Method for preparing an aqueous polymer dispersion

Abstract

The invention relates to a method for preparing an aqueous polymer dispersion by radically initiated aqueous emulsion polymerisation of a monomer composition containing 50 to 99.9 wt.% of at least one C1- to C10-alkyl(meth)acrylate and / or a vinyl aromatic compound (class I), or 50 to 99.9 wt.% of at least one vinyl aromatic compound and a conjugated aliphatic diene (class II), or 50 to 99.9 wt.% of vinyl acetate, vinyl propionate, vinyl esters of versatic acid, vinyl esters of long-chain fatty acids and / or ethylene (class III), in each case in relation to the total monomers, wherein the dispersion obtained thereby is polymerised in the presence of an oligosaccharide having a mean number of 1.5 to 10 ß-1,4-glycosidically linked glucopyranose units, and use thereof as a binder, adhesive or sizing agent for fibres, for the production of coatings or for the production of a paper coating material.

Description

Process for the preparation of an aqueous polymer dispersion The invention relates to a process for the preparation of an aqueous polymer dispersion by radically initiated aqueous emulsion polymerization of a monomer composition containing 50 to 99.9 wt.% of at least one vinyl aromatic compound and / or a C1 to C10 alkyl (meth)acrylate, or 50 to 99.9 wt.% of at least one vinyl aromatic compound and one conjugated aliphatic Tuesday, or 50 to 99.9 wt.% vinyl acetate, vinyl propionate, vinyl esters of versatic acid, vinyl esters of long-chain fatty acids and / or ethylene, in each case based on the total monomers, the aqueous polymer dispersions prepared by the process and their use as binders for Adhesives, sizing agents, fibers, coating agents and paper coating slips. Binders for paper coating slips based on copolymers of vinyl aromatic compounds and aliphatic dienes are selected for a wide variety of paper applications. The continuous increase in paper machine running speeds places ever-increasing demands on the rheology of the coating slip. In addition to the pigments, the binder plays a decisive role in the rheology of the coating slip. A prerequisite for modern dispersion binders for paper coating is a high solids content with moderate viscosity and high running speeds. EP-A 0 536 597 discloses aqueous polymer dispersions which are obtainable by radical emulsion polymerization of unsaturated monomers in the presence of at least one starch degradation product having a weight-average molecular weight M wfrom 2500 to 25000. As unsaturated monomers, for example, monomer mixtures are used which contain 50 to 100% by weight of esters of acrylic acid and / or methacrylic acid with alcohols having 1 to 12 C atoms and / or styrene or 70 to 100% by weight of styrene and / or butadiene. WO 2011 / 157679 teaches the preparation of polymer dispersions by radical emulsion polymerization of styrene, acrylates and acrylic acid in the presence of a seed latex and a degraded starch such as maltodextrin or a glucose syrup, and their use as binders for paper coating slips. Both degraded starch and glucose syrup are based on raw materials that also serve as the basis for food products. Since competition with food products is to be avoided, the underlying task was to find alternative polymerization processes that would lead to aqueous polymer dispersions with good binding strength and good mechanical properties. The object is achieved according to the invention by a process for producing an aqueous polymer dispersion by radically initiated aqueous emulsion polymerization of a monomer composition containing 50 to 99.9 wt.% of at least one Ci- to C-alkyl-(meth)acrylate and / or one vinylaromatic compound (Class I), or 50 to 99.9 wt.% of at least one vinyl aromatic compound and one conjugated aliphatic diene (Class II), or 50 to 99.9% by weight of vinyl acetate, vinyl propionate, vinyl esters of versatic acid, vinyl esters of long-chain fatty acids and / or ethylene (class III), each based on the total monomers, by polymerizing in the presence of an oligosaccharide having an average number of 1.5 to 10 ß-1.4-glycosidically linked glucopyranose units. The present invention further relates to the dispersion obtained by the process according to the invention, as well as to its use as a binder, adhesive, sizing agent for fibers, for producing coatings or for producing a paper coating slip. In the following, compounds derived from acrylic acid and methacrylic acid are sometimes abbreviated by inserting the syllable "(meth)" into the compound derived from acrylic acid. The total amount of monomer is the total amount of all monomers used in the polymerization, which add up to 100% by weight. Where the solids content of the aqueous dispersion is mentioned in wt%, it is based on the weight of the aqueous dispersion. The glucopyranose unit is understood below to mean the glucopyranose residue that is glycosidically linked via both its 1-hydroxyl group and the 4-hydroxyl group, or has a glycosidic linkage via the 1-hydroxyl group at the beginning of the chain and via the 4-hydroxyl group at the end of the chain. The term "ß-1,4-glycosidically linked glucopyranose" corresponds to the equally common prefix "cello." Cellobiose thus means two ß-1,4-glycosidically linked glucopyranose units, cellotriose stands for three, cellotetraose for four, cellopentaose for five, and cellohexaose for six correspondingly linked units. According to the invention, polymerization is carried out in the presence of an oligosaccharide which is composed essentially of β-1,4-glycosidically linked glucopyranose units. "Constructed essentially" means that at least 90% by weight, preferably at least 95% by weight, in particular at least 99% by weight of the oligosaccharide comprises β-1,4-glycosidically linked glucopyranose units. Due to the manufacturing process, the oligosaccharides used are often combinations of several oligosaccharides, resulting in the average number of glucopyranose units. According to the invention, they have an average number of 1.5 to 10, preferably 2 to 6, especially 4 to 5 glucopyranose units. This number is also referred to in the specialist literature as the degree of polymerization (DP). For cellobiose, DP = 2, for cellotriose, DP = 3, etc. Suitable oligosaccharides include cellulose degradation products, often referred to as cellodextrins. Cellulose sources include plant fibers from wood, bamboo, cotton, kenaf, wheat, Rice plants and ramie. The fibers are usually mechanically processed as bagasse, pulp, or other fibers from the papermaking process, such as fines. The production of corresponding oligosaccharides is well known and can be carried out in an aqueous environment i) enzymatically, ii) acid-catalytically, or iii) thermally ("Synthesis of cello-oligosaccharides by depolymerization of cellulose: A review", Pengru Chen, Abhijit Shrotri, Atsushi Fukuoka, Applied Catalysis A, General 621 (2021)). Cellulose is preferably degraded by enzymatic hydrolysis. The enzymatic hydrolysis of cellulose is carried out by cellulases. Cellulase sources include microorganisms such as bacteria of the classes Trichoderma, Acremonium, Aspergillus, Bacillus, Pseudomonas, Penicillium, Aeromonus, Irpex, Sporotrichum, Humicola, and Cellovibrio, as described in "Cellulase" (published by Kodansha Scientific).

[1987] ) and "Encyclopedia of cellulose" (published by Asakura Publishing Co., Ltd.

[2000] ). According to a likewise preferred embodiment, the oligosaccharides are produced by acid-catalytic hydrolysis of cellulose. In the acid-catalytic degradation of cellulose, hydrolysis via phosphoric acid is preferred. The oligosaccharides obtained thereby are also the subject of the invention. The present invention also relates to a process for the production of oligosaccharides having an average number of 1.5 to 10 β-1,4-glycosidically linked glucopyranose units by acid-catalytically degrading cellulose in phosphoric acid. This is followed by the isolation and enrichment of the oligosaccharides having a DP <8, preferably <6, in particular <4. Such separation processes are known and are based on the different dissolution and crystallization behavior of the individual oligosaccharides in water and in water-miscible solvents (e.g., acetone or tetrahydrofuran).Acid-catalytically degraded cellulose is described, for example, by Tim Liebert, Marit Seifert and Thomas Heinze in Macromolecular symposia, 2008, 262, pages 140-149, Wiley. Oligosaccharides, often referred to as cellodextrins, are generally known from the literature and commercially available. For example, cellobiose from Savanna Ingredients GmbH. According to a particularly preferred embodiment, polymerization is carried out in the presence of cellobiose (D-glucosyl-ß-(1—>4)-D-glucopyranose) as an oligosaccharide. Cellobiose is known and can be produced biotechnologically, for example, by enzymatic hydrolysis of cellulose or by enzymatic conversion of sucrose. Polymerization is preferably carried out in the presence of an oligosaccharide whose cellobiose content is >90 wt.%, preferably >95 wt.%, in particular >99 wt.%. Cellobiose is preferably selected as the oligosaccharide. A process is preferred in which polymerization is carried out in the presence of 5 to 100% by weight, preferably 5 to 50% by weight, of oligosaccharide based on total monomer. According to the invention, a monomer composition containing 50 to 99.9 wt.% of at least one Ci- to C-alkyl-(meth)acrylate and / or one vinylaromatic compound (Class I), or 50 to 99.9 wt.% of at least one vinyl aromatic compound and one conjugated aliphatic diene (Class II), or 50 to 99.9 wt.% vinyl acetate, vinyl propionate, vinyl esters of versatic acid, vinyl esters of long-chain fatty acids and / or ethylene (class III), each based on total monomer, polymerized. Monomer compositions of classes I and II are preferred. A monomer composition of (a) 19.9 to 80 wt.% of at least one vinyl aromatic compound, (b) 19.9 to 80 wt.% of at least one conjugated aliphatic diene and / or C1 to C10 alkyl (meth)acrylate, (c) 0.1 to 10 wt.% of at least one ethylenically unsaturated acid, (d) 0 to 20 wt.% of one or more ethylenically unsaturated monomers which differ from the monomers (a), (b) and (c), in each case based on the total monomers, polymerized in the presence of an oligosaccharide having an average number of 1.5 to 10, preferably 2 to 6, ß-1,4-glycosidically linked glucopyranose units. Particularly preferred is a monomer composition of (a) 19.9 to 80 wt.% of at least one vinyl aromatic compound, (b) 19.9 to 80 wt.% of at least one conjugated aliphatic diene and / or C1 to C10 alkyl (meth)acrylate, (c) 0.1 to 10 wt.% of at least one ethylenically unsaturated acid, (d) 0 to 20 wt.% of one or more ethylenically unsaturated monomers other than monomers (a), (b) and (c), in each case based on the total monomers, polymerized in the presence of an oligosaccharide having an average number of 1.8 to 2.2 ß-1,4-glycosidically linked glucopyranose units, in particular cellobiose. According to a further preferred embodiment, a monomer composition of (b) 50 to 99.9 wt.% of at least one C1 to C10 alkyl (meth)acrylate, (c) 0.1 to 10 wt.% of at least one ethylenically unsaturated acid, (d) 0 to 40 wt.% of one or more ethylenically unsaturated monomers other than monomers (a), (b) and (c), based in each case on the total monomers, polymerized in the presence of an oligosaccharide having an average number of 1.8 to 2.2 ß-1,4-glycosidically linked glucopyranose units, in particular cellobiose. Vinylaromatic compounds are used as monomers (a) in an amount of 19.9 to 80 wt. %, preferably 25 to 70 wt. %, and in particular 25 to 60 wt. %, based on 100 wt. % monomers. Examples of vinylaromatic compounds are styrene, o-methylstyrene, and vinyltoluene. Styrene, methylstyrene, and mixtures thereof are preferred. Styrene is particularly preferred. Examples of conjugated aliphatic dienes (b) include 1,3-butadiene, isoprene, 1,3-pentadiene, 1,3-dimethylbutadiene, and cyclopentadiene. From this group of monomers, 1,3-butadiene and / or isoprene are preferred. The acrylate monomers (b) are selected from C1- to C8-alkyl acrylates and C1- to C8-alkyl methacrylates. These are esters of acrylic acid and methacrylic acid with monohydric C1- to C8-alcohols, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, pentyl acrylate, pentyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, or propylheptyl acrylate. The acrylate monomers are preferably selected from Ci- to Cs-alkyl acrylates and Ci- to Cs-alkyl methacrylates, in particular from methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, 2-octyl acrylate and mixtures thereof. If the esters are of alcohols of biological origin, it is possible to increase the "biocarbon content" of the polymer. Suitable alcohols for the acrylic acid esters include isobutanol, isopentanol, and 2-octanol. Increasing the biocarbon content in this way reduces the amount of fossil carbon and lowers the CO2 requirement in the production of the polymer dispersion. The term "biocarbon" indicates that the carbon is of biological origin and comes from a biomaterial / renewable resource. A renewable resource or biomaterial is an organic material in which the carbon comes from CO2 that was recently (by human standards) fixed from the atmosphere through photosynthesis. A biomaterial (carbon of 100% natural origin) has an isotope ratio of 14 C / 12 C greater than 10 12 , typically about 1.2x10' 12, while a fossil material has a zero ratio. In fact, the isotope 14 C in the atmosphere and then incorporated by photosynthesis over a period of a few decades. The half-life of 14 C is 5730 years. Thus, the materials resulting from photosynthesis, generally plants, necessarily have a maximum content of 14 C isotope. The determination of biomaterial or biocarbon content can be performed according to ASTM D 6866-12, Method B (ASTM D 6866-06), and ASTM D 7026 (ASTM D 7026-04). Monomers (b) are used in an amount of 19.9 to 80 wt.%, preferably 25 to 70 wt.% and in particular 25 to 60 wt.%, based on total monomer. Ethylenically unsaturated acids are used as monomers (c) in an amount of 0.1 to 10 wt.%, preferably 0.2 to 8 wt.% or 1 to 6 wt.%, based on 100 wt.% monomers. Ethylenically unsaturated acids include, for example, ethylenically unsaturated carboxylic acids, ethylenically unsaturated sulfonic acids, and vinylphosphonic acid. α,β-monoethylenically unsaturated mono- and dicarboxylic acids containing 3 to 6 carbon atoms in the molecule are preferably used as ethylenically unsaturated carboxylic acids. Examples include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, vinylacetic acid, and vinyllactic acid. Suitable ethylenically unsaturated sulfonic acids include vinylsulfonic acid, styrenesulfonic acid, acrylamidomethylpropanesulfonic acid, sulfopropyl acrylate and sulfopropyl methacrylate.The ethylenically unsaturated acids can be used in the polymerization in the form of free acids or in a form partially or completely neutralized with suitable bases. Sodium hydroxide solution, potassium hydroxide solution, or ammonia are preferably used as neutralizing agents. Optionally, further ethylenically unsaturated compounds different from those mentioned above can be used. The other monomers can be used in amounts of 0 to 20 wt.%, for example in an amount of 0.1 to 15 wt.% or 0.5 to 10 wt.% based on 100 wt.% of the monomer mixtures. Other monomers include, for example, unsaturated nitriles such as acrylonitrile and methacrylonitrile; ethylenically unsaturated carboxylic acid amides such as acrylamide, methacrylamide, N-methylolacrylamide and N-methylolmethacrylamide; N,N-dialkylaminoalkylacrylamides, N,N-dialkylaminoalkylmethacrylamide; vinyl esters of saturated C1- to C18-carboxylic acids, such as vinyl acetate; Allyl esters of saturated carboxylic acids, vinyl ethers, vinyl ketones, dialkyl esters of ethylenically unsaturated dicarboxylic acids, N-vinylpyrrolidone, N-vinylpyrrolidine, N-vinylformamide, N,N-dialkylaminoalkyl acrylates, N,N-dialkylaminoalkyl methacrylates, vinyl chloride and vinylidene chloride. The other monomers are preferably monoethylenically unsaturated. However, polyunsaturated monomers, particularly crosslinking monomers with two or more ethylenic double bonds, may also be used, e.g., alkanediol diacrylates, such as butanediol diacrylate. Preferably (a) 25 to 70 wt.% styrene and / or methylstyrene, (b) 25 to 70 wt.% of at least one Ci- to C-alkyl acrylate, (c) 1 to 10% by weight, preferably 1 to 6% by weight of at least one ethylenically unsaturated acid, preferably selected from acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, vinylacetic acid, vinyllactic acid, vinylsulfonic acid, styrenesulfonic acid, acrylamidomethyl ipropanesulfonic acid, sulfopropyl acrylate and sulfopropyl methacrylate and (d) 0 to 20% by weight of one or more ethylenically unsaturated monomers other than the monomers (a), (b) and (c), each based on total monomers. In a preferred embodiment, (a) 25 to 60 wt% styrene, (b) 25 to 60 wt.% n-butyl acrylate, (c) 1 to 10 wt.%, preferably 1 to 6 wt.% acrylic acid and (d) 0 to 20 wt.% of one or more ethylenically unsaturated monomers other than monomers (a), (b) and (c), based in each case on total monomers. Emulsion polymerization takes place in an aqueous medium. This can be, for example, completely demineralized water or a mixture of water and a miscible solvent such as methanol, ethanol, ethylene glycol, glycerin, or sugar alcohols such as sorbitol or tetrahydrofuran. Preferably, this medium is water. The total amount of aqueous medium is such that the resulting aqueous polymer dispersion has a solids content of preferably >40 wt.%, particularly preferably 50 to 60 wt.%, in particular >50 wt.%, based on the weight of the aqueous dispersion. Polymerization conditions generally refer to the amounts of radical initiator, temperatures, and pressures under which the radically initiated aqueous emulsion polymerization does not stop. The relationships between temperature and decomposition rate are well known to those skilled in the art for common polymerization initiators or can be determined in routine experiments. It is self-evident that, for the preparation of the polymer dispersion, the seeding processes, monomer feed processes with, for example, step and gradient processes as well as mixed forms which are familiar to the person skilled in the art are also to be included in the present specification. According to a preferred embodiment, the emulsion polymerization is carried out as a monomer feed process. In other words, the monomer and, if appropriate, the emulsifier are added in a continuous flow. According to one embodiment, it is possible to initially introduce a portion of 1 to 10 wt. % and initiate the polymerization therein. In the context of the process according to the invention, emulsifiers are understood to mean emulsifying aids. Those skilled in the art typically understand these to be emulsifying aids that keep both the monomer droplets and polymer particles dispersed in the aqueous phase, thus ensuring the stability of the resulting aqueous polymer dispersion. Suitable emulsifiers include the emulsifiers commonly used for free-radical aqueous emulsion polymerizations. Suitable emulsifiers are surfactants whose number-average molecular weight is usually below 2000 g / mol or preferably below 1500 g / mol. Anionic, cationic, and nonionic emulsifiers are suitable as emulsifiers. Emulsifiers whose relative molecular weights are usually lower than those of protective colloids are preferably used as surfactants. Suitable anionic emulsifiers include, for example, alkali and ammonium salts of alkyl sulfates (alkyl radical: C5-C22), of sulfuric acid half-esters of ethoxylated alkanols (EO degree: 2 to 50, alkyl radical: C12-C18) and ethoxylated alkylphenols (EO degree: 3 to 50, alkyl radical: C4-C9), of alkylsulfonic acids (alkyl radical: C12-C18), of alkylarylsulfonic acids (alkyl radical: C9-C18), and of diesters of sulfosuccinic acid with C4-C18 alkanols. Further suitable emulsifiers can be found in Houben-Weyl, Methoden der organischen Chemie, Volume XIV / 1, Makromolekulare Stoffe, Georg-Thieme-Verlag, Stuttgart, 1961, pp. 192-208). Bis(phenylsulfonic acid) ethers or their alkali or ammonium salts, which bear a C4-C24 alkyl group on one or both aromatic rings, are also suitable as anionic emulsifiers. These compounds are well known, e.g., from US-A-4,269,749, and commercially available, for example, as Dowfax® 2A1 (Dow Chemical Company). Suitable nonionic emulsifiers are araliphatic or aliphatic nonionic emulsifiers, for example ethoxylated mono-, di-, and trialkylphenols (EO degree: 3 to 50, alkyl radical: C4-C10), ethoxylates of long-chain alcohols (EO degree: 3 to 100, alkyl radical: Cs-C8) and polyethylene oxide / polypropylene oxide homo- and copolymers. These can contain the alkylene oxide units randomly distributed or polymerized in the form of blocks. EO / PO block copolymers, for example, are particularly suitable. Ethoxylates of long-chain alkanols (alkyl radical C1-C30, medium degree of ethoxylation 5 to 100) and, among these, particularly preferably those with a linear Ci2-C2o-alkyl radical and an average degree of ethoxylation of 10 to 50 as well as ethoxylated monoalkylphenols. Preferably, at least one anionic and / or at least one non-ionic emulsifier is used. The emulsifier is preferably selected from alkali and ammonium salts of Cs-C22 alkyl sulfates and of sulfuric acid half-esters of ethoxylated alkanols (EO degree: 2 to 40, alkyl radical: C12-C18) and of sulfuric acid half-esters of ethoxylated alkylphenols (EO degree: 10 to 40, alkyl radical: C4-C9), and bis(phenylsulfonic acid) ethers or their alkali or ammonium salts which carry a C4-C24 alkyl group on one or both aromatic rings. Particular preference is given to using a mixture of emulsifiers, each in the form of their alkali and ammonium salts, in particular a mixture of alkyl sulfates (alkyl radical: C8-C22) with sulfuric acid semiesters of ethoxylated alkanols (EO degree: 2 to 40, alkyl radical: C12-C18) or with sulfuric acid semiesters of ethoxylated alkylphenols (EO degree: 10 to 40, alkyl radical: C4-C9) or with 2-ethylhexyl sulfosuccinate, or a mixture of alkali and ammonium salts of alkyl sulfates with bis(phenylsulfonic acid) ether or their alkali or ammonium salts which carry a C4-C24 alkyl group on one or both aromatic rings (e.g. Dowfax 2A1 from the Dow Chemical Company). The process according to the invention uses radical initiators (also referred to as radical polymerization initiators), i.e., initiators that form radicals under the reaction conditions. These can be either peroxides or azo compounds. Redox initiator systems are also possible, of course. Inorganic peroxides and / or organic peroxides can be used as peroxides. Suitable inorganic peroxides include hydrogen peroxide and peroxodisulfates, such as the mono- or di-alkali metal or ammonium salts of peroxodisulfuric acid, for example, its mono- and disodium, potassium, or ammonium salts. Suitable organic peroxides include alkyl hydroperoxides such as tert-butyl hydroperoxide, aryl hydroperoxides such as p-menthyl or cumene hydroperoxide, and dialkyl or diaryl peroxides such as di-tert-butyl, dibenzoyl, or dicumene peroxide. Redox initiator systems are combined systems composed of at least one organic or inorganic reducing agent and at least one peroxide. The peroxides mentioned above are primarily considered as oxidizing agents for redox initiator systems.Suitable reducing agents which can be used are sulfur compounds with a low oxidation state, such as alkali sulfites, for example potassium and / or sodium sulfite, alkali hydrogen sulfites, for example potassium and / or sodium hydrogen sulfite, alkali metabisulfites, for example potassium and / or sodium metabisulfite, acetone bisulfite, formaldehyde sulfoxylates, for example potassium and / or sodium formaldehyde sulfoxylate, alkali salts, especially potassium and / or sodium salts, aliphatic sulfinic acids and alkali metal hydrogen sulfides, such as potassium and / or sodium hydrogen sulfide, salts of polyvalent metals, such as iron(II) sulfate, iron(II) ammonium sulfate, iron(II) phosphate, enediols, such as dihydroxymaleic acid, benzoin and / or ascorbic acid, and reducing saccharides, such as sorbose, glucose, fructose and / or dihydroxyacetone. Preferred radical initiators are inorganic and organic peroxides, preferably ammonium or alkali metal salts of peroxosulfates or peroxodisulfates, as well as tert-butyl, p-menthol, and cumyl hydroperoxide, particularly selected from sodium and potassium peroxodisulfate, tert-butyl hydroperoxide, and cumyl hydroperoxide. Particular preference is given to using at least one inorganic peroxide, preferably peroxodisulfate, especially sodium peroxodisulfate, and one organic peroxide, preferably alkyl hydroperoxide, especially t-butyl hydroperoxide. The polymerization is generally carried out using 0.1 to 5 wt.% of the radical initiator, preferably 0.5 to 4 wt.% of the radical initiator, preferably at least one inorganic and / or organic peroxide, based on 100 wt.% of total monomers. Initiation of the polymerization reaction is understood to mean the start of the polymerization reaction of the monomers present in the polymerization vessel through the decomposition of the radical initiator. Polymerization starts, for example, when the polymerization mixture contains monomers and inorganic peroxide and reaches a temperature in the range of > 80°C to < 95°C. For example, to start the polymerization, an aqueous mixture is first prepared containing a portion of a protective colloid and / or an emulsifier in dissolved form, a portion of monomer, and the seed latex. This mixture is heated to a temperature above the decomposition temperature of the radical initiator, and a portion of the radical initiator is added. After a few minutes, the monomers are added. Advantageously, another portion of radical initiator, preferably inorganic peroxide, is added at the same time as the monomers. As with all radical polymerization reactions, it is advantageous if the initial charging of the reaction components, the metering / polymerization and the subsequent reaction in the reaction vessel take place under an inert gas atmosphere, for example under a nitrogen or argon atmosphere. Preferred polymerization conditions are a temperature in the range of > 75°C to < 115°C, preferably > 85°C to < 110°C, in particular > 90°C to < 105°C. It is possible to carry out the polymerization in the presence of a seed latex. A seed latex is typically understood by those skilled in the art to be a polymer dispersion whose seed particles act as particle formation centers in the polymerization process. According to a preferred process variant, an aqueous polymer dispersion with a weight-average particle size D w 50 in the range of 20 to 60 nm and a ratio D w 50 / D n50 < 2. In this document, the weight-average particle diameter is defined as the weight-average D determined by the analytical ultracentrifuge method. w 50 value, and the number-average particle diameter is the number-average DN50 value determined using the same method (cf. SE Harding et al., Analytical Ultracentrifugation in Biochemistry and Polymer Science, Royal Society of Chemistry, Cambridge, Great Britain 1992, Chapter 10, Analysis of Polymer Dispersions with an Eight-Cell-AUC-Multiplexer: High Resolution Particle Size Distribution and Density Gradient Techniques, W. Mächtle, pages 147 to 175). In the context of this document, a narrow particle size distribution is understood to mean the ratio of the particle sizes determined using the Analytical Ultracentrifugation method. Ultracentrifuge determined weight-average particle diameter D w 50 and number-average particle diameter DN50 [D W50 / DN50] is less than or equal to 2.0, preferably less than or equal to 1.5 and particularly preferably less than or equal to 1.2 or less than or equal to 1.1. The production of a seed latex is known to those skilled in the art and is usually carried out in the presence of a large amount of emulsifier, resulting in small particle sizes and a narrow particle size distribution. It is generally observed that polymerizations carried out in the presence of such an exogenous seed latex—in contrast to an in-situ seed latex—are characterized by uniform particle growth. The seed latex, as the name suggests, is usually used in the form of an aqueous dispersion. The seed latex is preferably a styrene polymer and / or methyl methacrylate polymer with a glass transition temperature > 50 °C, > 60 °C, > 70 °C, > 80 °C or > 90 °C, measured according to DIN EN ISO 11357-2 (2013-09). Preferably, 0.01 to 4 wt.%, in particular 0.02 to 2 wt.% seed latex (calculated as solid) based on total monomers is used. Preferably, the polymerization is initiated in a receiver containing up to 2 wt.% aqueous dispersion of a polystyrene seed latex based on 100 wt.% total monomers, and then monomers and emulsifier are continuously added. To modify the properties of the polymers, the emulsion polymerization can optionally be carried out in the presence of at least one chain transfer agent. These are typically used to reduce or control the molecular weight of the polymers obtainable by free-radical aqueous emulsion polymerization. Radical chain transfer compounds (radical chain regulators) can be used to adjust the weight-average molecular weights of the polymers formed. Essentially, aliphatic and / or araliphatic halogen compounds are used, such as n-butyl chloride, n-butyl bromide, n-butyl iodide, methylene chloride, ethylene dichloride, chloroform, bromoform, bromotrichloromethane, dibromodichloromethane, carbon tetrachloride, carbon tetrabromide, benzyl chloride, benzyl bromide, organic thio compounds, such as primary, secondary or tertiary aliphatic thiols, such as ethanethiol, n-propanethiol, 2-propanethiol, n-butanethiol, 2-butanethiol, 2-methyl-2-propanethiol, n-pentanethiol, 2-pentanethiol, 3-pentanethiol, 2-methyl-2-butanethiol, 3-methyl-2-butanethiol, n-hexanethiol, 2-hexanethiol, 3-hexanethiol, 2-methyl-2-pentanethiol, 3-methyl-2-pentanethiol, 4-methyl-2-pentanethiol, 2-methyl-3-pentanethiol, 3-methyl-3-pentanethiol, 2-ethylbutanethiol, 2-ethyl-2-butanethiol,n-Heptanethiol and its isomeric compounds, n-Octanethiol and its isomeric compounds, n-Nonanthiol and its isomeric compounds, n-Decanethiol and its isomeric compounds, n-Undecanethiol and its isomeric compounds, n-Dodecanethiol and its isomeric compounds, n-Tridecanethiol and its isomeric compounds, substituted thiols, such as 2-Hydroxyethanethiol, aromatic thiols, such as benzenethiol, ortho-, meta-, or para-methylbenzenethiol, mercaptoalkanoic acid and its derivatives, such as 3-Mercaptopropionic acid 6-methylheptyl ester or 2-Mercaptoethanoic acid 2-ethylhexyl ester as well as all others in the Polymer Handbook 3rd edtition, 1989, J. Brandrup and EH Immergut, John Wiley & Sons, Section II, pages 133 to 141, but also aliphatic and / or aromatic aldehydes, such as acetaldehyde, propionaldehyde and / or benzaldehyde, unsaturated fatty acids, such as oleic acid, dienes with non-conjugated double bonds, such as divinylmethane,Vinylcyclohexane or, Terpinols or hydrocarbons with easily abstractable hydrogen atoms, such as toluene, are used. However, it is also possible to use mixtures of the aforementioned non-interfering radical chain regulators. If chain-transferring compounds are used in the polymerization, the amount used in each case is, for example, 0.01 to 5, preferably 0.1 to 3 wt.%, based on 100 wt.% of the monomers used in the polymerization. According to the invention, the entire amount of the radical chain regulator can be initially introduced into the aqueous reaction medium before initiating the polymerization reaction. However, it is also possible to initially introduce only a portion of the radical chain regulator into the aqueous reaction medium before initiating the polymerization reaction and then to add the entire amount or any remaining amount continuously or discontinuously as required under polymerization conditions during the radically initiated emulsion polymerization. To complete the polymerization reaction, it is usually sufficient to stir the reaction mixture at the polymerization temperature for, say, 0.5 to 3 hours after the monomer addition has been completed. Typically, a conversion of around 95% is achieved by this time. In order to further increase the conversion and thus reduce the residual monomer content, one can, for example, add additional radical initiators from the group of initiators mentioned above to the reaction mixture or extend their addition and carry out a so-called "post-polymerization", i.e. a polymerization, in order to achieve conversions of >95% up to 99%. Such a post-polymerization can be carried out at the same, lower, or higher temperature than the main polymerization. For example, in this phase, 0.1 to 1.5 wt.%, based on 100 wt.% of the monomers used in the polymerization, of inorganic peroxide, preferably sodium peroxodisulfate, is added as initiator, and the polymerization temperature is set to a temperature in the range of 80 to 120 °C. The pH value during polymerization can be, for example, 1 to 5. After polymerization at a conversion of >95%, the pH value is adjusted to a value between 6 and 9, for example. Chemical deodorization can also be performed. If traces of residual monomers still need to be removed, this can also be done chemically using the redox initiator systems mentioned above and systems such as those listed in DE-A 4435 423, DE-A 44 19 518, and DE-A 44 35422. Treatment with the redox initiator system is carried out in the temperature range of 60 to 115°C, preferably between 80 and 100°C. The redox partners can be added to the dispersion independently of one another, completely, in portions, or continuously over a period of 10 minutes to 4 hours. To improve the post-polymerization effect of the redox initiator systems, soluble salts of metals of varying valence, such as iron, copper, or vanadium salts, can also be added to the dispersion. Complexing agents are also frequently added to keep the metal salts in solution under the reaction conditions. Following the polymerization reaction (main polymerization + post-polymerization) and, if necessary, chemical deodorization, it may be necessary to render the aqueous polymer dispersions largely free of odor carriers, such as residual monomers and other organic volatile components, a process also referred to as physical deodorization. This can be achieved in a conventional manner by distillative removal (particularly via steam distillation) or by stripping with an inert gas. The process according to the invention is an advantageous manufacturing process for aqueous dispersions because it is not based on starch derivatives and is therefore not "food-based." Furthermore, it has a much broader raw material base and is therefore more universally applicable. The present invention also relates to the dispersions obtainable by the process according to the invention. These preferably have a solids content of >45 wt.%. Their Brookfield viscosity is preferably <1000 mPas at 100 rpm, measured with spindle 3 at 23°C. These are characterized by being virtually coagulum-free aqueous dispersions. The amount of coagulum is in the ppm range and is preferably less than 2000 ppm, especially less than 1000 ppm. The aqueous polymer dispersions of the invention are used as binders, adhesives, fiber sizing agents, for the production of coatings, or for the production of paper coating slips. The aqueous polymer dispersions of the invention are suitable both for sizing textile fibers and for sizing mineral fibers, especially glass fibers. Due to their good adhesive strength, particularly when using comonomers that result in a low glass transition temperature of the copolymer (e.g., less than 20°C), they can also be used as adhesives, for example, for the production of laminates and for the production of coatings such as barrier coatings. The aqueous polymer dispersions of the invention are preferably used as binders in paper coating slips. The invention therefore also relates to a paper coating slip having a solids content in the range of 50 to 85 wt.% based on the paper coating slip, containing (i) inorganic pigment and (ii) an aqueous polymer dispersion as described above and obtainable by the process according to the invention (iii) and, where appropriate, other excipients. In addition to water, paper coating slips generally contain pigments, binders, and auxiliaries for adjusting the required rheological properties, such as thickeners. The pigments are usually dispersed in water. The paper coating slip contains pigments in an amount of preferably at least 80 wt.%, e.g., 80 to 95 wt.% or 80 to 90 wt.%, based on the solids content. White pigments are particularly suitable. Suitable pigments include metal salt pigments such as calcium sulfate, calcium aluminate sulfate, barium sulfate, magnesium carbonate, and calcium carbonate, of which carbonate pigments, especially calcium carbonate, are preferred. The calcium carbonate can be ground calcium carbonate (GCC, natural ground calcium carbonate), precipitated calcium carbonate (PCC, precipitated calcium carbonate), lime, or chalk. Suitable calcium carbonate pigments are available, for example, as Covercarb® 60, Hydrocarb® 60 or Hydrocarb® 90 ME. Other suitable pigments include silica, aluminum oxide, aluminum hydrate, silicates, titanium dioxide, zinc oxide, kaolin, alumina, talc, or silicon dioxide. Suitable additional pigments are available, for example, as Capim® MP 50 (Clay), Hydragloss® 90 (Clay), or Talcum 010. The paper coating slip contains the polymer dispersion prepared according to the invention as the sole binder or in combination with another binder. The most important functions of binders in paper coating slips are to bond the pigments to the paper and the pigments to each other, and to partially fill voids between pigment particles. For example, 1 to 50 wt.%, preferably 1 to 25 wt.% or 5 to 20 wt.% of the polymer according to the invention (solid / solid) is used per 100 wt.% of pigments. Preference is given to a paper coating slip which contains the polymers of the aqueous polymer dispersion in an amount of 5 to 50% by weight, based on the total amount of pigments, and pigments in an amount of 80 to 95% by weight, based on the solids content, and an auxiliary agent, and whose pigments are preferably selected from the group consisting of calcium sulfate, calcium aluminate sulfate, barium sulfate, magnesium carbonate, calcium carbonate, silicic acids, aluminum oxides, aluminum hydrate, silicates, titanium dioxide, zinc oxide, kaolin, clay, talc and silicon dioxide and whose auxiliary agent is selected from the group consisting of thickeners, further polymeric binders, co-binders, optical brighteners, fillers, flow control agents, dispersants, surfactants, lubricants, neutralizing agents, defoamers, deaerating agents, preservatives and dyes. The other synthetic binders different from the polymers prepared according to the invention are generally known and are described, for example, in D. Urban and K. Takamura, Polymer Dispersions and Their Industrial Applications, 2002, Wiley-VCH Verlag GmbH, Weinheim, Chapter 4.4.4, page 90 ff., the disclosure of which is expressly incorporated by reference. Other suitable binders include natural-based binders, in particular starch-based binders, as well as synthetic binders different from the polymers produced according to the invention, in particular emulsion polymers producible by emulsion polymerization. Starch-based binders in this context are understood to mean any native, modified, or degraded starch. Native starches can consist of amylose, amylopectin, or mixtures thereof. Modified starches can be oxidized starch, starch esters, or starch ethers. The molecular weight of the starch can be reduced by hydrolysis (degraded starch). Suitable degradation products are oligosaccharides or dextrins. Preferred starches are cereal, corn, and potato starch. Cereal and corn starch are particularly preferred, and corn starch is most preferably used. Paper coating slips according to the invention can additionally contain other auxiliaries, e.g. fillers, co-binders and thickeners for further optimizing viscosity and water retention, optical brighteners, dispersants, surfactants, lubricants (e.g. calcium stearate and waxes), neutralizing agents (e.g. NaOH or ammonium hydroxide) for pH adjustment, defoamers, deaerating agents, preservatives (e.g. biocides), flow control agents, dyes (especially soluble dyes), etc. Suitable thickeners include synthetic polymers (e.g. cross-linked polyacrylate), in particular celluloses, preferably carboxymethylcellulose. Optical brighteners include, for example, fluorescent or phosphorescent dyes, in particular stilbenes. It is preferably an aqueous paper coating slip; it already contains water, particularly due to the preparation of the components (aqueous polymer dispersions, aqueous pigment slurries); the desired viscosity can be adjusted by adding additional water. Typical solids contents of paper coating slips are in the range of 30 to 80 wt.%. The pH of the paper coating slip is preferably adjusted to values ​​of 6 to 11, especially 7 to 10. The invention also relates to paper or board coated with a paper coating slip according to the invention, and to a process for coating paper or board, wherein an aqueous polymer dispersion is prepared according to the invention; and a paper coating slip is prepared using this polymer dispersion, at least one pigment and optional further auxiliaries; and the paper coating slip is applied to at least one surface of paper or board. The paper coating slip is preferably applied to uncoated base paper or uncoated cardboard. The amount is generally 1 to 50 g, preferably 5 to 30 g (solid, i.e., without water or other solvents liquid at 21 °C, 1 bar) per square meter. Coating can be carried out using conventional application methods, e.g., size press, film press, blade coater, air brush, doctor blade, curtain coating, or spray coater. Depending on the pigment system, the aqueous dispersions of the water-soluble copolymers in paper coating slips can be used for the base coat and / or the top coat. The paper coating slips of the invention have good performance properties. They exhibit good runnability in paper coating processes and high bond strength. The coated papers and boards have good surface strength, in particular very high wet and dry pick resistance. They are readily printable using conventional printing processes, such as letterpress, gravure, offset, digital, inkjet, flexographic, newspaper, letterpress, sublimation, laser, electrophotographic, or a combination of these processes. Examples Unless the context indicates otherwise, percentages always mean percentages by weight. The stated content refers to the content in an aqueous solution or dispersion. Unless otherwise stated, solutions / dispersions by weight always refer to aqueous solutions / dispersions. When water was used in the examples, demineralized water was used. Measurement methods Determination of the viscosity of the dispersion: The viscosity of the dispersion was determined according to ASTM D2196 using a Brookfield viscometer with spindle type RV 3 at 100 rpm and a temperature of 23°C. Solids content: The solids content of the dispersions was determined using an IR moisture analyzer. This is a thermogravimetric method that combines an analytical balance with an infrared radiator. 1-2 g of the dispersions were finely distributed on a glass filter and dried to constant mass at 100°C. Constant mass is achieved when a weight loss of less than 2 mg in 45 s is achieved. The following materials were used in the examples: Emulsifier A: Sodium dodecyl benzyl sulfonate Seed latex: Polystyrene seed in the form of a 32.4 wt.% dispersion with a particle size of approximately 30 nm (determined by analytical ultracentrifuge) Initiator A: 5 wt.% solution of sodium peroxodisulfate (NaPS) Initiator B: 3 wt.% solution of tert-butyl hydroperoxide Reducing agent: 14 wt.% solution of acetone bisulfite Cellobiose manufacturer: Savanna Ingredients GmbH in food grade Lamperts Maltodextrin 19 degraded starch (Lamberts) with a DE value (dextrose equivalent) of 19 Example 1: Preparation of the oligosaccharide To synthesize the oligosaccharides, 5 g of microcrystalline cellulose with an average particle diameter of 50 μm was added to 60 mL of 85 wt% phosphoric acid and dissolved with stirring, without exceeding a temperature of 55°C during the mixing process. The mixture was then heated to 55°C for 20 hours. The mixture was poured into an excess of acetone (7-10 times) to precipitate the cellulose oligomers as the crude product. The suspension was decanted, and the liquid phase was discarded. For purification, the precipitate was dispersed in approximately 5 mL of water, centrifuged, and decanted, and the extract was collected. The precipitate was dispersed twice more with 5 mL of water, centrifuged, and decanted, and the aqueous extracts were combined. The aqueous phase (approx. 10 mL) was concentrated to 3 mL under reduced pressure at room temperature. The oligosaccharide was precipitated by adding acetone (approx. 100 mL) and separated by centrifugation and decantation. The resulting oligosaccharide (approx. 2-3 g) was washed with acetone and air-dried at room temperature. Determination of the composition of the oligosaccharide: The oligosaccharide obtained according to Example 1 was dissolved in water (concentration 0.25 to 2 mg / ml H2O) and analyzed by HPLC (Eurokat Na column from Knauer) with an attached RI detector. Ultrapure water containing 0.1 mM NaNa was used as the mobile phase. Calibration was performed using defined cellooligosaccharides from Megazyme. The following composition was determined for the oligosaccharide from Example 1: 1 wt% glucose, 5 wt% cellobiose, 15 wt% cellotriose, 20 wt% cellotetraose and 59 wt% water-soluble cellulose oligomers with 5 to 10 glucopyranose units. Production of emulsion polymers The following quantities in pphm (parts per hundred monomer) are based on 100 parts by weight (= 100% by weight) of total monomer. Example 2 Emulsion polymerization of styrene / n-butyl acrylate / acrylic acid / cello-oligosaccharide Template: 223 g water 39 g of cello-oligosaccharide (8 wt% water content) from Example 1 (20 pphm) 7.22 g of a 32.4 wt.% aqueous polystyrene latex dispersion (average particle size = 30 nm; 1.3 pphm) Encore 1 : 10.8 g of an aqueous 5 wt.% solution of sodium peroxodisulfate (0.3 pphm) Inlet l : 6.6 g acrylic acid (3.5 pphm) 1.95 g 97 wt% sodium dodecylbenzylsulfonate (1 pphm) 78 g styrene (41.5 pphm) 104 g n-butyl acrylate (55 pphm) 43 g water Inlet 2: 29.16 g of an aqueous 5 wt.% solution of sodium peroxodisulfate (0.81 pphm) Encore 2: 9.6 g of a 15 wt% solution of sodium hydroxide Inlet 3: 7.8 g 3% w / w solution of tert-butyl hydroperoxide (0.13 pphm) Inlet 4: 9.05 g of a 14.10 wt.% solution of acetone bisulfite (0.7 pphm) Encore 3: 3.6 g of a 15 wt% solution of sodium hydroxide The components of the initial mixture were placed in a 2 L glass reactor, which had previously been purged with nitrogen, and mixed. The initial mixture was heated to 93°C. When 80°C was reached, the initiator (Add-on 1) was slowly added, and polymerization was initiated. Feeds 1 and 2 were added immediately thereafter. Feed 1 was added over a period of 3 hours, while feed 2 was added over a period of 3.5 hours. Feed 1 was fed into the reactor in the form of an emulsion. After the end of feed 2, the mixture was stirred for a further 30 minutes at 93°C. Feed 2 was then added, and the polymerization mixture was stirred for a further 30 minutes. Feeds 3 and 4 were then added in parallel over a period of 1 hour at 80°C. After the reaction mixture had cooled to room temperature, feed 3 was added. The solids content of the dispersion was 38 wt%. The polymer dispersion was examined using an analytical ultracentrifuge: The obtained dispersion was monodisperse and had an average particle size of 169 nm, with a mass fraction of particles of 10% not smaller than 142 nm and a mass fraction of particles of 90% not larger than 192 nm. Example 3 Emulsion polymerization of styrene / n-butyl acrylate / acrylic acid / cellobiose Example 3 was carried out analogously to Example 2, with the difference that 20 pphm cellobiose powder was used in the initial charge. The solids content of the dispersion was 39 wt%. The polymer dispersion was examined using an analytical ultracentrifuge: The obtained dispersion was monodisperse and had an average particle size of 118 nm, with a mass fraction of particles of 10% not smaller than 112 nm and a mass fraction of particles of 90% not larger than 126 nm. Example 4 (not according to the invention) Emulsion polymerization of styrene / n-butyl acrylate / acrylic acid Example 4 was carried out analogously to Example 3, with the difference that 20 pphm maltodextrin powder, Lamperts Maltodextrin 19, was used in the initial batch. The solids content of the dispersion was 38 wt%. The polymer dispersion was examined using an analytical ultracentrifuge: The obtained dispersion was monodisperse and had an average particle size of 112 nm, with a mass fraction of particles of 10% not smaller than 92 nm and a mass fraction of particles of 90% not larger than 141 nm. Example 5 - Styrene / Butadiene / Acrylic Acid / Cellobiose Template: 1637.41 g demineralized water (113 pphm) 295.92 g of a 98 wt.% cellobiose powder (20 pphm) 7.25 g of a 2.0 wt% solution of Trilon BX (0.01 pphm) 2.59 g of a 28 wt.% solution of Texapon NSO P (0.05 pphm) Encore 1 : 103.57 g of a 7% w / w solution of sodium peroxodisulfate (initiator) (0.5 pphm) Inlet l : 2.59 g of a 28 wt.% solution of Texapon NSO P (0.05 pphm) 433.0 g water (30 pphm) Inlet 2: 58.0 g acrylic acid (4.0 pphm) 826.5 g styrene (57 pphm) 13.05 g tert-dodecyl mercaptan (0.9 pphm) Inlet 3: 565.5 g 1,3-butadlene (39 pphm) Inlet 4: 103.57 g of a 7 wt.% solution of sodium peroxodisulfate (0.5 pphm) Inlet 5: 29.0 g of a 10 wt.% solution of tert-butyl hydroperoxide (0.2 pphm) Inlet 6: 35.0 g of a 14.10 wt.% solution of acetone bisulfite (0.34 pphm) Encore 2: 61.0 g of a 15 wt% solution of sodium hydroxide (0.63 pphm) The components of the initial charge were placed in a 6 l pressure reactor and mixed. The reactor was purged with nitrogen. The initial charge was heated to 95°C. When 90°C was reached, the initiator (Add-on 1) was slowly added and feeds 1, 2, 3 and 4 were started and carried out over a period of 2.5 h. After feeds 1, 2, 3 and 4 had ended, the mixture was kept at 95°C with stirring for 30 minutes to complete the polymerization. Subsequently, 117 g of deionized water were added. The reaction mixture was then cooled to 90°C. Feeds 5 and 6 were then fed in parallel over 1.5 h. The reactor was cooled to room temperature and feed 2 was added to the reactor. The solids content of the dispersion was 38 wt.%. The polymer dispersion was examined using an analytical ultracentrifuge: The obtained dispersion was monodisperse and had an average particle size of 173 nm, with a mass fraction of particles of 10% not smaller than 164 nm and a mass fraction of particles of 90% not larger than 187 nm. Example 6 - Styrene / Butadiene / Acrylic Acid / Maltodextrin, (not according to the invention) Example 6 was carried out analogously to Example 5, with the difference that 20 pphm maltodextrin (Lamperts Maltodextrin 19) was used in the initial batch. The solids content of the dispersion was 38.7 wt%. The polymer dispersion was examined using an analytical ultracentrifuge: The obtained dispersion was monodisperse and had an average particle size of 97 nm, with a mass fraction of particles of 10% not smaller than 74 nm and a mass fraction of particles of 90% not larger than 119 nm. Example 7 - Styrene / Acrylate / Acrylic Acid / Maltose (not according to the invention) Example 7 was carried out analogously to Example 3, with the difference that 20 pphm maltose was used in the initial mixture. The solids content of the dispersion was 38.7 wt%. The polymer dispersion was examined using an analytical ultracentrifuge: The obtained dispersion was monodisperse and had an average particle size of 109 nm, with a mass fraction of particles of 10% not smaller than 103 nm and a mass fraction of particles of 90% not larger than 142 nm. Example 8 (not according to the invention) Emulsion polymerization of styrene / n-butyl acrylate / acrylic acid / glucose Example 8 was carried out analogously to Example 2, with the difference that 20 pphm glucose was used in the initial charge instead of the polysaccharide. The solids content of the dispersion was 38.9 wt%. The polymer dispersion was examined using an analytical ultracentrifuge: The obtained dispersion was monodisperse and had an average particle size of 114 nm, with a mass fraction of particles of 10% not smaller than 109 nm and a mass fraction of particles of 90% not larger than 126 nm. Example 9 Glucose syrup (not according to the invention) Emulsion polymerization of styrene / n-butyl acrylate / acrylic acid / glucose syrup Example 9 was carried out analogously to Example 2, except that 20 pphm dry glucose (anhydrous glucose syrup, DE = 28-32) was used instead of the cellooligosaccharide. The dry glucose used had a DE significantly below LP 19 (Example 4) and a higher proportion of glucose, maltose, and maltotriose. The solids content of the dispersion was 39.3 wt%. The polymer dispersion was examined using an analytical ultracentrifuge: The obtained dispersion was monodisperse and had an average particle size of 125 nm, with a mass fraction of 10% of the particles not smaller than 119 nm and a mass fraction of 90% of the particles not larger than 134 nm. Table 1: Summary of examples *Prepared in Example 1 ne: not according to the invention Characterization of the mechanical properties of the polymer dispersion The storage modulus G' (deformation) was measured using dynamic mechanical thermal analysis (DMTA). The G' value is considered a measure of the deformation energy stored in the sample material during the shear process. Substances that completely store deformation energy exhibit reversible deformation behavior; they remain unchanged after a loading / unloading cycle. G' is a measure of the elastic behavior of a polymer film. The dynamic mechanical properties of the films were analyzed using a torsional rheometer. Films were prepared from the polymer dispersions and dried. The films were dried in a drying cabinet at 30°C for at least 4 days until they appeared completely clear. The films were then tempered at 40°C for 3 hours. Before testing, the films were conditioned for at least 48 hours in a climate chamber at 23°C and 50% relative humidity. The resulting films were between 1 mm and 2 mm thick. For the measurements, 10 mm wide and 30–40 mm long strips were punched from the films. The film strips were subjected to oscillating torsional loading. The measurement parameters are listed in the following table. Measurement parameters: Application: RHEOPLUS / 32 V3.40 21004578-33024 Measuring device: MCR501 Manufacturer: Anton Paar Measuring system: SRF12-SN19150 The measurement was carried out in oscillation, isothermal at 30°C, a frequency of 0.1 Hz and a deformation of 0.01% to 20%. Results of the mechanical behavior of the polymer films In relation to a DMTA measurement, the quartile refers to a statistical value that represents the relationship between the data points in four quartiles. The first quartile (Q1) represents the value below which 25% of the data points lie, the second quartile (Q2) is the median, and the third quartile (Q3) represents the value below which 75% of the data points lie. These quartiles are used to analyze the scatter and distribution of the measured storage modulus values. The higher the storage modulus, the more deformation energy the film can store. Table 2: not according to the invention 5.0e8 = 5.0 10 8 The results show that the dispersion prepared in the presence of cellobiose (Example 3 according to the invention) has a significantly higher storage modulus than the dispersion prepared in the presence of maltose (Example 7 not according to the invention). Likewise, the storage modulus of the dispersion according to the invention of Example 2 (prepared in the presence of β-1,4-glycosidically linked glucopyranose units) is higher than that of the non-inventive dispersions of Examples 4 and 9 (prepared in the presence of α-1,4-glycosidically linked glucopyranose units). It follows that films of the polymer dispersions according to the invention are more resistant to external deformations. Production of paper coating slips: The quantities given refer to the solid content. 100% w / w calcium carbonate (Hydrocarb® 60 from Omya) 5 wt.% emulsion polymer of the respective example 0.25 wt.% rheology aid (Sterocoll® FS, BASF SE) The paper coating slip was prepared in a stirring unit into which the individual components were added one after the other. The pigment (calcium carbonate) was added in predispersed form (slurry). The other components were added in the order above. The final solids content was adjusted by adding water. Paper coating slip: Solids content = 64 wt% pH = 9 Viscosity (Brookfield RVT, spindle 4, 100 rpm): 500-1500 mPas Paper coating: A standard paper Magnostar base paper wood-free approx. 58 g / m 2The coating was applied to one side of the paper using a laboratory coating machine at a pressure of approximately 1.45 bar and a speed of 25 cm / min. The coating was dried using three 650 W heaters. The application was carried out using the blade coating method. The coating weight was 10-12 g / m² (solid). Measurement of dry pick resistance with IGT test printer (IGT dry): Strips were cut from the coated board to be tested and printed using the IGT test printer. The printing inks used were Lorilleux 3807 rouge. The test strips were passed through the press at a continuously increasing speed (maximum speed 100 cm / s). The contact pressure was 70 kN / m. A strip of paper is stretched over the circular segment. The 20 mm wide, inked print wheel is placed on the upper axle, applied to the set pressure, and the printing process begins. The printed test strip is viewed under oblique light, and the beginning of picking is marked with a line on the side of the print. The measurement used for dry picking resistance is the speed in cm / s present at this point during printing, as well as the test ink used. Table 3: Application data of the coated paper The examples show that papers coated with paper coating slips containing the dispersions according to the invention have a comparable binding strength to paper coating slips with dispersions prepared in the presence of degraded starch.

Claims

Claims 1 . Process for the preparation of an aqueous polymer dispersion by radically initiated aqueous emulsion polymerization of a monomer composition containing 50 to 99.9 wt.% of at least one vinyl aromatic compound and / or C1 to C10 alkyl (meth)acrylate, or 50 to 99.9 wt.% of at least one vinyl aromatic compound and a conjugated alkyl phatic diene, or 50 to 99.9 wt.% vinyl acetate, vinyl propionate, vinyl esters of versatic acid, vinyl esters of long-chain fatty acids and / or ethylene, each based on the total monomers, by polymerizing in the presence of an oligosaccharide having an average number of 1.5 to 10 ß-1,4-glycosidically linked glucopyranose units.

2. Process according to claim 1, characterized in that the average number of glucopyranose units is 2 to 6, in particular 4 to 5.

3. Process according to claim 1 or 2, characterized in that polymerization is carried out in the presence of an oligosaccharide obtained by acid-catalytic hydrolysis of cellulose and / or in the presence of an oligosaccharide obtained by enzymatic hydrolysis of cellulose.

4. Process according to claim 1 or 2, characterized in that polymerization is carried out in the presence of an oligosaccharide obtained by enzymatic hydrolysis of cellulose.

5. Process according to one of claims 1 to 4, characterized in that cellobiose is chosen as the oligosaccharide.

6. Process according to one of claims 1 to 5, characterized in that polymerization is carried out in the presence of 5 to 100% by weight, in particular 5 to 50% by weight, of oligosaccharide based on total monomer.

7. Process according to one of claims 1 to 6, characterized in that a monomer composition Settlement from (a) 19.9 to 80 wt.% of at least one vinyl aromatic compound, (b) 19.9 to 80 wt.% of at least one conjugated aliphatic diene and / or C1 to C10 alkyl (meth)acrylate, (c) 0.1 to 10 wt.% of at least one ethylenically unsaturated acid, (d) 0 to 20 wt.% of one or more ethylenically unsaturated monomers other than monomers (a), (b) and (c), each based on the total monomers, polymerized.

8. Process according to one of claims 1 to 7, characterized in that a monomer composition Settlement from (a) 25 to 70 wt.% styrene and / or methylstyrene, (b) 25 to 70 wt.% of at least one C1 to C10 alkyl acrylate, (c) 1 to 10 wt.% of at least one ethylenically unsaturated acid, preferably selected from acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, vinylacetic acid, vinyllactic acid, vinylsulfonic acid, styrenesulfonic acid, acrylamidomethylpropanesulfonic acid, sulfopropyl acrylate and sulfopropyl methacrylate and (d) 0 to 20 wt.% of one or more ethylenically unsaturated monomers other than monomers (a), (b) and (c), in each case based on total monomers, polymerized.

9. Process according to one of claims 1 to 8, characterized in that polymerization is carried out at a temperature in the range from > 75°C to < 115°C.

10. Aqueous polymer dispersion obtainable by radically initiated emulsion polymerization according to one of claims 1 to 9.

11. Use of the aqueous polymer dispersion according to claim 10 as a binder, adhesive, sizing agent for fibers, for the production of coatings or for the production of paper coating slips.

12. A paper coating slip having a solids content in the range from 50 to 85% by weight based on the paper coating slip, comprising (i) inorganic pigments and (ii) an aqueous polymer dispersion according to claim 10 and optionally further auxiliaries.

13. Paper coating slip according to the preceding claim, characterized in that the polymer dispersion (solid) is used in an amount of 5 to 50 wt.%, based on the total amount of pigments, and that the pigments are present in an amount of 80 to 95 wt.%, based on the total solids content, and are selected from the group consisting of calcium sulfate, calcium aluminate sulfate, barium sulfate, magnesium carbonate, calcium carbonate, silicic acids, aluminum oxides, aluminum hydrate, silicates, titanium dioxide, zinc oxide, kaolin, clay, talc and silicon dioxide and that the paper coating slip additionally contains at least one auxiliary agent selected from the group consisting of thickeners, further polymeric binders, co-binders, optical brighteners, fillers, flow control agents, dispersants, surfactants, lubricants, neutralizing agents, defoamers, deaerating agents, preservatives and dyes.

14. Paper or cardboard coated with a paper coating slip according to one of the two preceding claims.

15. A process for coating paper or board, wherein an aqueous polymer dispersion according to claim 10 is provided; and a paper coating slip is prepared using the aqueous polymer dispersion, at least one pigment, and optionally further auxiliaries; and - and the paper coating slip is applied to at least one surface of paper or board.

Images