MXPA98008130A - Fabric paper confeccionadora to increase the volume in a sheet of pa - Google Patents

Abstract

A papermaking fabric for increasing the volume in the sheet of paper during forming and / or drying by traversed air, which consists of a system of selectively woven MD filaments with a CD filament system having subsets of filaments at least minor and greater

Description

PAPER PREPARATION FABRIC FOR INCREASING THE VOLUME IN A PAPER SHEET BACKGROUND OF THE INVENTION Field of the Invention This invention relates in general terms to the fabrics that are used in the manufacture of paper. It relates more specifically to the formation and air drying of fabrics. It concerns more especially the fabrics that serve to increase the volume in the sheet of paper during the formation of the paper and / or in the course of the air-drying processes. Description of the Related Art In the process of papermaking, papermaking machines transform an aqueous pulp of fibers into a continuous paper web, which can be treated or processed for a variety of end uses. Papermaking fabrics are used throughout the papermaking process to transport the paper web as a web through the papermaking equipment. These papermaking fabrics also act as a driving band for the equipment.

The papermaking process begins in the forming section within a papermaking machine in which the aqueous paste is deposited on a forming fabric. The forming fabric conveniently retains the paper fibers while allowing excess water to pass through it. The wet paper web thus created with this process is then carried by a press fabric through the press section where the additional water is removed by squeezing the paper web and the fabric between two rollers. The paper web is then carried through the dryer section in a dryer fabric to remove the additional water by means of a forced evaporation system. The design of the papermaking fabrics used in each section of a papermaking machine varies according to the function. In the forming section of the paper manufacturing machines, the fibers are retained and collected on the upper face of a forming fabric to become a sheet of paper. The forming fabric should have a thin mesh weave or fabric on the side where it comes into contact with the paper in order to avoid marking the paper and supporting the fiber against the aqueous paste. The fabric must also have good drainage characteristics for the initial removal of water to facilitate the formation of the paper. However, as previously noted, the forming fabric also serves as a driving belt and is subject to high tensile loads in the machine direction as well as compressive or buckling loads in the transverse direction of the machine. The performance of a fourdrinier type papermaking machine is improved when the sheet is formed at a good height above the face of the sheet of the forming fabric. When the sheet is formed at a high level on the surface of the forming fabric, the sheet is better off since it is not trapped inside the band and thus higher machine speeds can be applied and greater efficiency of the manufacturing machine is achieved . In addition, when the sheet is formed at a good height above the fabric, the wire marking on the paper surface is reduced. On the other hand, for applications such as tissue paper and towel-type, it may be convenient to form a band with some fibers in the "Z" directions to create an additional volume on the paper sheet before finishing processes such as drying by traversing air.

After forming, the paper web can be subjected to a drying step with air trapping in order to impart an additional volume and a greater absorbency to the material. Accordingly, it is convenient to have a papermaking fabric that provides a fabric sheet forming system at a good height together with a greater volume and absorbency of the resulting paper product. It is also convenient to have such a papermaking fabric with improved wear capabilities. SUMMARY OF THE INVENTION A papermaking fabric that imparts volume to a paper product and has one side of sheet and one machine side, consists of a system of MD filaments (international abbreviation by: Machine Direction), selectively interwoven with a CD filament system (international abbreviation for: Direccion Transversal a la Machine), which have subsets of filaments at least smaller and larger in size, in which the MD filaments and the CD major filaments define maximum floats on opposite sides of the fabric that differ by no more than a single filament and the CD filaments Minors define floats or knuckles on the opposite sides of the fabric that lie within two filaments on the other side reciprocally and define lateral areas of sheet of paper depressions that give greater volume to it. It is an object of the present invention to provide a papermaking fabric, especially with a method of forming or drying with air traversing the fabric, this fabric having both an improved sheet support and better anti-wear characteristics in the fabric. so much that the fabric gives the sheet a greater volume at the same time. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a diagram of the tissue pattern of a papermaking fabric according to the present invention. Figure 2 is a sectional view taken along line 2-2 in Figure 1 showing the tissue pattern of a first MD filament that is interwoven with the CD filaments of the fabric. Figure 3 is a sectional view on line 3-3 of Figure 1 showing the tissue pattern of a CD filament of smaller diameter woven with the MD filaments of the fabric. Figure 4 is a sectional view on line 4-4 of Figure 1 showing the tissue pattern of a larger diameter CD filament that is woven with the MD filaments of the fabric. Figure 5 is a tissue pattern diagram of a second embodiment of the papermaking fabric. Figure 6 is a sectional view showing a second tissue pattern for the MD filament on line 6-6 of Figure 5. Figure 7 is a sectional view showing a second tissue pattern for the CD filament of smaller diameter per line 7-7 of Figure 5. Figure 8 is a sectional view showing a second tissue pattern for the larger diameter CD filament on line 8-8 of Figure 5. Figure 9 is an illustration of a process to form a paper web using a paper machine, with air dryer traversed. DETAILED DESCRIPTION OF THE FORM OF REALIZATION PREFERRED The invention will be described with reference to the figures of the drawings in which like numbers represent similar elements in all the illustrations.

With reference to figures 1 to 4, the fabric 1 has a system of filaments in the machine direction (MD) 20, interwoven with a system of filaments in the transverse direction of the machine, of smaller and larger diameter, alternating, 22 and 24. The fabric has its side turned to the sheet, that is, the sheet side S and one side turned to the machine, ie the machine side M. As shown in FIG. 2, the MD 20 filaments are woven in a pattern repetitive of above one, below two, above two and below five, both with respect to the smaller and larger diameter CD filaments, 22, 24. As shown in figure 3, the CD filaments of smaller diameter 22 are woven in a repeating pattern of below two and above three with respect to the MD 20 filaments. As shown in Figure 4, the larger diameter CD filaments 24 are woven in a repetitive pattern of below one and above four with respect to MD 20 filaments. floats, that is, the long, leaf-side floats of the larger diameter CD filaments 24 are woven in opposition to the long, machine-side floats of the smaller diameter CD filaments 22.

The differences in the S plane of the leaf side are created by alternating the smaller and larger diameter CD filaments 22 and 24. The alternation of the larger diameter filaments 24 and the smaller diameter CD filaments 22 creates a surface enhancement (plane depth), which will increase the volume in the sheet without adversely affecting the release of the sheet during formation or the prevention of bleeding during drying with air traversing. In the embodiment shown in Figures 5 to 8, the MD 40 filaments are woven in a repetitive pattern of above three, below one, above one and below five, with respect to both CD filaments of smaller diameter such as those of larger diameter 42, 44. CD filaments of smaller diameter 42 are woven in a repetitive pattern of above one, below one, above one and below two with with respect to the MD 40 filaments. The larger CD filaments 44, like the CD filaments 24 are woven in a repetitive pattern of below one and above four, with respect to the MD 40 filaments.

The diameter of the larger diameter CD monofilaments is in a range between about 0.1 and 0.8 mm and preferably about 0.4 mm. The diameter of the CD filaments of smaller diameter is in a range between approximately 0.08 and 0.6 mm and preferably 0.25 mm. The MD and CD filaments can be polyester, polyamide, vinyl, acrylic and other materials known in the art. In a preferred embodiment of the present invention, the polyester filaments are made, which has been treated for resistance to hydrolysis. The filaments may be of different compositions. In a preferred embodiment of the present invention, the fabric, in its woven condition, reaches an air permeability of 450 to 650 CFM and more preferably of the order of 550 CFM approximately. Other embodiments may exhibit air permeability up to 1000 CFM. The fabric of the present invention preferably has an open area of 5% to 30% and more preferably 10%. The fabric of the present invention can be woven in an endless configuration or it can also be woven in a flat condition.

In summary, it can be seen that CD filaments of greater diameter will define floating yarns on the leaf side of at least 4 filaments and yarns of smaller diameter will define floating yarns or knuckles and floating yarns that remain within two filaments of the other reciprocally. This yields to the papermaker a fabric that has floating sheet release yarns at a high level, and sheet depressions that provide volume, without the necessity of having to make a choice between them. As an example, a conventional, traversed air drying and forming process is illustrated in FIG. In this process the fibers are fed from a head box (110) to a convergent set of forming fabrics (120, 130). In this double wire forming arrangement, the water is removed from the band by centrifugal forces and by means of vacuum aids. The nascent, wet band is transferred in clean condition to the forming fabric (130) through a "uhle" box (140). Optionally, the web can be processed to remove the water by means of the vacuum box (150) and the steam jacket (160). The band is carried by the forming fabric (130) until it is transferred to an air trapping cloth (170), which is at the junction point (280), which is carried out by means of a shoe. of vacuum collection (190). The band is further dehydrated in the dewatering box (200) to increase the solids present in the band. The web is then drawn to the air-trapping fabric (170) to a dryer unit (210) where the heated air is allowed to pass both through the fabric and through the web to increase the solid content of the fabric. band. In general, the band has a dryness of 30% to 95% after leaving the dryer unit (210).

Claims (14)

1. CLAIMS 1. A single-layer papermaking fabric that imparts volume to a paper product and that has a sheet side and a machine side, consisting of: a MD filament system (International abbreviation for the Machine), selectively interwoven with a CD filament system (international abbreviation of Transverse Machine Direction), which has subsets of at least minor and major filaments, in which the MD filaments and the larger CD filaments define long maximums of the floating yarns on opposite sides of the fabric differing by no more than a single filament and smaller CD filaments defining floating yarns or knuckles on opposite sides of the fabric that remain within two MD filaments on the other side reciprocally and define side areas of sheet of depressions that impart volume to the paper.
2. 2. A procedure for making a sheet of paper that has an increased volume and that consists of the steps of: supplying paper manufacturing equipment with a dryer that works with traversed air; providing a single-layer trailing air dryer fabric within the air-drying dryer equipment, this air dryer fabric having one side of the sheet and one side of the machine, this fabric consisting of a selectively woven MD filament system with a system of CD filaments having subsets of at least minor and major filaments, defining the MD filaments and the largest long CD filaments of the floating yarns on opposite sides of the fabric differing by no more than a single filament and the CD filaments minors define floating threads or knuckles on opposite sides of the fabric that lie within two MD filaments on the other side reciprocally, and define sheet side areas of depressions that impart volume to the paper; supplying a partially dehydrated paper web to the sheet side of the dryer fabric with traversed air, and supplying an element for printing or applying under pressure the web of paper against the fabric and even into the depressions of the fabric.
3. 3. A paper product made by the process of: supplying paper manufacturing equipment with airborne dryer through; providing a single-layer, cross-air drying fabric inside the air-drying dryer, said air-dryer fabric having one side of the sheet and one machine side, the drying fabric consisting of air through and a system of selectively woven MD filaments with a system of CD filaments having subsets of at least minor and major filaments, the MD filaments and the major filaments CD define maximum lengths of the floating yarns on opposite sides of the fabric differing by no more than one filament and the smaller CD filaments define floating yarns or knuckles on opposite sides of the fabric that lie within two MD filaments of the other reciprocally and define areas on the leaf side of depressions that impart volume to the paper; supply a partially dehydrated paper web to the sheet side of the dryer fabric with traversed air; and supplying an element for printing or applying under pressure the band of paper against the fabric and even within the depressions of the fabric.
4. 4. A single-layer papermaking fabric that imparts volume to a paper product and that has a sheet side and a machine side, consisting of: a system of MD filaments selectively woven with a CD filament system having sub-assemblies of filaments at least smaller and larger, in which the larger CD filaments have a repetitive pattern involving at least five MD filaments and that includes at least one floating yarn of three or more MD filaments and the smaller CD filaments have a repeating pattern which involves at least 5 MD filaments and which includes at least one floating yarn of two or more MD filaments and at least one floating yarn or knuckle on its opposite side that remains within 2 MD filaments of the floating yarns on the opposite side of the yarn. such that the leaf-side areas of the depressions imparting volume to the paper are defined.
5. The papermaking fabric according to claim 4 wherein the MD filaments are woven in a repetitive pattern of above one, below two, above two and below five both with respect to the CD filaments of smaller diameter and larger.
6. The papermaking fabric according to claim 4 in which the MD filaments are woven in a repetitive pattern of above three, below one, above one and below five both with respect to the filaments CD of smaller diameter as greater.
7. The papermaking fabric according to claim 4 wherein the CD filaments of larger diameter have a diameter that is in the range of between 0.1 mm and 0.
8. 8 mm approximately in the order of 0.4 mm. The papermaking fabric according to claim 4, wherein the CD filaments of larger diameter have a diameter of the order of about 0.4 mm.
9. 9. The papermaking fabric according to claim 4 wherein the CD filaments of smaller diameter have a diameter that is in the range between 0.08 and 0.6 mm, approximately.
10. 10. The papermaking fabric according to claim 4, wherein the CD filaments of smaller diameter have a diameter of the order of 0.25 mm.
11. The papermaking fabric according to claim 4, wherein said fabric achieves an air permeability that is in a range of 450 to 650 CFM.
12. 12. The papermaking fabric according to claim 4 wherein said fabric achieves an air permeability of the order of 550 CFM.
13. 13. The papermaking fabric according to claim 4 wherein said fabric has an open area of about 5% to 30%.
14. 14. The papermaking fabric according to claim 4 wherein said fabric has an open area of the order of about 10%.