MXPA05013700A - NONWOVEN PAPERMAKERâÇÖS FABRIC - Google Patents

Abstract

A nonwoven papermakerâÇÖs fabric, usable in the dryer section of a paper machine, has a spiral wound machine direction (MD) base layer of raw stock which is wound around a pair of parallel rolls or cylinders until the desired length and width is achieved. The spiral wound MD layer is overlaid with a cross-machine direction (CD) layer of similar or dissimilar raw stock and mated by any of a number of means. The spiral wound MD layer can also be mated to another MD layer spiraled in the opposite direction and in one embodiment further mated to a CD layer. The fabric is preferably produced so that its neutral line is oriented toward the paper side of the fabric so that the paper sheet will stretch less than when typical dryer fabrics are used to turn the paper sheet and fabric around the dryer cylinders.

Description

NON-WOVEN FABRIC FOR MANUFACTURING PAPER Field of the Invention The present invention relates to papermaking techniques. More specifically, the present invention relates to drying fabrics for the drying section of a paper machine. Description of the Prior Art During the papermaking process, a cellulosic fibrous web is formed by depositing a fibrous mixture, i.e., an aqueous dispersion of cellulose fibers, on a moving forming fabric in the forming section of a machine for make paper A large amount of water is drained from the mixture through the forming fabric, leaving the cellulosic fibrous web on the surface of the forming fabric. The newly formed cellulosic fibrous network proceeds from the forming section to a press section, which includes a series of pressure contact zones. The cellulosic fibrous network passes through the contact areas of pressure supported by a press fabric, or as is often the case, between two such press fabrics. In the contact areas of pressure, the cellulosic fibrous network is subjected to compressive forces that squeeze water from it, and adhere the cellulosic fibers in the network to each other to convert the cellulosic fibrous network into a sheet of paper. The water is accepted by the fabric or press fabrics and, ideally, does not return to the sheet of paper. The sheet of paper finally proceeds to a drying section, which includes at least a series of rotating drying drums or cylinders, which are heated internally by steam. The newly formed paper sheet is sequentially guided in a serpentine path around each in the series of drums by a drying fabric, which holds the sheet of paper tightly against the surfaces of the drums. The heated drums reduce the water content of the paper sheet to a desirable level through evaporation. It should be noted that the forming, press and drying fabrics take the form of endless cycles on the paper machine and function in the manner of conveyors. It should be further appreciated that papermaking is a continuous process that proceeds at considerable speeds. That is, the fibrous mixture is continuously deposited on the forming fabric in the forming section, while the freshly made paper sheet is continuously rolled onto rolls after it leaves the drying section. The present invention relates specifically to the drying fabrics used in the drying section. The cylinders in the drying section can be arranged in one - row or top and bottom row. Those who are in the bottom row can alternate in relation to those in the top row, rather being in a forced vertical relationship. As the sheet proceeds through the drying section, it may alternatively pass between the upper and lower rows as it first passes around a drying cylinder in one of the two rows, then around a drying cylinder in the another row, and so sequentially through the drying section. In order to increase production rates and minimize alteration in the sheet, single-pass drying sections can be used to transport the sheets that are dried at high speeds. In a single-pass drying section, such as that shown in Figure 5, a sheet of paper 198 is transported by the use of a single drying cloth 199 that follows a serpentine path sequentially around the drying cylinders. 200 in the upper and lower rows. Additionally, a variety of rotating rollers can be used. These rotating rollers can be solid or ventilated. It will be appreciated that, in a single-pass drying section, the drying fabric holds the sheet of paper being dried directly against the drying cylinders in one of the two rows, typically the top row, but it carries around the drying cylinders in the bottom row. The return pass of the fabric is above the top drying cylinders. On the other hand, some of the single-pass drying sections have the opposite configuration in which the drying fabric directly holds the sheet of paper against the drying cylinders in the lower row but carries it around the upper cylinders. In this case, the return pass of the fabric is below the bottom row of the cylinders. In any case, a compression angle is formed by the air carried by the rear surface of the drying cloth moving in the narrowest space where the drying fabric in motion approaches the drying cylinder. The resulting increase in air pressure at the compression angle causes air to flow outwardly through the drying fabric. This flow of air, in turn, forces the sheet of paper away from the surface of the drying cloth, a phenomenon known as "falling." Falling can reduce the quality of the paper product that is manufactured by causing edge fractures. Falling can also reduce the efficiency of the machine if it leads to blade breaks. Many paper mills have addressed this problem by machined slots in the drying rolls or by adding a vacuum source to the drying rolls. Both of these resources allow air otherwise trapped in the compression angle to be removed without passing through the drying cloth, although both methods are costly. Contemporary drying fabrics are produced in a wide variety of styles designed to meet the requirements of the papermaking machines on which they are installed for the grades of paper that are made. Generally, they comprise a commonly woven base fabric of monofilaments and can be single-ply or multi-ply. The yarns are typically extruded from any of several synthetic polymer resins, such as polyamide and polyester resins, used for this purpose by persons of ordinary skill in the coating techniques of papermaking machines. Fabrics in modern papermaking machines can have a width of from 5 to more than 33 feet, a length of from 40 to more than 400 feet and a weight of from about 100 to more than 3,000 pounds. These fabrics wear out and require replacement. Fabric replacement often involves putting the machine out of service, removing the worn fabric, preparing it to install a fabric and installing the new fabric. Although many fabrics are endless, many of the fabrics currently used come together on the machine. The installation of the fabrics includes pulling the body of the fabric over the machine and joining the ends of the fabric to form an endless band. In response to this need to produce fabrics in a variety of lengths and widths more quickly and efficiently, fabrics have been produced in recent years using a spiral wound technique described in the U.S. Patent. commonly assigned No. 5,360,656 to Rexfelt et al. , the teachings of which are incorporated into the present by reference. The U.S. Patent No. 5,360,656 shows a fabric comprising a base fabric having one or more layers of cut fiber material sewn thereon. The base fabric comprises at least one layer composed of a spirally wound strip of woven fabric having a width that is smaller than the width of the base fabric. The base fabric is endless in the longitudinal or machine direction. The threads in the longitudinal direction of the spirally wound strip make an angle with the longitudinal direction of the fabric .. The strip of woven fabric can be woven flat on a loom which is narrower than those typically used in the production of coatings for machines to make paper. The base fabric comprises a plurality of convoluted and coiled turns of the relatively narrow woven fabric strip. The strip of fabric is woven from yarns in the longitudinal direction (warp) and in the transverse direction (weft). Adjacent turns of the spirally wound fabric strip may be in contact with each other, and the spirally continuous joining line thus produced can be closed by stitching, stitching, fusing, welding. { e. g. , ultrasonic) or rubberized. Alternatively, the adjacent longitudinal edge portions of the attached spiral turns may be arranged superimposed, while the edges have a reduced thickness, so as not to cause an increased thickness in the overlap area. Still alternatively, the spacing between the yarns in the longitudinal direction can be increased at the edges of the strip, so that, when the attached spiral turns are arranged in an overlapping manner, there can be a spacing without change between the yarns in the longitudinal direction in the overlay area. In any case, the result is a woven base fabric, which takes the form of an endless cycle and which has an internal surface, a longitudinal direction (of the machine) and a transverse direction (transverse to the machine). The side edges of the woven base fabric are then adapted to make them parallel to their longitudinal (machine) direction. The angle between the machine direction of the woven base fabric and the spirally continuous joining line can be relatively small, that is, typically less than 10 °. For the same reason, the yarns in the longitudinal direction (warp) of the woven fabric strip make the same relatively small angle with the longitudinal direction (of the machine) of the woven base fabric. Similarly, the yarns in the transverse direction (weft) of the woven weft strip, which are perpendicular to the yarns in the longitudinal direction (warp), make the same relatively small angle with the transverse direction (transverse to the machine) of the yarn. the woven base fabric. In summary, neither the yarns in the longitudinal direction (warp) nor the transverse direction (weft) of the woven fabric strip are aligned with the longitudinal (machine) or transverse (machine transverse) directions of the woven base fabric . A fabric having such a base fabric can be referred to as a multi-axis fabric. While the standard fabrics of the prior art have three axes: one in machine direction (MD), one in the cross machine direction (CD), and one in the Z direction, which is through the thickness of the fabric, the multiaxial fabric has not only these three axes, but also has at least two axes more defined by the directions of the yarn systems in their spirally wound layer or layers. In addition, there are multiple flow paths in the z direction of a multi-axial fabric. As a consequence, a multiaxial fabric has at least five axes. Due to its multiaxial structure, the multi-axial fabric having more than one layer exhibits superior resistance to clumping and / or crushing in response to MACF # 148245 v1 12/14/2005 JGD - compression during the papermaking process as compared to one having base fabric layers whose yarn systems are parallel to each other. The present invention provides an alternative to typical woven drying fabrics. The present invention is a non-woven drying fabric produced directly from provisions of natural material. This procedure allows the incorporation of material elements in mass into the fabric and greater design control of the operative characteristics of the fabric. In addition, the present fabric can be produced using a spiral winding technique, similar to the one discussed above, by replacing the strips of woven material with natural elements of stock material.

SUMMARY OF THE INVENTION According to the foregoing, the present invention is a drying cloth, although it may find application in the forming, pressing and drying sections of a papermaking machine. The present invention is a non-woven fabric for making paper for use in the drying section of a paper machine. The.layer has a spirally wound machine direction (MD) layer made of a first natural supply material. The spirally wound MD layer is formed by winding MD elements of the first natural supply material around a pair of parallel rollers or cylinders until the layer has a desired length and a desired width. A layer in the cross machine direction (CD) of CD elements of a second natural stock material overlaps and cakes with the spirally wound MD layer. Preferably this is done so that the fabric has a neutral line oriented towards the paper side of the fabric. This placement of the neutral line in the direction of thickness direction in the fabric reduces the stretching of the supported paper sheet when it is used in a papermaking machine according to the turns of the fabric around the cylinders in the papermaking machine . In another embodiment of the invention, the fabric has a spirally wound first machine direction (MD) layer of a first natural supply material. The first spirally wound MD layer is formed by winding the MD elements of the first natural supply material in a first direction around a pair of parallel rollers or cylinders until the layer has the desired length and the desired width. A second spirally wound MD layer of a second natural supply material is formed by winding MD elements of the second natural supply material in a second direction opposite to the first direction. The second spirally wound MD layer overlays and cakes with the first MD layer wound in a spiral. Preferably this is done so that the fabric has a neutral line oriented towards the paper side of the fabric. This, as above, also reduces the elongation of the paper sheet when it is used in a papermaking machine as the fabric rotates around the cylinders in the papermaking machine. In a further embodiment, in addition to the first and second MD layers wound in spiral (or more) a CD layer is provided and overlays (or interspersed between) the MD layers and cakes with them. Other aspects of the present invention include that the spirally wound MD layer forms the paper side of the fabric and the CD layer forms the machine side of the fabric. The first natural material of provisions can be the same as the second natural material of provisions. The MD elements and the CD elements are preferably flat filaments, round filaments, textured filaments, bulky wavy filaments, shaped filaments, hollow filaments, films, non-woven materials, or segments of woven material. The natural material of provisions is. preferably one. of polyamide, polyester, polyolefins, or other polymeric material. The air permeability and water permeability of the fabric are determined by the separation of the MD elements. The CD elements can be matched to the spirally wound MD layer using a rotating cylinder having separation elements for placing the CD elements directly on the spirally wound MD layer. The CD layer may alternatively be bonded to the spirally wound MD layer using a heat activated bonding process. CD elements can be provided with channels or MD-oriented slots to provide improved handling of the air through the fabric. The present invention will now be described in more complete detail with frequent reference being made to the drawing figures, which are identified below. BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the invention, reference is made to the following description and accompanying drawings in which: Figure 1 is a procedure for producing the spirally wound base layer of natural provisions in accordance with the teachings of the present invention; Figure 2 shows a non-woven fabric according to the present invention installed on a drying section of a paper machine; Figure 2A shows a straight cut view of the present fabric in Figure 2; Figure 3 is a method for caking the CD layer of natural supplies to the spirally wound base layer in accordance with the teachings of the present invention; Figure 4 is another method for caking the CD layer of natural supplies to the spirally wound base layer in accordance with the teachings of the present invention; and Figure 5 is a cross-sectional view of a single pass drying section. DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The present invention relates to a fabric produced for the drying section of a papermaking machine that is produced as a non-woven product using several different natural supply materials. The present fabric is an alternative to the typical drying fabrics that are woven using monofilament yarns or polymeric multifilaments or spirally linked drying fabrics. Specifically, the present fabric has a machine direction (MD) spirally wound base layer of natural supplies that wrap around two parallel cylinders until the desired length and desired width is achieved. This spiral wound technique is similar to the one taught in the Patent? 656 - which was discussed above and is incorporated herein by the HACF # 148245 v1 12/14/2005 JGD - reference - only that strips of woven material are replaced in the present invention with elements of natural supply material. Figure 1 is an exemplary procedure for producing the spirally wound base layers of natural supply elements in accordance with the teachings of the present invention. As shown in Figure 1, the natural supply material is fed through a supply system, preferably from a harness / bobbin 10 installation, through a feed mechanism 15 which winds the provisions around the cylinders 30 (heated or unheated) to form a spirally wound base layer 20 until the desired length and desired width is achieved. This base layer is essentially a spirally wound layer of natural supply material that is oriented substantially along its length. The spacing between the elements of the natural supply material can be zero to form a sealed cylinder, or it can be spaced appropriately to control the air and water permeability of the fabric. It should be understood that many other methods can be used to produce the spiral wound base layer and that the present invention is not limited to this process. The spirally wrapped MD layer is superimposed with a layer (CD) in the direction transverse to the machine of - - similar or different natural provision and cakes by any of a variety of means. Figure 3 is an exemplary method for caking the CD layer of natural supply to the spirally wound base layer according to the teachings of the present invention. As shown in Figure 3, the spirally wound layer 20 is rotated around two cylinders 30 and the elements of the natural material CD of provisions 35 are attached to the MD layer by a feed mechanism 40. Figure 4 is another procedure exemplary for caking the CD layer of natural supplies to the MD base layer according to the teachings of the present invention. As shown in Figure 4, the spirally wound layer 20 is rotated around two cylinders and the elements of the natural material of supplies CD 35 are fed by a feed mechanism 42 through a conveyor means 43 and are joined to the MD layer by a joining means 44. In this embodiment, the fabric can be turned inward so that the MD layer is the paper side of the fabric and the CD layer is the machine (or use) side of the fabric. The CD elements can be superimposed on the spirally wound MD layer by a variety of methods, including a rotating cylinder with spacing elements or shapes that allow the rotating cylinder to feed the elements directly to the MD spiral. Each round MD of the natural supply is caked to the adjacent turn by any of a variety of means, including adhesion through glues (hot melts, "snap closures" male / female), applying an elacer system to attach the elements (through sewing, weaving, etc.) or by applying a layer of meltable material, fuse between the turns and applying heat to the structure to subsequently bond the turns together .. Similarly, the MD spiral of the natural supply the CD elements are bonded perpendicularly to similar or different natural provisions by any of a variety of means, including adhesion through glues (hot melts, "male / female instant closures" (where practical)), applying a Linker system for coupling the CD and MD elements (through stitching, weaving, etc.) or by applying a layer of meltable material, fuse between the CD layers and MD and applying heat to the structure to subsequently bond the layers together. This bonded structure forms a non-woven fabric consisting of MD elements and CD elements that provide the stability and integrity required for the papermaking fabric. Alternatively in another embodiment of the present invention, the original spirally wound MD layer may be coupled to another spirally wound MD layer which is wound in the opposite direction in order to provide the necessary stability in the MD and CD. Note that this method can be extended so that many spirally woven layers can be laminated together in a manner as mentioned above as required to form the fabric. A variation of this would be to include a CD layer in addition to the two MD layers (or more) which can be placed on top or interspersed with each other appropriately laminated together. The present fabric can preferably be produced so that its neutral line is oriented (ie, offset or offset) towards the paper side of the fabric so that the paper sheet will stretch less than when the typical drying fabrics are used as the sheet and the fabric passes around the drying cylinders. Figure 2 shows a non-woven fabric according to the present invention installed on a drying section of a paper machine. Figure 2A shows a straight cut view of the present fabric in Figure 2, which is comprised of the spirally wound layer MD.20 and the CD layer 35 having a neutral line 60 that moves to one side of the other. the fabric as shown (by dotted lines).

One method to produce such a displaced neutral line is by applying a CD layer that is as thick or thicker in caliper than the MD layer. This provides a structure that exhibits this flexible behavior when wound around the drying cylinders, thereby providing a greater change in distance in the MD on one side of the fabric as opposed to the other side of the fabric. This is advantageous for the production of the paper sheet, since when the paper is in contact with the side of the fabric closest to the neutral line, the fabric and therefore the paper will stretch less than with typical fabrics as the fabric rotates around the drying cylinders. The present fabric can be produced either endless or preferably joined through a joint, using any method known in the art. The natural furnish materials used in the present invention are preferably polyesters, polyolefins (polypropylene), polyphenylene sulfide (PPS, which is commercially available under the name of RYTON®), polyamides or other polymeric materials. Another example of material is a heat-modified polyester, resistant to hydrolysis and. to the . contaminants of the variety described in the U.S. Patent. commonly assigned No. 5,169,499 and used in drying fabrics sold by Albany International Corp. under the trademark THERMONETICS®. The teachings of the U.S. Patent No. 5,169,499 are incorporated herein by reference. In addition, such materials as poly (terephthalate cyclohexanedimethylene isophthalate) (PCTA), polyetheretherketone (PEEK) and others can also be used. Any combination of materials may be used as identified by an ordinary expert in the art. The process according to the present invention involves the use of elements of natural provisions, which could be flat filaments, round filaments, textured filaments, voluminous wavy filaments, shaped filaments, (joint-in-slot, tetrahedron, elliptical, rectangular, etc. ..) hollow filaments, films (perforated or non-perforated), non-woven materials (ie, joined by spinning, joined by fusion, etc.) or segments of woven material. Note that the flat filaments can be used in both the MD and CD sections or, as in the case of the opposite spirally wound layers, in one or all of the spirally bonded layers. Any combination of elements for any layer of the fabric can be used as identified by someone of ordinary skill in the art. Note that some or all of the CD elements may include channels or MD-oriented slots to improve air handling by the fabric.

The modifications to the foregoing will be obvious to those of ordinary skill in the art, but would not lead to the invention thus modified beyond the scope of the present invention. The following claims must be considered to cover such situations.

Claims (34)

1. - CLAIMS 1. A non-woven papermaking fabric comprising: a spirally wound machine direction (MD) layer of a first natural supply material having a desired length and a desired width; and a layer in the cross machine direction (CD) of CD elements of a second natural supply material superimposed and matted with the MD layer wound in a spiral. The papermaking fabric according to claim 1, wherein the spirally wound MD layer is formed by winding the MD elements of the first natural supply material around a pair of parallel cylinders. The papermaking fabric according to claim 1, wherein the fabric has a neutral line oriented towards the paper side of the fabric, thereby reducing the elongation of the paper sheet when it is installed in a manufacturing machine. paper as the fabric rotates around the cylinders in the paper machine. 4. The papermaking fabric according to claim 1, wherein the spirally wound MD layer forms the paper side of the fabric and the CD layer forms the machine side of the fabric. MACF # 148245 v11411212005 - 5. The papermaking fabric according to claim 1, wherein the first natural material of provisions is the same as the second natural material of provisions. The papermaking fabric according to claim 1, wherein the fabric is a drying fabric for use in a drying section of the papermaking machine. The papermaking fabric according to claim 1, wherein some or all of the MD elements are flat filaments, round filaments, textured filaments, bulky wavy filaments, shaped filaments, hollow filaments, films, non-woven materials or segments of woven material. The papermaking fabric according to claim 1, wherein some or all of the CD elements are flat filaments, round filaments, textured filaments, bulky wavy filaments, shaped filaments, hollow filaments, films, non-woven materials or segments of paper. woven material. The papermaking fabric according to claim 8, wherein some or all said CD elements have channels or grooves oriented MD. 10. The papermaking fabric according to claim 1, wherein the first natural material of - Provisions is one of polyamide, polyester, polyolefins or other polymeric material. The papermaking fabric according to claim 1, wherein the second natural supply material is one of polyamide, polyester, polyolefins or other polymeric material. The papermaking fabric according to claim 1, wherein the CD elements are caked to the spirally wound MD layer using a rotating cylinder having spacing elements for placing the CD elements directly onto the spirally wound MD layer. . The papermaking fabric according to claim 1, wherein the CD layer is caked to the spirally wound MD layer using a heat-activated bonding process. A non-woven fabric for making paper comprising: a spirally wound first machine direction (MD) layer of a first natural supply material; the first spirally wound MD layer being formed by winding MD elements of the first natural supply material in a first direction around a pair of parallel cylinders until the layer has a desired length and a desired width; Y - a second spirally wound MD layer of a second natural supply material formed by winding MD elements of the second natural supply material in a second direction, opposite to the first direction; the second MD layer being spirally wound overlapped and matted with the first MD layer wound in a spiral. 15. The papermaking fabric according to claim 14, wherein the fabric has a neutral line oriented towards the paper side of the fabric, thereby reducing the elongation of the fabric when installed in a custom paper machine as the fabric rotates around the cylinders in the machine to make paper The papermaking fabric according to claim 14, wherein the first spirally wound MD layer forms the paper side of the fabric and the second MD layer forms the machine side of the fabric. 17. The papermaking fabric according to claim 14, wherein the first natural material of provisions is the same as the second natural material of provisions. The papermaking fabric according to claim 14, wherein the fabric is a drying fabric for use in a drying section of the papermaking machine. 19. The papermaking fabric according to claim 14, wherein some or all of the MD elements are of flat filaments, round filaments, textured filaments, bulky wavy filaments, shaped filaments, hollow filaments, films, non-woven materials or segments of material tissue. The papermaking fabric according to claim 14, wherein the first natural supply material is one of polyamide, polyester, polyolefins or other polymeric material. The papermaking fabric according to claim 14, wherein the second natural supply material is one of polyamide, polyester, polyolefins or other polymeric material. 22. The papermaking fabric according to claim 14, wherein the second spirally wound MD layer is caked to the first spirally wound MD layer using a heat activated bonding process. 23. A non-woven fabric for making paper comprising: a first machine direction (MD) spirally wound layer of a first natural supply material; the first spirally wound MD layer being formed by winding MD elements of the first natural supply material in a first direction around a pair of parallel cylinders until the layer has a desired length and a desired width; a second spirally wound MD layer of a second natural supply material formed by winding MD elements of the second natural supply material in a second direction, opposite to the first direction; the layer being formed in the cross machine direction (CD) when winding CD elements of a third natural stock material; and said layers being laminated to each other. 24. The papermaking fabric according to claim 23, wherein said CD layer is superimposed or sandwiched between said MD layers wound in a spiral. 25. The papermaking fabric according to claim 23, wherein the fabric has a neutral line oriented towards the paper side of the fabric, thereby reducing fabric elongation when installed in a papermaking machine. As the fabric rotates around the cylinders in the paper making machine. 26. The papermaking fabric according to claim 23, wherein the spirally wound MD layers form the paper side of the fabric and the CD layer forms the machine side of the fabric. 27. The papermaking fabric according to claim 23, wherein the first natural material of provisions is the same as the second natural material of provisions. 28. The papermaking fabric according to claim 27, wherein the third natural supply material is the same as the first natural supply material or the second natural supply material or both. 29. The papermaking fabric according to claim 23, wherein the fabric is a drying fabric for use in a drying section of the papermaking machine. The papermaking fabric according to claim 25, wherein some or all of the MD elements are of flat filaments, round filaments, textured filaments, bulky wavy filaments, shaped filaments, hollow filaments, films, non-woven materials or segments of woven material. 31. The papermaking fabric according to claim 23, wherein the natural supply material is one of polyamide, polyester, polyolefins or other polymeric material. The papermaking fabric according to claim 26, wherein some or all of the CD elements are of flat filaments, round filaments, textured filaments, bulky wavy filaments, filaments - shaped, hollow filaments, films, non-woven materials or segments of woven material. 33. The papermaking fabric according to claim 32, wherein some or all of the CD elements have channels or grooves oriented MD. 34. The papermaking fabric according to claim 23, wherein the rolled MD and CD layers are laminated using a heat-activated bonding process.