EP1657052A1 - Procédé permettant d'augmenter la souplesse de bandes de base et produits en découlant - Google Patents

Procédé permettant d'augmenter la souplesse de bandes de base et produits en découlant Download PDF

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Publication number
EP1657052A1
EP1657052A1 EP06000173A EP06000173A EP1657052A1 EP 1657052 A1 EP1657052 A1 EP 1657052A1 EP 06000173 A EP06000173 A EP 06000173A EP 06000173 A EP06000173 A EP 06000173A EP 1657052 A1 EP1657052 A1 EP 1657052A1
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EP
European Patent Office
Prior art keywords
web
base web
shear
base
paper product
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP06000173A
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German (de)
English (en)
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EP1657052B1 (fr
Inventor
Brian Klaubert
Susan E. Smith
Paul Arnold
Michael A Hermans
Phil S Lin
Robert A Drew
Patricia Riedl
Peter J Allen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kimberly Clark Worldwide Inc
Kimberly Clark Corp
Original Assignee
Kimberly Clark Worldwide Inc
Kimberly Clark Corp
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Publication date
Application filed by Kimberly Clark Worldwide Inc, Kimberly Clark Corp filed Critical Kimberly Clark Worldwide Inc
Priority claimed from EP01933422A external-priority patent/EP1282506B1/fr
Publication of EP1657052A1 publication Critical patent/EP1657052A1/fr
Application granted granted Critical
Publication of EP1657052B1 publication Critical patent/EP1657052B1/fr
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    • 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
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H25/00—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
    • D21H25/005—Mechanical treatment
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
    • D21H27/002—Tissue paper; Absorbent paper

Definitions

  • Products made from base webs such as bath tissues, facial tissues, paper towels, industrial wipers, foodservice wipers, napkins, medical pads, and other similar products are designed to include several important properties.
  • the products should have a soft feel and, for most applications, should be highly absorbent.
  • the products should also have good stretch characteristics and should resist tearing.
  • the products should also have good strength characteristics, should be abrasion resistant, and should not deteriorate in the environment in which they are used.
  • the present invention is directed to improvements in base webs and to improvements in processes for making the webs in a manner that optimizes the physical properties of the webs.
  • the present invention is directed to a process for improving the tactile properties, such as softness and stiffness, of base webs without severely diminishing the strength of the webs.
  • the present invention is directed to further improvements in prior art constructions and methods, which are achieved by providing a process for producing base webs, namely base webs containing pulp fibers.
  • the process includes the steps of first forming a base web.
  • the base web can be made from various fibers and can be constructed in various ways.
  • the base web can contain pulp fibers and/or staple fibers.
  • the base web can be formed in a wet-lay process, an air-forming process, or the like.
  • the web is subjected to shear forces sufficient to improve the softness properties of the web.
  • the web is placed in between a first moving conveyor and a second moving conveyor.
  • the first and second moving conveyors are then guided around a shear-inducing roll while the base web is positioned in between the conveyors.
  • the conveyors are sufficiently wrapped around the shear-inducing roll and are placed under a sufficient amount of tension so as to create shear forces that act upon the base web.
  • the shear forces disrupt the web increasing the softness and decreasing the stiffness of the web.
  • the softness of the web is increased without substantially reducing the strength of the web. More particularly, it has been discovered that the process shifts the normal strength-softness curve so as to create webs having unique softness and strength properties.
  • the base web When guided around the shear-inducing roll, the base web should have a moisture content of less than about 10%, particularly less than about 5%,and more particularly less than about 2%.
  • the shear-inducing roll can rotate or can be a stationary device.
  • the shear-inducing roll should have a small effective diameter, such as less than about 10 inches, particularly less than about 7 inches and more particularly from about 2 inches to about 6 inches.
  • the conveyors should be wrapped around the shear-inducing roll at least 30° and particularly from about 50° to about 270°. Further, the amount of tension placed upon the conveyors when wrapped around the shear-inducing roll should be at least 5 pounds per linear inch and particularly from about 10 pounds per linear inch to about 50 pounds per linear inch.
  • the base web can be a stratified web including a middle layer positioned between a first outer layer and a second outer layer.
  • the outer layers can have a tensile strength greater than the middle layer.
  • the outer layers can be made from softwood fibers, while the middle layer can be made from hardwood fibers.
  • the middle layer can have a tensile strength greater than the outer layers. It has been discovered by the present inventors that various unique products can be formed when using stratified base webs as described above.
  • the present inventors have discovered that the process of the present invention produces unique products having improved softness characteristics.
  • base webs made according to the present invention have improved void-volume properties and fuzz-on-edge properties.
  • the present invention is directed to a paper product that includes a nonwoven base web containing pulp fibers.
  • the base web has a void volume greater than 12 g/g.
  • base webs made according to the present invention can have the above void-volume levels even at basis weights greater than 20 gsm, particularly greater than 25 gsm, and more particularly greater than 30 gsm.
  • base webs made according to the present invention can also be improved without substantially decreasing the tensile strength of the webs.
  • base webs having a void volume greater than 12 g/g can also have a geometric mean tensile strength of greater than about 170 g/in.
  • the process of the present invention also improves the fuzz-on-edge properties of the base web.
  • the fuzz-on-edge test measures the amount of fibers present on the surface of the web that are generally aligned in the z-direction.
  • the degree of "fuzziness" of a web has also been measured in a test referred to as a "perimeter per edge length" test as described in European Application No. 0 539 703 which is incorporated herein by reference.
  • a greater fuzz-on-edge generally indicates a softer web. It has been found that base webs made according to the present invention can have a fuzz-on-edge in an amount greater than 2.2 mm/mm, and particularly greater than 2.5 mm/mm.
  • Base webs having the above properties can be single-ply base webs made according to various processes.
  • the base web can be an uncreped, through-air-dried base web.
  • the base web can be dried on a yankee dryer and creped.
  • Base webs processed according to the present invention can have various applications and uses.
  • base webs made according to the present invention can be single ply base webs particularly well suited for use as a bath tissue. Beside bath tissues, however, the base webs can also be used and incorporated into facial tissues, paper towels, industrial wipers, foodservice wipers, napkins, medical pads, diapers, feminine-hygiene products, and other similar products.
  • the present invention is directed to a process for improving the tactile properties of base webs without a subsequent substantial loss in tensile strength.
  • the present invention is also directed to webs made from the process.
  • the process of the present invention is well suited to increasing the softness and decreasing the stiffness of base webs, such as webs containing pulp fibers. Further, in some applications, the caliper of a web can be reduced while still gaining all of the above advantages.
  • the process of the present invention includes the step of subjecting a previously formed base web to a shearing force in an amount sufficient to improve the softness of the web.
  • the base web can be subjected to a shearing force in an amount sufficient to improve the void volume of the web and the fuzz-on-edge properties of the web.
  • a shearing force can be applied to the web by placing the web between a pair of moving conveyors.
  • a conveyor is intended to refer to a flexible sheet, such as a wire, a fabric, a felt, and the like.
  • a speed differential is created between the two conveyors which applies a shearing force to the web.
  • the conveyors can be guided around at least one shear-inducing element, such as a roll, while the web is sandwiched between the two conveyors.
  • the shear-inducing element can rotate or can be stationary and typically has a small effective diameter, such as less than about 10 inches.
  • the moving conveyors have a sufficient amount of wrap around the shear-inducing element and are placed under sufficient tension to create shear forces that act upon the base web. Specifically, passing the conveyors over the shear-inducing element causes a speed differential in the conveyors which creates a shearing force that breaks bonds within the web or otherwise disrupts fiber entanglement within the web, where the web is weakest. Through this process, the softness of the web increases while the stiffness of the web is reduced. Unexpectedly, the present inventors have discovered that this softening occurs with substantially less loss of tensile strength than would be expected at the softness levels obtained.
  • Base webs that may be used in the process of the present invention can vary depending upon the particular application. In general, any suitable base web may be used in the process in order to improve the tactile properties of the web. Further, the webs can be made from any suitable type of fiber.
  • the manner in which the base web of the present invention is formed may vary depending upon the particular application.
  • the web can contain pulp fibers and can be formed in a wet-lay process according to conventional paper making techniques.
  • a wet-lay process the fiber furnish is combined with water to form an aqueous suspension.
  • the aqueous suspension is spread onto a wire or felt and dried to form the web.
  • the base web of the present invention can be air formed.
  • air is used to transport the fibers and form a web.
  • Air-forming processes are typically capable of processing longer fibers than most wet-lay processes, which may provide an advantage in some applications.
  • FIG. 2 one embodiment of a process for producing a base web that may be used in accordance with the present invention is illustrated.
  • the process illustrated in the figure depicts a wet-lay process, although, as described above, other techniques for forming the base web of the present invention may be used.
  • the web-forming system includes a headbox 10 for receiving an aqueous suspension of fibers.
  • Headbox 10 spreads the aqueous suspension of fibers onto a forming fabric 26 that is supported and driven by a plurality of guide rolls 34.
  • a vacuum box 36 is disposed beneath forming fabric 26 and is adapted to remove water from the fiber furnish to assist in forming a web.
  • a formed web 38 is transferred to a second fabric 40, which may be either a wire or a felt.
  • Fabric 40 is supported for movement around a continuous path by a plurality of guide rolls 42.
  • a pick up roll 44 designed to facilitate transfer of web 38 from fabric 26 to fabric 40.
  • the speed at which fabric 40 can be driven is approximately the same speed at which fabric 26 is driven so that movement of web 38 through the system is consistent.
  • the two fabrics can be run at different speeds, such as in a rush transfer process, in order to increase the bulk of the webs or for some other purpose.
  • web 38 is pressed onto the surface of a rotatable heated dryer drum 46, such as a Yankee dryer, by a press roll 43.
  • Web 38 is lightly pressed into engagement with the surface of dryer drum 46 to which it adheres, due to its moisture content and its preference for the smoother of the two surfaces.
  • heat is imparted to the web causing most of the moisture contained within the web to be evaporated.
  • Web 38 is then removed from dryer drum 46 by a creping blade 47. Creping web 38 as it is formed reduces internal bonding within the web and increases softness.
  • the web instead of wet pressing the base web 38 onto a dryer drum and creping the web, the web can be through-air dried.
  • a through-air dryer accomplishes the removal of moisture from the base web by passing air through the web without applying any mechanical pressure.
  • FIG. 3 an alternative embodiment for forming a base web for use in the process of the present invention containing a through-air dryer is illustrated.
  • a dilute aqueous suspension of fibers is supplied by a headbox 10 and deposited via a sluice 11 in uniform dispersion onto a forming fabric 26 in order to form a base web 38.
  • a vacuum box 36 can be disposed beneath the forming fabric 26 for removing water and facilitating formation of the web 38.
  • the base web 38 is then transferred to a second fabric 40.
  • the second fabric 40 carries the web through a through-air drying apparatus 50.
  • the through-air dryer 50 dries the base web 38 without applying a compressive force in order to maximize bulk.
  • the through-air drying apparatus 50 includes an outer rotatable cylinder 52 with perforations 54 in combination with an outer hood 56.
  • the fabric 40 carries the web 38 over the upper portion of the through air drying apparatus outer cylinder 52. Heated air is drawn through perforations 54 which contacts the web 38 and removes moisture.
  • the temperature of the heated air forced through the perforations 54 can be from about 170°F to about 500°F.
  • the base web 38 is placed between a pair of moving conveyors and pressed around a shear-inducing element in accordance with the present invention.
  • a process for improving the tactile properties of a base web in accordance with the present invention is illustrated in Figure 4.
  • the base web 38 is supplied between a first moving conveyor 60 and a second moving conveyor 62.
  • the speed at which the conveyors 60 and 62 are moving is generally not critical to the present invention. For most commercial applications, the conveyors can be moving at a speed of from about 1,000 feet per minute to about 6,000 feet per minute.
  • the base web and the conveyors are guided around a shear-inducing roll 64 by a pair of support rolls 66 and 68.
  • the conveyors 60 and 62 are placed under tension and are wrapped around the shear-inducing roll 64 in amounts sufficient to create shear forces that act upon the base web 38.
  • a speed differential develops in the conveyors. Due to the interaction between the surfaces of the conveyors and the contacting surface of the web, the speed differential of the conveyors can be translated into a speed differential between the two web surfaces.
  • Factors which can affect the web surface/conveyor surface interaction can include but are not limited to, for example, the coefficient of friction at the conveyor surfaces, the tension of the conveyors, and the moisture content of the web.
  • a speed differential between the two web surfaces can create shearing forces which act upon the base web. The shearing forces can break bonds within the web where the web is weakest, which subsequently increases the softness and decreases the stiffness of the web.
  • void volume is a measure of the volume of liquid which can be contained within a sheet. As used herein, void volume is determined according to the POROFIL test described in EXAMPLE 2 below.
  • single-ply webs can be produced having a basis weight of greater than about 20 gsm and a void volume of greater than 11.5 g/g. More specifically, a single-ply web, suitable as a bath tissue, can be produced by the present invention that can have a basis weight of more than about 30 gsm and a void volume of greater than about 12.0 g/g.
  • a fuzz-on-edge test is a test that generally measures the amount of fibers present on the surface of the base web that protrude from the sheet.
  • the fuzz-on-edge is measured according to the test as described in EXAMPLE 2 below. The greater the fuzz-on-edge of a base web, the softer the base web feels. In particular, the fuzz-on-edge corresponds to a greater number of fibers on the surface of the web in the z-direction which provides a "fuzzy" soft feel.
  • Base webs made according to the present invention can have a fuzz-on-edge in an amount greater than about 2.0 mm/mm, particularly greater than 2.2 mm/mm, and more particularly greater than about 2.5 mm/mm.
  • base web 38 when fed around the shear-inducing roll 64, should generally have a low moisture content.
  • the base web 38 should have a moisture content of less than about 10% by weight, particularly less than about 5% by weight, and more particularly less than about 2% by weight.
  • the shear-inducing roll 64 can be a rotating roll having a relatively small diameter. In other embodiments, however, the shear-inducing roll can be a stationary roll.
  • the effective diameter of the shear-inducing roll, for most applications, should be less than about 10 inches, particularly less than about 7 inches, and more particularly from about 2 inches to about six inches.
  • the amount that conveyors 60 and 62 are wrapped around the shear-inducing roll 64 can vary depending upon the particular application and the amount of shear that is desired to be exerted on the web. For most applications, however, the conveyors should be wrapped around the shear-inducing roll in an amount from about 30° to about 270°, particularly from about 50 ° to about 200 °, and more particularly from about 80° to about 180°. In the embodiment illustrated in Figure 4, the amount of wrap placed around the shear-inducing roll can be adjusted by adjusting the position of either the shear-inducing roll 64 or the support rolls 66 and 68. For instance, by moving the shear-inducing roll 64 down closer to the support rolls 66 and 68, the conveyors will wrap around the shear-inducing roll 64 a lesser extent.
  • the amount of tension placed upon the conveyors 60 and 62 can also have an impact on the amount of shear that is exerted on the base web 38.
  • the amount of tension placed upon the conveyors will depend upon the particular application. For most applications, however, the conveyors 60 and 62 should be placed under tension in an amount from about 5 pounds per linear inch to about 90 pounds per linear inch, particularly from about 10 pounds per linear inch to about 50 pounds per linear inch, and more particularly from about 30 pounds per linear inch to about 40 pounds per linear inch.
  • the speed differential should be from about 0.5% to about 5%, and particularly from about 1% to about 3% with conveyor on the outside moving faster than the conveyor contacting the roll.
  • the web can be further processed as desired.
  • the web can be collected onto a reel 69 for later packaging.
  • the tactile properties of the base web can be greatly enhanced, without seriously affecting the strength of the web. Further, in some applications, it has been discovered that the caliper of the web can be dramatically reduced. Caliper reduction without adversely affecting other properties of the web is beneficial in that more material can be placed upon reel 69, which provides various processing benefits.
  • the amount of caliper reduction achieved can be controlled by adjusting numerous variables.
  • the number of shear-inducing rolls, the radius of the rolls, dwell time within the nip, nip pressure, conveyor type and base sheet structure all have an impact on the amount of caliper the process can remove.
  • Percent caliper reduction increases with an increase in dwell time, number of rolls, nip pressure, and fabric mesh. Dwell time can be affected by the secondary variables of speed and wrap angle.
  • Nip pressure can be varied by the secondary variables of fabric tension and roll diameter.
  • Fabric mesh can be varied by using fabrics of differing knuckle surfaces.
  • the system includes a single shear-inducing roll 64. In other embodiments, however, more shear-inducing rolls can be used. For instance, in other embodiments, the conveyors can be wrapped around two shear-inducing rolls, three shear-inducing rolls, and even up to ten shear-inducing rolls. Referring to Figure 5, an alternative embodiment of the present invention is illustrated that includes five shear-inducing rolls.
  • the base web 38 is fed between the first conveyor 60 and the second conveyor 62 and is then wrapped around support rolls 70 and 72 and shear-inducing rolls 74, 76, 78, 80, and 82.
  • shear-inducing rolls can create more shear that is exerted on the base web.
  • the shear-inducing rolls are illustrated as having approximately equal diameters, alternative embodiments may be desired with some or all of the shear-inducing rolls having diameters which are unequal to the others.
  • the total wrap of the conveyors around all of the shear-inducing rolls should be at least 90° for most embodiments. More particularly, especially when using more than two shear-inducing rolls, the total wrap should be greater than 100°, and particularly greater than 120°. The total wrap, however, can increase or decrease depending upon increasing or decreasing the number of shear-inducing rolls respectively.
  • FIG. 6 includes a single shear-inducing roll 100. As shown, conveyors 60 and 62 are guided around the shear-inducing roll 100 by support rolls 102, 104, 106 and 108.
  • the system illustrated in Figure 7 also includes a single shear-inducing roll 110. It should be understood, however, that more shear-inducing rolls can be included in any of the systems illustrated. As shown in Figure 7, shear-inducing roll 110 is supported by a backing roll 112. In order to facilitate the amount of wrap around shear-inducing roll 110, the system further includes support rolls 114 and 116.
  • base webs processed according to the present invention can be made from various materials and fibers.
  • the base web can be made from pulp fibers, other natural fibers, synthetic fibers, and the like.
  • the base web contains pulp fibers either alone or in combination with other types of fibers.
  • the pulp fibers used in forming the web can be, for instance, softwood fibers having an average fiber length of greater than 1 mm and particularly from about 2 to 5 mm based on a length weighted average.
  • Such fibers can include Northern softwood kraft fibers. Secondary fibers obtained from recycled materials may also be used.
  • staple fibers can be added to the web to increase the strength, bulk, softness and smoothness of the web.
  • Staple fibers can include, for instance, polyolefin fibers, polyester fibers, nylon fibers, polyvinyl acetate fibers, cotton fibers, rayon fibers, non-woody plant fibers, and mixtures thereof.
  • staple fibers are typically longer than pulp fibers. For instance, staple fibers typically have fiber lengths of 5 mm and greater.
  • the staple fibers added to the base web can also include bicomponent fibers.
  • Bicomponent fibers are fibers that can contain two materials such as, but not limited to, in a side by side arrangement or in a core and sheath arrangement.
  • the sheath polymer In a core and sheath fiber, generally the sheath polymer has a lower melting temperature than the core polymer.
  • the core polymer in one embodiment, can be nylon or a polyester, while the sheath polymer can be a polyolefin such as polyethylene or polypropylene.
  • Such commercially available bicomponent fibers include CELBOND fibers marketed by the Hoechst Celanese Company.
  • the staple fibers used in the base web of the present invention can also be curled or crimped.
  • the fibers can be curled or crimped, for instance, by adding a chemical agent to the fibers or subjecting the fibers to a mechanical process. Curled or crimped fibers may create more entanglement and void volume within the web and further increase the amount of fibers oriented in the Z direction as well as increase web strength properties.
  • the staple fibers when forming paper products containing pulp fibers, can be added to the web in an amount from about 5% to about 30% by weight and particularly from about 5% to about 20% by weight.
  • the base web of the present invention is not used to make paper products, but instead is incorporated into other products such as diapers, feminine-hygiene products, garments, personal-care products, and various other products, the base web can be made from greater amounts of staple fibers.
  • thermormechanical pulp can also be added to the base web.
  • Thermomechanical pulp refers to pulp that is not cooked during the pulping process to the same extent as conventional pulps.
  • Thermomechanical pulp tends to contain stiff fibers and has higher levels of lignin.
  • Thermomechanical pulp can be added to the base web of the present invention in order to create an open pore structure, thus increasing bulk and absorbency and improving resistance to wet collapse.
  • thermomechanical pulp can be added to the base web in an amount from about 10% to about 30% by weight.
  • a wetting agent is also preferably added during formation of the web.
  • the wetting agent can be added in an amount less than about 1% and, in one embodiment, can be a sulphonated glycol.
  • the fiber furnish used to form the base web can be treated with a chemical debonding agent.
  • the debonding agent can be added to the fiber slurry during the pulping process or can be added directly into the headbox.
  • Suitable debonding agents include cationic debonding agents such as fatty dialkyl quaternary amine salts, mono fatty alkyl tertiary amine salts, primary amine salts, imidazoline quaternary salts, and unsaturated fatty alkyl amine salts.
  • Other suitable debonding agents are disclosed in U.S. Patent No. 5,529,665 to Kaun which is incorporated herein by reference.
  • the debonding agent used in the process of the present invention can be an organic quaternary ammonium chloride.
  • the debonding agent can be added to the fiber slurry in an amount from about 0.1% to about 1% by weight, based on the total weight of fibers present within the slurry.
  • the base web of the present invention may also have a multilayer construction.
  • the web can be made from a stratified fiber furnish having at least three principal layers.
  • the process of the present invention causes web disruption in the area of the web that is weakest. Consequently, one particular embodiment of the present invention is directed to using a stratified base web that contains weak outer layers and a strong center layer. Upon exposure to the shear forces created through the process of the present invention, bonds are broken on the outer surface of the sheet, while the strength of the center layer is maintained. The net effect is a base web having improved softness and stiffness with minimal strength loss.
  • a stratified base web can be used that has outer layers having a greater tensile strength than a middle layer.
  • bonds in the middle layer fail but the integrity of the outer layers is maintained.
  • the resulting sheet simulates, in some respects, the properties of a two-ply sheet.
  • a three-layered headbox generally 10 may include an upper headbox wall 12 and a lower headbox wall 14. Headbox 10 may further include a first divider 16 and a second divider 18, which separate three fiber stock layers. Each of the fiber layers 24, 20, and 22 comprise a dilute aqueous suspension of fibers.
  • debonding agents can be used as described above in order to alter the strength of a particular layer.
  • different fiber furnishes can be used for each layer in order to create a layer with desired characteristics.
  • softwood fibers can be incorporated into a layer for providing tensile strength
  • hardwood fibers can be incorporated into an adjacent layer for creating a weaker tensile strength layer.
  • layers containing hardwood fibers typically have a lower tensile strength than layers containing softwood fibers.
  • Hardwood fibers have a relatively short fiber length.
  • hardwood fibers can have a length of less than about 2 millimeters and particularly less than about 1.5 millimeters.
  • the hardwood fibers incorporated into a layer of the base web include eucalyptus fibers.
  • Eucalyptus fibers typically have a length of from about 0.8 millimeters to about 1.2 millimeters.
  • eucalyptus fibers increase the softness, enhance the brightness, increase the opacity, and increase the wicking ability of the web.
  • hardwood fibers may also be incorporated into the base web of the present invention.
  • Such fibers include, for instance, maple fibers, birch fibers and possibly recycled hardwood fibers.
  • the above-described hardwood fibers can be present in the base web in any suitable amount.
  • the fibers can comprise from about 5% to about 100% by weight of one layer of the web.
  • the hardwood fibers can be present within the lower tensile strength layer of the web either alone or in combination with other fibers, such as other cellulosic fibers.
  • the hardwood fibers can be combined with softwood fibers, with superabsorbent materials, and with thermomechanical pulp.
  • stronger tensile strength layers can be formed using softwood fibers, especially when adjacent weaker tensile strength layers are made from hardwood fibers.
  • the softwood fibers can be present alone or in combination with other fibers.
  • staple fibers such as synthetic fibers, can be combined with the softwood fibers.
  • each layer of a stratified base web in relation to the total weight of the web is generally not critical. In most embodiments, however, the weight of each outer layer will be from about 15% to about 40% of the total weight of the web, and particularly from about 25% to about 35% of the weight of the web.
  • the basis weight of base webs made according to the present invention can vary depending upon the particular application. In general, for most applications, the basis weight can be from about 5 pounds per 2,880 square feet (ream) (8.5 gsm) to about 80 pounds per ream (136 gsm), and particularly from about 6 pounds per ream (10.2 gsm) to about 30 pounds per ream (51 gsm). In one embodiment, the present invention can be used to construct a single ply bath tissue having a basis weight of from about 20 gsm to about 40 gsm.
  • Some other uses of the base webs include use as a wiping product, as a napkin, as a medical pad, as an absorbent layer in a laminate product, as a placemat, as a drop cloth, as a cover material, as a facial tissue, or for any product that requires liquid absorbency.
  • paper webs were produced, placed between two fabrics, and then guided around at least one shear-inducing roll. More particularly, stratified webs were tested which included three layers. The two outer layers of the web were made from eucalyptus fibers. The middle layer, however, contained softwood fibers. The webs were produced using a through-air dryer similar to the system illustrated in Figure 3. The base webs had an average basis weight of about 18.9 Ibs/ream.
  • the webs were then placed in between a pair of fabrics and guided around at least one shear-inducing roll, similar to the configuration illustrated in Figure 4.
  • the base webs were wrapped around 3 shear-inducing rolls at a pressure of 25 pounds per linear inch.
  • the fabrics were wrapped around the shear-inducing rolls in an amount of about 45 °.
  • the diameter of the shear-inducing rolls was varied between 2 inches, 4.5 inches and 10.5 inches. Further, the amount of softwood fibers contained in the web was also varied (middle layer of the web) from 28% by weight to 31 % by weight.
  • GMT geometric mean tensile strength test
  • the tensile strength of samples was determined in the machine direction and in the cross machine direction. The size of the samples tested were 3 inches in width unless indicated to the contrary.
  • each end of a sample was placed in an opposing clamp. The clamps held the material in the same plane and moved apart at a ten inch per minute rate of extension. The clamps moved apart until breakage occurred in order to measure the tensile strength of the sample.
  • the geometric mean tensile strength is then calculated by taking the square root of the machine-direction tensile strength of the sample multiplied by the cross-direction tensile strength of the sample.
  • Tensile strength tests can be performed, for instance, on the Sintech 2 tester, available from the Sintech Corporation of Cary, North Carolina, the Instron Model TM available from the Instron Corporation of Canton, Massachusetts, a Thwing-Albert Model INTELLECT II available from the Thwing-Albert Instrument Company of Philadelphia, Pennsylvania, or SYNERGY 100 available from MTS Systems, Corp. located in Eden Prairie, Minnesota. Results are reported in grams or in grams per inch width of sample.
  • the process of the present invention shifts the strength/softness curve towards creating softer and stronger webs. Further, decreasing the shear-inducing roll diameter further increases the softness of the webs at a given strength.
  • a nonwoven web was formed, placed between two conveyors, and then guided around three small rolls.
  • the web produced was a stratified web including three layers.
  • the center layer was 100% softwood and made up approximately 34% by weight of the total web.
  • the two outer layers were each approximately 33% by weight of the web and were a 3:1 mixture (by weight) of eucalyptus fibers and broke.
  • 5.1 kg/metric ton of total fiber furnish of PROSOFT TQ 1003 debonder obtained from _ Hercules, Inc. was added to the outer layers of the web and 6.0 kg/metric ton of total fiber furnish of HERCOBOND wet strength agent obtained from Hercules, Inc. was added to the center layer.
  • the softwood fibers were refined at a load of 2.75 HP-day/metric ton.
  • the web was produced using a through-air dryer apparatus similar to the system illustrated in Figure 3.
  • the through-air drying apparatus included a Voith t1205-1 fabric for carrying the web through the apparatus.
  • the web entered the through-air drying apparatus at a consistency of approximately 29%, and left the through-air drying section of the process at a consistency of about 98%.
  • the web had a caliper of approximately 32 to 36 mils. Caliper of the web was determined by use of an EMVECO 200A Tissue Caliper Tester. Throughout the experimental procedures, caliper was measured at a load of about 2.00 kPa over an area of about 2500 mm 2 .
  • the web was placed between two conveyors and fed around a set of shear-inducing rolls.
  • One conveyor was a style 960 fabric available from the Asten Johnson Corporation. This fabric was travelling at approximately 1600 ft/min.
  • the other conveyor was a style 866B fabric, also available from the Asten Johnson Corporation. Due to the speed differential created by the presence of the shear-inducing rolls, this second fabric was travelling at approximately 1615 ft/min. Both conveyors were at fabric tensions of about 30-35 pounds per linear inch.
  • the web and the two conveyors traveled together over three shear-inducing rolls, each of which had a 2.25" diameter, the total wrap angle around the three rolls was about 128°.
  • the individual wrap angle for each roll was, 32°, 60°, and 36°, sequentially.
  • the web left the shear-inducing rolls with a caliper of about 20-24 mils.
  • the web was calendered in a rubber/steel configuration with a rubber roll covering of about 40 P&J hardness and a nip load of about 15 pli.
  • the web produced according to the above process was then tested for void volume, geometric mean tensile strength as described in EXAMPLE 1, caliper, and fuzz-on-edge.
  • Void volume of the resultant sheet was determined according to the following void-volume test. First, the sheet was saturated with a non-polar liquid and the volume of liquid absorbed was measured. The volume of liquid absorbed is equivalent to the void volume within the sheet structure. The void volume is expressed as grams of liquid absorbed per gram of fiber in the sheet.
  • the test includes the following steps. For each single-ply sheet sample to be tested, sheets are selected and a 1 inch x 1 inch square (1 inch in the machine direction and 1 inch in the cross machine direction) is cut out. The dry weight of each test specimen is weighed and recorded to the nearest 0.0001 gram.
  • the specimen is placed in a dish containing POROFIL" pore wetting liquid of sufficient depth and quantity to allow the specimen to float freely following absorption of the liquid.
  • POROFIL liquid, having a specific gravity of 1.875 grams per cubic centimeter, available from Coulter Electronics Ltd., Northwell Drive, Luton, Beds., England; Part No. 9902458.
  • the specimen is held at the very edge (1-2 millimeters in) of one corner with tweezers and removed from the liquid. The specimen is held with that corner uppermost and excess liquid is allowed to drip for 30 seconds.
  • the lower corner of the specimen is lightly dabbed (less than 1/2 second contact) with #4 filter paper (Whatman Ltd., Maidstone, England) in order to remove any excess of the last partial drop.
  • the specimen is immediately weighed, within 10 seconds. The weight is recorded to the nearest 0.0001 gram.
  • the fuzz-on-edge test is an image analysis test.
  • the image analysis data are taken from two glass plates made into one fixture. Each plate has a sample folded over the edge with the sample folded in the CD direction and placed over the glass plate. The edge is beveled to 1/16" thickness.
  • the fixture includes a first glass plate 202 and a second glass plate 204.
  • Each of the glass plates have a thickness of 1 ⁇ 4 inch.
  • glass plate 202 includes a beveled edge 206 and glass plate 204 includes a beveled edge 208.
  • Each beveled edge has a thickness of 1/16 inch.
  • the glass plates are maintained in position by a pair of U-shaped brackets 210 and 212. Brackets 210 and 212 can be made from, for instance, 3 ⁇ 4 inch finished plywood.
  • the product sheet exhibited the following characteristics: basis weight - 31.4 gsm (bone dry) geometric mean tensile strength - 531 grams/3" width (177g/in) measured with a 2 inch gap between grips caliper - 0.0159 inches void volume - 12.0 g fluid/g fiber Fuzz-on-Edge (FOE) - 2.165 perimeter ratio/edge length
  • Example 2 An uncreped through-air-dried web was made as described in Example 2, with the exception that the three shear-inducing rolls of Example 2 were replaced with three 4.5" diameter rolls and the total wrap angle around the three rolls was about 90°. Additionally, the web was calendered in a rubber/steel configuration with a rubber roll covering of about 40 P&J hardness and a nip load of about 25 pli.
  • Example 2 An uncreped through-air-dried web was made as described in Example 2, with the exception that the three shear-inducing rolls of Example 2 were replaced with three 4.5" diameter rolls and the total wrap angle around the three rolls was about 163°. Additionally, the web was calendered in a rubber/steel configuration with a rubber roll covering of about 40 P&J hardness and a nip load of about 25 pli.
  • Example 2 An uncreped through-air-dried web was made as described in Example 2, with the exception that the three shear-inducing rolls of example 2 were replaced with three 4.5" diameter rolls and the total wrap angle around the three rolls was about 163°. Additionally, the web was calendered in a rubber/steel configuration with a rubber roll covering of about 40 P&J hardness and a nip load of about 0 pli.
  • Example 2 An uncreped through-air-dried web was made as described in Example 2, with the exception that the three shear-inducing rolls of example 2 were replaced with one 4.5" diameter roll and the total wrap angle around the roll was about 60°. Additionally, the web was calendered in a rubber/steel configuration with a rubber roll covering of about 40 P&J hardness and a nip load of about 100 pli.

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7497925B2 (en) * 2002-11-27 2009-03-03 Kimberly-Clark Worldwide, Inc. Shear-calendering processes for making rolled tissue products having high bulk, softness and firmness
WO2011140628A1 (fr) * 2010-05-12 2011-11-17 Rajan Ahluwalia Procédé de production de papier recyclé
EP3279395B1 (fr) 2012-02-16 2023-09-27 International Paper Company Procédé de fabrication d'une bande de pâte fluff

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3207657A (en) * 1963-01-22 1965-09-21 Huyck Corp Method and apparatus for making paper by contracting the forming carrier to compact the web
EP0539703A1 (fr) * 1991-09-11 1993-05-05 Kimberly-Clark Corporation Article absorbant
EP0613979A1 (fr) * 1993-03-02 1994-09-07 Kimberly-Clark Corporation Papier tissu doux à plusieurs couches et son procédé de fabrication
EP0668152A1 (fr) * 1994-02-18 1995-08-23 Kimberly-Clark Corporation Procédé pour faire du papier bouffant doux p. ex.: mouchoirs en papier et produits en papier ainsi obtenus
US5743999A (en) * 1993-04-12 1998-04-28 Kimberly-Clark Worldwide, Inc. Method for making soft tissue
US5759346A (en) * 1996-09-27 1998-06-02 The Procter & Gamble Company Process for making smooth uncreped tissue paper containing fine particulate fillers

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3207657A (en) * 1963-01-22 1965-09-21 Huyck Corp Method and apparatus for making paper by contracting the forming carrier to compact the web
EP0539703A1 (fr) * 1991-09-11 1993-05-05 Kimberly-Clark Corporation Article absorbant
EP0613979A1 (fr) * 1993-03-02 1994-09-07 Kimberly-Clark Corporation Papier tissu doux à plusieurs couches et son procédé de fabrication
US5743999A (en) * 1993-04-12 1998-04-28 Kimberly-Clark Worldwide, Inc. Method for making soft tissue
EP0668152A1 (fr) * 1994-02-18 1995-08-23 Kimberly-Clark Corporation Procédé pour faire du papier bouffant doux p. ex.: mouchoirs en papier et produits en papier ainsi obtenus
US5759346A (en) * 1996-09-27 1998-06-02 The Procter & Gamble Company Process for making smooth uncreped tissue paper containing fine particulate fillers

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7497925B2 (en) * 2002-11-27 2009-03-03 Kimberly-Clark Worldwide, Inc. Shear-calendering processes for making rolled tissue products having high bulk, softness and firmness
WO2011140628A1 (fr) * 2010-05-12 2011-11-17 Rajan Ahluwalia Procédé de production de papier recyclé
EP3279395B1 (fr) 2012-02-16 2023-09-27 International Paper Company Procédé de fabrication d'une bande de pâte fluff

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