PLANT AND METHOD FOR THE PRODUCTION OF A SINGLE- OR MULTI-LAYER NON-WOVEN FABRIC

Description

[0001] The invention relates to a method for producing a multilayer nonwoven fabric, as well as a nonwoven fabric produced according to this method.

[0002] It is known from EP 1929080 B1 to bond loose fibers to a nonwoven fabric in which the loose fibers are always supported and guided from below by a belt and simultaneously laid onto a nonwoven fabric. This process and the associated equipment are very complex, as absolutely parallel guidance of the belts over a long section is required. This is very difficult to implement from a design perspective, since constant tension is required between the belts and both belts must have the same speed at every point to prevent uncontrolled distortions in the final product.

[0003] DE 102015112955 A1 solves the above-mentioned problem by laying the layer of loose fibers on a nonwoven fabric.

[0004] EP 3118361 A1 discloses a carding plant which is arranged in the material transport direction upstream of the plant for the production of wet-laid fibers.

[0005] WO2013 / 067557 A1 and EP 3550062 A1 disclose the production of a wet-laid fibrous material from pulp containing solvent-spun cellulose fibers.

[0006] US Patent 2013 / 0157537 discloses a layer of wet-laid pulp fibers bonded to a nonwoven fabric of regenerated cellulose fibers using water jets. The nonwoven fabric is placed beneath the layer of wet-laid pulp fibers in the system, resulting in a high degree of fiber release from the top of the pulp fibers during water jet bonding.

[0007] DE 102016217401 A1 discloses an inclined screen former from which a web of wet-laid fibrous material is transferred upside down onto a circulating belt by means of a transfer screen. A further nonwoven fabric can be introduced from a feeding device under the web of wet-laid fibrous material onto the circulating belt.

[0008] Wetlaid products often have insufficient tensile strength, limiting their use in hygiene products. A combination of high liquid absorption and increased tensile strength is desirable and expands their range of applications.

[0009] The object of the present invention is to provide a method for producing a multilayer nonwoven fabric by which wet-laid fibers can be processed together with at least one carded nonwoven fabric to form a high-strength nonwoven. Furthermore, it is an object of the invention to produce a nonwoven fabric from a wet-laid fiber material with high strength and simultaneously good liquid absorption.

[0010] The invention solves the stated problem by means of the teachings according to claims 1 and 3; further advantageous embodiments of the invention are characterized by the dependent claims.

[0011] The inventive method for producing a multilayer nonwoven fabric involves laying a web of wet-laid fiber and / or a nonwoven and / or a carded nonwoven on a circulating belt and subjecting this, in combination with one of the aforementioned webs of fiber or nonwovens, as a two- to three-layer nonwoven to water jet bonding for bonding and / or bonding and / or structuring, and subsequently drying. The laying of the web of fiber and its possible combination with another carded nonwoven is designed in such a way that no distortion is exerted on the individual web or on the multilayer web. This requires a higher strength of the fiber, which is achieved by combining or mixing the wet-laid fiber, which usually consists of pulp, with a proportion of 30 wt.% to 5 wt.% solvent-spun cellulose fibers, for example with lyocell.The combination of wet-laid pulp fibers with solvent-spun cellulose fibers, for example from lyocell, increases the wet strength of the fiber by over 60%, because, surprisingly, the fibrils of the solvent-spun cellulose fibers form a strong bond with the short pulp fibers. The increased wet strength of the fiber allows for further processing in the plant without chambering the fiber or passing it through a second belt. In contrast to prior art material combinations, solvent-spun cellulose fibers, as short-cut fibers, can also have a shorter fiber length than is typically used. The average fiber length of 8 to 12 mm for solvent-spun cellulose fibers at a titer of 1.2 to 1.8 dtex has proven ideal for use in a wet-laid process.Due to the high bonding capacity of the solvent-spun cellulose fibers with the pulp, the pulp load on the filtration system is reduced, thus increasing the efficiency of the system and the process. The process according to the invention has the advantage that very lightweight fiber materials, for example 25 g / m² and less, can be produced, which exhibit high strength and can therefore be transferred from one conveyor belt to the next without damage.

[0012] Water jet bonding is designed to bond, join, and / or structure multiple layers of fibers or multiple nonwovens. Preferably, the water jets of the bonding process are designed to spray water onto the fiber web at a pressure of 40 to 400 bar. Using a specially designed nozzle arrangement or in combination with an upper structuring band that compartmentalizes the fiber web, structuring and thus creating a patterned surface on the nonwoven is possible. Alternatively, bonding and structuring can also be carried out on a drum (not shown) with a structuring tray mounted on it, which is positioned upstream of the dryer.

[0013] This results in a highly flexible system in which various fibers with different fiber lengths and basis weights can be fed in and processed individually or together. The arrangement of an inclined screen former and a carding unit positioned downstream in the material transport direction is space-saving and, due to the conveyor belt running beneath the carding unit, easy and inexpensive to implement. Part of the conveyor belt can, for example, be installed under a covered, subfloor section.

[0014] The nonwoven fabric according to the invention comprises a wet-laid fiber material consisting of 70 wt.% to 95 wt.% pulp and 30 wt.% to 5 wt.% solvent-spun cellulose fibers, for example, lyocell. The combination of the wet-laid pulp fibers with the solvent-spun cellulose fibers increases the wet strength of the nonwoven fabric by over 60%, since, surprisingly, the fibrils of the solvent-spun cellulose fibers form a strong bond with the short pulp fibers. The water absorption capacity of the solvent-spun cellulose fibers creates an ideal combination with the pulp, enabling high liquid absorption when used as a middle or bottom layer in hygiene products or diapers. In contrast to prior art material combinations, the solvent-spun cellulose fibers also have a shorter fiber length than is typically used.The average fiber length of solvent-spun cellulose fibers, such as Lyocell, of 8 to 12 mm at a titer of 1.3 to 1.8 dtex has proven ideal for use in a wet-laid process. The high binding capacity of the solvent-spun cellulose fibers with the pulp reduces the pulp load on the filtration system, thus increasing the efficiency of the system and the process.

[0015] In this process, the wet-laid fiber is bonded to one or two layers of another nonwoven fabric, which act as cover layers around the wet-laid fiber. At least one of these nonwovens is a carded nonwoven fabric consisting of 100 wt.% solvent-spun cellulose fibers, or 100 wt.% viscose, or 100 wt.% a mixture of solvent-spun cellulose fibers and viscose. The second nonwoven fabric also consists of 100 wt.% solvent-spun cellulose fibers, or 100 wt.% viscose, or 100 wt.% a mixture of solvent-spun cellulose fibers and viscose. The solvent-spun cellulose fibers preferably have an average fiber length of 38 - 40 mm with a titer of 1.2 - 1.8 dtex, which distinguishes them from the solvent-spun cellulose fibers used in the wetlaid process.The viscose fibers also preferably have an average fiber length of 38–40 mm with a density of 1.2–1.8 dtex. A further advantage of combining the previously described fiber material 9 with a carded nonwoven fabric 15a made of solvent-spun cellulose fibers lies in the complete biodegradability of the resulting hygiene product. Depending on the availability and global market price of viscose and / or lyocell, Tencel, Cocel, etc., with similar properties, the plant operator can optimize costs by producing nonwoven fabrics, which serve as the cover layer for the fiber material, consisting solely of solvent-spun cellulose fibers, solely of viscose, or of a mixture of both.

[0016] 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.

[0017] They show: Fig. 1 shows a first embodiment of the system and the method according to the invention; Fig. 2 shows a second embodiment of the system and the method according to the invention.

[0018] The system 100 comprises at least one inclined screen former 1, at least one device downstream in the transport direction of the web for introducing a further web of material, at least one water jet compaction unit arranged downstream with at least one water bar 16 and a dryer 18.

[0019] An inclined screen former 1 is arranged below a circulating screen belt 10. The screen belt 10, which can be designed as an endless belt, runs around various rollers 12 and has an inclined section 11 that rises at an angle in the direction of travel of the screen belt. In the region of the inclined section 11, the inclined screen former 1 is arranged below the screen belt 10, and the screen belt 10 rests on its surface 2. Below the surface 2, at least one suction zone 3 is arranged, which is pressurized by means of pumps (not shown). The inclined screen former 1 can have several suction zones 3, which are subjected to different pressures or vacuums. The vacuum sources can preferably be designed as controllable vacuum pumps.

[0020] In this embodiment, at least one fiber suspension is fed onto the wire belt 10 via a headbox 8. Besides water, the fiber suspension contains a specific amount of solids, which in turn consists of fibers and other additives. When multiple fiber suspensions are present, lamellae (not shown) are arranged between them, allowing the layer thickness of the fiber suspensions to be varied individually or collectively. Since the lamellae separate the fiber suspensions from one another, they are dewatered sequentially on the inclined wire former 1. This prevents the fiber suspensions from mixing and improves the purity of the individual layers of fiber. Each layer of a fiber suspension can be subjected to a separate vacuum via the at least one suction zone in conjunction with the controllable vacuum pumps, thus enabling the processing of different water-fiber mixtures in each fiber suspension.

[0021] In this embodiment, the fiber suspension consists of pulp with a lyocell content of 5 wt.% to 30 wt.%. The pulp has an average fiber length of 1–3 mm with a density of 1.1–1.8 dtex. The lyocell has an average fiber length of 8–12 mm with a density of 1.2–1.8 dtex. Compared to the prior art, the tensile strength of the fiber 9 can be increased by adding lyocell. A further advantage is the reduced pulp load on the filtration process. Surprisingly, this is due less to the reduction of the pulp content at the same basis weight, but rather to the bonding effect between the lyocell fibers and the pulp. Unlike viscose fibers, lyocell fibers have fibrils that bind and hold the short pulp fibers in the aqueous solution.

[0022] In a test, the tensile strength of 100 wt% pulp with a basis weight of 25 g / m² in the transverse direction (CD) was 12 N / 5 cm. All strength values ​​given here refer to a test according to EDANA WSP 110.4 (09). With a fiber blend of 90 wt% pulp and 10 wt% lyocell, the strength increased on average to 14 N / 5 cm, and to a maximum of up to 16 N / 5 cm. With a fiber blend of 80 wt% pulp and 20 wt% lyocell, the strength increased on average to 18 N / 5 cm, and to a maximum of up to 20 N / 5 cm. The increase in the blend is advantageously limited to 70 wt% pulp with 30 wt% lyocell, as the fiber then no longer has the necessary liquid absorption capacity required for use as a diaper liner or hygiene product. The basis weight of the dry web made of fibrous material 9 can preferably be 10 to 60 g / m².Instead of lyocell, another solvent-spun cellulose fiber, such as Tencel, can also be used.

[0023] The conveyor belt 10, which is permeable to liquids and gases, transports the fiber suspension over the inclined section 11 and across the inclined screen former 1. Due to gravity and the negative pressure acting on the fiber suspension, the suspension is dewatered, resulting in a web of fibrous material 9 with a single layer of fibers. Below the suction zone 3, the screen water 6 is collected in a screen box 5 and drawn off. The web of fibrous material 9 is transported along the belt 10, first over a horizontal section and then over an inclined section, in the direction of the arrow. After the inclined section, the web of fibrous material 9 is transferred, underside down, onto another circulating belt 13, which runs as an endless belt around at least two rollers 14.

[0024] In the transport direction of the fiber material 9, in the first embodiment the Figure 1 A carding unit 15 is arranged in the system 100. The carding unit 15 is positioned spatially above the belt 13, so that the wet-laid web of fiber material 9 can be guided independently of the carding unit 15 to a water jet compaction unit with at least one water bar 16 and a suction unit 17 located below the belt 13. In other words, the belt 13 is guided below the stationary carding unit 15 and is designed to direct the web of fiber material 9 directly from the inclined screen former to the water jet compaction unit. There, the fiber material 9 is compacted, dried in the dryer 18, and optionally wound up in a winding station 20.

[0025] The carding unit 15 can feed a carded web of fibers, a carded nonwoven 15a, into the system 100. This occurs before water jet bonding, so that the web of fiber material 9 is bonded to the carded nonwoven 15a by means of the water bars 16. The web of fiber material 9 can be bonded to a top layer of carded nonwoven 15a to form a multi-layered nonwoven 19 by water jet bonding and dried in the dryer 18 and optionally wound up in a winding station. Typically, the carded nonwoven 15a can consist of, for example, polyester, viscose, a cotton blend, or a mixture of synthetic and / or natural fibers. Preferably, the basis weight of the carded nonwoven 15a is between 20 g / m² and 60 g / m².

[0026] Advantageously, the carded nonwoven fabric consists of 100 wt.% viscose, or of 100 wt.% solvent-spun cellulose fiber, for example, Lyocell or Tencel, or of a 100 wt.% blend of both fibers. The advantage of these materials as a top layer for the fiber 9 lies in their high absorbency and soft feel (soft denim) when used as a hygiene product. A further advantage of combining the previously described fiber 9 with a carded nonwoven fabric 15a made of solvent-spun cellulose fibers is the complete biodegradability of the resulting hygiene product. Depending on the availability and global market price of viscose and / or Lyocell, Tencel, etc., the plant operator can optimize costs with similar properties by using a carded nonwoven fabric 15a consisting solely of solvent-spun cellulose fibers, solely of viscose, or of a blend of both.The lyocell fibers used here preferably have an average fiber length of 38–40 mm and a density of 1.2–1.8 dtex. The viscose fibers also preferably have an average fiber length of 38–40 mm and a density of 1.2–1.8 dtex.

[0027] The carded fleece preferably has a basis weight of 20g / m 2<, so that the consolidated and dried fleece 19 has a basis weight of preferably 45g / m 2<.

[0028] According to this embodiment, the system is configured to process either the web of fiber material 9 or the carded nonwoven fabric 15a, or the web of fiber material 9 together with the carded nonwoven fabric 15a. Preferably, a two-layer nonwoven fabric with a weight of 45 g / m² is produced, in which the fiber web layer 9 consists of 70 wt.% - 95 wt.% pulp and 30 wt.% - 5 wt.% solvent-spun cellulose fibers. The second layer of carded nonwoven fabric 15a can consist of 100 wt.% solvent-spun cellulose fibers, 100 wt.% viscose, or 100 wt.% of a mixture of solvent-spun cellulose fibers and viscose.

[0029] In the exemplary embodiment of the Figure 2 is in comparison to the embodiment of the Figure 1Additionally, an unwinding station 24 with a roller 23 is arranged in the transport direction of the web of fibrous material 9 in front of the belt 13. The unwinding station 24 can be arranged in front of the inclined screen former 1 or below (underfloor) it and can feed a web of fibers as a nonwoven 24a into the system 100 as an alternative or supplement to the carded nonwoven 15a. Instead of the unwinding station 24, another carding unit can also be arranged in front of the inclined screen former 1, the carded nonwoven from which is fed into the system 100 below the inclined screen former 1.

[0030] Contrary to the schematic representation of the arrangement of the unwinding station 24 and the direction of travel of the belt 10 in the Figure 2In this embodiment, the unwinding station 24 is arranged such that the nonwoven fabric 24a is laid onto the web 13 between the lay-up of the fiber web 9 and the roller 14. This allows for a three-layer nonwoven fabric 19, with the nonwoven fabric 24a and the carding nonwoven fabric 15a forming the top layers for the fiber web 9. Preferably, the carding nonwoven fabric 24a also consists of 100 wt.% viscose, or of 100 wt.% solvent-spun cellulose fibers, or of a 100 wt.% mixture of both fibers. The solvent-spun cellulose fibers preferably have an average fiber length of 38–40 mm with a density of 1.2–1.8 dtex. The viscose fibers also preferably have an average fiber length of 38 - 40 mm with a titer of 1.2 - 1.8 dtex.

[0031] The carded nonwoven fabric preferably has a basis weight of 20g / m 2<, so that the consolidated and dried three-layer nonwoven fabric 19 has a basis weight of preferably 65g / m 2<.

[0032] If the nonwoven fabric 24a is fed into the system 100 as an alternative to the web made of fibrous material 9, a nonwoven fabric made of tissue or paper can also be used. Preferably, the basis weight of the nonwoven fabric 24a is then between 10 g / m² and 60 g / m².

[0033] According to this exemplary embodiment of the Figure 2 The system is designed to produce a two- or three-layer nonwoven fabric 19, which can consist of a web of fibrous material 9 with a carded nonwoven fabric 15a on the top side and, optionally, a carded nonwoven fabric 24a on the bottom side. The system 100 is configured such that there is no overlap or parallel running of belts between which distortion of the nonwoven fabric is possible due to speed differences. Reference sign

[0034] 100 plant 1 Inclined screen former 2 Lining 3 Suction zone 5 Suction box 6 Screen water 8 Headbox 9 Fiber 10 Screen belt 11 Inclined section 12 Roller 13 Belt 14 Roller 15 Carding 15a Carding fleece 16 Water bar 17 Extraction 18 Dryer 19 Fleece 23Roller 24Unwinding station 24aFleece

Claims

1. Method for producing a two-ply or three-ply nonwoven (19), in which a sheet of wet-laid fibre material (9) is produced in an inclined wire former (1) and which is supplied together with a roller card web (15a), which is produced by a roller card (15) arranged downstream in material transport direction, and / or a web (24a), which is introduced into the installation upstream or downstream of the inclined wire former (1) via an unwinding station (24) or a further roller card, in the form of a two- to three-ply nonwoven (19) to a hydroentanglement for bonding and / or entangling and / or structuring and is subsequently dried, wherein the sheet of wet-laid fibre material (9) is transported by means of a belt (13), which is guided below the stationary roller card (15) and is designed to guide the sheet of fibre material (9) directly from the inclined wire former (1) to the hydroentanglement, wherein the fibre material (9) consists of from 70% by weight to 95% by weight pulp and from 30% by weight to 5% by weight solvent-spun cellulose fibres, preferably of 80% by weight pulp and 20% by weight solvent-spun cellulose fibres, particularly preferably of 90% by weight pulp and 10% by weight solvent-spun cellulose fibres, characterized in that the roller card web (15a) and the web (24a) consists of 100% by weight solvent-spun cellulose fibres, or 100% by weight viscose, or 100% by weight of a mixture of solvent-spun cellulose fibres and viscose.

2. Method according to any one of claims 1, characterised in that the hydroentanglement is configured to entangle, bond and / or structure the fibre material (9) with one or both webs (15a, 24a) at a pressure of from 40 bar to 400 bar.

3. Nonwoven, produced according to a method according to claim 1 or 2, comprising a wet-laid fibre material (9) of from 70% by weight to 95% by weight pulp and from 30% by weight to 5% by weight solvent-spun cellulose fibres, characterised in that the wet-laid fibre material (9) is bonded with at least one cover layer of 100% by weight solvent-spun cellulose fibres, or of 100% by weight viscose, or of 100% by weight of a mixture of solvent-spun cellulose fibres and viscose.

4. Nonwoven according to claim 3, characterised in that the wet-laid fibre material (9) consists of 80% by weight pulp and 20% by weight solvent-spun cellulose fibres and has a strength of at least 18 N / 5 cm in the cross-machine direction (CD).

5. Nonwoven according to one of claims 3 to 4, characterised in that the wet-laid fibre material (9) consists of 90% by weight pulp and 10% by weight solvent-spun cellulose fibres and has a strength of at least 16 N / 5 cm in the cross-machine direction (CD).

6. Nonwoven according to any one of claims 3 to 5, characterised in that the pulp has an average fibre length of from 1 to 3 mm with a titre of from 1.1 to 1.8 dtex.

7. Nonwoven according to any one of claims 3 to 5, characterised in that the solvent-spun cellulose fibres have an average fibre length of from 8 to 12 mm with a titre of from 1.2 to 1.8 dtex.

8. Nonwoven according to claim 3, characterised in that the fibres of solvent-spun cellulose fibres or viscose have an average fibre length of from 38 to 40 mm with a titre of from 1.2 to 1.8 dtex.

9. Nonwoven according to claim 8, characterised in that the cover layer or cover layers is / are in the form of a roller card web (15a) and / or web (24a).