Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
  • D21F11/06—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines of the cylinder type
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
  • D21F11/14—Making cellulose wadding, filter or blotting paper

Definitions

• Our invention relates to paper products such as absorbent sheets.
• Our invention also relates to methods of making paper products such as absorbent sheets, as well as to structuring fabrics for making paper products such as absorbent sheets.
• the resulting paper products also thereby have characteristics resulting from the molded shape, such as a particular caliper and absorbency.
• a myriad of structuring fabrics has been developed for use in papermaking processes to provide products with different shapes and characteristics. And, fabrics can be woven into a near limitless number of patterns for potential use in papermaking processes.
• One important characteristic of many absorbent paper products is softness— consumers want, for example, soft paper towels. Many techniques for increasing the softness of paper products, however, have the effect of reducing other desirable properties of the paper products.
• calendering basesheets as part of a process for producing paper towels can increase the softness of the resulting paper towels, but calendering also has the effect of reducing the caliper and absorbency of the paper towels.
• many techniques for improving other important properties of paper products have the effect of reducing the softness of the paper products. For example, using wet and dry strength resins in a papermaking process can improve the underlying strength of paper products, but wet and dry strength resins also reduce the perceived softness of the products. For these reasons, it is desirable to make softer paper products, such as absorbent sheets.
• our invention provides an absorbent sheet of cellulosic fibers.
• the absorbent cellulosic sheet includes a plurality of projected regions projecting from the absorbent sheet, wherein the projected regions include folds that are curved relative to the machine direction of the absorbent sheet. Ends of the curved folds are on opposite sides of the projected regions and such that one of the ends of each of the curved folds is positioned downstream from the other end of the curved folds in the machine direction of the absorbent sheet. Apexes of the curved folds are positioned downstream in the machine direction of the absorbent sheet. Further, connecting regions connecting the projected regions of the absorbent sheet.
• our invention provides an absorbent cellulosic sheet.
• a plurality of projected regions project from the absorbent sheet, wherein the projected regions include folds that are curved relative to the machine direction of the absorbent sheet. Ends of the curved folds are on opposite sides of the projected regions, and the curved folds have a radius of curvature of about 0.5 mm to about 2.0 mm. Further, connecting regions connecting the projected regions of the absorbent sheet.
• the papermaking web comprises a plurality of projected regions projecting from the papermaking web, wherein the projected regions include folds that are curved relative to a machine direction of the absorbent sheet, with ends of the curved folds being on opposite sides of the projected regions and such that one of the ends of each of the curved folds is positioned downstream from the other end of the curved folds in the machine direction of the papermaking web. Apexes of the curved folds are positioned downstream in the machine direction of the papermaking web. Connecting regions form a network connecting the projected regions of the papermaking web.
• our invention provides a method of making a fabric-creped absorbent cellulosic sheet.
• the method includes compactively dewatering a papermaking furnish to form a web.
• the method also includes creping the web under pressure in a creping nip between a transfer surface and a structuring fabric.
• the structuring fabric includes knuckles formed on warp yarns of the structuring fabric, with the knuckles being positioned along lines that are angled relative to the machine direction of the fabric, wherein the angle of lines relative to the machine direction is between about 10° and about 30°.
• the method includes a step of drying the web to form the absorbent cellulosic sheet.
• our invention provides an absorbent cellulosic sheet that includes a plurality of projected regions projecting from the absorbent sheet, with the projected regions including folds that are curved in the machine direction of the absorbent sheet, and with ends of the curved folds being on opposite sides of the projected regions.
• the absorbent sheet has a normalized fold curvature ratio that is less than about 4.
• the absorbent sheet also includes connecting regions forming a network connecting the projected regions of the absorbent sheet.
• Figure 1 is a schematic diagram of a papermaking machine configuration that can be used in conjunction with our invention.
• Figure 2 is a top view of a structuring fabric for making paper products according to an embodiment of our invention.
• Figures 3 A-3F indicate characteristics of structuring fabrics according to embodiments of our invention and characteristics of comparison structuring fabrics.
• Figures 4A-4E are photographs of absorbent sheets according to embodiments of our invention.
• Figure 5 is an annotated version of the photograph shown in Figure 4E.
• Figures 6A and 6B are cross-sectional views of a portion of an absorbent sheet according to an embodiment of our invention and a portion of a comparison absorbent sheet, respectively.
• Figures 7 A and 7B show laser scans for determining the profile of portions of absorbent sheets according to embodiments of our invention.
• Figure 8 indicates characteristics of structuring fabrics according to embodiments of our invention and a comparison structuring fabric.
• Figure 9 shows the characteristics of basesheets that were made using the structuring fabrics having the characteristics shown in Figure 8.
• Figures 10A-10D indicate characteristics of still further structuring fabrics according to embodiments of our invention.
• Figures 11 A-l IE are photographs of absorbent sheets according to embodiments of our invention.
• Figures 12A-12E are photographs of further absorbent sheets according to embodiments of our invention.
• Figure 13 indicates characteristics of structuring fabrics according to embodiments of our invention and a comparison structuring fabric.
• Figure 14 shows a measurement of a profile along one of the warp yarns of a structuring fabric according to an embodiment of our invention.
• Figure 15 is a chart showing fabric crepe percentage versus caliper for basesheets made with a fabric according to an embodiment of our invention and a comparative fabric.
• Figure 16 is a chart showing fabric crepe percentage versus SAT capacity for basesheets made with a fabric according to an embodiment of our invention and a comparative fabric.
• Figure 17 is a chart showing fabric crepe percentage versus caliper for basesheets made with different furnishes and a fabric according to an embodiment of our invention.
• Figure 18 is a chart showing fabric crepe percentage versus SAT capacity for basesheets made with different furnishes and a fabric according to an embodiment of our invention.
• Figure 19 is a chart showing fabric crepe percentage versus void volume for basesheets made with a fabric according to an embodiment of our invention and a comparative fabric.
• Figures 20A and 20B are soft x-ray images of an absorbent sheet according to an
• Figures 21 A and 21B are soft x-ray images of an absorbent sheet according to another embodiment of our invention.
• Figures 22A-22E are photographs of absorbent sheets according to further embodiments of our invention.
• Figures 23 A and 23B are photographs of an absorbent sheet according to an embodiment of our invention and a comparison absorbent sheet.
• Figure 24A and 24B are photographs of cross sections of the absorbent sheets shown in Figures 23 A and 23B, respectively.
• Figures 25A and 25B indicate characteristics of further structuring fabrics according to embodiments of our invention.
• Figure 26 is a detailed view of a pressure imprint of one of the structuring fabrics having the characteristics shown in Figure 25B.
• Figure 27A-27C show fold formations around the knuckles in a structuring fabric according to an embodiment of our invention and around knuckles in comparative structuring fabrics.
• Figures 28A-28E are photographs of further absorbent sheets according to embodiments of our invention.
• Figure 29 is photograph of an absorbent sheet according to an embodiment of our invention with annotation lines for determining aspects of the fabric.
• Figures 30A and 30B are photographs of an absorbent sheet according to our invention and a comparison absorbent sheet, respectively.
• Our invention relates to paper products such as absorbent sheets and methods of making paper products such as absorbent sheets.
• Absorbent paper products according to our invention have outstanding combinations of properties that are superior to other absorbent paper products that are known in the art.
• the absorbent paper products according to our invention have combinations of properties particularly well suited for absorbent hand towels, facial tissues, or toilet paper.
• paper product encompasses any product incorporating
• Papermaking fibers having cellulose as a major constituent. This would include, for example, products marketed as paper towels, toilet paper, facial tissue, etc.
• Papermaking fibers include virgin pulps or recycled (secondary) cellulosic fibers, or fiber mixes comprising cellulosic fibers.
• Wood fibers include, for example, those obtained from deciduous and coniferous trees, including softwood fibers, such as northern and southern softwood kraft fibers, and hardwood fibers, such as eucalyptus, maple, birch, aspen, or the like.
• fibers suitable for making the products of our invention include non-wood fibers, such as cotton fibers or cotton derivatives, abaca, kenaf, sabai grass, flax, esparto grass, straw, jute hemp, bagasse, milkweed floss fibers, and pineapple leaf fibers.
• non-wood fibers such as cotton fibers or cotton derivatives, abaca, kenaf, sabai grass, flax, esparto grass, straw, jute hemp, bagasse, milkweed floss fibers, and pineapple leaf fibers.
• “Furnishes” and like terminology refers to aqueous compositions including papermaking fibers, and, optionally, wet strength resins, debonders, and the like, for making paper products.
• a variety of furnishes can be used in embodiments of our invention, and specific furnishes are disclosed in the examples discussed below.
• furnishes are used according to the specifications described in commonly-assigned U.S. Patent No. 8,080,130 (the disclosure of which is incorporated by reference in its entirety).
• the furnishes in this patent include, among other things, cellulosic long fibers having a coarseness of at least about 15.5 mg/100 mm. Examples of furnishes are also specified in the examples discussed below.
• the initial fiber and liquid mixture that is dried to a finished product in a papermaking process will be referred to as a "web” and/or a "nascent web.”
• the dried, single-ply product from a papermaking process will be referred to as a "basesheet.”
• the product of a papermaking process may be referred to as an "absorbent sheet.”
• an absorbent sheet may be the same as a single basesheet.
• an absorbent sheet may include a plurality of basesheets, as in a multi-ply structure.
• an absorbent sheet may have undergone additional processing after being dried in the initial basesheet forming process in order to form a final paper product from a converted basesheet.
• an "absorbent sheet” includes commercial products marketed as, for example, hand towels.
• machine direction (MD) and “cross machine direction” (CD) will be used in accordance with their well-understood meaning in the art. That is, the MD of a fabric or other structure refers to the direction that the structure moves on a papermaking machine in a papermaking process, while CD refers to a direction crossing the MD of the structure. Similarly, when referencing paper products, the MD of the paper product refers to the direction on the product that the product moved on the
• the CD of the product refers to the direction crossing the MD of the product.
• the MD of the paper product In terms of the MD of the paper product,
• downstream refers to an area that is formed before an "upstream” area.
• FIG 1 shows an example of a papermaking machine 200 that can be used to make paper products according to our invention.
• a detailed description of the configuration and operation of papermaking machine 200 can be found in commonly-assigned U.S. Patent No. 7,494,563 (“the '563 patent”), the disclosure of which is incorporated by reference in its entirety.
• the '563 patent describes a papermaking process that does not use through air drying (TAD).
• TAD through air drying
• the papermaking machine 200 is a three-fabric loop machine that includes a press section 100 in which a creping operation is conducted. Upstream of the press section 100 is a forming section 202.
• the forming section 202 includes headbox 204 that deposits an aqueous furnish on a forming wire 206 supported by rolls 208 and 210, thereby forming an initial aqueous cellulosic web 116.
• the forming section 202 also includes a forming roll 212 that supports a papermaking felt 102 such that web 116 is also formed directly on the felt 102.
• a felt run 214 extends about a suction turning roll 104 and then to a shoe press section 216 wherein the web 116 is deposited on a backing roll 108.
• the web 116 is wet-pressed concurrently with the transfer of the web 116 to the backing roll 108, which carries the web 116 to a creping nip 120.
• the web 116 instead of being transferred on the backing roll 108, the web 116 by be transferred from the felt run 214 onto an endless belt in a dewatering nip, with the endless belt then carrying the web 116 to the creping nip 120.
• An example of such a configuration can be seen in U.S. Patent No. 8,871,060, which is incorporated by reference herein in its entirety.
• the web 116 is transferred onto the structuring fabric 112 in the creping nip 120, and then vacuum drawn by vacuum molding box 114. After this creping operation, the web 116 is deposited on a Yankee dryer 218 in another press nip 217 using a creping adhesive that is applied to the surface of the Yankee dryer 218.
• the web 116 is dried on Yankee dryer 218, which is a heated cylinder, and the web 116 is also dried by high jet velocity impingement air in the hood around the Yankee dryer 218. As the Yankee dryer 218 rotates, the web 116 is peeled from the dryer 218 at position 220. The web 116 may then be subsequently wound on a take-up reel (not shown).
• the reel may be operated slower than the Yankee dryer 218 at steady-state in order to impart a further crepe to the web.
• a creping doctor blade 222 may be used to conventionally dry-crepe the web 116 as it is removed from the Yankee dryer 218.
• the web 116 is transferred onto the top side of the structuring fabric 112.
• the creping nip 120 is defined between the backing roll 108 and the structuring fabric 112, with the structuring fabric 112 being pressed against the backing roll 108 by a creping roll 110.
• the web 116 still has a high moisture content when it is transferred to the structuring fabric 112, the web is deformable such that portions of the web can be drawn into pockets formed between the yarns that make up the structuring fabric 112. (The pockets of structuring fabrics will be described in detail below.)
• the structuring fabric 112 moves more slowly than does the papermaking felt 102.
• the web 116 is creped as it is transferred onto the structuring fabric 112.
• An applied suction from vacuum molding box 114 may also aid in drawing the web 116 into pockets in the surface of the structuring fabric 112, as will be described below.
• the web 116 reaches a highly consistent state with most of the moisture having been removed. The web 116 is thereby more or less
• Basesheets made with papermaking machine 200 may also be subjected to further processing, as is known in the art, in order to convert the basesheets into specific products.
• the basesheets may be embossed, and two basesheets can be combined into multi-ply products. The specifics of such converting processes are well known in the art.
• the web 116 is dewatered to the point that it has a higher consistency when transferred onto the top side of the structuring fabric 112 as compared to an analogous operation in other papermaking processes, such as a TAD process. That is, the web 116 is compactively dewatered so as to have from about 30 percent to about 60 percent consistency (i.e., solids content) before entering the creping nip 120. In the creping nip 120, the web 116 is subjected to a load of about 30 pounds per linear inch (PLI) to about 200 PLI. Further, there is a speed differential between the backing roll 108 and the structuring fabric 112. This speed differential is referred to as the fabric creping percentage, and may be calculated as:
• Fabric Crepe % S1/S2 - 1 where Si is the speed of the backing roll 108 and S2 is the speed of the structuring fabric 112.
• the fabric crepe percentage, or "creping ratio” can be anywhere from about 3% to about 100%. This combination of web consistency, speed differential occurring at the creping nip 120, the pressure employed at the creping nip 120, and the structuring fabric 112 and creping nip 120 geometry act to rearrange the cellulose fibers while the web 116 is still pliable enough to undergo structural change.
• the slower forming surface speed of the structuring fabric 112 causes the web 116 to be substantially molded into openings in the structuring fabric 116, with the fibers being realigned in proportion to the creping ratio.
• FIG. 2 is a drawing showing details of a portion of the web contacting side of a structuring fabric 300 that has a configuration for forming paper products according to an embodiment of our invention.
• the structuring fabric 300 includes warp yarns 302 that run in the machine direction (MD) when the fabric is used in a papermaking process, and weft yarns 304 that run in the cross machine direction (CD).
• MD machine direction
• CD cross machine direction
• the warp and weft yarns 302 and 304 are woven together so as to form the body of the structuring fabric 300.
• the web-contacting surface of the structuring fabric 300 is formed by knuckles (two of which are outlined in Figure 2 and labeled as 306 and 310), which are formed on the warp yarns 302, but no knuckles are formed on the weft yarns 304. It should be noted, however, that while the structuring fabric 300 shown in Figure 2 only has knuckles on the warp yarns 302, our invention is not limited to structuring fabrics that only have warp knuckles, but rather, includes fabrics that have both warp and weft knuckles. Indeed, fabrics with only warp knuckles and fabrics with both warp and weft knuckles will be described in detail below.
• the knuckles 306 and 310 in the structuring fabric 300 are in a plane that makes up the surface that the web 116 contacts during a papermaking operation.
• Pockets 308 (one of which is shown as the dotted outlined area in Figure 2) are defined in the areas between the knuckles 306 and 310. Portions of the web 116 that do not contact the knuckles 306 and 310 are drawn into the pockets 308 as described above. It is the portions of the web 116 that are drawn into the pockets 308 that result in domed regions that are found in the resulting paper products.
• warp yarn knuckles 306 and 310 have a length of about 2 mm to about 6 mm.
• Most structuring fabrics known in the art have shorter warp yarn knuckles (if the fabrics have any warp yarn knuckles at all).
• the longer warp yarn knuckles 306 and 310 provide for a larger contact area for the web 116 during the papermaking process, and, it is believed, might be at least partially responsible for the increased softness seen in absorbent sheets according to our invention, as compared to absorbent sheets with conventional, shorter warp yarn knuckles.
• FIG. 3 A-3E indicate some of the characteristics of structuring fabrics made according to embodiments of our invention, which are labeled as Fabrics 1-15.
• Figure 3F also shows characteristics of conventional structuring fabrics, which are labeled as Fabrics 16 and 17. Structuring fabrics of the type shown in Figures 3 A-3F can be made by numerous
• Fabrics 1-15 have long warp yarn knuckle fabrics such that the vast majority of the contact area in Fabrics 1-15 comes from the warp yarn knuckles, as opposed to weft yarn knuckles (if the fabrics have any weft yarn knuckles at all).
• Fabrics 16 and 17, which have shorter warp yarn knuckles, are provided for comparison. All of the characteristics shown in Figures 3 A-3F were determined using the techniques in the aforementioned fabric characterization publications, particularly, using the non-rectangular, parallelogram calculation methods that are set forth in the fabric characterization
• the air permeability of a structuring fabric is another characteristic that can influence the properties of paper products made with the structuring fabric.
• the air permeability of a structuring fabric is measured according to well-known equipment and tests in the art, such as Frazier® Differential Pressure Air Permeability Measuring Instruments by Frazier Precision Instrument Company of Hagerstown, Maryland.
• the long warp knuckle structuring fabrics used to produce paper products according to our invention have a high amount of air permeability.
• the long warp knuckle structuring fabric has an air permeability of about 450 CFM to about 1000 CFM.
• Figures 4A-4E are photographs of absorbent sheets made with long warp knuckle structuring fabrics, such as those characterized in Figures 3 A-3E. More specifically, Figures 4A-4E show the air side of the absorbent sheets, that is, the side of the absorbent sheets that contacted the structuring fabric during the process of forming the absorbent sheets. Thus, the distinct shapes that are imparted to the absorbent sheets through contact with the structuring fabrics, including domed regions projecting from the shown side of the absorbent sheet, can be seen in Figures 4A-4E. Note that the MD of the absorbent sheets is shown vertically in these figures.
• the absorbent sheet 1000 includes a plurality of substantially rectangular-shaped domed regions, some of which are outlined and labeled 1010, 1020, 1030, 1040, 1050, 1060, 1070, and 1080 in Figure 5.
• the domed regions 1010, 1020, 1030, 1040, 1050, 1060, 1070, and 1080 correspond to the portions of the web that were drawn into the pockets of the structuring fabric during the process of forming the absorbent sheet 1000.
• the connecting regions generally correspond to portions of the web that were formed in the plane of the knuckles of the structuring fabric during the process of forming the absorbent sheet 1000.
• All of the domed regions include a plurality of indented bars formed into the tops of the domed regions, with the indented bars extending across the domed regions in the CD of the absorbent sheets. Some of these indented bars are outlined and labeled 1085 in Figure 5. Notably, almost all of the domed regions have three such indented bars, with some of the domed regions having four, five, six, seven, or even eight indented bars.
• the number of indented bars can be confirmed using laser scan profiling (described below). Using such laser scan profiling, it was found that in a particular absorbent sheet according to an embodiment of our invention, there are, on average (mean), about six indented bars per domed region.
• indented bars seen in the absorbent sheets shown in Figure 4A-4E and 5 are formed when the web is transferred onto a structuring fabric with the configurations described herein during a papermaking process as described herein. Specifically, when a speed differential is used for creping the web as it is transferred onto the structuring fabric, the web "plows" onto the knuckles of the structuring fabric and into the pockets between the knuckles. As a result, folds are created in the structure of the web, particularly in the areas of the web that are moved into the pockets of the structuring fabric. An indented bar is thus formed between two of such folds in the web.
• the plowing/folding effect takes place multiple times over a portion of a web that spans a pocket in the structuring fabric.
• multiple indented bars are formed in each of the domed regions of absorbent sheets made with the long warp knuckle structuring fabrics described herein.
• the indented bars in the domed regions may contribute to an increased softness that is perceived in the absorbent sheets according to our invention. Specifically, the indented bars provide a more smooth, flat plane being perceived when the absorbent sheet is touched, as compared to absorbent sheets having conventional domed regions.
• the difference in perceptional planes is illustrated in Figures 6A and 6B, which are drawings showing cross sections of an absorbent sheet 2000 according to our invention and a comparison sheet 3000, respectively.
• the domed regions 2010 and 2020 include indented bars 2080, with ridges being formed between the indented bars 2080 (the ridges/indents correspond to the folds in the web during the papermaking process as described above).
• the comparison sheet 3000 is perceived as less smooth and soft compared to the perceived planes PI found in the domed regions 2010 and 2020 with the indented bars 2080.
• domed regions of an absorbent sheet according to our invention might have different numbers of indented bars. At the same time, a few of the domed regions observed in any particular absorbent sheet of our invention might not include any indented bars.
• the lengths and depths of the indented bars in absorbent sheets, as well as the lengths of the domed regions, can be determined from a surface profile of a domed region that is made using laser scanning techniques, which are well known in the art.
• Figures 7 A and 7B show laser scan profiles across domed regions in two absorbent sheets according to our invention.
• the peaks of the laser scan profiles are the areas of the domes that are adjacent to the indented bars, while the valleys of the profiles represent the bottoms of the indented bars.
• we have found that the indented bars extend to a depth of about 45 microns to about 160 microns below the tops of the adjacent areas of the domed regions.
• the indented bars extend an average (mean) of about 90 microns below the tops of the adjacent areas of the domed regions.
• the domed regions extend a total of about 2.5 mm to about 3 mm in length in a substantially MD of the absorbent sheets.
• the long domed regions are at least partially the result of the long MD pockets in the structuring fabrics used to create the absorbent sheets, as discussed above. From the laser scan profiles, it can also be seen that the indented bars were spaced about 0.5 mm apart along the lengths of the domed regions in embodiments of our invention.
• dome regions being bilaterally staggered in the MD such that substantially continuous, stepped lines of domed regions extend in the MD of the sheets.
• the domed region 1010 is positioned adjacent to the domed region 1020, with the two domed regions overlapping in a region 1090.
• the domed region 1020 overlaps domed region 1030 in a region 1095.
• the bilaterally staggered domed regions 1010, 1020, and 1030 form a continuous, stepped line, substantially along the MD of the absorbent sheet 1000.
• Other domed regions form similar continuous, stepped lines in the MD.
• the bilaterally staggered domed regions provide for a smooth planar surface on the Yankee side of the absorbent sheets, which thereby results in a better distribution of pressure points on the absorbent sheet.
• the Yankee side of an absorbent sheet is the side of the absorbent sheets that is opposite to the air side of the absorbent sheets that is drawn into the structuring fabric during the papermaking process.
• the bilaterally staggered domed regions act like long boards in the MD direction that cause the absorbent sheet structure to lay flat. This effect, resulting from the combination of bilaterally staggered domed regions and indented bars will, for example, cause a web to better lay down on the surface of a Yankee dryer during a papermaking process, which results in better absorbent sheets.
• substantially continuous lines of connecting regions extend in a stepped manner along the MD of the absorbent sheet 1000.
• connection region 1015 which runs substantially in the CD
• connecting region 1025 which runs substantially in the CD.
• Connecting region 1025 is also contiguous with connecting region 1035, which runs substantially in the MD.
• connecting region 1015 is contiguous with connecting region 1025 and connecting region 1055.
• the MD connecting regions are substantially longer than the CD connecting regions, such that lines of stepped, continuous connecting regions can be seen along the absorbent sheet.
• the sizes of the domed regions and the connecting regions of an absorbent sheet generally correspond to the pocket and knuckle sizes in the structuring fabric used to produce the absorbent sheet.
• the relative sizing of the domed and connecting regions contributes to the softness of absorbent sheets made with the fabric.
• the softness is further improved as a result of the substantially continuous lines of domed regions and connecting regions.
• a distance in the CD across the domed regions is about 1.0 mm
• a distance in the CD across the MD oriented connecting regions is about 0.5 mm.
• overlap/touching regions between adjacent domed regions in the substantially continuous lines are about 1.0 mm in length along the MD.
• Such dimensions can be determined from a visual inspection of the absorbent sheets, or from a laser scan profile as described above. An exceptionally soft absorbent sheet can be achieved when these dimensions are combined with the other features of our invention described herein.
• absorbent sheets were made using Fabric 15 as shown Figure 3E in a papermaking machine having the general configuration shown in Figure 1 with a process as described above.
• products were made using the shorter warp length knuckle Fabric 17 (that is also shown in Figure 3F) under the same process conditions. Parameters used to produce basesheets for these trials are shown in TABLE 1.
• Sheets formed in the trials with Fabric 15 were found to be smoother and softer than the sheets formed in the trials with Fabric 17 ⁇ i.e., a shorter warp knuckle fabric).
• Other important properties of the sheets made with Fabric 15, such as caliper and bulk, were found to be very comparable to those properties of the sheets made with Fabric 17.
• the basesheets made with the long warp knuckle Fabric 15 could potentially be used to make absorbent products that are softer than absorbent products with the shorter warp knuckle Fabric 17 without the reduction of other important properties of the absorbent products.
• the planar volumetric index (PVI) is a useful parameter for characterizing a structuring fabric.
• the PVI for a structuring fabric is calculated as the contact area ratio (CAR) multiplied by the effective pocket volume (EPV) multiplied by one hundred, where the EPV is the product of the pocket area estimate (PA) and the measured pocket depth.
• the pocket depth is most accurately calculated by measuring the caliper of a handsheet formed on the structuring fabric in a laboratory, and then correlating the measured caliper to the pocket depth. And, unless otherwise noted, all of the PVI-related parameters described herein were determined using this handsheet caliper measuring method.
• a non-rectangular, parallelogram PVI is calculated as the contact area ratio (CAR) multiplied by the effective pocket volume (EPV) multiplied by one hundred, where the CAR and EPV are calculated using a non-rectangular, parallelogram unit cell area calculation.
• the contact area of the structuring long warp knuckle fabric varies between about 25% to about 35% and the pocket depth varies between about 100 microns to about 600 microns, with the PVI thereby varying accordingly.
• PVDI planar volumetric density index
• the PVDI of a structuring fabric is defined as the PVI multiplied by pocket density. Note that in embodiments of our invention, the pocket density varies between about 10 cm “2 to about 47 cm "2 .
• Yet another useful parameter of a structuring fabric can be developed by multiplying the PVDI by the ratio of the length and width of the knuckles of the fabric, thereby providing a PVDI-knuckle ratio (PVDI-KR).
• a PVDI-KR for a long warp knuckle structuring fabric as described herein would be the PVDI of the structuring fabric multiplied by the ratio of warp knuckles length in the MD to the warp knuckles width in the CD.
• these parameters take into account important aspects of a structuring fabric (including percentage of contact area, pocket density, and pocket depth) that affect shapes of paper products made using the structuring fabric, and, hence, the PVDI and PVDI-KR may be indicative of the properties of the paper products such as softness and absorbency.
• the PVI, PVDI, PVDI-KR, and other characteristics were determined for three long warp knuckle structuring fabrics according to embodiments of our invention, with the results being shown as Fabrics 18-20 in Figure 8.
• the PVI, PVDI, PVDI-KR, and other characteristics were also determined for a shorter warp knuckle structuring fabric, as is shown as Fabric 21 in Figure 8.
• the PVDI-KRs for Fabrics 18-20 are about 43 to about 50, which are significantly greater than the PVDI-KR of 16.7 for Fabric 21.
• Fabrics 18-21 were used to produce absorbent sheets, and characteristics of the absorbent sheets were determined, as shown in Figure 9.
• the characteristics shown in Figure 9 were determined using the same techniques that are described in the aforementioned fabric characterization publications.
• the determinations of the interconnecting regions correspond to the warp knuckles on the structuring fabric
• the dome regions correspond to the pockets of the structuring fabric.
• the sheets made from the long warp knuckle Fabrics 18-20 have multiple indented bars in each dome region.
• the domed regions of the absorbent sheet formed from the shorter warp knuckle Fabric 21 had, at most, one indented bar, and many of the domed regions did not have any indented bars at all.
• the sensory softness was determined for the absorbent sheets shown in Figure 9.
• Sensory softness is a measure of the perceived softness of a paper product as determined by trained evaluators using standardized testing techniques. More specifically, sensory softness is measured by evaluators experienced with determining the softness, with the evaluators following specific techniques for grasping the paper and ascertaining a perceived softness of the paper. The higher the sensory softness number, the higher the perceived softness.
• the absorbent sheets made with Fabrics 18-20 were 0.2 to 0.3 softness units higher than the absorbent sheets made with Fabric 21. This difference is outstanding.
• the sensory softness was found to correlate with the PVDI-KR of the fabrics.
• PVDI-KR the higher the PVDI-KR of the structuring fabric, the higher the sensory softness number that was achieved.
• PVDI-KR is a good indicator of the softness that can be achieved in a paper product made with a process using a structuring fabric, with a higher PVDI-KR structuring fabric producing a softer product.
• Figures 10A-10D show characteristics of further long-warp knuckle Fabrics 22-41 according to various embodiments of our invention, including the PVI, PVDI, and PVDI-KR for each of the fabrics.
• these structuring fabrics have a wider range of characteristics than the structuring fabrics described above.
• contact lengths of the warp knuckles of Fabrics 22-41 ranged from about 2.2 mm to about 5.6 mm. In further embodiments of our invention, however, the contact lengths of the warp knuckles may range from about 2.2 mm to about 7.5 mm.
• the pocket depths were determined by forming a handsheet on the fabrics and then determining the size of domes on the handsheet (the size of the domes corresponding to the size of the pockets, as described above).
• the pocket depths for Fabrics 38-40 were determined using techniques set forth in the aforementioned fabric characterization patents. Further trials were conducted to evaluate properties of absorbent sheets according to embodiments of our invention. In these trials, the Fabrics 27 and 38 were used. For these trials, a papermaking machine having the general configuration shown in Figure 1 was used with a process as described above. Parameters used to produce the basesheets for these trials are shown in TABLE 3. Note that an indication of a varying rate means that the process variable was varied in different trial runs.
• the basesheets in these trials were converted into unembossed, single-ply rolls.
• Pictures of the absorbent sheets made with Fabric 27 are shown in Figures 11 A-l IE and pictures of the absorbent sheets made with Fabric 38 are shown in Figures 12A-12E.
• the domed regions of the absorbent sheets include a plurality of indented bars like the absorbent sheets described above.
• the absorbent sheets made with Fabrics 27 and 38 include bilaterally staggered domed regions that result in substantially continuous, stepped lines in the MD of the absorbent sheets, and substantially continuous, stepped connecting regions between the domed regions.
• the profiles of the domed regions in the basesheets made from Fabrics 27 and 38 were determined using laser scanning, in the same manner that the profiles were determined in the absorbent sheets described above. It was found that the domed regions in the basesheets made with Fabric 27 had 4 to 7 indented bars, with there being an average (mean) of 5.2 indented bars per domed region.
• the indented bars of domed regions extended from about 132 to about 274 microns below the tops of adjacent areas of the domed regions, with an average (mean) depth of about 190 microns. Further, the domed regions extended about 4.5 mm in the MD of the basesheets.
• the domed regions in the basesheets made with Fabric 38 had 4 to 8 indented bars, with there being an average (mean) of 6.29 indented bars per domed region.
• the indented bars of domed regions in the basesheets made with Fabric 38 extended from about 46 to about 159 microns below the tops of adjacent areas of the domed regions, with an average (mean) depth of about 88 microns. Further, the domed regions extended about 3 mm in the MD of the basesheets. Because the extended MD direction domed regions in the basesheets made with Fabrics 27 and 38 include a plurality of indented bars, it follows that the basesheets will have similar beneficial properties stemming from the configuration of the domed regions as the absorbent sheets described above.
• the basesheets made with Fabrics 27 and 38 will be softer to the touch compared to basesheets made with fabrics not having long warp knuckles.
• Other properties of the basesheets made with Fabrics 27 and 38 were compared to the properties of basesheets made with shorter knuckle fabrics.
• the caliper and pocket depth were compared for uncalendered basesheets made with the different fabrics. The caliper was measured using standard techniques that are well known in the art. It was found that the caliper of the basesheets made with Fabric 27 varied from about 80 mils/8 sheets to about 110 mils/8 sheets, while the basesheets made with Fabric 38 varied from about 80 mils/8 sheets to about 90 mils/8 sheets. Both of these ranges of caliper are very comparable, if not better than, the about 60 to about 93 mils/8 sheets caliper that was found in the basesheets made with shorter warp yarn knuckle fabrics under similar process conditions.
• the depths of the domed regions were measured using a topographical profile scan of the air side (i.e., the side of the basesheets that contacts the structuring fabric during the
• the depths of the domed regions in the basesheets made using Fabric 27 ranged from about 500 microns to about 675 microns, while the depths of the domed regions in the basesheets made using Fabric 38 ranged from about 400 microns to about 475 microns. These domed regions were comparable to, if not greater than, the depths of the domed regions in basesheets made from the structuring fabrics having shorter warp yarn knuckles.
• the pockets are long and deep, as reflected in the PVI related parameters indicated in Figure 13.
• the CD yarns are entirely located below the plane of the knuckles in the MD yarns such that there are no CD knuckles at the top surface of the fabric. Because there are no CD knuckles, there is a gradual slope to the warp yarns in the z-direction, the details of which are shown in the profile scan in Figure 14. As indicated in this figure, the warp yarns have a slope of about 200 ⁇ /mm from the lowest point where the warp yarns pass under a CD yarn to the top of the adjacent warp knuckle.
• the warp yarns are angled from about 11 degrees relative to a plane that Fabric 42 moves along during the creping operation. It is believed that this gradual slope of the warp yarns allows the fibers in a web being pressed to Fabric 42 to only slightly pile up on the sloped portion of the warp yarn before some of the fibers slip up over the top of the adjacent knuckle.
• the gradual slope of the warp yarns in Fabric 42 thereby creates less of an abrupt stop for the fibers of the web and less densification of the fibers as compared to other fabrics where the warp yarns have a steeper slope that is contacted by the web .
• Fabrics 42 and 43 both have higher PVDI-KR values, and these values in conjunction with the PVDI-KR values of the other structuring fabrics described herein are generally indicative of the range of PVDI-KR values that can be found in embodiments of our invention. Further, structuring fabrics with even higher PVDI-KR values, for example, up to about 250, could also be used.
• the cellulose fibers in the web are subjected to various localized forces (e.g., pushed, pulled, bent, delaminated), and subsequently become more separated from each other. In other words, the fibers become de- bonded and result in a lower modulus for the product.
• the web therefore has better vacuum "moldability," which leads to greater caliper and a more open structure that provides for greater ab sorpti on .
• Figures 15 and 16 show that, even in the trials with Fabric 42 where no vacuum molding was used, the caliper and SAT capacity increased with the increasing fabric crepe level. As there was no vacuum molding, it follows that these increases in caliper and SAT capacity are directly related to fiber mobility in Fabric 42.
• Figures 15 and 16 also demonstrate that a high amount of caliper and SAT capacity are achieved using Fabric 42— in the trials where vacuum molding is used, at each creping level the caliper and SAT capacity of the basesheets made with Fabric 42 were much greater than the caliper and SAT capacity of the basesheets made with Fabric 45.
• the fiber moldability provided by Fabric 42 can also be seen in the results shown in Figure 15 and 16. Specifically, the differences between the caliper and SAT capacity in the trials with no vacuum molding and the trials with vacuum molding demonstrates that the fibers in the web are highly moldable on Fabric 42. As will be discussed below, vacuum molding draws out the fibers in the regions of the web formed in the pockets of Fiber 42. The large fiber moldability means that the fibers are highly drawn out in this molding operation, which leads to the increased caliper and SAT capacity in the resulting product. Figure 19 also evidences that greater fiber mobility is achieved with Fabric 42 by comparing the void volume of the basesheets from the trials at the fabric crepe levels.
• void volume is essentially a measure of the space between the cellulose fibers. Void volume is measured by the procedure set forth in the aforementioned U.S. Patent No. 7,399,378. As shown in Figure 19, the void volume increased with the increasing fabric crepe in the trials using Fabric 42 where no vacuum molding was used. This indicates that the cellulose fibers were more separated from each other (i.e., de-bonded, with a lower resulting modulus) at each fabric crepe level in order to produce the additional void volume. Figure 19 further demonstrates that, when vacuum molding is used, Fabric 42 produces basesheets with more void volume than the conventional Fabric 45 at each fabric crepe level.
• FIGs 20A, 20B, 21 A, and 2 IB are soft x-ray images of basesheets made using Fabric 42.
• soft x-ray imaging is a high-resolution technique that can be used for gauging mass uniformity in paper.
• the basesheets in Figures 20A and 20B where made with an 8 percent fabric crepe, whereas the basesheets in Figures 21 A and 21B were made with a 25 percent fabric crepe.
• Figures 20A and 21 A show fiber movement at a more "macro" level, with the images showing an area of 26.5 mm by 21.2 mm.
• Wave-like patterns of less mass can be seen with the higher fabric crepe (Figure 21 A), but regions of less mass are not readily seen with the lower fabric crepe ( Figure 20A).
• Figures 20B and 2 IB show the fiber movement at a more "micro" level, with the images showing an area of 13.2 mm by 10.6 mm.
• the cellulose fibers can clearly be seen as more distanced from each other and pulled apart with the higher fabric crepe (Figure 2 IB) than with the lower fiber crepe ( Figure 20B).
• the soft x-ray images further confirm that Fabric 42 provides for greater fiber mobility with the higher localized mass movement being seen at the higher fabric crepe level than at the lower fabric crepe level.
• FIGs 17 and 18, and also Figure 19, show the results of the trials in terms of the furnish. Specifically, these figures show that Fabric 42 can produce comparable amounts of caliper, SAT capacity, and void volume when using the non-premium furnish as well as with the premium furnish. This is a very beneficial result as it demonstrates that the Fabric 42 can achieve outstanding results with a lower cost, non-premium furnish. Because Fabric 42 has extra-long warp yarn knuckles, as with the other extra-long warp yarn knuckle fabrics described above, the products made with Fabric 42 may have multiple indented bars extending in a CD direction. The indented bars are again the result of folds being created in the areas of the web that are moved into the pockets of the structuring fabric.
• the aspect ratio of the length of the knuckles and the length across the pocket even further enhances the formation of the folds/indented bars. This is because the web is semi-restrained on the long warp knuckles while being more mobile within the pockets of Fabric 42. The result is that the web can buckle or fold at multiple places along each pocket, which in turn leads to the CD indented bars seen in the products.
• the indented bars formed in absorbent sheets made from Fabric 42 can be seen in Figures 22A-22E.
• These figures are images of the air-side of products made with Fabric 42 at different fabric creping levels but with no vacuum molding.
• the MD is in the vertical direction in all of these figures.
• the products in Figures 22A-22E are characterized by having parallel and near-continuous lines of projected regions substantially extending in the MD, with each of the extended projected regions including a plurality of indented bars extending across the projected regions in a substantially CD of the absorbent sheet.
• These projected regions correspond to lines of pockets extending in the MD of Fabric 42.
• Between the projected regions are connecting regions that also extend substantially in the MD.
• the connecting regions correspond to the long warp yarn knuckles of Fabric 42.
• FIG. 22A The product in Figure 22A was made with a fabric crepe of 25%.
• the indented bars are very distinct. It is believed that this pattern of indented bars is the result of the fiber network on Fabric 42 experiencing a wide range of forces during the creping process, including in-plane compression, tension, bending, and buckling. All of these forces will contribute to the fiber mobility and fiber moldability, as discussed above. And, as a result of the near continuous nature of the projected regions extending in the MD, the enhanced fiber mobility and fiber moldability can take place in a near continuous manner along the MD.
• Figures 22B-22E show the configuration of products with less fabric creping as compared to the product shown in Figure 22A.
• the fabric crepe level used to form the depicted product was 15%
• the fabric crepe level was 10%
• in Figure 22D the fabric crepe level was 8%
• in Figure 22E the fabric crepe level was 3%.
• the amplitude of the folds/indented bars can be seen to decrease with the decreasing fabric crepe level.
• the frequency of the indented bars remains about the same through the fabric crepe levels. This indicates that the web is
• Figures 22A-22E show that the high pocket aspect ratio of Fabric 42 has the ability to uniformly exert decompacting energy to the web such that fiber mobility and fiber moldability are promoted over a wide fabric creping range. And, this fiber mobility and fiber moldability is a very significant factor in the outstanding properties, such as caliper and SAT capacity, found in the absorbent sheets made with Fabric 42.
• Figures 23 A-24B are scanning electron microscopy images of the air sides of a product made with Fabric 42 ( Figures 23 A and 24A) and a comparison product made with Fabric 45
• FIGS 23B and 24B In these cases, the products were made with 30% fabric crepe and maximum vacuum molding.
• the center regions of the images in Figures 23 A and 23B show areas made in the pockets of the respective fabrics, with areas surrounding the center regions corresponding to regions formed on knuckles of the respective fabrics.
• the cross sections shown in Figures 24A and 24B extend substantially along the MD, with an extended projected region of the Fabric 42 product being seen in Figure 24 A and with multiple domes (as formed in multiple pockets) being seen in the Fabric 45 product shown in Figure 24B. It can very clearly be seen that the fibers in the product made with Fabric 42 are much less densely packed than the cellulose fibers in the product made with Fabric 45. That is, the center dome regions in the Fabric 45 product are highly dense— as dense, if not more dense, than the connecting region surrounding the pocket region in the Fabric 42 product.
• Figures 24A and 24B show the fibers to be much looser, i.e., less dense, in the Fabric 42 product than in the Fabric 45 product, with distinct fibers springing out from the Fabric 42 product structure in Figure 24A.
• Figures 23 A-24B thereby further confirm that that Fabric 42 provides for a large amount of fiber mobility and fiber moldability creping process, which in turn results in regions of significantly reduced density in the absorbent sheet products made with the fabric.
• the reduced density regions provide for greater absorbency in the products.
• the reduced density regions provide for more caliper as the sheet becomes more "puffed out" in the reduced density regions.
• the puffy, less dense regions will result in the product feeling softer to the touch.
• Trial 22 only formed a one-ply product, but was otherwise converted in the same manner as the other trials.
• the long warp yarn knuckle structuring fabrics described herein can be used in methods that provide products having outstanding combinations of properties.
• the long warp yarn knuckle structuring fabrics described herein can be used in conjunction with the non-TAD process described generally above and specifically set forth in the aforementioned '563 patent, (wherein the papermaking furnish is compactively dewatered before creping) to form an absorbent sheet that has SAT capacities of at least about 9.5 g/g and at least about 500 g/m 2 . Further, this absorbent sheet can be formed in the method while using a creping ratio of less than about 25%.
• the method and long warp yarn knuckle structuring fabrics can be used to produce an absorbent sheet that has SAT capacities of at least about at least about 10.0 g/g and at least about 500 g/m 2 , has a basis weight of less than about 30 lbs/ream, and a caliper 220 mils/8 sheets. We believe that this type of method has never created such an absorbent sheet before.
• the absorbent sheets made using Fabric 42 in the trials shown in TABLES 14-16 have an outstanding combination of properties, in particular, outstanding caliper and absorbency.
• Figures 25A and 25B indicate characteristics of further structuring fabrics according to embodiments of our invention.
• the Fabrics 46-52 shown in Figures 25A and 25B have long warp yarn knuckles, which range from about 2.4 mm to about 5.7 mm.
• Fabric 46-52 have high PVDI-KR values, ranging from about 41 to about 123.
• the Fabrics 46-52 also demonstrate another aspect of our invention related to positioning of the knuckles on the web-contacting surface of structuring fabrics.
• the knuckles in Fabrics 46-52 are positioned relative to each other such that straight lines can be drawn through the centers of a plurality of the knuckles.
• One such line LI is shown in Figure 26, which is a detailed view of the pressure imprint of Fabric 50.
• the angle a of line LI relative to a line MDL that runs along the MD of the fabric is about 15°.
• warp yarn knuckle lines can be between about 10° to about 30° relative to an MD line, and in more specific embodiments, the warp yarn knuckle lines can be between about 10° to about 20° relative to an MD line.
• the angles of the warp yarn knuckle lines for Fabrics 46-52 are given in Figures 25 A and 25B. It should also be noted that some of the other fabrics described herein include similar angled lines of warp yarn knuckles, including, for example, Fabric 42 shown in Figure 13.
• FIG. 27A This fiber mobility of a structuring fabric that has angled warp yarn knuckle lines is demonstrated in Figure 27A, and this fiber mobility can be compared to other structuring fabric configurations as shown in Figures 27B and 27C.
• the fibers are moved to the fold formations 4002 and 5002 shown in these figures, for example, during a creping operation, such as when the web 116 is transferred from the backing roll 108 to the structuring fabric 112 in the creping nip 120, as shown in Figure 1 and as described above.
• Figure 27B illustrates the case of an MD knuckle 4000 in a structuring fabric.
• FIG. 27C shows how a CD knuckle 5000 of a structuring fabric also has a localized densification zone as a result of web folds 5002 piling up against an edge 5004 of the knuckle 5000.
• the knuckles 6000 in the angled warp yarn lines shown in Figure 27A result in a much different fold formations than the fold formations illustrated in Figures 27B and 27C.
• a strain field arises though the combination of the movement of the knuckles 6000 and the adhesion of the web 116 to the backing roll 108.
• the strain field is localized to the pocket regions between the knuckles 6000.
• the strain field arises because of the creping ratio speed differential in the web transfer from the transfer surface to the structuring fabric: in the creping nip, portions of the web are pulled in a downstream direction by the faster moving transfer surface, while other portions of the web are effectively held up by the slower moving knuckles 6000.
• the web is, for example, 40% to 45% solids, which means that the web will behave in a substantially viscous manner.
• fibers of the web in the strain field can be permanently repositioned relative to each other— after exiting the creping operation, the fibers do not recover to their relative positioning before they entered the strain field.
• This fiber mobilization in the strain field increases the fiber-fiber distance, and thereby weakens the bonds between the fibers so that the web can be molded more easily.
• the result is that the fibers are distributed in curved folds in the pockets between the knuckles 6000.
• the curved folds are an indication that fiber mobilizing work has occurred in the pockets.
• the curved folds are shaped such that apexes 6003 of the curved folds are positioned downstream in the MD, and ends of the curved folds are offset in the MD, with ends 6007 of the curved folds being positioned upstream in the MD relative to the other ends 6009 of the curved folds.
• the curved folds shown in Figure 27A are significantly less dense than the piles of fibers formed at the edges of MD and CD knuckles in structuring fabrics not having angled warp yarn lines shown in Figures 27B and 27C.
• absorbent sheets have greatly improved softness and absorbency because of the reduced densification of the curved folds, which in turn relates to the fiber mobilization discussed above.
• the shapes of the curved folds are also related to the distances Dl between the knuckles 6000. As will be appreciated by those skilled in the art, if the knuckles 6000 are too close, there will not be enough room in the pocket between the knuckles 6000 for the fibers to move into the less dense, curved folds. On the other hand, if the knuckles are too far apart, many of the fibers will not be subjected to the strain field action of the faster moving transfer surface and the slower moving knuckles, and thus, fewer, less pronounced, curved folds may be formed in the web and the resultant absorbent sheet.
• the distances Dl between the centers of two adjacent knuckles 6000 in different warp yarn knuckle lines can be about 1.5 mm to about 4.0 mm. In a specific embodiment, the distances Dl are about 2.0 mm. With the 2.0 mm distance between the knuckles 6000, there is about 1.5 mm of room in the pocket region between the two adjacent knuckles 6000.
• Figures 28A-28E are photographs of absorbent basesheets made with a structuring fabric having angled warp yarn knuckle lines, with a papermaking machine having the general configuration shown in Figure 1, using the non-TAD process described generally above (and specifically set forth in the aforementioned '563 patent), and with the parameters shown in TABLE 4 above.
• Different creping ratios i.e., fabric crepe %) and different molding box vacuums were used for each of the basesheets shown in Figures 28A-28E.
• the basesheet in Figure 28A was made with a 25% crepe ratio and a molding box vacuum of 2 in. Hg
• the basesheet in Figure 28B was made with a 25% crepe ratio and a molding box vacuum of 8 in.
• the basesheet in Figure 28C was made with a 30% crepe ratio and a molding box vacuum of 10 in. Hg, and the basesheet in Figure 28D was made with a 25% crepe ratio and a molding box vacuum of 8 in. Hg.
• the basesheet shown in Figure 28E was made with a 20% crepe ratio, but no molding box vacuum. Note, as there is no vacuum molding used in the production of the basesheet shown in Figure 28E, the basesheet is also indicative of the structure of web following the creping operation in the papermaking process. That is, the web in the papermaking process would have the same general curved fold formations as the basesheet product shown in Figure 28E.
• creping ratios may be used in conjunction with structuring fabrics having angled warp yarn knuckle lines in other embodiments of our invention.
• the creping ratio used with an angled warp yarn knuckle line fabric is between about 3% and about 100%, in more specific embodiments, the creping ratio is between about 3% to about 50%, in even more specific embodiment, the creping ratio is between about 5% and 30%.
• Curved folds can clearly be seen in the projected regions of the basesheets shown in Figures 28A-28E.
• the MD of the sheets is in the vertical (i.e., up and down) direction, with the upstream side of the sheets being at the top of the pictures and the downstream side of the sheets being at the bottom of the figures.
• Figure 28A some of the curved folds have been marked with dotted lines.
• the ends of the curved shapes are unsymmetrical: one end of the curved folds is positioned more downstream than the other end of the curved folds.
• the curved folds extend between these two ends to an apex that is at a downstream most part of the curved folds. And, the ends of the curved folds are positioned adjacent to connecting regions, which correspond to the knuckles of the fabric.
• Curved folds can also be seen in the absorbent sheets shown in Figures 22A and 22E. As previously noted, the absorbent sheets in these figures were formed using Fabric 42, which includes angled lines of warp yarn knuckles. Further, the curved folds can be seen in the soft x-ray images shown in Figures 21 A and 2 IB.
• Figures 28A-28E also show that multiple curved folds are formed in each of the projected regions.
• the multiple curved folds are a result of the extended length in the MD direction of the pockets in which the domed regions are formed, and, thus, the curved folds are also related to the length of the warp yarn knuckles.
• multiple indented bars are formed between the multiple curved folds in the projected regions of the absorbent sheets shown in Figures 28A-28E. Such indented bars can be seen between the curved folds in the absorbent sheets shown in Figures 28A-28E.
• the connecting regions connect the projected regions having the curved folds can also be seen in the photographs of the basesheets shown in Figures 28A-28E. These connecting regions largely correspond to the parts of the sheet that were formed on the knuckles of fabrics used to make these sheets, as well as parts of the sheet that were formed in regions adjacent to the knuckles and pockets.
• An aspect of the connecting regions of the basesheet according to our invention is highlighted in Figure 28 A, wherein regions adjacent to upstream ends of the projected regions are circled. It can be seen that the sheet has folded in these circled regions. These folds are formed because of a z-direction slope in the warp yarns, and lack of CD knuckles, as discussed above.
• the web can slide into these parts of the connecting regions in the papermaking process, thereby creating the folds.
• the folds in the connecting regions act to further reduce the density of the fibers, thereby further improving properties of the absorbent sheets.
• a radius of curvature for the curve folds can be calculated. Specifically, circles can be drawn such that arcs of the circles align with the curved folds. As is evident from the photographs shown in Figures 28A-28E, the leading (downstream) edges of the curved folds are most prominent, and, thus, it is easiest to draw the circles such that the arcs align with the leading edges.
• Figure 29 is the same photograph as Figure 28A, additionally showing circles with arcs aligned with the leading edges of some of the curved folds. From such circles, and using the scale of the photograph, an average radius of curvature for the curved folds may easily be calculated. In embodiments of our invention, we have found that the radius of curvature for the curved folds averages about 1.2 mm, with the radiuses ranging between about 0.5 mm and about 2.0 mm. As discussed above, the curved folds are formed as a result of a localized strain field that arises when a creping operation is performed with an angled warp yarn knuckle fabric according to our invention.
• a normalized fold curvature ratio can be calculated as the radius of curvature for a curved fold divided by a radius of a circle drawn within the projected regions. The lower the normalized fold curvature ratio, the more effective the strain field has been to curve the folds. And, we believe that with a more effectively formed fold curvature, the absorbency and softness of the absorbent sheet are improved.
• FIG. 30A An absorbent sheet according to our invention is shown in Figure 30A, and a commercially-available comparison absorbent sheet is shown in Figure 30B.
• Figure 30A an arc has been drawn to match one of the curved folds. From this and other similarly drawn arcs, the average radius of curvature for the curved folds may be calculated, as discussed above.
• Figure 3 OB an arc has been drawn in Figure 3 OB to match a slight curvature that can be seen in the fold formations, and an average radius for this absorbent sheet may thereby be calculated from this and similar arcs.
• the full circles in Figures 30A and 3 OB have been drawn within the projected regions, with opposite points of the circles aligning with points on opposite sides of the projected regions in which the curved fold formations appear.
• the circles are the maximum size that can be fit within the projected regions, and the radiuses of these circles are therefore half of the distance across the projected regions in the CD of the absorbent sheet.
• the normalized fold curvature ratio can then be calculated for the absorbent sheets shown in Figures 30A and 30B as the ratio of the calculated average radius of curvature and the radius of curvature for the maximum circle size within the projected regions.
• the calculated average radius of curvature is about 1.2 mm
• the normalized fold curvature ratio is about 1.9.
• the calculated average radius of curvature is about 4.55 and the normalized fold curvature ratio is about 4.5.
• the normalized fold curvature ratio is less than about 4, and more particularly, from about 0.5 to about 4. In more specific embodiments, the normalized fold curvature ratio is from about 1 to about 3. As evidence by the absorbent sheet shown in Figure 3 OA, embodiments of our invention may have a specific normalized fold curvature ratio around about 2. When the normalized fold curvature ratio is in these ranges, we believe that a significant amount of fiber mobilization has occurred for the given fabric. Thus, as also discussed above, the fiber mobilization leads to better properties in the paper product, such as good absorbency.
• the invention can be used to produce desirable paper products such as hand towels or toilet paper.
• the invention is applicable to the paper products industry.

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