Patent Application
20240240402
The present invention relates to producing a web of fibrous material in a paper machine.
Devices and methods for producing a fibrous material web are known. Document WO2019/137667 A1 describes a method and a device for producing a fibrous mat. The fibrous mat is produced in a dry-laid process. At the end of the low-water formation of the fibers, a press nip, through which the fibrous mat is passed for only a short time, is provided for the consolidation of the fibrous mat. The press nip is formed by support elements. To heat the fibrous mat, the support elements can be heated directly or indirectly.
The known devices are not suitable for high machine speeds and high mechanical strength of the fibrous material web.
It is therefore the objective of the current invention to cite a device and a method for producing a fibrous material web at a high production rate and at the same time, one having high mechanical strength and quality.
The present invention relates to a method for producing a fibrous material web, including the following steps: (a) low-water processing of cellulose-containing fibers into individual fibers and/or fiber bundles; (b) forming of individual fibers and/or fiber bundles in the air stream into a planar laid fibrous structure using a dry forming method; (c) moistening of individual fibers and/or fiber bundles by way of a fluid, in particular water; (d) solidifying the planar laid fibrous structure by applying pressure in a press nip. The present invention also relates to a machine to produce a fibrous material web.
The present invention provides a method for the production of a fibrous material web, including the following steps: (a) low-water processing of cellulose-containing fibers into individual fibers and/or fiber bundles; (b) forming of individual fibers and/or fiber bundles in the air stream into a planar laid fibrous structure using a dry forming method; (c) moistening of individual fibers and/or fiber bundles by way of a fluid, in particular water; (d) solidifying the planar laid fibrous structure by applying pressure in a press nip. According to the present invention it is further provided that (e) the individual fibers and/or the fiber bundles are subjected to a heating step e) upstream from the solidification step to increase the temperature of the individual fibers and/or of the fiber bundles in the solidification step.
This solution offers the advantage of gently increasing the temperature of the individual fibers and/or the fiber bundles prior to solidification. If necessary, heat can still be added in the solidification nip without impairing the quality of the fibrous material web. This permits the machine speed to be further increased without burning or singeing the fibers of the fibrous material web. In addition, the effect of the temperature increase, and the compression pressure in the solidification nip can be decoupled. This allows for an additional positive influence on the quality of the fibrous material web.
Heating step e) can be carried out advantageously by infrared heating elements and/or by a steam blow box and/or by hot air and/or by heated contact surfaces, such as for example a revolving screen or a roll. In the event that steam is used, the steam condensate can also partially or completely replace the fluid used to moisten the laid fibrous structure. If a roll, in particular a heated roll, is used, said roll optionally does not apply pressure upon the laid fibrous structure.
If infrared heating elements are used in heating step e), they will advantageously not exert any pressure upon the fibers and/or the laid fibrous structure, and, moreover, advantageously no direct air currents are directed onto the freshly deposited fibers which are not yet solidified, and which could lead to the fibers being blown away.
In a possible further embodiment, the infrared heating elements are electrically heated or supplied with electricity. The electric heating of the infrared heating elements allows for improved temperature control in the fibers and/or the laid fibrous structure, and further reduces the risk of igniting whirling dry fibers.
Heating step e) is advantageously carried out in the range of greater than or equal to 30° C., optionally greater than or equal to 45° C., and less than or equal to 100° C., optionally less than or equal to 95° C. This has a particularly advantageous effect on moistening step c), as the applied medium adheres particularly well to the deposited fibers or remains adhered to them, and wherein the laid fibrous structure is provided with increased strength.
In another possible design, heating step e) can be carried out by the preheated fluid in moistening step c). For gentle heating, this can occur in addition to other heating steps.
In addition, it is also possible if heating step (e) is carried out by introducing steam before or during forming step (b), in particular into the air-fiber/fiber bundle stream. In this case, the resulting steam condensate can also partially or completely replace the fluid used to moisten the laid fibrous structure. At the same time, the humidity in the air-fiber/fiber bundle stream is increased and electrostatic charge is counteracted. This improves the formation of the laid fibrous structure.
The present invention also provides a machine for the production of a fibrous material web, in particular for the execution of the described method, with (a) a device for low-water processing of cellulose-containing fibers into individual fibers and/or fiber bundles; (b) a dry forming unit for forming individual fibers and/or fiber bundles in an air stream into a planar laid fibrous structure using a dry forming method; (c) a moistening unit for moistening of individual fibers and/or fiber bundles by way of a fluid, in particular water; (d) a press nip to solidify the planar laid fibrous structure by applying pressure.
The machine according to the present invention is characterized in that the machine includes a heating device upstream from the press nip to increase the temperature of the individual fibers and/or the fiber bundles in the press nip.
In one advantageous design, the heating device includes an infrared heating element and/or a steam blow box and/or heated contact surfaces, such as for example a revolving screen or a roll.
It is also advantageous if the heating device is operatively connected with the moistening unit for heating the fluid. The heating device may for example, be a heat exchanger.
The individual fibers and/or fiber bundles or the laid fibrous structure can also be heated by the heating device being operatively connected with the device for low-water processing and/or with the dry forming unit. This means that a heat flow is generated that heats the individual fibers and/or fiber bundles or the laid fibrous structure.
The present invention also expressly extends to such embodiments which are not given by combinations of features from explicit references in the claims, whereby the disclosed features of the present invention can be combined with one another as desired, insofar as this is technically meaningful.
Additional features and advantages of the invention result from the following description of an optional design example with reference to the drawing.
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawing, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one embodiment of the invention, and such exemplification is not to be construed as limiting the scope of the invention in any manner.
While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 125 451.5 | Sep 2021 | DE | national |
This is a continuation of PCT application no. PCT/EP2022/074148, entitled “METHOD AND MACHINE FOR PRODUCING A FIBROUS MATERIAL WEB IN A PAPER MACHINE”, filed Aug. 31, 2022, which is incorporated herein by reference. PCT application no. PCT/EP2022/074148 claims priority to German patent application no. 10 2021 125 451.5, filed Sep. 30, 2021, which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2022/074148 | Aug 2022 | WO |
| Child | 18618877 | US |
