WO2001025535A1 - Procede de nettoyage d'une machine a papier - Google Patents

Procede de nettoyage d'une machine a papier Download PDF

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Publication number
WO2001025535A1
WO2001025535A1 PCT/US2000/026570 US0026570W WO0125535A1 WO 2001025535 A1 WO2001025535 A1 WO 2001025535A1 US 0026570 W US0026570 W US 0026570W WO 0125535 A1 WO0125535 A1 WO 0125535A1
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WIPO (PCT)
Prior art keywords
treatment agent
dryer
paper
paper machine
addition rate
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Application number
PCT/US2000/026570
Other languages
English (en)
Inventor
Thord Hassler
Original Assignee
Hercules Incorporated
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Hercules Incorporated filed Critical Hercules Incorporated
Priority to AU77236/00A priority Critical patent/AU7723600A/en
Publication of WO2001025535A1 publication Critical patent/WO2001025535A1/fr

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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F1/00—Wet end of machines for making continuous webs of paper
    • D21F1/30—Protecting wire-cloths from mechanical damage
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F5/00—Dryer section of machines for making continuous webs of paper
    • D21F5/02—Drying on cylinders
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
    • D21G9/00—Other accessories for paper-making machines
    • D21G9/0009—Paper-making control systems
    • 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
    • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
    • D21H21/02—Agents for preventing deposition on the paper mill equipment, e.g. pitch or slime control

Definitions

  • This invention relates to paper machines generally, and to paper machine runnability and cleanliness in particular. Background
  • Contaminants may originate from the tree itself as extractives that have not been removed during the preparation of the fiber furnish used in the paper making process. Alternatively, the contaminants enter the process through the use of recycled paper. Such paper may contain substances such as glues, lattices, waxes, adhesives and other depositable material added to the paper to improve its properties or make it suitable for its intended use.
  • Deposition can take place in many different locations of the paper making process. Practically any surface may accumulate a deposit, but some surfaces are more prone to deposition than others. Examples of common areas of deposition are: screens in the screen room after the pulp digester, oxygen stage in the bleach section of a pulp mill, machine chest, approach pipe leading the head box. head box, forming wire, press rolls, press felts, drying cylinders and dryer fabrics.
  • Deposition is a complex phenomenon where a multitude of parameters determines the extent of deposition. Attempts have been made to rationalize experience to a cohesive theory. However, effective orgamc deposition control is much more based on empirical expenence than scientific data.
  • de-inking Another method, commonly referred to as de-inking, is based on the principle ot contaminant removal in the preparation of the furnish for the paper production
  • Yet another method is to use a polymer added to a pulp composition before sheet formation for removal of contaminants with the paper. This is particularly preferred when the machine is operated with a high degree of water reuse. Such methods are not always used for retention of contaminants only, but may well also be used for retention of fines, fillers and paper additives such as sizing agents. Many different polymers are used in this regard. Catiomc polymers used include condensation polymers from epichlorohyd ⁇ n and amines (as taught in, e.g , U.S.
  • catiomc starches that are used for overall retention rather than specifically for the retention ot contaminants: catiomc polyacrylamides: modified polyethylene lmine (as taught in. e.g., U.S. Patent No. 3.514.398, the disclosure of which is incorporated by reference in its entirety); water soluble quaternary ammonium polymers (as taught in, e.g.. U.S. Patent No. 3.288,770. the disclosure of which is incorporated by reference in its entirety); and polyvinyl amine polymers (as taught in. e.g., U.S. Patents Nos. 5.098.521 and 4.421,602. the disclosures of which are incorporated by reference in their entireties).
  • Nonionic polymers including, e.g., polyethylene oxide, are also used for paper machine retention of contaminants.
  • patent 5.300.194 the disclosure of which is incorporated by reference in its entirety, is based on separate apphcation of aniornc and catiomc polymers onto certain surfaces in the wet end of a paper machine, e.g., during sheet formation or just after sheet formation.
  • Japanese kokai patent apphcation no. HEI 3 [ 1991 ] - 113089 teaches a surface-soiling prevention method for a paper machine dryer Japanese publication "Merits and achievements of dryer surface modification" (Tomohiro Maezono: Japanese TAPPI, Vol. 52, No.2. 1998, pp. 232-238) describes a method to keep the dryer section of a paper machine free from deposits.
  • Yet another method is based on reduction of the tackiness of the contaminants. Examples of this method can be found in, e.g., U.S. Patents Nos. 5,866,618, 5,723,021 and 4.886,575.
  • Yet another method uses the adsorbing potential of talc and other adsorbents. By this method, the contaminant will not be removed from the system but is instead pacified so that it will not form a deposit.
  • the present invention relates to a method for controlling operation parameters in disparate segments of a paper machine for the purpose of overall regulation of machine operations, including, e.g., runnability and/or cleanliness.
  • the present invention also relates to methods for measuring variables and adjusting parameters which couple operations in disparate segments of a paper machine.
  • the present invention also relates to a method for maintaining cleanliness in a papermaking machine through control of parameters in the wet and dry ends of the machine.
  • the invention relates to elimination or reduction of agglomerates, preferably anionic agglomerates, e.g., pitch and/or stickies, by use of a retention agent in the wet end. coupled with pacifying the retained agglomerates in the dryer to reduce or eliminate runnability problems that agglomerates would otherwise cause in the dryer.
  • the present invention provides a method for improving paper machine operation, the paper machine comprising a wet end and a dryer end, the method comprising: a) determining whether it is desired to improve paper machine operations by dete ⁇ nining whether frequency of paper breaks is acceptable and whether paper appearance is acceptable; b) attributing paper machine operating problems primarily to the wet end, primarily to the dryer end, or to both, by analyzing where in the paper machine deposits are occurring and where paper breaks are caused; and c) improving paper machine operation by: cl) if paper machine problems are primarily attributed to the dryer end, then applying a treatment agent to the dryer; c2) if paper machine problems are primarily attributed to the wet end, or are attributed to both the wet and dryer ends, then applying a treatment agent to the dryer, and introducing or increasing amount of retention agent in the wet end.
  • the method preferably includes: a) first, introducing or increasing amount of retention agent in the wet end; b) second, determining that problems of breaks or paper appearance are att ⁇ butable to the dryer end; and c) third, applying a treatment agent to the dryer
  • parameters are adjusted by performing at least two times at least one of a), b) and c) of the previous paragraph.
  • the amount of retention agent is increased until problems of paper breaks or appearance att ⁇ butable to the dryer end become unacceptable: then applying a treatment agent to the dryer
  • the invention also provides a method for determining paper machine operating parameters, the paper machine comprising a wet end and a dryer end, the method comp ⁇ smg: a) determining an acceptable level of depositable substances m the wet end.
  • a retention agent and retention agent addition rate that obtains about the acceptable level of depositable substances
  • a treatment agent and treatment agent addition rate in the dryer end which treatment agent addition rate is sufficient to reduce deposition of depositable substance in the dryer end
  • the treatment agent and treatment agent addition rate are based on the acceptable level of depositable substances, the retention agent, and retention agent addition rate
  • a method of operating a paper machine comprising employmg a) the retention agent: b) approximately the retention agent addition rate; c) the treatment agent: and d) approximately the treatment agent addition rate; determined by this method.
  • the invention also provides a method for determining paper machine operating parameters, the method comprising: a) determining an acceptable level of depositable substances m the wet end; b) determining a retention agent and retention agent addition rate that obtams about the acceptable level of depositable substances; and c) determining a treatment agent and treatment agent addition rate in the dryer end, which treatment agent addition rate is sufficient to reduce deposition of depositable substance in the dryer end: wherein the retention agent and retention agent addition rate are based on the acceptable level of depositable substances, the treatment agent, and treatment agent addition rate.
  • a method of operating a paper machine comprising employing a) the retention agent; b) approximately the retention agent addition rate; c) the treatment agent; and d) approximately the treatment agent addition rate: determined by this method.
  • the invention also provides a method for determining paper machine operating parameters, the method comprising: a) determining an acceptable level of depositable substances in the wet end: b) dete ⁇ nining a retention agent and retention agent addition rate that obtains about the acceptable level of depositable substances; and c) determining a treatment agent and treatment agent addition rate in the dryer end, which treatment agent addition rate is sufficient to reduce deposition of depositable substances in the dryer end; wherein the acceptable level of depositable substances is based on the retention agent, the retention agent addition rate, the treatment agent, and the treatment agent addition rate.
  • a method of operating a paper machine comprising employing a) the retention agent; b) approximately the retention agent addition rate; c) the treatment agent; and d) approximately the treatment agent addition rate; determined by this method.
  • the present invention also provides a method for operating a paper machine having a wet end and a dryer end, the method comprising: a) preparing a pulp slurry comprising a retention agent; b) separating Whitewater from the pulp slurry to form a sheet; c) drying the sheet in a dryer; and d) applying a treatment agent to the dryer; wherein the paper machine is operated with an average water consumption of less than about 50 1/kg.
  • the acceptable level of depositable substances in the wet end is preferably determined based on experience of mill management to levels below which they expect to experience an acceptable level of difficulties. This determination preferably includes at least one of several factors, including fiber raw material, paper grade, age of machinery, and an opinion of management based on experience.
  • the retention agent preferably comprises at least one of cationic polymer, preferably a synthetic cationic polymer, and cationic starch.
  • the pulp slurry has a solids content and comprises greater than about 0.2 kg cationic starch per ton of paper on a dry basis, or greater than about 0.01 kg synthetic cationic polymer per ton of paper on a dry basis.
  • the dryer comprises a dryer fabric and a drum, and the treatment agent is apphed to at least one of the dryer fabric and drum.
  • the treatment agent preferably comprises at least one of an oil and a synthetic resin powder.
  • a treatment agent comprises an oil
  • the oil preferably comprises a mineral oil, a paraffin wax.
  • a natural or derivatized vegetable oil a natural or derivatized animal oil, or a silicone oil.
  • a treatment agent comprises a natural or derivatized vegetable oil
  • the natural or derivatized vegetable oil preferably comprises a partially hydrogenated animal or vegetable oil. a completely hydrogenated animal or vegetable oil, an animal or vegetable oil transesterified with a polyol, or an acetylated animal or vegetable oil.
  • a treatment agent comprising an oil apphed to a fabric is preferably apphed at a rate of about 0.1 to 100 mg oil per m 2 of fabric surface per minute, more preferably about 0.2 to 40 mg oil per m 2 of fabric surface per minute, more preferably about 0.4 to about 20 mg oil per m 2 of fabric surface per minute, more preferably about 0.5 to 10 mg oil per m : of fabric surface per minute.
  • a treatment agent applied to a dryer drum is preferably apphed at an average rate of about 0.1 to 5000 mg oil per m : of drum surface per minute, more preferably about 5 to 1000 mg oil per m ⁇ of drum surface per minute, more preferably about 30 to 800 mg oil per m 2 of drum surface per minute.
  • the treatment agent comprises an oil
  • the oil is preferably in the form of an oil- in- water emulsion.
  • the synthetic resin powder is preferably in the form of a dispersion in water or other aqueous phase.
  • a treatment agent comprises a surfactant.
  • the surfactant preferably comprises at least one of a nonionic ethoxylated surfactant, an anionic alkyl sulfonate, and a soap.
  • a treatment agent apphed to a dryer drum can comprise a synthetic resin powder, preferably in the form of an aqueous dispersion.
  • Aqueous dispersions of synthetic resin powder preferably comprise a surfactant, the surfactant preferably comprising at least one of a nonionic ethoxylated surfactant, an anionic alkyl sulfonate, and a soap.
  • a treatment agent apphed to a dryer drum comprises a synthetic resin powder
  • the synthetic resin powder is preferably apphed at a rate of about 10 ⁇ g to 50 mg synthetic resin powder per m 2 of drum surface per minute.
  • the synthetic resin powder preferably comprises at least one of melamine cyanurate (preferably comprising melamine cyanurate prepared from about equal weights of melamine and isocyanuric acid) and polytetrafluoroethylene. Apphcation of the synthetic resin powder can be continuous or intermittent.
  • the synthetic resin powder comprises particles having sizes in the range of about 0.1 to 10 ⁇ m, more preferably about 1 to 5 ⁇ m.
  • retention agent is preferably added in sufficient quantity to decrease the turbidity of the Whitewater by at least about 20% compared to operating the paper machine without retention agent, more preferably by at least about 30%, more preferably by at least about 40%.
  • Methods of the present invention are preferably employed in paper machines operated with an average water consumption of less than about 40 1/kg, more preferably less than about 25 1/kg, more preferably less than about 10 1/kg.
  • Figure 1 is a schematic diagram of a method for determining paper machine operating parameters according to the present invention. Detailed Description of Invention
  • weights of paper or other cellulosic product are based on dry weight of the paper or other cellulosic product.
  • a reference to a compound or component includes the compound or component by itself, as well as in combination with other compounds or components, such as mixtures of compounds.
  • Paper machine deposits are generally attributed to either natural or synthetic sources. Natural sources of deposits comprise, or arise from, components naturally present in wood, and can include resins and other compounds. Synthetic sources comprise, or arise from, components intentionally or unintentionally added during production of the paper; during converting paper to an end product; or, in the case of recycled furnish, as a result of use of product later recycled. Synthetic deposits can include insoluble inks, adhesives, etc. Natural sources of deposits are generally referred to as "pitch,” and synthetic sources are generally refe ⁇ ed to as "stickies.” As used herein, the two terms are interchangeable, and use of either term, unless otherwise stated, should be considered as including the other term as well.
  • Both pitch and stickies comprise insoluble, hydrophobic compounds, and tend to agglomerate into particles in aqueous media, such as pulp slurries.
  • the particles may also deposit in machine surfaces, which those of ordinary skill in the art recognize can cause a variety of problems.
  • Particles comprising materials attributable to pitch and/or stickies. therefore, are referred to herein as "depositable substances.”
  • the present invention is directed toward a method for controlling disparate segments of a paper machine in order to improve operational characteristics including, for example, paper machine wet end cleanliness, and deposits on dryer drums and fabrics.
  • the invention includes methods for removal of pitch and/or stickies from a paper machine by use of a retention agent in the wet end of a paper machine in order to bind the pitch/stickies to the paper fibers, and implementation of a dryer deposit control program in the dryer section in order to reduce or eliminate deposition and/or runnability problems which would otherwise be caused by the pitch/stickies in the paper.
  • the invention includes use of a retention agent capable of reducing water turbidity in the wet end of a paper making machine, combined with use of a deposits inhibitor in the dryer end of a paper machine.
  • Methods according to the present invention are especially suited for use in paper machines having high degrees of system closure, which translates to low rates of water consumption.
  • water consumption in methods according to the present invention will be less than about 50 hters of water per kilogram of paper produced (50 1/kg), more preferably less than about 40 1/kg, more preferably less than about 25 1/kg, even more preferably less than about 10 1/kg. Because of water losses due to evaporation in dryer sections, it is impractical to approach 0 1/kg water consumption, and water consumption is generally greater than about 2 or 4 1/kg.
  • Any method for determining residual quantities of contaminants in paper making process waters can be used. Such methods include, for example, turbidimetric methods: TOC (total organic carbon); COD (chemical oxygen demand); and microscopic methods, such as hemocytometric methods; for counting colloidal particles. Turbidimetric methods are preferred, but the methods tend to co ⁇ elate for a given paper machine with a given furnish composition. For the best results, the white water is preferably filtered through coarse filter paper to remove large particles such as fibers. When a turbidimetric method is used for determining quantities of contaminants in paper making process waters, e.g., pitch and/or stickies, any reduction in turbidity is beneficial.
  • TOC total organic carbon
  • COD chemical oxygen demand
  • microscopic methods such as hemocytometric methods
  • Reduction in turbidity can be gauged by measuring turbidity of Whitewater when retention agent is used, and comparing that turbidity to the turbidity of Whitewater obtained in substantially the same way, but without the addition of any retention agent. It is prefe ⁇ ed that use of a retention aid will lower the turbidity of Whitewater by at least about 20% compared to when no retention agent is used, preferably by at least about 30%, more preferably by at least about 40%. Ideally, one would like to reduce the turbidity by about 100%. but in practice it will seldom be economically feasible to do so. It is preferable, therefore, that turbidity be reduced by less than about 100%, more preferably less than about 95%, more preferably less than about 90%, more preferably less than about 85%.
  • any substance that is capable of reducing turbidity in paper machine Whitewater can be used in the present invention.
  • Such substances preferably comprise a polymer, more preferably a catiomc polymer. Mixtures of such substances may also be used.
  • Prefe ⁇ ed cationic polymers include those disclosed in U.S. Patent No. 5,300,194, the disclosure of which is incorporated herein in its entirety.
  • Such cationic polymers include, e.g., polyethyleneimines; protonated or quaternary ammonium polymers; dicyandiamide-formaldehyde condensates; polymers of diallyldimethylammonium chloride; copolymers of diallyldimethylammonium chloride.
  • an acrylic acid derivative such as an acrylamide
  • polybutadienes reacted with lower alkyl amines and partially quaternized, cationic starch, lignin, and tannin derivatives, Manniched tannins, cross-linked polyamines: and mixtures thereof.
  • nonionic retention systems can be used if these reduce turbidity.
  • Example of such systems include polyethylene oxide, and the combination of polyethylene oxide with phenolic resin marketed by the company Kemira under the trade name Netbond.
  • anionic polymers such as anionic polyacrylamide can be used.
  • the reduction in turbidity should be as high as possible, because this will reduce the quantity of residual contaminants in the process water. Apphcation of polymer that does not reduce turbidity is not useful.
  • the amount of synthetic polymer used can be determined by a person of ordinary skill in the art for each particular apphcation. Typically, synthetic polymers will be added at an addition rate below about 1 kg polymer per ton paper (dry basis), more preterably less than about 400g per ton. more preferably less than about 250g per ton If too httle polymer is used, however, then there will be insufficient reduction in turbidity Generally, the polymer addition rate will be greater than about 10 g per ton. more preterably greater than lOOg per ton
  • Naturally denved polymers such as catiomc starches and guar gum. generally require a higher addition rate
  • the amount of naturally derived polymer used can be determined by a person of ordinary skill in the art for each particular apphcation Typically, naturally denved polymers are added at a rate greater than about 1 kg/ton, preferably greater than about 5kg/ton The addition rates will generally be less than about 20 kg/ton. more preferably less than about 10 kg/ton
  • Methods accordmg to the present invention employ dryer pacification of depositable substances While any method of dryer pacification can be used, it is prefe ⁇ ed to use the methods disclosed in Japanese Patent Apphcations Nos 10/288934, 10/288942 and 10/288945, and methods disclosed in U S Patent No 5,246,548, the disclosures of which are incorporated by reference m their entireties These methods are directed toward spraying of a treatment agent on the dryer of a paper machine
  • a dryer fabnc is preferably sprayed with a treatment agent comp ⁇ smg an oil
  • a dryer drum is preferably sprayed with a treatment agent comp ⁇ smg an oil, a synthetic resm powder, or a combination thereof
  • a treatment agent is sprayed onto a dryer fabnc and a second treatment agent, optionally the same as the first treatment agent, is sprayed onto
  • treatment agent When treatment agent is apphed to the dryer, the heat of the dryer generally evaporates most or all of water or other volatiles that may be present, and the remainder of the treatment agent forms a film on a dryer surface, preferably a dryer fabnc and/or dryer drum As paper goes through the dryer, that is, as paper is dned, some of the treatment agent is removed with the paper, which eventually depletes the amount of treatment agent on a dryer surface Treatment agent should be replenished, therefore, preferably at a rate approximately equal to the rate of treatment agent depletion
  • treatment agent is preferably apphed to the dryer, preferably by spraying, either continuously or intermittently Intermittent apphcation can be at regular or irregular intervals
  • Intermittent is meant, e.g , applying for 15 minutes every 30 or 60 minutes, spraying for 10 minutes every hour, or spraying for several minutes whenever it is determined that treatment levels have sufficiently declined
  • An approp ⁇ ate treatment agent and an appropriate treatment agent addition rate can be determmed by one of ordinary skill in
  • Different chemical treatments can be used to reduce deposition in a dryer section
  • Such chemical treatments can be apphed in the form of a solution, m a solvent, as a dispersion, or as neat mate ⁇ al, and can be classified as oils, synthetic resm powders, and mixtures thereof.
  • Several factors should be considered when selectmg which treatment agent to use One factor is the release performance of the treatment agent, ⁇ .e., how well the treatment agent prevents deposition on the dryer surface
  • film stability ⁇ .e., how well the treatment agent maintains as a film under the dryer conditions, especially dryer temperature
  • Another factor is chemical stability, ⁇ .e.. how chemically stable the treatment agent is.
  • the treatment agent should not be adhesive enough to pick up fibers from the wet sheet at dryer surface temperatures
  • the final factor is impact on the sheet. 1 e , the treatment agent should not have an adverse effect on sheet properties at the apphcation rate, especially on sizing and color
  • the person of ordinary skill in the art is able to balance these factors using ordinary experimentation to determine a suitable treatment agent for the particular paper grade being produced.
  • Prefe ⁇ ed oils include sihcones and triglycerides.
  • Prefe ⁇ ed sihcone oils include dialkylsilicones. alkylaryl sihcones, and amino sihcones. Examples of these include, but are not limited to, methylphenyl sihcone oil, dimethyl sihcone oil, amino sihcone oil, epoxy sihcone oil. denatured higher fatty acid sihcone oil.
  • Triglycerides or other oily materials e.g., natural or hydrogenated vegetable or animal oil, e.g., castor oil, can also be used.
  • mineral oils and paraffin waxes are also be used.
  • oil should be understood to mean that the active ingredient is a hquid at temperatures of use, e.g., at the temperature of the surface in the dryer section to which treatment agent is apphed.
  • synthetic resin powder should be understood to refer to a material which is solid at those temperatures.
  • a paraffin wax having a melting temperature of about 60 °C would be considered an oil rather than a solid.
  • Examples of commercial treatment agents include a variety of treatment agents from Maintech, Co. Ltd., (Tokyo, Japan) for example.
  • Dusclean calendar Nos. 1 and 2 Dusclean fine paper No. 1, Duslean news print Nos. 1, 2. and 3, Cleankeeper C, Cleankeeper E, Cleankeeper S, and Cleankeeper LF treatment agents.
  • Hercules Incorporated (Wilmington. Delaware, USA) has Zenix DS 7148, Zenix DS 7141, Zenix DS 7149 and Zenix DS 7151 treatment agents.
  • the treatment agent can be apphed in any manner determined by one of ordinary skill in the art, and is preferably apphed by spraying the treatment agent on to the dryer surface to be treated.
  • An oil e.g., a sihcone oil
  • a treatment agent comprising an oil is preferably apphed with the oil in the form of an emulsion as this lowers viscosity of the treatment agent, and improves dispersion characteristics during spraying.
  • the oil is preferably emulsified with surfactant, by methods determined by those of ordinary skill in the art.
  • an additional surfactant can be used. Any amount of surfactant, or mixture of surfactants, that permits formation of an emulsion by a method determined by one of ordinary skill in the art may be used.
  • Prefe ⁇ ed surfactants include anionic and nonionic surfactants.
  • a nonionic surfactant comprises ethoxylated surfactants, preferably including at least one of ethoxylated glycerides, ethoxylated fatty acids, or other ethoxylated polyols, such as polysorbate 80.
  • the anionicity preferably arises from either a carboxylic acid functionality or a sulfonate functionality.
  • Prefe ⁇ ed anionic surfactants include soaps, e.g., sodium or potassium salts of C 10 -C 22 fatty acids, and alkyl sulfonates, e.g., C ⁇ 0 -C 22 alkyl sulfonates.
  • the surfactant used for emulsification of oil is preferably present at about 15 to
  • Emulsions of oil in water can be prepared in any concentration determined useful by one of ordinary skill in the art. Emulsions preferably have weight ratios of water to oil in the range of about 4 to 15.
  • an excessive supply rate of oil in a treatment agent can result in clogging of the eyes of dryer fabric, thereby deteriorating drying efficiency; can result in dripping or pooling on drums, leading to waste of material; and can possibly result in excessive pick-up of treatment agent on paper, causing change or variation in paper quality.
  • An oil treatment rate can vary depending on, e.g., the type of the dryer fabric and/or dryer drum, and quality of the paper strip, and can be determined by one of ordinary skill in the art. Whenever a treatment rate is for non-constant or non-continuous treatment, then the treatment rate should be understood as referring to average treatment rate.
  • the treatment rate for a dryer fabric can be determined by one of ordinary skill in the art, and can depend on the surface area of the fabric, the material from which the fabric is made, and other factors.
  • the oil in a treatment agent apphed to a dryer fabric is preferably apphed at a rate greater than about 0.1 mg/m 2 /min, more preferably greater than about 0.2 mg/m 2 /min. more preferably greater than about 0.4 mg/m 2 /min, more preferably greater than about 0.5 mg/m 2 /min, and more preferably greater than about 1 mg/m 2 /min, where "m 2 " refers to the area of fabric, i.e., for a simple closed loop of fabric, the area is simply length times width.
  • the oil in a treatment agent is apphed to a dryer fabric at a rate less than about 100 mg m 2 /min, preferably less than about 50 mg/m 2 /min, more preferably less than about 40 mg/m 2 /min, more preferably less than about 25 mg/m7min, more preferably less than about 20 mg/m 2 /min. and more preferably less than about 10 mg/m 2 /min.
  • the oil in a treatment agent apphed to a dryer drum is preferably apphed at a rate greater than about 0.1 mg/m 2 /min, preferably greater than about 0.5 mg/m 2 /min, more preferably greater than about 1 mg/m 2 /min, more preferably greater than about 2 mg m 2 /min. more preferably greater than about 5 mg m 2 /min, more preferably greater than about 10 mg m 2 /min, more preferably greater than about 30 mg/m 2 /min, where "m 2 " refers to the surface area, square meters, of dryer drum, i.e., ⁇ (drum length) (drum diameter).
  • the oil in a treatment agent is apphed to a dryer fabric at a rate less than about 5000 mg/m 2 /min, preferably less than about 1000 mg/m 2 /min, preferably less than about 800 mg/m 2 /min, more preferably less than about 500 mg/m 2 /min, more preferably less than about 300 mg/m 2 /min, more preferably less than about 200 mg/m 2 /min.
  • the treatment agent can be diluted with water to any concentration of actives (non-aqueous components) determined by a person of ordinary skill in the art to be used in a particular paper machine, and can depend on the nature of the pulp, other additives used, etc.
  • the treatment agent sprayed onto the dryer has greater than about 0.033 wt% actives, more preferably greater than about 1 wt% actives, and more preferably greater than about 5 wt% actives.
  • the treatment agent sprayed onto the dryer has less than about 60 wt% active, more preferably less than about 40 wt% actives, more preferably less than about 30 wt% actives.
  • a treatment agent apphed to a dryer drum may contain a synthetic resin powder in addition to, or in place of, an oil. Any synthetic resin powder of appropriate size and type to reduce the effects of asperities in a dryer drum can be used. Since the surface of a drum dryer can be heated up to a high temperature (typically in the range of about 50 to 135 °C), however, use of synthetic resin powders stable at dryer temperatures, e.g., not susceptible to denaturation at dryer temperatures, is preferable. Some preferred synthetic resins for use in treatment agents include, for example, melamine cyanurate (MCA); polytetrafluoroethyelene; and combinations thereof.
  • MCA melamine cyanurate
  • a treatment agent comp ⁇ smg a synthetic resm preferably comprises a melamine cyanurate (MCA), which preferably compnses MCA prepared by reactmg about equal weights ot melamine and isocyanu ⁇ c acid.
  • particle size is an important consideration in selectmg a synthetic resm powder Any particle size distnbution that is capable of efficiently filling up aspenties in a dryer roll may be used in methods of the present invention, and can be determined by one of ordmary skill m the art for the particular equipment used. If the particle size is too small, the fill-up condition becomes unstable, and if the particle size is too large, it becomes difficult to fill up the recesses in the microscopic aspe ⁇ ties on the surface of the drum dryer.
  • synthetic resm powders will generally have average particle sizes greater than about 0.1 ⁇ m, more preferably greater than about 1 ⁇ m. Generally, the synthetic resm powders will have average particle sizes less than about 10 ⁇ m. more preferably less than about 5 ⁇ m.
  • An apphcation rate of synthetic resm powder may be determmed by a person of ordmary skill m the art to dehver a sufficient amount of powder to the drum surface, and may depend on a number of factors, mclud g, for example, on the average particle size m the resm powder, on the mate ⁇ al and condition of the drum to which the treatment is apphed. and the method of apphcation. It is preferable to spray a treatment agent compnsmg a synthetic resm powder on the surface of the dryer, preferably at a low rate of apphcation.
  • the rate of apphcation is greater than about 2 ⁇ g/m 2 /m ⁇ n, more preferably greater than about 10 ⁇ g/m 2 /m ⁇ n, more preferably greater than about 30 ⁇ g/m m ⁇ n based on the weight of the resm powder and the drum surface area
  • the rate of apphcation is preferably less than about 50 mg/mVrnin, more preferably less than about 10 mg/m 2 /m ⁇ n.
  • the treatment agent comp ⁇ smg a synthetic resm powder also comprise a surfactant to improve the quahty of the dispersion, so that spraying as desc ⁇ bed heremafter can be facihtated.
  • a surfactant that improves the dispersion can be used.
  • surfactants mclude anionic and nonionic surfactants.
  • a nonionic surfactant comprises ethoxylated surfactants, preferably including at least one of ethoxylated glycerides. ethoxylated fatty acids, or other ethoxylated polyols, such as polysorbate 80.
  • a surfactant comprises an anionic surfactant
  • the anionicity preferably arises from either a carboxylic acid functionality or a sulfonate functionality.
  • Prefe ⁇ ed anionic surfactants include soaps, e.g., sodium or potassium salts of fatty acids, and alkyl sulfonates, e.g., C ⁇ o-C 22 alkyl sulfonates.
  • surfactant preferably represents about 15 to 60 wt% based on the total of surfactant and synthetic resin powder.
  • a treatment agent comprising a dispersion of synthetic resin powder generally contains about 5 to 100 times as much water (by weight) as much as the synthetic resin powder or sum of synthetic resin powder and surfactant.
  • a treatment agent comprises an oil, a synthetic resin powder, or both
  • water used for dilution and/or apphcation can be heated, e.g., to a temperature in the range of 50 to 80 °C, to reduce the risk of the nozzles getting clogged, e.g., with scum and slime.
  • the surface treatment agent is preferably also heated to a substantially equivalent temperature.
  • a spray nozzle or spray nozzles are preferably employed.
  • the treatment agent may be further diluted with water (on the order of 10- to 100- fold) before the treatment agent is apphed to a dryer surface.
  • Treatment agents for use in the present invention may also contain other additives as deemed necessary by one of ordinary skill in the art to control or modify the treatment agent. These may include, for example, preservatives, antistatic agents, viscosity modifiers, and mixtures thereof.
  • a treatment agent can comprise ingredients to alter the characteristics of the paper product produced. Depending on the type of paper product being manufactured, such ingredients include, for example, lipid (including oil or solid wax) based dusting inhibitor.
  • a treatment agent can be apphed to a dryer by any means. The method of apphcation is not important as long as the treatment is evenly apphed to the surface which is to be treated, e.g., a dryer drum or dryer fabric. A prefe ⁇ ed method of apphcation is with spray nozzles.
  • Stationary nozzles are generally employed in one of two ways. First, there can be two jets, one situated on each outer edge of the width of the drum or fabric to be treated. Second, there can be a multiplicity of nozzles a ⁇ anged across a width of drum or fabric to be treated. When treatment agent is pumped through the jets, or through the nozzles, the treatment agent is sprayed approximately uniformly across surface to be sprayed, e.g., the width of drum or fabric.
  • one or more nozzles are mounted on tracks which permit the nozzles to traverse the width of the surface to be sprayed, thereby covering the entire width of the surface to be sprayed.
  • any spraying apparatus can be used.
  • Prefe ⁇ ed spraying apparatuses are manufactured by Maintech Co. Ltd, Tokyo, Japan under the trade names MISTRUNNER, CLEAN HIT and SPRAY BAR.
  • MISTRUNNER comprises a single traversing spray nozzle.
  • CLEAN HIT comprises two types of stationary nozzles: a needle nozzle to spray the center part of the fabric or drum, and fan nozzles to spray from each end.
  • SPRAY BAR comprises a plurality of stationary nozzles. Each of these apparatuses can be obtained with heating and mixing units for the treatment agent.
  • a treatment agent When a treatment agent is apphed to a dryer fabric, it is apphed either directly, e.g., by spraying the fabric, or indirectly, e.g., by applying the treatment agent to a roll that contacts the fabric. It is prefe ⁇ ed to apply treatment agent to a fabric either by a single traversing nozzle, or with two jet nozzles.
  • treatment agent apphed to a fabric is preferably apphed to the fabric at a location distant from where the fabric contacts the paper, such as at the stretch roll. It is also preferable to apply a treatment agent to the side of the fabric that comes in contact with the paper, or to a roll that contacts the side of the fabric that contacts the paper.
  • the treatment agent is preferably apphed directly to the drum with a single traversing nozzle. Evaporation is less of a consideration when spraying a drying drum than when treating a fabric because the high heat of the drying drum results in rapid evaporation of water that may be present in the treatment agent.
  • strategies and parameters for operation of a paper machine can be determined by following the methodology that is schematically represented in Figure 1.
  • the methodology that is schematically represented in Figure 1.
  • the first step is an analysis relating to paper appearance and break frequency.
  • ""Break frequency” refers to how often there is a break in the paper, which entails machine downtime and lost productivity.
  • Paper appearance refers to spots, discolorations, holes, or other imperfections that can arise in paper.
  • the first step, determining whether break frequency and paper appearance are acceptable, is highly subjective, and depends on a multitude of factors, including paper grade produced, machine speed, and even subjective opinions of decision makers. For example, in some mills, experiencing three or four breaks per month might be considered excessive, whereas in another mill, possibly using different equipment and/or producing different paper grades, breaks even more often than three per day might be considered acceptable.
  • the first step it is determined that breaks and appearance are acceptable, or that there is no interest in improving either of these, then there is no need to implement changes in operating parameters. If. instead, the result of this analysis is that either the break frequency or the paper appearance is unacceptable, or that there is an interest in improving either of these, then the second step is taken.
  • the cause of paper breaks and the locations of paper machine deposits is analyzed.
  • Deposits can be formed in the wet end of the paper machine as well as in the dry end. and their locations can be determined visually, such as by inspecting the machine parts, as well as indirectly, such as by analyzing consequences of the deposits. A person of ordinary skill in the art is able to undertake the necessary analysis to determine the location of deposits in a paper machine.
  • Deposits formed on dryer fabric generally can have two relevant consequences. First, the deposits may leave marks as imprints on the paper. Second, deposits on the dryer fabric may also impair moisture removal leading to wet streaks in the final paper. When either of these two consequences of deposits has developed to an unacceptable level, the machine will have to be closed down and the fabric will have to be cleaned or replaced.
  • Deposits on dryer drums can result in fiber removal from the sheet as a result of adhesion to the roll caused by adhesive contaminant substances. These fibers can accumulate in the dryer section and may form bundles of fibers that may cause a break on the machine. Deposits on the dryer drum are typically removed with a doctor blade, which can damage a dryer drum, reducing its useful lifetime.
  • Deposits may form in the wet end of a paper machine with a high degree of water closure due to accumulation of contaminants caused by reusing the water enclosed in paper making apphcations. These deposits may be located on a variety of different surfaces. Common areas of deposition are usually areas of high shear. These include the approach pipe to the headbox, the headbox, the forming wire, and foils. These deposits may break loose to be incorporated in the paper, creating a spot or a hole, potentially causing a break on the paper machine. Wet end deposits, in addition to visual examination, can also be determined indirectly. For example, deposits on the forming fabric can alter the flow of water through the fabric, leading to a non-uniform fiber distribution in that area. This non-uniformity leads to an imperfection in the sheet, which may cause a break in paper production.
  • deposits can form on the dryer fabric and not on a drying drum, on a drying drum and not on a drying fabric, or on both a drying drum and a drying fabric. Further, on a dryer comprising more than one dryer drum, dryer drum deposits can occur on a dryer drum contacting only one side of the paper sheet, or on dryer drums contacting both sides of the paper sheet. Further, where deposits form on dryer drums contacting both sides of the paper sheet, the deposits need not be equally distributed among drums. Thus, when implementing a dryer deposits control program, only those dryer surfaces in need of deposition control need to be treated.
  • the deposition problem is generally more severe in the first drum, and lessens in severity with each succeeding drum.
  • the first drum should be treated with a dryer deposits control treatment, and the treatment is carried to later drums.
  • a deposits control program can be implemented down the line to treat additional drums if deposits problems continue.
  • the desired course of action is the introduction of a retention agent to retain the contaminants with the sheet. If a retention agent is already used, then the retention agent can be increased, or an additional retention agent employed. The retention agent should be added or supplemented to the point where the imperfections caused by deposits in the wet end are acceptable, and the break frequency caused by these deposits is also acceptable. This increased removal may lead to increased deposition in the dryer section. In the event that this deposition and its consequences are considered unacceptable, in accordance with this invention, then a deposit control agent in the dryer section is introduced.
  • the inventive methodologies can be apphed either retrospectively or prospectively.
  • retrospective apphcation is meant that parameters are analyzed retrospectively, e.g., based on past paper machine performance, such as based on paper breaks and/or deposits locations, such as described above.
  • prospective apphcation is meant that the parameters are based on operating changes that a paper machine operator would like to implement, such as, for example, increasing machine speed, increasing water closure, or using cheaper fiber furnish. For instance, suppose a production manager was required to increase water closure by lowering consumption from 50 1/kg to 30 1/kg. In the first step of the inventive method, the manager would recognize that breaks might increase in frequency, or that paper appearance would suffer. Thus, based on the equipment used and paper produced, the manager would determine likely areas of deposits problems and paper breaks. Based on the results of the analysis, the manager could decrease water consumption, and simultaneously implement retention agents and a dryer deposition control program according to the present invention.
  • methods of the present invention are directed toward determining paper machine operating parameters, of which three sets of parameters are involved.
  • Each set of parameters can be determined by one of ordinary skill in the art using the methods disclosed herein.
  • the first set of parameters is an acceptable level of visible imperfections caused by depositable substances.
  • This parameter relates to the final paper product produced in the machine, and does not specifically relate to a particular segment of the paper machine.
  • This set of parameters can be determined, for example, based on the type of paper product being produced.
  • a paper product destined to be used as corrugated medium in cardboard boxes, for example, can have a higher level of depositable substances than a paper product destined to be used in fine stationery.
  • the second set of parameters is the retention agent and retention agent addition rate in the wet end of the paper machine.
  • the parameters can be based, for example, on the degree of turbidity reduction desired in the Whitewater, the degree of cleanliness required in a paper machine.
  • the third set of parameters is the treatment agent or agents, and addition level or levels thereof, in the dryer section of the paper machine. This set of parameters can be determined by the level of depositable substances expected or found to be present in the dryer section.
  • the present invention ties together the above three sets of parameters. Any two sets of the three sets of parameters can be independently determined by a person of ordinary skill in the art, and used as the basis for determining the unknown set of parameters. It is also possible to combine the treatment program of this invention with other programs to reduce deposit formation. By way of example, it would still be advisable to use deairator in the washing of the pulp to reduce the level of contaminants. It would also be possible to use talk as adsorbent in the preparation of the pulp. To complement the program on the paper machine it may be desirable to use products that prevent deposition on specific surfaces such as press roll by apphcation of a treatment program directly onto this surface.
  • the mill first evaluates a cationic polymer derived from dimethyl amine and epichlorohydrin added to the furnish at an addition rate of 1 lb. per ton paper to eliminate this problem.
  • This method indeed reduces the concentration of contaminants in the wet end and prevents deposition in the head box. but causes increased deposits on the drying cylinders and on the dryer fabric. The apphcation is for this reason terminated, as the deposits in the drying section are considered a more serious problem than the deposits formed in the head box.
  • the mill then proceeds to use the combined method of apphcation according to this invention of the same cationic polymer added to the furnish at the addition rate of 1 lb. per ton paper combined with the apphcation of treatment agent apphed to the drying cylinders.
  • the treatment agent used is a sihcone oil administered as an oil-in-water emulsion directly onto the first and second dryer rolls by a single traversing nozzle at an addition rate of active ingredients of 1 ml/m 2 /min.
  • This combined process eliminates not only the deposits in the head box but also the deposits on the drying cylinders. The overall machine cleanliness is improved.
  • Example 2 A mill producing newsprint paper from a mixture of thermo mechanical pulp and deinked newsprint has a problem with deposits in the forming section, press section and drying section. It is using a modified polyethylene imine cationic polymer (1.5 lb/ton of the trade product Polymin SK from BASF) m the forming section for the retention of fines and colloidal contaminant matenal Applying this program the mill expenences mcreased deposition m the press section and m the drying section resulting in breaks in the paper production A program apphed m the drying section to eliminate deposits on the press felts and press rolls prevents deposition onto these two surfaces, but the mcreased deposition m the drying section still prevails
  • the mill then implements a treatment agent apphcation program in the dryer section, applying a sihcone oil in the form of an emulsion at a rate of active mgredients of 1 ml/m 2 /m ⁇ n to the dryer fabnc, and a sihcone oil in the form of an emulsion at a rate of active mgredients of 1 ml/m 2 /m ⁇ n to the first and seventh dryer drum
  • a treatment agent apphcation program in the dryer section, applying a sihcone oil in the form of an emulsion at a rate of active mgredients of 1 ml/m 2 /m ⁇ n to the dryer fabnc, and a sihcone oil in the form of an emulsion at a rate of active mgredients of 1 ml/m 2 /m ⁇ n to the first and seventh dryer drum
  • the mill is able to increase the use of the catiomc polymer m the forming section to 2 lb/ton for an overall improved machine cleanness.
  • Example 3 A producer of corrugated medium usmg 80% old corrugated containers (OCC) and 20% mixed office waste as furnish is forced to reduce water consumption from 14 1/ton to 8 1/ton In consequence of this closure, the concentration of colloidal contammants in the white water mcreases 100% To cope with the much mcreased concentration of colloidal mate ⁇ al m the back water the mill mcreases the addition rate of cationic polyacrylamide retention agent from 200 g/ton to 300 g/ton. This results in heavy deposition on the dryer fabncs of pitch and stickies from the recycled paper. The mill then begins applying a dryer deposition program to the fabric comp ⁇ smg essentially the method used in Example 1 of U.S patent 5,246,548.
  • a paper mill is operating at a water consumption level of 40 1/kg to produce paper of acceptable quality for its clients. The mill experiences about 1 paper break per week, which the process manager considers acceptable. The mill is then required to reduce its water consumption to 30 1/kg. Upon imposing water closure to meet the new requirement, the mill experiences an increase in paper breaks to about three paper breaks per week. The chents also begin to complain about spots in the paper received.
  • the mill apphes a treatment agent comprising an emulsion of mineral oil to the second dryer drum using a single traversing nozzle spraying at a rate of 2 mJ/m 2 /min, and apphes the spray continuously.
  • a treatment agent comprising an emulsion of mineral oil
  • the mill apphes the spray continuously.
  • Example 5 A new process manager in the mill of Example 4 decides to increase the cleanliness of the paper machine. Without examining the equipment, the manager decides to increase the level of retention agent used in the fiber furnish. The mill had been using 250 g/ton of cationic polyacrylamide with molecular weight about 1.2 xl0° g/mol. The process manager decides to supplement this with 200 g/ton of poly(diallyl dimethyl ammonium chloride), made according to U.S. Patent No. 3,288,770. Based on the manager's experience in other mills, however, the manager concludes that such an addition rate would lead to an unacceptable level of paper breaks in the dryer section. In addition to the dryer treatment agent already being apphed to the second dryer roll (Example 4).
  • the manager decides to apply dryer treatment to the dryer fabric and first dryer drum before increasing the retention agent, in order to prevent dryer section problems.
  • the dryer treatment program is implemented, the retention agent is mcreased, and it is observed that the wet end is now cleaner, with fewer deposits forming in the headbox and foils Additionally, paper breaks are reduced to about one every five weeks

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Abstract

L'invention concerne un procédé permettant d'examiner des paramètres fonctionnels à l'échelle du système dans une machine à papier; ceci afin de procéder à la régulation générale des opérations de la machine, y compris, par exemple, le comportement et/ou la propreté. Ce procédé convient tout particulièrement aux systèmes de fabrication de papier présentant un degré élevé d'obturation de l'eau. Les procédés décrits dans la présente invention comprennent des combinaisons d'un agent de rétention dans la partie humide d'une machine à papier et la passivation du séchoir dans une sécherie d'une machine à papier. L'invention concerne également des procédés permettant de commander des paramètres fonctionnels dans différents segments de la machine à papier; des procédés permettant de mesurer des variables et d'ajuster les paramètres reliant les opérations dans les différents segments d'une machine à papier; et des procédés permettant d'assurer la propreté d'une machine à papier grâce à la commande de paramètres dans la partie humide et dans la partie sèche de la machine.
PCT/US2000/026570 1999-10-05 2000-09-27 Procede de nettoyage d'une machine a papier WO2001025535A1 (fr)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009043971A1 (fr) * 2007-10-01 2009-04-09 Kemira Oyj Procédé de limitation de la formation de dépôts
EP2639350A1 (fr) * 2012-03-16 2013-09-18 Clariant International Ltd. Procédé pour réduire les effets négatifs des contaminants naturels de pas dans des opérations de mise en pâte et de papier

Citations (3)

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Publication number Priority date Publication date Assignee Title
GB2284833A (en) * 1993-11-02 1995-06-21 Steven Frederick Finch Inhibiting the deposition of sticky particles on paper mill dryer fabrics
EP0760406A2 (fr) * 1995-08-24 1997-03-05 Nalco Canada, Inc. Combinaison d'un poly(dadmac/acrylamide)et d'une bentonite pourle control de la poix dans des procédés de fabrication de papier
US5824191A (en) * 1993-08-09 1998-10-20 Fibermark Filter & Technical Products, Inc. Process for making a paper based product employing a polymeric latex binder

Patent Citations (3)

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Publication number Priority date Publication date Assignee Title
US5824191A (en) * 1993-08-09 1998-10-20 Fibermark Filter & Technical Products, Inc. Process for making a paper based product employing a polymeric latex binder
GB2284833A (en) * 1993-11-02 1995-06-21 Steven Frederick Finch Inhibiting the deposition of sticky particles on paper mill dryer fabrics
EP0760406A2 (fr) * 1995-08-24 1997-03-05 Nalco Canada, Inc. Combinaison d'un poly(dadmac/acrylamide)et d'une bentonite pourle control de la poix dans des procédés de fabrication de papier

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009043971A1 (fr) * 2007-10-01 2009-04-09 Kemira Oyj Procédé de limitation de la formation de dépôts
EP2639350A1 (fr) * 2012-03-16 2013-09-18 Clariant International Ltd. Procédé pour réduire les effets négatifs des contaminants naturels de pas dans des opérations de mise en pâte et de papier
WO2013135362A1 (fr) * 2012-03-16 2013-09-19 Clariant International Ltd Procédé pour la réduction des effets négatifs de contaminants à base de poix naturelle dans des opérations à la fois de réduction en pâte et de fabrication de papier

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