Aqueous polymer dispersions

Description

[0001] The present invention relates to a process for the preparation of an aqueous polymer dispersion by radically initiated aqueous emulsion polymerization, which is characterized in that in an aqueous medium in the presence of at least one phosphorus group-containing dispersing agent in a first polymerization stage (polymerization stage 1) ≥ 1.0 and ≤ 3.0 wt% at least one α,β-monoethylenically unsaturated C 3 to C 6 mono- or dicarboxylic acid (monomers A1), ≥ 1.5 and ≤ 6.0 wt% at least one ethylenically unsaturated compound which has at least one phosphorus-containing group (monomers A2), ≥ 91.0 and ≤ 97.5 wt% at least one ethylenically unsaturated compound which differs from the monomers A1 and A2 (monomers A3), wherein the amounts of monomers A1 to A3 add up to 100 wt.% (total monomer amount 1), are radically polymerized to a polymer 1, and subsequently in the presence of polymer 1 in a second polymerization stage (polymerization stage 2) ≤ 0.1 wt% at least one α,β-monoethylenically unsaturated C 3 to C 6 mono- or dicarboxylic acid (monomers B1), ≤ 0.1 wt% at least one ethylenically unsaturated compound which has at least one phosphorus-containing group (monomers B2), ≥ 99.8 and ≤ 100 wt.% at least one ethylenically unsaturated compound which differs from the monomers B1 and B2 (monomers B3), wherein the amounts of monomers B1 to B3 add up to 100 wt.% (total monomer amount 2), are radically polymerized to a polymer 2, with the proviso that the type and amounts of the monomers A1 to A3 are selected such that the polymer 1 obtained therefrom has a glass transition temperature Tg 1< in the range ≥ -10 and ≤ 15 °C, the type and amounts of the monomers B1 to B3 are selected such that the polymer 2 obtained therefrom has a glass transition temperature Tg 2< which is at least 10 °C above the glass transition temperature Tg 1< [Tg 2< = Tg 1< + ≥ 10 °C], the ratio of total monomer amount 1 to total monomer amount 2 is 70 to 85 wt.% to 15 to 30 wt.%, and the amount of the at least one phosphorus group-containing dispersant is ≥ 0.5 wt.% based on the sum of total monomer amount 1 and total monomer amount 2 (total monomer amount).

[0002] The present invention further relates to the aqueous polymer dispersions obtainable by the processes and to their use in a wide variety of applications, in particular in corrosion protection coatings.

[0003] For multi-stage aqueous polymer dispersions containing phosphorus groups, the following relevant state of the art can be assumed.

[0004] EP-A 1193298 discloses aqueous polymer dispersions whose polymers contain monomers with a strong acid group in polymerized form. A strong acid group is understood to mean those which have a pKa value of <4 at 20 °C, such as sulfonic acid or phosphoric acid groups. Optionally, these polymers can also contain minor amounts of carboxylic acid monomers in polymerized form. The polymerization reaction takes place under strongly acidic conditions. Any necessary neutralization only takes place after the polymerization reaction. The resulting aqueous polymer dispersions are advantageously suitable as binders in corrosion protection formulations and coatings with high gloss requirements.

[0005] WO 2016 / 071326 teaches a process for producing an aqueous polymer dispersion in a two-stage polymerization process, wherein in the first polymerization stage, polymerization is carried out in the presence of a dispersing agent containing sulfate or sulfonate groups and in the second polymerization stage, polymerization is carried out in the presence of a dispersing agent containing phosphate or phosphonate groups.

[0006] EP 0960889 teaches an aqueous polymer dispersion obtainable by emulsion polymerization of a monomer mixture in the presence of a protective colloid composed of vinylphosphonic acid and alkyl acrylates. The resulting polymer dispersions are advantageously suitable as binders in corrosion protection formulations.

[0007] EP-A 2426155 discloses dispersions of multi-stage dispersion polymers containing phosphoric acid group-containing monomers in polymerized form, and their use in coating formulations. A characteristic feature of the preparation of the dispersion polymers is the pulsed metering of the phosphorus group-containing monomers, which should be carried out such that 75 to 100 wt. % of the phosphorus group-containing monomers are added within the period during which 10 to 50 wt. % of the total monomer quantity is added. Here, too, the polymerization reaction takes place under strongly acidic conditions. Any necessary neutralization only takes place after the polymerization reaction. The resulting polymer dispersion particles are said to be advantageously suitable for adsorption on titanium dioxide particles, so that they are used in particular in titanium dioxide-containing coating formulations.

[0008] A disadvantage of the aforementioned processes is that the technically standard stainless steel polymerization reactors are unsuitable for polymerization reactions in strongly acidic media due to extensive corrosion and / or localized pitting corrosion, thus requiring special, expensive internally coated polymerization reactors or titanium polymerization reactors. Furthermore, the resulting aqueous polymer dispersions are unstable when functional monomers are additionally used in the polymerization reaction and tend to experience increased coagulum formation or even coagulation. Furthermore, aqueous corrosion protection coatings containing the aqueous polymer dispersions obtained by the aforementioned processes as binders are not entirely satisfactory in all respects.

[0009] The object of the present invention was therefore to provide a process for producing an aqueous dispersion of phosphorus group-containing dispersion polymers, the production of which can be carried out in industrially customary polymerization reactors, wherein the resulting aqueous polymer dispersion is stable and has a low fine coagulum content and, moreover, when used in anti-corrosive coatings, has improved early water resistance, lower surface corrosion, lower rusting starting from a scratch and improved adhesion properties.

[0010] The problem was solved by the process defined at the beginning or by the aqueous polymer dispersions accessible by this process.

[0011] The implementation of radically initiated emulsion polymerizations of ethylenically unsaturated compounds (monomers) in an aqueous medium has been described many times and is therefore sufficiently known to the person skilled in the art [cf. Emulsion Polymerization in Encyclopedia of Polymer Science and Engineering, Vol. 8, pages 659 ff. (1987); DC Blackley, in High Polymer Latices, Vol. 1, pages 35 ff. (1966); H. Warson, The Applications of Synthetic Resin Emulsions, Chapter 5, pages 246 ff. (1972); D. Diederich, Chemistry in our Time 24, pages 135 to 142 (1990); Emulsion Polymerization, Interscience Publishers, New York (1965); DE-A 40 03 422 and dispersions of synthetic high polymers, F. Hölscher, Springer-Verlag, Berlin (1969)].The radically initiated aqueous emulsion polymerization is usually carried out in such a way that the monomers are dispersed in an aqueous medium, usually with the use of dispersing aids such as emulsifiers and / or protective colloids, and polymerized by means of at least one water-soluble radical polymerization initiator. Frequently, in the aqueous polymer dispersions obtained, the residual contents of unreacted monomers are reduced by chemical and / or physical methods also known to the person skilled in the art [see, for example, EP-A 771328, DE-A 19624299, DE-A 19621027, DE-A 19741184, DE-A 19741187, DE-A 19805122, DE-A 19828183, DE-A 19839199, DE-A 19840586 and 19847115], the polymer solids content is adjusted to a desired value by dilution or concentration, or other customary additives, such as, for example, foam-modifying or viscosity-modifying additives, are added to the aqueous polymer dispersion.The process according to the invention differs from this general procedure only in that it is carried out in two stages while adhering to the aforementioned framework parameters as well as the specific monomer compositions and a specific pH control.

[0012] For the preparation of the aqueous polymer dispersions accessible by the process according to the invention by two-stage aqueous emulsion polymerization, the following ethylenically unsaturated monomers A1, A2, A3, B1, B2 and B3 can be used.

[0013] All α,β-monoethylenically unsaturated C 3 - to C 6 -mono- or dicarboxylic acids can be used as monomers A1. Examples of C 3 - to C 6 -, preferably C 3 - or C 4 -mono- or dicarboxylic acids include acrylic acid, methacrylic acid, ethylacrylic acid, itaconic acid, allylacetic acid, crotonic acid, vinylacetic acid, vinyllactic acid, fumaric acid, maleic acid, and 2-methylmaleic acid. However, the monomers A1 also include the anhydrides of corresponding α,β-monoethylenically unsaturated dicarboxylic acids, such as maleic anhydride or 2-methylmaleic anhydride.

[0014] Acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid and / or crotonic acid are particularly advantageously used as monomers A1.

[0015] The total amount of monomers A1 is ≥ 1.0 and ≤ 3.0 wt.%, advantageously ≥ 1.0 and ≤ 2.0 wt.% and particularly advantageously ≥ 1.1 and ≤ 1.8 wt.%, in each case based on the total amount of monomers 1.

[0016] Suitable monomers A2 are all ethylenically unsaturated compounds which have at least one phosphorus-containing group. Examples of these are vinylphosphonic acid and / or a (meth)acryloxy(poly)alkoxyphosphate, where the (meth)acryloxy(poly)alkoxyphosphate has the following formula I: H 2 C=CH(H / CH 3 )-C(=O)-[AO] x -OP(=O)(-OH) 2 , formula (I) where AO: represents an ethyleneoxy [-OCH 2 CH 2 -], a propyleneoxy [-OCH(CH 3 )CH 2 -], a butyleneoxy group [-OCH(C 2 H 5 )CH 2 -] or mixtures thereof, with the ethyleneoxy group and / or propyleneoxy group being preferred, and x: represents a number between 1 and 30, with numbers between 1 and 20 being preferred and numbers between 1 and 10 being very particularly preferred.

[0017] Compounds of the following formulas are explicitly mentioned as (meth)acryloxy(poly)alkoxyphosphates: H 2 C=CH-C(=O)-OCH 2 CH 2 -OP(=O)(-OH) 2 H 2 C=CH-C(=O)-OCH(CH 3 )CH 2 -OP(=O)(-OH) 2 H 2 C=C(CH 3 )-C(=O)-OCH 2 CH 2 -OP(=O)(-OH) 2 H 2 C=C(CH 3 )-C(=O)-OCH(CH 3 )CH 2 -OP(=O)(-OH) 2 H 2 C=CH-C(=O)-[OCH 2 CH 2 ] 4-7 ​​-OP(=O)(-OH) 2 H 2 C=CH-C(=O)-[OCH(CH 3 )CH 2 ] 4-7 -OP(=O)(-OH) 2 H 2 C=C(CH 3 )-C(=O)-[OCH 2 CH 2 ] 4-7 ​​-OP(=O)(-OH) 2 H 2 C=C(CH 3 )-C(=O)-[OCH(CH 3 )CH 2 ] 4-7 ​​-OP(=O)(-OH) 2 and particularly preferably H 2 C=C(CH 3 )-C(=O)-[OCH 2 CH 2 ] 4-7 ​​-OP(=O)(-OH) 2 H 2 C=C(CH 3 )-C(=O)-[OCH(CH 3 )CH 2 ] 4-7 ​​-OP(=O)(-OH) 2 H 2 C=CH-C(=O)-[OCH(CH 3 )CH 2 ] 4-7 -OP(=O)(-OH) 2 H 2 C=CH-C(=O)-OCH 2 CH 2 -OP(=O)(-OH) 2 H 2 C=C(CH 3 )-C(=O)-OCH 2 CH 2 -OP(=O)(-OH) 2

[0018] The above-mentioned preferred (meth)acryloxy(poly)alkoxyphosphates are commercially available, for example as Sipomer ®< PAM-100, Sipomer ®< PAM-200, Sipomer ®< PAM-300 or Sipomer ®< PAM-4000 from Solvay / Rhodia and 2-(methacryloyloxy)ethyl phosphate from Sigma-Aldrich / Merck KGaA.

[0019] Of course, the monomers A1 and A2 also include the fully or partially neutralized water-soluble salts, in particular the alkali metal or ammonium salts, of the aforementioned acids.

[0020] The total amount of monomers A2 is ≥ 1.5 and ≤ 6.0 wt.%, advantageously ≥ 1.5 and ≤ 5.0 wt.% and particularly advantageously ≥ 1.5 and ≤ 4.0 wt.%, in each case based on the total amount of monomers 1.

[0021] All ethylenically unsaturated compounds that differ from monomers A1 and A2 can be used as monomers A3, such as, for example, alkyl (meth)acrylates. Preferably, these include alkyl (meth)acrylates whose linear or branched alkyl radical has 1 to 20 carbon atoms, particularly preferably 1 to 10, and very particularly preferably 1 to 8 carbon atoms. Important in this context is that the notation ("meth)acrylic acid" compounds or "(meth)acrylate" compounds generally encompasses both the corresponding acrylic acid compounds and the corresponding methacrylic acid compounds.

[0022] Examples of (meth)acrylic acid alkyl esters are (meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, (meth)acrylic acid n-propyl ester, (meth)acrylic acid n-butyl ester, (meth)acrylic acid iso-butyl ester, (meth)acrylic acid sec-butyl ester, (meth)acrylic acid n-pentyl ester, (meth)acrylic acid iso-pentyl ester, (meth)acrylic acid 2-methyl-butyl ester, (meth)acrylic acid amyl ester, (meth)acrylic acid n-hexyl ester, (meth)acrylic acid 2-ethylbutyl ester, (meth)acrylic acid pentyl ester, (meth)acrylic acid n-heptyl ester, (meth)acrylic acid n-octyl ester, (meth)acrylic acid 2-ethylhexyl ester, (meth)acrylic acid 2-propylheptyl ester, (meth)acrylic acid n-decyl ester, (Meth)acrylic acid undecyl ester and / or (meth)acrylic acid n-dodecyl ester.

[0023] Preferred (meth)acrylic acid alkyl esters are methyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, n-hexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate and / or 3-propylheptyl acrylate.

[0024] Vinyl aromatics with up to 20 C atoms can also be advantageously considered as monomers A3.

[0025] Vinylaromatics with up to 20 C atoms are optionally substituted aromatic systems with a vinyl group that is in conjugation to the aromatic ring system.

[0026] Such substituted vinylaromatics frequently contain one or more linear or branched alkyl groups, preferably one having 1 to 10 carbon atoms, often 1 to 6, and preferably 1 to 4 carbon atoms, which can be located on the aromatic or on the vinyl group. If the substituent is located on the aromatic, the substituent can preferably be in the ortho or para position, particularly preferably in the para position, to the vinyl group.

[0027] Suitable vinylaromatic compounds are, in particular, vinyltoluene, vinylnaphthalene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and / or styrene, although styrene and / or α-methylstyrene are particularly preferred.

[0028] The monomers A3 also include ethylenically unsaturated nitriles having up to 20 C atoms, such as in particular fumaronitrile, acrylonitrile and methacrylonitrile, preferably acrylonitrile and methacrylonitrile and particularly preferably acrylonitrile, vinyl esters of carboxylic acids containing up to 20 C atoms, such as in particular vinyl laurate, vinyl stearate, vinyl propionate, vinyl versatic acid ester, vinyl butyrate and vinyl acetate, but preferably vinyl acetate, vinyl and vinylidene halides having up to 10 C atoms, such as in particular ethylenically unsaturated compounds substituted by chlorine, fluorine or bromine, preferably vinyl chloride and vinylidene chloride and vinyl ethers of alcohols containing 1 to 10 C atoms, such as advantageously methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, sec-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether and n-octyl vinyl ether, with vinyl ethers of alcohols containing 1 to 4 C atoms being preferred.

[0029] With particular advantage, the at least one monomer A3 is selected to ≥ 80 wt.% from the group comprising n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, styrene and methyl methacrylate.

[0030] To a minor extent, ie > 0 and ≤ 20 wt.%, advantageously ≥ 1 and ≤ 10 wt.% and particularly advantageously ≥ 1 and ≤ 6 wt.%, in each case based on the total amount of monomers A3, the monomers A3 may also comprise the following functionalized ethylenically unsaturated monomers.

[0031] Suitable functionalized ethylenically unsaturated monomers are all monoethylenically unsaturated compounds having at least one hydroxy group, such as in particular all hydroxyalkyl, advantageously hydroxy-C 2 -C 10 -alkyl, preferably hydroxy-C 2 -C 4 -alkyl and particularly advantageously hydroxy-C 2 -C 3 -alkyl acrylates and / or methacrylates, wherein in the context of this document the alkoxylated hydroxyalkyl acrylates and / or methacrylates, ie the hydroxyalkyl acrylates and / or methacrylates reacted with alkylene oxides (essentially ethylene oxide and propylene oxide), are also to be regarded as monomers A3. Advantageously, the hydroxyalkyl group-containing monomer A3 is selected from the group comprising diethylene glycol monoacrylate, 4-hydroxybutyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl acrylate, diethylene glycol monomethacrylate, 4-hydroxybutyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxypropyl methacrylate and 2-hydroxyethyl methacrylate.2-Hydroxyethyl acrylate and / or 2-hydroxyethyl methacrylate are particularly advantageously used, with 2-hydroxyethyl methacrylate being particularly preferred.

[0032] The functionalized ethylenically unsaturated monomers should also include hydroxyalkyl acrylates and methacrylates that have more than one hydroxyl group, for example, two to five, preferably two to four, particularly preferably two to three hydroxyl groups. Examples include glycerol monoacrylate and methacrylate, trimethylolpropane monoacrylate and methacrylate, pentaerythritol monoacrylate and methacrylate, as well as monoacrylates and methacrylates of sugar alcohols, such as sorbitol, mannitol, diglycerol, threitol, erythritol, adonitol (ribitol), arabitol (lyxitol), xylitol, dulcitol (galactitol), maltitol, and isomalt.

[0033] The functionalized ethylenically unsaturated compounds A3 that can be used according to the invention also include organic compounds that have at least two non-conjugated ethylenically unsaturated groups, such as, for example, 1,2-, 1,3- and 1,4-butanediol diacrylate, 1,2- and 1,3-propylene glycol (meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, pentaerythritol tri- and tetra(meth)acrylate, allyl methacrylate, 1,2-, 1,3- and 1,4-divinylbenzene and mixtures thereof. These compounds are particularly preferably selected from the group consisting of divinylbenzene, 1,4-butanediol diacrylate, and allyl methacrylate.

[0034] Further functionalized ethylenically unsaturated compounds A3 which can be used according to the invention are selected from the group consisting of (meth)acrylic acid 2-(2-oxo-imidazolidin-1-yl)-ethyl ester (2-ureidoethyl acrylate and 2-ureidoethyl (meth)acrylate), N-[2-(2-oxo-oxazolidin-3-yl)-ethyl]-methacrylate, 2-(acetoacetoxy)ethyl acrylate, acetoacetoxypropyl methacrylate, acetoacetoxybutyl methacrylate, 2-(acetoacetoxy)ethyl methacrylate, diacetoneacrylamide (DAAM) and diacetone methacrylamide. Preferred in this group are (meth)acrylic acid 2-(2-oxo-imidazolidin-1-yl)-ethyl ester, (acetoacetoxy)ethyl methacrylate, diacetoneacrylamide and / or diacetone methacrylamide, particularly preferred are (meth)acrylic acid 2-(2-oxo-imidazolidin-1-yl)-ethyl ester and (acetoacetoxy)ethyl methacrylate.

[0035] The functionalized ethylenically unsaturated compounds A3 that can be used according to the invention also include compounds with a (meth)acrylate and an epoxy group. Of particular note are glycidyl acrylate and glycidyl methacrylate, preferably glycidyl methacrylate.

[0036] The functionalized ethylenically unsaturated compounds A3 which can be used according to the invention also include ethylenically unsaturated compounds having at least one silicon-containing group, such as, for example, vinyltriacetoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane or vinyltriethoxysilane.

[0037] It is particularly advantageous that at least one monomer A3 is selected to > 0 and ≤ 20 wt.% from the group comprising 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-(acetoacetoxy)ethyl methacrylate, 2-ureidoethyl methacrylate, diacetoneacrylamide, glycidyl methacrylate, 3-(methacryloyloxy)propyltrimethoxysilane, vinyltriethoxysilane, allyl methacrylate and 1,4-butanediol diacrylate.

[0038] The total amount of monomers A3 is ≥ 91.0 and ≤ 97.5 wt.%, advantageously ≥ 93.0 and ≤ 97.5 wt.% and particularly advantageously ≥ 95.2 and ≤ 97.4 wt.%, in each case based on the total amount of monomers 1.

[0039] According to the invention, the type and amounts of monomers A1 to A3 are selected such that the polymer 1 obtained therefrom after polymerization has a glass transition temperature Tg 1< measured according to DIN EN ISO 11357-2 (2013-09) [differential thermal analysis, midpoint temperature, heating rate 20 K / min] in the range ≥ -10 and ≤ 15 °C, advantageously ≥ -5 and ≤ 10 °C, and particularly advantageously ≥ -5 and ≤ 5 °C. It is important that all glass transition temperatures stated in this document are determined by the aforementioned method.

[0040] It is known to the person skilled in the art that according to Fox (TG Fox, Bull. Am. Phys. Soc. 1956 [Ser. II] 1, page 123 and according to Ullmann's Encyclopedia of Technical Chemistry, Vol. 19, page 18, 4th edition, Verlag Chemie, Weinheim, 1980) the glass transition temperature of at most weakly crosslinked copolymers can be determined using the following formula 1 / Tg = x 1 / Tg 1 + x 2 / Tg 2 + … x n / Tg n , can be estimated to a good approximation, where x 1 , x 2 , .... xn are the mass fractions of the monomers 1, 2, .... n and Tg 1< , Tg 2< , .... Tg n< are the glass transition temperatures of the polymers each made up of only one of the monomers 1, 2, .... n in degrees Kelvin. The glass transition temperatures of these homopolymers of most ethylenically unsaturated monomers are known (or can be determined experimentally in a simple manner known per se) and are given, for example, in J. Brandrup, EH Immergut, Polymer Handbook 1st Ed. J. Wiley, New York, 1966, 2nd Ed. J. Wiley, New York, 1975 and 3rd Ed. J. Wiley, New York, 1989, and in Ullmann's Encyclopedia of Industrial Chemistry, page 169, Verlag Chemie, Weinheim, 1992.

[0041] It is advantageous to use in the first polymerization stage ≥ 1.0 and ≤ 3.0 wt% Acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid and / or crotonic acid, ≥ 1.5 and ≤ 6.0 wt% H 2 C=C(CH 3 )-C(=O)-[OCH(CH 3 )CH 2 ] 4-7 ​​-OP(=O)(-OH) 2 , H 2 C=C(CH 3 )-C(=O)-[OCH 2 CH 2 ] 4-7 ​​-OP(=O)(-OH) 2 and / or H 2 C=C(CH 3 )-C(=O)-OCH 2 CH 2 -OP(=O)(-OH) 2 , ≥ 81 and ≤ 97.5 wt% n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, styrene and / or methyl methacrylate, and ≥ 0 and ≤ 10 wt% 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-(acetoacetoxy)ethyl methacrylate, 2-ureidoethyl methacrylate, diacetone acrylamide, glycidyl methacrylate, 3-(methacryloyloxy)propyltrimethoxysilane, vinyltriethoxysilane, allyl methacrylate and / or 1,4-butanediol diacrylate, and especially preferred ≥ 1.0 and ≤ 2.0 wt% Acrylic acid and / or methacrylic acid, ≥ 1.5 and ≤ 5.0 wt% H 2 C=C(CH 3 )-C(=O)-[OCH(CH 3 CH 2 )] 4-7 ​​-OP(=O)(-OH) 2 ≥ 85 and ≤ 97.5 wt% Methyl methacrylate, styrene and / or 2-ethylhexyl acrylate, and ≥ 0 and ≤ 8.0 wt% (Acetoacetoxy)ethyl methacrylate and / or vinyltriethoxysilane, used.

[0042] All of the aforementioned monomers A1 are suitable as monomers B1. The amounts of monomers B1 are ≤ 0.1 wt. %, advantageously ≤ 0.05 wt. %, and particularly advantageously ≤ 0.01 wt. %, in each case based on the total amount of monomers 2.

[0043] Analogously, all of the aforementioned monomers A2 are suitable as monomers B2. The amounts of monomers B2 are ≤ 0.1 wt. %, advantageously ≤ 0.05 wt. %, and particularly advantageously ≤ 0.01 wt. %, each based on the total amount of monomers 2.

[0044] However, it is advantageous not to use any monomers B1 and B2.

[0045] In principle, all of the aforementioned monomers A3 are suitable as monomers B3, although the proportion of functionalized ethylenically unsaturated monomers is ≤ 1.0 wt. %, advantageously ≤ 0.5 wt. %, and particularly advantageously ≤ 0.1 wt. %, in each case based on the total amount of monomers B3. Particularly advantageously, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, styrene, and methyl methacrylate are used as monomers B3, the proportion of which is ≥ 99.0 wt. %, preferably ≥ 99.5 wt. % and particularly preferably ≥ 99.9 wt. %, in each case based on the total amount of monomers B3. With particular advantage, the monomers B3 are selected to 100 wt.% from the group comprising n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, styrene and methyl methacrylate.

[0046] According to the invention, the type and amounts of monomers B1 to B3 are selected such that the polymer 2 obtained therefrom after polymerization has a glass transition temperature Tg 2< that is at least 10 °C above the glass transition temperature Tg 1< [Tg 2< = Tg 1< + ≥ 10 °C]. Advantageously, the glass transition temperature Tg 2< is at least 15 °C above the glass transition temperature Tg 1< . The glass transition temperature Tg 2< is therefore in the range ≥ 0 and ≤ 80 °C, advantageously ≥ 10 and ≤ 60 °C, and particularly advantageously ≥ 10 and ≤ 40 °C.

[0047] Advantageously, in the second polymerization stage ≥ 0 and ≤ 95 wt% n-butyl methacrylate, ≥ 2 and ≤ 90 wt% Styrene, and ≥ 0 and ≤ 40 wt% Methyl methacrylate and / or 2-ethylhexyl acrylate, and especially preferred ≥ 5 and ≤ 95 wt% n-butyl methacrylate, ≥ 2 and ≤ 70 wt% Styrene, and ≥ 0 and ≤ 25 wt% Methyl methacrylate and / or 2-ethylhexyl acrylate used.

[0048] Advantageously, the type and amounts of the monomers A1 to A3 and B1 to B3 are selected such that the resulting polymer 1 has a glass transition temperature Tg 1< in the range ≥ -5 and ≤ 10 °C and the resulting polymer 2 has a glass transition temperature Tg 2< in the range ≥ 10 and ≤ 40 °C.

[0049] It is essential that the ratio of total monomer quantity 1 to total monomer quantity 2 is 70 to 85 wt.% to 15 to 30 wt.% and advantageously 70 to 80 wt.% to 20 to 30 wt.%.

[0050] It is important according to the invention that the aforementioned monomers A1 to A3 and B1 to B3 can be used individually or as mixtures. The total or partial amounts of monomers A1 to A3 can be initially introduced into the aqueous polymerization medium before initiating the polymerization reaction, and any remaining partial amounts can be metered in under polymerization conditions. However, it is also possible to meter the total amounts of monomers A1 to A3 (total monomer amount 1) into the aqueous polymerization medium under polymerization conditions.

[0051] In a preferred embodiment, in the first polymerization stage, at least a portion ≤ 10 wt. % of the total monomer amount 1 is initially introduced into the aqueous polymerization medium before initiation of the polymerization reaction, and the remaining amount is metered into the aqueous polymerization medium under polymerization conditions, while in the second polymerization stage, the total amount of monomers B1 to B3 (total monomer amount 1) is metered into the aqueous polymerization medium under polymerization conditions. The monomers A1 to A3 and B1 to B3 can be metered into the aqueous polymerization medium in individual streams, as a monomer mixture, or in the form of an aqueous monomer emulsion, discontinuously, or continuously at constant or varying flow rates.

[0052] However, it is particularly advantageous to use the monomers of the first and second polymerization stages as monomer mixtures, particularly advantageously as aqueous monomer emulsions. Advantageously, at least ≥ 90 wt.% and particularly advantageously ≥ 95 wt.%, or the total amounts of the monomer mixtures of the first and second polymerization stages, are metered into the aqueous polymerization medium as aqueous monomer emulsions under polymerization conditions.

[0053] The free-radically initiated aqueous emulsion polymerization according to the invention is generally carried out in the presence of a free-radical polymerization initiator (radical initiator). Suitable free-radical initiators are all those capable of initiating a free-radical aqueous emulsion polymerization. These can, in principle, be either peroxides or azo compounds. Redox initiator systems are, of course, also suitable. Peroxides that can be used are, in principle, inorganic peroxides such as hydrogen peroxide or peroxodisulfates, such as the mono- or di-alkali metal or ammonium salts of peroxodisulfuric acid, such as, for example, their mono- and disodium, potassium, or ammonium salts, or organic peroxides such as alkyl hydroperoxides, for example tert-butyl, p-mentyl, or cumyl hydroperoxide, as well as dialkyl or diaryl peroxides, such as di-tert-butyl or dicumyl peroxide.The azo compounds used are primarily 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(amidinopropyl) dihydrochloride (AlBA, equivalent to V-50 from Wako Chemicals). Of course, so-called redox initiator systems can also be used as radical initiators. 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, 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.

[0054] Initiation of the polymerization reaction refers to the start of the polymerization reaction of the monomers present in the polymerization vessel after radical formation by the radical initiator. The polymerization reaction can be initiated by adding radical initiator to the aqueous polymerization mixture in the polymerization vessel under polymerization conditions. However, it is also possible to add some or all of the radical initiator to the aqueous polymerization mixture containing the initial monomers in the polymerization vessel under conditions that are unsuitable for initiating a polymerization reaction, for example, at low temperature, and then to adjust polymerization conditions in the aqueous polymerization mixture.Polymerization conditions generally refer to the temperatures and pressures under which radically initiated aqueous emulsion polymerization proceeds at a sufficient polymerization rate. They depend particularly on the radical initiator used. The type and amount of radical initiator, the polymerization temperature, and the polymerization pressure are advantageously selected such that the radical initiator has a half-life of < 3 hours and, particularly advantageously, < 1 hour, while ensuring that sufficient initiator radicals are always available to initiate and maintain the polymerization reaction.

[0055] The entire range from 0 to 170 °C is suitable as the reaction temperature for free-radically initiated aqueous emulsion polymerization. Temperatures generally used are from 50 to 120 °C, preferably from 60 to 110 °C, and particularly preferably from 60 to 100 °C. Free-radically initiated aqueous emulsion polymerization can be carried out at a pressure of less than, equal to, or greater than 1 atm [1.013 bar (absolute), atmospheric pressure], so that the polymerization temperature can exceed 100 °C and reach up to 170 °C. In the presence of monomers A1 to B3 with a low boiling point, the emulsion polymerization is preferably carried out under elevated pressure. The pressure can be 1.2, 1.5, 2.5, 10, 15 bar (absolute), or even higher. If the emulsion polymerization is carried out under negative pressure, pressures of 950 mbar, frequently 900 mbar and often 850 mbar (absolute) are set.The radical aqueous emulsion polymerization is advantageously carried out at 1 atm under exclusion of oxygen, in particular under an inert gas atmosphere, such as nitrogen or argon.

[0056] According to the invention, the entire amount of radical initiator 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 initiator into the aqueous reaction medium before initiating the polymerization reaction and then, under polymerization conditions during the radically initiated emulsion polymerization, add the entire amount or any remaining amount continuously or discontinuously in the first and / or second polymerization stage, depending on consumption. Of course, different radical initiators can be used in different amounts in the first and second polymerization stages.In a preferred embodiment, a portion of the radical initiator is initially introduced into the aqueous reaction medium before initiation of the polymerization reaction and the remaining amount is added in parallel with the monomer metering during the first and second polymerization stages.

[0057] As a rule, the total amount of radical initiators is ≥ 0.05 and ≤ 5 wt.%, preferably ≥ 0.1 and ≤ 3 wt.% and particularly preferably ≥ 0.1 and ≤ 1.5 wt.%, in each case based on the total amount of monomers.

[0058] Radical chain transfer compounds (radical chain regulators) can be used to adjust the weight-average molecular weights of the polymers formed in the first and second polymerization stages. 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-nonanethiol 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 6-methylheptyl 3-mercaptopropionate or 2-ethylhexyl 2-mercaptoethanoate as well as all others in the Polymer Handbook 3rd edition, 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 or vinylcyclohexane, or hydrocarbons with easily abstracted hydrogen atoms, such as toluene, are used. However, it is also possible to use mixtures of the aforementioned non-interfering radical chain regulators.

[0059] 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, under polymerization conditions during the radically initiated emulsion polymerization, add the entire amount or any remaining amount continuously or discontinuously as needed in the first and / or second polymerization stage. Of course, different radical chain regulators can be used in different amounts in the first and second polymerization stages.

[0060] As a rule, the total amount of radical chain regulator is ≥ 0 and ≤ 5 wt.%, preferably ≥ 0 and ≤ 2 wt.% and particularly preferably ≥ 0 and ≤ 1 wt.%, in each case based on the total amount of monomers.

[0061] Essential to the invention is that the aqueous emulsion polymerization is carried out in the presence of at least one phosphorus-containing dispersing agent, which keeps both the monomer droplets and the resulting polymer particles dispersed in the aqueous phase and thus ensures the stability of the resulting aqueous polymer dispersion. In principle, all dispersing agents containing at least one phosphorus-containing group are suitable as phosphorus-containing dispersing agents.

[0062] Suitable dispersing agents containing phosphorus groups are, for example, mono- and / or diesters of phosphoric acid with alkoxylated and / or non-alkoxylated C 6 to C 30 fatty alcohols, as disclosed, for example, in WO 2009 / 17757, sections

[0006] ,

[0007] and

[0034] to

[0065] or in WO 2009 / 115607, page 4, lines 22 to 34 and page 25, line 31 to page 26, line 14. It is important to note that, within the scope of this document, express reference is made to these references and, therefore, the dispersing agents containing phosphorus groups disclosed therein are to be regarded as part of this document.

[0063] However, in the context of this document, it is particularly advantageous to use dispersing agents containing phosphorus groups which are selected from compounds of the formula II R 1< -O-(AO) m -P(=O)(OR 2< )(OH) Formula (II) wherein m represents an integer from 0 to 30, preferably 5 to 25 and particularly preferably 5 to 20, AO represents alkyleneoxy, as defined under the compounds of the general formula I, R 1< represents C 6 -C 30 alkyl, preferably C 8 -C 22 alkyl and particularly preferably C 11 -C 14 alkyl and R 2< represents H or a group -(AO) m -R 2a<, in which R 2a< has the meaning given for R 1< and AO and m have one of the meanings given above, but R 2< advantageously represents H, and the alkali metal or ammonium salts of the aforementioned compounds of formula II;

[0064] The above-mentioned dispersing agents containing phosphorus groups are familiar to the person skilled in the art and are commercially available, for example under Maphos ®< 24 T (von BASF BTC), Maphos ®< 10 T (von BASF BTC) Amphisol ®< A (von DSM Nutritional Products Europe Ltd.) Colafax ®< CPE (von Colonial Chemical, Inc.) Crodafos ®< MCA (von Croda Inc.), Crodafos ®< CES (von Croda Inc.), Crodafos ®< HCE (von Croda Inc.), Crodafos ®< 1435 (von Croda Inc.), Crodafos ®< CS 20 Acid (von Croda Inc.), Crodafos ®< CP (von Croda Inc.), Hostaphat ®< CC100 (von Clariant International Ltd.), Rhodafac ®< RS-410 (von Solvay SA) Rhodafac ®< RS-610 (von Solvay SA) Rhodafac ®< RS-610 / A25 (von Solvay SA) Rhodafac ®< RS-610 E (von Solvay SA) Rhodafac ®< RS-710 (von Solvay SA) Rhodafac ®< RS-710 E (von Solvay SA) oder Lutensit ®< A-EP (von BASF SE)

[0065] The amount of the at least one dispersing aid containing phosphorus groups used according to the invention is ≥ 0.5 wt.%, advantageously ≥ 0.5 and ≤ 4.0 wt.%, preferably ≥ 0.5 and ≤ 2.0 wt.% and particularly preferably ≥ 0.7 and ≤ 1.5 wt.%, in each case based on the total amount of monomers.

[0066] According to the invention, the entire amount of the phosphorus group-containing dispersing agent can be initially introduced into the aqueous reaction medium before initiating the polymerization reaction. However, it is also possible, if appropriate, to initially introduce only a portion of the phosphorus group-containing dispersing agent into the aqueous reaction medium before initiating the polymerization reaction and then, under polymerization conditions during the free-radical-initiated emulsion polymerization, to add the entire amount or any remaining amount continuously or discontinuously as required in the first or in the first and second polymerization stages. Of course, different phosphorus group-containing dispersing agents can be used in different amounts in the first and second polymerization stages. Advantageously, ≥ 50 wt.-% of the at least one phosphorus group-containing dispersing agent is added to the aqueous reaction medium as a component of the aqueous monomer emulsion during the polymerization reaction. However, it is essential that at least a portion of the at least one phosphorus group-containing dispersing agent is already present during the first polymerization stage. The amount of the at least one phosphorus group-containing dispersing agent is advantageously ≥ 0.5 wt.% and advantageously ≥ 0.8 wt.% at any time during the aqueous emulsion polymerization, based in each case on the total amount of monomers A1 to B3 added to the aqueous polymerization mixture at the time in question.

[0067] Optionally, in addition to the at least one dispersing agent containing phosphorus groups, further protective colloids and / or emulsifiers commonly used for carrying out radical aqueous emulsion polymerizations can be used.

[0068] Suitable protective colloids include polyvinyl alcohols, cellulose derivatives, or vinylpyrrolidone-containing copolymers. A detailed description of other suitable protective colloids can be found in Houben-Weyl, Methoden der organischen Chemie (Methods of Organic Chemistry), Volume XIV / 1, Makromolekulare Stoffe (Macromolecular Materials), pages 411 to 420, Georg-Thieme-Verlag, Stuttgart, 1961. Of course, mixtures of emulsifiers and / or protective colloids can also be used. Preferably, only emulsifiers are used as additional dispersing aids, whose relative molecular weights, unlike the protective colloids, are usually below 1000. They can be anionic, cationic, or nonionic. Of course, when using mixtures of surface-active substances, the individual components must be compatible with each other; in case of doubt, this can be verified by conducting a few preliminary tests.In general, anionic emulsifiers are compatible with each other and with nonionic emulsifiers. The same applies to cationic emulsifiers, while anionic and cationic emulsifiers are usually incompatible with each other. Common emulsifiers are, for example, ethoxylated mono-, di- and tri-alkylphenols (EO degree: 3 to 50, alkyl radical: C4 to C12), ethoxylated fatty alcohols (EO degree: 3 to 50; alkyl radical: C8 to C36) as well as alkali metal and ammonium salts of alkyl sulfates (alkyl radical: C8 to C12), of sulfuric acid half esters of ethoxylated alkanols (EO degree: 4 to 30, alkyl radical: C12 to C18) and ethoxylated alkylphenols (EO degree: 3 to 50, alkyl radical: C4 to C12), of alkylsulfonic acids (alkyl radical: C12 to C18) and of alkylarylsulfonic acids (alkyl radical: C9 to C18). Further suitable emulsifiers can be found in Houben-Weyl, Methods of Organic Chemistry, Volume XIV / 1, Macromolecular Substances, pages 192 to 208, Georg-Thieme-Verlag, Stuttgart, 1961.

[0069] Compounds of the general formula III have also proven to be suitable as surface-active substances. wherein R 3< and R 4< are hydrogen atoms or C 4 - to C 24 -alkyl and are not simultaneously hydrogen atoms, and M 1< and M 2< can be alkali metal ions and / or ammonium ions, have proven suitable. In the general formula III, R 3< and R 4< are preferably linear or branched alkyl radicals having 6 to 18 carbon atoms, in particular having 6, 12 and 16 carbon atoms, or hydrogen, where R 3< and R 4< are not both simultaneously hydrogen atoms. M 1< and M 2< are preferably sodium, potassium or ammonium, with sodium being particularly preferred. Particularly advantageous are compounds of the general formula III in which M 1< and M 2< are sodium, R 3< is a branched alkyl radical having 12 carbon atoms and R 4< is a hydrogen atom or R 3<. Technical mixtures containing 50 to 90 wt.% of the monoalkylated product are frequently used, such as Dowfax ®< 2A1 (a trademark of the Dow Chemical Company). The compounds of general formula III are generally known, e.g.from US-A 4269749, and commercially available.

[0070] If additional dispersing aids are used in addition to the at least one dispersing aid containing phosphorus groups, anionic and / or non-ionic and particularly advantageous anionic surfactants are used.

[0071] As a rule, the total amount of optional dispersing aids is ≥ 0 and ≤ 3.0 wt.%, preferably ≥ 0 and ≤ 2.0 wt.% and particularly preferably ≥ 0.1 and ≤ 0.5 wt.%, in each case based on the total amount of monomers.

[0072] According to the invention, under polymerization conditions during the free-radical-initiated emulsion polymerization, the total amount of optional dispersing agent is added continuously or discontinuously as needed in the first and / or second polymerization stage. However, it is also possible to initially charge the entire amount or a portion of the optionally used dispersing agent in the aqueous reaction medium before initiating the polymerization reaction and to meter in any remaining amount continuously or discontinuously during the first and / or second polymerization stage.

[0073] It is also essential that the radically initiated aqueous emulsion polymerization in the first polymerization stage can optionally also be carried out in the presence of a polymer seed, for example in the presence of 0.01 to 10 wt.%, frequently 0.05 to 7.0 wt.% and often 0.1 to 4.0 wt.% of a polymer seed, in each case based on the total amount of monomers.

[0074] According to the invention, a polymer seed is used in particular when the particle size of the polymer particles to be produced by means of a radically initiated aqueous emulsion polymerization is to be adjusted in a targeted manner (see, for example, US-A 2520959 and US-A 3397165).

[0075] If a polymer seed is used in the process according to the invention, its polymer seed particles advantageously have a weight-average diameter Dw ≤ 100 nm, frequently ≥ 5 nm to ≤ 50 nm and often ≥ 15 nm to ≤ 35 nm.

[0076] The polymer seed is usually used in the form of an aqueous polymer dispersion.

[0077] If a polymer seed is used, it is advantageous to use an external polymer seed. In contrast to a so-called in situ polymer seed, which is prepared in the reaction vessel before the start of the actual emulsion polymerization and which generally has the same monomer composition as the polymer 1 prepared by the subsequent free-radical-initiated aqueous emulsion polymerization, an external polymer seed is understood to be a polymer seed that was prepared in a separate reaction step and whose monomer composition differs from the polymer 1 prepared by the free-radical-initiated aqueous emulsion polymerization. This simply means that different monomers or monomer mixtures with different compositions are used to prepare the external polymer seed and to prepare the aqueous polymer dispersion.The preparation of a foreign polymer seed is familiar to the person skilled in the art and is usually carried out in such a way that a relatively small amount of monomers and a relatively large amount of emulsifiers are placed in a reaction vessel and a sufficient amount of polymerization initiator is added at reaction temperature.

[0078] According to the invention, preference is given to using a polymer seed having a glass transition temperature of ≥ 50 °C, frequently ≥ 60 °C or ≥ 70 °C, and often ≥ 80 °C or ≥ 90 °C. A polystyrene or polymethyl methacrylate polymer seed is particularly preferred.

[0079] The entire amount of foreign polymer seed can be initially introduced into the polymerization vessel. However, it is also possible to initially introduce only a portion of the foreign polymer seed into the polymerization vessel and add the remaining amount during the polymerization process together with the monomers A1 to A3 or B1 to B3. If necessary, the entire amount of foreign polymer seed can also be added during the polymerization process. Preferably, the entire amount of foreign polymer seed is initially introduced into the polymerization vessel before initiating the polymerization reaction.

[0080] The process according to the invention is advantageously carried out in such a way that the second polymerization stage is not commenced until the total monomer amount 1 has been converted to ≥ 98 wt. %, advantageously to ≥ 99 wt. %, and particularly advantageously to ≥ 99.5 wt. %, which can be easily determined using calorimetric measurements familiar to the person skilled in the art. Polymerization stage 2 is also carried out in a corresponding manner until a monomer conversion of ≥ 98 wt. %, advantageously ≥ 99 wt. %, and particularly advantageously to 99.5 wt. % of the total monomer amount 2 has been achieved.

[0081] According to the invention, the pH of the aqueous polymerization mixture is advantageously in the range ≥ 3 and ≤ 8 during both the first and the second polymerization stage, and particularly advantageously in the range ≥ 4.0 and ≤ 6.5, measured at room temperature. According to the invention, the pH measurement or pH control is carried out in such a way that a small amount of the aqueous polymerization mixture is continuously discharged from the polymerization vessel via a small bypass line and cooled to 20 to 25 °C (room temperature), the pH is determined from this using a calibrated pH electrode, and the aqueous polymerization mixture is then returned to the polymerization vessel. Of course, it is also possible to take a small sample of the aqueous polymerization mixture, cool it to room temperature, measure the pH, and then return the sample to the aqueous polymerization mixture.

[0082] According to the invention, all customary bases can be used to adjust the pH, such as alkali, alkaline earth or ammonium hydroxides or carbonates or bicarbonates, such as, for example, NaOH, KOH, NH 4 OH, Ca(OH) 2 , Na 2 CO 3 , K 2 CO 3 , (NH 4 )CO 3 , NaHCO 3 , KHCO 3 or NH 4 HCO 3 . Also suitable as bases are ammonia and primary, secondary or tertiary organic amines, such as methylamine, ethylamine, propylamine-1, propylamine-2, n-butylamine-1, n-butylamine-2, 2-methylpropylamine-1, 2-methylpropylamine-2 etc., dimethylamine, diethylamine, di-n-propylamine, di-iso-propylamine, di-n-butylamine, di-2-methylpropylamine etc., trimethylamine, triethylamine, tri-n-propylamine, tri-iso-propylamine, tri-n-butylamine, tri-2-methylpropylamine etc., but also mixed amines, such as N-methyl-N-ethylamine, N,N-dimethyl-N-ethylamine etc.However, bases which have a boiling point of ≤ 20 °C, advantageously ≤ 10 °C and particularly advantageously ≤ 0 °C at a pressure of 1.013 bar (absolute) are advantageously used to adjust the pH, such as in particular trimethylamine and ammonia, in particular in the form of its aqueous solution or its basic salts (NH 4 ) 2 CO 3 , NH 4 HCO 3 , although ammonia, in particular in the form of its aqueous solution, is particularly preferred.

[0083] The aqueous polymer dispersion obtained after the second polymerization stage contains polymer particles whose weight-average particle diameter is in the range ≥ 50 and ≤ 500 nm, advantageously in the range ≥ 50 and ≤ 200 nm, and in particular in the range ≥ 80 and ≤ 150 nm. According to the invention, the weight-average particle diameter is generally determined according to ISO 13321 using a Malvern High Performance Particle Sizer at 22 °C and a wavelength of 633 nm.

[0084] Of course, a preferred embodiment also encompasses the aqueous polymer dispersions obtainable by the process according to the invention, as well as polymer powders obtainable by drying them. The production of polymer powder by drying aqueous polymer dispersions is familiar to those skilled in the art and is carried out, for example, by freeze-drying or spray-drying.

[0085] Importantly, the aqueous polymer dispersions produced by the process according to the invention are characterized by high stability and low coagulum formation. Furthermore, the V2A or V4A steel reactors used for the process according to the invention exhibit no or significantly lower corrosion phenomena, particularly due to pH control.

[0086] It is also important that the aqueous polymer dispersions obtainable by the process according to the invention and the polymer powders obtainable therefrom by drying can be used advantageously as binders in the production of adhesives, sealants, synthetic resin plasters, paper coating slips, fiber nonwovens, flexible roof coatings and paints as well as in sand consolidation, as a component in the production of textile or leather auxiliaries and impact modifiers or for modifying mineral binders and plastics.

[0087] The aqueous polymer dispersions according to the invention or their polymer powders are particularly advantageously suitable as binders in aqueous corrosion protection formulations for metal surfaces, which also includes the surfaces of metal alloys. If multilayer systems are used, the aqueous polymer dispersions according to the invention or their polymer powders can be used as binders in one or more layers.

[0088] If the aforementioned aqueous formulations are used to produce aqueous corrosion protection formulations, these aqueous formulations may contain, in addition to conventional components such as organic solvents, coalescing agents, additional additives such as dispersing agents, neutralizing agents, defoamers, thickeners and leveling agents as well as bactericidal or fungicidal auxiliaries, additional pigments, fillers and / or corrosion inhibitors.

[0089] In principle, all organic and / or inorganic white or colored pigments familiar to the person skilled in the art with a particle size of ≤ 15 µm, measured according to ISO 1524 using a Hegmann grindometer, can be used as pigments.

[0090] The most important white pigment is titanium dioxide in its various modifications due to its high refractive index (rutile: 2.70 and anatase: 2.55) and its good hiding power. Zinc oxide and zinc sulfide are also used as white pigments. These white pigments can be used in surface-coated (i.e., coated) or uncoated (i.e., uncoated) form. In addition, organic white pigments, such as non-film-forming hollow polymer particles rich in styrene and carboxyl groups with a particle size of approximately 300 to 400 nm (so-called opaque particles), are also used.

[0091] In addition to white pigments, a wide variety of colored pigments familiar to the expert can be used for color design, for example the somewhat cheaper inorganic iron, cadmium, chromium and lead oxides or sulfides, lead molybdate, cobalt blue or carbon black as well as the somewhat more expensive organic pigments, for example phthalocyanines, azo pigments, quinacridones, perylenes or carbazoles.

[0092] Of course, the aqueous formulations can also contain fillers familiar to those skilled in the art in addition to the pigments. Fillers are essentially understood to be powdered inorganic materials with a particle size of ≤ 20 µm (according to Hegmann) and a lower refractive index than the pigments (white fillers have refractive index values ​​of < 1.7 according to DIN 55943 and DIN 55945). The powdered fillers are often naturally occurring minerals, such as calcite, chalk, dolomite, kaolin, talc, mica, diatomaceous earth, barite, quartz, or talc / chlorite intergrowths, but also synthetically produced inorganic compounds, such as precipitated calcium carbonate, calcined kaolin, barium sulfate, and pyrogenic silica. Calcium carbonate in the form of crystalline calcite or amorphous chalk is preferred as the filler.

[0093] According to the invention, corrosion inhibitors or corrosion protection pigments are particularly suitable as corrosion protection agents.

[0094] Examples of corrosion inhibitors are listed in "Corrosion Inhibitors. 2nd Edition. An Industrial Guide," Ernest W. Flick, Ed: William Andrew Inc ISBN: 978-0-8155-1330-8. Preferred corrosion inhibitors are hexamine, benzotriazole, phenylenediamine, dimethylethanolamine, polyaniline, sodium nitrite, cinnamaldehyde, condensation products of aldehydes and amines (imines), chromates, nitrites, phosphates, hydrazine, and ascorbic acid.

[0095] Examples of corrosion protection pigments are modified zinc orthophosphates (e.g. HEUCOPHOS ®< ZPA, ZPO and ZMP), polyphosphates (e.g. HEUCOPHOS ®< ZAPP, SAPP, SRPP and CAPP), WSA - Wide Spectrum Anticorrosives (e.g. HEUCOPHOS ®< ZAMPLUS and ZCPPLUS) and modified silicate pigments (e.g. HEU-COSIL ®< CTF, Halox ®< 750), for example from Heubach GmbH, as well as barium borophosphate (e.g. Halox ®< 400), barium phosphosilicates (e.g. Halox ®< BW-111, Halox ®< BW-191), calcium borosilicates (e.g. Halox ®< CW-291, CW-22 / 221, CW-2230), calcium phosphosilicate (e.g. Halox ®< CW-491), strontium phosphosilicate (e.g. Halox ®< SW-111) or strontium zinc phosphosilicate (e.g. Halox ®< SZP-391) from Halox ®< .

[0096] In one embodiment, therefore, aqueous corrosion protection formulations are also included which contain at least one aqueous polymer dispersion according to the invention or at least one polymer powder according to the invention.

[0097] Also included according to the invention is a method for coating metal surfaces, which is characterized in that an aqueous corrosion protection formulation containing an aqueous polymer dispersion according to the invention or a polymer powder according to the invention is applied to a metal surface and then dried.

[0098] The aqueous corrosion protection formulation can be applied to a metal surface in a conventional manner, e.g., by spraying, spatula, knife coating, brushing, rolling, or pouring. The volatile components of the aqueous formulation are then removed by drying. This process can be repeated one or more times if desired. The application rate is generally selected so that the dry film thickness (after removal of the volatile components) is 15 to 150 µm, and preferably 30 to 100 µm.

[0099] The aqueous formulations are used to treat the surfaces of iron, steel, zinc, zinc alloys, aluminum, or aluminum alloys as substrates for corrosion protection. The metallic, preferably grease-free, surfaces can be uncoated, coated with zinc, aluminum, or their alloys, hot-dip galvanized, electrogalvanized, sherardized, or pre-coated with primers.

[0100] In particular, these are the surfaces of iron, steel, zinc, zinc alloys, aluminum, or aluminum alloys. Steel can contain the usual alloy components known to those skilled in the art. These can be the surfaces of bodies consisting entirely of said metals or alloys. However, they can also be the surfaces of bodies coated with Zn, Zn alloys, Al, or Al alloys, whereby the bodies can consist of other materials, for example, other metals, alloys, polymers, or composite materials. In a preferred embodiment of the invention, these are steel surfaces or galvanized and / or aluminized steel surfaces.

[0101] Zinc or aluminum alloys are known to those skilled in the art. Typical components of zinc alloys include, in particular, Al, Pb, Si, Mg, Sn, Cu, or Cd. Typical components of aluminum alloys include, in particular, Mg, Mn, Si, Zn, Cr, Zr, Cu, or Ti. The term "zinc alloy" is intended to also include Al / Zn alloys in which Al and Zn are present in approximately equal amounts. The skilled person selects the type and quantity of alloy components depending on the desired application. Zn or aluminum coatings can be applied to steel, for example, by hot-dip galvanizing or sherardizing. If the component is immobile or the component geometry does not permit it, corresponding coatings can also be applied by thermal spraying (spray galvanizing, spray aluminizing).

[0102] By means of the aqueous polymer dispersions according to the invention, in particular the aqueous formulations according to the invention, metallic surfaces which are in contact with atmospheric air during use can advantageously be protected from corrosion, but they can also be surfaces which are in contact with water, soil or other corrosive media during use.

[0103] The metallic surfaces to be protected from corrosion by means of the aqueous polymer dispersions according to the invention, in particular the aqueous formulations according to the invention, can in principle be any desired surfaces. However, they are preferably the surfaces of metallic buildings or metal structures or the components required therefor. Metal structures or buildings are typically made of structural steel, such as steel girders, steel pipes, or steel sheets, and joined to form corresponding structures by riveting, welding, or screwing. In one embodiment of the invention, the coated articles can be immobile metallic structures such as, for example, buildings, bridges, power poles, tanks, containers, buildings, pipelines, power plants, chemical plants, ships, cranes, piles, sheet piling, valves, pipes, tanks, fittings, flanges, couplings, halls, roofs, and structural steel.In this embodiment, anti-corrosive coatings are typically applied in-situ by brushing or spraying. This can be either initial protection or a repair. Such anti-corrosive coatings dry and cure under atmospheric conditions, i.e., at ambient temperature and in the presence of air and normal humidity. The relative humidity can be any, but is preferably between 10 and 80%, and particularly preferably between 30 and 70%. Depending on the required level of protection, the corrosion protection of surfaces provided by anti-corrosive coatings is also referred to as light, medium, or heavy corrosion protection.

[0104] The invention will be explained by means of the following non-limiting examples. Examples Example 1 (Dispersion 1)

[0105] In a 2 l polymerization vessel equipped with dosing devices and temperature control, at 20 to 25 °C (room temperature) under nitrogen atmosphere 260,0 g deionized water, and 12,0 g a 25 wt.% aqueous solution of a phosphorus group-containing dispersing agent (Rhodafac ®< RS610 / A25) and heated to 90 °C with stirring. Upon reaching this temperature, 30.4 g of feed 1 were added, followed by 33.8 g of a 2.5 wt. % aqueous solution of ammonium peroxodisulfate over a period of 2 minutes, and then stirring was continued for a further 10 minutes at the above-mentioned temperature. Simultaneously with the addition of the ammonium peroxodisulfate solution, 32.6 g of a 5.3 wt. % aqueous solution of ammonia were continuously added at a constant flow rate over a period of 175 minutes.

[0106] After the ten-minute stirring time, the remainder of feed 1 was continuously metered in over 90 minutes at a constant flow rate while maintaining a temperature of 90 °C. Starting at the same time as the remaining feed of feed 1, 48.4 g of a 2.5 wt. % aqueous solution of ammonium peroxodisulfate were also continuously metered in over 90 minutes. The polymerization mixture was then allowed to react for a further 15 minutes at 90 °C. Feed 2 was then continuously metered in over 65 minutes at a constant flow rate while maintaining a temperature of 90 °C. Parallel to feed 2, 15.2 g of a 2.0 wt. % aqueous solution of ammonium peroxodisulfate were continuously metered in. After feed 2 was complete, the polymerization mixture was allowed to react for a further 20 minutes at 90 °C. The resulting aqueous polymer dispersion was then cooled to 75 °C and at the same time 10.1 g of a 10 wt.A 10% aqueous solution of tert-butyl hydroperoxide and, in a parallel feed, 9.9 g of a 6% aqueous solution of Brüggolit ®< FF6 M (reducing agent from Brüggemann GmbH & Co. KG) were continuously metered in over 10 minutes. The polymerization mixture was then stirred at 70 °C for 20 minutes, cooled to room temperature, and 1.2 g of a 5% aqueous solution of Acticid ®< MBS (biocide from Thor) were added while stirring. Inlet 1 (homogeneous mixture of):

[0107] 110,3 g deionized water, 12,0 g Rhodafac ®< RS610 / A25, 2,4 g a 30 wt.% aqueous solution of a fatty alcohol polyethylene oxide ether sulfate (Disponil ®< FES 993 from BASF SE), 196,9 g Styrene, 196,9 g 2-ethylhexyl acrylate, 18,2 g Sipomer ®< PAM-200, 14,1 g Methyl methacrylate, 22,4 g Acetoacetoxyethyl methacrylate, 6,2 g Acrylic acid Inlet 2 (homogeneous mixture of):

[0108] 42,4 g deionized water, 2,4 g Rhodafac ®< RS610 / A25, 0,6 g Disponil ®< FES 993, 12,1 g Styrene, 133,3 g n-butyl methacrylate

[0109] The resulting polymer dispersion was filtered through a 125 µm filter before further use, whereby a coagulum content of < 0.1 wt.% was determined.

[0110] The aqueous polymer dispersion obtained after filtration had a solids content of 50.1 wt.%. The weight-average particle diameter was determined to be 93 nm, and the fine coagulum content was determined to be 227 µg / g of aqueous polymer dispersion. The pH was determined to be 4.2 at the end of the first polymerization stage and 6.1 at the end of the second polymerization stage. The dispersion polymer had a glass transition temperature Tg 1< of -2.8 °C and a glass transition temperature Tg 2< of 16 °C.

[0111] The solids contents of the resulting aqueous polymer dispersions were generally determined by drying a defined amount of the aqueous polymer dispersion (approx. 0.8 g) to constant weight at 160 °C using a Mettler Toledo HR73 moisture analyzer. Two measurements were performed in each case. The value given in the examples corresponds to the average of these two measurements.

[0112] To determine the fine coagulum content, 3.0 g of the resulting aqueous polymer dispersion were diluted to 1500 g with deionized water. Using the Klotz PZG3 sample feeder, after pre-rinsing, 1000 g of the resulting diluted aqueous polymer dispersion were pumped through the Klotz LDS 2x2 sensor at room temperature in 2.5 minutes. In combination with the ABAKUS evaluation and control unit with PC connection, this resulted in the specified values, which correspond to the counted particles in the range 10–500 µm.

[0113] It is important to note that coagulum contents > 0.1 wt.% and fine coagulum contents > 1000 µg / g of aqueous polymer dispersion can lead to problems during filtration (e.g. due to filter blockage) and are generally associated with disadvantages when used in coating materials due to the occurrence of surface defects and / or imperfections in the coating.

[0114] The weight-average particle diameter was generally determined according to ISO 13321 using a Malvern High Performance Particle Sizer at 22 °C and a wavelength of 633 nm.

[0115] The pH value was generally determined using a calibrated pH electrode InPro ®< 325X from Mettler-Toledo GmbH.

[0116] The glass transition temperatures were generally determined according to DIN EN ISO 11357-2 (2013-09) using differential scanning calorimetry (DSC) at a heating rate of 20 K / min using a DSC Q2000 from TA Instruments. The center temperatures were used for the determination. Example 2 (Dispersion 2)

[0117] The preparation of Example 2 was carried out completely analogously to the preparation of Example 1 with the difference that in feed 1 the acrylic acid was replaced by the same amount of methacrylic acid.

[0118] The resulting polymer dispersion had a solids content of 50.1 wt.%. The weight-average particle diameter was 99 nm. The coagulum content was <0.1%, and the fine coagulum content was determined to be 336 µg / g. The dispersion polymer had a glass transition temperature Tg 1 of -3.5 °C and a glass transition temperature Tg 2 of 17 °C. Example 3 (Dispersion 3)

[0119] The preparation of Example 3 was carried out completely analogously to the preparation of Example 1 with the difference that feeds 1 and 2 had the following composition: Inlet 1 (homogeneous mixture of):

[0120] 110,3 g deionized water, 12,0 g Rhodafac ®< RS610 / A25, 2,4 g Disponil ®< FES 993, 168,6 g Styrene, 176,5 g 2-ethylhexyl acrylate, 13,1 g Sipomer ®< PAM-200, 73,1 g Methyl methacrylate, 6,0 g Acetoacetoxyethyl methacrylate, 6,7 g Acrylic acid Inlet 2 (homogeneous mixture of):

[0121] 42,4 g deionized water, 2,4 g Rhodafac ®< RS610 / A25, 0,6 g Disponil ®< FES 993, 72,6 g Styrene, 52,4 g n-butyl methacrylate, 8,8 g Methyl methacrylate, 22,2 g 2-Ethylhexyl acrylate

[0122] The resulting polymer dispersion had a solids content of 49.7 wt.%. The weight-average particle diameter was determined to be 121 nm, the coagulum content to be <0.1 wt.%, and the fine coagulum content to be 507 µg / g. The determined glass transition temperatures Tg 1< and Tg 2< were 6 °C and 23 °C, respectively. Example 4 (Dispersion 4)

[0123] In a 2 l polymerization vessel equipped with dosing devices and temperature control, at 20 to 25 °C (room temperature) under nitrogen atmosphere 339,0 g deionized water, and 10,3 g from Rhodafac ®< RS610 / A25 and heated to 90 °C with stirring. Upon reaching this temperature, 30.4 g of feed 1 were added, followed by 33.8 g of a 2.2 wt. % aqueous solution of ammonium peroxodisulfate over a period of 2 minutes, and then stirring was continued for a further 10 minutes at the above-mentioned temperature. Simultaneously with the addition of the ammonium peroxodisulfate solution, 40.5 g of a 4.6 wt. % aqueous solution of ammonia were continuously added at a constant flow rate over a period of 175 minutes.

[0124] After the ten-minute stirring time, the remainder of feed 1 was continuously added at a constant flow rate over 90 minutes while maintaining a temperature of 90 °C. Starting simultaneously with the remaining feed of feed 1, 52.8 g of a 2.4 wt. % aqueous solution of ammonium peroxodisulfate were also continuously added over 90 minutes. The polymerization mixture was then allowed to react for a further 15 minutes at 90 °C. Feed 2 was then continuously added at a constant flow rate over 65 minutes while maintaining a temperature of 90 °C. Parallel to feed 2, 15.2 g of a 2.0 wt. % aqueous solution of ammonium peroxodisulfate were continuously added. After feed 2 was complete, the polymerization mixture was allowed to react for a further 20 minutes at 90 °C. The resulting aqueous polymer dispersion was then cooled to 75 °C and at the same time 16.2 g of a 6.8 wt.A 10% aqueous solution of tert-butyl hydroperoxide and, in a parallel feed, 16.0 g of a 4% w / w aqueous solution of Brüggolit ®< FF6 M were continuously added over 10 minutes. The polymerization mixture was then stirred at 70 °C for 20 minutes, cooled to room temperature, and 14.7 g of a 0.4% w / w aqueous solution of Acticid ®< MBS were added while stirring. Inlet 1 (homogeneous mixture of):

[0125] 79,7 g deionized water, 12,9 g Rhodafac ®< RS610 / A25, 2,6 g Disponil ®< FES 993, 208,5 g Styrene, 208,5 g 2-ethylhexyl acrylate, 19,5 g Sipomer ®< PAM-200, 15,2 g Methyl methacrylate, 24,1 g Acetoacetoxyethyl methacrylate, 6,7 g Acrylic acid 6,5 g Vinyltriethoxysilane Inlet 2 (homogeneous mixture of):

[0126] 33,5 g deionized water, 2,6 g Rhodafac ®< RS610 / A25, 0,7 g Disponil ®< FES 993, 13,0 g Styrene, 143,3 g n-butyl methacrylate

[0127] The resulting polymer dispersion was filtered through a 125 µm filter before further use, whereby a coagulum content of < 0.1 wt.% was determined.

[0128] The aqueous polymer dispersion obtained after filtration had a solids content of 49.8 wt.%. The weight-average particle diameter was determined to be 98 nm, and the fine coagulum content was determined to be 203 µg / g of aqueous polymer dispersion. The pH was determined to be 4.1 at the end of the first polymerization stage and 6.0 at the end of the second polymerization stage. The dispersion polymer had a glass transition temperature Tg 1< of -5.4 °C and a glass transition temperature Tg 2< of 13 °C. Example 5 (Dispersion 5)

[0129] The preparation of Example 5 was carried out completely analogously to the preparation of Example 1 with the difference that 32.6 g of a 5.3 wt.% aqueous solution of sodium hydroxide were used instead of ammonia.

[0130] The aqueous polymer dispersion obtained after filtration had a solids content of 50.2 wt.%. The weight-average particle diameter was determined to be 106 nm, the coagulum content to be <0.1 wt.%, and the fine coagulum content to be 373 µg / g of aqueous polymer dispersion. The pH was determined to be 4.0 at the end of the first polymerization stage and 5.9 at the end of the second polymerization stage. The dispersion polymer had a glass transition temperature Tg 1 < of -2.3 °C and a glass transition temperature Tg 2 < of 15.7 °C. Example 6 (Dispersion 6)

[0131] The preparation of Example 6 was carried out completely analogously to the preparation of Example 1 with the difference that 32.6 g of a 5.3 wt.% aqueous solution of trimethylamine were used instead of ammonia.

[0132] The aqueous polymer dispersion obtained after filtration had a solids content of 49.9 wt.%. The weight-average particle diameter was determined to be 98 nm, the coagulum content to be <0.1 wt.%, and the fine coagulum content to be 308 µg / g of aqueous polymer dispersion. The pH was determined to be 4.5 at the end of the first polymerization stage and 6.2 at the end of the second polymerization stage. The dispersion polymer had a glass transition temperature Tg 1 < of -2.1 °C and a glass transition temperature Tg 2 < of 16.5 °C. Comparison example 1

[0133] The preparation of Comparative Example 1 was carried out completely analogously to the preparation of Example 1 with the difference that feed 1 did not contain any Sipomer ®< PAM-200 and feed 2 additionally contained 18.2 g of Sipomer ®< PAM-200.

[0134] The polymerization mixture coagulated during feed 1, so the experiment had to be stopped. Comparison example 2

[0135] The preparation of Comparative Example 2 was carried out completely analogously to the preparation of Example 1 with the difference that feed 1 did not contain acrylic acid and feed 2 additionally contained 6.2 g of acrylic acid.

[0136] The polymerization mixture coagulated during feed 1, so the experiment had to be stopped. Comparison example 3

[0137] The preparation of Comparative Example 3 was carried out completely analogously to the preparation of Example 1 with the difference that 25.8 g of Disponil ®< FES 993 were used in the initial charge instead of 12.0 g of Rhodafac ®< RS610 / A25, a total of 28.1 g of Disponil ®< FES 993 were used in feed 1 and a total of 5.7 g of Disponil ®< FES 993 were used in feed 2 and in each case no Rhodafac ®< RS610 / A25 was used.

[0138] The polymerization mixture coagulated during feed 1, so the experiment had to be stopped. Comparison example 4

[0139] The preparation of Comparative Example 4 was carried out completely analogously to the preparation of Example 1 with the difference that no 5.3 wt.% aqueous solution of ammonia was used, whereby the polymerization batch coagulated in the first polymerization stage at a pH of 2.3, so that the experiment had to be discontinued. Comparative Example 5 (Comparative Dispersion V5)

[0140] The preparation of Comparative Example 5 was carried out completely analogously to the preparation of Example 1 with the difference that 16.3 g instead of 32.6 g of a 5.3 wt.% aqueous solution of ammonia were used.

[0141] The aqueous polymer dispersion obtained after filtration had a solids content of 50.1 wt.%. The weight-average particle diameter was determined to be 90 nm, the coagulum content to be <0.1 wt.%, and the fine coagulum content to be 689 µg / g of aqueous polymer dispersion. The pH was determined to be 2.9 at the end of the first polymerization stage and 5.3 at the end of the second polymerization stage. The dispersion polymer had a glass transition temperature Tg 1 < of -2.8 °C and a glass transition temperature Tg 2 < of 15 °C. Comparative Example 6 (Comparative Dispersion V6)

[0142] The preparation of Comparative Example 6 was carried out completely analogously to the preparation of Example 1 with the difference that 48.9 g of a 5.3 wt.% aqueous solution of ammonia were used instead of 32.6 g.

[0143] The aqueous polymer dispersion obtained after filtration had a solids content of 49.8 wt.%. The weight-average particle diameter was determined to be 96 nm, the coagulum content to be 0.2 wt.%, and the fine coagulum content to be 1083 µg / g of aqueous polymer dispersion. The pH was determined to be 4.9 at the end of the first polymerization stage and 7.3 at the end of the second polymerization stage. The dispersion polymer had a glass transition temperature Tg 1< of -2.0 °C and a glass transition temperature Tg 2< of 15 °C. Comparative Example 7 (Comparative Dispersion V7)

[0144] In a 2 l polymerization vessel equipped with dosing devices and temperature control, at room temperature under nitrogen atmosphere 260,0 g deionized water, and 12,0 g from Rhodafac ®< RS610 / A25

[0145] and heated to 90 °C with stirring. Upon reaching this temperature, 30.4 g of feed 1 were added, followed by 33.8 g of a 2.5 wt. % aqueous solution of ammonium peroxodisulfate over a period of 2 minutes, and then stirring was continued for a further 10 minutes at the above-mentioned temperature. Simultaneously with the addition of the ammonium peroxodisulfate solution, 32.6 g of a 5.3 wt. % aqueous solution of ammonia were continuously added at a constant flow rate over a period of 175 minutes.

[0146] After the ten-minute stirring time, the remainder of feed 1 was continuously metered in at a constant flow rate over 175 minutes while maintaining a temperature of 90 °C. Starting simultaneously with the remaining feed of feed 1, 60.7 g of a 2.5 wt. % aqueous solution of ammonium peroxodisulfate were also continuously metered in over 170 minutes. After feed 1 had been added, the polymerization mixture was allowed to react for a further 20 minutes at 90 °C. The resulting aqueous polymer dispersion was then cooled to 75 °C, and simultaneously, 10.1 g of a 10 wt. % aqueous solution of tert-butyl hydroperoxide and, in a parallel feed, 9.9 g of a 6 wt. % aqueous solution of Brüggolit ®< FF6 M were continuously metered in over 10 minutes. The polymerization mixture was then stirred at 70 °C for 20 minutes, cooled to room temperature and treated with 1.2 g of 5 wt.-% aqueous solution of Acticid ®< MBS. Inlet 1 (homogeneous mixture of):

[0147] 152,7 g deionized water, 14,4 g Rhodafac ®< RS610 / A25, 3,0 g Disponil ®< FES 993, 209,0 g Styrene, 196,9 g 2-ethylhexyl acrylate, 18,2 g Sipomer ®< PAM-200, 14,1 g Methyl methacrylate, 133,3 g n-butyl methacrylate 22,4 g Acetoacetoxyethyl methacrylate, 6,2 g Acrylic acid

[0148] The aqueous polymer dispersion obtained after filtration had a solids content of 50.0 wt.%. The weight-average particle diameter was determined to be 98 nm, the coagulum content to be <0.1 wt.%, and the fine coagulum content to be 467 µg / g of aqueous polymer dispersion. The pH of the aqueous polymer dispersion was determined to be 5.1. The dispersion polymer had a glass transition temperature Tg of 14 °C. Comparative Example 8 (Comparative Dispersion V8)

[0149] The preparation of Comparative Example 8 was carried out completely analogously to the preparation of Example 1 with the difference that in feed 1 96.9 g instead of 196.9 g of styrene and 296.9 g instead of 196.9 g of 2-ethylhexyl acrylate were used.

[0150] The aqueous polymer dispersion obtained after filtration had a solids content of 49.5 wt.%. The weight-average particle diameter was determined to be 127 nm with a second fraction at 880 nm, the coagulum content to be 1 wt.%, and the fine coagulum content to be 8744 µg / g of aqueous polymer dispersion. The pH was determined to be 4.2 at the end of the first polymerization stage and 6.7 at the end of the second polymerization stage. The dispersion polymer had a glass transition temperature Tg 1 of -32 °C and a glass transition temperature Tg 2 of -8 °C. Application-related studies

[0151] For the performance tests, a clearcoat and a pigmented anti-corrosive coating were prepared from the aqueous polymer dispersions obtained in the examples and the comparative examples. For this purpose, polymer dispersions 1 to 6 and V5 to V8 were first diluted with deionized water to a solids content of 49.5 wt. %. Production of clear coats

[0152] The clearcoats were prepared by adjusting 96.0 g of each of the aqueous polymer dispersions 1 to 6 and V5 to V8, diluted to 49.5 wt. %, to a pH of 9.5 with a 50 wt. % aqueous solution of dimethylethanolamine from Huntsman Corporation at room temperature while stirring. Subsequently, 3 g of the organic solvent Texanol ®< from Eastman Chemical and 1 g of the corrosion inhibitor CHE ®< -COAT-CI LNF A4 from CH Erbslöh KG were added and mixed homogeneously. The resulting clearcoats are referred to below as clearcoats 1 to 6 and V5 to V8. Early water test

[0153] The clear coats 1 to 6 and V5 to V8 to be tested were each applied to the surface of a 200 x 80 mm cleaned and grease-free, ungalvanized steel sheet using a box-type doctor blade. The gap size was selected to result in a dry film thickness of 40 to 85 µm. The coated steel sheets (hereinafter referred to as steel sheets 1 to 6 and V5 to V8) were each dried for two hours at 23 °C and 50% relative humidity in a climate chamber. The actual test was then carried out by placing the steel sheets 1 to 6 and V5 to V8 vertically in a water bath filled with deionized water to a height of 15 cm at room temperature for 24 hours.Subsequently, steel sheets 1 to 6 and V5 to V8 were removed from the water bath, dabbed dry with a soft cotton cloth, and the respective color change between the wetted and the non-wetted area was assessed. The color change was visually assessed using the following scale: 0 (no change) to 5 (significant color change across the entire area). The results obtained are listed in Table 1 below. Table 1: Results of the early water test sheet steel Evaluation 1 0 2 0 3 0 4 1 5 1 6 0 V5 4 V6 2 V7 2 V8 3

[0154] Production of pigmented anti-corrosive paints

[0155] 167.9 g of the aqueous polymer dispersions 1 to 6 and V5 to V8, diluted to 49.5 wt. %, were each admixed at room temperature with 1.5 g of the commercially available defoamer for coatings, BYK ®< 022 (Byk GmbH; a mixture of polysiloxanes and hydrophobic solids in polyglycol). Subsequently, 15.0 g of deionized water, 1.0 g of 25 wt. % aqueous ammonia solution, 1.5 g of Dispex ®< Ultra PA4570 (BASF SE; a dispersing additive based on modified polyacrylate), and 4.5 g of Dispex ®< CX 4231 (BASF SE; a dispersing additive based on an ammonium salt of an organic acid copolymer in water) were added using a Dispermat. A mixture of 2.2 g of phenoxypropanol (film-forming agent) and 2.2 g of gasoline (boiling range 180 to 210 °C; film-forming agent) was also incorporated while stirring. Subsequently, 25.5 g of the hematite pigment Bayferrox®< 130 M (Lanxess AG) and 10.8 g of talc 20 M 2 (Lanxess AG) were added.Luzenac; filler: magnesium silicate), 38.3 g of Litopone®< L (Sachtleben, filler based on barium sulfate and zinc sulfide), and 24.6 g of Heucophos®< ZMP (Heubach, corrosion protection pigment based on zinc phosphate) were added. A further 0.8 g of BYK®< 022 and 1.1 g of a 1:1 mixture of water and corrosion inhibitor L 1 (CH Erbslöh KG) were then added. The entire mixture was premixed for 10 minutes in a dissolver using a toothed disk (diameter 5 cm; 2000 revolutions per minute) and then dispersed for 20 minutes using a double Teflon disk (diameter 5 cm; 2300 revolutions per minute) and 200 g of glass beads (diameter 3 mm). The glass beads were then sieved off. Finally, the respective batches were thickened with 1.8 g of 25 wt.% aqueous ammonia solution and a mixture of 0.3 g of a 25 wt.% aqueous solution of a commercially available urethane-based thickener (Rheovis ®< PU 1280, Fa.BASF SE) and 1.0 g of butylglycol (solvent), and if necessary, the pH was adjusted to 9.5 with a 25 wt.% aqueous ammonia solution. The resulting corrosion protection formulations 1 to 6 and V5 to V8 had a solids content of 61 wt.% and a pigment / volume concentration of 23%. The resulting corrosion protection formulations were diluted with deionized water to a viscosity of approximately 300 mPas (determined at room temperature using a Rotothinner 455N ball from Sheen Instruments), and the respective solids contents were determined.

[0156] What is important in this context is that the corrosion protection formulation V6 thickened immediately after its production, so that this formulation could not be used to coat a steel sheet. Salt spray test

[0157] To test the corrosion protection properties, a salt spray test was conducted in accordance with DIN EN ISO 7253 (with a test duration of 360 hours) using a 5 wt.% aqueous sodium chloride solution. For this purpose, the diluted corrosion protection formulations 1 to 6 as well as V5, V7, and V8 were each applied to one side of a 200 x 80 mm cleaned, ungalvanized steel sheet using a box-type doctor blade, with the gap size selected to result in a dry film thickness of 60 to 100 µm. The test sheets obtained after coating were stored for 6 days in a climate chamber at 23 °C and 50% relative humidity, where they were dried. The coated test sheets were then stored for a further 24 hours at a temperature of 50 °C. After cooling to room temperature, the backs of the respective test sheets were coated with a solvent-based paint to protect against corrosion and then dried at room temperature for 24 hours.Before the actual test, the edges of the respective test panels were taped with plastic film. The coated side of the test panels was then scratched down to the steel with a scratching spike and sprayed with salt water for 360 hours. The evaluation of the resulting test panels (V5, V7, and V8) was carried out by visually comparing the tested samples with the standards specified by DIN EN ISO 7253. The corrosion behavior of the individual test panels was assessed based on the rust formation at the scratch, surface corrosion, and adhesion using a cross-cut test as follows: Under-rusting at the scribe (analogous to DIN EN ISO 4628-8; 2013):

[0158] Starting at the artificially damaged areas, rust formed beneath the coatings. The values ​​given in Table 2 indicate the maximum distance in mm of the iron oxide formed, measured from the cracks. Before sampling, the loose coatings around the cracks were removed using adhesive tape. According to the invention, the lower the measured values, the better they are evaluated. Surface corrosion:

[0159] The assessment was performed by visually assessing the proportion of corroded area relative to the total area of ​​the test panels. The values ​​given in Table 2 represent the percentage of corroded areas. The lower the measured values, the better the assessment. Adhesion (cross-cut according to DIN EN ISO 2409):

[0160] The adhesion of the corrosion protection coatings to the substrate was determined using the cross-cut test. Following the salt spray test, a grid of multiple cuts (2 mm spacing) was cut into the respective dry, dabbed corrosion protection coating, covered with adhesive tape, and then the tape was removed. The appearance of the grid was evaluated after the tape was removed. Grades from 0 to 5 were awarded according to the following scale: Gt 0 The cut edges were completely smooth and none of the grid squares had chipped off. Gt 1 The coating had chipped off along the cut edges, but the chipped area was no larger than 15% of the grid cut area. Gt 2 The chipped grid area was larger than 15% but not larger than 35%. Gt 3 The coating had chipped off partially or completely in wide strips along the cut edges or some squares were completely or partially chipped off. Gt 4 The affected grid cut area was larger than 35% but not larger than 65%. Gt 5 Any chipping that could be classified as more severe than GT 4.

[0161] The results obtained are also listed in Table 2 below. Table 2: Results of the salt spray test test sheet Under-rust at the scribe mark [in mm] Surface corrosion [in %] Cross-hatch 1 5 <5 Gt0 2 8 <5 GT1 3 6 <5 Gt0 4 2 <5 Gt0 5 9 5 GT1 6 7 <5 Gt0 V5 20 15 GT2 V7 10 10 GT1 V8 15 20 GT5 Determination of film hardness

[0162] The film hardness was determined using the König pendulum damping test in accordance with DIN EN ISO 1522. The test was carried out by applying the diluted corrosion protection formulations 1 to 6, as well as V5, V7, and V8, to one side of a 200 x 80 mm cleaned, ungalvanized steel sheet using a box-type doctor blade. The gap size was selected to result in a dry film thickness of 60 to 100 µm. The coated test sheets were then stored in a drying cabinet at 50 °C for 20 hours and subsequently cooled to room temperature. The König pendulum damping test in accordance with DIN EN ISO 1522 was then carried out on the coated steel sheets obtained in this way. The results obtained from testing the steel sheets coated with corrosion protection formulations 1 to 6, as well as V5, V7, and V8, are listed in Table 3.The higher the number of pendulum impacts, the harder the coating is to be considered. Table 3: Film hardness results sheet steel Number of pendulum strokes 1 17 2 18 3 30 4 22 5 17 6 16 V5 15 V7 8 V8 5

[0163] The results of the application-technical investigations clearly show that the coatings produced with the polymer dispersions according to the invention exhibit significantly better values ​​with regard to under-rusting at the scratch, surface corrosion, cross-cut and film hardness than the corrosion protection formulations produced with the corresponding comparison dispersions.

Claims

1. A process for producing an aqueous polymer dispersion by free-radically initiated aqueous emulsion polymerization, wherein in an aqueous medium in the presence of at least one phosphorus group-containing dispersing aid in a first polymerization stage (polymerization stage 1) ≥ 1.0% and ≤ 3.0% weightbyof at least one α,β-monoethylenically unsaturated C3- to C6-mono- or -dicarboxylic acid (monomers A1),≥ 1.5% and ≤ 6.0% weightbyof at least one ethylenically unsaturated compound having at least one phosphorus-containing group (monomers A2),≥ 91.0% and ≤ 97.5% weightbyof at least one ethylenically unsaturated compound distinct from the monomers A1 and A2 (monomers A3), wherein the amounts of the monomers A1 to A3 sum to 100% by weight (total monomer amount 1), are free-radically polymerized to afford a polymer 1 and subsequently in the presence of the polymer 1 in a second polymerization stage (polymerization stage 2) ≤ 0.1% by weightof at least one α,β-monoethylenically unsaturatedC3- to C6-mono- or -dicarboxylic acid (monomers B1),≤ 0.1% by weightof at least one ethylenically unsaturated compound having at least one phosphorus-containing group (monomers B2),≥ 99.8% and ≤ 100% weightbyof at least one ethylenically unsaturated compound distinct from the monomers B1 and B2 (monomers B3), wherein the amounts of the monomers B1 to B3 sum to 100% by weight (total monomer amount 2), are free-radically polymerized to afford a polymer 2 with the proviso that • the type and amounts of the monomers A1 to A3 are chosen such that the resulting polymer 1 has a glass transition temperature Tg1 in the range ≥ -10°C and ≤ 15°C measured as described in the description, • the type and amounts of the monomers B1 to B3 are chosen such that the resulting polymer 2 has a glass transition temperature Tg2 which is at least 10°C above the glass transition temperature Tg1 [Tg2 = Tg1 + ≥ 10 °C] measured as described in the description, • the ratio of total monomer amount 1 to total monomer amount 2 is 70% to 85% by weight to 15% to 30% by weight and • the amount of the at least one phosphorus group-containing dispersant is ≥ 0.5% by weight based on the sum of total monomer amount 1 and total monomer amount 2 (total monomer amount).

2. The process according to claim 1, wherein the monomers A1 employed are acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid and / or crotonic acid.

3. The process according to either of claims 1 and 2, wherein the monomers A2 employed are vinylphosphonic acid and / or a (meth)acryloxy(poly)alkoxy phosphate.

4. The process according to any of claims 1 to 3, wherein the at least one monomer A3 is to an extent of ≥ 80% by weight selected from the group comprising n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, styrene and methyl methacrylate.

5. The process according to any of claims 1 to 4, wherein the type and amounts of the monomers A1 to A3 and B1 to B3 are chosen such that the obtained polymer 1 has a glass transition temperature Tg1 in the range ≥ -5°C and ≤ 10°C and the obtained polymer 2 has a glass transition temperature Tg2 in the range ≥ 10°C and ≤ 40°C.

6. The process according to any of claims 1 to 5, wherein no monomers B1 and B2 whatsoever are employed.

7. The process according to any of claims 1 to 6, wherein the polymerization stages 1 and 2 are performed at a pH in the range ≥ 3 and ≤ 8 measured at room temperature.

8. The process according to claim 7, wherein the pH adjustment is carried out with a base having a boiling point ≤ 20°C measured at 1.013 bar (absolute).

9. The process according to any of claims 1 to 6, wherein the at least one monomer A3 is to an extent of > 0% and ≤ 20% by weight selected from the group comprising 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-(acetoacetoxy)ethyl methacrylate, 2-ureidoethyl methacrylate, diacetone acrylamide, glycidyl methacrylate, 3-(methacryloyloxy)propyltrimethoxysilane, vinyltriethoxysilane, allyl methacrylate and 1,4-butanediol diacrylate.

10. An aqueous polymer dispersion obtainable by a process according to any of claims 1 to 9.

11. A polymer powder obtainable by drying an aqueous polymer dispersion according to claim 10.

12. The use of an aqueous polymer dispersion according to claim 10 or of a polymer powder according to claim 11 as a binder in the production of adhesives, sealants, synthetic resin renders, paper coating slips, fiber nonwovens, flexible roof coatings and paints and also in sand consolidation, as a component in the production of textile or leather auxiliaries and impact modifiers or for modification of mineral binders and plastics.

13. The use of an aqueous polymer dispersion according to claim 10 or of a polymer powder according to claim 11 as a binder in aqueous anticorrosion formulations for metal surfaces.

14. A process for coating metal surfaces, wherein an aqueous anticorrosion formulation comprising an aqueous polymer dispersion according to claim 10 or a polymer powder according to claim 11 is applied to the metal surface and subsequently dried.

15. An aqueous anticorrosion formulation comprising an aqueous polymer dispersion according to claim 10 or a polymer powder according to claim 11.