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
  • 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
  • D21H23/08—Controlling the addition by measuring pulp properties, e.g. zeta potential, pH
• • 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
  • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
  • D21H11/14—Secondary fibres
• • 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
  • D21H17/01—Waste products, e.g. sludge
• • 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
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/24—Polysaccharides
• • 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
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/24—Polysaccharides
  • D21H17/28—Starch
• • 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
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/24—Polysaccharides
  • D21H17/31—Gums
  • D21H17/32—Guar or other polygalactomannan gum
• • 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
  • D21H17/67—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
  • D21H23/08—Controlling the addition by measuring pulp properties, e.g. zeta potential, pH
  • D21H23/10—Controlling the addition by measuring pulp properties, e.g. zeta potential, pH at least two kinds of compounds being added

Definitions

• This invention relates to papermaking and more specifically to a process for the production of paper in which a cationic organic polymer having a hydrophobic group and an anionic microparticulate material are added to a papermaking stock The process provides improved drainage and retention
• an aqueous suspension containing cellulosic fibres, and optional fillers and additives referred to as stock
• a headbox which ejects the stock onto a forming wire
• Water is drained from the stock through the forming wire so that a wet web of paper is formed on the wire, and the web is further dewatered and dried in the drying section of the paper machine
• white water which usually contains fine particles, e g fine fibres, fillers and additives
• Drainage and retention aids are conventionally introduced into the stock in order to facilitate drainage and increase adsorption of fine particles onto the cellulosic fibres so that they are retained with the fibres on the wire
• Cationic organic polymers like cationic starch and cationic acrylamide- based polymers are widely used as drainage and retention aids
• the present invention relates to a process for the production of paper from a suspension containing cellulosic fibres, and optional fillers, which comprises adding to the suspension a cationic organic polymer and an anionic microparticulate material, forming and dewatering the suspension on a wire, wherein the cationic organic polymer has a non-aromatic hydrophobic group
• the process further comprises forming and dewatering the suspension on a wire to obtain a wet web containing cellulosic fibres, or paper, and white water, recirculating the white water and optionally introducing fresh water to form a suspension containing cellulosic fibres, and optional fillers, to be dewatered to form paper, wherein the amount of fresh water introduced is less than 30 tons per ton
• the main polymer can be selected from homopolymers and copolymers prepared from one or more monomers comprising at least one monomer having a hydrophobic group, suitably an ethylenically unsaturated monomer, and the main polymer is preferably a vinyl addition polymer
• suitable main polymers include cationic vinyl addition polymers obtained by polymerizing a cationic monomer having a non- aromatic hydrophobic group or a monomer mixture comprising such a monomer
• the cationic monomer having a non-aromatic hydrophobic group is represented by the general formula (I)
• R. is H or CH 3
• R 2 and R 3 are each H or, preferably, an alkyl group having from 1 to 3 carbon atoms, suitably 1 to 2 carbon atoms
• A is O or NH
• B is an alkylene group of from 2 to 8 carbon atoms, suitably 2 to 4 carbon atoms, or a hydroxy propylene group
• R 4 is a substituent containing a hydrophobic group, suitably a non-aromatic hydrocarbon group containing at least 2 carbon atoms, suitably from 3 to 12 and preferably from 4 to 8 carbon atoms
• X " is an anionic countenon, usually a halide like chloride
• R 4 usually comprises and, preferably, is selected from any of the linear, branched or cyclic alkyl groups mentioned above and the total number of carbon atoms of the groups
• R 2 , R 3 and R 4 is usually at least 4, suitably at least 5 and preferably at least 6
• suitable cationic monomers having a non-aromatic hydrophobic group include (meth)- acryloxyethyl-N,N-d ⁇ methyl-N-n-butylammon ⁇ um chloride, (meth)acryloxyam ⁇ noethyl-N,N- dimethyl-N-n-butylammonium chloride, (meth)acryloxypropyl-N,N-d ⁇ methyl-N-t-butyl- ammonium chloride, (meth)acryloxyam ⁇ nopropyl-N,N-d ⁇ methyl-N-t-butylammon ⁇ um chloride, (meth)acryloxyam ⁇ nopropyl-N,N-d ⁇ methyl-N-n-hexylammon ⁇ um chloride, (meth)- acryloxyethyl-N,N-d ⁇ methyl-N-n-hexylammon ⁇ um
• suitable copolymerizable monomers of this type include (meth)- acrylamide acrylamide-based monomers like N-alkyl (meth)acrylam ⁇ des and N,N-d ⁇ alkyl (meth)acrylam ⁇ des, e g N-n-propylacrylamide, N-isopropyl (meth)acrylam ⁇ de, N-n-butyl (meth)acrylam ⁇
• Suitable copolymerizable cationic monomers include the monomers represented by the general formula (III)
• R is H or CH 3
• R 2 and R 3 are each H or, preferably, an alkyl group having from 1 to 3 carbon atoms, suitably 1 to 2 carbon atoms
• A is O or NH
• B is an alkylene group of from 2 to 8 carbon atoms, suitably 2 to 4 carbon atoms, or a hydroxy propylene group
• R 7 is H a hydrocarbon group, suitably alkyl, having from 1 to 3 carbon atoms, suitably 1 to 2 carbon atoms or a substituent containing an aromatic group, suitably a phenyl or substituted phenyl group, which can be attached to the nitrogen by means of an alkylene group usually having from 1 to 3 carbon atoms, suitably 1 to 2 carbon atoms, for example a benzyl group (— CH 2 -C 6 H 5 ) or a phenylethyl group (-CH 2 -CH
• suitable main polymers include cationic vinyl addition polymers obtained by polymerizing a monomer mixture comprising at least one non-cationic ethylenically unsaturated monomer having a non- aromatic hydrophobic group and at least one cationic ethylenically unsaturated monomer, the non-aromatic hydrophobic group being as defined above, and this invention further relates to a cationic vinyl addition polymer having a non-aromatic hydrophobic group, its preparation and use, as further defined in the claims
• Suitable non-cationic monomers having a non-aromatic hydrophobic group include non-ionic monomers, preferably a non- lonic monomer represented by the general formula (IV)
• the total number of carbon atoms of the groups R 8 and R 9 is usually at least 2, suitably at least 3 and notably from 3 to 6
• suitable copolymerizable monomers of this type include acrylamide-based monomers like N-alkyl (meth)acrylam ⁇ des
• R is H or CH 3
• A is O or NH
• B is an alkylene group of from 2 to 4 carbon atoms, suitably 2 to 3 carbon atoms, preferably ethylene (-CH 2 -CH 2 -) or propylene (-CH 2 -CH(CH 3 )- or -CH(CH 3 ) - CH 2 -)
• n is an integer of at least 1 , suitably from 2 to 40 and preferably 3 to 20
• R 10 is a substituent containing a hydrophobic group, suitably alkyl, having at least 2 carbon atoms, suitably from 3 to 12 and preferably from 4 to 8 carbon atoms
• suitable copolymerizable monomers of this type include alkyl (mono-, di- and polyethyleneglycol) (meth)acrylates and alkyl (mono-, di- and polypropyleneglycol) (meth)acrylates, e g ethyltnglycol (meth)acrylate and butyl
• Main polymers according to this invention can be prepared from a monomer mixture generally comprising from 1 to 99 mole%, suitably from 2 to 50 mole% and preferably from 5 to 25 mole% of monomer having a non-aromatic hydrophobic group, and from 99 to 1 mole%, suitably from 98 to 50 mole% and preferably from 95 to 75 mole% of other copolymerizable monomers which preferably comprises acrylamide or methacrylamide ((meth)acryiam ⁇ de), the monomer mixture suitably comprising from 98 to 50 mole% and preferably from 95 to 75 mole% of (meth)acrylam ⁇ de, the sum of percentages being 100
• the monomer having a non- aromatic hydrophobic group is cationic
• the monomer having a non-aromatic hydrophobic group is non-cationic and the monomer mixture thus also comprises a copolymerizable cationic monomer which suitably is present in an amount of from
• the main polymer according to this invention can be prepared by polymerization of monomers in known manner and the polymerization is suitably carried out in an aqueous or inverse emulsion phase
• the monomer(s) used including the monomer having a hydrophobic group described above, are preferably at least in part soluble in the aqueous phase
• Polymerization processes are generally known in the art and reference is made to Encyclopedia of Polymer Science and Engineering, Vol 1-18, John Wiley & Sons, 1985, which is hereby incorporated herein by reference
• the polymerization is suitably initiated in an aqueous phase containing monomers, a conventional free-radical polymerization initiator and optionally chain-transfer agent for modifying the molecular weight of the polymer, and is suitably carried out in the absence of oxygen in an inert gas atmosphere, for example under nitrogen
• the polymerization suitably takes place under stirring at temperatures between 20 and 100°C, preferably between 40 and 90°C
• the charge density of the main polymer is from 0 2 to 5 0 meqv/g of dry polymer, suitably from 0 6 to 3 0
• the weight average molecular weight of synthetic main polymers is usually at least about 500,000, suitably above about 1 ,000,000 and preferably above about 2,000,000
• the upper limit is not critical, it can be about 30,000,000, usually 25,000,000 and suitably 20,000,000
• the main polymer of this invention may be in any state of aggregation such as, for example, in solid form, e g powders, in liquid form, e g solutions, emulsions, dispersions including salt dispersions, etc
• the main polymer When being added to the stock, the main polymer is suitably in liquid form, e g in the form of an aqueous solution or dispersion
• the anionic microparticulate material according to this invention can be selected from inorganic and organic particles
• Anionic inorganic particles that can be used according to the invention include anionic silica-based particles and clays of the smectite type It is preferred that the anionic inorganic particles are in the colloidal range of particle size
• Anionic silica-based particles, i e particles based on S ⁇ 0 2 or silicic acid, are preferably used and such particles are usually supplied in the form of aqueous colloidal dispersions, so-called sols
• suitable silica-based particles include colloidal silica and different types of polysilicic acid
• the silica-based sols can also be modified and contain other elements, e g aluminium and/or boron, which can be present in the aqueous phase and/or in the silica-based particles
• Suitable silica-based particles of this type include colloidal aluminium-modified silica and aluminium silicates Mixtures of such suitable sih
• Anionic silica-based particles suitably have an average particle size below about 50 nm, preferably below about 20 nm and more preferably in the range of from about 1 to about 10 nm
• the particle size refers to the average size of the primary particles, which may be aggregated or non-aggregated
• the specific surface area of the silica-based particles is suitably above 50 m 2 /g and preferably above 100 m 2 /g
• the specific surface area can be up to about 1700 m 2 /g and preferably up to
• the specific surface area can be measured by means of titration with NaOH in known manner, e g as described by Sears in Analytical Chemistry 28(1956) 12, 1981-1983 and in U S Patent No 5,176,891
• the given area thus represents the average specific surface area of the particles
• the anionic inorganic particles are silica-based particles having a specific surface area within the range of from 50 to 1000 m 2 /g, preferably from 100 to 950 m 2 /g Sols of silica-based particles these types also encompass modified sols like aluminium-containing silica-based sols and boron-containing silica-based sols
• the silica-based particles are present in a sol having an S- value in the range of from 8 to 45%, preferably from 10 to 30%, containing silica-based particles with a specific surface area in the range of from 300 to 1000 m 2 /g, suitably from 500 to 950 m 2 /g, and preferably from 750 to 950 m 2 /g, which sols can be modified with aluminium and/or boron as mentioned above
• the particles can be surface- modified with aluminium to a degree of from 2 to 25% substitution of silicon atoms
• the S- value can be measured and calculated as described by Her
• Clays of the smectite type that can be used in the process of the invention are known in the art and include naturally occurring, synthetic and chemically treated materials
• suitable smectite clays include montmo ⁇ llonite/bentonite, hectonte, beidelite nontronite and saponite, preferably bentonite and especially such bentonite which after swelling preferably has a surface area of from 400 to 800 m 2 /g
• Suitable clays are disclosed in U S Patent Nos 4,753,710, 5,071 ,512, and 5,607,552, which are hereby incorporated herein by reference
• Anionic organic particles that can be used according to the invention include highly cross-linked anionic vinyl addition polymers, suitably copolymers comprising an anionic monomer like acrylic acid, methacrylic acid and sulfonated or phosphonated vinyl addition monomers, usually copolymerized with nonionic monomers like (meth)acrylam ⁇ de, alkyl
• anionic organic particles also include anionic condensation polymers, e g melamine-sulfonic acid sols
• the drainage and retention aids (agents) according to the present invention may also comprise further components such as, for example, low molecular weight cationic organic polymers and/or aluminium compounds
• drainage and retention aids refers to two or more components (aids, agents or additives) which, when being added to a stock, give better drainage and/or retention than is obtained when not adding the components
• LMW cationic organic polymers that can be used include those commonly referred to and used as anionic trash catchers (ATC) ATC's are known in the art as neutralizing and/or fixing agents for detrimental anionic substances present in the stock and the use thereof in combination with drainage and retention aids often provide further improved drainage and/or retention
• ATC anionic trash catchers
• the LMW cationic organic polymer can be derived from natural or synthetic sources, and preferably it is an LMW synthetic polymer Suitable organic polymers of this type include LMW highly charged cationic organic polymers such as polyamines, polyamidoamines, polyethyleneimines, homo- and copolymers based on diallyldimethyl ammonium chloride, (meth)acrylam ⁇ des and (meth)acrylates
• the molecular weight of the LMW cationic organic polymer is usually lower, it is suitably at least 2,000 and preferably at least 10,000 The upper limit of the molecular weight is usually about 700,000, suit
• Aluminium compounds that can be used according to this invention include alum, aluminates, aluminium chloride, aluminium nitrate and polyaluminium compounds, such as polyaluminium chlorides, polyaluminium sulphates, polyaluminium compounds containing both chloride and sulphate ions, polyaluminium silicate-sulphates, and mixtures thereof
• the polyaluminium compounds may also contain other anions than chloride ions, for example anions from sulfu ⁇ c acid, phosphoric acid, organic acids such as citric acid and oxalic acid
• the components of drainage and retention aids according to the invention can be added to the stock in conventional manner and in any order It is preferred to add the main polymer to the stock before adding the anionic microparticulate material, even if the opposite order of addition may be used It is further preferred to add the main polymer before a shear stage, which can be selected from pumping, mixing, cleaning, etc , and to add the anionic particles after that shear stage When
• the LMW cationic organic polymer and the main polymer can be introduced into the stock essentially simultaneously, either separately or in admixture, e g as disclosed in U S Patent No 5,858,174, which is hereby incorporated herein by reference
• the components of the present drainage and retention aids are added into the stock to be dewatered in amounts which can vary within wide limits depending on, inter alia, type and number of components, type of furnish, filler content, type of filler, point of addition, salt content, etc Generally the components are added in an amount that give better drainage and/or retention than is obtained when not adding the components
• the main polymer is usually added in an amount of at least 0 001 %, often at least 0 005% by weight, based on dry stock substance, and the upper limit is usually 3% and suitably 1 5% by weight
• the anionic microparticulate material is usually added in an amount of at least 0 001% by weight, often at least 0 005% by weight, based on dry substance of the stock, and the upper limit is usually 1 0% and suitably 0 6% by weight
• the total amount added is suitably within the range of from 0 005 to 0 5% by weight, calculated as S ⁇ 0 2 and based on dry stock substance
• the process of the invention is preferably used in the manufacture of paper from a suspension containing cellulosic fibres, and optional fillers, having a high conductivity
• the conductivity of the stock that is dewatered on the wire is at least 0 75 mS/cm, suitably at least 2 0 mS/cm, preferably at least 3.5 mS/cm
• Very good results have been observed at conductivity levels above 5 0 mS/cm and even above 7 5 mS/cm
• Conductivity can be measured by standard equipment such as, for example a WTW LF 539 instrument supplied by Christian Berner
• the values referred to above are suitably determined by measuring the conductivity of the cellulosic suspension that is fed into or present in the headbox of the paper machine or, alternatively, by measuring the conductivity of white water obtained by dewatering the suspension
• High conductivity levels mean high contents of salts (electrolytes), where the various salts can be based on mono-, di- and multivalent
• the invention is further suitably used in papermaking processes where white water is extensively recirculated (recycled), i e with a high degree of white water closure, for example where from 0 to 30 tons of fresh water are used per ton of dry paper produced, usually less than 20, suitably less than 15, preferably less than 10 and notably less than 5 tons of fresh water per ton of paper
• Recirculation of white water obtained in the process suitably comprises mixing the white water with cellulosic fibres and/or optional fillers to form a suspension to be dewatered, preferably it comprises mixing the white water with a suspension containing cellulosic fibres, and optional fillers, before the suspension enters the forming wire for dewatering
• the white water can be mixed with the suspension before, between or after introducing the drainage and retention aids
• Fresh water can be introduced in the process at any stage, for example, it can be mixed with cellulosic fibres in order to form a suspension, and it can be mixed with a suspension containing cellulosic fibre
• additives which are conventional in papermaking can of course be used in combination with the additives according to the invention, such as, for example, dry strength agents, wet strength agents, sizing agents, e g those based on rosin, ketene dimers and acid anhydrides, optical brightening agents, dyes, etc
• the cellulosic suspension, or stock can also contain mineral fillers of conventional types such as, for example, kaolin, china clay, titanium dioxide, gypsum, talc and natural and synthetic calcium carbonates such as chalk, ground marble and precipitated calcium carbonate
• mineral fillers of conventional types such as, for example, kaolin, china clay, titanium dioxide, gypsum, talc and natural and synthetic calcium carbonates such as chalk, ground marble and precipitated calcium carbonate
• paper as used herein, of course include not only paper and the production thereof, but also other sheet or web-like products, such as for example board and paperboard, and the production thereof
• the process can be used in the production of paper from different types of suspensions of cellulose-containing fibres and the suspensions should suitably contain at least 25% by weight and preferably at least 50% by weight of such fibres, based on dry substance
• the suspensions can be based on fibres from chemical pulp such as sulphate, sulphite and organosolv pulps, mechanical pulp such as thermomechanical pulp, chemo- thermomechanical pulp, refiner pulp and groundwood pulp, from both hardwood and softwood, and can also be based on recycled fibres, optionally from de-inked pulps, and mixtures thereof
• Cationic polymers were prepared by polymerizing a monomer mixture according to the following general procedure
• Polymers according to the invention P1 to P5, and polymers intended for comparison purposes, Ref 1 and Ref 2, were prepared from the indicated monomers in the indicated amounts P1 acrylamide (90 mole%), and acryloxyethyl dimethyl n-butylammonium chloride (10 mole%), P2 acrylamide (90 mole%) and acryloxyethyl dimethyl methylcyclohexylammonium chloride (10 mole%),
• Example 2 Drainage and retention performance was evaluated by means of a Dynamic Drainage Analyser (DDA), available from Aknbi, Sweden, which measures the time for draining a set volume of stock through a wire when removing a plug and applying vacuum to that side of the wire opposite to the side on which the stock is present
• DDA Dynamic Drainage Analyser
• First pass retention was evaluated by measuring, with a nephelometer, the turbidity of the filtrate, the white water, obtained by draining the stock
• the furnish used was based on 56% by weight of peroxide bleached TMP/SGW pulp (80/20), 14% by weight of bleached birch/pine sulphate pulp (60/40) refined to 200° CSF and 30% by weight of china clay
• To the stock was added 40 g/l of a colloidal fraction, bleach water from an SC mill, filtrated through a 5 ⁇ m screen and concentrated with an UF filter, cut off 200,000 Stock volume was 800 ml, consistency 0 14% and pH 7 0 Conductivity was adjusted to about 2 5 mS/cm by addition of calcium chloride (400 ppm Ca)
• the stock was stirred in a baffled jar at a speed of 1500 rpm throughout the test and additions were conducted as follows i) adding cationic polymer to the stock following by stirring for 30 seconds, n) adding anionic microparticulate material to the stock followed by stirring for 15 seconds, m) draining the stock while automatically recording the drainage time
• the cationic polymers tested in this Example were P1 and Ref. 1 according to in Example 1.
• the anionic microparticulate material used in this Example was a sol of silica- based particles of the type disclosed in U.S. Patent No. 5,368,833.
• the sol had an S- value of about 25% and contained silica particles with a specific surface area of about 900 m 2 /g which were surface-modified with aluminium to a degree of 5%.
• the silica- based sol was added to the stock in an amount of 1.5 kg/ton, calculated as Si0 2 and based on dry stock system.
• Table 1 shows the drainage time and retention values at various dosages of P1 and Ref. 1 , calculated as dry polymer on dry stock system (kg/ton).
• the anionic inorganic material according to Example 2 were similarly used in this Example and was added in an amount of 1.5 kg/ton, calculated as SiO 2 and based on dry stock system.
• the polymers used in this Example were P1 , P2 and Ref. 1 according to
• Example 1 Table 2 shows the dewatering and retention effect at various dosages of P1 ,
• the stock used in this Example was similar to the stock used according to Example 3 and had a conductivity of about 7.0 mS/cm (1300 ppm Ca).
• the anionic inorganic material according to Example 2 was added in an amount of 1.5 kg/ton, calculated as Si0 2 and based on dry stock system.
• the polymers used were P3 and Ref.
• Table 3 shows the results of the dewatering tests at various dosages of P3 and Ref. 1 , calculated as dry polymer on dry stock system.
• Example 2 the dewatering performance was evaluated according to the procedure described in Example 2.
• the stock used in this test series was similar to the one according to Example 2 and had a conductivity of about 2.5 mS/cm.
• the polymers used were P4, P5 and Ref. 2 according to Example 1 which were added in an amount of 2 kg/ton, calculated as dry polymer on dry stock system.
• the anionic inorganic material according to Example 2 was similarly used in this test series.
• Table 4 shows the results of the dewatering tests at various dosages of anionic inorganic material, calculated as Si0 2 and based on dry stock system.
• Example 2 The furnish was the same as used in Example 2 Stock volume was 800 ml and pH about 7 Sodium chloride (550 ppm Na) and calcium chloride were added to the stock to adjusted the conductivity to 5 0 mS/cm (400 ppm Ca) and 7 0 mS/cm (1300 ppm Ca)
• the polymers P2, P3, Ref 1 and anionic microparticles according to Example 1 were similarly used in this test series in conjunction with a low molecular weight cationic polyamine
• the polyamine was added to the stock followed by stirring for 30 seconds before addition of the cationic acrylamide-based polymer
• the polyamine was added in an amount of 3 kg/ton, calculated as dry polymer on dry stock system
• the main polymers P2, P3 and Ref 1 were added in an amount of 1 5 kg/ton, calculated as dry polymer on dry stock system
• Table 5 shows the dewatering and retention effect at various conductivities and dosages of silica-based particles, calculated as S ⁇ 0 2 and based on dry stock system
• Example 7 In this test series, dewatering and retention performance was evaluated according to the procedure described in Example 2
• Example 2 The furnish was the same as used in Example 2 Stock volume was 800 ml and pH about 7 Varying amounts of sodium chloride was added to the stock to adjust the conductivity to 2 5 mS/cm (550 ppm Na) (Test Series Nos 1-3), 5 0 mS/cm (1470 ppm Na) (Test Series Nos 4-6) and 10 0 mS/cm (3320 ppm Na) (Test Series Nos 7-9)
• the cationic polymers used were P1 to P3 and Ref 1 according to Example 1
• the anionic microparticulate material used was hydrated suspension of powdered Na- bentonite in water
• Table 6 shows the dewatering and retention effect at various dosages of cationic polymer calculated as dry polymer on dry stock system, and bentonite, calculated as dry on dry stock system Table 6

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• Polymers With Sulfur, Phosphorus Or Metals In The Main Chain (AREA)

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