Paper making and fiber liberation – Processes and products – Non-uniform – irregular or configured web or sheet
Reexamination Certificate
1998-11-13
2001-06-19
Fortuna, Jose (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-uniform, irregular or configured web or sheet
C162S109000, C162S117000, C162S205000
Reexamination Certificate
active
06248210
ABSTRACT:
FIELD OF INVENTION
The invention relates to a method for maximizing water removal from an absorbent paper web in a press nip. More particularly, the present invention relates to the use of a shoe press on the Yankee dryer with a pressure profile that maximizes water removal. Still more particularly, the present invention relates to a method for utilizing a very steep pressure drop at and/or following the exit of a nip curve in order to maximize water removal by minimizing rewet. Finally, the present invention relates to a method for increasing paper machine speed by utilizing a press section that maximizes water removal.
BACKGROUND OF THE INVENTION
In modern society, bath tissue, paper towels, facial tissue, and paper napkins (hereinafter referred to as packaged paper products) have been remarkably successfully consumer products. The success of these paper products stems from the ability of manufacturers to consistently enhance product attributes at lower cost and to meet volume demands on a timely basis. Packaged paper products offer consumers an array of attributes necessary to such jobs as performing the daily tasks of wiping up spills, personal cleansing, and cleaning household goods. For example, paper towels are engineered to be absorbent and strong while wet whereas bath tissue products are expected to be soft to the touch yet strong while in use. Absorbency and softness are inversely related to strength, often making it difficult to obtain the right balance of attributes. Accordingly, significant research and development efforts are routinely expended to enhance the quality of these products while continuing to reduce cost by, for example, improving the production of these products. Although numerous schemes have been developed and patented, the search by R&D departments continues to seek out new and innovative methods for improving these products.
There are numerous methods described in the patent literature for improving the quality of packaged paper products. One of the earliest known methods to enhance the quality of consumer paper products is described in U.S. Pat. No. 3,301,746 by Sanford and Sisson, assigned to Procter and Gamble Corporation, and incorporated herein by reference in its entirety. This patent describes a papermaking scheme for enhancing product quality by avoiding overall web compression and by using a pattern array of densified regions in the xy plane of the sheet to enhance product strength.
Other early methods for improving the quality of packaged paper products are described in U.S. Pat. No. 3,812,000 by Salvucci and Yiannos and U.S. Pat. No. 3,821,068 by Shaw. These patents are assigned to Scott Paper Company, each of which is incorporated herein by reference in its entirety. Shaw discloses a papermaking scheme for producing soft tissue by avoiding mechanical compression until the sheet has been dried to at least 80% solids. Salvucci and Yiannos disclose a technique for producing a soft tissue structure by avoiding mechanical compression of an elastomeric containing fiber furnish until the consistency of the web is at least 80% solids.
Thicker more absorbent structures can be made using a low batting papermaking felt as described in U.S. Pat. No. 4,533,457 by Curran et al., assigned to Scott Paper Company, and incorporated herein by reference in its entirety. U.S. Pat. Nos. 5,591,305 and 5,569,358 by Cameron, assigned to James River Corporation, and incorporated herein by reference in their entirety, disclose a lowbatting, high-bulk-generating felt with improved dewatering capabilities.
A more recent method for improving the quality of a through-air-dried sheet is described in U.S. Pat. No. 4,440,597 by Wells and Hensler, assigned to Procter and Gamble Company, and incorporated herein by reference in its entirety. This patent describes a method for increasing the stretch of a paper web by operating the forming section of a paper machine faster than the through air dryer section of the paper machine. As a result of the speed differential, the paper web is inundated into the through air-dryer-fabric leading to enhanced stretch and absorbency properties in the base sheet and resulting product.
Fibers and chemicals can be used to enhance the quality of packaged paper products. For example, U.S. Pat. No. 5,320,710 by Reeves et al., assigned to Fort James Corporation, and incorporated herein by reference in its entirety, describes a new furnish combination extracted from the species Funifera of the genus Hesporaloe in the Agavaceae family. This furnish has fibers which are very long and which have very fine-geometrical attributes known to enhance tissue and towel performance. U.S. Pat. No. 3,755,220 by Freimark and Schaftlein, assigned to Scott Paper Company, and incorporated herein by reference in its entirety, describes a debonding scheme for maintaining wet strength while reducing product dry strength-a method known to enhance the handfeel of towel products.
The use of bulking fibers can improve the quality of the final end product. U.S. Pat. No. 3,434,918 by Bernardin, U.S. Pat. No. 4,204,504 by Lesas et al., U.S. Pat. No. 4,431,481 by Drach et al., U.S. Pat. No. 3,819,470 by Shaw et al., and U.S. Pat. No. 5,087,324 by Awofeso et al. disclose the use of bulking fibers in papermaking webs to improve product attributes like thickness, absorbency, and softness. These aforementioned patents are incorporated herein by reference in their entirety.
U.S. Pat. No. 5,348,620 by Hermans et al., assigned to Kimberly-Clark Worldwide Inc., and incorporated herein by reference discusses a high consistency/high temperature fiber-treatment-process using a disperser to improve product attributes. To improve tissue softness, several approaches are available to the papermaker such as using certain species of hardwood like eucalyptus in stratified webs as disclosed in U.S. Pat. No. 4,300,981 by Carstens and U.S. Pat. No. 3,994,771 by Morgan et al. The last two patents are incorporated herein by reference in their entirety. These aforementioned patents describe just a few of the many methods developed over the last thirty years to enhance the quality of packaged paper products.
There are also numerous schemes for enhancing the productivity of paper machines. For example, gap formers have been developed to enhance sheet drainage ultimately leading to increased machine speed. New developments in Yankee hood design and Yankee cylinder design have allowed improvements in heat transfer coefficients and mass transfer coefficients, ultimately leading to enhanced machine speeds. New developments in forming fabrics, e.g., multi-layer and triple-layer forming fabrics, have resulted in improved drainage, better fabric life, and enhanced fiber support. These factors translate into enhanced machine speed and productivity. Improvements in press felts, e.g. Scapa's SPECTRA ™ felt concept of using a soft polyurethane sandwich near the base of the felt or the use of stratified batting, have led to improvements in felt life, reductions in break-in time, and improvements in water removal at wet presses. These improved press-felt developments have ultimately translated into improved machine speed and productivity. Improvements in Yankee creping adhesives have been helpful to enhance blade wear and reduce sheet plugging. Continuous creping doctors have alleviated the need to frequently change doctor blades. The last two aforementioned developments have led to improvements in machine speed, reductions in down time, and reductions in paper waste. In spite of all these advances, methods are sought to enhance productivity.
The present invention improves the efficiency of known water removal methods by adding one or more pressing units to the production paper machine, in place of or in conjunction with a suction pressure roll. “Pressing units” according to the present invention include those units that physically engage a belt or pressing blanket, which contacts the impression fabric or felt upon which the web travels. “Foraminous endless fabric” as defined in accordance with the prese
Edwards Steven L.
Marinack Robert J.
McDowell Jeffrey Charles
Worry Gary L.
Finnegan Henderson Farabow Garrett & Dunner
Fort James Corporation
Fortuna Jose
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