Patent Application
20080264592
The present invention relates generally to the reduction of dust in papermaking processes through the disruption of the flow of dust laden air in the boundary layer near the surface of a paper web. More specifically, the present invention relates to a creping foil having pipes for the propulsion of fluid integrally mounted thereon.
Dust can be generated when a paper web is separated from a Yankee dryer by a creping blade. Much of the dust is carried along the web in a boundary layer of air which forms due to the rapid movement of the web away from the Yankee dryer. The dust in the boundary layer oftentimes spreads into the areas around the paper machine or other equipment and may cause unwanted contamination of those parts of the paper machine.
A number of problems may be related to the production, and presence, of dust in a paper machine. For example, during printing operations unwanted dust can reduce the aesthetic quality of the final product by mixing with, or getting caught in, printing ink. Relatively high amounts of dust may also be a source of physical irritation for any person who may be in close enough proximity to inhale it. Further, dust may present a fire hazard, can be the cause of increased maintenance costs, premature equipment wear and sheet breaks.
Without being limited by theory, it is thought that dust can be formed from paper fibers which can be liberated from the paper web as a paper web impacts the surface of a creping blade. Upon liberation from the paper web, the dust may be drawn into the fluid (air) boundary layer traveling along the surface of the moving paper web. Without wishing to be limited by theory, it is thought that that approximately 90% of dust that is formed at the creping blade is drawn into the above-mentioned boundary layer.
The prior art methods of removing dust that results from the creping of paper off a Yankee dryer include the use of large vacuums or high horsepower fan-driven dust extraction systems that collect and/or separate dust from the surrounding air. However, without being limited by theory, it is thought that the forces exerted onto a paper web by fans or vacuums may cause loss of sheet control or tearing of the paper web.
Thus, there exists the need for an efficient device and method to control the migration of dust in a papermaking process that provides a minimal level of disruption to the papermaking process and in particular, to the paper web.
In one embodiment the present invention relates to a creping foil comprising: a machine direction, cross machine direction, and Z-direction normal to a plane formed by machine direction and cross machine directions. The creping foil further comprises a front face, back face, and bottom side. The front face comprises one or more top conduits having one or more upper pipes integrally mounted therein; the one or more upper pipes are rotatable about an axis in the cross machine direction and have one or more upper diameter holes. The bottom side comprises one or more bottom conduits having one or more lower pipes integrally mounted therein. The one or more lower pipes are rotatable about an axis in the cross machine direction and have one or more lower diameter holes.
In another embodiment the present invention relates to a creping foil comprising: a machine direction, cross machine direction, and Z-direction normal to a plane formed by machine direction and cross machine directions. The creping foil further comprises a front face, back face, bottom side, and two or more side faces. The front face comprises one or more top conduits having one or more upper pipes integrally mounted therein; the one or more upper pipes are rotatable about an axis in the cross machine direction and have one or more upper diameter holes. The bottom side comprises one or more bottom conduits having one or more lower pipes integrally mounted therein. The one or more lower pipes are rotatable about an axis in the cross machine direction and have one or more lower diameter holes. One or more of the side faces comprises one or more creping foil pivots.
While the specification concludes with claims that particularly point out and distinctly claim the present invention, it is believed that the present invention will be understood better from the following description of embodiments, taken in conjunction with the accompanying drawings, in which like reference numerals identify identical elements.
Without intending to limit the invention, embodiments are described in more detail below:
“Doctor blade” or “blade” as used herein refers to a blade that is disposed adjacent to a piece of equipment so that the doctor blade can remove a material that may be disposed on the piece of equipment. Doctor blades are commonly used in many different industries for many different purposes. Examples of materials include, but are not limited to: tissue webs, paper webs, glue, residual buildup, pitch, and combinations thereof. Examples of equipment include, but are not limited to: drums, plates, Yankee dryers, rollers, and combinations thereof. Exemplary industries that use doctor blades include, but are not limited to: papermaking, nonwoven manufacture, tobacco, and printing, coating and adhesives processes.
“Creping blade” or “creper blade” as used herein, refers to a doctor blade used in the papermaking industry to remove a paper web from a drum and to provide some “crepe” or fold to the web. Creping blades can have the dual function of removing a web from a piece of equipment, such as, for example a Yankee dryer, and providing the web with crepe.
“Creping foil” or “Creping blade foil” or “creper blade foil” or “creper foil” or “foil” as used herein, refers to a web-support structure that may be positioned anywhere in the dry end of a papermaking machine in which mechanical action is performed on a paper web. In one embodiment, the creping foil may be positioned in relatively close proximity to a creping blade in a papermaking machine. In one embodiment, the creping foil can serve as a means to improve sheet control as a paper web leaves the Yankee dryer after it contacts with the creping blade. In another embodiment, the creping foil disrupts the dust-containing boundary layer that forms around the paper web as it leaves the creping blade. In one embodiment, the creping foil is positioned under the paper web during operation. In another embodiment, the creping foil is positioned above the paper web during operation.
“Fluid” as used herein, refers to any matter having particles that may continually deform or flow under an applied shear stress regardless of the magnitude of the applied stress.
“Yankee dryer” or “Yankee roll” or “Yankee” as used herein, refers to a drum for drying paper webs that may not be strong enough to endure numerous felt transfers. The Yankee dryer dries paper as it comes off the wet end of the papermaking machine by pressing one side of the paper web against a cylinder that is typically heated with steam. In some embodiments, the web is glued to the Yankee to keep the web under control. In some embodiments the Yankee dryer may be a cylindrical metal drum having a diameter of from about 3.5 to about 5.5 meters. While on the Yankee dryer, the paper web goes from about 30% dryness to about 95% dryness.
As used herein, “Machine Direction” or “MD” means the direction parallel to the flow of the fibrous structure or paper web through a papermaking machine and/or product manufacturing equipment.
As used herein, “Cross Machine Direction” or “CD” means the direction perpendicular to, and coplanar with, the machine direction of the paper web and/or fibrous structure product comprising the fibrous structure.
As used herein, “Z-direction” means the direction normal to a plane formed by machine direction and cross machine directions.
“Sheet control” as used herein, refers to the lack of vibrations, turbulence, edge flipping, flutter, or weaving of the web that result in a loss of control at higher speeds.
Paper making fibers useful in the present invention include cellulosic fibers commonly known as wood pulp fibers. Applicable wood pulps include chemical pulps, such as Kraft, sulfite and sulfate pulps; mechanical pulps including groundwood, thermo-mechanical pulp; chemical-thermo-mechanical pulp; chemically modified pulps, and the like. Chemical pulps, however, may be preferred in tissue towel embodiments since they are known to those of skill in the art to impart a superior tactile experience and softness to tissue sheets made therefrom. Pulps derived from deciduous trees (hardwood) and/or coniferous trees (softwood) can be utilized herein.
Such hardwood and softwood fibers can be blended or deposited in layers to provide a stratified paper web. Exemplary layering embodiments and processes of layering are disclosed in U.S. Pat. Nos. 3,994,771 and 4,300,981. Additionally, fibers derived from non-wood pulp such as cotton linters, bagesse, and the like, can be used. Additionally, fibers derived from recycled paper, which may contain any or all of the pulp categories listed above, as well as other non-fibrous materials such as fillers and adhesives used to manufacture the original paper product may be used in the present web. In addition, fibers and/or filaments made from polymers, specifically hydroxyl polymers, may be used in the present invention. Non-limiting examples of suitable hydroxyl polymers include polyvinyl alcohol, starch, starch derivatives, chitosan, chitosan derivatives, cellulose derivatives, gums, arabinans, galactans, and combinations thereof. Additionally, other synthetic fibers such as rayon, lyocel, polyester, polyethylene, and polypropylene fibers can be used within the scope of the present invention. Further, such fibers may be latex bonded. Other materials are also intended to be within the scope of the present invention as long as they do not interfere or counter act any advantage presented by the instant invention.
Synthetic fibers useful herein include any material, such as, but not limited to, those selected from the group consisting of polyesters, polypropylenes, polyethylenes, polyethers, polyamides, polyhydroxyalkanoates, polysaccharides, and combinations thereof. The synthetic fiber may comprise a polymer. The polymer may be any material, such as, but not limited to, those materials selected from the group consisting of polyesters, polyamides, polyhydroxyalkanoates, polysaccharides and combinations thereof. More specifically, the material of the polymer segment may be selected from the group consisting of poly(ethylene terephthalate), poly(butylene terephthalate), poly(1,4-cyclohexylenedimethylene terephthalate), isophthalic acid copolymers (e.g., terephthalate cyclohexylene-dimethylene isophthalate copolymer), ethylene glycol copolymers (e.g., ethylene terephthalate cyclohexylene-dimethylene copolymer), polycaprolactone, poly(hydroxyl ether ester), poly(hydroxyl ether amide), polyesteramide, poly(lactic acid), polyhydroxybutyrate, and combinations thereof.
Further, the synthetic fibers can be a single component (i.e., single synthetic material or mixture makes up entire fiber), bi-component (i.e., the fiber is divided into regions, the regions including two or more different synthetic materials or mixtures thereof and may include co-extruded fibers) and combinations thereof. It is also possible to use bicomponent fibers, or simply bicomponent or sheath polymers. Nonlimiting examples suitable bicomponent fibers are fibers made of copolymers of polyester (polyethylene terephthalate)/polyester (polyethylene terephthalate) (otherwise known as “CoPET/PET” fibers), which are commercially available from Fiber Innovation Technology, Inc., Johnson City, Tenn. These bicomponent fibers can be used as a component fiber of the structure, and/or they may be present to act as a binder for the other fibers present. Any or all of the synthetic fibers may be treated before, during, or after the process of the present invention to change any desired properties of the fibers. For example, in certain embodiments, it may be desirable to treat the synthetic fibers before or during the papermaking process to make them more hydrophilic, more wettable, etc.
The paper web may comprise a tissue-towel paper product known in the industry. Embodiment of these substrates may be made according U.S. Pat. Nos.: 4,191,609, 4,300,981, 4,191,609, 4,514,345, 4,528,239, 4,529,480, 4,637,859, 5,245,025, 5,275,700, 5,328,565, 5,334,289, 5,364,504, 5,527,428, 5,556,509, 5,628,876, 5,629,052, 5,637,194, and 5,411,636; EP 677612; and U.S. Patent App. No. 2004/0192136A1.
The paper web may be manufactured via a wet-laid making process where the resultant paper web may be comprised of fibrous structure selected from the group consisting of: through-air-dried fibrous structure plies, differential density fibrous structure plies, wet laid fibrous structure plies, air laid fibrous structure plies, conventional fibrous structure plies, and combinations thereof.
Optionally, the paper web may be foreshortened by creping or by wet microcontraction. Creping and/or wet microcontraction are disclosed in U.S. Pat. Nos.: 6,048,938, 5,942,085, 5,865,950, 4,440,597, 4,191,756, and 6,187,138.
The substrate which comprises the paper web may be cellulosic, non-cellulosic, or a combination of both. The substrate may be conventionally dried using one or more press felts or through-air dried. If the substrate which comprises the paper web is conventionally dried, it may be conventionally dried using a felt which applies a pattern to the paper as taught by commonly assigned U.S. Pat. No. 5,556,509 and PCT Application WO 96/00812. The substrate which comprises the paper web may also be through air dried. A suitable through air dried substrate may be made according to commonly assigned U.S. Pat. No. 4,191,609.
In one embodiment, the substrate which comprises the paper web may be through air dried on a belt having a patterned framework. The belt according to the present invention may be made according to any of commonly assigned U.S. Pat. Nos. 4,637,859, 4,514,345, 5,328,565, and 5,334,289.
The forming section 41 of the papermaking machine 21 comprises a headbox 50; a loop of fine mesh backing wire or fabric 51 which is looped about a vacuum breast roll 52, over vacuum box 70, about rolls 55 through 59, and under showers 60. Intermediate rolls 56 and 57, backing wire/fabric 51 is deflected from a straight run by a separation roll 62. Biasing means not shown are provided for moving roll 58 as indicated by the adjacent arrow to maintain fabric/wire 51 in a slack obviating tensioned state.
The intermediate carrier section 42 comprises a loop of forming and carrier fabric 26 which is looped about rolls 62 through 69 and about a portion of roll 56. The forming and carrier fabric 26 also passes over vacuum boxes 70 and 53, and transfer head 25; and under showers 71. Biasing means are also provided to move roll 65 to obviate slack in fabric 26. Juxtaposed portions of fabrics 51 and 26 extend about an arcuate portion of roll 56, across vacuum box 70, and separate after passing over an arcuate portion of separation roll 62. In one embodiment, forming and carrier fabric 26 is identical to backing wire/fabric 51 except for the lengths.
The pre-dryer/imprinting section 43 of papermaking machine 21 comprises a loop of transfer fabric or imprinting fabric 28. Transfer/imprinting fabric 28 is looped about rolls 77 through 86; passes across transfer head 25 and vacuum box 29; through a blow-through pre-dryer 88; and under showers 89. Additionally, not shown is a biasing mechanism for biasing roll 79 towards the adjacent Yankee dryer 91 with a predetermined force per lineal inch to effect imprinting the knuckle pattern of fabric 28 in paper web 30 in the manner of, and for the purpose disclosed in, U.S. Pat. No. 3,301,746. Not shown is a biasing mechanism for moving roll 85 as indicated by the adjacent arrow to obviate slack in fabric 28.
The drying/creping section 44 of papermaking machine 21 comprises Yankee dryer 91, adhesive applicator 92, creping blade 93, creper foil 700, reel roll 94, and dust collection device 99.
V1 is the velocity of the papermaking fabrics 51 and 26. V2 is the velocity about the transfer/printing rolls 77 through 86. V3 is the velocity of the calendar assembly 45. V4 is the reel velocity of the reel roll 94.
The use of a foil or other web support devices positioned adjacent to a Yankee dryer above a creping blade is known in the art. An example of a foil being used to stabilize the paper web as it leaves the creping blade is described in U.S. Pat. No. 5,891,309. It should be noted that the use of a creping foil as described herein is not limited to use with a Yankee dryer, but the creping foil can be used anywhere in the dry end of the papermaking process, particularly in any area where there is some mechanical trauma exerted onto the paper web.
The creping foil 700 further comprises a top edge 713, top side 770, and bottom side 720. In one embodiment, the creping foil 700 further comprises an apex 712, wherein the apex 712 is defined the surface of creping foil 700 that connects the highest points (in the Z-direction) of the opposing side faces 714 of the creper foil. In some embodiments, the apex 712 is the same as the top edge 713. In one embodiment, the creping foil 700 further comprises one or more top conduits 710 that can be located on the front face 730 of the creping foil 700. In another embodiment, the creping foil 700 further comprises one or more bottom conduits 715 that can be located on the bottom side 720 of the creping foil 700. In one embodiment the creping foil 700 further comprises one or more upper pipes 714 that can be integrally mounted in a top conduit 710. In one embodiment, the upper pipe 714 comprises one or more openings, or upper diameter holes 711, for transport of a fluid through an upper pipe 714 into through an upper diameter hole 711. In one embodiment the creping foil 700 comprises one or more lower pipes 717 that can be integrally mounted in the interior of a lower conduit 715. In one embodiment, the lower pipe 717 comprises one or more openings, or lower diameter holes 716, for transport of a fluid through a lower pipe 717. In some embodiments, the upper pipe 714 and/or lower pipe 717 can be rotated about axes in the cross-machine direction such that the upper diameter holes 711 and lower diameter holes 716 can face at any angle. In one embodiment, there is only one upper diameter hole 711 and/or lower diameter hole 716 which can be a continuous line in the cross machine direction. In this embodiment the width of the hole is from about 0.005″ (about 0.0127 cm) to about 0.5″ (about 1.27 cm). In another embodiment, the upper diameter holes 711 and/or lower diameter holes 716 are circular and have a diameter of from about 0.005″ (about 0.0127 cm) to about 0.5″ (about 1.27 cm). In one embodiment, the upper diameter holes 711 and/or lower diameter holes 716 can be spaced a distance of from about ⅛″ to about 4″ apart. The upper diameter holes 711 and/or lower diameter holes 716 can be any shape and can have any spacing. Nonlimiting examples of fluid that can be used as a momentum barrier can be selected from the group consisting of: air, water, nitrogen gas, inert gases, and combinations thereof.
The creping foil 700 of the present invention can be made from any material or materials suitable for the particular purpose of the creper foil, whether the material(s) is now known or later becomes known. For example, a creper foil may be made from a material selected from the group consisting of: stainless steel, carbon steel, alloy metals, aluminum, aluminum alloys, composite materials, plastic, fiberglass, epoxy based, multi-bonded materials, carbon fibers, woven and/or bonded materials, cured and/or baked materials, plastics, wood, and combinations thereof.
As shown in the exemplary embodiment of
In one embodiment, the creping foil 700 can be mounted from about 2 inches (about 5.08 cm) to about 10 inches (about 25.4 cm) in the machine direction away from the creping blade 93. In another embodiment, the creping foil 700 can be mounted from about 3 inches (about 7.62 cm) to about 8 inches (about 20.32 cm) in the machine direction away from the creping blade 93 to disrupt the flow of the boundary layer of air that forms around the web 30 after reaching the point of mechanical trauma 600 on the paper web 30. Without being limited by theory, it is thought that dust released from the point of mechanical trauma 600 on the paper web 30 is most dense when it is initially liberated at the creping blade 93 and is less dense as the distance from the creping blade 93 increases.
All conditioning and testing is performed under TAPPI standard conditions 50.0%±2.0% R.H. and 23.0±1.0° C. (T204 om-88). All samples are conditioned for a minimum of 2 hours before testing.
A papermaking machine of the general configuration shown in
After being creped off the Yankee dryer 91 by the creping blade 93, the paper web 30 passes over a creping foil 700 and continues on to the reel roll 94. The creping foil 700 is located about 3 inches in the machine direction from the creping blade 93. The creping foil 700 has a width of about 234 inches (about 594.36 cm), height of about 10 inches (about 25.4 cm), and a thickness of about 3 inches (about 7.62 cm). The creping foil 700 has a radius of curvature of about 300 inches (about 762 cm). Compressed air is supplied to the upper pipe 714 of the creping foil 700 at a pressure of 8 psig (about 0.544368 atm). Note that gauge pressure differs from the absolute pressure (i.e. actual pressure) as absolute pressure is equal to the gauge pressure plus atmospheric pressure. Air is provided to the lower pipe 716 of the creping foil 700 at a gauge pressure of about 40 inches of water (about 0.098333 atm) with a flow rate of 350 cubic feet per minute (about 9.91 cubic meters per minute).
A dust collection device 99 is located about 100 inches (about 2.54 meters) below the portion of the paper web 30 and about ½ inch (about 1.27 cm) behind the creping blade 93 in the machine direction. The dust collection device 99 draws air from under the paper web 30 using an exhaust fan that draws air at 25000 cubic feet per minute (about 707.921165 cubic meters per minute). The dust collection device 99 has an intake slot of approximately 2.5 inches (about 6.35 cm) in the machine direction and about 220 inches (about 558.8 cm) in the cross machine direction. The intake slot is connected to the fan and a duct which routes the collected air stream through a wet cyclonic separator to remove the dust collected from the air for weighing. The amount of dust collected is weighed after 2 hours of running continuously.
Three runs using the identical conditions were performed and the mean weight is reported.
Papermaking Machine without a Creping Foil
A paper web is made in accordance with the prior example except that no creping foil is used in the creping section of the papermaking machine
Three runs using the identical conditions were performed and the mean weight is reported.
All publications, patent applications, and issued patents mentioned herein are hereby incorporated in their entirety by reference. Citation of any reference is not an admission regarding any determination as to its availability as prior art to the claimed invention.
Herein, “comprising” means the term “comprising” and can include “consisting of” and “consisting essentially of.”
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical dimensions or values recited. Instead, unless otherwise specified, each such dimension or value is intended to mean both the recited dimension or value and a functionally equivalent range surrounding that dimension or value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm”.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
