METHOD AND SYSTEM FOR PRODUCING A WET-LAID NON-WOVEN FABRIC WEB

Abstract

A method for producing a wet-laid non-woven fabric web includes: providing a first suspension with natural pulp fibers in a first tank, providing a second suspension with regenerated cellulose fibers in a second tank, combining the first suspension and the second suspension to create a mixture, feeding the mixture to a headbox and dewatering the mixture in the forming section of a machine for producing the wet-laid non-woven fabric web. The second suspension with the regenerated cellulose fibers is conveyed by a volumetric pump, in particular by an eccentric screw pump, from the second tank into the volume flow of the first suspension. Wherein over the entire conveying path between the second tank and the headbox, the second suspension is not conducted through any mixing chest having a stirrer. Furthermore, a corresponding system for carrying out the method is taught.

Claims

1. A method for producing a wet-laid nonwoven web, which comprises the following steps of: providing a first suspension containing natural pulp fibers in a first tank; providing a second suspension containing regenerated cellulose fibers in a second tank; combining the first suspension and the second suspension to generate a mixture by conveying the second suspension containing the regenerated cellulose fibers from the second tank by means of a volumetric pump into a volume stream of the first suspension, with the second suspension not being passed through any mixing chest having a stirring mechanism over an entire conveying path between the second tank and a headbox; supplying the mixture to the headbox; and dewatering the mixture in a forming section of a machine for producing the wet-laid nonwoven web.

2. The method according to claim 1, which further comprises conveying the first suspension containing the natural pulp fibers from the first tank by means of a further volumetric pump into a volume stream of the second suspension, with the first suspension not being passed through any said mixing chest containing the stirring mechanism over an entire conveying path between the first tank and the headbox.

3. The method according to claim 1, wherein the first suspension is one of a plurality of first suspensions containing the natural pulp fibers disposed in a plurality of first tanks.

4. The method according to claim 3, which further comprises mixing the plurality of first suspensions with one another in at least one mixing chest containing a stirring mechanism before they are conveyed further into a volume stream of the second suspension.

5. The method according to claim 1, wherein the regenerated cellulose fibers contain viscose and/or lyocell.

6. The method according to claim 1, wherein the wet-laid nonwoven web undergoes waterjet needling in the machine for producing the wet-laid nonwoven web.

7. The method according to claim 6, wherein a production operation is configured such that a completed said wet-laid nonwoven web is dispersible in water.

8. The method according to claim 1, wherein all fibers and any further auxiliaries from which the wet-laid nonwoven web is formed are selected such that the wet-laid nonwoven web is biodegradable.

9. The method according to claim 1, wherein the volumetric pump is an eccentric screw pump.

10. The method according to claim 2, wherein the further volumetric pump is an eccentric screw pump.

11. The method according to claim 3, wherein the natural pulp fibers in the first suspensions differ from one another.

12. A facility for producing a wet-laid nonwoven web, the facility comprising: a first tank for a first suspension containing natural pulp fibers; a second tank for a second suspension containing regenerated cellulose fibers; a volumetric pump conveying the second suspension containing the regenerated cellulose fibers from said second tank into a volume stream of the first suspension at a combining point for combining the first suspension and the second suspension to generate a mixture; a headbox being supplied with the mixture, the facility being free from a mixing chest containing a stirring mechanism over an entire conveying path for the second suspension from said second tank up to said headbox; and a forming section for dewatering the mixture.

13. The facility according to claim 12, further comprising a waterjet needling apparatus for needling the wet-laid nonwoven web.

14. The facility according to claim 12, wherein said volumetric pump is an eccentric screw pump.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0023] FIG. 1 is a block diagram of a conventional facility for producing a wet-laid nonwoven web in accordance with the prior art,

[0024] FIG. 2 is a block diagram of a first embodiment of a facility of the invention for producing the wet-laid nonwoven web; and

[0025] FIG. 3 is a block diagram of a second embodiment of the facility of the invention for producing the wet-laid nonwoven web.

DETAILED DESCRIPTION OF THE INVENTION

[0026] Referring now to the figures of the drawings in detail and first, particularly to FIG. 1 thereof, there is shown a prior art facility 10 for producing a wet-laid nonwoven web, where here only the front part up to the a headbox 12 is represented. For possible configurations of the back part of the facility, up to the rolling function, reference is made, for example, to the observations in the international patent publication WO 2015/000687 A1, which originates from the instant applicant. In this example, only two kinds of fibers are mixed: natural pulp fibers, which are provided in the form of an aqueous suspension in a first tank 14, and regenerated cellulose fibers, which are provided likewise in the form of an aqueous suspension in a second tank 16. The two aqueous suspensions are each pumped by means of a conventional rotary or centrifugal pump 18 to a first mixing chest 20 having a stirrer 22. There, the two suspensions, containing the natural pulp fibers and the regenerated cellulose fibers, are mixed with one another for the first time. In general, the first mixing chest 20 is followed by further mixing chests 20 with corresponding stirrers 22 for example, as shown in FIG. 1, by a second mixing chest 20 and by a third and final mixing chest 20, which is also referred to as the machine chest. Water may be added as early as in the chests 20, to reduce the fiber concentration in the suspension mixture. After the final mixing chest 20, the mixture may be guided alternatively past or into a preliminary dilution tank 24. The primary contents of the preliminary dilution tank 24 are further water. Subsequently, the mixture may be guided again alternatively past or into a white water tank 26. In the former case, the mixture may be added to the water from the white water tank 26, either upstream or downstream of a pump 18. The white water tank 26 additionally receives the so-called white water from the forming section, this being the water which has passed through a forming wire and is pumped back in the process circuit. Finally, the fiber suspension mixture, heavily diluted with the water from the preliminary dilution tank 24 and from the white water tank 26, reaches the headbox 12, from where it is applied to a forming wire, in a forming section no longer shown here, and is dewatered there, in order to form the actual nonwoven web. This takes place preferably in an inclined-wire former.

[0027] With this facility, the problem may occur that the long-regenerated cellulose fibers may become spun in the rotary or centrifugal pump 18 with which they are pumped out of the second tank 16, and/or at the stirrer 22 of one of the mixing chests 20. This then leads to costly and inconvenient cleaning and gives rise to corresponding production downtimes or outages.

[0028] FIG. 2 shows a schematic representation of a front part of the facility 10 for producing a wet-laid nonwoven web, analogous to FIG. 1, but this time of a first embodiment according to the invention. In FIG. 2, the same components have the same reference signs as in FIG. 1, but without a prime. Accordingly, with regard to these components, reference is made to the observations above in relation to FIG. 1.

[0029] Differently than in FIG. 1, the facility 10 represented in FIG. 2 has no mixing chests 20 with stirrers 22. Moreover, the rotary or centrifugal pumps 18 which pump the suspension from the first tank 14 and the second tank 16, respectively, were each replaced by a volumetric pump 28, and, to be more precise, by an eccentric screw pump 28. The first suspension containing the natural pulp fibers from the first tank 14 is jetted directly into the conduit which connects the preliminary dilution tank 24 to the white water tank 26, for example upstream of the rotary or centrifugal pump 18 disposed between them. The second suspension containing the regenerated fibers from the second tank 16 is jetted alternatively likewise into the conduit which connects the preliminary dilution tank 24 to the white water tank 26, and/or into the conduit which connects the white water tank 26 to the headbox 12. This jetting may take place either upstream and/or downstream of a respective rotary or centrifugal pump 18. As a result of the extremely high dilution of the suspension mixture with the water from the preliminary dilution tank 24 and/or white water tank 26, the risk here of the regenerated fibers becoming spun is no more than low.

[0030] In the volumetric pump 28, provided in accordance with the invention downstream of the second tank, there is likewise virtually no risk of the long regenerated fibers becoming spun, just as there is no longer any risk at the stirrers 22 of the mixing chests 20, which in accordance with the invention are done away with entirely in the conveying path of the second suspension from the second tank 16 up to the headbox 12.

[0031] Given that with this embodiment there are no mixing chests 20 with stirrers 22, a positive side effect possiblerelative to the embodiment from FIG. 1 according to the prior artis that of economizing on construction space and costs, including, in particular, costs for the power to drive the stirrers 22.

[0032] FIG. 3 shows a schematic representation of a front part of a facility for producing a wet-laid nonwoven web, analogous to FIGS. 1 and 2, but this time of a second embodiment according to the invention. In FIG. 3, the same components have the same reference signs as in FIG. 1, but without a prime, and/or the same reference signs as in FIG. 2. Accordingly, with regard to these components, reference is made to the observations above in relation to FIGS. 1 and 2.

[0033] Differently than in the first embodiment according to FIG. 2, the second embodiment according to FIG. 3 contains two first tanks 14. Each of the two first tanks 14 is filled with a first suspension containing natural pulp fibers, although the pulp fibers in the two tanks 14 differ from one another. For example, one tank 14 may contain natural pulp fibers of shorter fiber length than the other tank 14.

[0034] The first suspensions of both first tanks 14 may be mixed via multiple mixing chests 20 with stirrers 22 substantially in the same way as described above in FIG. 1 with respect to the first suspension and the second suspension. The two first suspensions here may also be pumped from the two first tanks 14 by means of a respective rotary or centrifugal pump 18. For the fibers composed of natural pulp, which are consistently very short by comparison with the regenerated fibers, there is no risk here of them becoming spun. After that, the mixture of the two first suspensions may be guided alternatively into the preliminary dilution tank 24 and/or past it into the connecting conduit between the preliminary dilution tank 24 and the white water tank 26.

[0035] It is important for this embodiment that here as well in accordance with the invention, as in the case of the first embodiment according to FIG. 2, the second suspension comprising the regenerated cellulose fibers is conveyed from the second tank 16 into the volume stream of the first suspension by means of a volumetric pump 28, more particularly by means of an eccentric screw pump, with the second suspension not being passed through any mixing chest 20 containing a stirring mechanism 22 over the entire conveying path between the second tank 16 and the headbox 12. This reduces the risk of the regenerated fibers becoming spun in the facility 10. The second suspension from the second tank 16 may be routed here in the manner described above in the first exemplary embodiment with regard to FIG. 2.

[0036] The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention: [0037] 10, 10 facility for producing a wet-laid nonwoven web [0038] 12, 12 headbox [0039] 14, 14 first tank [0040] 16, 16 second tank [0041] 18, 18 rotary or centrifugal pump [0042] 20, 20 mixing chest [0043] 22, 22 stirrer [0044] 24, 24 preliminary dilution tank [0045] 26, 26 white water tank [0046] 28 volumetric pump (eccentric screw pump)