the manufacturer MANN+HUMMEL GmbH was examined. In the following table the flexural rigidities of a test nonwoven are compared with those of comparative nonwovens. Commercially available filter elements are partly manufactured with filter medium from different manufacturers. Comparative nonwovens 1, 2 and 3 are based on commercially available filter media for interior filters.

(62) TABLE-US-00002 TABLE 2 Flexural rigidity according to DIN 53121 Sample Type Front Back Medium Test nonwoven 1 Spun-bonded fabric 210 mN 219 mN 214.5 mN Comparative nonwoven 1 Meltblown 157 mN 165 mN 161 mN Comparative nonwoven 2 Meltblown 149 mN 149 mN 149 mN Comparative nonwoven 3 2-ply  63 mN  51 mN 57 mN

(63) The test nonwoven 1 used two plastic components. Three thermoplastic materials MA, MB and MC were used, with MA PPH 9099, MB MR2001 and MC Adflex being chosen. The first plastic component essentially comprises MA. The second plastic component essentially comprises a mixture of MB and MC in the ratio 3:1. Overall, the mass ratio in the fiber is: MA: 70%, MB: 22.5% and MC: 7.5%. A spun-bonded nonwoven of the grammage or a weight per unit area of 100 g/m.sup.2 was produced and investigated using a system available from Reifenhäuser Reicofil as test nonwoven 1. The thickness of the spun-bonded nonwoven was 1.14 mm with a weight of 106 g/m.sup.2. The measurements were carried out according to DIN 29076-2 or DIN 29073-1. There were sixteen pie segments in the fibers.

(64) The comparative nonwoven 1 can be used for a commercial filter element CU3054 of the manufacturer MANN+HUMMEL GmbH and is made of a polypropylene with a grammage of 125 g/m.sup.2 and has a thickness of 1.25 mm.

(65) The comparative nonwoven 2 can be used for a commercial filter element CU3054 of the manufacturer MANN+HUMMEL GmbH and is made of a polypropylene with a grammage of about 146.5 g/m.sup.2 and has a thickness of about 1.15 mm.

(66) The comparative nonwoven 3 can be used for a commercial filter element CU3054 of the manufacturer MANN+HUMMEL GmbH and is made of a two-ply polyester/polypropylene material with a grammage of about 105 g/m.sup.2 and has a thickness of 0.6 mm. The carrier layer made of polyester is provided with a meltblown layer of polypropylene.

(67) It can be seen that compared to conventional comparative media based either on spun-bonded or multilayered materials, they have improved flexural rigidity. This allows a particularly good further processing, for example in filter elements made of zigzag-pleated filter media.

(68) Possible Additional Equipment of Filter Media

(69) In FIG. 9, a further embodiment for a filter medium 11 is indicated. The embodiment comprises a first filter layer 9, for example of a meltblown material, onto which is applied a spun-bonded nonwoven 10, which is composed essentially of non-split multi-component fibers.

(70) In order to further improve or change the filtration properties, it is possible, as indicated in FIG. 10, to embed adsorbent particles 13 in or between layers of filter media. For example, the filter medium 12 has a first layer of a meltblown material 9 and a second layer of the described spun-bonded nonwoven 9′. In between, for example, adsorber particles 13 of activated carbon or other adsorbent agents are embedded. As a result, volatile hydrocarbons, for example, can be retained in addition to particle filtration when the filter medium 12 passes through.

(71) Filtration Properties of Filter Media

(72) The applicant has produced further test webs and examined their properties. In the following table 3, the thicknesses, the air permeability, the grammage and the flexural rigidity are shown for test nonwovens 1 to 4.

(73) TABLE-US-00003 TABLE 3 Thickness Air permeability Grammage Sample (DIN 29076-2) (DIN 9237) (DIN 29073-1) Test nonwoven 2 0.86 mm 4500 l/m.sup.2s 88 g/m.sup.2 Test nonwoven 3 0.90 mm 2323 l/m.sup.2s 90 g/m.sup.2 Test nonwoven 1 1.14 mm 1809 l/m.sup.2s 106 g/m.sup.2 Test nonwoven 4 1.18 mm 1705 l/m.sup.2s 124 g/m.sup.2

(74) For the test nonwovens 2, 3 and 4, the same starting material was used as for the test nonwoven 1 for the two plastic components of the segments.

(75) Table 4 lists the filtration properties of the test nonwovens.

(76) TABLE-US-00004 TABLE 4 NaCl deposition ISO A2 initial ISO A2 initial ISO A2 dust efficiency separation separation retention capacity at 0.3 μm at 1 μm at 5 μm at 50 Pa Sample (DIN 71640-1) (DIN 71460-1) (DIN 71460-1) (DIN 71460-1) Test nonwoven 2 24% 80% 87% 65 g/m.sup.2 Test nonwoven 3 43% 88% 95% 34 g/m.sup.2 Test nonwoven 1 47.3%.sup.  94.4%.sup.  97.5%.sup.  36.2 g/m.sup.2 Test nonwoven 4 52% 93% 98% 34 g/m.sup.2
Pleated Filter Media and Filter Elements

(77) In the following FIG. 11, a zigzag-pleated medium is shown as a pleat pack 20. The filter medium 10 accordingly has pleats 21, which typically extend transversely to the machine direction M. The pleated filter medium is also referred to as a pleat pack 20 or pleated. The pleats 21 may be produced by pleating along sharp pleat edges 22 (also referred to as pleat tips) or by a wavy embodiment of the filter medium 10. A respective pleat 21 may be defined by two pleat sections 23, which are connected to one another via a corresponding pleat edge 22. According to the exemplary embodiment, the pleated edges 22 point in or against the direction of flow, which is indicated in FIG. 11 by the arrow L.

(78) A pleat in which the pleats 21 have a varying height H is also possible. Further, the pleat spacing between the pleats 21 may vary so that the distance D.sub.1 is not equal to the distance D.sub.2. The pleat pack 20 may be designed to be self-supporting, i.e. the pleats 21 are dimensionally stable in the case of an intended flow in the filter operation.

(79) The filter medium 10 used is limited in the machine direction M by end pleats 30, 31. Transverse thereto, the filter medium 10 is bounded by pleat end edges 19, 20 (also referred to as pleat profiles 33). By “pleat end edge” it is meant the end face pleat surface which extends between adjacent pleat edges 33 of a respective pleat 22.

(80) The filter medium 10 may have a rectangular shape in plan view, that is, in the plane E of its planar extension. However, a triangular, pentagonal or polygonal, round or oval shape is also conceivable.

(81) One possible application is the use of the respective filter medium in interior air filters for motor vehicles. FIG. 12 shows a motor vehicle 14 with an air conditioner 15, which may be formed as a heating air conditioner. The air conditioner 15 receives outside air 16 and supplies filtered air 17 to a cabin 18 (also referred to as a passenger compartment) of the motor vehicle 14. For this purpose, the air conditioner 15 comprises a filter arrangement shown in FIG. 13.

(82) The filter arrangement 24 comprises a filter housing 19 with an interior filter 32 accommodated therein, in particular exchangeably. The interior filter 32 is shown in more detail in FIG. 14. The interior filter 32 comprises a filter medium pleated as a pleat pack 20 (see. FIG. 11), which in particular is all around connected to a frame 25. The frame 25 may include, for example, sidebands 26, 27 and headbands 28, 29.

(83) The sidebands 26, 27 shown in FIG. 14 are connected to the pleat end edges 33, the headbands 28, 29 to the end pleats 30, 31, in particular by fusing, abrasing or gluing. The sidebands 26, 27 and the headbands 28, 29 may form the frame 19 in one piece or in several parts. The sidebands 26, 27 and the headbands 28, 29 can be made, for example, from a particularly flexible fiber material or as in particular rigid synthetic injection molded components. In particular, the frame 19 may be produced by injection molding on the pleat pack 20.

(84) In filter operation, the filter medium 10, as shown in FIG. 11 or 13, flows perpendicular to its flat extent of air L. The air L flows from a raw side RO of the cabin air filter 8 toward a clean side RE thereof.

(85) In order to ensure a sufficient seal between the raw and clean sides RO, RE, a seal between the cabin air filter 32 and the filter housing 19 may be provided. The seal may, for example, be integrated in the frame 25. In this case, the frame 25 is at least partially formed of a sealing material. Alternatively, the seal can be provided as an additional part, for example, attached, in particular be molded, onto the frame 25.

(86) The filter element 32 reproduced in FIG. 14 surrounds a cuboidal volume with the boundary surfaces A.sub.1, A.sub.2, A.sub.3. The largest boundary surface A.sub.1 corresponds to the outflow or inflow side of the filter element 32.

(87) Filtration Properties of the Pleat Pack

(88) The applicant has carried out comparative investigations in which prior art filter elements, namely CU 3054 interior air filter elements manufactured by MANN+HUMMEL GmbH, have been compared with filter elements of identical geometrical design. The comparison and test filter elements have a shape as shown in FIG. 14. The test filter elements are equipped with a respective spun-bonded nonwoven made of multi-component fibers produced by the method proposed herein. The spun-bonded nonwovens were solidified and subjected to a charge. For this purpose, three electrode arrangements each having a voltage between the electrode and the winding roll of 25-35 kV have been used. The distance to the spun-bonded nonwoven was about 20 to 40 mm, and the running speed along the electrode assemblies was between 30 and 40 m/min. The flat spun-bonded nonwoven present as rolled goods was then subjected to zigzag pleating and provided with sidebands and headbands according to CU 3054.

(89) Each filter element tested has a length extension of 292±1.5 mm, a width of 198.5±1 mm and a height of 30±1 mm. This results in pleat heights H=28 mm with a total of 42 pleats in the resulting pleat pack. The pleat spacing D.sub.1=D.sub.2 is 7 mm. The filter area is thus 0.466 m.sup.2 for a cover area A.sub.1 of the filter element of 0.058 m.sup.2 (see FIG. 9, 14). The commercially available filter elements are available with different retention capacities. In the commercial comparative filter elements, a filter medium made of a meltblown nonwoven is used. Alternatively, a two-ply material of high retention polyester and polypropylene can be used.

(90) FIG. 15 shows curves from pressure drop measurements of a test pack 3 for the filter grade D and a commercial filter element CU 3054 having a conventional filter medium. Over the entire volume flow range of 100 to 600 m.sup.3/min, the filter element with a pleat pack of multi-component spun-bonded fibers substantially non-split in the filter element (Test pack 3) provides better results than the prior art filter medium (Comparison pack 3).

(91) From the following table it can be seen that the proposed single ply spun-bonded nonwovens of propylene blends result in improved rates of separation and improved pressure drops. All measurements were carried out in accordance with DIN 71460-1.

(92) TABLE-US-00005 TABLE 5 NaCl deposition ISO A2 initial ISO A2 initial Pressure drop efficiency separation separation Sample at 600 m.sup.3/h at 0.3 μm at 1 μm at 5 μm Comparison pack 1 39 Pa 12% 46% 66% Test pack 1 36 Pa 24% 79% 86% Comparison pack 2 58 Pa 20% 69% 94% Test pack 2 55 Pa 39% 92% 96% Comparison pack 3 137 Pa 54% 95% 99% Test pack 3 77 pa 49% 95% 98%

(93) In this respect, a filter element made from the proposed spun-bonded nonwoven is superior to the known filter element materials. This applies in particular with regard to the flexural rigidity of the filter medium, the retention capacity and the dust storage capacity. The higher the requirements for filter media and filter elements, the better the proposed spun-bonded non-spliced multi-component fibers.

(94) Reference Signs Used:

(95) 1 Multi-component fiber 2, 3 Segments/plastic component 4 Inner segment boundary 5 Circumference 6 Outer segment boundary 6′ Longitudinal groove 7 Sheath surface 8 Junction 9 Meltblown material 10 Spun-bonded nonwoven 11 Filter medium 12 Filter medium 13 Adsorber particles 14 Motor vehicle 15 Air conditioner 16 Outside air 17 Filtered air 18 Interior 19 Filter housing 20 Pleat pack 21 Pleat 22 Pleat edge 23 Pleat section 24 Filter arrangement 25 Frame 26 Sideband 27 Sideband 28 Headband 29 Headband 30 End pleat 31 End pleat 32 Interior air filter 33 Pleating profile D.sub.1, D.sub.2 Pleating distance A.sub.1, A.sub.2, A.sub.3 Boundary surface E Level H Pleat height L Air flow M Machine direction U Circumference D Diameter Z Length extension RO Raw air area RE Clean air area