MXPA98006967A - Fabric for the confection of paper, process for manufacturing voluminous products and the productsasi obtained - Google Patents

Abstract

The present invention provides in general terms a fabric made with the TAD process, of twill twill for use in shaping a paper web. The present invention more particularly offers a twill TAD type fabric of 7, .3 which is potentially useful for large areas of high bulk and a high degree of absorbency in the paper product.

Description

MANUFACTURING VOLUMINOUS PRODUCTS AND PRODUCTS Thus obtained BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a fabric that is used in an air passage drying process (in English: "through-air drying") to manufacture a BACKGROUND OF THE INVENTION The physical attributes of a paper web are controlled not only by the fibers of the web but also by the web on which the web is produced. It is used to support the belt and form an impression in the belt plays a central role in the development of the attributes of the product.The character of the fabric also has a considerable effect on the attributes of the processing as the ability to pass ("runnability" ") and productivity In a TAD process, the sheet side of the fabric refers to that side of the fabric that is generally used to be in contact with the wet web The reverse, that is, the reverse side, refers to the side of the fabric that is not generally in contact with the band.

A variety of types of TAD fabrics have been proposed in an attempt to achieve good product attributes and favorable processing efficiency. The previous fabrics obtained with the TAD process were basically those of a single layer, of taffeta, semi-twill, 4-puffs or 5 puffs. US Patent Specification No. 3,301,746 discloses the use of diagonal drawstrings of serge / and half-twill, square. U.S. Patent No. 3,974,025 mentioned the use of the reverse of a TAD fabric, of the semi-twill type. Another early development in the technology of TAD fabrics has been disclosed in US Patent No. 4,239,065 in the name of Trokhan. This patent discloses specific openings in which the crosses present on the upper face define a bilaterally displaced arrangement of cavities, similar to wicker baskets, in which each cavity covers at least one crossing that is below the upper face. TAD fabrics create volume in a fibrous web since they compact the web only along certain elevated, related areas. Large portions of the fibrous web, present in the open areas or baskets, between the raised areas, are not compressed during the TAD process. These uncompressed areas are not only soft and absorbent but have a greater bulk. Woven fabrics in a single layer have the advantages of being inexpensive and efficient at the same time without creating difficult processing problems. However, these fabrics have the disadvantage that when the open areas become larger, that is to say when the size of the baskets forming the uncompressed areas of the fibrous web increases, these fabrics provide insufficient support of the fibrous web. . The lack of band support causes the formation of tiny holes or pinholes in the band with the bleeding of the fibers in the vacuum boxes and air ducting, which reduces both the vacuum dehydrating efficiency and the efficiency of dried during the TAD process. The creation of holes can negatively affect the attributes, that is, the good characteristics of the paper, including its strength and visual appearance. The present invention provides a woven fabric with an open area large enough to produce a bulky and smooth paper web, without the formation of pinholes, bleeding of fibers in vacuum boxes or problems related to air channeling. Furthermore, it is pointed out that the present invention combines these advantages in a fabric consisting of a single layer.

SUMMARY OF THE INVENTION It is also an object of the present invention to provide a cloth that dries with air passage that is simple and inexpensive and that despite This gives rise to a voluminous and absorbent sheet of paper. It is further an object of the present invention to provide a fabric that reduces the bleeding of the fibers through the unit and the presentation of jeritos. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an illustration of a process for forming a paper web using a paper dryer machine that works with an air system passing from side to side. Figure 2 is a perspective view of a preferred embodiment of a fabric that is used in papermaking, in accordance with the present invention. Figure 3 is a top plan view of the papermaking fabric, which is taken along line 3-3 of Figure 2. Figure 4 is a side elevational view of the papermaking fabric which has been taken along line 4-4 of Figure 3. Figure 5a-e is a series of viewsschematic illustrating the pattern of the sheaves of an MD yarn for the papermaking fabric of Figure 2. Figure 6 is a side perspective view of the papermaking fabric taken in accordance with line 6-6 of the Figure 2. Figure 7 is a side elevational view of the papermaking fabric taken on line 7-7 of Figure 6. Figure 8a-b is a series of schematic views illustrating the patterns of the puffs of CD yarns with smaller and larger diameter for the papermaking fabric according to Figure 2. Figure 9 is a top plan view of another embodiment of the papermaking fabric according to Figure 2. Figure 10 is an illustration of the knuckles and baskets of the fabric that are used to print the paper web according to the present invention. DETAILED DESCRIPTION The present invention is directed to a fabric to make a soft, high bulky band and high degree of absorbency. As illustrated in the TAD process of Figure 1, a band is formed in a conforming structure. (180) starting from an aqueous paste of pulp. The pulp is introduced from a head box (10) to the forming structure. The shaping structure can be a double wire shaper, a half-moon shaped shaper or any shaping configuration recognized in the art. The web is finally transferred from the forming structure to a carrier fabric constituting a printing fabric by TAD process. Referring to FIGS. 2 to 4, the fabric 1 is shown in a broken twill shed of 7/3 according to the teachings of the present invention. The filaments are interwoven in the direction of the machine (abbreviated this direction MD) 10, with a system of filaments in transverse direction (CD), alternating, of smaller and larger diameter, 12, 14. The fabric has a side of sheet S, see Figure 3, and a machine side M, not illustrated separately, in which the side of the sheet of the fabric 1 defines the characteristics of the paper. Figures 5a-e further illustrate the repeat of shed R according to Figure 2. Each MD filament, 10, is woven above 7 and below 3 strands of type CD (transverse direction), 12, 14 Below each coarse or floating MD yarn, on the side of the sheet 18 there are 4 CD filaments of smaller diameter 12 as well as three CD filaments of larger diameter 14. The CD filaments of smaller diameter, 12, are placed on each side of each CD filament of greater diameter 14. Above each floating thread 19 of type MD on the machine side there is a single CD filament of smaller diameter 12 and two filaments CD of larger diameter 14. The CD filament of smaller diameter 12 is parallel to the larger diameter CD filaments 14, and between them. It is necessary to maintain these relationships in any variant of puff since the puff described above. As shown in Figures 6 to 8, the CD filament of smaller diameter 12 is woven with the MD 10 filaments in a repetitive pattern consisting of one pass above one and one pass below four. The filament-CD-of larger diameter 14 is woven with the MD 10 filaments in a repetitive pattern of passing above one, below one, above one and below two. Inasmuch as repetitive CD lengths are equal in relation to the MD 10 yarns, each knuckle on the side of the sheet 13 formed by a CD filament of smaller diameter 12 is adjacent to, and between a pair of knuckles on the side of the yarn. sheet 15 formed by the CD filaments of greater diameter 14. In view of the fact that the MD 10 filaments are in a relatively higher plane than the CD filaments of smaller diameter 12 and float above a number of CD 14 filaments, the yarns Floating MD 18 dominate the side of the sheet S of the fabric «ae 1. These high profile MD floating yarns 18 cause a compression on the paper sheet (not shown) when it is on top of the fabric 1. The combination of the long leaf side MD yarns 18 and the knuckles of the filaments CD 14 forms a flange around the basket-type depressions on the sheet side of the cloth 1. The knuckles of the lower plane of the CD 12 filaments do not interfere with the baskets where they appear and the floating threads on the side of the machine, long, of the CD 12 filaments provide a lower support or base for the fibers. The paper fibers within these "basket" shapes remain relatively uncompressed compared to the fibers that are in contact with the floating threads MD 18 and the knuckles CD 15. Each basket is defined by at least two MD 10 filaments on two sides and two larger diameter CD filaments 14 on the two remaining sides.The compression areas on the sheet side of the fabric are aligned in the CD direction and are displaced in the MD direction to form baskets diagonally aligned along the fabric 1. The pattern of the shed causes larger and smaller baskets to be formed.In a single CD line of baskets, the long CD of the baskets alternates.If the shorter basket is considered with a length 1 then the Longest basket has a length of about 1-1 / 2. The shorter basket also has a slightly shorter MD and smaller caliber than the longer baskets. These baskets are illustrated by the darkened areas 26 and 28 in Figure 10. As shown in Figures 6, 8a and 8b, the smaller diameter CD filaments 12 lie predominantly in the lower portion of the fabric 1 and provide additional support for uncompressed knots 12 which allow a sheet of paper, not shown, to be printed with depth on the cloth 1 without there being a fiber bleeding through the unit or a hole formation. Further, the location of the smaller diameter CD filaments 12 within the lower portion of the fabric provides the desired additional fiber support without unduly blocking the drainage holes 16, see Figure 3, in the fabric 1. In a form of Alternate embodiment of the present invention, as shown in Figure 9, the fabric 2 is applied to the surface to increase the contact area and provide a single higher plane sheet side. The fabric 2 is brought to the surface until it reaches the larger diameter CD filaments in 24. The surface setting of the MD and CD filaments 10 and 14 causes additional sheet contact over the surface area added that compresses the fibers while the baskets between the floating yarns brought to the surface 21 and the knuckles 24 create areas of uncompressed paper fibers. Large baskets 28 and small baskets 26 are indicated by the darkened areas in Figure 10. In any embodiment, the MD and CD filaments may be polyester, polyamide, vinyl, acrylic, naylon or 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. MD filaments and CD filaments do not need to be of the same material. The smaller diameter CD filaments may also differ in composition compared to the larger MD and CD filaments. For example, hollow and compressible yarns can be used in place of solid filaments for smaller diameter CD filaments. For example, hollow, compressible yarns may be used in place of solid filaments for smaller diameter CD filaments. The hollow yarns will provide greater resilience and compressibility to the fabric. The threads suitable for this case are described in US Pat. No. 5,368,696, which is incorporated as a reference material as if it had been described here in its entirety. Preferably the Hollow core yarns have an empty margin of fifteen to thirty percent (15-30%). In the preferred embodiment, the CD filaments of larger diameter 14 vary between about 0.03 to 0.6 mm and preferably between 0.4 and 0.5 mm. CD filaments of smaller diameter 2 vary between about 0.15 and 0.3 mm and are preferably 0.2 mm. Preferably, the diameter of the larger CD yarns is at least equal to the diameter of the MD yarns. In a preferred embodiment of the present invention, the fabric in its weaving condition achieves an air permeability in the range of 600 to 800 CFM and more preferably of the order of 700 CEM, as tested in an air permeability tester. Frazier air. The fabric of the present invention preferably has an open area, as seen in Figure 3, in the range of ten to twenty-five percent (10 to 25%) and more preferably of the order of twenty percent (20%). The MD filaments and the larger CD filaments are preferably monofilaments. The smallest CD yarn or filament can be of any configuration, it can be for example a monofilament, a multifilament cable, a flat monifilament or a flat monofilament with holes drilled therein, as understood by the expert technician. in the matter. The ratio of the larger diameter CD filaments to the smaller diameter CD filaments is preferably from 1.5: 1 to 4: 1, and more preferably will be 2: 1. The fabric of the present invention can be woven in an endless configuration or it can also be woven in a flat form. The description presented in this text is based on a 'fabric that has been woven flat with the warp filaments running in the direction of the machine. It will be clear to the person skilled in the art that the yarns in the machine direction and in the transverse direction of the machine can be reoriented for an endless weaving process. The fabric according to one embodiment of the present invention has a mesh count of 20 to 50 filaments per inch, that is to say for every 2.54 cm of distance in the transverse direction and more preferably of 30 to 40 filaments per inch, that is, for every 2.54. cm of distance in transversal direction. The fabric according to one embodiment of the present invention has a sufficient mesh count to avoid the formation of pinholes in the fibrous web. It is currently preferred that the mesh count is not less than 20. The fabric according to a form of Embodiment of the present invention has a mesh count of 20 to 50 filaments per inch, ie for every 2.54 cm distance in the machine direction, more preferably at least 30 filaments per 2.54 cm distance in the machine direction. The fabric according to the present invention can be further treated to improve its contact area. Any method recognized in the art can be used to increase the contact area. Exemplary methods are described in U.S. Patent No. 3,579,164, which was granted on March 30, 1971 to Friedberg et al. This patent discloses surfacing or abrasion of the high points of the crossovers to provide regions of flat surface. The contact area refers to the amount of surface placement of the fabric. The fabric according to the present invention preferably has a contact area in the range of 20% to 40% and more preferably 25% to 35% and more preferably still of the order of 30%. The fabric according to the present invention can also be described in terms of orientation of the open areas or baskets and contact areas of the floating threads or knuckles. The fabric according to the present invention has alternating sizes of large baskets and little. The sizes of baskets and knots are measured at the maximum point between two sides and all measurements are based on the fabric before treatments such as abrasion to increase the contact area. The larger baskets and the knots are larger than about 40 miles by 40 miles, more preferably they are in the range of about 60 miles by 40 miles to about 120 miles per 100 miles, and more - preferably of the order of 80 miles by 50 Thousands. The smaller baskets and knots are greater than approximately 20 miles by 30 miles. The baskets also have different depths and therefore have the corresponding knots different heights. The larger baskets are preferably of a depth of 0.3 to 0.7 mm, more preferably have a depth of the order of 0.3 to 0.5 mm and. more preferably they still have a depth of 0.4 mm. The smaller baskets have a preferred depth of the order of 0.15 mm to 0.4 mm, more preferably 0.2 to 0.3 mm and more preferably still the depth will be of the order of 0.25 mm. The baskets are aligned three-way. The large and small baskets are aligned in the transverse direction and the large and small baskets are aligned each in the two diagonal directions. The fabric as described here is used preferably in the TAD process with the knuckles of the long warp on the leaf side. A test cloth was woven using PET monofilaments that had been treated to make them resistant to hydrolysis. The large diameter monofilaments were 0.4 mm. The filaments of smaller diameter were 0.2 mm. The fabric was woven using all large-diameter onofilaments in the machine direction and alternating filaments of large and small diameter in the transverse direction. The large diameter MD filaments and the large diameter CD filaments were interwoven to create a broken twill weave of 7 mm diameter.,3. The alternating CD filaments were only interwoven to the extent necessary to secure them in order to achieve fiber support. The mesh count for the fabric produced was 35 filaments in the machine direction per inch, that is, for each 2.54 cms and 46 filaments in the transverse direction per inch, that is, for each 2.54 cms. The woven fabric was treated to impart thermal and dimensional stability. Then it was treated additionally. the fabric applying a sandpaper to the MD knuckles to increase the contact area of the band to 28%. Then a seam was applied to the fabric through the known technique fraying the ends and retro-weaving them into the body of the fabric to form a continuous or endless fabric.

Claims (18)

1. CLAIMS 1. A papermaking fabric for forming and transporting a web of aqueous paper comprising: - a single-ply fabric having filaments in the direction of the machine of a first diameter and filaments in the transverse direction of a second diameter which they are interwoven to form a pattern of knuckles and baskets; the fabric also having filaments in the transverse direction of a third diameter, alternating with the filaments in the transverse direction of the second diameter and forming central support members at the bottom of the baskets. The papermaking fabric according to claim 1, wherein each filament in the machine direction is woven above seven filaments in the transverse direction and in which three of the seven filaments in the transverse direction correspond to a second diameter and four. of the seven filaments in the transverse direction are of a third diameter. 3. The papermaking fabric according to claim 1 wherein each filament in the machine direction is woven below three filaments in the direction transverse, in which two of the three filaments in the transverse direction correspond to a second diameter and one of the three filaments in the transverse direction is of a third diameter. 4. The papermaking fabric according to claim 1, wherein the filaments in the machine direction corresponding to the first diameter and the filaments in the transverse direction corresponding to the second diameter have an equal diameter. The papermaking fabric according to claim 1, wherein the filaments in the machine direction and the filaments 'in the transverse direction' are all monofilaments. 6. The papermaking fabric according to claim 1, wherein the fabric has a mesh count in the transverse direction from 20 to 50 filaments per inch, that is, every 2.54 cms. The papermaking fabric according to claim 1, wherein the fabric has a mesh count in the machine direction from 20 to 50 filaments per inch, that is to say for every 2.54 cms. The papermaking fabric according to claim 1, wherein the fabric is sanded on the side of the sheet. 9. The papermaking fabric according to claim 8, which is sanded to a contact area of 20% to 40%. 10. The papermaking fabric according to claim 1, wherein the fabric is a forming fabric. 11. In combination with a papermaking apparatus with a dryer operating with passing air, which has at least one dryer position: by way of a papermaking fabric that dries with the passage of air, which comprises: a fabric in a single layer having filaments in the machine direction corresponding to a first diameter and filaments in the transverse direction of the machine corresponding to a second diameter, which are interwoven to form a pattern of knuckles and baskets; the web having filaments in the transverse direction corresponding to a third diameter alternating with the filaments in the transverse direction of the second diameter to form support members virtually centrally located at the bottom of the baskets. 12. A papermaking fabric having one side of sheet and one side of machine, same comprising: a system of filaments MD selectively interwoven with a CD filament system having at least two subsets of minor and larger filaments, wherein the MD filaments form and floating yarns on the MD side of the sheet having a minimum length of seven filaments of the CD system, and the smaller CD filaments form floating yarns on the machine side in CD direction having a minimum length of four filaments of the MD system whereby the shed forms a plurality of basket-type depressions on the leaf side of the yarn. cloth. The papermaking fabric according to claim 12, wherein the smaller CD-filaments are woven in a repeating pattern of passing below four and above one MD filament. The papermaking fabric according to claim 12 wherein the larger CD filament is woven in a repetitive pattern of above one, below one, above one and below two MD filaments. 15. The fabric according to claim 12, wherein the knuckles formed by the CD filaments of smaller diameter coincide with the knuckles of the larger diameter CD filaments. The fabric according to claim 15 wherein the smaller CD filaments are woven in a pattern repetitive to pass under four MD filaments and above one MD filament. 17. The papermaking fabric having one side of sheet and one side of machine; composed of: a system of selectively woven MD filaments with a CD filament system, in which the MD filaments form floating yarns on the leaf side in the MD direction that possess a minimum number of floating filaments of seven filaments in the CD system; the CD filaments have at least two subsets of filaments that have filaments of greater and smaller diameter; CD filaments of larger diameter define only knuckles on the leaf side; and the smaller diameter CD filaments define only knuckles on the sheet side and floating yarns on the machine side; as a result of which the shed forms a plurality of depressions in the sheet side of the fabric. The fabric according to claim 17 in which the knuckles formed by the CD filaments of smaller diameter coincide with the knuckles formed with the larger diameter CD filaments.