INDUSTRIAL FABRIC, METHOD FOR PRODUCING A NONWOVEN, AND USE OF AN INDUSTRIAL FABRIC

Abstract

An industrial fabric (30, 40, 45) is provided, in particular for transporting a nonwoven web while producing same, having a product side (PS), which is in contact with the nonwoven, and a machine side (MS), which is in contact with transport devices of a system (1) for producing the nonwoven. The fabric (30, 40, 45) has MD threads (32, 33, 43, 44, 48, 50), which run in the running direction of the nonwoven web, and CMD threads (31, 41, 42, 52), which run perpendicularly to the MD threads, said threads being woven together. At least two layers of MD threads (32, 33, 43, 44, 48, 50) are provided which are stacked one over the other in pairs and form product contact MD threads (32, 43, 50) and non-product contact MD threads (33, 44, 48). At least the material of each product contact MD thread (32, 43, 50) facing the product side (PS) forms a contact angle, measured according to the Wilhelmy plate method, of at least 80°, preferably at least 90°, more preferably at least 100°. In order to prevent the adhesion of threads to the fabric (30, 40, 45) and in order to reduce the air permeability, the fabric has a single layer of CMD threads (31, 41, 42, 52), and the cross-section of each product contact MD thread (32, 43, 50) has at least two regions, a first region of which is formed of the first material and a second region of which is formed of the second material. A substantial proportion, preferably a predominant proportion, of a tensile force acting on each product contact MD thread (32, 43, 50) can be transmitted from the second region, and the cross-section of the product contact MD threads (32, 43, 50) have a second region in the form of a core (61) and a first region in the form of a casing (62) which surrounds the core (61). The product MD threads (32, 43, 50) are preferably coextruded or are extruded in two successive steps. The MD threads (32, 33, 43, 44, 48, 50) have a flattened cross-section, preferably a rectangular cross-section, wherein a ratio of a height of the cross-section to a width of the cross-section preferably ranges from 1:1.2 to 1:10, preferably from 1:1.5 to 1:4. The invention further relates to a method for producing a nonwoven and to the use of an industrial fabric (30, 40, 45).

Claims

1. An industrial fabric (30, 40, 45, 70) for transporting a web of a nonwoven, the industrial fabric comprising a product side (PS) that is adapted to be in contact with the nonwoven, and a machine side (MS) that is adapted to be in contact with conveying devices of a system (1) for producing the nonwoven, at least two layers of MD threads (32, 33, 43, 44, 48, 50, 72, 73) adapted to be oriented in a running direction of a web of the nonwoven and CMD threads (31, 41, 42, 52) that are oriented perpendicular to the MD threads and are interwoven with the at least two layers of the MD threads, the at least two layers of MD threads (32, 33, 43, 44, 48, 50, 72, 73) are arranged stacked in pairs one above and below each other, and form product contact MD threads (32, 43, 50, 72, 73) and non-product contact MD threads (33, 44, 48), at least a surface of the respective product contact MD threads (32, 43, 50, 72, 73) facing the product side (PS) has a first material that has a contact angle, measured according to the Wilhelmy plate method, of at least 80°, the CMD threads (31, 41, 42, 52) are arranged in a single layer, and each cross section of the product contact MD threads (32, 43, 50, 72, 73) has at least first and second areas, the first area is made from a first material and the second area is made from a second material, wherein a majority of a tensile force acting on the respective product contact MD threads (32, 43, 50) is transferred by the second area and the second area of the product contact MD threads (32, 43, 73, 73) is formed as a core (61) and the first area is formed as a casing (62) surrounding the core (61), wherein the product contact MD threads (32, 43, 50, 72, 73) have a flattened cross section, and a ratio of a height of the cross section to a width of the cross section is between 1:1.2 and 1:10.

2. The industrial fabric (30, 40, 45, 70) according to claim 1, wherein the first area is made from a fluorine-containing polymer or copolymers of polyethylene with the fluorine-containing polymer.

3. The industrial fabric (30, 40, 45, 70) according to claim 1, wherein the second area is made from polyamide, polyphenylene sulfide, polyether ether ketone, polypropylene, aramid, polyethacetone, or polyethylene naphthalate.

4. The industrial fabric (30, 40, 45, 70) according to claim 1, wherein at least one material facing the product side (PS) of at least said CMD threads (31, 41, 42, 52) that are adapted to contact the web of the nonwoven have a contact angle, measured according to the Wilhelmy plate method, of at least 80°.

5. The industrial fabric (30, 40, 45, 70) according to claim 1, wherein the CMD threads (31, 41, 42, 52) have a round cross section.

6. The industrial fabric (30, 40, 45) according to claim 5, wherein the CMD threads include first CMD threads (41) with a larger diameter and second CMD threads (42) with a smaller diameter that are alternately arranged one behind the other in a direction of the MD threads (43, 44), and the second CMD threads (42) with the smaller diameter are engaged with the MD threads (43, 44) and at least one surface of the second CMD threads (42) with the smaller diameter facing the product side is made from a material that has a contact angle, measured according to the Wilhelmy plate method, of at least 80°.

7. The industrial fabric (30, 40, 45, 70) according to claim 1, wherein at least one of the MD threads (32, 33, 43, 44, 48, 50) or the CMD threads (31, 41, 42, 52) are monofilaments.

8. The industrial fabric (30, 40, 45, 70) according to claim 1, wherein at least one part of at least one of the MD threads (32, 33, 43, 44, 48, 50) or the CMD threads (31, 41, 42, 52) is electrically conductive, and includes carbon on an outer casing of the cross section of the at least one of the MD threads or CMD threads, or carbon nanotubules are contained in the material of the at least one of the MD threads (32, 33, 43, 44, 48, 50) or the CMD threads (31, 41, 42, 52).

9. The industrial (30, 40, 45, 70) according to claim 1, wherein the fabric is closed by a seam connecting two fabric ends to form an endless conveyor belt, the seam is a spiral seam that has two seam spirals (74) that extend over an entire width of the conveyor belt and are turned in or hooked into loops (71) of the MD threads (72, 73) of opposing fabric ends and both are coupled with each other by a closing wire extending over the entire width of the conveyor belt.

10. The industrial fabric (30, 40, 45) according to claim 9, wherein the seam spirals (74) include a thread (75) having a cross section with a core (76) and a casing (77) surrounding the core (76), the casing (77) is made from a material that has a contact angle, measured according to the Wilhelmy plate method, of at least 80°.

11. The industrial fabric according to claim 1, wherein a cross-sectional area of the threads (31, 32, 33, 41, 42, 43, 44, 48, 50, 72, 73) is at least 0.0003 mm.sup.2.

12. A method for producing a nonwoven that is aerodynamically formed and at least one of chemically or thermally cured, comprising: moving a web of the nonwoven is on a surface of a conveyor belt (9, 12, 15) made from an industrial fabric (30, 40, 45) according to claim 1.

13. A method of using an industrial fabric (30, 40, 45) according to claim 1, comprising: forming the industrial fabric into a conveyor belt (9, 12, 15) for transporting a web of a nonwoven during its production, and carrying the web of the nonwoven during its thermal hardening through molten material processing or chemical hardening through curing either in a drying device (8) or curing device (14).

14. The industrial fabric (30, 40, 50) according to claim 1, wherein the product contact MD threads are coextruded or extruded in two successive steps.

15. The industrial fabric (30, 40, 50) according to claim 1, wherein the fluorine containing polymer is a PVDF, an ETFE, or a PTFE polymer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The invention will be explained in more detail below with reference to an embodiment of a system for producing a nonwoven, as well as several embodiments of industrial fabric from which a conveyor belt for use in a production system can be made.

[0033] Shown are:

[0034] FIG. 1: a schematic illustration of the production steps for a nonwoven,

[0035] FIG. 2: a longitudinal section, an industrial fabric in a first embodiment,

[0036] FIG. 3: a longitudinal section through an industrial fabric in a second embodiment,

[0037] FIG. 4: a cross section through the fabric according to FIG. 4 in the area of a first CMD thread,

[0038] FIG. 5: like FIG. 4 but in the area of a second CMD thread,

[0039] FIG. 6: a cross section through an MD thread,

[0040] FIG. 7: a longitudinal section through an industrial fabric in a fourth embodiment in the area of seam loops,

[0041] FIG. 8: a section of a top view of two ends of an industrial fabric for closing the seam, and

[0042] FIG. 9: a perspective view of a fabric according to the invention in a fifth embodiment in the area of a spiral seam.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0043] A system 1 shown in FIG. 1 is used for producing an aerodynamically formed and both thermally and also chemically cured nonwoven that leaves the system 1 at the position 2 as an endless web. The nonwoven is formed from a fiber pulp, mixed with two-component fibers and a very water-absorbent plastic granulate. The two-component fibers have a core made from polypropylene with a higher melting point and a casing made from polyethylene surrounding the core with a lower melting point. The starting materials are fed by means of a feeder 3 to a forming belt 4 where a material layer is formed. With the help of a transfer belt 5, the nonwoven web is transferred to a spraying device 6 where a coating of a polymer dispersion with bonding properties is applied. For passing through the spraying device 6, the nonwoven web is transported by a belt 7.

[0044] Downstream of the spraying device 6, the nonwoven web is fed into a first drying device 8 (furnace) where the web is transported by a conveyor belt 9. In the drying device 8, the casings of the two component fibers are melted and the polymer dispersion sprayed in the spraying device 6 is hardened. This produces the cohesion of the fibers of the nonwoven.

[0045] Downstream of the first drying device 8, the nonwoven web is fed by a belt 10 through a second spraying device 11 before it is guided by a second conveyor belt 12 through a second drying device 13. A final curing of the nonwoven web is performed in a curing device 14 where the nonwoven web is transported with the help of a third conveyor belt 15. Finally, the final nonwoven web is guided with the help of a discharge belt 16 to the output (position 2) of the system 1.

[0046] One problem of known systems is that the spaces in conveyor belts 9, 12 become clogged with non-bound fibers, so that the permeability of the conveyor belts 9, 12 decreases and sufficient air can no longer be guided into the drying devices 8, 13 through the nonwoven web. The heat transfer to the nonwoven web is then inadequate, which leads to inadequate cohesion of the fibers and thus inadequate strength of the nonwoven web, because the necessary temperatures can no longer be achieved. A remedy is now created according to the invention by a fabric that is shown in FIGS. 2 to 8 and will be explained in more detail below.

[0047] FIGS. 2 and 3 each show a longitudinal section, i.e., a section parallel to the threads oriented in the running direction of the nonwoven web, through industrial fabric 30, 40.

[0048] FIG. 2 shows a fabric 30 with only one layer of CMD threads 31, but, in turn, two MD threads 32 and 33 in a stacked arrangement. These have the same profile within the fabric; these are therefore so-called double threads. The MD threads 32, 33 always maintain their orientation relative to each other, i.e., they are not turned toward or with each other. The MD thread 32 that is arranged on the product side PS of the fabric 30 thus lies above the MD thread 33 arranged on the machine side MS. With their surface areas facing each other, the MD threads 32 and 33 oriented in a stacked arrangement are in direct contact. As still to be explained below, the MD threads 32, 33 have a flattened rectangular cross section, so that, in the fabric composite, a stable stack and maintenance of the arrangement can be achieved relative to each other.

[0049] An industrial fabric 40 shown in FIG. 3 contains CMD threads 41 and 42 arranged in a single CMD layer. In addition, two layers of MD threads 43 and 44 are present in the fabric 40, wherein the MD threads 44 are arranged on the machine side MS and the MD threads 43 are arranged on the product side PS. As also produced, in particular, from the cross-sectional illustrations according to FIGS. 4 and 5, the CMD threads 42 that have a smaller diameter are binding threads (see FIG. 5), while the CMD threads 41 having a larger diameter are to be designated as pure filling threads and run in a relatively straight line through the fabric 40 (see FIG. 4). It can be seen that the CMD threads 41 separate each pair of MD threads 43, 44 from each other (FIG. 4), while the MD threads 43, 44 in the area of the CMD threads 42 contact each other directly, i.e., are in planar contact with each other. In the case of the fabric 40, the MD threads 43, 44 are the warp threads and the CMD threads 41, 42 are the weft threads.

[0050] FIG. 6 shows a cross section through an individual MD thread, how it can be used in the fabrics 30, 40 on the product side PS (MD threads 32, 43). The flattened rectangular MD thread has a core 61 (thread core) and a casing 62 (thread casing) surrounding this core. The outer contour of the core 61 is rectangular and has a height 63 of 0.36 mm and a width 64 of 1.07 mm. The casing 62 is also rectangular in its outer contour and has a height 65 of 0.45 mm and a width 66 of 1.20 mm. A thickness 67 of the casing 62 is produced on its longitudinal sides of approx. 0.045 mm. The casing 62 is formed of a material with especially high surface energy, such as, for example, PVDF. In contrast, the core 61 is made from a material with good mechanical properties with especially high tensile strength, e.g., polyester (PET). Both the material of the core 61 and also of the casing 62 offer a sufficiently large temperature resistance up to 200° C.

[0051] FIG. 7 shows, as an example in a longitudinal section illustration, the formation of a seam on a fabric 45 that must be combined into an endless belt like the fabric 30, 40 already described above, in order to be able to be used as a conveyor belt 9, 12, 15 in the system 1. On one seam end 46 of the fabric 45, seam loops 47 are formed such that a lower MD thread 48 is cut at a position 49 and the remaining section facing the seam end 46 is removed. In the channel formed previously by the MD thread 48, the upper MD thread 50 (product contact MD thread) of the associated stacked pair is inserted and fed back with its end 51 up to the position 49 at which the lower MD thread 48 (non-product contact MD thread) ends. In this way, the seam loop 47 made from the MD thread 48 is formed at the seam end 46. The CMD threads 52 of the fabric 45 remain undisturbed during this seam formation.

[0052] From FIG. 8 it can be seen that for two opposing seam ends 46, 53 of the fabric 45 to be joined together to form a closed belt, alternating seam loops 47 were formed from the MD threads 50 and the adjacent MD threads 50 are left without seam loop formation. For an offset arrangement of the seam loops 47 on the opposing seam ends 46, 53, the two seam ends 46, 53 can be pushed together relative to each other in the direction of the arrows 54, 55 like a kind of positive-locking fit. In this way, the rows of seam loops 47 nested with each other form a continuous seam channel in which a closing wire 56 is inserted (like a kind of CMD thread), whereby the seam is closed and an endless belt is produced.

[0053] FIG. 9 shows a perspective view of another fabric 70 according to the invention with an alternative embodiment of the seam, namely in the form of a spiral seam. An industrial fabric 70 that has the same construction, apart from the seam ends, as the fabric according to FIGS. 3 to 5 has, on two free ends (viewed in the MD direction), chain loops 71 that are formed from the MD threads 72, 73 in that these are woven back over a certain length on the machine side MS of the fabric 70. In the chain loops 71 whose ends are on a common straight line that runs perpendicular to the MD threads 72, 73, a thread 75 with a spiral shape is pulled for the formation of a spiral thread 74, that is, through each chain loop 71 individually. The thread 75 has a round of flattened cross section and is made from two components, namely a thread core 76 and a thread casing 77 concentrically surrounding this core in cross section. The thread 75 can be produced by coextrusion or by a multi-step extrusion process, in that initially the thread core 76 is produced by extrusion and then is surrounded with the material of the thread casing 77 in the course of a second extrusion process. The casing 77 is made like the surface of the MD threads 72, 73 facing the product side PS from a material that has a contact angle, measured according to the Wilhelmy plate method, of at least 80°. The closing of the seam is realized such that both ends of the fabric 70 are intermeshed with each other with their seam spirals, so that within the seam spirals 74 of the two ends, a closing channel 78 is formed in which a not-shown closing wire is inserted in a longitudinal direction 79 of the seam spirals 74, whereby the two fabric ends are connected to each other.

[0054] Due to the surface properties of the threads 75 in the seam area, the risk is prevented that undesired adhesion is produced in this area, which could have occurred if the threads 75 forming the seam spirals 74 were made from a material with a lower contact angle. The core 76 present in this thread 75 makes it possible, through the selection of a material with a high tensile strength, to ensure the necessary stability and tensile load bearing capacity of the seam.

LIST OF REFERENCE SYMBOLS

[0055] 1 System [0056] 2 Position [0057] 3 Pick-up device [0058] 4 Forming belt [0059] 5 Transfer belt [0060] 6 Spraying device [0061] 7 Belt [0062] 8 Drying device [0063] 9 Conveyor belt [0064] 10 Belt [0065] 11 Spraying device [0066] 12 Conveyor belt [0067] 13 Drying device [0068] 14 Curing device [0069] 15 Conveyor belt [0070] 16 Discharge belt [0071] 30 Fabric [0072] 31 CMD thread [0073] 32 MD thread [0074] 33 MD thread [0075] 40 Fabric [0076] 41 CMD thread [0077] 42 CMD thread [0078] 43 MD thread [0079] 44 MD thread [0080] 45 Fabric [0081] 46 Seam end [0082] 47 Seam loop [0083] 48 MD thread [0084] 49 Position [0085] 50 MD thread [0086] 51 End [0087] 52 CMD thread [0088] 53 Seam end [0089] 54 Arrow [0090] 55 Arrow [0091] 56 Closing wire [0092] 61 Core [0093] 62 Casing [0094] 63 Height [0095] 64 Width [0096] 65 Height [0097] 66 Width [0098] 67 Thickness [0099] 70 Fabric [0100] 71 Chain loop [0101] 72 MD thread [0102] 73 MD thread [0103] 74 Seam spiral [0104] 75 Thread [0105] 76 Core [0106] 77 Casing [0107] 78 Closing channel [0108] PS Product side [0109] MS Machine side