Patent issued for process of manufacturing wet formed cellulosic product and a wet formed cellulosic product, combines mechanical and non-mechanical dewatering

Kendall Sinclair

Kendall Sinclair

Dec 20, 2012 – Journal of Engineering

December 20, 2012 () – Armstrong World Industries, Inc.
By a News Reporter-Staff News Editor at Journal of Engineering -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Beaupre, James J. (St. David, ME); Neivandt, David J. (Bangor, ME); Kehrer, Kenneth P. (Lancaster, PA), filed on September 1, 2010, was cleared and issued on December 11, 2012.

The assignee for this patent, patent number 8328987, is Armstrong World Industries, Inc. (Lancaster, PA).

Reporters obtained the following quote from the background information supplied by the inventors: "The manufacture of a cellulosic product such as a sheet of paper from a pulp slurry includes forming portions, pressing portions, and drying portions. Forming the cellulosic product (for example, the sheet of paper) can involve the removal of water by forming section drainage, pressing, and drying. There has been much work conducted in exploring mechanical processes of enhancing removal of water prior to the drying in order to reduce the amount of energy needed for the drying process. As such, there is a need for improvements in the forming section drainage and pressing section drainage that do not require substantial capital investment.

"As paper machines age and speed requirements increase, the machines tend to become limited by the drying portions and/or pressing portions. This limits the rate at which water can be removed. Speed above a predetermined rate produces a sheet with higher than desirable moisture levels.

"Dewatering advancements in the forming portions and pressing portions have generally been mechanical. A higher dryness coming from the forming portions into the pressing portions may lead to a higher dryness exiting the pressing portions and leads to a lower water load entering the drying portions, thus allowing for a savings in energy or an increase in production.

"Pressing portions can be the last chance to increase the dryness of the sheet before entering the drying portions. In pressure controlled pressing portions, the resistance to flow between the fibers of the sheet is insignificant. The dryness of the sheet is dictated by the flow of water exiting the fiber wall. Water in the controlled pressing portions involves a flow phenomenon with the press impulse being the major driving force. Water is removed proportional to the water load of the sheet at a maximum operational pressure. A greater dryness can be achieved by increasing the pressure applied to the sheet, however, above the maximum operational pressure, the structural integrity of the sheet is overcome and the sheet is crushed, creating a lower quality product. Pressure controlled pressing portions apply to single felted presses with basis weights up to 100 g/m.sup.2 and to double felted presses with basis weights up to 150 g/m.sup.2. The pressure controlled pressing portions can be extended to heavier sheets at higher speeds with modern shoe presses.

"Conversely, flow controlled pressing portions are defined by conditions where the rate of water removal is constant at a given set of pressing parameters. This is a sign of poor operational pressing conditions. In the flow controlled pressing portions, water removal follows Darcy's law, as dryness is a function of the press impulse with no independent effect of pressure or time. This condition arises when the water which is being pressed from the sheet is removed at a slower rate than it is created, defeating the purpose of applying a greater pressure. To overcome the limitation, the rate at which water is carried away from the pressing zone is increased in order to achieve a greater dryness out of the press and to revert to the pressure controlled regime.

"In Stratton R. A., Use of polymers in wet pressing, Tappi Proceedings Papermakers Conference, pp. 179-185 (1982), hereinafter 'Stratton,' which is incorporated by reference in its entirety, various cationic wet end polymers were utilized to demonstrate that increases of up to about 1% to 2% solids out of a press section are possible by addition of the polymers to the wet end. Stratton focused solely on the use of the polymers in wet pressing. Increasing the concentration of the polymers resulted in increased solids.

"Busker L. H., Cronin D. C., The relative importance of wet press variables in water removal, Pulp and Pap Can, 85:87-101 (1984), which is incorporated by reference in its entirety, suggested that additives are not apt to be the most productive areas of research and development for large gains in water removal.

"In Wegner T H, The effect of polymeric additive on papermaking, Tappi J 7:107-111 (1987), hereinafter 'Wegner,' which is incorporated by reference in its entirety, the effects of cationic polyacrylamide on water removal in the forming, pressing, and drying sections were discussed. Wegner observed that while an increase in drainage was evident, the sheet behavior during wet-press dewatering was unaffected. It was noted, however, that wet pressing with a cationic polyacrylamide could compensate for higher moisture levels entering the press while maintaining the solids content exiting the press.

"In Springer A, Nabors L A, Bhatia O, The influence of fiber, sheet structural properties, and chemical additives on wet pressing, Tappi J, 4(2):221-228 (1991), hereinafter 'Springer,' which is incorporated by reference in its entirety, chemical additives such as cationic polyacrylamides were shown to have an indirect influence on wet pressing. These chemical additives increased solids exiting the forming section. However, the gains associated with the increased solids were lost during the pressing section. Springer indicated that for sheets entering the press at equal moistures, the additives had no effect on the outgoing solids content. Springer postulated that if an additive was to have any effect on press enhancement, the additive must be able to penetrate the fiber structure and influence its water holding capacity.

"What is needed is a process of forming cellulosic products and cellulosic products, capable of dewatering while not suffering from the above-drawbacks."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "In an exemplary embodiment, a process of making a wet formed cellulosic product including providing a slurry, forming the slurry into a cellulosic product, dewatering the cellulosic product, drying the cellulosic product, and applying an additive to one or more of the slurry and the cellulosic product. A surfactant is in one or more of the slurry and the cellulosic product.

"In another exemplary embodiment, a process of making a wet formed cellulosic product includes providing a slurry having a surfactant and an additive, forming the slurry into a cellulosic product, dewatering the cellulosic product, drying the cellulosic product, and complexing the additive with the surfactant. The surfactant further dewaters the cellulosic product and the complexing of the additive with the surfactant modifies one or more of bulk of the cellulosic product, charge of the cellulosic product, potential of the cellulosic product, cumulative pore volume of the cellulosic product, and surface tension of the cellulosic product.

"In another exemplary embodiment, a wet formed cellulosic product includes a surfactant and an additive, wherein the additive includes one or more of bentonite; polyacrylamide; montmorrilnites; phylosilicates, anionic additives; polyacrylic acid; polystyrene sulfonate; polyerms having an acid selected from the group consisting of sulfonic acid, phosphoric acid, salts of carboxylic acid, salts of phosphoric acid, salts of sulfonic acid, and salts of phosphoric acid; natural polymers; modified natural polymers; synthetic polymers; homopolymers of polyacrylates; homopolymers of polysulfonates; homopolymers of polyphosphates; copolymers of polyacrylates; copolymers of polysulfonates; copolymers of polyphosphates. polyacrylic acid, polymethacrylic acid, polystryrenesulfonic acid, carboxymethylcellulose, guar and xanthan gums; anionic starch; amphoteric starch, copolymers of acrylic acid and acrylamide; silica calcium carbonate; titanium dioxide; and alumina.

"An advantage of an embodiment of the present invention includes the ability to reduce energy consumption in wet form processes due to the non-mechanical dewatering.

"Another advantage of an embodiment of the present invention includes the ability to increase an overall amount of dewatering due to a combination of mechanical and non-mechanical dewatering.

"Another advantage is the ability to manipulate bulk of the cellulosic product formed.

"Another advantage is the ability to manipulate charge and/or potential of the cellulosic product formed.

"Another advantage is the ability to manipulate in surface tension of the cellulosic product formed.

"Another advantage is the ability to manipulate cumulative pore volume of the cellulosic product formed.

"Other advantages will be apparent from the following description of exemplary embodiments of the disclosure."

For more information, see this patent: Beaupre, James J.; Neivandt, David J.; Kehrer, Kenneth P.. Process of Making a Wet Formed Cellulosic Product and a Wet Formed Cellulosic Product. U.S. Patent Number 8328987, filed September 1, 2010, and issued December 11, 2012. Patent URL:

Keywords for this news article include: Chemicals, Chemistry, Phosphoric Acids, Armstrong World Industries Inc..

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