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Patent Issued for Methods of Preserving Starch in Pulp and Controlling Calcium Precipitation And/Or Scaling

By a News Reporter-Staff News Editor at Life Science Weekly -- Buckman Laboratories International, Inc. (Memphis, TN) has been issued patent number 8764942, according to news reporting originating

By a News Reporter-Staff News Editor at Life Science Weekly — Buckman Laboratories International, Inc. (Memphis, TN) has been issued patent number 8764942, according to news reporting originating out of Alexandria, Virginia, by NewsRx editors (see also Buckman Laboratories International, Inc.).
The patent’s inventor is Van Haute, Eddie (Ghent, BE).
This patent was filed on June 4, 2013 and was published online on July 1, 2014.
From the background information supplied by the inventors, news correspondents obtained the following quote: “The present invention relates to papermaking and/or the use of recycled paper/paperboard, and also relates to preserving the starch content of pulp during paper and packaging manufacturing, and further relates to controlling calcium precipitation and/or scaling in the treatment of waste water effluents.
“Recycling is a major factor in the modern green economy and is particularly significant in the paper industry’s goal to become more efficient and environmentally sustainable. Use of recycled pulp in paper and packaging manufacturing, however, presents several obstacles to achieving high-quality product. Recycled pulp, for example, derived from old corrugated cardboard, writing/printing grades sized or coated with starch, contain starch, usually at high levels, and are beneficial to making recycled paper/paperboard. The grades of paper/cardboard to be recycled also have beneficial levels of CaCO.sub.3. Unfortunately, this starch content can become substantially degraded during manufacturing as can supplemental starch added during the manufacturing. Less starch in the resulting product means a loss of or lower mechanical properties in the paper/paperboard product made from the pulp. Further, the calcium found in pulp, such as pulp from recycled sources, can cause calcium precipitation, scaling or fouling in the post treatment of process water that occurs after pulp removal.
“More specifically, in the past, numerous papermaking plants (especially those using recycled paper) have experienced numerous problems that may have been related to bacterial problems. However, when the standard approach to combating bacteria was attempted, no success was achieved. Biocides typically used in the papermaking industry and/or typical biocide treatments did not solve the following problems that were being seen in many machines making packaging papers. Those in the industry could not understand what was the exact problem and could not determine a solution to the problem. The present inventor however, determined that a particular microbial activity initiated the following sequence: Microorganisms release amylases into the papermaking system. These extracellular enzymes degrade starch into glucose oligomers (e.g., maltose) and glucose (the starch for instance, comes from waste paper, broke and/or wet end additive starch). The oligomers and monomers are taken up by bacteria and are fermented producing volatile fatty acid (VFAs). VFAs decrease the process pH (from 7 or higher to 6.5-6 or lower). The fermentation process is accompanied by an increase in conductivity and decrease in redox potential. The pH in localized areas around fermenting bacteria can be as low as 1 to 4. Low pH dissolves calcium carbonate filler (for instance as present in waste paper) into soluble calcium Ca.sup.2+ (and CO.sub.2). At this point, the problems only get worse: (1) increased growth of fermenting bacteria results in increased production of extracellular amylases; (2) any starch added for strength in the wet end (between mixing chest and head box) is degraded; (3) the glucose oligomers encourage even more growth of microorganisms and so increase slime and/or other bacteria problems; (4) VFAs are a cause of serious odor problems in the paper as well as in the production environment and/or in the surroundings, potentially including habitation areas; (5) when calcium carbonate is dissolved and stabilized by VFAs, filler (e.g., from waste paper) is lost, essentially a loss of raw material; and/or (6) dissolved calcium can cause deposit or scaling problems.
“In mills utilizing anaerobic digesters for waste water treatment, another related problem can develop, as follows: VFAs react to stabilize dissolved calcium (as VFA-Ca salts) and carry that calcium into the waste water treatment system. With conversion of VFAs into CH.sub.4 and CO.sub.2 and a pH increase in the anaerobic digester, calcium scale forms; if excessive scale is formed this can shut down the waste treatment system, which in turn could cause the shutdown of the mill for cleaning of the anaerobic digester.
“In mills utilizing aerobic digesters or ponds for waste water treatment, alone or in combination with anaerobic digesters, problems with CaCO.sub.3 fall-out can develop, as follows: VFAs react to stabilize dissolved calcium (as VFA-Ca salts) and carry that calcium into the waste water treatment system. With (further) degradation of VFAs in the effluent and with further pH increase during the effluent treatment, calcium carbonate can precipitate resulting in scaling (aerobic reactors) or excessive sludge formation (in aerobic ponds). This can lead to increased downtime for maintenance and cleaning and can cause significant cost for the disposal of CaCO.sub.3-rich sludge as chemical waste.
“The present inventor was the first to understand the root of the problem and how to prevent and/or control this problem. The approach used by the present inventor, as described herein, is to reduce or prevent the breakdown of starch by microbiological activity in the paper mill. The root causes of the problem are in summary: The bacteria and the amylase enzymes produced by the bacteria in the paper machines, because amylase enzymes are very efficient in breaking down starch, for instance, to maltose and glucose. The stimulation of fermentation metabolism of facultative anaerobic bacteria by high glucose and sugar content in the process water resulting in high levels of VFAs being produced which are at the origin of the solubilisation of calcium filler in the process.
“Thus, the present inventor determined that the best way to solve this problem was to get ahead of the problem and stop the terrible chain of events that are detailed above.”
Supplementing the background information on this patent, NewsRx reporters also obtained the inventor’s summary information for this patent: “It is therefore a feature of the present invention to improve strength in paper products (especially ones from recycled pulp or pulp from recycled sources) such as packaging sheets/boards, fluting, liner, test liner, single/multilayer and the like, by preserving the starch content of pulp used to manufacture the same. The treatment of the present invention can be used on Foudrinier and on roundformer machines.
“Another feature of the present invention is to increase the efficiency of wet end additives in paper and packaging manufacturing. This for instance can be achieved through reduction of Ca.sup.2+, pH increase, and/or lower conductivity.
“A further feature of the present invention is to reduce odor-causing materials that can form during paper and packaging manufacturing.
“Yet another feature of the present invention is the reduction of holes and microbiological-related breaks in paper and packaging being formed and in the completed product.
“Another feature of the present invention is the preservation of pre-existing and/or newly added, strength-imparting (native) starch and/or preexisting and/or newly formed starch-cellulose complexes in recycled pulp and/or broke and/or other pulp source material from amylase degradation to allow efficient recovery and transfer of the pre-existing and/or newly added starch and/or preexisting and/or newly formed starch-cellulose complexes into a new sheet manufactured with the recycled pulp or broke.
“Additional features and advantages of the present invention will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention will be realized and attained by means of the elements and combinations particularly pointed out in the description and appended claims.
“To achieve these and other advantages, and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention relates to a method to preserve starch present in pulp and in process waters. The method can be performed as part of a papermaking process. Process water containing pulp can be treated with a chloramine(s). The treatment can be performed in any suitable manner. The treatment can be continuous, substantially continuous, intermittent, cyclic, batch, or any combination thereof. Preferably the treatment maintains an effective amount of chloramine in the process water to achieve one or more benefits mentioned here and generally this effective amount is achieved by maintaining a residual amount of chloramine in the process water over a long continuous period of time. The treatment can be performed at one or more stages or locations in a papermaking system. For example, the treatment can be performed in a vessel such as a head box, and/or at one or more locations upstream and/or downstream of the headbox. A target residual chloramine value or range can be achieved by the treatment. For example, the process water can have a residual chloramine amount of from about 0.3 ppm to about 15 ppm (or chlorine equivalents). The ppm level is expressed as chlorine equivalents as is known and understood by those skilled in the art, and are not as actual chloramine ppm’s in the process water. This residual amount can be determined, for instance, at the headbox, or just prior or just after the headbox (as just one example of a measurement location). The starch can be present in the pulp in a desired amount. For example, the starch can be present in the pulp in an amount of at least about 0.001 wt \% based on the total weight of dried pulp fiber, such as 0.1 wt \% or higher, or 1 wt \% or higher, based on the total weight of dried pulp fiber. The present invention includes the surprising and unexpected discovery that chloramine when used in sufficient quantities and in a substantially continuous or continuous manner, can dramatically preserve starch content, such as, but not limited to cationic starch and/or native starch from size, coatings, sprays, and/or glues, that is present in the pulp, thus leading to packaging and paper products with enhanced properties including strength.
“The present invention relates to a method for microorganism control and starch protection in pulp in a papermaking process or other process which comprises a dual treatment of process water containing pulp with biocide and oxidant. The biocide (e.g., chloramine and/or other biocides) can reduce or eliminate microorganisms capable of producing starch-degrading enzymes, such as amylase (such as .alpha.-amylase) or other starch-degrading enzymes, in the process water. The oxidant (e.g., sodium hypochlorite and/or other oxidants) can provide enzyme control to eliminate residual enzymatic activity of starch-degrading enzymes (such as those produced by microorganisms) or other enzymes. With the indicated dual treatment, enzyme substrates (such as native starches or other enzyme substrates) can be protected from degradation by such enzymes. The dual treatment method can reduce or eliminate counts of bacteria and/or other microorganisms that are starch-degrading enzyme producing and/or other microorganisms, in process water containing the pulp as compared to treatment of the process water containing the pulp without the biocide and oxidant. The dual treatment further can reduce or eliminate starch-degrading enzyme counts in the treated process water as compared to treatment of the process water containing the pulp without the biocide and oxidant.
“The present invention relates to a method to preserve pre-existing and newly added (native) starch and pre-existing and newly formed (native) starch-cellulose complexes present in pulp in a papermaking process comprising treating process water containing pulp comprising complexes or aggregates of cellulose and native starch, wherein the treating comprises separately adding chloramine and oxidant (e.g., sodium hypochlorite) to the process water. The starch-degrading enzyme content (e.g., amylase content) in the treated process water is reduced compared to a similar treatment of the process water without the oxidant. The method can be used to preserve pre-existing as well as newly formed (native) starch and starch-cellulose complexes in recycled pulp, broke, or both used in a papermaking process which comprises the indicated double treatment strategy. An oxidant, e.g., sodium hypochlorite (NaOCl), is used to reduce or eliminate starch-degrading enzyme (e.g., amylase) from a process, such as a papermaking process, and chloramine is separately used from the oxidant in the process to reduce or eliminate microbiological infection and prevent or at least reduce starch-degrading enzyme (e.g., amylase) production in the process from starch-degrading enzyme producing microorganisms. (Native) starch and starch-cellulose complexes in recycled paper or broke are preserved which can contribute to strength in new sheets manufactured with the recycled pulp or broke. Starch-degrading enzyme producing microorganisms, such as amylase-producing bacteria, can produce enzymes that can degrade free starch if present in the process water, and also starch that is complexed with cellulose in aggregates that are introduced into a papermaking process from recycled papers or broke and the like and/or formed in-situ from new starch (native or cationic) added to the process which forms new bonds with fiber. The present invention includes the surprising and unexpected discovery that (native) starch present in recycled pulp or broke that is not mechanically removable (e.g., by processes such as repulping, mixing, refining and other paper processes) is vulnerable to release by starch-degrading action (e.g., amylolytic action), wherein the indicated double treatment strategy can reduce or prevent such starch-degrading action (e.g., amylolytic action) to allow efficient recovery and transfer of the pre-existing (native) starch and starch-cellulose complexes into a new sheet manufactured with the recycled pulp or broke. The indicated double treatment strategy alternatively or additionally can reduce and/or prevent such starch-degrading action on newly added starch (native or cationic), which can be present in the process as free starch and/or in complexed form wherein new bonds are created in-situ between this new starch and fiber in the process. The indicated double treatment strategy can protect, at least partially or fully, such newly added starch and/or newly formed starch-fiber complexes from amylolytic action.
“The methods of the present invention also have the added benefits of controlling the growth of microorganisms, reducing the production of volatile fatty acids (VFAs), preventing conductivity increases, preventing decreases in redox potential, lowering calcium dissolution, increasing pH, and/or minimizing precipitation on and/or scaling of machinery–especially in anaerobic digesters. The methods of the present invention can increase the efficiency of cationic wet end additives, for example, retention polymers, starches, and/or dry strength resins. Improved strength allows for lower strength additive costs, reduction in basis weight, and use of product in higher strength grade markets.
“The methods of the present invention can result in maintaining or increasing filler and/or ash content in the sheet product. For instance, solid calcium that would have been dissolved in conventional systems, is instead retained in the sheet as a raw material. Lower calcium ion concentrations (lower precipitated calcium levels) lead to increased uptake of starch into sheets including binding of starch to filler particles. Reduction in chemistry usage is also realized in multiple contexts including in the paper machine and subsequently in a biological waste water plant. Increased machine output due to reduction in size press starch solids and the option to transition from size press to wet end starch addition are also made possible. Also, with the present invention, a drying energy reduction can be achieved by the elimination of (1 or 2 sides of 2-sided) size press. Reduction in the amount of sludge to be landfilled and reduction in effluent plant polymer treatment are further made possible by the methods of the present invention.
“It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide a further explanation of the present invention, as claimed.
“The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate some of the features of the present invention and together with the description, serve to explain the principles of the present invention.”
For the URL and additional information on this patent, see: Van Haute, Eddie. Methods of Preserving Starch in Pulp and Controlling Calcium Precipitation And/Or Scaling. U.S. Patent Number 8764942, filed June 4, 2013, and published online on July 1, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=\%2Fnetahtml\%2FPTO\%2Fsrchnum.htm&r=1&f=G&l=50&s1=8764942.PN.&OS=PN/8764942RS=PN/8764942
Keywords for this news article include: Bacteria, Chloramines, Sulfonamides, Enzymes and Coenzymes, Buckman Laboratories International Inc..
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