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
  • D21H23/22—Addition to the formed paper
  • D21H23/66—Treating discontinuous paper, e.g. sheets, blanks, rolls
• • 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
• • 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
  • D21H17/46—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/54—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen
  • D21H17/55—Polyamides; Polyaminoamides; Polyester-amides
• • 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
  • D21H17/46—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/54—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen
  • D21H17/56—Polyamines; Polyimines; Polyester-imides
• • 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
  • D21H19/00—Coated paper; Coating material
  • D21H19/10—Coatings without pigments
• • 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
  • D21H19/00—Coated paper; Coating material
  • D21H19/10—Coatings without pigments
  • D21H19/12—Coatings without pigments applied as a solution using water as the only solvent, e.g. in the presence of acid or alkaline compounds
• • 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
  • D21H19/00—Coated paper; Coating material
  • D21H19/36—Coatings with pigments
  • D21H19/38—Coatings with pigments characterised by the pigments
  • D21H19/385—Oxides, hydroxides or carbonates
• • 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
  • D21H19/00—Coated paper; Coating material
  • D21H19/36—Coatings with pigments
  • D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
  • D21H19/54—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
  • D21H19/00—Coated paper; Coating material
  • D21H19/36—Coatings with pigments
  • D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
  • D21H19/56—Macromolecular organic compounds or oligomers thereof obtained by reactions only involving carbon-to-carbon unsaturated bonds
• • 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
  • D21H19/00—Coated paper; Coating material
  • D21H19/36—Coatings with pigments
  • D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
  • D21H19/56—Macromolecular organic compounds or oligomers thereof obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H19/60—Polyalkenylalcohols; Polyalkenylethers; Polyalkenylesters
• • 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
  • D21H19/00—Coated paper; Coating material
  • D21H19/36—Coatings with pigments
  • D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
  • D21H19/64—Inorganic compounds
• • 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
  • D21H21/14—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 characterised by function or properties in or on the paper
  • D21H21/18—Reinforcing agents
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21J—FIBREBOARD; MANUFACTURE OF ARTICLES FROM CELLULOSIC FIBROUS SUSPENSIONS OR FROM PAPIER-MACHE
  • D21J1/00—Fibreboard
  • D21J1/08—Impregnated or coated fibreboard

Definitions

• the present invention relates to an aqueous surface coating composition for paper and board with a solids content of 1 to 55 wt % comprising
• the present invention further relates to a method for producing paper and board using the aqueous surface coating composition, and to corrugated boards produced from this paper.
• An important requirement in the packaging paper segment is the strength of the paper, since an important basis for such paper are recycled fibers, which lose length as a result of the recycling and hence lead to a successive decrease in the strength of the paper.
• the paper stock is often admixed with assistants such as wet and dry strength agents, such as cationic and anionic polyacrylamide or polyvinylamine, retention agents, and sizing agents.
• assistants such as wet and dry strength agents, such as cationic and anionic polyacrylamide or polyvinylamine, retention agents, and sizing agents.
• the effect of cationic strengtheners in the paper stock is partly undone by anionic compounds from the recycling process. Attempts are therefore made to obtain additional strength through the adding of assistants to the paper sheet, in the size press, for example.
• surface sizing it is the paper sheet that is coated.
• Surface sizing agents employed are often gelatin or derivatives of starch. Starch of this kind, added as a surface sizing agent, likewise has a strengthening effect. But it is not possible to increase strength by starch ad infinitum.
• WO 2004/027149 teaches accordingly the strengthening of the paper sheet by crosslinking of zinc borate and starch applied to the paper sheet in the size press.
• EP 2 432 934 teaches improving the strength of paper and card by spraying zirconium carbonate onto a paper sheet made from paper fibers and polyvinyl alcohol fibers, and then drying the coated sheet.
• a disadvantage of all of these crosslinking agents is that the process of crosslinking begins in the mixture itself and produces only a limited strengthening effect.
• An object of the present invention was to provide a surface coating composition which crosslinks only on the fiber and produces high strength in the paper.
• Paper stock also known as pulp furnish
• pulp furnish refers hereinafter to a mixture of water and fibrous material and, depending on the stage in the papermaking process, may further comprise filler and also paper auxiliaries.
• Dry paper stock is to be understood as meaning the overall paper stock composed of fibrous material and also, optionally, filler and, optionally, paper auxiliaries, without water (paper stock solids).
• the term for the shaped body consisting of fibrous material alters with the mass per unit area, also referred to in the jargon as grammage.
• paper is to comprehend a mass per unit area of 7 g/m 2 to 225 g/m 2 , and board a mass per unit area of 225 g/m 2 and above.
• the surface coating composition comprises a zirconium carbonate compound.
• This zirconium carbonate compound is, for example, ammonium zirconium carbonate or potassium zirconium carbonate. These are anionic, inorganic, hydroxylated zirconium compounds, and are available as water-based solutions and are typically employed for paper coatings, colored coating slips, and liquid-ink formulations.
• Starch in this context is to be understood as any virgin, modified, or degraded starch.
• Virgin starches may consist of amylose, amylopectin, or mixtures thereof.
• Modified starches may comprise oxidized starch, starch esters, or starch ethers.
• Types of starch contemplated include virgin starches such as potato starch, wheat starch, corn starch, rice starch, or tapioca starch, preferably potato starch.
• Chemically modified starches may also be used, such as hydroxyethyl or hydroxypropyl starches, or else starches which contain anionic groups, such as phosphate starch, or else cationized starches containing quaternary ammonium groups, preference being given to a degree of substitution DS of 0.01 to 0.2. This degree of substitution DS indicates the number of cationic groups present on average in the starch per glucose unit.
• amphoteric starches which contain not only quaternary ammonium groups but also anionic groups such as carboxylate and/or phosphate groups, and which may optionally also have undergone chemical modification, having for example been hydroxyalkylated or alkyl-esterified.
• the starches may be used individually or else in any desired mixtures with one another.
• the average molar masses M w of a degraded starch are situated, for example, in the range from 0.4 million to 8 million daltons, preferably in the range from 0.5 to 3 million daltons, more preferably in the range from 0.6 to 2 million daltons.
• Degradation may take place thermally, which normally refers to boiled starch. Degradation may also take place enzymatically. Lastly, degradation may also take place oxidatively. Particular preference is given to using enzymaticaly degraded starch.
• the average molar mass M w (determined by GPC) of the water-soluble synthetic polymer is preferably ⁇ 1 million Daltons, for example, 20 000 daltons to 1 million daltons, preferably 35 000 daltons to 1 million daltons.
• These polymers have example K values (determined by the method of H. Fikentscher in 5% strength aqueous sodium chloride solution at a pH of 7, a polymer concentration of 0.5 wt %, at a temperature of 25° C.) in the range from 20 to 250, preferably 30 to 80.
• the water-soluble synthetic polymer preferably contains in copolymerized form one or more monomers selected from acrylamide, vinyl alcohol, vinyl acetate, and an N-vinylcarboxamide of the formula
• R 1 , R 2 ⁇ H or C 1 to C 6 alkyl.
• the water-soluble synthetic polymers may be uncharged or charged.
• the latter carry cationic and/or anionic radicals.
• the water-soluble synthetic polymer contains in copolymerized form one or more monomers selected from acrylamide and an N-vinylcarboxamide of the formula (I), with the proviso that there is no vinyl alcohol present in copolymerized form.
• vinyl alcohol denotes a copolymerized unit [CH 2 CHOH] which is customarily obtained through the use as monomer of a vinyl ester, such as vinyl formate or vinyl acetate, for example, and through the subjection of the resulting polymer to hydrolysis, in which the copolymerized vinyl ester monomers are hydrolyzed to [CH 2 CHOH] units.
• water-soluble synthetic polymers that are suitable are the polymers of a vinylcarboxamide of the formula (I) above.
• suitable water-soluble synthetic polymers are polymers comprising vinylamine units.
• the cationic polymers comprising vinylamine units are water-soluble.
• the solubility in water under standard conditions (20° C., 1013 mbar) at a pH of 7.0 amounts for example to at least 5 wt %, preferably at least 10 wt %.
• the cationic polymers comprising vinylamine units are cationic.
• the charge density of the cationic polymers comprising vinylamine units (without a counterion) amounts to at least 0.1 meq/g and is preferably in the range from 4 to 10 meq/g.
• the cationic polymers comprising vinylamine units typically have average molecular weights M w in the range from 10 000 to 10 000 000 daltons, preferably in the range from 15 000 to 5 000 000 daltons, more preferably in the range from 20 000 to 3 000 000 daltons.
• Cationic polymers comprising vinylamine units are known: cf. the cited prior-art DE 35 06 832 A1 and DE 10 2004 056 551 A1.
• cationic polymer comprising vinylamine units
• group (a0) monomers are N-vinyl-formamide, N-vinyl-N-methylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide, N-vinyl-N-methylpropionamide, and N-vinylpropionamide.
• the group (a0) monomers may be used alone or in a mixture in the copolymerization with the monomers of the other groups.
• the copolymers may optionally contain group (c0) monomers in copolymerized form, examples being esters of ethylenically unsaturated C 3 to C 5 carboxylic acids such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, isobutyl methacrylate, methyl methacrylate, ethyl methacrylate, and vinyl esters, such as vinyl acetate or vinyl propionate, for example, or other monomers such as N-vinylpyrrolidone, N-vinylimidazole, acrylamide and/or methacrylamide.
• group (c0) monomers in copolymerized form, examples being esters of ethylenically unsaturated C 3 to C 5 carboxylic acids such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, isobutyl methacryl
• the water-soluble synthetic polymer in one preferred embodiment carries acid groups, and is therefore preferably an anionic polymer.
• the anionic charge density of the water-soluble synthetic polymer amounts to at least ⁇ 0.1 to 10 meq/g and is preferably in the range from ⁇ 0.1 to ⁇ 4 meq/g.
• the water-soluble synthetic polymer preferably comprises, more particularly consists of, one or more monomers in copolymerized form, selected from
• branched copolymers are the result.
• the proportions and reaction conditions in this case should be selected so that water-soluble polymers are still obtained.
• chain transfer agents All known such agents may be used, such as thiols, secondary alcohols, sulfites, phosphites, hypophosphites, thioacids, aldehydes, etc. (further details are found for example in EP-A 438 744, page 5, lines 7-12).
• the branched copolymers contain in copolymerized form for example
• group (a) monomers examples are N-vinylformamide, N-vinyl-N-methylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide, N-vinyl-N-methylpropionamide, and N-vinylpropionamide.
• Another suitable monomer (a) is acrylamide.
• Group (b) monomers contemplated include, in particular, monoethylenically unsaturated carboxylic acids having 3 to 8 C atoms, and also the water-soluble salts of these carboxylic acids.
• This group of monomers includes, for example, acrylic acid, methacrylic acid, dimethacrylic acid, ethacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, methylenemalonic acid, allylacetic acid, vinylacetic acid, and crotonic acid.
• Suitable group (b) monomers include monomers containing sulfo groups such as vinylsulfonic acid, acrylamido-2-methylpropanesulfonic acid, and styrenesulfonic acid, and also vinylphosphonic acid.
• the monomers of this group may be used alone or in a mixture with one another, in partly neutralized or fully neutralized form, in the copolymerization. Neutralization is done using, for example, alkali metal bases or alkaline earth metal bases, ammonia, amines and/or alkanolamines.
• Examples thereof are aqueous sodium hydroxide solution, aqueous potassium hydroxide solution, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, magnesium oxide, calcium hydroxide, calcium oxide, triethanolamine, ethanolamine, morpholine, diethylenetriamine, or tetraethylenepentamine.
• the group (b) monomers are used preferably in partly neutralized form in the copolymerization.
• the copolymers may contain in copolymerized form optionally group (c) monomers, examples being esters of ethylenically unsaturated C 3 to C 5 carboxylic acids such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, isobutyl methacrylate, methyl methacrylate, ethyl methacrylate, and vinyl esters, such as vinyl acetate or vinyl propionate, for example, or other monomers such as N-vinylpyrrolidone and N-vinylimidazole.
• group (c) monomers examples being esters of ethylenically unsaturated C 3 to C 5 carboxylic acids such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, isobutyl methacrylate, methyl methacrylate, ethyl methacrylate, and vinyl
• the copolymers may contain in copolymerized form optionally group (d) monomers, examples being methylenebisacrylamide, glycol diacrylate, glycol dimethacrylate, glycerol triacrylate, triallylamine, pentaerythritol triallyl ether, polyalkylene glycols at least doubly esterified with acrylic acid and/or methacrylic acid, or polyols such as pentaerythritol, sorbitol, or glucose. If at least one group (d) monomer is used in the copolymerization, the amounts employed are up to 2 mol %, as for example 0.001 to 1 mol %.
• group (d) monomers examples being methylenebisacrylamide, glycol diacrylate, glycol dimethacrylate, glycerol triacrylate, triallylamine, pentaerythritol triallyl ether, polyalkylene glycols at least doubly esterified with acrylic acid and/or meth
• the polymerization of the monomers takes place in a known way in the presence of radical polymerization initiators and optionally in the presence of chain transfer agents; cf. EP-B 672 212, page 4, lines 13-37 or EP-A 438 744, page 2, line 26 to page 8, line 18.
• the water-soluble synthetic polymer used is preferably an anionic copolymer obtainable by copolymerizing
• the water-soluble synthetic polymer comprises preferably
• the water-soluble synthetic polymer used is preferably a water-soluble synthetic polymer obtainable by copolymerizing
• water-soluble synthetic polymer is an anionic copolymer obtainable by copolymerizing
• water-soluble synthetic polymers are copolymers obtainable by copolymerizing a monomer mixture comprising, preferably consisting of,
• the water-soluble synthetic polymer comprises for example
• water-soluble synthetic polymer are copolymers of acrylamide with a compound selected from acrylic acid, methacrylic acid and the alkali metal or ammonium salts thereof, preferably of acrylamide with acrylic acid.
• These water-soluble synthetic polymers contain in copolymerized form generally at least 30 wt %, in a preferred form at least 40 wt %, and in a very preferred form at least 50 wt %, and also, in general, not more than 90 wt %, preferably not more than 85 wt %, and in a more preferred form not more than 80 wt % of acrylamide, based on the total weight of the monomers.
• These water-soluble synthetic polymers contain in copolymerized form generally at least 70 wt %, in a preferred form at least 60 wt %, and in a very preferred form at least 40 wt %, and also, in general, not more than 10 wt %, preferably not more than 15 wt %, and, in a particularly preferred form, not more than 20 wt % of a compound selected from acrylic acid, methacrylic acid, and the alkali metal or ammonium salts thereof, preferably acrylic acid, based on the total weight of the monomers.
• polyacrylic acids are also contemplated as water-soluble synthetic polymers.
• water-soluble polyacrylic acids which have a low molecular weight.
• Low molecular weight pertains to an average molecular weight (M w ) of less than 50 000, preferably less than 20 000, and most preferably less than 10 000, e.g., less than 5000.
• Such polyacrylic acids may contain as comonomers, in copolymerized form, other monocarboxylic acids, dicarboxylic acid monomers, and their anhydrides, and also monoethylenically unsaturated monomers which are not carboxylic acids.
• Examples of monocarboxylic acids are methacrylic acid, vinylacetic acid (3-butenoic acid), and acryloyloxypropionic acid.
• Examples of suitable dicarboxylic acid monomers are maleic acid, itaconic acid, mesaconic acid, fumaric acid, and citraconic acid.
• suitable for use are the anhydrides of the carboxylic acids, such as maleic anhydride.
• Monoethylenically unsaturated monomers which are not carboxylic acids may be present in amounts in which they are soluble in the reaction mixture and the polymer produced is soluble in water.
• the carboxyl-free monomer is less than 80% and preferably less than 50 wt % of the overall weight of all the monomers employed.
• Suitable monoethylenically unsaturated monomers which are not carboxylic acids are alkyl esters of acrylic or methacrylic acid, such as methyl, ethyl, or butyl acrylate or methyl, butyl, or isobutyl methacrylate; hydroxyalkyl esters of acrylic or methacrylic acids, such as hydroxyethyl or hydroxypropyl acrylate or methacrylate; acrylamide, methacrylamide, phosphoethyl methacrylate, allyl or methallyl alcohols, esters, and ethers; acrylonitrile, vinyl acetate, styrene, vinylsulfonic acid or salts thereof, allylsulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid or salts thereof.
• Preferred polyacrylic acids are those which are acrylic acid polymers or acrylic acid copolymers containing in copolymerized form up to 30 wt %, based on all ethylenically unsaturated monomers, of ethylenically unsaturated comonomers selected from the group consisting of methacrylic acid, maleic acid (or anhydride), vinylsulfonic acid, allylsulfonic acid, and 2-acrylamido-2-methylpropanesulfonic acid.
• the polyacrylic acid is preferably acrylic acid homopolymer.
• chain transfer agents for regulating molecular weight, are added during the radical polymerization of acrylic acid.
• Preferred chain transfer agents are hypophosphorous acid or a salt thereof, such as a sodium hypophosphite monohydrate.
• Suitable accordingly are polyacrylic acids obtainable by polymerizing monoethylenically unsaturated monocarboxylic acids and optionally further monomers, using sodium persulfate as initiator, in the presence of a hypophosphite as chain transfer agent, with an alkaline neutralizing agent being present during the polymerization in an amount sufficient to neutralize at least 20% of the acidic groups.
• suitable polyacrylic acids are those obtainable by polymerizing acrylic acid in a feed regime with peroxodisulfate as initiator in the presence of hypophosphite as chain transfer agent and in water as solvent, with water and optionally one or more ethylenically unsaturated comonomers being included in an initial charge, and with acrylic acid in an acidic, non-neutralized form, optionally one or more ethylenically unsaturated comonomers, an aqueous peroxodisulfate solution, and an aqueous hypophosphite solution being added continuously, and a base being added to the aqueous solution after the end of the acrylic acid feed, with the comonomer content not exceeding 30 wt %, based on the total monomer content.
• water-soluble synthetic polymers are amphoteric copolymers with an anionic overall charge, obtainable by copolymerizing
• amphoteric compounds accordingly contain for example
• the anionic copolymers may be hydrolyzed in the presence of acids or bases, or else enzymatically.
• the vinylamine groups formed from the vinylcarboxamide units are present in salt form.
• the hydrolysis of vinylcarboxamide copolymers is described at length in EP-A 438 744, page 8, line 20 to page 10, line 3. The statements made therein apply correspondingly to the preparation of the amphoteric polymers for inventive use.
• the aqueous surface coating composition of the invention comprises, and preferably consists to an extent of at least 95 wt % of, consisting more particularly to an extent of 100% by weight of, the inventive composition of (A), (B), and (C) and water, with the solids content of the surface coating composition being 1 to 55 wt %, preferably 5 to 20 wt %, more particularly 10 to 15 wt %.
• the aqueous surface coating composition of the invention preferably comprises
• the surface coating composition of the invention is applied to base paper.
• the amount of coating composition is applied with a coatweight of preferably 0.1 to 10 g/m 2 .
• the surface coating composition is produced by mixing of the individual components.
• the boiled starch is introduced first and the water-soluble synthetic polymer is mixed in, followed by the zirconium carbonate compound.
• the aqueous surface coating composition of the invention may further comprise a surface sizing agent based on an aqueous dispersion.
• the aqueous dispersions may possess anionic or cationic charge and they have a particle size of between 50 and 500 nm.
• Suitable dispersions are those obtainable by copolymerizing ethylenically unsaturated monomers, especially acrylonitrile and (meth)acrylates, and also, optionally, up to 10 wt % of further monomers such as styrene, by means of radically initiated emulsion polymerization in the presence of degraded starch. It is possible here for chain transfer agents to be used.
• Aqueous dispersions of this kind are described in EP 0 273 770, EP 0 257 412, WO 99/42490, WO 2002/14393, WO 2007/000419, WO 2007/000420, and WO 2011/039185, the disclosure content of which is expressly referenced.
• the aqueous surface coating composition of the invention preferably has a viscosity in the range from 1 to 200 mPa ⁇ s (12% solids content and Brookfield spindle 2 at 100 rpm at which solids content (Brookfield LV viscosity, spindle 4, 6 rpm, RT).
• the surface coating composition of the invention is suitable for coating base paper.
• the paper obtained accordingly is distinguished by high strengths.
• the surface coating compositions of the invention may be processed by all of the methods suitable in a surface sizing context. Application with the surface coating composition of the invention takes place in a film and/or size press or by a contactless application technique with a spraying bar or curtain coating process. Coating may be accomplished by means of a doctor blade or a nozzle.
• the film press and/or size press is preferably arranged inline in the paper machine. Generally it is incubated into the drying unit. At the time of application, the paper sheet preferably has a water content of ⁇ 60 wt %.
• the surface coating composition is normally added to the size press liquor in an amount of 0.05 to 3 wt %, based on solids, guided by the desired degree of sizing of the papers to be furnished.
• the present invention relates further to a method for producing paper and board, comprising the steps of
• Fibrous material used in accordance with the invention may comprise virgin and/or recovered fibers. Any softwood or hardwood fiber typically used in the paper industry may be employed, examples being unbleached chemical pulp, and also fibrous materials from any annual plants.
• Mechanical pulp includes, for example, groundwood, thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), pressure groundwood, semichemical pulp, high-yield pulp, and refiner mechanical pulp (RMP). Sulfate, sulfite, and soda chemical pulps are contemplated, for example.
• Suitable annual plants for producing fibrous materials include, for example, rice, wheat, sugarcane, and kenaf.
• the pulp furnishes are preferably produced using waste paper, which is used either alone or in a mixture with other fibrous materials.
• a preferred method for producing paper and board comprising the steps of
• fibrous material having a freeness of 20 to 50 SR In the case of waste paper it is possible to use a fibrous material having a freeness of 20 to 50 SR. In general a fibrous material with a freeness of about 40 SR is used, which is ground during the production of the pulp furnish. Preference is given to using fibrous material having a freeness of ⁇ 40 SR.
• the method of the invention serves preferably for producing filler-containing paper.
• the filler content of the paper is generally 1-20 wt %, preferably 5 to 20 wt %, more particularly 10-15 wt %, based on dry total paper stock or on paper stock.
• Filler here, as is usual in papermaking, means inorganic pigment.
• customary paper auxiliaries are sizing agents, wet strength agents, cationic or anionic retention agents based on synthetic polymers, and also dual systems, dewatering agents, optical brighteners, defoamers, biocides, and paper dyes. These conventional paper additives may be used in the customary amounts.
• Stock sizing agents include alkylketene dimers (AKDs), alkenylsuccinic anhydrides (ASAs), and rosin size.
• Wet strength agents are synthetic dry strengtheners such as polyvinylamine, or natural dry strengtheners such as starch.
• Retention aids suitable include, for example, anionic microparticles (colloidal silica, bentonite), anionic polyacrylamides, cationic polyacrylamides, cationic starch, cationic polyethyleneimine, or cationic polyvinylamine. Further conceivable are any desired combinations thereof, examples being dual systems consisting of a cationic polymer with an anionic microparticle or of an anionic polymer with a cationic microparticle. To achieve high filler retention, it is advisable to add such retention aids as may be added, for example, to thin stuff as well as to thick stuff.
• the coating step of the invention takes place during the drying phase.
• a drying unit upstream of the coating apparatus preferably a size press.
• the present specification relates further to the paper coated with the surface coating composition of the invention. Corrugated boards produced using this paper exhibit enhanced strength properties.
• the solids content was ascertained by temperature-conditioning a sample of the product (approximately 3 g)—that is, drying it to constant weight—in a preheated forced air drying cabinet at 120° C.
• the product obtained accordingly may be characterized as follows:
• NVF nonvolatile fraction
• K value 28.8 (determined in 5 wt % strength aqueous sodium chloride solution at a pH of 7 and a polymer concentration of 2%)
• the initial charge was then flushed with nitrogen and heated to 65° C.
• the product mixture may be characterized as follows:
• K value 54.6 (determined in formamide with a polymer concentration of 1%).
• Polymer 7 used was a polyacrylic acid having an average molecular weight (by GPC) of about 4000 g/mol and a degree of neutralization of 50.
• Merizet® 120 maize starch (from Tate & Lyle) was used, and was enzymatically degraded as follows: a 12% slurry of Merizet 120 was prepared in hot water at 65° C. under agitation in a 1000 L vessel, and 0.012% of PL 120 enzyme from Novozyme was added. After 20 minutes, 100 ml of acetic acid were metered into the starch solution to terminate the process of starch degradation. The starch solution had a viscosity of 55 mPas at 100 rpm (spindle 2).
• the aqueous starch solutions were diluted with DMSO and thereby stabilized.
• the molar mass distribution was determined by GPC-MALLS (gel chromatography with multiangle laser light scattering).
• the GPC-MALLS consists of a Waters 515 pump module, devolatilizer, Waters 717 Autosampler, GPC column heating (Jet Stream).
• the MALLS detector is a Dawn-Heleos (Wyatt Technology, Santa Barbara, USA) equipped with a K5 flow cell and a He—Ne laser m from 10 to 658 nm and equipped with 16 detectors with an angle of 15 to 162° .
• the following GPC columns were used in series: Suprema S 30000, S 1000, and S 10 (PSS, Mainz, Germany).
• the samples were eluted with a DMSO-containing 0.09 M NaNO 3 solution with a flow rate of 0.5 ml/min and a temperature of 70° C. in the GPC columns.
• ASTRA 5.3.0.18 was used for software analysis.
• the molar mass distribution was determined by means of GPC-UV (gel chromatography with UV and fluorescence detector).
• the GPC consists of a Waters 515 pump module, devolatilizer, Waters 717 Autosampler, GPC column heating (Jet Stream).
• the UV detector is an Agilent (DRI 1200 UV) and the equipment also includes a fluorescence detector from Agilent (1200 VWD-260 nm).
• the following GPC columns were used in series: TSKgel GMPWXL. The samples were eluted with a 0.01 M NaN 3 solution with a flow rate of 0.8 ml/min and a temperature of 35° C. in the GPC columns. Prior to injection, the polymer solutions were filtered through a 0.2 micrometer Millipore filter. The concentration of the polymer solution was 1.5%.
• Bacote 20® (from Zirconium Chemicals) is an alkaline solution of ammonium zirconium carbonate (Zirconate (2),bis[carbonato(2)-0]dihydroxydiammonium) with a solids content of 20%.
• surface coating compositions were produced.
• the starch solution was introduced first, and the polymer solution and Bacote 20 were metered in.
• the constitution of the surface coating composition was selected so as to achieve the amounts indicated in the table in parts by weight of starch (solids), parts by weight of polymer (solids), and parts by weight of Bacote 20.
• Each of the compositions was made up with water so as to give a solids content of 12 wt %. 2 parts by weight of Bacote 20 were used in each case, corresponding after conversion to 0.4 part by weight of ammonium zirconium carbonate.
• the base paper used was composed 100% of waste paper (mixture of the following grades: 1.02, 1.04, 4.01) with a grammage of 100 g/m2, possessing no surface starch.
• the base paper was coated in the formulations described in table 1 using a film press at 800 m/min on an experimental coater unit with IR dryers.
• the coatweights were determined gravimetrically. The coatweight reported is based on the dried amount of coating after departure from the IR dryer.
• the strength of the example papers was then investigated. Coating took place with different amounts of surface coating composition.

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• 2015
  • 2015-06-23 EP EP15731313.1A patent/EP3164543A1/fr not_active Withdrawn
  • 2015-06-23 CN CN201580035938.XA patent/CN106661843A/zh active Pending
  • 2015-06-23 US US15/322,367 patent/US20180209099A1/en not_active Abandoned
  • 2015-06-23 KR KR1020177002969A patent/KR20170026594A/ko unknown
  • 2015-06-23 WO PCT/EP2015/064133 patent/WO2016001016A1/fr active Application Filing

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