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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/71—Mixtures of material ; Pulp or paper comprising several different materials not incorporated by special processes
  • D21H17/74—Mixtures of material ; Pulp or paper comprising several different materials not incorporated by special processes of organic and inorganic material
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F226/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a single or double bond to nitrogen or by a heterocyclic ring containing nitrogen
  • C08F226/02—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a single or double bond to nitrogen or by a heterocyclic ring containing nitrogen by a single or double bond to nitrogen
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F8/00—Chemical modification by after-treatment
  • C08F8/44—Preparation of metal salts or ammonium salts
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
  • C08L33/24—Homopolymers or copolymers of amides or imides
  • C08L33/26—Homopolymers or copolymers of acrylamide or methacrylamide
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F2810/00—Chemical modification of a polymer
  • C08F2810/50—Chemical modification of a polymer wherein the polymer is a copolymer and the modification is taking place only on one or more of the monomers present in minority
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
  • C08L33/04—Homopolymers or copolymers of esters
  • C08L33/14—Homopolymers or copolymers of esters of esters containing halogen, nitrogen, sulfur, or oxygen atoms in addition to the carboxy oxygen
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L43/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and containing boron, silicon, phosphorus, selenium, tellurium or a metal; Compositions of derivatives of such polymers
  • C08L43/02—Homopolymers or copolymers of monomers containing phosphorus
• • 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

Definitions

• the present invention relates to an aqueous composition
• an aqueous composition comprising at least one finely divided filler and at least one water-soluble amphoteric copolymer, a process for the preparation of such a composition and its use as an additive in the production of paper, cardboard and board.
• Polymers having a large number of ionically dissociable groups in the main chain and/or in a side chain are referred to as polyelectrolytes. If these polymers have both anionogenic/anionic and cationogenic/cationic groups, they are amphoteric polyelectrolytes or ampholytic polymers, respectively. They are generally water-soluble or at least water-dispersible and have a wide range of applications, inter alia in the area of papermaking.
• EP-A-0 251 182 discloses a process for the preparation of polymers, a mixture of N-vinylformamide and acrylonitrile or methacrylonitrile being polymerized in the presence of free radical initiators, and the polymers then being modified by treatment with acids.
• the modified polymers are said to contain vinylamine units in the form of salts, vinylformamide units and acrylonitrile or methacrylonitrile units and, if appropriate, acrylamide units and acrylic acid units.
• the reworking of examples of this publication has, however, shown that the polymers hydrolyzed with acids contain considerable amounts of amidine units of the formula
• the hydrolyzed polymers are used as drainage aids, retention aids or for strengthening the paper in papermaking.
• EP-A-0 528 409 discloses cationic copolymers which contain from 20 to 90 mol % of amidine units. They are prepared by copolymerization of N-vinylformamide and acrylonitrile and subsequent hydrolysis of the copolymers with acids. The polymers containing amidine units are used as flocculants for sludges.
• WO 94/13882 relates to the use of copolymers which are obtainable by copolymerization of N-vinylcarboxamides, monoethylenically unsaturated carboxylic acids and, if appropriate, vinyl acetate, N-vinylpyrrolidone and/or N-vinylimidazole and, if appropriate, monomers having at least two double bonds in the molecule and subsequent partial or complete hydrolysis of the vinylcarboxamide units contained in the copolymers to amino or ammonium groups as an additive for the paper stock for increasing the drainage rate and the retention and the dry and wet strength of the paper in papermaking.
• hydrolyzed copolymers of N-vinylformamide and acrylic acid may contain considerable amounts of amidine units of the following formula where X ⁇ is an anion.
• JP-A-08059740 discloses that amphoteric water-soluble polymers are added to aqueous suspensions of inorganic particles, at least a part of the polymers being adsorbed onto the filler surface.
• the amphoteric polymers are preferably prepared by hydrolysis of copolymers of N-vinylformamide, acrylonitrile and acrylic acid in the presence of acids. They contain from 20 to 90 mol % of amidine units of the structure where R 1 and R 2 are each H or a methyl group and X ⁇ is an anion.
• the filler slurries treated with such polymers are added to the paper stock in the production of filler-containing papers.
• the filler treatment is said to lead to improved drainage of the paper stock and result in an improvement in the various strength properties of the dried paper and an improvement in the filler retention.
• US-A-2002/0088579 describes the pretreatment of inorganic fillers with cationic, anionic and amphoteric (zwitterionic) polymers.
• the treatment consists in each case of at least two stages. First the treatment with a cationic polymer and then the treatment with an anionic polymer are recommended. In further steps, further cationic and anionic polymers can be adsorbed again alternately.
• the aqueous suspensions containing the pretreated filler particles are added to the paper stock in the production of filler-containing paper.
• the filler treatment is said to lead to an improvement in various strength properties of the dried paper.
• WO 00/59965 describes a polymer composition based on polymers having phosphonate and sulfonate groups and the use thereof in papermaking.
• the polymers may additionally contain monomers having amide groups incorporated in the form of polymerized units.
• copolymers which contain N-vinylcarboxamides incorporated in the form of polymerized units and are subjected to a hydrolysis after the polymerization is not disclosed.
• aqueous slurries of finely divided fillers which are at least partly coated with such polymers for papermaking is also not described.
• It is an object of the present invention to provide an aqueous composition comprising at least one finely divided filler and at least one water-soluble amphoteric copolymer, which composition can be used in papermaking.
• Paper products produced therewith should have good performance characteristics, especially good strength properties of the dried paper. These include especially good dry breaking lengths, dry pick resistances and/or good values with regard to the internal strength.
• an aqueous composition which comprises at least one finely divided filler and at least one water-soluble amphoteric copolymer, the copolymer containing at least one monomer which is incorporated in the form of polymerized units and is selected from monoethylenically unsaturated sulfonic acids, phosphonic acids, phosphoric esters and derivatives thereof.
• the present invention therefore relates to an aqueous composition
• aqueous composition comprising at least one finely divided filler and at least one water-soluble amphoteric copolymer which is obtainable by copolymerization of a monomer mixture comprising
• alkyl comprises straight-chain and branched alkyl groups.
• Suitable alkyl groups are, for example, C 1 -C 6 -alkyl and particularly preferably C 1 -C 4 -alkyl groups.
• compounds which are derived from acrylic acid and methacrylic acid may in some cases be abbreviated by inserting the syllable “(meth)” into the compound derived from acrylic acid.
• Open-chain N-vinylamide compounds of the formula 1) which are suitable as monomers a) are, for example, N-vinylformamide, N-vinyl-N-methylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide, N-vinylpropionamide, N-vinyl-N-methylpropionamide and N-vinylbutyramide and mixtures thereof.
• Suitable monomers b) are compounds which have an organic radical having a polymerizable, ⁇ , ⁇ -ethylenically unsaturated double bond and one sulfonic or phosphonic acid group per molecule.
• the salts and esters of the abovementioned compounds are furthermore suitable.
• the esters of the phosphonic acids may be the monoesters or the diesters.
• Suitable monomers b) are furthermore monoesters of phosphoric acid with alcohols having a polymerizable, ⁇ , ⁇ -ethylenically unsaturated double bond. One or both remaining protons of the phosphoric acid group may be neutralized by suitable bases or esterified with alcohols which have no polymerizable double bonds.
• Suitable bases for the partial or complete neutralization of the acid groups of the monomers b) are, for example, alkali metal or alkaline earth metal bases, ammonia, amines and/or alkanolamines.
• alkali metal or alkaline earth metal bases ammonia, amines and/or alkanolamines.
• alkali metal or alkaline earth metal bases ammonia, amines and/or alkanolamines.
• sodium hydroxide solution sodium hydroxide solution, potassium hydroxide solution, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, magnesium oxide, calcium hydroxide, calcium oxide, triethanolamine, ethanolamine, morpholine, diethylenetriamine or tetraethylenepentamine.
• Suitable alcohols for the preparation of the esters are, for example, C 1 -C 6 -alkanols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, etc.
• the monomers b) include, for example, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, sulfoethyl acrylate, sulfoethyl methacrylate, sulfopropyl acrylate, sulfopropyl methacrylate, 2-hydroxy-3-acryloyloxypropylsulfonic acid, 2-hydroxy-3-methacryloyloxypropylsulfonic acid, styrenesulfonic acid, acrylamidomethylene-phosphonic acid, 2-acrylamido-2-methylpropanesulfonic acid, vinylphosphonic acid, CH 2 ⁇ CH—NH—CH 2 —PO 3 H, monomethyl vinylphosphonate, dimethyl vinylphosphonate, allylphosphonic acid, monomethyl allylphosphonate, dimethyl allylphosphonate, acrylamidomethylpropylphosphonic acid, (meth)acryloylethylene glycol phosphate, monovin
• component b If exclusively monomers in which all protons of the acid groups have been esterified, e.g. dimethyl vinylphosphonate or dimethyl allylphosphonate, are used as component b), at least one monoethylenically unsaturated mono- and/or dicarboxylic acid or a salt thereof, as described below as component c), is used for the polymerization. It is thus ensured that the copolymers used according to the invention have anionogenic/anionic groups. Alternatively, the conditions for the hydrolysis can also be chosen so that some of the ester groups are also cleaved.
• the abovementioned monomers b) may be used individually or in the form of any desired mixtures.
• Suitable monomers c) are monoethylenically unsaturated carboxylic acids of 3 to 8 carbon atoms, the water-soluble salts of these carboxylic acids and monoethylenically unsaturated carboxylic anhydrides. These include, for example, acrylic acid, methacrylic acid, dimethacrylic acid, ethacrylic acid, ⁇ -chloroacrylic acid, crotonic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, mesaconic acid, citraconic acid, glutaconic acid, aconitic acid, methylenemalonic acid, allylacetic acid and vinylacetic acid.
• the monomers of this group can be used alone or as a mixture with one another, in partly or in completely neutralized form, in the copolymerization. Bases suitable for the neutralization are those mentioned in the case of component b).
• the copolymers can, if appropriate, contain, incorporated in the form of polymerized units, at least one further monomer d) which is free of nitrile groups.
• additional monomers d) are preferably selected from esters of ⁇ , ⁇ -ethylenically unsaturated mono- and dicarboxylic acids with C 1 -C 30 -alkanols, C 2 -C 30 -alkanediols and C 2 -C30-aminoalcohols, amides of ⁇ , ⁇ -ethylenically unsaturated monocarboxylic acids and the N-alkyl and N,N-dialkyl derivatives thereof, esters of vinyl alcohol and allyl alcohol with C 1 -C30-monocarboxylic acids, N-vinyllactams, nitrogen-containing heterocycles having ⁇ , ⁇ -ethylenically unsaturated double bonds, vinylaromatics, vinyl halides, vinylidene halides, C 2
• Suitable additional monomers d) are, for example, methyl(meth)acrylate, methyl ethacrylate, ethyl(meth)acrylate, ethyl ethacrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, tert-butyl(meth)acrylate, tert-butyl ethacrylate, n-octyl(meth)acrylate, 1,1,3,3-tetramethylbutyl(meth)acrylate, ethylhexyl(meth)acrylate and mixtures thereof.
• Suitable additional monomers d) are furthermore the esters of ⁇ , ⁇ -ethylenically unsaturated mono- and dicarboxylic acids with aminoalcohols, preferably C 2 -C 12 -aminoalcohols. These may be C 1 -C 8 -monoalkylated or C 1 -C 8 -dialkylated on the amine nitrogen.
• Suitable acid components of these esters are, for example, acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, crotonic acid, maleic anhydride, monobutyl maleate and mixtures thereof. Acrylic acid, methacrylic acid and mixtures thereof are preferably used.
• N-methylaminomethyl(meth)acrylate N-methylaminoethyl(meth)acrylate, N,N-dimethylaminomethyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, N,N-diethylaminoethyl(meth)acrylate, N,N-dimethylaminopropyl(meth)acrylate, N,N-diethylaminopropyl(meth)acrylate, N,N-dimethylaminocyclohexyl(meth)acrylate, etc.
• Suitable additional monomers d) are furthermore acrylamide, methacrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-(n-butyl)(meth)acrylamide, tert-butyl(meth)acrylamide, n-octyl(meth)acrylamide, 1,1,3,3-tetramethylbutyl(meth)acrylamide, ethylhexyl(meth)acrylamide and mixtures thereof.
• Suitable additional monomers d) are furthermore 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxyethyl ethacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 3-hydroxybutyl acrylate, 3-hydroxybutyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl acrylate, 6-hydroxyhexyl methacrylate, etc.
• Suitable additional monomers are furthermore N-[2-(dimethylamino)ethyl]acrylamide, N-[2-(dimethylamino)ethyl]methacrylamide, N-[3-(dimethylamino)propyl]acrylamide, N-[3-(dimethylamino)propyl]methacrylamide, N-[4-(dimethylamino)butyl]acrylamide, N-[4-(dimethylamino)butyl]methacrylamide N-[2-(diethylamino)ethyl]acrylamide, etc.
• Suitable monomers d) are furthermore N-vinyllactams and derivatives thereof which may have, for example, one or more C 1 -C 6 -alkyl substituents, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, etc.
• N-vinylpyrrolidone N-vinylpiperidone, N-vinylcaprolactam
• N-vinyl-5-methyl-2-pyrrolidone N-vinyl-5-ethyl-2-pyrrolidone
• N-vinyl-6-methyl-2-piperidone N-vinyl-6-ethyl-2-piperidone
• N-vinyl-7-methyl-2-caprolactam N-vinyl-7-ethyl-2-caprolactam, etc.
• Suitable monomers d) are furthermore N-vinylimidazoles, alkylvinylimidazoles, in particular methylvinylimidazoles, such as 1-vinyl-2-methylimidazole, 3-vinylimidazole N-oxide, 2- and 4-vinylpyridines, 2- and 4-vinylpyridine N-oxides and betaine derivatives and quaternization products of these monomers.
• Suitable additional monomers are furthermore ethylene, propylene, isobutylene, butadiene, styrene, ⁇ -methylstyrene, vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride and mixtures thereof.
• copolymerization monomers e) which contain at least two double bonds in the molecule, e.g. methylenebisacrylamide, glycol diacrylate, glycol dimethacrylate, glyceryl triacrylate, pentaerythrityl triallyl ether, polyalkylene glycols or polyols, such as pentaerythritol, sorbitol or glucose, which are at least diesterified with acrylic acid and/or methacrylic acid. If at least one monomer of group (e) is used in the copolymerization, the amounts used are up to 2, e.g. from 0.001 to 1, mol %.
• a monomer mixture is used for the polymerization, the component b) consisting only of monoethylenically unsaturated sulfonic acids and/or derivatives thereof or the component b) consisting only of monoethylenically unsaturated phosphonic acids, phosphoric esters and/or derivatives thereof.
• the monomer mixture used for the polymerization preferably contains a combination of at least one compound of component b) and at least one compound of component c), in each case having a free acid group or an acid group in salt form.
• a preferred combination is, for example, vinylsulfonic acid or an alkali metal vinylsulfonate and acrylic acid.
• a further preferred combination is, for example, vinylphosphonic acid or an alkali metal vinylphosphonate and acrylic acid.
• the water-soluble amphoteric copolymers used according to the invention are preferably obtainable by free radical copolymerization of
• the preparation of the water-soluble amphoteric polymers is effected by conventional processes known to a person skilled in the art. Suitable processes are described, for example, in EP-A-0 251 182 and WO 94/13882, which are hereby incorporated by reference.
• the water-soluble amphoteric polymers can be prepared by solution, precipitation, suspension or emulsion polymerization.
• Solution polymerization in aqueous media is preferred.
• Suitable aqueous media are water and mixtures of water and at least one water-miscible solvent, for example an alcohol, such as methanol, ethanol, n-propanol, etc.
• the polymerization temperatures are preferably from about 30 to 200° C., particularly preferably from 40 to 110° C.
• the polymerization is usually effected under atmospheric pressure but may also take place under reduced or superatmospheric pressure.
• a suitable pressure range is from 1 to 5 bar.
• the monomers b) containing acid groups are preferably used in the salt form.
• the pH is preferably brought to a value of from 6 to 9.
• the pH can be kept constant during the polymerization.
• the monomers can be polymerized with the aid of free radical initiators.
• Initiator mixtures or redox initiator systems e.g. ascorbic acid/iron(II) sulfate/sodium peroxodisulfate, tert-butyl hydroperoxide/sodium disulfite, tert-butyl hydroperoxide/sodium hydroxymethanesulfinate, H 2 O 2 /Cu I , are also suitable.
• ascorbic acid/iron(II) sulfate/sodium peroxodisulfate tert-butyl hydroperoxide/sodium disulfite
• tert-butyl hydroperoxide/sodium hydroxymethanesulfinate H 2 O 2 /Cu I
• the polymerization can be effected in the presence of at least one regulator.
• Regulators which may be used are the conventional compounds known to a person skilled in the art, for example sulfur compounds, e.g. mercaptoethanol, 2-ethylhexyl thioglycolate, thioglycolic acid or dodecyl mercaptan, and tribromochloromethane or other compounds which have a regulating effect on the molecular weight of the polymers obtained.
• the molar masses of the water-soluble amphoteric polymers is, for example, at least 10 000, preferably at least 100 000, in particular at least 500 000, Dalton.
• the molar masses of the polymers are then, for example, from 10 000 to 10 million, preferably from 100 000 to 5 million (for example, determined by light scattering).
• This molar mass range corresponds, for example, to K values of from 5 to 300, preferably from 10 to 250 (determined according to H. Fikentscher in 5% strength aqueous sodium chloride solution at 25° C. and a polymer concentration of 0.5% by weight).
• the copolymers may be hydrolyzed to an extent of from 0.1 to 100 mol %, e.g. from 70 to 100 mol %. In most cases, the degree of hydrolysis of the homo- and copolymers is from 1 to 98, preferably from 10 to 95, mol %.
• the copolymers may contain amidine units, which form, for example, by reaction of formic acid with two neighboring amino groups or by intramolecular reaction of an amino group with a neighboring amide group, for example of N-vinylformamide incorporated in the form of polymerized units.
• amidine units formed in the hydrolysis of vinylformamide units with acids or bases are of the formula IV where X ⁇ is an anion.
• the hydrolyzed copolymers contain, for example,
• Particularly preferred hydrolyzed copolymers are those which contain
• novel aqueous compositions are preferably present in the form of a slurry.
• Suitable fillers are all pigments which can usually be used in the paper industry, e.g. calcium carbonate, which may be used in the form of ground calcium carbonate (GCC), chalk, marble or precipitated calcium carbonate (PCC), talc, kaolin, bentonite, satin white, calcium sulfate, barium sulfate and titanium dioxide. It is also possible to use mixtures of two or more pigments.
• the particle diameter of the finely divided fillers is, for example, such that from 40 to 90% of the particles are smaller than 2 ⁇ m.
• aqueous slurries of finely divided fillers which may be anionically dispersed are treated with at least one water-soluble amphoteric polymer.
• at least one water-soluble amphoteric polymer For example, from 0.1 to 5% by weight, based on fillers, of a water-soluble amphoteric polymer can be added to an aqueous slurry containing from 1 to 50% by weight of at least one finely divided filler, or an aqueous slurry of a finely divided filler can be introduced into an aqueous solution of an amphoteric polymer and the components mixed in each case.
• the copolymers used according to the invention have a relatively large number of ionically dissociable/dissociated groups of opposite chargeability/charge which are bonded to the polymer chain.
• Coulomb interactions may occur.
• the surface charge may additionally be measured by zeta potential measurements which show that the charge is on the outside.
• the electrophoretic mobility and the zeta potential can be determined by a laser optical method.
• the measuring instrument used is, for example, a Zetasizer 3000 HS from Malvern Instruments Ltd.
• the K values of the copolymers were determined according to H. Fikentscher, Cellulosechemie 13 (1932), 48-64 and 71-74, in 1.0% aqueous sodium chloride solution at 25° C. at a pH of 7 and a polymer concentration of 0.1% by weight.
• the degree of hydrolysis of the polymers can be determined by enzymatic analysis of the formic acid/formates liberated in the hydrolysis.
• the structural composition of the polymer was calculated from the monomer mixture used, the degree of hydrolysis and the vinylamine/amidine ratio determined by means of 13 C-NMR spectroscopy. For this purpose, the ratio of the integrals of the two following signals were evaluated: Group Position of the signal [ppm] Area HCOO ⁇ 173 A (formate) —N ⁇ CH—N— 152 A (amidine)
• the polymer I obtained has the following structural units: vinylformamide: 35 mol % vinylamine and amidine: 27 mol % sodium vinylsulfonate: 11 mol % sodium acrylate: 27 mol %
• the polymer II obtained has the following structural units: vinylformamide: 18 mol % vinylamine and amidine: 43 mol % sodium vinylsulfonate: 11 mol % sodium acrylate: 28 mol %
• 500.0 g of the above product are heated to 80° C. in a 1 l four-necked flask having a paddle stirrer, internal thermometer, dropping funnel and reflux condenser at a stirrer speed of 80 rpm.
• 200 g of distilled water, 6.3 g of a 40% strength aqueous sodium disulfite solution and then 35.2 g of a 25% strength aqueous sodium hydroxide solution are added so that they mix in thoroughly.
• the reaction mixture is kept at 80° C. for 3 hours and then cooled to room temperature.
• By slow addition of about 17 g of concentrated hydrochloric acid the pH is brought to 7.9, and then 42.8 g of distilled water are added for dilution. After cooling to room temperature, a viscous, colorless, slightly turbid solution having a solids content of 13.3% is obtained.
• the degree of hydrolysis is 37% (based on VFA).
• the polymer IlIl obtained has the following structural units: vinylformamide: 36 mol % vinylamine and amidine: 26 mol % sodium vinylsulfonate: 11 mol % sodium acrylate: 27 mol %
• a further 56.0 g of a 1.5% strength aqueous solution of 2,2′-azobis(2-methyl-propionamidine)dihydrochloride are added in the course of 4 hours. After the end of the addition, the reaction mixture is kept at 50° C. for a further 4 hours. Thereafter, 0.2 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 20 g of distilled water is added and the temperature is kept at 50° C. for a further 3 hours. The temperature is then increased to 75° C. for 2 hours. The solution obtained is diluted with 250.0 g of distilled water and cooled to room temperature.
• a clear, yellowish, viscous solution having a solids content of 29.6% is obtained.
• the K value of the copolymer is 81.
• 360 g of the above product are heated to 80° C. in a 1 l three-necked flask having a paddle stirrer, internal thermometer, dropping funnel and reflux condenser at a stirrer speed of 80 rpm.
• First 4.5 g of a 40% strength aqueous sodium disulfite solution and then 48.1 g of a 25% strength aqueous sodium hydroxide solution are added so that they mix in thoroughly.
• the reaction mixture is kept at 80° C. for 3.5 hours and then cooled to room temperature.
• By slow addition of about 23 g of concentrated hydrochloric acid the pH is brought to 7.6.
• a viscous, yellow, clear solution having a solids content of 28.5% is obtained.
• the degree of hydrolysis is 31% (based on VFA).
• the polymer IV obtained has the following structural units: vinylformamide: 48 mol % vinylamine and amidine: 25 mol % sodium vinylsulfonate: 27 mol %
• the polymer V obtained has the following structural units: vinylformamide: 46 mol % vinylamine and amidine: 17 mol % sodium vinylphosphonate: 5 mol % sodium acrylate: 32 mol %
• a slightly turbid, colorless, viscous solution having a solids content of 30.1% is obtained.
• the K value of the terpolymer is 85.
• a viscous, colorless, slightly turbid solution having a solids content of 29.0% is obtained.
• the degree of hydrolysis is 27% (based on VFA).
• the polymer VI obtained has the following structural units: vinylformamide: 52 mol % vinylamine and amidine: 21 mol % sodium vinylphosphonate: 11 mol % sodium acrylate: 16 mol %
• TMP thermomechanical pulp
• groundwood was beaten in the ratio of 70/30 at a solids concentration of 4% in a laboratory pulper until free of specks and until the freeness of 60-65 was reached.
• the pH of the stock was then from 7 to 8.
• the beaten stock was then diluted with drinking water to a solids concentration of 0.35%.
• the paper sheets were produced in each case on a Rapid-Köthen sheet former according to ISO 5269/2 with a sheet weight of 80 g/m 2 , and then dried for 7 minutes at 90° C. and then calendered with a nip pressure of 200 N/cm.
• a mixture of bleached birch sulfate and bleached pine sulfite was beaten in the ratio of 70/30 at a solids concentration of 4% in a laboratory pulper until free of specks and until a freeness of 55-60 was reached.
• An optical brightener (Blankophor PSG from Ciba) and a cationic starch (HiCat 5163 A from Roquette) were then added to the beaten stock.
• the digestion of the cationic starch takes place as a 10% strength starch slurry in a jet cooker at 130° C. in a residence time of 1 minute.
• the dosage of the optical brightener was 0.5%, based on dry content of the paper stock suspension, of commercial product.
• the dosage of the cationic starch was 0.5%, based on the dry content of the paper stock suspension, of starch.
• the pH of the stock was then from 7 to 8.
• the beaten stock was then diluted with drinking water to a solids concentration of 0.35%.
• the paper sheets were produced in each case on a Rapid-Köthen sheet former according to ISO 5269/2 with a sheet weight of 80 g/m 2 and then dried for 7 minutes at 90° C.

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• 2003
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