MXPA99011255A - Differential density cellulosic structure and process for making same - Google Patents

Abstract

A differential density single lamina web of cellulosic fibers is disclosed. The web comprises at least two pluralities of micro-regions disposed in a non-random and repeating pattern:a first plurality of high density regions and a second plurality of low density regions. The high density regions comprise cellulosic fibers comprising fluid latent indigenouspolymers (FLIP), such as hemicelluloses and lignin. The fibers of the high-density regions are FLIP-bonded, i.e., bonded together by a process of softening, flowing and immobilization of the FLIP between the cellulosic fibers of the high density regions. The process for making the web comprises the steps of providing a plurality of papermaking fibers comprising FLIP;providing a macroscopically monoplanar papermaking belt (20) having a web-facing surface (21) and deflection conduits (40);depositing the plurality of the cellulosic fibers on the papermaking belt (20) to form a web;heating the web to a temperature sufficient to cause the FLIP contained in a first portion associated with the web-facing surface of the belt to soften;impressing the web-side suface of the belt into the web (21);immobilizing the flowable FLIP and creating FLIP-bonds between the fibers comprising the first portion of the web.

Description

DIFFERENTIAL DENSITY CELLULOSIS STRUCTURE AND PROCESS TO DEVELOP THE SAME FIELD OF THE INVENTION The present invention relates to processes for making cellulosic, absorbent, soft and strong wefts. More particularly, this invention relates to cellulosic webs having high density micro-regions and low density micro-regions, and to the processes and apparatus for making these cellulosic webs.

BACKGROUND OF THE INVENTION Paper products are used for a variety of purposes. Paper towels, facial tissues, toilet paper and the like are in constant use in modern industrialized societies. The high demand for these paper products has created a demand for improved versions of the products. If paper products such as paper towels, facial tissues, toilet paper and the like are going to perform their proposed tasks and find wide acceptance, they must possess certain physical characteristics. Among the most important of these characteristics are the resistance, softness and absorbency. Resistance is the ability of a plot of P9 7 paper to retain your physical integrity during use. Softness is the pleasant tactile perception that users perceive when they use paper for their proposed uses. Absorbency is the characteristic of paper that allows paper to pick up and hold fluids, particularly water and aqueous solutions and suspensions. Not only is it important the absolute amount of fluid that a certain amount of paper will hold, but also the speed at which the paper will absorb the fluid. There is a well-established relationship between the strength and the density of the weft. Therefore, an effort has been made to produce highly densified paper webs. One of these methods, known as the CONDEBELT® technology, is described in U.S. Patent No. 4,112,586 issued September 12, 1978; U.S. Patent Nos. 4,506,456 and 4,506,457 both issued on March 26, 1985; U.S. Patent No. 4,899,461 issued February 13, 1990; U.S. Patent No. 4,932,139 issued June 12, 1990; U.S. Patent No. 5,594,997 issued January 21, 1997, all prior patents granted to Lehtinen; and U.S. Patent No. 4,622,758 issued November 18, 1986 to Lehtinen et al .; Patent of the P947 United States No. 4,958,444 issued September 25, 1990 to Rautakorpi et al. All prior patents are granted to Valmet Corporation of Finland and are incorporated herein by reference. The CONDEBELT® technology uses a pair of movable endless bands, to dry the web that is pressed and moved between, and parallel to, the webs. The bands have different temperatures. A thermal gradient drives the water from the relatively heated side, and the water condenses into a fabric on the relatively cold side. A combination of temperature, pressure, moisture content of the weft, and a residence time cause the hemicelluloses and lignin contained in the paper fibers of the weft to soften and flow, thus interconnecting and "welding" the fibers together litter bins. While CONDEBELT® technology allows the production of a highly densified strong paper suitable for packaging needs, this method is not suitable for producing a strong and at the same time soft paper suitable for consumer disposable products, such as facial tissue , paper towel, napkins, toilet paper and the like. It is well known in the art that increasing the density of paper decreases the characteristics of absorbency and softness of the paper.

The cellulosic structures currently elaborated by the present assignee contain multiple micro-regions more typically defined by differences in density. The cellulosic structures of differential density are created first, by applying vacuum pressure to the wet web associated with a molding web, thereby diverting a portion of the paper fibers, to generate the low density regions, and second, by pressing the portions of the web comprising the paper fibers, not deflected, against a hard surface, such as a surface of a Yankee dryer drum, to produce the high density regions. The high-density micro-regions of these cellulosic structures generate resistance, while the low-density micro-regions contribute to softness, volume and absorbency. These cellulosic structures of differential density can be produced using the paper, pass-air drying bands comprising a reinforcing structure and a resinous framework, bands which are described in commonly assigned U.S. Patent No. 4,514,345 issued. Johnson et al., April 30, 1985; U.S. Patent No. 4,528,239 issued to Trokhan on July 9, 1985; U.S. Patent No. 4,529,480 issued to Trokhan on July 16, 1985; U.S. Patent No. 4,637,859 issued to Trokhan on January 20, 1987; U.S. Patent No. 5,334,289 issued to Trokhan et al. on August 2, 1994. The above patents are incorporated herein by reference, Typically, as is well known in the papermaking art, wood used in papermaking inherently comprises cellulose. (approximately 45%), hemicelluloses (approximately 25-35%), lignin (approximately 21-25%) and extractables (approximately 2-8%). G. A. Smook, Handbook for Pulp & Paper Technologists, TAPPI, 4 S printing, 1987, pages 6-7, book that is incorporated herein by reference. Hemicelluloses are polymers of hexoses (glucose, mannose and galactose) and pentoses (xylose and arabinose). Id., At 5. Lignin is a highly polymerized amorphous substance comprising an outer layer of a fiber. Id., At 6. The extractables are a variety of diverse substances present in the native fibers, such as resin acids, fatty acids, turpenoid compounds and alcohols. Id. As used herein, hemicelluloses, lignin and polymeric extractables inherently present in cellulosic fibers are defined by a generic term "native, latent, fluid polymers" or "FLIP".

Hemicelluloses, lignin and polymeric extractables are typically a part of the cellulosic fibers, but can be added independently to a plurality of cellulosic papermaking fibers, or the weft, if desired, as part of a process for making paper. Traditional conditions for papermaking, such as the temperature of the weft and duration of the application of pressure (ie, a residence time) during transfer from the wet weave to the Yankee dryer are not suitable to cause the FLIPs they soften and flow in regions of high density. Therefore, it is an object of the present invention to provide a new papermaking process for making strong, soft, absorbent cellulosic structures comprising high density micro-regions and low density micro-regions; the high-density micro-regions that are formed, at least partially, by a process of smoothing the native, latent, fluid polymers inherently contained in cellulosic papermaking fibers, allowing the native, latent, fluid polymers to flow, interconnecting from this mode the adjacent papermaking fibers of the high-density micro-regions, and then immobilizing the native, latent, fluid polymers in the high-density micro-regions. It is yet another object of the present invention to provide a cellulosic structure having a plurality of high density micro-regions and a plurality of low density micro-regions, the plurality of high density micro-regions comprising pulped cellulose fibers, to native, latent, fluid polymers.

SUMMARY OF THE INVENTION An individual sheet web of cellulosic fiber differential density of the present invention comprises at least two pluralities of micro-regions placed in a non-random and repeating pattern; a first plurality of high density micro-regions and a second plurality of low density micro-regions. The high density microregions comprise cellulosic fibers comprising native, latent, fluid polymers (FLIP), such as hemicelluloses, lignin and polymeric extractables. The fibers of the high density micro-regions are linked to the native, latent, fluid polymers (bound to FLIP), that is, joined together by a smoothing process, to the point of being fluid, and then the immobilization of the FLIPs between the juxtaposed and adjacent cellulose fibers of the high density micro-regions. In one embodiment, the high density micro-regions comprise a macroscopically monoplanar and pattern network area, essentially continuous, and the low density micro-regions comprise a plurality of discrete domes dispersed throughout, encompassed by, and isolated from one another by a network area. In another embodiment, the low density micro-regions comprise an essentially continuous and pattern network area; and the high density micro-regions comprise a plurality of discrete knuckles circumscribed by the network area and dispersed throughout its length. In a process aspect of the present invention, the process for making the individual sheet, cellulosic fiber differential density film comprises the following steps: providing a plurality of paper cellulosic fibers, comprising FLIP; providing a macroscopically monoplanar and fluid-permeable forming web having a weft-side surface, a back surface opposite to the weft-side surface, and deflection conduits extending between the weft-side surface and the back surface; placing the plurality of cellulosic fibers in the forming web to form a "web comprising a first portion of the cellulosic fibers associated with the weft side surface, and a second portion of the cellulosic fibers corresponding to the deflection passages. heating the first portion of the weft for a period of time and at a temperature sufficient to cause the FLIP contained in the first portion to soften, print the surface of the weft side of the formation band in the weft, densifying this the first portion of the cellulosic fibers and causing the FLIPs to flow and interconnect those cellulosic fibers that are mutually juxtaposed in the first portion, immobilize the FLIP fluids and create bonds by FLIP between the cellulosic fibers mutually juxtaposed in the first portion. of immobilizing FLIP fluids and creating FLIP unions can be achieved either by one or a combination of the following: drying at least a first portion of the web, cooling at least the first portion of the web, releasing the pressure caused by the printing step of the web side surface of the web in the plot. The step of printing the surface of the weft side of the forming web can be achieved by pressing the weft in association with the paper web between a first mutually opposite press member having a first press surface and the second press member. having a second press surface, the first and second press members that are pressed together. The press surfaces are parallel to each other and mutually opposite. The web and the paper web are interposed between the first and second press surfaces such that the first press surface makes contact with the web, and the second press surface contacts the back surface of the web. Preferably, the step of heating the first portion and the printing step are performed concurrently. The process may further comprise the step of applying a fluid pressure differential to the web such as to leave the first portion of the cellulosic fibers on the weft side surface of the forming web while deflecting the second portion of web. the cellulosic fibers in the deflection conduits, and remove a portion of the liquid carrier from the weft. Preferably, the step of applying a first pressure differential is performed subsequent to the step of draining the liquid carrier through the forming band and before the step of heating the first portion.

The process of the present invention can additionally utilize a macroscopically monoplanar molding band, separated from the forming band; then the process further comprises the step of transferring the web from the forming web to the molding web. In this case, the steps of applying a differential of fluid pressure, heating, printing, drying and cooling are preferably performed while the web is in association with the molding band. - BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side elevation, schematic view of an exemplary embodiment of a continuous papermaking process of the present invention, showing a web that is heated by a heating wire and press between a first couple of press members. Figure 1A is a side elevational, schematic view of another exemplary embodiment of a continuous papermaking process of the present invention, showing a web that is heated by a Yankee drying drum and pressed between the drum of Yankee drying and a pressing band. Figure IB is an elevational, lateral, fragmentary, schematic view of the process of the present P947, which shows a web that is pressed between a Yankee drying drum and the press rolls. Figure 2 is a top plan view, schematic, of a paper web used in the process of the present invention, which has a network of the weft side, essentially continuous and deflection conduits, discrete. Figure 2A is a fragmentary, schematic, cross-sectional view of the paper web taken along the lines 2A-2A of Figure 2, and showing a cellulosic web in association with the paper web that is pressed between a first member of the press and a second member of the press. Figure 3 is a top plan view, schematic, of the paper web comprising a frame formed by discrete protuberances encompassed by an essentially continuous area of deflection conduits, the discrete protuberances having a plurality of discrete deflection passages. in the same. Figure 3A is a fragmentary, schematic, cross-sectional view of a paper web taken along lines 3A-3A of Figure 3 and showing a cellulosic web in association with the paper web that is pressed between a first member of the press and a P947 second member of the press. Figure 4 is a top plan view, schematic of a prophetic paper web of the present invention. Figure 4A is a fragmentary, schematic cross-sectional view of the paper web taken along lines 4-4 of Figure 4.

DETAILED DESCRIPTION OF THE INVENTION The papermaking process of the present invention comprises a number of steps or operations that occur in the general sequence of time as noted below. However, it should be understood that the steps described below are proposed to assist a reader in understanding the process of the present invention, and that the invention is not limited to processes with only a certain number or arrangement of steps. In this regard, it is pointed out that it is possible, and in some cases still preferable, to combine at least some of the following steps so that they are performed concurrently. Likewise, it is possible to separate at least some of the following steps in two or more steps without departing from the scope of this invention. Figures 1 and 1A are schematic, simplified representations of two modes of a P947 continuous process for papermaking of the present invention. As used herein, the term "paper band 20", or simply "band 20", is a generic term that includes both a forming band 20a and a forming band 20b, on the basis of bands shown in the preferred form of endless bands in Figures 1 and 2. The present invention can use the individual paper band 20 which "functions as both the forming band 20a and the molding band 20b (this embodiment is not shown in the figures of the present invention. , but can be easily visualized by one skilled in the art.) However, the use of separate bands 20a and 20b is preferred, It will be understood by one skilled in the art that the present invention may use more than two bands.; for example, a drying band (not shown) can be used, separated from the forming band 20a and the molding band 20b. As used herein, the term "X-Y plane" designates a plane parallel to the macroscopically monoplanar, general plane of the paper web, and the term "Z-direction" designates a direction perpendicular to the X-Y plane. The first step of the papermaking process is to provide a plurality of cellulosic papermaking fibers, preferably suspended in a carrier.

P947 fluid. More preferably, a plurality of cellulosic paper fibers suspended in a fluid carrier comprises an aqueous dispersion of paper fibers. Equipment for preparing the aqueous dispersion of paper fibers is well known in the papermaking art, and therefore, is not shown in Figures 1 and 2. The aqueous dispersion of papermaking fibers is provided to a main box 15. A main, individual box is shown in Figures 1 and 2. However, it should be understood that there may be multiple main boxes in alternative arrangements of the papermaking process of the present invention. The main box (s) and the equipment for preparing the aqueous dispersion of paper fibers are typically of the type described in U.S. Patent No. 3,994,771, issued to Morgan and Rich on November 30, 1976, which is incorporated herein by reference. The preparation of the aqueous dispersion and the characteristics of the aqueous dispersion are described in greater detail in U.S. Patent No. 4,529,480 issued to Trokhan on July 16, 1985, which is incorporated herein by reference. As explained hereinabove, typically a wood pulp used in papermaking inherently comprises cellulose, hemicelluloses, lignin and extractables. As a result of P947 mechanical and / or chemical treatment of the wood to produce pulp, portions of hemicelluloses, lignin, and extractables are removed from the paper fibers. It is believed that when the fibers are put together during a process for making paper, the hydroxyl groups of the cellulose are bonded together by hydrogen bonds. Smook, infra, in 8. Therefore, the removal of most lignin, while retaining substantial amounts of hemicelluloses, is generally seen as a desirable occurrence, since the removal of lignin increases the absorbency of the lignin. fibers. A "beating" or "refining" process that causes the removal of the primary fiber walls also helps to increase the fiber's absorbency (Id., At 7), as well as increasing fiber flexibility. Although some portion of the native, latent, fluid, or "FLIP" polymers, as defined hereinbefore, are removed from the papermaking fibers during the mechanical and / or chemical treatment of the wood, the paper fibers retain a portion still. of FLIPs even after chemical treatment. The claimed invention allows the advantageous use of those FLIPs that have traditionally been seen as undesirable in the process for making paper. Of course, hemicelluloses, lignins and polymeric extractables can be added to P947 paper fibers or a weft, if desired, during a process to manufacture paper. The hemicelluloses, lignin and polymeric extractables, which are part of the papermaking fibers, are normally present in the cellulosic fibers in a non-fluid condition. However, under certain conditions defined by temperature, pressure, moisture content, FLIPs can soften and flow. The term "FLIP" reflects the common quality of these substances that will normally be hardened or immobilized, and to soften and become fluid with certain imposed conditions. In an example embodiment shown in Figure 1, the aqueous dispersion of the paper fibers containing FLIP and supplied by the main box 15 is distributed to the paper web 20, such as the forming band 20a, to carry out the second. step of the process to make paper. In Figures 1 and 1A, the forming band 20a is supported by a front roll 28a and a plurality of return rolls designated 28b and 28c. The forming band 20a is driven in the direction indicated by the directional arrow A by a conventional driving means well known to a person skilled in the art, and therefore not shown in Figures 1 and 1A. They can also be associated with the process for P947 manufacture paper shown in Figures 1 and 1A, optional auxiliary units and devices that are commonly associated with papermaking machines and forming belts, including: forming boards, hydrofoils, vacuum boxes, rollers tension, support rolls, wire cleaning showers, and the like, which are conventional and well known in the papermaking art, and therefore are also not shown in Figures 1 and 1A. The preferred forming band 20a is a macroscopically monoplanar, fluid permeable band. The forming web 20a may comprise a forming mat well known to those skilled in the papermaking art. With reference to Figures 2-3A, the forming band 20a may comprise a reinforcing structure 50, permeable to air and a frame 30 attached to the reinforcing structure 50. Preferably, the frame 30 is resinous. The reinforcing structure 50 has a side 51 that faces the weft and a side 52 that faces the machine and is opposite the side 51 that faces the weft. The side 51 facing the web defines an XY plane of the forming web 20a, and the XY plane that is perpendicular to a Z direction. The framework 30 may comprise a plurality of discrete protuberances 35 attached to the reinforcing structure 50 and that extend from the P947 itself, as shown in Figures 3 and 3A. Alternatively, the structure 30 can be essentially continuous, as shown in Figure 2. In the forming band 20a comprising the plurality of discrete protuberances 35, each of the protuberances 35 has an upper surface 36, a base surface 37, and walls 38 that separate and interconnect the upper surface 36 and the base surface 37, as shown in Figures 3 and 3A. A plurality of upper surfaces 36 define a surface 21 of the weft side, and a plurality of base surfaces 37 define a rear surface 22 of the forming web 20a. This type of training band 20a is described in commonly assigned U.S. Patent No. 5,245,025, issued to Trokhan et al., On September 14, 1993, and U.S. Patent No. 5,527,428 issued to Trokhan et al. al., on June 18, 1996, all of which are incorporated herein by reference. As shown in Figure 3, the band 20 comprised of the plurality of discrete protuberances 35 has essentially continuous ducts 70 extending between the weft surface 21 and the back surface 22 of the strip 20. In addition to the ducts 70, the band 20 may have a plurality of P947 discrete, deflection conduits 75 placed on the protrusions 35 and also extending between the weft-facing surface 21 and the rear surface 22 of the forming web 20a. The forming band 20a comprising both the essentially continuous conduits 70 and the discrete conduits 75 have high velocity flow permeable liquid zones and low velocity flow permeable liquid zones defined respectively by the deflection conduits 70, essentially continuous and the discrete ducts 55. When the liquid carrier and the entrained cellulosic fibers are deposited in this forming band 20a, the liquid carrier is drained through the forming band 20a in two simultaneous stages, a high-speed flow stage and a low flow rate stage, as described in greater detail in commonly assigned U.S. Patent No. 5,245,025 and referenced above. The band 20 containing a substantially continuous frame 30 can also be used as the forming band 20a. However, this type of band 20 having essentially continuous frame 30 should preferably be used as the molding band 20b, as will be discussed in more detail below. The type of band 20 having the frame 30 essentially continuous is P947 describes in commonly assigned U.S. Patent No. 5,514,345, referenced above, issued to Johnson et al. on April 30, 1985; U.S. Patent No. 4,528,239 issued to Trokhan on July 9, 1985; U.S. Patent No. 4,529,480 issued to Trokhan on July 16, 1985, all of which are incorporated herein by reference. One skilled in the art will understand that if the forming web 20a comprises a forming mesh well known in the art, and therefore not shown, the surface of the forming mesh that makes contact with the web comprises the surface 21 on the web side. plot that ~ defines the XY plane, the opposite surface of the forming mesh comprising the back surface 22, and the hollow spaces between the filaments of the forming mesh comprise deflection conduits extending between the surface 21 of the weft side and the surface 22 back of the forming mesh. The next step is to deposit the plurality of pulp fibers, cellulosic, preferably suspended in the fluid carrier, on the surface 21 of the weft side of the forming web 20a, and preferably draining the fluid carrier through the forming web 20a , to form an embryonic web 10 of the paper fibers in the forming web 20a. How it is used P947 in the present, the "embryonic weft" is the weave of paper, cellulose fibers that undergo rearrangement in band 20 during the course of the papermaking process. The characteristics of the embryonic web 10 and the various possible techniques for forming the embryonic web 10 are described in commonly assigned U.S. Patent No. 4,529,480, mentioned above, which is incorporated herein by reference. In the process shown in Figures 1 and 1A, the embryonic web 10 is formed from cellulosic fibers suspended in the liquid carrier between the anterior roller 28a and the return roller 28b by depositing the cellulosic fibers suspended in the liquid carrier in the liquid carrier. band 20a and remove a portion of the liquid carrier through the forming band 20a. Conventional vacuum boxes, forming boards, hydrofoils and the like which are not shown in Figures 1 and 1A are useful in effecting the removal of the liquid carrier. For clarity and consistency, as used herein, the frame 10, in spite of the stages of its processing, is referred to by the same number "10", that is, the "embryonic" frame 10, "intermediate" 10 frame. , frame 10"presecada", and so on. The finished product, a paper web, is referred to by the number P947"10 *". As shown in Figures 2A and 3A, the embryonic web 10 formed in the forming web 20a comprises a first portion 11 of the cellulosic fibers and a second portion 12 of the cellulosic fibers. The first portion 11 is the portion that is physically associated with the surface 21 of the weft side of the web 20, or that corresponds to the surface 21 of the weft side in the Z direction. The second portion 12 is a portion that is not physically associated with the surface 21 of the web side of the web 20, or which corresponds in the Z direction to either (1) the continuous deflection ducts 70, when the band 20 having the frame 30 comprising the plurality of discrete protuberances 35 (Figure 3A), or (2) the discrete deflection ducts 40, when the band 20 having the essentially continuous frame 30 is used (Figure 2A). One skilled in the art will understand that the same fiber can comprise (and in many cases will comprise) the first portion 11 and the second portion 12, ie, at least a part of the fiber can correspond in the Z direction to the surface 21 of the side of the frame, while the other part or parts of the same figure may correspond in the Z direction to the conduit or deflection conduits. When the training band 20a is used that P947 comprises the deflection conduits 70, essentially continuous, the second portion 12 of the embryonic web 10 comprises an essentially continuous network and pattern (corresponding to the direction Z to the area of the essentially continuous conduits 70) preferably having a basis weight relatively high; and the first portion 11 of the embryonic web comprises a plurality of discrete knuckles (corresponding to the plurality of discrete protuberances 35) that preferably have a relatively low basis weight. The first portion 11 comprising the plurality of discrete knuckles is circumscribed and adjacent to the second portion 12. The first portion 11 comprising the plurality of discrete knuckles is preferably presented in a non-random repeat pattern corresponding to the preferred pattern not randomization of the plurality of discrete protuberances 35 of the forming band 20a. As shown in Figures 3 and 3A, the forming band 20a can have both the essentially continuous ducts 70 and the discrete ducts 75 placed in the discrete protuberances 35. In the latter case, the embryonic pattern 10 comprises a third portion 13 that preferably has an intermediate basis weight relative to the basis weight of the first portion 11 and the basis weight of the second portion 12. The third P947 portion 13 is presented in a preferred non-random repeat pattern corresponding to discrete ducts 75. Third portion 13 is juxtaposed with, and is preferably circumscribed by first portion 11. U.S. Patent No. 5,628,876 commonly assigned, granted on May 13, 1997 in the name of Ayers et al. describes a semi-continuous pattern of the frame 23 that can also be used in the band 20 for the purposes of the present invention. The above patent is incorporated herein by reference. During the formation of the embryonic web 10 and after the embryonic web 10 is formed, the embryonic web travels with the forming web 20a in the direction indicated by the directional arrow A (Figures 1 and 1A) to be placed in the vicinity of the training band 20b. Alternatively, the single band 20 can be used as both the forming band 20b and the molding band 20b. The next step is to transfer the embryonic plot from the forming band 20a to the surface 21 of the weft side of the molding band 20b. Conventional equipment, such as the vacuum collection shoe 27a (Figures 1 and 1A), can be used to achieve handover. As noted above, in a P947 embodiment of the process of the present invention, the individual band 20 can be used both as the forming band 20a and the molding band 20b. In the latter case, the handover step is not applicable, as will be readily appreciated by one skilled in the art. Also, one skilled in the art will understand that the vacuum collection shoe 27a shown in Figures 1 and 1A is a preferred means for transferring the web 10 of the forming web 20a to the molding band 20b. Other equipment, such as an interchangeable band or the like (not shown) can be used for the purpose of transferring the web 10 from the forming web 20a to the molding web 20b. U.S. Patent No. 4,440,579 commonly assigned issued on April 3, 1984 to Wells et al,. It is incorporated as a reference to the present. The preferred molding web 20b is a macroscopically monoplanar, fluid permeable web. One embodiment of the preferred molding band is shown in Figures 2 and 2A. The molding band 20b shown in Figures 2 and 2A preferably comprises the air-permeable reinforcing structure 50 and the essentially continuous, preferably continuous, resin framework 30, attached to the reinforcing structure 50 and extending from the same The surface 21 of the weft side of the drying band 20b comprises a network on the side of the P947 essentially continuous web defining weft-side openings of the discrete deflection ducts 40, and the back surface 22 of the molding band 20b comprises a rear network defining the rear openings of the ducts 40. As explained above , the network on the frame side defines the XY plane, and the Z direction is a direction perpendicular to the XY plane. The commonly assigned U.S. Patent No. 4,239,065, issued December 16, 1980 in the name of Trokhan and incorporated herein by reference, discloses another type of paper web 20 that can be used in the present invention. The anterior band has no resinous framework, and the surface 21 of the weft side of the anterior band is defined by co-planar paths distributed in a predetermined pattern throughout the length of the band. Another type of web that can be used as the paper web 20 in the process of the present invention is described in the European Patent Application having the Publication Number: 0 677 612 A2, filed on 12.04.95. While in the present invention a woven element is preferred for the reinforcement structure 25 of the paper web 20, a paper web 20 can be made using a felt as a reinforcing structure, as shown in FIG.

P947 discloses in U.S. Patent No. 5,556,509 issued September 17, 1996 to Trokhan et al., And patent applications: Serial No. 08 / 391,372 filed on 2/15/95 in the name of Trokhan et al. to the. and titled: "Method of Applyng to Curable Resin to Substrate for Use in Papermaking"; Serial No. 08 / 461,832 filed 06/05/95 in the name of Trokhan et al. and titled: "Web Patterning Apparatus Comprising to Felt Layer and Photosensitive Resin Layer". This patent and applications are assigned to The Procter & Gamble Company and are incorporated herein by reference. In the embodiments illustrated in Figures 1, 1A and IB, the molding band 20b travels in the direction indicated by the directional arrow B. In Figure 1, the molding band 20b passes around the return rolls 29c, 29d, a printing separation roller 29e, return rollers 29a and 29b. In Figure 1A, the molding band 20b passes around the return rolls 29a, 29b, 29c, 29d and 29g. In both Figure 1 and 1A, an emulsion distribution roller 29f distributes an emulsion in the molding band 20b from 7 of an emulsion bath. The circuit around which the molding band 20b also preferably includes a means for applying a fluid pressure differential to the weft 10, which in the preferred embodiments P947 of the present invention comprises a vacuum collection shoe 27a and a vacuum box 27b. The circuit may also include a pre-dryer (not shown). In addition, water showers (not shown) are preferably used in the papermaking process of the present invention to clean the molding band 20b from any paper fiber, adhesive and the like, which may remain attached to the molding band. 20b after it has traveled through the final step of the papermaking process. Associated with the molding band 20b, and also not shown in Figures 1 and 1A, are several additional support rolls, return rolls, cleaning means, driving means, and the like commonly used in paper making machines and well known to those skilled in the art. The next step is to apply a fluid pressure differential to the embryonic web 10 to divert at least a portion of the paper fibers into the discrete deflection conduits of the molding band 20b and to remove a portion of water from the embryonic web 10, thereby forming an intermediate frame 10. The step of applying a fluid pressure differential is optional, although highly desirable. The deflection serves to rearrange the paper fibers in the weft 10 in the desired structure. The step of applying a differential of P947 fluid pressure to the weft 10 and the deflection of the fibers in the deflection conduits 40 of the molding band 20b, which can be carried out in the vacuum collection shoe 27a and the vacuum box 27b, is described with greater detail in the United States Patent No. 5,098,522, commonly assigned, granted to Smurkoski et al. on March 24, 1992 and incorporated herein by reference. The next step in the process of the present invention comprises heating the first portion of the weft 10, that is, that part of the inlet 10 that is in association with the surface 21 of the weft side of the web 20 (Figures 2A and 3A). It is believed that heating the first portion 11 to a sufficient temperature and for a sufficient period of time will cause the FLIPs contained in the paper fibers of the first portion 11 to soften. Then under pressure, the softened FLIPs become fluid and capable of interconnecting those paper fibers that are mutually juxtaposed in the first portion 11. The heating step of the first portion 11 can be achieved by a variety of methods known in the art. . For example, as shown schematically in Figure 1, the first portion 11 can be heated by a heating mat 80. The heating mat 80 travels around the rollers.

P947 return 85a, 85b, 85c and 85d in the direction indicated by the directional arrow C. The heating mat 80 is in contact with the first portion 11 of the weft 10. The heating mat 80 is heated by a heating apparatus 85. This principal arrangement is described in U.S. Patent No. 5,594,997 issued to Jukka Lehtinen on January 21, 1997 and assigned to Valmet Corporation (of Finland). Alternatively or additionally, the weft 10 can be heated by steam, as described in U.S. Patent No. 5,506,456 issued to Jukka Lehtinen on March 26, 1985 and granted to Valmet Corporation (of Finland). Both prior patents are incorporated herein by reference. As one skilled in the art will appreciate, the molding band 20b will preferably have a hollow volume suitable for taking a liquid displaced from the weft 10. Alternatively, the molding band 20b can be "backed up" by another band which, alone or in combination with the molding band 20b, it has the appropriate hollow volume. The temperature application to the frame 10 can be distributed by zones (not shown). For example, in a first zone, the web is rapidly heated to a temperature TI sufficient to cause the FLIPs contained in the first portion 11 of the web 10 to soften and flow; and in the second zone the frame 10 is P947 maintains only at the temperature Ti. This "zonal" application of temperature allows for better time control during which FLIPs are in a smoothed and fluid condition, and can provide savings in relation to energy. Figures 1A and IB show embodiments of the process of the present invention, in which the heating step is achieved in the Yankee drying drum 14. In the embodiments shown in Figures 1A and IB, the drum surface 14 Yankee is a heating surface. The next step is to print the surface 21 of the web side of the web 20 in the web 10. The printing step is preferably achieved by subjecting the web 10 associated with the web 20 and web 20 to a pressure between two web members. mutually opposed press. A first press member 61 and a second press member 62, as best shown in Figures 2A and 3A. The first press member 61 and the second press member 62 have a first press surface 61 * and a second press surface 62 *, respectively. The first and second press surfaces 61 * and 62 * are parallel to the XY plane and mutually opposite to the Z direction. The weft 10 and the band 20 are interposed between the first press surface 61 * and the second press surface 62 * such that P947 the first press surface 61 * makes contact with at least the first portion 11 of the weft 10, and the second press surface 62 * makes contact with the rear surface 22 of the drying strip 20b. Of course, in some embodiments of the process of the present invention (specifically, in the embodiments in which the deviation of the paper fibers from the second portion 12 in the deflection conduits has not occurred) the first press surface 61 * can do contact with both the first portion 11 and the second portion 12 of the frame 10, as shown schematically in Figure 3A. The first press member 61 and the second press member 62 press each other in the direction Z (in Figures 2A and 3A, the pressure is indicated "esqatically by the directional arrows P.) The first press surface 61 * presses the first portion 11 against the surface 21 that faces the web 20, densifying in this way the first portion 11 causing the cellulosic fibers of the first portion 11 to fit together under the pressure P. As a result of the application of the pressure P, a resulting area of contact between the fibers of the first portion 11 is increased, and the smoothed FLIPs contained in the fibers of the first portion 11 become fluid and interconnect the adjacent fibers and mutually P947 juxtaposed from the first portion 11. In an alternative embodiment shown in Figures 1A and IB, the printing step is achieved in the Yankee drying drum 14. In this case, the surface of the Yankee drying drum 14 comprises the first press surface 61 *. Under the traditional papermaking conditions, when the web 10 is transcribed to the Yankee drying drum 14 using the print separation roller 29e (Figure 1), the residence time during which the web 10 is under pressure between the surface of the Yankee drum 14 and the printing roller 29e is too short to provide full advantage of the application of the pressure and effectively densify the fibers of the first portion 11, even if the first portion 11 contains the smoothed FLIP. The modalities shown in Figures 1A and IB allow to press the frame 10 for a much longer period of time and to receive full advantage of the smoothed and fluid FLIPs. In Figure 1A, the weft 10 and the molding band 20b are pressed between the surface of the drum 14 of the Yankee dryer and a pressing band 90 having a first side 91 and a second side 92 opposite the first side 91. The surface of the drum 14 Yankee comprises the first press surface 61 * which makes contact with the first portion 11 of the weft 10; and the first side 91 of P947 the pressing band 90 comprises the second press surface 62 * which makes contact with the rear surface 21 of the molding band 20b. The pressing band 90 is preferably an endless belt shown schematically in Figure 1A as it travels around the return rolls 95a, 95b, 95c and 95d in the direction indicated by the directional arrow D. Figure IB shows a variation of the modality shown in Figure la. In Figure IB, the weft 10 and the molding band 20b are pressed between the surface of the Yankee drum 14 and a series of pressing rollers 60. Similar to the embodiment shown in Figure 1A, and the embodiment shown in Figure IB , the surface of the Yankee drum 14 is the first press surface 61 * which makes contact with the first portion of the weft 10. The surfaces of the press rolls 60 are the second press surface 62 * which makes contact with the rear surface 21 of the molding band 20b. Each of the pressing rolls 60 is preferably a resilient roll, elastically deformable under the pressure applied to the surface of the Yankee drying drum 14. Each of the pressing rolls 60 is rotated in the direction indicated by the directional arrow E. Preferably, the pressure in each of the pressing rolls 60 is normally applied to the P947 surface of the Yankee drying drum 14, that is, toward the center of rotation of the Yankee drying drum 14. Figure IB shows the second press surface 62 * comprised of three consecutive pressing rollers 60 which apply pressure to the rear surface 21 of the molding band 20b; a first pressing roller 60A which applies a pressure Pl, a second pressing roller 60b which applies a pressure P2, and a third pressing roller 60c which applies a pressure P3. The use of a plurality of press rolls 60 allows different pressure to be applied in discrete steps (Figure IB), for example, Pl < P2 < P3 or Pl > P2 > P3 > , or any other desirable combination of Pl, P2, P3. One skilled in the art will understand that the number of pressing rolls 60 may differ from that shown in Figure IB as an illustration of a possible embodiment of the process of the present invention. Similarly, to the "zonal" application of temperature, explained above, the use of a plurality of pressing rollers 60 that apply differential pressure in discrete steps improves flexibility by optimizing the conditions that cause FLIPs to soften and flow. Preferably, the heating and pressing steps of the frame 10 are performed concurrently. In the latter case, the first surface of P947 press 61 * comprises preferably or is associated with a heating element. In Figures 2A and 3A, for example, the first press surface 61 * comprises the heating mat 80, according to the embodiment of the process shown in Figure 1. Figures 1A and IB, the first press surface 61 * it comprises the heated surface of the Yankee drying drum 14. It is believed that the simultaneous pressing and heating of the first portion 11 of the weft 10 facilitates the smoothing and flowability of the FLIPs contained in the cellulosic fibers of the first portion 11 and improves the densification of the first portion 11 of the weft 10. As noted above, under the traditional papermaking conditions, when the web 10 is transferred to the Yankee drying drum 14, the residence time during which the "web 10" is under pressure between the surface of the drum 14 of Yankee drying and the printing separation roller 29e_ (Figure 1) is too short to effectively cause the FLIPs to soften, although some densification occurs in the transfer of the screen 10 to the surface of the Yankee dryer in the separation between the surface of the Yankee drying drum 14 and the surface of the printing separation roller 29e, the traditional papermaking conditions l do not allow to keep the frame 10 low P947 pressure for more than approximately 2-5 milliseconds. At the same time, it is believed that for the purposes of causing the smoothed FLIPs to flow and interconnect the fibers in the first portion 11, the preferred residence time should be at least about 0.1 seconds (100 milliseconds). In contrast to the traditional papermaking process, the embodiments shown in Figures 1A and IB allow a significant increase in residence time during which the weft 10 is subjected to the combination of temperature and pressure sufficient to causing the FLIP to become fluid and interconnect the paper fibers in the first portion 11 (pressed) of the weft 10. In accordance with the process of the present invention, the preferred residence time is greater than about 1.0 seconds. The most preferred residence time is in the range of between about 12 seconds and about 10 seconds. One skilled in the art will readily appreciate that at a given speed of the paper web 20, the residence time is directly proportional to the length of a route to which the web 10 is under pressure. Whereas the first portion 11 of the Weft 10 is subjected to the pressure between the first press member 61 and the surface 21 of the weft side of the web 20, the P947 second portion 12 of the weft 10 is not subjected to pressure, thereby retaining the absorbency and softness characteristics of the essentially non-densified web. As noted above, if the deviation of the paper fibers from the second portion 12 in the deflection conduits has not occurred, the first press surface 61 * can contact both the first portion 11 and the second portion 12. of the frame 10. Even in the latter case, the second portion 12 is not subjected to pressure as the first portion is, as best shown in Figures 2A and 3A. Prophetically, exemplary preferred conditions that cause FLIPs to soften and become fluid to interconnect adjacent paper fibers include heating of the first portion 11 of the weft 10 having a moisture content of about 30% or greater (ie, consistency of about 70% or less) at a temperature of at least 702C for a period of time of at least 0.5 seconds, and preferably under the pressure of at least 1 bar (14.7 psi). Most preferably, the moisture content is at least about 50%, the residence time is at least about 1.0 second, and the pressure is at least about 5 bar (73.5 psi). If the web 10 is heated by a first press surface 61 *, the P947 preferred temperature of the first press surface 61 * is at least about 1502C. The next step comprises the immobilization of the fluid FLIPs and the creation of native, latent, fluid polymer bonds (or FLIP bonds) between the cellulosic fibers that are smoothed and interconnected in the first portion 11 of the frame 10. The step of FLIP immobilization can be achieved either by using the first portion 11 of the weft 10, or by drying the first portion 11 of the weft 10, or by releasing the pressure to which the first portion 11 of the weft has been subjected 10. The above three steps can be performed either in an "alternative" or in combination, concurrently or consecutively, for example, in one mode of the process, the drying step alone, alternatively to the cooling step alone, can be enough to immobilize the FLIPs In another modality, for example, the cooling step can be achieved in the step of releasing pressure.Of course, the three steps can be combined to perform concurrently, or consecutively in any order. The papermaking process of the present invention may also include an optional pre-drying step of the intermediate web 10 to form a pre-dried web, the pre-drying step that is performed prior to P947 heating step. Any convenient means (not shown) known in the papermaking art can be used to pre-dry the intermediate web. For example, flow passage dryers, non-thermal capillary dewatering devices, and Yankee dryers, alone and in combination, are satisfactory. The next step is to dry the screen 10 to a consistency of more than about 70%. Preferably, the drying step occurs when the web 10 is heated and pressed between the first and second press members 61 and 62. The next step in the papermaking process is an optional step of condensation of the dry web 10. As used herein, "condensation" refers to the reduction in the length of a dry weft 10 that occurs when energy is applied to the dry weft 10 in a manner such that the length of the weft 10 is reduced and the fibers in the weft are reduced. the frame 10 is re-arranged with an associated break of some of the fiber-fiber links. The condensation can be achieved by any of the various well-known ways. The most common and preferred method is the creping shown schematically in Figures 1, 1A and IB. In the creping operation, the dry weft 10 adheres to a surface and is then removed from that surface with a scraper blade 16. The surface a P947 which the web 10 should usually also function as a drying surface, typically on the surface of the Yankee drying drum 14. In general, only the first portion 11 of the weft 10 that has been associated with the weft side surface 21 of the drying web 20 is adhered directly to the surface of the Yankee drying drum 14. The pattern of the first portion 11 of the weft 10 and its orientation relative to the scraper blade 16 will dictate for the most part the extent of the character of the creping imparted to a finished paper web 10 *. The weft 10 can also be wet micro-shrunk, as described in commonly assigned U.S. Patent No. 4,440,597, issued April 3, 1984 to Wells et al. and incorporated herein by reference. Figures 4 and 4A show a prophetic embodiment of the finished paper web 10 * which is made by the process of the present invention using the paper web 20 having an essentially continuous framework 30 shown schematically in Figures 2 and 2A. The paper web 10 * shown in Figures 4 and 4A comprises a first plurality of high density micro regions and a second plurality of low density micro regions. Low-density micro-regions comprise cellulosic fibers bound to native, latent, fluid polymers P947 (or attached to FLIP). A method to determine if FLIP bonds have been formed is described in an article by Leena Kunnas, et al. "The Effect of Conduct on Drying on the Structure of Fiber Bonds", TAPPI Journal, Vol. 76, No. 4, April 1993, which article is incorporated herein by reference and is appended hereto as an Appendix. Preferably, the low density micro-regions do not contain the cellulosic fibers bound by FLIP. The first plurality of high density micro regions comprises a network area 11 * essentially continuous, macroscopically monoplanar and patterned (formed by the fibers of the first portion 11 of the frame 10). The second plurality of the low density micro-regions comprises a plurality of discrete domes 12 * (formed by the fibers of the second portion 12 in the frame 10). Essentially all domes 12 * are scattered along, are isolated from each other and are covered by network area 11 *. The domes 12 * extend in the Z direction from the general plane of the network area 11 *. Preferably, the domes 12 * are placed in a non-random and repeating pattern corresponding to the pattern of the discrete ducts 40 of the resin framework 30 of the strip 20. A paper web made by the process P947 of the present invention utilizing the paper strip 20 having the frame 30 comprising the discrete protuberances 35 shown schematically in Figures 3 and 3A is not illustrated but can be easily visualized by imagining that in Figure 4, the essentially continuous area designated by the reference number 11 * is an area formed by the fibers of the second portion (low density), and the discrete areas designated by the reference number 12 * which are areas formed by the fibers of the first portion (high density) ). Then, the paper web made in the paper strip 20 having the frame 30 comprising the discrete protuberances 35 will have the first plurality of high density regions comprising a plurality of discrete knuckles, and the second plurality of low density regions that it comprises an essentially continuous and patterned network area. The knuckles are circumscribed by the network area and dispersed along its entire length. If the discrete protrusions 35 of the frame 30 have deflection conduits 40, discrete therein, as shown in Fig. 3, then, in a prophetic manner, the paper web will additionally comprise a third plurality of micro-regions corresponding to the discrete ducts 40 and formed by the fibers of the third portion 13 (Figure 3A). The third plurality of P947 the micro-regions will comprise regions of low density, essentially all of which are juxtaposed and isolated from each other by the first plurality of high density regions.

P947

Claims (10)

1. CLAIMS 1. A single sheet web with differential density of cellulosic fibers comprising native, latent, fluid polymers, the web has at least two pluralities of micro-regions placed in a non-random and repeating pattern, the web comprises: a first plurality of high density micro-regions comprising cellulosic fibers bound by native, latent, fluid polymers; and a second plurality of low density micro-regions that preferably do not contain the cellulosic fibers bound by native, latent, fluid polymers.
2. 2. The screen according to claim 1, wherein the native, latent, fluid polymers comprise hemicelluloses, lignin, polymeric extractables, any combination thereof. The frame according to claims 1 and 2, wherein the first plurality of the high density micro regions comprises an essentially continuous network area, macroscopically monoplanar and patterned; and the second plurality of low density micro-regions comprises a plurality of discrete domes, essentially all the domes are scattered throughout the network area, encompassed by it and isolated from each other by said area. 4. A process "for making a cellulose, individual sheet, differential density plot comprising at least a plurality of high density micro-regions and a second plurality of low density micro-regions, the process comprises the steps of: (a) provide a plurality of cellulosic papermaking fibers comprising native, latent, fluid polymers: the native, latent, fluid polymers comprise hemicelluloses, lignin, polymeric extractables or any combination thereof, (b) provide a paper web, permeable to fluids and macroscopically monoplanar having a surface of the side_ of the frame defining a plane XY, a rear surface opposite the surface of the side of the frame, a direction Z perpendicular to the plane XY, and deflection conduit extending between the surface of the side of the weft and the back surface; (c) depositing the plurality of cellulosic fibers comprising polyester native, latent, fluids on the surface of the weft side of the paper web to form a web of cellulose fibers in the paper web, the web comprises at least a first portion corresponding to the surface of the web side in the web. direction Z and a second portion corresponding to the P947 deflection conduits in the Z direction; (d) heating at least the first portion of the web to cause the native, latent, fluid polymers contained in the cellulosic fibers of the first portion to soften; (e) printing the weft side surface of the paper web in the web under pressure, thereby densifying the first portion of the web and causing the native, latent, fluid polymers to flow and interconnect the cellulosic fibers that are mutually juxtaposed in the first portion; e (f) immobilizing the native, latent, fluid polymers, and creating the bonds of native, latent, fluid polymers between the cellulosic fibers that are interconnected in the first portion. The process according to claim 4, wherein the step of immobilizing the native, latent, fluid polymers, and creating the native, latent, fluid polymer units comprises drying at least the first portion of the web or cooling at least the first portion of the weft or release the first portion of the pressure web or any combination thereof. The process according to claim 5, wherein the step of immobilizing the native, latent, fluid polymers and creating the native, latent, fluid polymer bonds comprises drying the web to a consistency of at least 70% at a temperature of at least 702C. The process according to claims 4, 5 and 6, wherein the step of printing the weft side surface of the paper web in the weft comprises pressing the weft and the paper web between a first press member and a second press member. Press member opposed to the first press member; the first and second press members have a first press surface and a second press surface, respectively, the first and second press surfaces are parallel to the XY plane and mutually opposite in the Z direction, the weft and the paper web are interposed between the first and second press surfaces; the first press surface makes contact with the web and the second press surface contacts the back surface of the paper web, the first and second press members are pressed together in the Z direction. 8. The process according to claim 7, wherein the first press surface comprises a pressing band. The process according to claim 7, wherein the first press surface comprises a surface of a Yankee drying drum. P947 10. The process according to claim 6, further comprising the step of applying a fluid pressure differential to the web of the cellulosic fibers so as to leave the first portion of the web on the surface of the weft side of the web. While the second portion of the web is deflected towards the deflection conduits, thereby removing a portion of the liquid carrier from the web, the step of applying a fluid pressure differential to the web is performed subsequent to the passage ( c) and before step (d). P947 SUMMARY OF THE INVENTION A single sheet web of differential density of cellulosic fibers is described. The frame comprises at least two pluralities of micro-regions placed in a non-random repeat pattern: a first plurality of high density regions and a second plurality of low density regions. The high density regions comprise cellulosic fibers comprising native, latent, fluid polymers (FLIP), < such as hemicelluloses and lignin. The fibers of the high-density regions are joined by FLIP, that is to say, joined together by the process of smoothing, fluidization and immobilization of the FLIPs between the cellulosic fibers of the high-density regions. The process for making the weft comprises the steps of providing a plurality of paper fibers comprising FLIP; providing a macroscopically monoplanar paper web (20) having a surface facing the plot (21) and deflection conduits (40), depositing the plurality of cellulosic fibers in the paper web (20) to form a weft; heating the frame to a temperature sufficient to cause the FLIPs contained in a first portion associated with the surface facing the weft of the web to soften; printing the surface of the weft side of the web in the weft (21); immobilize FLIPs P947 fluids and create FLIP links between the fibers that comprise the first portion of the frame. P947