System and method for producing a single-layer or multi-layer nonwoven

Abstract

The invention relates to a system and a method, comprising - at least one carding machine (1), which is designed to generate a fibrous web (3) by means of an aerodynamic process, - a first conveying belt (4), which is designed to convey the fibrous web (3) from the carding machine to a compactor, - a compactor, which is designed to compact the fibrous web (3) to a nonwoven (24), - a drafting device (10), which is arranged downstream in the material-conveying direction and is designed to draw the nonwoven (24) by at least the factor of 1.5, - and a consolidator, which is arranged downstream in the material-conveying direction.

Description

[0001] The invention relates to a system and a method for producing a single- or multi-layer nonwoven fabric.

[0002] In the production of nearly isotropic nonwovens from fibers used, for example, in wipes or hygiene products, the carded fiber rovings are folded in a cross-folder to create a nonwoven with a medium-thickness / thickness ratio (MD / CD) of 1.3:1 to 2.1:1, which is then further consolidated after the cross-folder. For example, if the desired end product is a nonwoven with a weight of 40 g / m², the carding machine produces a fiber roving with a weight of 30 g / m². This fiber roving then enters a subsequent nonwoven at a speed of, for example, 100 m / min, where it is folded into four layers to achieve the desired MD / CD ratio. The multi-layered nonwoven then exits the cross-folder at a speed of, for example, 22 m / min and enters a drafting and consolidation station, after which it is wound up at a speed of 80 m / min.The lighter the nonwoven fabric produced by the carding machine, the more sensitive the folding or cross-folding process in the cross-folder becomes, as air currents and high speeds significantly affect the folding process. Furthermore, a cross-folder represents a very expensive investment for the plant operator, requiring considerable space due to the L-shaped material flow and undesirably limiting production quality and quantity.

[0003] For example, EP 0777771 B1 discloses a device for the aerodynamic production of a fiber fleece, also known as an airlay carding machine. These airlay carding machines can produce a nearly isotropic fiber fleece. A disadvantage is the slow production speed at higher nonwoven weights.

[0004] WO 2018 / 055181 A1 discloses a carding machine for the aerodynamic production of a fiber fleece with a thermal post-treatment of the nonwoven.

[0005] The brochure Carding Lines (by Autefa Solutions, published 09 / 2011) shows classic carding lines in which the carding device is always arranged after a cross-folder.

[0006] EP 3118361 A1 discloses a plant for wet-laid fibers which can be operated alone or in combination with a conventional carding machine or with a carding nonwoven only.

[0007] The object of the present invention is to provide a system and a method for producing a single- or multi-layer nonwoven fabric that is flexible in its application and with which almost isotropic nonwoven fabrics can be produced with high productivity.

[0008] The invention solves the stated problem by means of the teachings according to claims 1 and 12; further advantageous features of the invention are characterized by the dependent claims.

[0009] According to the technical teaching of claim 1, the system for producing a single- or multi-layer nonwoven fabric comprises at least one carding machine configured to generate a fiber pile by means of an aerodynamic process, and a first conveyor belt configured to transport the fiber pile from the carding machine to a compaction unit, wherein the compaction unit is configured to compact the fiber pile into a nonwoven fabric.

[0010] Due to the aerodynamic production of the fiber nap, it exhibits a high degree of isotropy, which can otherwise only be achieved using wet-laid or air-laid processes. In contrast to these processes, an air-laid carding machine, for example, can process a wide range of fiber lengths, fiber finenesses, and fiber types.

[0011] To efficiently process the large mass of fiber fleece produced, the invention provides that a downstream stretching device is arranged in the material transport direction, which is designed to stretch the nonwoven fabric by a factor of at least 1.5. Subsequently, the nonwoven fabric can be consolidated in various ways.

[0012] The system is configured to produce an isotropic nonwoven fabric with high productivity without a lay-up unit. The system's productivity is higher than that of a conventional carding machine with a subsequent lay-up unit, and the investment costs are significantly lower. With the same basis weight of the finished product, for example, 40 g / m², productivity can be doubled according to the invention. A further advantage is the reduced defect rate in the nonwoven fabric production, since folding thin nonwovens or fiber woven fabrics often results in edge folding, leading to uneven material accumulation across the cross-section.

[0013] The system can include at least one additional carding unit designed to generate another fiber web using an aerodynamic process. If space permits, any number of carding units can be arranged in a row, with their fiber webs being processed together. By varying the number of carding units used and stretching the nonwoven fabric by a factor of 1.5 to 4, the final product can be varied almost arbitrarily in terms of basis weight and productivity. The system becomes more flexible and less expensive than a system with a conventional carding unit and lay-up unit. The same or different fiber qualities can be used.

[0014] In a system of multiple carding machines arranged in a row, the conveyor belt for transporting the fiber mat from the first carding machine (in the direction of material transport) can be located at least partially beneath the subsequent carding machines. The conveyor belt can run underground or be positioned between the supports of the carding machines.

[0015] Prior to compaction, a separate conveyor belt can be installed, designed to collect the fiber piles layered on top of each other. It is not necessary to synchronize this separate conveyor belt with the carding belts' discharge conveyors.

[0016] Because the carding machines are designed as airlay machines, a compact and space-saving design can be used. Compared to other carding machines that operate on the random lay or aerodynamic principles, the airlay machine can produce a fiber nap with low basis weights and process fibers with a wide range of lengths.

[0017] The compaction unit can, for example, consist of at least one pair of rollers that compact the fiber nap without altering the structure or orientation of the fibers. The subsequent stretching unit comprises at least an upper and lower stretching arrangement with which the nonwoven fabric can be stretched by a factor of 1.5 to 4. This arrangement can consist of rollers or conveyor belts, each with a smooth surface, or equipped with needles or pins.

[0018] Further flexibility of the system can be achieved by arranging at least one unwinding station in the material transport direction after the drawing unit and before the consolidation unit. This unwinding station is designed to introduce, for example, another carded nonwoven fabric or a layer of paper or tissue into the system below and / or above the nonwoven fabric. This results in a highly flexible system in which various fibers with different fiber lengths and basis weights can be introduced and processed individually or together.

[0019] The subsequent bonding process can be implemented as hydrodynamic bonding or as thermal bonding. Hydrodynamic bonding is a water jet bonding process and features multiple water jets with associated suction systems, which can be operated at pressures of 40 to 400 bar. Using water jet bonding, a single nonwoven fabric or multiple layers of nonwoven fabric can be bonded, joined, and / or structured. By means of a specially designed nozzle arrangement or in combination with an upper structuring belt, which compartmentalizes the web as fiber material and / or the nonwoven fabric, structuring and thus creating a patterned surface of the nonwoven fabric is possible. Alternatively, bonding and structuring can also be carried out on a drum (not shown) with a mounted structuring tray, which is positioned upstream of the dryer.

[0020] After hydrodynamic solidification, a dryer can be arranged in the material transport direction.

[0021] The inventive method for producing a single- or multi-layer nonwoven fabric involves generating at least one fiber nap with an MD / CD ratio of 1.0:1 to 1.2:1 from fibers with a fiber length of 10 to 60 mm and a fiber fineness of 0.5 to 30 dtex using an aerodynamic process. The fiber nap is subsequently compacted, and the resulting nonwoven fabric is stretched by at least a factor of 1.5 and then bonded. The inventive method enables the production of an isotropic nonwoven fabric without a lay-up unit, with high productivity. By stretching the nonwoven fabric, an isotropic nonwoven fabric with virtually any basis weight can be produced at high production speeds. Compared to wet-laid or air-laid processes, the process complexity is significantly lower, and a greater variety of fibers with respect to length, fineness, and grade can be processed.

[0022] By producing at least one additional fiber layer, which is then laid on top of the first and compacted together to form a nonwoven fabric, the productivity of the system can be further increased. Any number of fiber layers can be produced separately, stacked on top of each other, and adjusted to the final weight via stretching. The concept is essentially limited only by the space required when more than four carding machines are used in a line.

[0023] The superimposed fiber filaments all preferably exhibit the same properties as the first fiber filament. However, the invention also provides for the possibility of producing and processing fiber filaments of different fiber qualities together, with both fiber filaments exhibiting approximately the same isotropy.

[0024] The stretching of the fiber pile can be done by a factor of 1.5 to 4, preferably by a factor of 2.

[0025] For example, the fiber pile of each carding machine can have a basis weight of 20 to 400g / m² and be produced at a speed of 15 to 200m / min, preferably having a basis weight of 80g / m² and being produced at a speed of 80m / min.

[0026] The process can be made even more flexible by bonding the drawn nonwoven fabric together with at least one additional nonwoven fabric, which is fed into the system via an unwinding station. This additional nonwoven fabric, which can be, for example, a carded nonwoven or a layer of paper or tissue, can be positioned above and / or below the drawn nonwoven fabric. The drawn nonwoven fabric can then be covered or compartmentalized on one side with a different, preferably lighter, nonwoven fabric, enabling the production of a wide range of products, such as hygiene products.

[0027] The consolidation of the stretched nonwoven fabric, alone or in combination with the nonwoven fabric(s) introduced from the unwinding station(s), can be carried out hydrodynamically or thermally, depending on the fiber type.

[0028] Further measures improving the invention are described in more detail below together with a description of a preferred embodiment of the invention with reference to the figures.

[0029] They show: Fig. 1: shows a first embodiment of the system and method according to the invention; Fig. 2a: shows a detailed view of a first embodiment of a delay device; Fig. 2b: shows a detailed view of a second embodiment of a delay device; Fig. 3: shows a second embodiment of the system and method according to the invention.

[0030] The system 100 according to the invention comprises at least one first carding unit 1, which may be designed as an airlay carding unit. The carding unit 1 is fed via a feeder 2 with fibers or fiber flakes, which may consist of natural or synthetic fibers (cotton, viscose, lyocell, hemp, pulp, polyester, polyamide, polypropylene, polyolefin) or of mixtures of these fibers. Preferably, fibers with a length of 10 to 60 mm and a density of 0.5 to 30 dtex can be processed. The working width of the carding unit 1 can be between 1.5 and 3.8 m. The produced fiber pile 3, which, for example, has a weight of 80 g / m² at a production speed of 80 m / min, is laid down on a first conveyor belt 4, which guides the fiber pile 3 to a compaction unit, which in this embodiment is designed as a pair of rollers 6. The compaction process has the task of densifying the fiber pile without changing the structure in the orientation of the fibers.

[0031] Other aerodynamic methods can also be used to produce a random lay nonwoven fabric, enabling the creation of a fiber nap with high isotropy in a dry process. Airlay carding has the advantage that fibers of varying lengths and types (natural / synthetic fibers) can be processed with high quality across a wide range of properties (nonwoven weight, fiber fineness).

[0032] As an alternative to the roller pair 6, compaction can also be achieved using a roller and a circulating belt, the roller then preferably being designed as a perforated sheet roller. Another alternative for compaction is hydromechanical pre-compaction, which has the advantage that the slightly pre-compacted nonwoven fabric can be drawn more uniformly later.

[0033] If a higher basis weight is required for the final product, the system 100 has at least one additional carding unit 1a, which can also be designed as an airlay carding unit. In this embodiment, the fiber web 3 from the first carding unit 1 is guided by the conveyor belt 4 under the subsequent carding units 1a in the material transport direction and transferred to a further conveyor belt 5. The second carding unit 1a is also fed via a feeder 2a with fibers or fiber flakes, which can be identical to the fibers of the first carding unit 1. However, the fibers can also be different, so that a multi-layered nonwoven fabric with layers of different fibers can be produced. In this embodiment, the produced second fiber web 3a also has a weight of 80 g / m² at a production speed of 80 m / min. The second fiber web 3a is also transferred to the conveyor belt 5, on which the two fiber webs 3 and 3a are brought together.Synchronization of the conveyor belts 4, 5 is not necessary. The subsequent compaction unit, into which two layers of fiber 3, 3a with a total weight of 160 g / m² are fed at 80 m / min, is designed in this embodiment as a pair of rollers and compacts the two layers of fiber 3, 3a without changing the orientation of the fibers, thus forming a nonwoven fabric 24. Since the final product is to have a weight of 40 g / m², a stretching device 10, which can be designed as a nonwoven fabric stretcher, is arranged after the compaction unit.

[0034] In a first embodiment according to the Figure 2aThe pre-drawing device 10 is designed as a nonwoven stretcher, which may have an entry area 11 with two conveyor belts angled relative to each other. The angle of the conveyor belts can be adjusted, as can the speed of each individual conveyor belt. In the conveyor belts, the nonwoven fabric 24 is pre-compressed and its thickness reduced so that it can enter between the upper and lower pre-drawing arrangements 12, 13. Both pre-drawing arrangements 12, 13 consist of a series of rollers that are offset from each other, such that the rollers of the upper pre-drawing arrangement 12 project at least partially into the gusset of the rollers of the lower pre-drawing arrangement 13. At least some of the rollers are driven, with the two pre-drawing arrangements 12, 13 being operated at different roller speeds, so that the nonwoven fabric is stretched between the rollers.The rotational speed of the rollers can increase continuously from the inlet area 11 to the outlet area 14. For this purpose, the rollers preferably have individual drives, so that the stretching along the stretching device is variably adjustable. The mass of the nonwoven fabric 24 in cross-section can be reduced by the speed difference of the rollers from the inlet area 11 to the outlet area 14, so that the nonwoven fabric 24 is stretched essentially uniformly over its entire cross-section. Preferably, the upper stretching arrangement 12 is force- or weight-loaded. Preferably, the distance between the upper stretching arrangement 12 and the lower stretching arrangement 13 can decrease from the inlet area 11 to the outlet area 14. The outlet area 14 of the stretching device 10 can be designed as a conveyor belt adapted to the increased transport speed of the nonwoven fabric.

[0035] Preferably, the surfaces of the rollers of the upper and lower winding arrangement 12, 13 can be smooth or have a set of pins, which prevents shrinkage of the nonwoven fabric. Lateral guides on the winding device 10 prevent the nonwoven fabric 24 from being stretched beyond the desired working width.

[0036] Figure 2bFigure 1 shows a second embodiment of a pre-drawing device 10, which can also have an entry area 11 with two conveyor belts angled relative to each other. The angle of the conveyor belts relative to each other can be adjusted, as can the speed of each individual conveyor belt. In the conveyor belts, the nonwoven fabric 24 is pre-compressed and its thickness reduced so that it can enter between the upper and lower pre-drawing arrangements 12, 13. In this embodiment, the upper and lower pre-drawing arrangements 12, 13 are designed as conveyor belts, with the conveyor belts operating at different speeds, so that the nonwoven fabric is stretched between the conveyor belts by a factor, which can be, for example, 2.The upper and lower drafting arrangements 12, 13 can also be adjusted in angle and / or distance to each other to accommodate different nonwoven thicknesses. Particularly in this embodiment, where the respective speed of the upper and lower drafting arrangements 12, 13 remains constant over the drafting distance, the discharge area 14 is designed as a conveyor belt and can be set to different speed ranges corresponding to the stretching factor. Preferably, the conveyor belts of the drafting arrangement 12, 13 can also be provided with needles on the surface facing the nonwoven 24.

[0037] After the pre-drawing unit, the nonwoven fabric 24, which has been stretched by a factor of 2 in the pre-drawing unit 10, for example, is consolidated with a weight of 40 g / m² at a speed of 160 m / min. This consolidation can take place in the subsequent hydrodynamic consolidation. This consolidation has several water bars 20 in which the fibers are interwoven by means of water jets. A circulating conveyor belt 21 can be arranged below the water bars 20, and a suction unit 22 is located below it. The conveyor belt 21 is perforated to drain the water from the water bars 20. Alternatively, the nonwoven fabric 24 can also be chambered between two conveyor belts and consolidated by means of water jets. In this case, the nonwoven fabric can not only be consolidated but can also be structured and / or perforated.Another alternative to the embodiment shown can be achieved by consolidation on a rotating, internally suctioned drum, in which the nonwoven fabric 24 is also structured and / or perforated in addition to consolidation. Depending on the application, the water bars can be operated with a water pressure of 40–400 bar. After consolidation, the nonwoven fabric 24 is dried in a dryer, which can be designed as a drum or belt dryer, and wound up at a winding station 25.

[0038] An alternative embodiment of Annex 100 is in Figure 3The diagram shows a system in which at least one or two unwinding stations 15 are arranged downstream of the warping unit 10. These stations are designed to feed, for example, a thin layer of synthetic carded nonwoven fabric 15a into the system below and / or above the nonwoven fabric 24, so that the nonwoven fabric 24, made of isotropic fibers, is covered with one or two further layers of carded nonwoven fabric 15a. The layers of thin synthetic carded nonwoven fabric 15a can, for example, have a low basis weight of < 30 g / m². Alternatively, instead of the synthetic carded nonwoven fabric 15a introduced by the unwinding stations 15, a thin nonwoven fabric made of tissue or paper can also be used.

[0039] According to this embodiment, the system is configured to produce a single- or multi-layered nonwoven fabric 24, which can consist solely of the fiber nap 3, 3a of the carding 1, 1a, or of the fiber nap 3, 3a with a lower and / or upper carding nap 15a. This results in material combinations of fibers with different basis weights, varying numbers of fiber layers, and / or one to three layers. The system 100 is configured such that an isotropic nonwoven fabric 24 can be produced with high productivity without a lay-up unit. The MD / CD ratio after bonding is between 1.5:1 and 2.1:1. Reference sign

[0040] 100 plant 1, 1acard 2, 2ariser 3, 3afiber pile 4conveyor belt 5conveyor belt 6rollers 10. Drafting unit 11. Infeed area 12. Upper drafting assembly 13. Lower drafting assembly 14. Outfeed area 15. Unwinding station 15a. Carding fleece 20Wasserbalken 21Transportband 22Absaugung 23Trockner 24Vlies 25Wickelstation

Claims

1. Installation (100) for producing a single-ply or multi-ply nonwoven, comprising - at least one roller card (1), which is configured to produce a fibre web (3) by means of an aerodynamic process, - a first transport belt (4), which is configured to transport the fibre web (3) from the roller card (1) to a compacting device, - wherein the compacting device is configured to compact the fibre web (3) to form a web (24), characterised in that - in the material transport direction there is arranged a downstream drafting device (10) which is configured to draft the web (24) by at least the factor 1.5, - and a bonding device arranged downstream in the material transport direction.

2. Installation according to claim 1, characterised in that the installation (100) has at least one further roller card (1a), which is configured to produce a further fibre web (3a) by means of an aerodynamic process.

3. Installation according to claim 2, characterised in that the transport belt (4) is at least in part arranged underneath the further roller card (3a).

4. Installation according to claim 2, characterised in that upstream of the compacting device there is arranged a transport belt (5) which is configured to receive the fibre webs (3, 3a) layered one above the other.

5. Installation according to claim 1 to 2, characterised in that the roller card (3, 3a) is configured as an airlay roller card.

6. Installation according to claim 1, characterised in that the compacting device is configured as at least one pair of rolls (6) or as a roll with a circulating belt or as a hydromechanical bonding device.

7. Installation according to claim 1, characterised in that the bonding device is configured as a hydrodynamic bonding device or as a thermobonder.

8. Installation according to claim 1, characterised in that the drafting device (10) has at least one upper and lower drafting arrangement (12, 13) which each consist of rolls or transport belts.

9. Installation according to claim 8, characterised in that the drafting arrangement (12, 13) is equipped with needles or clothings.

10. Installation according to claim 7, characterised in that a dryer (23) is arranged downstream of the hydrodynamic bonding device in the material transport direction.

11. Installation according to claim 1, characterised in that downstream of the drafting device (10) and upstream of the bonding device in the material transport direction there is arranged at least one unwinding station (15) which is configured to introduce a web (15a) into the installation (100) below and / or above the web (24).

12. Method for producing a single-ply or multi-ply nonwoven, wherein at least one fibre web (3) having a MD / CD ratio of from 1.0:1 to 1.2:1 is produced from fibres having a fibre length of from 10 to 60 mm and a fibre fineness of from 0.5 to 30 dtex by means of an aerodynamic process, which fibre web is compacted and the resulting web (24) is drafted by at least the factor 1.5 and subsequently bonded.

13. Method according to claim 12, characterised in that at least one second further fibre web (3a) is produced, which is deposited on the first fibre web (3) and, together therewith, compacted to form a web (24), the second further fibre web (3a) having the same properties as the first fibre web (3).

14. Method according to claim 12 or 13, characterised in that the bonding is effected hydrodynamically or thermally.

15. Method according to claim 14, characterised in that the hydrodynamic bonding is effected by means of water jets at from 40 to 400 bar.

16. Method according to claim 15, characterised in that after the bonding the nonwoven (24) has a MD / CD ratio between 1.5:1 and 2.1:1.

17. Method according to claim 12, characterised in that the fibre web (3) has a basis weight of from 20 to 400 g / m2 and is produced at a speed of from 15 to 200 m / min, and preferably has a basis weight of 80 g / m2 and is produced at a speed of 80 m / min.

18. Method according to claim 12, characterised in that the drafting is effected by the factor 1.5 to 4, preferably by the factor 2.

19. Method according to any one of claims 12 to 18, characterised in that the drafted web (24) is bonded together with at least one further web (15a), the web (15a) being arranged below and / or above the web (24).

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