Classifications

• • 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
  • D21H21/06—Paper forming aids
  • D21H21/10—Retention agents or drainage improvers
• • 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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/37—Polymers of unsaturated acids or derivatives thereof, e.g. polyacrylates
  • D21H17/375—Poly(meth)acrylamide
• • 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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/41—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups
  • D21H17/44—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups cationic
  • D21H17/45—Nitrogen-containing groups
  • D21H17/455—Nitrogen-containing groups comprising tertiary amine or being at least partially quaternised
• • 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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/63—Inorganic compounds
  • D21H17/66—Salts, e.g. alums
• • 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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/63—Inorganic compounds
  • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
  • D21H17/68—Water-insoluble compounds, e.g. fillers, pigments siliceous, e.g. clays
• • 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
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
  • D21H23/04—Addition to the pulp; After-treatment of added substances in the pulp
  • D21H23/06—Controlling the addition
  • D21H23/14—Controlling the addition by selecting point of addition or time of contact between components

Definitions

• the present invention relates to papermaking pulps, papermaking processes employing the pulps, papermaking apparatus and paper and paperboard products made from the pulps. More particularly, the present invention relates to treating papermaking pulp with at least one microparticle-containing retention aid system.
• Retention aid systems containing microparticles and other particulate materials have been added to papermaking pulps as process aids to improve retention and other properties such as formation and drainage.
• U.S. Patent No. 5,194,120 to Peats et al. incorporated herein by reference in its entirety, describes a retention aid system comprising a cationic polymer and an amorphous metal silicate material.
• One type of silicate material mentioned by Peats et al. system is Laponite ® , a synthetic layered silicate.
• a retention aid system comprising an amorphous metal silicate material and a cationic polymer provides several advantages, including improved retention, drainage and formation while minimizing the amount of polymer and amorphous metal silicate added to the pulp.
• the microparticle component of the retention aid system is typically added to the papermaking pulp in the form of a low viscosity aqueous colloidal dispersion, i.e. a sol.
• a sol a low viscosity aqueous colloidal dispersion
• One problem with microparticle sols employed in papermaking pulps is instability. Because of the instability of sols used in connection with papermaking pulps, the sols are often made on-site for immediate delivery to a papermaking process.
• the present invention relates to the use of a combination of synthetic layered silicate microparticles, a peptizer and at least one polymer as a retention aid system for a papermaking pulp or stock.
• the synthetic layered silicate is preferably a synthetic hydrous sodium lithium magnesium silicate and is preferably added to the papermaking pulp in the form of an aqueous colloidal dispersion which also contains the peptizer.
• the polymer can be a cationic polymer, a nonionic polymer, or an amphoteric polymer used under cationic conditions.
• the polymer is preferably a synthetic nitrogen-containing cationic polymer, for example, a cationic polyacrylamide. If nonionic, the polymer can be, for example, a nonionic polyacrylamide or a polyethylene oxide.
• the peptizer is present in the microparticle dispersion for the purpose of maintaining the dispersion in the form of a sol and to prevent the dispersion from setting to a gel for a predetermined period of time. This permits the formation of relatively concentrated microparticle sols which can be formed off-site, which exhibit a relatively long shelf life and can be shipped to the papermaking plant for immediate or future use.
• microparticle dispersions which include a peptizer also provide significant improvements over microparticle dispersions which do not employ a peptizer.
• a retention aid including a microparticle dispersion containing synthetic hydrous sodium lithium magnesium silicate and a peptizer significantly improves retention of fines, drainage and formation, thereby providing enhancements in the papermaking process and in the paper product.
• the present invention provides a method of making paper or paperboard comprising: (a) forming a treated pulp by adding to a papermaking pulp a synthetic layered silicate, a peptizer and at least one polymer, the synthetic layered silicate comprising a synthetic hydrous sodium lithium magnesium silicate and the at least one polymer comprising one or more members of the group consisting of cationic polymers, nonionic polymers and amphoteric polymers under cationic conditions; and (b) forming the treated pulp into said paper or paperboard.
• the present invention provides a papermaking apparatus comprising a supply of synthetic layered silicate, a supply of a papermaking pulp, a device for feeding the synthetic layered silicate from the supply of synthetic layered silicate to the supply of papermaking pulp, a supply of a retention system polymer, a device for feeding the retention system polymer from the supply of retention system polymer to the papermaking pulp, and a device for forming the pulp into a paper or paperboard after treatment with the synthetic layered silicate and the retention system polymer, wherein said retention system polymer is a cationic polymer, a nonionic polymer, or an amphoteric polymer under cationic conditions, or combinations thereof and wherein the synthetic layered silicate comprises a synthetic hydrous sodium lithium magnesium silicate and is fed to the papermaking pulp in the form of an aqueous dispersion which also includes an inorganic polyphosphate peptizer.
• the present invention provides a paper or paperboard made from a drained paperweb, the paperweb comprising a treated pulp, the treated pulp comprising cellulosic fibers, synthetic hydrous sodium lithium magnesium silicate, at least one retention system polymer and an inorganic polyphosphate peptizer, said retention system polymer comprising a cationic polymer, a nonionic polymer, or an amphoteric polymer under cationic conditions, or combinations thereof.
• FIG. 1 is a flow chart showing a papermaking process according to an embodiment of the present invention
• FIG. 2 is a flow chart showing a papermaking process according to another embodiment of the present invention.
• FIG. 3 is a flow chart showing a papermaking process according to yet another embodiment of the present invention.
• FIG. 4 is a flow chart showing a papermaking process according to yet another embodiment of the present invention.
• FIG. 5 is a flow chart showing a papermaking process according to yet another embodiment of the present invention.
• FIG. 6 is a bar graph showing the time to achieve drainage of 200 ml of filtrate from paperwebs made of various exemplary and comparative paperstock formulations
• FIG. 7 is a bar graph comparing the turbidity of various exemplary and comparative paperstock formulations;
• FIG. 8 is a bar graph showing the % total first pass retention (TFPR) of various exemplary and comparative paperstock formulations;
• FIG. 9 is a plot of time vs. volume showing the drainage of various exemplary and comparative paperstock formulations
• Figure 10 is a bar graph showing the drainage in seconds of various exemplary and comparative paperstock formulations.
• Figure 11 is a bar graph showing the retention for various exemplary and comparative paperstock compositions.
• the present invention relates to the use of a retention aid system for a papermaking pulp, the system comprising a synthetic layered silicate, a peptizer and at least one polymer. More than one type of microparticle, more than one type of peptizer and more than one type of polymer can be used in the process of the invention.
• Paper and paperboard products made according to the method preferably exhibit excellent opaqueness and/or other desirable physical properties. Sheets of pulp from which the paper and paperboard products are made preferably exhibit excellent drainage and/or excellent retention of pulp fines.
• the synthetic layered silicate preferably comprises a synthetic hydrous sodium lithium magnesium silicate which is manufactured and sold under the trademark Laponite ® by Rockwood Additives Limited of Widnes, Cheshire, United Kingdom. These synthetic hydrous sodium lithium magnesium silicates are synthesized by combining salts of sodium, magnesium and lithium with sodium silicate at carefully controlled rates and temperatures. This produces an amorphous precipitate which is then partially crystallized under high temperature and pressure. The resulting product is filtered, washed, dried and milled to give a fine white powder. [00025] For greater certainty, the terms "synthetic hydrous sodium lithium magnesium silicate” and "hydrous sodium lithium magnesium silicate” as used herein include silicates which are identified by CAS No.
• silicates typically comprise a free flowing white powder having a bulk density of 1 ,000 kg/m 3 ; surface area (BET) of 370 m 2 g; pH (2% suspension) of 9.8; sieve analysis ( ⁇ 250 ⁇ m) of 98%; and moisture content of 10%.
• synthetic hydrous sodium lithium magnesium silicate and "hydrous sodium lithium magnesium silicate” as used herein do not include synthetic layered silicates identified by the TSCA name "hydrous sodium lithium magnesium fluorosilicate” and by CAS No. 64060-48-6 and which have the following typical chemical composition (wt% - dry basis): Si0 2 51.0; MgO 25.0; Li 2 0 1.3; Na 2 0 6.0; P 2 0 5 3.3; F 5.0; loss on ignition 8.4.
• the synthetic layered silicate microparticles can be added in any amount sufficient to improve the retention of fines or drainage or to reduce turbidity when the pulp or stock is formed into a wet sheet or web.
• the microparticles are added in an amount of at least about 0.05 lb/ton (0.02 kg/tonne) of paperstock, based on the dried solids weight of both the microparticles and the paperstock.
• the microparticles are added in an amount of from about 0.1 lb/ton (.05 kg/tonne) of paperstock to about 5.0 lb/ton (2.3 kg/tonne) of paperstock, for example, from about 0.2 lb/ton (0.09 kg/tonne) to about 1.0 lb/ton (0.5 kg/tonne), based on dried solids weight of the paperstock.
• the terms "furnish”, “pulp", “stock”, and “paperstock” are used interchangeably.
• the synthetic layered silicate is added to the pulp in the form of an aqueous, colloidal dispersion of relatively low viscosity.
• a colloidal dispersion having these characteristics is known as a "sol".
• the dispersion preferably also contains a peptizer in an amount sufficient to maintain the dispersion in the form of a sol for a predetermined period of time.
• the peptizer essentially stabilizes the sol to prevent it from setting to a gel for a period of time which depends at least partially on the concentration of the synthetic layered silicate. This permits the dispersion to be formed off-site in a reasonable concentration and then shipped to the paper making plant for immediate or future use.
• the peptizer is preferably a water soluble salt which enhances dispersion of the synthetic layered silicate, more preferably a sodium salt selected from the group comprising sodium carbonate, sodium metaphosphates, sodium polyacrylates, sodium hydroxide, sodium chloride, sodium polyphosphates and sodium pyrophosphates.
• the peptizer is an inorganic polyphosphate, more preferably tetrasodium pyrophosphate.
• the preferred peptizer, tetrasodium pyrophosphate is present in certain grades of hydrous sodium lithium magnesium silicate available from Rockwood Additives Limited, including Laponite RDS, Laponite XLS and Laponite DS.
• Laponite RDS which comprises synthetic hydrous sodium lithium magnesium silicate (CAS No. 53320-86-8) in combination with about 5 wt% tetrasodium pyrophosphate.
• Laponite RDS sols containing about 10wt% concentration of Laponite are stable for about 3 days.
• the sol has a laponite concentration of up to about 6 wt% which is stable for at least about 90 days.
• Sols having a microparticle concentration in this range exhibit sufficiently long shelf to allow them to be formed off-site for shipment and subsequent use in a papermaking process.
• microparticle dispersions which include a peptizer also provide significant improvements over microparticle dispersions which do not employ a peptizer.
• the inventor has found that the inclusion of a peptizer in the microparticle dispersion significantly improves retention of fines, drainage and formation, thereby providing enhancements in the papermaking process and in the paper product.
• Laponite RDS which contains the peptizer tetrasodium pyrophosphate (TSPP)
• TSPP peptizer tetrasodium pyrophosphate
• the polymer is preferably added to the papermaking pulp before addition of the microparticles, though any order of addition can be used.
• the polymer can be any polymer which does not adversely affect the formation of pulp or paper and may preferably comprise a coagulant and/or a flocculant.
• the polymer is a medium to high molecular weight synthetic polymer, for example, a cationic nitrogen-containing polymer such as a cationic polyacrylamide or a copolymer thereof, or a cationic diallyldimethylammonium chloride or a copolymer thereof.
• the polymer can be cationic, nonionic, or amphoteric. If amphoteric, the polymer is preferably used under cationic conditions. At least one other polymer of any kind can be used in addition to the polymers recited above so long as the at least one other polymer does not substantially adversely affect the retention properties of the present invention.
• the at least one other polymer can preferably be a polyamidoamineglycol (PAAG) polymer.
• the polymer preferably has a molecular weight in the range of from about 100,000 to about 25,000,000, and more preferably from about 500,000 to about 18,000,000, though other molecular weights are possible to achieve the intended effect.
• the polymer can preferably be a high molecular weight linear cationic polymer or a crosslinked polyethylene oxide.
• Exemplary high molecular weight linear cationic polymers and shear stage processing suitable for use in the pulps and methods of the present invention are described in U.S. Patent Nos. 4,753,710 and 4,913,775 to Langley et al., both of which are incorporated herein in their entireties by reference.
• the polymer is preferably added before at least one of the significant shear steps of the papermaking process and may be added in more than one step.
• the microparticles can be added before or after the various significant shear steps of the papermaking process.
• the polymer can be added before the microparticles and before at least one significant shear step in the papermaking process. If the polymer is added before the microparticles, the microparticles can be added before or after a final shear step of the papermaking process. Although it is preferable to add the polymer to the papermaking pulp before the last shear point in the papermaking process, the polymer can be added after the last shear point.
• the microparticles preferably form bridges or networks between various particles.
• the polymer is preferably partially attached (e.g., adsorbed) onto the surfaces of particles within the stock and can provide sites of attachment.
• Aqueous cellulosic papermaking pulp or stock can be treated by first adding the polymer to the pulp or stock, followed by subjecting the paper stock to high shear conditions, followed by the addition of the microparticles prior to sheet formation.
• the polymer can be cationic, nonionic, or amphoteric under cationic conditions.
• the polymer can be added simultaneously with the synthetic layered silicate microparticles.
• Preferred cationic polyacrylamides for use as the retention system polymer are described in more detail below. If a cationic polyacrylamide is used as the cationic polymer, the cationic polyacrylamide can have a molecular weight in excess of
• the combination of the polymer and the synthetic layered silicate microparticles preferably provides a suitable balance between freeness, dewatering, fines retention, good paper formation, strength, and resistance to shear.
• the polymer composition of the retention system is added in an amount effective to preferably improve the drainage or retention of the pulp compared to the same pulp but having no polymer present.
• the polymer is preferably added in an amount of at least about 0.01 pound of polymer per ton (0.005 kg/tonne) of paperstock, based on the weight of dried solids of both the polymer and the paperstock.
• the polymer is added in an amount of from about 0.1 lb/ton (0.05 kg/tonne) of paperstock to about 5 lb/ton (2.3 kg/tonne) of paperstock, even more preferably from about 0.2 lb/ton (0.09 kg/tonne) to about 2 lb/ton (1 kg/tonne) based on the dried solids weight of the paperstock, though other amounts can be used.
• any cationic polymer or mixture thereof can be used and preferably conventional cationic polymers commonly associated with papermaking can be used in the pulps or stocks of the present invention.
• cationic polymers include, but are not limited to, cationic starches and cationic polyacrylamide polymers, for example, copolymers of an acrylamide with a cationic monomer, wherein the cationic monomer may be in a neutralized or quaternized form. Nitrogen-containing cationic polymers are preferred.
• Exemplary cationic monomers which may be copolymerized with acrylamide to form preferred cationic polymers useful according to the present invention, include amino alkyl esters of acrylic or methacrylic acid, and diallylamines in either neutralized or quaternized form.
• Exemplary cationic monomers and cationic polyacrylamide polymers are described in U.S. Patent No. 4,894,119 to Baron, Jr., et al., which is incorporated herein in its entirety by reference.
• the polymer may also be a polyacrylamide formed from comonomers that include, for example, 1-trimethylammonium-2-hydroxypropylmethacrylate methosulphate.
• cationic polymers include, but are not limited to, homopolymers of diallylamine monomers, homopolymers of aminoalkylesters of acrylic acids, and polyamines, as described in U.S. Patent No. 4,894,119. Co-polymers, ter- polymers, or higher forms of polymers may also be used. Further, for purposes of the present invention, a mixture of two or more polymers may be used.
• nonionic acrylamide units are preferably present in the copolymer, preferably in an amount of at least about 30 mol % and generally in an amount of no greater than 95 mol %. From about 5 mol % to about 70 mol % of the polymer is preferably formed from a cationic comonomer.
• the papermaking pulp or stock can be any conventional type, and, for instance, can contain cellulose fibers in an aqueous medium at a concentration of preferably at least about 50% by weight of the total dried solids content in the pulp or stock.
• the retention system of the present invention can be added to many different types of papermaking pulp, stock, or combinations of pulps or stocks.
• the pulp may comprise virgin and/or recycled pulp, such as virgin sulfite pulp, broke pulp, a hardwood kraft pulp, a softwood kraft pulp, mixtures of such pulps, and the like.
• the retention aid system can be added to the pulp or stock in advance of depositing the pulp or stock onto a papermaking wire.
• the pulp or stock containing the retention aid system has been found to exhibit good dewatering during formation of the paperweb on the wire.
• the pulp or stock also exhibits a desirable high retention of fiber fines and fillers in the paperweb products under conditions of high shear stress imposed upon the pulp or stock.
• the papermaking pulp or stock according to the present invention may further contain other types of microparticles.
• One or more different types of secondary microparticle additives different from the synthetic layered silicate microparticles, may be added to the pulp at any time during the process.
• the secondary microparticle additive can be a natural or synthetic hectorite, bentonite, zeolite, non-acidic alumina sol, or any conventional particulate additives as are known to those skilled in the art.
• Exemplary synthetic microparticles are described in U.S. Patent Nos. 5,571 ,379 and 5,015,334, which are incorporated herein in their entireties by reference.
• the papermaking pulps or stocks according to the present invention may further contain a coagulant/flocculant retention system having a different composition than the retention system of the present invention.
• the papermaking pulps of the present invention may also contain a conventional papermaking pulp-treating enzyme that has cellulytic activity.
• the enzyme composition also exhibits hemicellulytic activity.
• Suitable enzymes and enzyme-containing compositions include those described in U.S. Patent Nos. 5,356,800 and 6,342,381 to Jaquess, and International Publication No. WO 99/43780, all incorporated herein in their entireties by reference.
• Other exemplary papermaking pulp-treating enzymes are BUZYMETM 2523 and BUZYMETM 2524, both available from Buckman Laboratories International, Inc., Memphis, Tenn.
• a preferred cellulytic enzyme composition preferably contains from about 5% by weight to about 20% by weight enzyme.
• the preferred enzyme composition can further contain polyethylene glycol, hexylene glycol, polyvinylpyrrolidone, tetrahydrofuryl alcohol, glycerine, water, and other conventional enzyme composition additives, as for example, described in U.S. Patent No. 5,356,800.
• the enzyme may be added to the pulp in any conventional amount, such as in an amount of from about 0.001% by weight to about 0.100% by weight enzyme based on the dry weight of the pulp, for example, from about 0.005% by weight to about 0.05% by weight.
• an enzyme composition is included in the pulp or stock and contains at least one polyamide oligomer and at least one enzyme.
• the polyamide is present in an effective amount to stabilize the enzyme.
• Exemplary enzyme compositions containing polyamide oligomers and enzymes are described in International Published Application No. WO 99/43780, which is incorporated herein in its entirety by reference.
• an enzyme composition can include a combination of two or more different enzymes.
• the enzyme composition can include, for example, a combination of a lipase and a cellulase, and optionally can include a stabilizing agent.
• the stabilizing agent may be a polyamide oligomer as described herein.
• Cationic starch may be added to the pulp or stock of the present invention to form a starch treated pulp.
• Starch may be added at one or more points along the flow of papermaking pulp through the papermaking apparatus or system of the present invention.
• cationic starch can be added to a pulp at about the same time that the acidic aqueous alumina sol is added to the pulp.
• a cationic starch is employed, it is added to the pulp or combined with the pulp prior to introducing the synthetic layered silicate microparticles to the pulp.
• the cationic starch can alternatively or additionally be added to the pulp after the pulp is first treated with an enzyme, a coagulant, or both.
• Preferred cationic starches include, but are not limited to, potato starches, corn starches, and other wet-end starches, or combinations thereof.
• starch Conventional amounts of starch can be added to the pulp.
• An exemplary amount of starch that can be used according to the present invention is from about 5 to about 25 pounds per ton based on the dried solids weight of the pulp.
• a biocide may be added to the pulp in accordance with conventional uses of biocides in papermaking processes.
• a biocide may be added to the treated pulp in a blend chest after the pulp has been treated with the optional enzyme and polymer.
• Biocides useful in the papermaking pulps according to the present invention include biocides well known to those skilled in the art, for example, biocides available from Buckman Laboratories International, Inc., Memphis, Tenn., such as BUSANTM biocides.
• the pulps or stocks of the present invention may additionally be treated with one or more other components, including polymers such as anionic and non-ionic polymers, clays, other fillers, dyes, pigments, defoamers, pH adjusting agents such as alum, microbiocides, and other conventional papermaking or processing additives.
• polymers such as anionic and non-ionic polymers, clays, other fillers, dyes, pigments, defoamers, pH adjusting agents such as alum, microbiocides, and other conventional papermaking or processing additives.
• these additives can be added before, during, or after introduction of the synthetic layered silicate microparticles.
• the synthetic layered silicate microparticles are added after most, if not all, other additives and components are added to the pulp.
• the synthetic layered silicate microparticles can be added to the papermaking pulp after the addition of enzymes, coagulants, flocculants, fillers, and other conventional and non-conventional papermaking additives.
• FIG. 1 A flow chart of a papermaking system for carrying out one of the methods of the present invention is set forth in FIG. 1. It is to be understood that the system shown is exemplary of the present invention and is in no way intended to restrict the scope of the invention.
• an optional supply of enzyme composition at a desired concentration is combined with a flowing stream of papermaking pulp to form a treated pulp.
• the supply of pulp shown represents a flow of pulp, as for example, supplied from a pulp holding tank or silo.
• the supply of pulp shown in FIG. 1 can be a conduit, holding tank, or mixing tank, or other container, passageway, or mixing zone for the flow of pulp.
• the supply of enzyme composition can be, for example, a holding tank having an outlet in communication with an inlet of a treated pulp tank.
• the pulp treated with the enzyme composition is passed from the treated pulp tank through a refiner and then through a blend chest where optional additives, for example, a biocide, may be combined with the treated pulp.
• the refiner has an inlet in communication with an outlet of the treated pulp tank, and an outlet in communication with an inlet of the blend chest.
• the pulp treated in the blend chest is passed from an outlet of the blend chest through a communication to an inlet of a machine chest where optional additives may be combined with the treated pulp.
• the blend chest and machine chest can be of any conventional type known to those skilled in the art.
• the machine chest ensures a level head, that is, a constant pressure on the treated pulp or stock throughout the downstream portion of the system, particularly at the head box.
• the pulp is passed to a white water silo and then to a fan pump.
• the retention system polymer of the present invention is preferably introduced into the flow of pulp between the silo and the fan pump.
• the supply of retention system polymer composition can be, for example, a holding tank having an outlet in communication with a line between the white water silo and the fan pump.
• the synthetic layered silicate microparticles are preferably added.
• Conventional valving and pumps used in connection with introducing conventional additives can be used.
• the screened pulp passes to a head box where a wet papersheet is made on a wire and drained. In the system of FIG. 1 , drained pulp resulting from papermaking in the headbox is recirculated to the white water silo.
• the synthetic layered silicate microparticles are added first to the refined treated pulp between the white water silo and the fan pump.
• the retention system polymer is added after the fan pump and before the screen.
• FIG. 3 Another embodiment of the present invention is shown in FIG. 3.
• a pulp optionally treated with a cationic starch is refined, passed to a blend chest, passed to a machine chest, and then passed to a white water silo. Between the white water silo and the fan pump the retention system polymer is preferably added to the pulp.
• the synthetic layered silicate microparticles are preferably added after the pulp passes through the screen and just prior to sheet formation in the head box.
• the apparatus of the present invention can also include metering devices for providing a suitable concentration of the synthetic layered silicate microparticles or other additives to the flow of pulp.
• a cleaner for example, a centrifugal force cleaning device, can be disposed between, for instance, the fan pump and the screen, according to any of the embodiments of FIGS. 1-3 above.
• Figures 4 and 5 are flow charts illustrating the polymer and microparticle addition steps in two particularly preferred embodiments of the present invention. It will be appreciated that Figures 4 and 5 illustrate only those components (i.e. fan pump, screen and headbox) and addition steps which are necessary to describe the polymer and microparticle addition steps in these preferred processes, and that the processes and apparatus illustrated in Figures 4 and 5 may preferably include some or all of the optional additives, apparatus components and/or process steps shown in Figures 1 to 3 and described above.
• the pulp passes through the apparatus of Figures 4 and 5 in the direction indicated by the arrows, passing through the fan pump and the screen on its way to the headbox.
• the pulp is sheared by both the fan pump and the screen, however the shear applied to the pulp by the screen is greater than that applied by the fan pump, so that the screen is the final high shear stage in the papermaking process prior to entry of the pulp into the headbox of the papermaking apparatus.
• a coagulant polymer is preferably added before the fan pump.
• the coagulant preferably comprises a relatively low molecular weight, cationic, high charge density polymer to scavenge and collect colloidal particles, primarily anionic fibers and fillers.
• the colloidal particles are coagulated to form macro-colloids which are larger in size and more easily retained in the sheet upon drainage.
• the coagulant is preferably a polyamine or diallyldimethylammonium chloride (DADMAC) polymer, or copolymers thereof.
• DADMAC diallyldimethylammonium chloride
• a particularly preferred coagulant for use in the processes illustrated in Figures 4 and 5 is BUFLOCTM 5376, available from Buckman Laboratories International, Inc., which is a cationic DADMAC having a 95% charge density and a molecular weight of about 500,000.
• the coagulant polymer is preferably added to the pulp in an amount of from about 0.05 to about 1.0 kg/tonne of pulp on a dry basis, more preferably from about 0.1 to about 0.5 kg/tonne and even more preferably about 0.3 kg/tonne.
• the processes of Figures 4 and 5 both include the addition of a microparticle-containing retention aid system comprising a retention system polymer and a microparticle.
• the microparticle is a synthetic layered silicate, more preferably a synthetic hydrous sodium lithium magnesium silicate, and even more preferably a synthetic hydrous sodium lithium magnesium silicate in combination with a peptizer, the most preferred peptizer being tetrasodium pyrophosphate.
• the microparticle preferably comprises one or more of Laponite RDS, XLS and DS, and more preferably comprises Laponite RDS.
• the microparticle is preferably added in an amount of from about 0.1 to about 1.0 kg/tonne of pulp on a dry basis, more preferably from about 0.2 to about 0.6 kg/tonne and even more preferably about 0.4 kg/tonne.
• the retention system polymer is preferably a flocculant and may preferably comprise any of the synthetic nitrogen-containing cationic polymers described above.
• a particularly preferred retention system polymer is BUFLOCTM 5511 , available from Buckman Laboratories International, Inc., which is a cationic polyacrylamide having a molecular weight of about 10,000,000.
• the retention system polymer is preferably added to the pulp in an amount of about 0.05 to 1.0 kg/tonne of pulp on a dry basis, more preferably from about 0.05 to about 0.5 kg/tonne and even more preferably from about 0.1 to about 0.2 kg/tonne.
• FIGs 4 and 5 differ from one another in the order of addition of the retention system polymer and the microparticle.
• the microparticle is added before the screen, more preferably between the fan pump and the screen, while the retention system polymer is added after the screen, more preferably between the screen and the head box.
• Figure 5 the order of addition is reversed, with the polymer being added before the screen, more preferably between the fan pump and the screen, and the microparticle being added after the screen, more preferably between the screen and the head box.
• the order of addition in Figure 5 is preferred.
• Laponite RD is a hydrous sodium lithium magnesium silicate
• Laponite RDS is a hydrous sodium lithium magnesium silicate with tetrasodium pyrophosphate
• Laponite JS is a hydrous sodium lithium magnesium fluorosilicate with tetrasodium pyrophosphate.
• BUFLOCTM 594 available from Buckman Laboratories International, Inc., which is a high molecular weight cationic polyacrylamide having an average molecular weight of from about 5,000,000 to about 7,000,000 units and a 21% charge density.
• a numerical value for example, "594 0. 5", the numerical value represents the amount of pounds on a dry basis of the Bufloc 594 polymer per ton of paperstock based on the dried solids weight of the paperstock.
• B 5511 and “5511” represent BUFLOCTM 5511 , available from Buckman Laboratories International, Inc., which is a cationic polyacrylamide having a molecular weight of about 10,000,000.
• BUFLOCTM 5511 available from Buckman Laboratories International, Inc.
• the numerical value represents the amount of pounds on a dry basis of the Bufloc 5511 polymer per ton of paperstock based on the dried solids weight of the paperstock.
• the order of addition is specified.
• the abbreviation "B 5511 0.5/RDS 0.5” indicates that the polymer component Bufloc 5511 is added to the furnish before the microparticle component Laponite RDS. This simulates a papermaking process in which the polymer is added prior to the final high shear stage (typically before the screen) and the microparticle is added after the final high shear stage (typically between the screen and the headbox).
• the abbreviation “RDS 0.5/B 5511 0.5” indicates that the polymer component Bufloc 5511 is added to the furnish after the microparticle component Laponite RDS. This simulates a papermaking process in which the microparticle is added prior to the final high shear stage (typically before the screen) and the polymer is added after the final high shear stage (typically between the screen and the headbox).
• Tests were conducted at a paper mill. Drainage was performed using a small screen through which 500 ml samples were drained using a modified Schopper Riegler method. Mixing was carried out in a food blender.
• Equipment used for the modified Shopper Riegler drainage test included the following: a Modified Schopper Riegler (MSR); a 1000 ml graduated cylinder; a stopwatch; a 5-gallon (18.9 I) plastic bucket; wires for MSR; a vacuum flask and funnel (for retention); Whatman ashless filter papers (for ash retention); a turbidity meter; a hemocytometer; and a microscope.
• MSR Modified Schopper Riegler
• a 1000 ml graduated cylinder a stopwatch
• a 5-gallon (18.9 I) plastic bucket wires for MSR
• a vacuum flask and funnel for retention
• Whatman ashless filter papers for ash retention
• a turbidity meter a hemocytometer
• a microscope included the following: a Modified Schopper Riegler (MSR); a 1000 ml graduated cylinder; a stopwatch; a 5-gallon (18.9 I) plastic bucket; wires for MSR; a
• Samples to be tested were taken from the headbox of the papermaking apparatus. For each test, 1000 ml was required. Because temperature has an impact on drainage, each test was run immediately after the sample was taken. For lab studies with the retention aids, the furnish was kept at the same temperature as the headbox temperature.
• the MSR was cold and the sample was hot, the MSR was warmed up by running hot water over the outside and inside of the MSR. If no hot water was available, cold water was used. All tests were conducted in the same way. It was imperative that the MSR wire was devoid of any fibers or fines. The wire was backflushed with water before the test was run. Uniform fiber, fines, and filler distribution in the sample was ensured by agitating the fiber slurry in the bucket. 1000 ml of the slurry was measured in a graduated cylinder and poured into the MSR while holding the plunger down. The graduated cylinder was placed under the MSR. The plunger was then released and the stop watch started at the same time.
• the time required for drainage of the sample in incremental units of 100 ml was measured and recorded.
• the incremental units of 100 ml chosen were purely empirical. For example, very slow draining stock samples were instead measured at 100, 150, and 200 ml drainage times. Sometimes several tests were needed to determine the starting volume tests.
• the different levels of polymers in the various samples were compared, and for this purpose, furnish samples were obtained from the machine before addition of the retention/drainage aid. Drainage and retention values were compared against blank furnishes to determine improvement.
• the MSR filtrate was filtered through a pre-weighed filter paper, dried in an oven at from 105°C. to 120°C and weighed again. The weight difference was recorded in mg/ml.
• Drainage times were compared based on different levels of additives (i.e. polymer and/or microparticle) in the furnish. Drainage times were recorded in seconds for each volume level. The total suspended solids were estimated with a turbidity meter. The filtrate could also have been filtered to determine suspended solids. Solids contents of MSR filtrate could be reported in mg/ml and used to indicate the retention capabilities of different systems, with lower numbers indicating better retention. [00080] For repeated tests, the sample was taken from the same place along the papermaking system. It was ensured that the furnish composition was the same for the repeated test. Repeated tests that did not agree within reason with a corresponding original test were suspect.
• additives i.e. polymer and/or microparticle
• the MSR was kept clean and constantly rinsed with water to keep residual fibers from building up on the sides.
• the screen was periodically cleaned to remove resin build-up, and brushed clean with a mild detergent.
• the wires were checked to make sure bent or damaged wires were not used. All tests were conducted in the same manner and at the same consistency.
• the paper mill employed a newsprint furnish comprising 70 wt % thermomechanical pulp (TMP) and 30% de-inked pulp (DIP).
• TMP thermomechanical pulp
• DIP de-inked pulp
• the pulp had a headbox conductivity of 1 ,000 microsiemens, a cationic demand of 0.15 ml/l of 0.001 N solution and a consistency of 0.65.
• the headbox pH of the paperstock was 4.83.
• Additives combined with the paperstock included calcined clay as a filler in an amount of 2 wt% based on the dried solids weight of the paperstock. The calcined clay was present in the DIP component.
• Polymer was added to the paperstock in varying amounts up to 0.75 lb/ton (0.35 kg/tonne) of paperstock, based on the dried solids weight of both the polymer and the paperstock.
• microparticle was added to the paperstock in varying amounts up to
• Tables 1 and 2 The results of the tests are shown in Tables 1 and 2 below. (Table 1 will contain the drainage/turbidity data and Table 2 will contain the retention data).
• Table 1 the column headings "100", “150 “, "200” and “250” represent the number of milliliters of filtrate collected that drained through the wire.
• the corresponding numbers underneath the column headings represent the number of seconds needed for the respective number of milliliters (ml) of filtrate to drain through the wire and be collected.
• the paperstock identified as "Blank” (having no microparticle retention system) required 27 seconds for 100 ml of filtrate to be drained through the forming wire and collected, required 58 seconds for 150 ml of filtrate to be collected, and required 90 seconds for 200 ml of filtrate to be collected.
• the turbidity measured in units of nephelometric turbidity unites (NTU) is listed in the last column.
• NTU nephelometric turbidity unites
• Each of the stock and polymer samples were prepared as follows: prepare stock and polymer samples; make sure the wire for the Britt Jar is wet; set the Britt Jar speed at the required set point and turn it on; mix chemicals into stock; pour treated stock into Britt Jar; wait 5 seconds; open clamp and start collecting filtrate; collect first 100 mL of filtrate; filter the filtrate through the pre-conditioned filter papers and dry in the oven at 110°C; and calculate the %TFPR. If required ash the dried filter papers to determine the %FPAR.
• [HB ash] is determined by ashing the HB, then multiplying the % ash value by the [HB].
• [TW ash] is determined by ashing the TW, then multiplying the % ash value by the [TW].
• Example 4 Retention Tests Comparing Laponite RD, RDS and JS [000100]
• Britt Jar tests as described in Example 2 were performed using various combinations of polymer (Bufloc 5511) and microparticles. The tests were performed with an alkaline fine paper furnish comprised of 60% hardwood and 40% softwood, having a pH of 7.9, conductivity of 670 microsiemens and ash content of 20% precipitated calcium carbonate (PCC) added at the machine chest in the paper process.
• the retention data including both total first pass retention (TFPR) and first pass ash retention (FPAR) is shown below in Table 3 and is also illustrated in Figure 11.

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