Paper making and fiber liberation – Processes and products – Non-fiber additive
Reexamination Certificate
2000-01-28
2002-04-23
Silverman, Stanley S. (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-fiber additive
C162S203000, C162S198000, C162S132000, C162S303000, C162S304000, C162S183000, C162S202000
Reexamination Certificate
active
06375799
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 of German Patent Application No. 199 03 943.7, filed on Jan. 28, 1999, the disclosure of which is expressly incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing a fibrous material web, e.g., a paper or cardboard web, from a fibrous material suspension. The invention also relates to a device for carrying out the process.
2. Discussion of Background Information
A starting point for the instant invention is European Patent Application EP 0 894 894, which was not published prior to the above-noted priority date of the instant application. EP 0 894 894, which is expressly incorporated by reference herein in its entirety, discloses the formation of a fibrous material web between two endless, water-permeable belts, preferably wire belts, which occurs in a known manner by virtue of the fact that a portion of the suspension fluid is removed through the belts. In a part of the web-forming zone, the belts, together with the fibrous material web being forming between them, is guided between so-called uniform pressure drainage elements, in the form of, e.g., perforated plates. A disclosed embodiment provides for an additive, e.g., ink, filler, adhesive, draining agent, to be supplied to the fibrous material web being formed by flowing through one of the uniform pressure drainage elements and through the porous belt traveling atop the forming web.
SUMMARY OF THE INVENTION
The present invention improves the web forming process and the apparatus for performing the process to the extent that certain properties of the finished fibrous material web are improved.
As a result, a number of requirements should be fulfilled, if possible. For example, the so-called “two-sidedness” of the fibrous material web can be deliberately influenced, i.e., to achieve as little two-sidedness as possible so that substantially uniform properties occur on both sides of the web or to produce an “intentional two-sidedness” so that the two sides of the fibrous material web have different properties.
An additive can be supplied to the fibrous material web, and a rinsing-out of the additive should be prevented to the greatest extent possible during subsequent draining of the fibrous material web.
When producing multi-ply products, the fibrous material web produced to be united with another fibrous material web should include a ply bond between the two webs that is as high as possible.
The cross profile of particular web properties should be influenced and/or adjusted.
The intensity of drainage in particular partial regions of the web-forming zone can be influenced and/or adjusted.
Accordingly, the process in accordance with the instant invention provides that the supply of the additive is controlled or regulated such that the fibrous material web formed has the respectively deliberate (i.e., either slight or clearly perceptible) two-sidedness. In other words, the supply of the additive is controlled or regulated so that, with regard to a particular surface quality (or with regard to a particular quality level that can be measured on the surfaces of the web), a particular ratio is produced between the properties or quality levels of the two sides of the web.
In an exemplary embodiment of the process according to the invention, during a continuous manufacturing process, a particular property can be continuously measured on both sides of the traveling fibrous material web (e.g., paper web). Thus, a continuous determination may be made as to whether the intended degree of two-sidedness is being achieved.
If the degree of two-sidedness deviates from an intended value of two-sidedness (i.e., a set point), then a volume flow and/or a pressure of the additive being supplied, for example, can be varied so that the two-sidedness of the material web being formed approaches the set point, e.g., with the aid of a closed control loop. By varying the pressure, the penetration depth of the additive, among other things, can be deliberately controlled, which can lead to an optimization of the distribution of additive in the Z-direction.
A particularly important further concept of the invention is that a fine fibrous material suspension can be used as an additive. The fine fibrous material suspension can be obtained, e.g., from suspension fluid removed in a beginning region of a twin wire zone, i.e., the so-called “white water.” In this instance, a definite, e.g., particularly high, fines content can be produced on one of the two sides of the fibrous material web or on both sides of the web. The level of the fines content is important, for example, for the printability of the finished fibrous material web. In a similar manner, it is important in the production of a multi-ply product that, before the two fibrous material webs are united, the fines content on the web sides to be joined together, or arranged to come into contact with one another, can be increased to the greatest extent possible. Other possible additives include, e.g., filler suspension, polymer solution, adhesive solution, or starch solution, or an ink that is supplied, for example, at a particular location.
When utilizing the process according to the invention, the location of the additive supply is in a vicinity of the so-called “uniform pressure drainage.” This is the region of web formation in which drainage occurs through the use of an essentially pulsation-free drainage pressure. In this regard, in a relevant part of the web-forming zone, drainage pressure either remains essentially the same or changes almost continuously, e.g., increases. Consequently, drainage of this type differs from the drainage method normally used in the beginning region of the web formation in which, with the aid of so-called “forming strips,” pressure pulsations are produced in the suspension while it is present between the belts. This results in the fibrous material remaining as uniformly distributed as possible during the web formation process.
A particular advantage of the supply location (for the additive) in the vicinity of the uniform pressure drainage is that, after the supply of the additive, the subsequent drainage can be controlled so that as little as possible of the supplied additive is lost. This is achieved, e.g., by virtue of the fact that the additive is supplied at the beginning region or in the middle region of the uniform pressure drainage zone and that, downstream of the supply point, the intensity of the subsequent drainage can be reduced on the relevant side of the web, and may even be, e.g., completely suppressed in a particular section. At the same time, the intensity of drainage on the opposite web side can be increased through the use of, e.g., a vacuum and by providing increased perforation cross-sections in a particular region.
The prevention of drainage on the side of the web on which the additive has been supplied is possible, e.g., by virtue of the fact that either a closed, i.e., non-perforated, plate element is provided in a particular partial region of the uniform pressure drainage zone or a part of the perforation is closed, e.g., with the aid of a compressed air buffer. In any case, it can be assured that a very high retention of the supplied additives can be expected. Otherwise, the invention also assures that the fines and/or fillers contained in the fibrous material suspension from the beginning are retained to a higher percentage than previously in the fibrous material web being formed.
In an alternative embodiment, and with the aid of uniform pressure drainage elements of different permeabilities, it is possible to assure that drainage through one belt is more intense than the drainage through the other belt. In extreme cases, in a particular region of the uniform pressure drainage zone, the removal of suspension fluid through one of the two belts can be suppressed at least to a large extent, e.g., with the aid of a water-impermeable uniform pressu
Bachler Josef
Halmschlager Günter
Merckens Christoph
Greenblum & Bernstein P.L.C.
Halpern Mark
Silverman Stanley S.
Voith Sulzer Papiertechnik Patent GmbH
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