Paper making and fiber liberation – Processes and products – Non-fiber additive
Reexamination Certificate
1999-09-23
2001-10-16
Silverman, Stanley S. (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-fiber additive
C162S198000, C162SDIG004, C162S164100, C162S164200, C162S168100
Reexamination Certificate
active
06303001
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority Linder 35 U.S.C. §119 of German Patent Application No. 198 43 729.3, filed on Sep. 24, 1998, 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 uniform cross direction profile of a continuous web of paper or cardboard. More particularly, the present invention relates to a paper machine suitable for executing the process mentioned above and the resulting paper.
2. Discussion of Background Information
German patent publication No. DE 37 15 551 A1 discloses a process for reducing the fluttering of the web edges of a paper web as well as a paper machine for executing this process. This patent publication proposes using a stock suspension with a higher strength potential in the edge region of the paper web to be manufactured than in the rest of the web width region. With regard to the paper machine, the publication discloses providing additional lines in the headbox to supply the stock suspension into the side regions of the headbox.
Despite this lateral supply of different stock suspensions to the edge regions or different additives to the stock suspension, varying shrinkage occurs across the width of the web. As a rule, the edges shrink more than the central regions of the material web due to additional processing in the paper machine. However, different shrinkage behavior across the entire width of the material web can also result from different drying speeds or from different processing across the entire material web. Consequently, the problem of uneven shrinkage is not limited to the edges of the web.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for the manufacture of a continuous web, e.g. paper or cardboard web, which produces a homogenization of the shrinkage behavior of the web across the entire width. Another object of the invention is to produce a paper machine for executing the process.
The inventors have recognized that, based on the different shrinkage behavior of the web, e.g. paper or cardborad web, across its width, criteria necessary for high paper quality, for example, surface roughness or strength values, etc., also change across the width, depending on the shrinkage cross direction profile. Therefore, the homogenization of the shrinkage behavior of the paper web should homogenize not only the shrinkage behavior, but also the correlating property parameters of the paper across the entire width of the web. Consequently, the present invention improves the process for manufacturing a paper or cardboard web to the extent that the shrinkage cross direction profile of the web is homogenized during its manufacturing process by influencing the local composition of the stock suspension sectionally across the width by using components having different shrinkage behavior. When the homogenization is achieved, a reduction of the differences in the properties of the material web across the entire width, particularly on its surface, e.g., roughness, results.
According to an embodiment of the process, the shrinkage of a sectional region is intensified by increasing the number of fibers and/or other materials that have an increased shrinkage tendency or, in another embodiment, replacing fibers and/or other materials that have a lower shrinkage tendency in the “normal” mixture of the stock suspension with fibers and/or other materials that have an increased shrinkage tendency.
Reduced shrinkage of a particular section can be achieved in accordance with another embodiment by adding extra fibers and/or other materials that have a reduced shrinkage tendency in this section, or that the “normal” fiber mixture is replaced by a fiber mixture having a reduced shrinkage tendency. The same applies in the reverse for an increase in shrinkage.
Preferably, metering of the desired fibers and/or other shrinkage-influencing materials occurs in the headbox. In terms of the possibilities for metering or admixtures of stock suspensions that have different fiber properties, reference is made to Applicant's earlier German patent applications, DE 37 41 603 A1, DE 40 19 593 A1, DE 44 22 907 A1, DE 42 37 304 A1, and DE 42 11 291 A1, the disclosures of which are incorporated herein by reference in their entireties. With regard to the cited materials, particular emphasis is placed on the fact that possible basis weight changes, which could be produced through the metering of particular stock suspensions, etc., can be compensated for by a regulation mechanism in the known sectioned headboxes, which are supplied with stock suspensions having different concentrations and are sectionally controlled. These cited materials also disclose in detail how the supply of stock suspension having different properties to the headbox can be executed and how the basis weight cross direction profile of the material web can be kept uniform.
According to an improvement of the process, in order to achieve or maintain a desired cross direction profile, in the approach flow system of the paper machine or cardboard machine, at least two stock suspension streams are produced, with fibers that have different shrinkage behaviors and/or with other shrinkage-influencing materials, and close to or in the headbox, the shrinkage of the material web is balanced across the machine width by sectionally mixing at least two stock suspension streams with fibers that have different shrinkage tendencies, while the basis weight cross direction profile and/or the fiber orientation cross direction profile is/are influenced by means of sectionally metering white water flow so that the desired basis weight profiles are maintained or achieved.
According to an aspect of the present invention, a process is provided for homogenizing the property cross direction profile of a continuous material web. The process includes producing at least one machine width stock suspension layer on a wire or between two wires; controlling the local composition of the stock suspension sectionally across the width by changing the proportions of components with different shrinkage behaviors so that the shrinkage cross direction profile of the material web is homogenized during its manufacturing process; and draining, pressing, and drying the material web produced from the stock suspension layer.
The process may also include increasing supply of fibers and/or other materials having an increased shrinkage tendency to produce an intensification of the shrinkage of a sectional region. Alternatively, the process includes replacing fibers with a reduced shrinkage tendency with fibers and/or other materials having an increased shrinkage tendency to produce an intensification of the shrinkage of a sectional region. Alternatively, the process includes increasing a supply of fibers and/or other materials having a reduced shrinkage tendency to reduce the shrinkage of a sectional region. Alternatively, the process includes replacing fibers having an increased shrinkage tendency with fibers and/or other materials having a reduced shrinkage tendency to reduce the shrinkage of a sectional region.
The process may also include metering desired fibers and/or other materials in a headbox and/or in a wet section. Alternatively, the process may also include producing, in an approach flow system of the paper or cardboard machine, at least two stock suspension streams with fibers and/or other materials having different shrinkage behaviors; sectionally mixing at least two stock suspension streams with fibers and/or other materials that have different shrinkage tendencies in the region of the headbox so that the shrinkage of the material web across the machine width is balanced; and sectionally metering dilution water to control a basis weight cross direction profile and/or the fiber orientation cross direction profile.
According to another embodiment, long fibers are used as the fibers with an increased shrinkage behavior, an
Bachler Eduard
Brunnauer Erich
Grossmann Udo
Halmschlager Guenter
Wassermann Alexander
Greenblum & Bernstein P.L.C.
Halpern Mark
Silverman Stanley S.
Voith Sulzer Papiertechnik Patent GmbH
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