aqueous polymer dispersion

Abstract

The present invention relates to aqueous polymer dispersions containing phosphorus groups and their use as binders in coating formulations.

Description

[0001] The present invention relates to a process for preparing an aqueous polymer dispersion by free-radical-initiated aqueous emulsion polymerization, wherein in a first polymerization stage (polymerization stage 1), the following substances are subjected to free-radical polymerization in an aqueous medium in the presence of at least one phosphorus-containing dispersion aid to provide polymer 1:

[0002] At least one α,β-monoethylenically unsaturated C3- to C6-monocarboxylic or dicarboxylic acid (monomer A1) in an amount of ≥1.0% by weight and ≤3.0% by weight,

[0003] At least one ethylenically unsaturated compound having at least one phosphorus-containing group (monomer A2) in an amount of ≥1.5% by weight and ≤6.0% by weight,

[0004] At least one ethylenically unsaturated compound different from monomers A1 and A2 (monomer A3) in an amount of ≥91.0% by weight and ≤97.5% by weight,

[0005] wherein the amounts of monomers A1 to A3 together total 100% by weight (total monomer amount 1),

[0006] and

[0007] subsequently, in a second polymerization stage (polymerization stage 2), the following substances are subjected to free-radical polymerization in the presence of polymer 1 to provide polymer 2:

[0008] At least one α,β-monoethylenically unsaturated C3- to C6-monocarboxylic or dicarboxylic acid (monomer B1) in an amount of ≤0.1% by weight,

[0009] At least one ethylenically unsaturated compound having at least one phosphorus-containing group (monomer B2) in an amount of ≤0.1% by weight,

[0010] At least one ethylenically unsaturated compound different from monomers B1 and B2 (monomer B3) in an amount of ≥99.8% by weight and ≤100% by weight,

[0011] wherein the amounts of monomers B1 to B3 together total 100% by weight (total monomer amount 2),

[0012] provided that

[0013] · The type and amount of monomers A1 to A3 are selected such that the glass transition temperature Tg of the resulting polymer 1 1 is in the range of ≥ -10°C and ≤15°C,

[0014] · The type and amount of monomers B1 to B3 are selected such that the glass transition temperature Tg of the resulting polymer 2 2 is at least 10°C higher than the glass transition temperature Tg 1 [Tg 2 = Tg1

[0015] +≥10 °C],

[0016] · The ratio of total monomer amount 1 to total monomer amount 2 is 70 wt% to 85 wt% to 15 wt% to 30 wt%, and

[0017] · The amount of said at least one phosphorus-containing dispersant is ≥ 0.5 wt%, based on the sum of total monomer amount 1 and total monomer amount 2 (total monomer amount).

[0018] The present invention also relates to an aqueous polymer dispersion obtainable by this method and its use in a very wide range of fields, especially in anticorrosive coatings.

[0019] The multi-stage phosphorus-containing aqueous polymer dispersion starts from the following related prior art.

[0020] EP-A 1193298 discloses an aqueous polymer dispersion, the polymer of which contains monomers having strong acid groups in copolymerized form, where strong acid groups are to be understood as meaning those groups having a pKa value < 4 at 20 °C, such as sulfonic acid groups or phosphoric acid groups. These polymers may also optionally contain minor amounts of carboxylic acid monomers in copolymerized form. The polymerization reaction is carried out under strongly acidic conditions. Any required neutralization reaction is carried out only after the polymerization reaction. The aqueous polymer dispersion thus obtained is advantageously suitable as a binder in anticorrosive preparations and high-gloss coatings.

[0021] EP-A 2426155 discloses a dispersion of a multi-stage dispersion polymer containing phosphorus-containing monomers in copolymerized form and its use in coating formulations. The characteristic feature of the preparation of the dispersion polymer is the pulsed addition of the phosphorus-containing monomer, where the pulsed addition is carried out such that 75 wt% to 100 wt% of the said phosphorus-containing monomer is added during the period of adding 10 wt% to 50 wt% of the total monomer amount. Here, the polymerization reaction is also carried out under strongly acidic conditions. Any required neutralization reaction is carried out only after the polymerization reaction. It is said that the polymer dispersion particles thus obtained are advantageously suitable for adsorption on titanium dioxide particles, and thus they are particularly used in coating formulations containing titanium dioxide.

[0022] The disadvantages of the above methods are that industrially commonly used stainless steel polymerization reactors are not suitable for polymerization reactions in strongly acidic media due to surface corrosion and local pitting corrosion, and thus for this purpose, special and expensive internally coated polymerization reactors or titanium polymerization reactors become necessary. In addition, in the case of additionally using functional monomers in the polymerization reaction, the obtained aqueous polymer dispersion is unstable and has a tendency to increase the formation of condensates or even coagulation. Furthermore, aqueous anticorrosive coatings containing the aqueous polymer dispersion obtained by the above method as a binder are not entirely convincing in all respects.

[0023] Accordingly, the object of the present invention is to provide a process for preparing an aqueous dispersion of a phosphorus-containing dispersion polymer, which can be carried out in a polymerization reactor commonly used industrially, wherein the obtained aqueous polymer dispersion is stable and has a low content of fine coagulates, and when used in an anticorrosive coating, also exhibits improved early water resistance, reduced surface corrosion, reduced subsurface corrosion starting from scratches, and improved adhesion properties.

[0024] This object is achieved by the process defined at the beginning and by the aqueous polymer dispersion obtainable by this process.

[0025] The free-radical-initiated emulsion polymerization reaction of ethylenically unsaturated compounds (monomers) in an aqueous medium has been widely described and is thus well known to the person skilled in the art [in this regard, see Emulsionspolymerisation [Emulsion Polymerization] in Encyclopedia of Polymer Science and Engineering, Vol. 8, pages 659 et seq., (1987); D.C. Blackley, in High Polymer Latices, Vol. 1, pages 35 et seq., (1966); H. Watson, The Applications of Synthetic Resin Emulsions, Chapter 5, pages 246 et seq., (1972); D. Diederich, Chemie in unserer Zeit 24, pages 135 to 142 (1990); Emulsion Polymerisation, Interscience Publishers, New York (1965); DE-A 4003 422 and Dispersionen synthetischer Hochpolymerer [Dispersions of Synthetic HighPolymers], F. Springer-Verlag, Berlin (1969). The free-radical-initiated aqueous emulsion polymerization reaction is usually carried out as follows: monomers (usually including dispersion aids such as emulsifiers and / or protective colloids) are dispersed in an aqueous medium, and at least one water-soluble free-radical polymerization initiator is used to polymerize them. Generally, it is also known to those skilled in the art to use chemical methods and / or physical methods to reduce the residual content of unreacted monomers in the resulting aqueous polymer dispersion [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], to adjust the polymer solids content to the desired value by dilution or concentration, or to add other conventionally added substances to the aqueous polymer dispersion, such as foam-modifying or viscosity-modifying additives. The method of the present invention differs from this general method only in that the method of the present invention is carried out in two stages, while observing the stated limiting parameters and specific monomer composition and specific pH management.

[0026] The aqueous polymer dispersions obtainable by the method of the present invention can be prepared by a two-stage aqueous emulsion polymerization reaction using the following ethylenically unsaturated monomers A1, A2, A3, B1, B2 and B3.

[0027] The monomers A1 which can be used include any α,β-monoethylenically unsaturated C3- to C6-monocarboxylic or dicarboxylic acids. Examples of C3- to C6-monocarboxylic or dicarboxylic acids, preferably C3- or C4-monocarboxylic or dicarboxylic acids, are acrylic acid, methacrylic acid, ethylacrylic acid, itaconic acid, allylacetic acid, crotonic acid, vinylacetic acid, vinyl lactic acid, fumaric acid, maleic acid, 2-methylmaleic acid. However, the monomers A1 also include the anhydrides of the corresponding α,β-monoethylenically unsaturated dicarboxylic acids, such as maleic anhydride or 2-methylmaleic anhydride.

[0028] Particularly preferably used monomers A1 are acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid and / or crotonic acid.

[0029] The total amount of monomers A1 is ≥1.0% by weight and ≤3.0% by weight, advantageously ≥1.0% by weight and ≤2.0% by weight and particularly advantageously ≥1.1% by weight and ≤1.8% by weight, in each case based on the total monomer amount 1.

[0030] The monomer A2 considered includes any ethylenically unsaturated compound having at least one phosphorus-containing group. Examples thereof are vinylphosphonic acid and / or (meth)acryloyloxy(poly)alkoxy phosphates, where the (meth)acryloyloxy(poly)alkoxy phosphates have the following formula I:

[0031] H2C=CH(H / CH3)-C(=O)-[AO] x -O-P(=O)(-OH)2, formula (I)

[0032] where

[0033] AO: represents ethenoxy [-OCH2CH2-], propenoxy [-OCH(CH3)CH2-], butenoxy [-OCH(C2H5)CH2-] or a mixture thereof, where ethenoxy and / or propenoxy are preferred, and

[0034] x: represents a number between 1 and 30, where a number between 1 and 20 is preferred and a number between 1 and 10 is very particularly preferred.

[0035] Specifically mentioned (meth)acryloyloxy(poly)alkoxy phosphates are compounds of the following formula:

[0036] H2C=CH-C(=O)-OCH2CH2-O-P(=O)(-OH)2

[0037] H2C=CH-C(=O)-OCH(CH3)CH2-O-P(=O)(-OH)2

[0038] H2C=C(CH3)-C(=O)-OCH2CH2-O-P(=O)(-OH)2

[0039] H2C=C(CH3)-C(=O)-OCH(CH3)CH2-O-P(=O)(-OH)2

[0040] H2C=CH-C(=O)-[OCH2CH2] 4-7 -O-P(=O)(-OH)2

[0041] H2C=CH-C(=O)-[OCH(CH3)CH2] 4-7 -O-P(=O)(-OH)2

[0042] H2C=C(CH3)-C(=O)-[OCH2CH2] 4-7 -O-P(=O)(-OH)2

[0043] H2C=C(CH3)-C(=O)-[OCH(CH3)CH2] 4-7-O-P(=O)(-OH)2

[0044] and particularly preferably

[0045] H2C=C(CH3)-C(=O)-[OCH2CH2] 4-7 -O-P(=O)(-OH)2

[0046] H2C=C(CH3)-C(=O)-[OCH(CH3)CH2] 4-7 -O-P(=O)(-OH)2

[0047] H2C=CH-C(=O)-[OCH(CH3)CH2] 4-7 -O-P(=O)(-OH)2

[0048] H2C=CH-C(=O)-OCH2CH2-O-P(=O)(-OH)2

[0049] H2C=C(CH3)-C(=O)-OCH2CH2-O-P(=O)(-OH)2

[0050] The above-mentioned preferred (meth)acryloyloxy(poly)alkoxy phosphates are commercially available, for example as PAM-100 from Solvay / Rhodia, PAM-100, PAM-200, PAM-300 or PAM-4000, and ethyl 2-(methacryloyloxy)phosphate from Sigma-Aldrich / Merck KGaA.

[0051] Of course, monomers A1 and A2 also include the completely or partially neutralized water-soluble salts of the above acids, especially alkali metal salts or ammonium salts.

[0052] The total amount of monomer A2 is ≥ 1.5% by weight and ≤ 6.0% by weight, advantageously ≥ 1.5% by weight and ≤ 5.0% by weight and particularly advantageously ≥ 1.5% by weight and ≤ 4.0% by weight, in each case based on the total monomer amount 1.

[0053] The monomers A3 that can be used include all ethylenically unsaturated compounds different from monomers A1 and A2, such as (meth)acrylic acid alkyl esters, where these monomers preferably include (meth)acrylic acid alkyl esters in which the linear or branched alkyl group has 1 to 20 carbon atoms, particularly preferably 1 to 10 carbon atoms and very particularly preferably 1 to 8 carbon atoms. In this context, it should be noted that "(meth)acrylic acid" compounds or "(meth)acrylate" compounds should generally be understood to include the relevant acrylic acid compounds and the relevant methacrylic acid compounds.

[0054] Examples of the (meth)acrylic acid alkyl esters include: methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, 2-methylbutyl (meth)acrylate, pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, pentyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-propylheptyl (meth)acrylate, n-decyl (meth)acrylate, undecyl (meth)acrylate and / or n-dodecyl (meth)acrylate.

[0055] 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.

[0056] Also advantageously considered as monomer A3 are vinyl aromatic compounds having up to 20 carbon atoms.

[0057] The vinyl aromatic compounds having up to 20 carbon atoms are optionally substituted aromatic systems having a vinyl group conjugated to the aromatic ring system.

[0058] Such substituted vinyl aromatic compounds usually have one or more, preferably one, straight-chain or branched alkyl group having 1 to 10 carbon atoms, usually 1 to 6 carbon atoms and preferably 1 to 4 carbon atoms, on the aryl or on the vinyl group. If the substituent is on the aryl, the substituent may preferably be in the ortho or para position to the vinyl group, particularly preferably in the para position to the vinyl group.

[0059] Suitable vinyl aromatic compounds particularly include vinylbenzene, vinylnaphthalene, α-methylstyrene and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and / or styrene, however, styrene and / or α-methylstyrene are particularly preferred among them.

[0060] Moreover, monomer A3 further comprises: ethylenically unsaturated nitriles having up to 20 carbon atoms, such as in particular dinitrile fumarate, acrylonitrile and methacrylonitrile, preferably acrylonitrile and methacrylonitrile, and particularly preferably acrylonitrile; vinyl esters of carboxylic acids having up to 20 carbon atoms, especially vinyl laurate, vinyl stearate, vinyl propionate, vinyl versatate, vinyl butyrate and vinyl acetate, but preferably vinyl acetate; vinyl halides and vinylidene halides having up to 10 carbon atoms, such as in particular chlorine, fluorine or bromine-substituted ethylenically unsaturated compounds, preferably vinyl chloride and vinylidene chloride; and vinyl ethers of alcohols having 1 to 10 carbon atoms, advantageously for example methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, tert-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether and n-octyl vinyl ether, where vinyl ethers of alcohols having 1 to 4 carbon atoms are preferred.

[0061] It is particularly advantageous when the at least one monomer A3 is present to an extent of ≥80% by weight selected from n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, styrene and methyl methacrylate.

[0062] Monomer A3 may also comprise a minor content, i.e. >0% by weight and ≤20% by weight, advantageously ≥1% by weight and ≤10% by weight and particularly advantageously ≥1% by weight and ≤6% by weight, of the following functionalized ethylenically unsaturated monomers, in each case based on the total amount of monomer A3.

[0063] The functionalized ethylenically unsaturated monomers considered include all monoethylenically unsaturated compounds having at least one hydroxyl group, such as acrylates and / or methacrylates of the following groups: in particular all hydroxyalkyls, advantageously hydroxy-C2-C 10 -alkyls, preferably hydroxy-C2-C4-alkyls and particularly advantageously hydroxy-C2-C3-alkyls, where in the context of this document, alkoxylated hydroxyalkyl acrylates and / or methacrylates - i.e. those reacted with alkylene oxides (essentially ethylene oxide and propylene oxide) - are also considered as monomer A3. Monomer A3 containing hydroxyalkyl is advantageously selected from: 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. It is particularly advantageous to use 2-hydroxyethyl acrylate and / or 2-hydroxyethyl methacrylate, with 2-hydroxyethyl methacrylate being particularly preferred.

[0064] Functionalized ethylenically unsaturated monomers should also be understood to include hydroxyalkyl acrylates and hydroxyalkyl methacrylates having more than one hydroxyl group, for example two to five, preferably two to four, particularly preferably two to three hydroxyl groups. Examples thereof are glycerol monoacrylate and glycerol methacrylate, trimethylolpropane monoacrylate and trimethylolpropane methacrylate, pentaerythritol monoacrylate and pentaerythritol methacrylate, and monoacrylates and methacrylates of the following sugar alcohols: for example sorbitol, mannitol, diglycerol, threitol, erythritol, adonitol (ribitol), arabinitol (lyxitol), xylitol, dulcitol (galactitol), maltitol and isomaltitol.

[0065] Functionalized ethylenically unsaturated compounds A3 which can be used according to the invention also include organic compounds having at least two non-conjugated ethylenically unsaturated groups, for example 1,2-, 1,3- and 1,4-butanediol diacrylate, 1,2- and 1,3-propanediol (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(meth)acrylate and pentaerythritol tetra(meth)acrylate, allyl methacrylate, 1,2-, 1,3- and 1,4-divinylbenzene and mixtures thereof. These compounds are particularly preferably selected from divinylbenzene, 1,4-butanediol diacrylate and allyl methacrylate.

[0066] Other functionalized ethylenically unsaturated compounds A3 which can be used according to the invention are selected from: 2-(2-oxoimidazolidin-1-yl)ethyl (meth)acrylate (2-ureidoethyl acrylate and 2-ureidoethyl (meth)acrylate), N-[2-(2-oxooxazolidin-3-yl)ethyl] methacrylate, 2-(acetoacetoxy)ethyl acrylate, acetoacetoxypropyl methacrylate, acetoacetoxybutyl methacrylate, 2-(acetoacetoxy)ethyl methacrylate, diacetoneacrylamide (DAAM) and diacetonemethacrylamide. Preferred among the abovementioned compounds are 2-(2-oxoimidazolidin-1-yl)ethyl (meth)acrylate, (acetoacetoxy)ethyl methacrylate, diacetoneacrylamide and / or diacetonemethacrylamide, and particularly preferred are 2-(2-oxoimidazolidin-1-yl)ethyl (meth)acrylate and (acetoacetoxy)ethyl methacrylate.

[0067] However, the functionalized ethylenically unsaturated compound A3 that can be used according to the present invention also includes compounds having (meth)acryloyl groups and epoxy groups. Examples particularly include glycidyl acrylate and glycidyl methacrylate, preferably glycidyl methacrylate.

[0068] Among the functionalized ethylenically unsaturated compounds A3 that can be used according to the present invention, there are also included ethylenically unsaturated compounds having at least one silicon-containing group, such as vinyltriacetoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, or vinyltriethoxysilane.

[0069] It is particularly advantageous when the at least one monomer A3 is present in an amount of >0 wt% and ≤20 wt% selected from 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.

[0070] The total amount of monomer A3 is ≥91.0 wt% and ≤97.5 wt%, advantageously ≥93.0 wt% and ≤97.5 wt%, and particularly advantageously ≥95.2 wt% and ≤97.4 wt%, in each case based on the total monomer amount 1.

[0071] According to the present invention, the types and amounts of monomers A1 to A3 are selected such that the glass transition temperature Tg of the polymer 1 obtained therefrom after the polymerization reaction, measured according to DIN EN ISO 11357-2 (2013-09) [differential scanning calorimetry, midpoint temperature, heating rate 20 K / minute] 1 is in the range of ≥-10 °C and ≤15 °C, advantageously ≥-5 °C and ≤10 °C, and particularly advantageously ≥-5 °C and ≤5 °C. It should be noted that all the glass transition temperatures recorded herein are determined by the above method.

[0072] It is known to those skilled in the art that according to Fox (T.G. Fox, Bull. Am. Phys. Soc. 1956 [Ser. II] 1, page 123 and Ullmann's Encyclopedia of Industrial Chemistry, Volume 19, page 18, 4th edition, Verlag Chemie, Weinheim, 1980), the following formula can be used to well approximate and estimate the glass transition temperature of at most weakly crosslinked copolymers:

[0073] 1 / Tg = x1 / Tg 1 +x2 / Tg2 +....x n / Tg n ,

[0074] where x1, x2... x n are the mass fractions of monomers 1, 2... n, and Tg 1 , Tg 2 ... Tg n are the glass transition temperatures in Kelvin of the respective polymers consisting of only one of monomers 1, 2... n. The glass transition temperatures of these homopolymers of most ethylenically unsaturated monomers are known (or can be experimentally determined in a simple manner known per se) and are listed, for example, in the following documents: J. Brandrup, E. H. Immergut, Polymer Handbook, 1st Edition, J. Wiley, New York, 1966; 2nd Edition, J. Wiley, New York, 1975; and 3rd Edition, J. Wiley, New York, 1989, as well as Ullmann's Encyclopedia of Industrial Chemistry, page 169, Verlag Chemie, Weinheim, 1992.

[0075] Advantageously used in the first polymerization stage are:

[0076] acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid and / or crotonic acid in an amount of ≥ 1.0% by weight and ≤ 3.0% by weight,

[0077] ≥ 1.5% by weight and ≤ 6.0% by weight of

[0078] H2C=C(CH3)-C(=O)-[OCH(CH3)CH2] 4-7 -O-P(=O)(-OH)2,

[0079] H2C=C(CH3)-C(=O)-[OCH2CH2] 4-7 -O-P(=O)(-OH)2 and / or

[0080] H2C=C(CH3)-C(=O)-OCH2CH2-O-P(=O)(-OH)2,

[0081] n-butyl acrylate, n-butyl methacrylate,

[0082] 2-ethylhexyl acrylate, styrene and / or methyl methacrylate in an amount of ≥ 81% by weight and ≤ 97.5% by weight, and

[0083] 2-Hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,

[0084] 2-(Acetoacetoxy)ethyl methacrylate, 2-ureidoethyl methacrylate, diacetone acrylamide, glycidyl methacrylate, 3-(methacryloyloxy)propyltrimethoxysilane, vinyltriethoxysilane, allyl methacrylate and / or 1,4-butanediol diacrylate, and particularly preferably

[0085] ≥1.0 wt% and ≤2.0 wt% of acrylic acid and / or methacrylic acid,

[0086] ≥1.5 wt% and ≤5.0 wt% of

[0087] H2C=C(CH3)-C(=O)-[OCH(CH3CH2)] 4-7 -O-P(=O)(-OH)2,

[0088] ≥85 wt% and ≤97.5 wt% of methyl methacrylate, styrene and / or 2-ethylhexyl acrylate, and

[0089] ≥0 wt% and ≤8.0 wt% of (acetoacetoxy)ethyl methacrylate and / or vinyltriethoxysilane.

[0090] The monomers B1 considered include all of the above monomers A1. The amount of monomer B1 is ≤0.1 wt%, advantageously ≤0.05 wt% and particularly advantageously ≤0.01 wt%, in each case based on the total monomer amount 2.

[0091] Similarly, the B2 considered include all of the above monomers A2. The amount of monomer B2 is ≤0.1 wt%, advantageously ≤0.05 wt% and particularly advantageously ≤0.01 wt%, in each case based on the total monomer amount 2.

[0092] However, it is advantageous not to use any monomers B1 and B2.

[0093] The monomers B3 considered in principle include all of the above monomers A3, however, the proportion of functionalized ethylenically unsaturated monomers therein is ≤1.0% by weight, advantageously ≤0.5% by weight and particularly advantageously ≤0.1% by weight, in each case based on the total amount of monomers B3. Particularly advantageously used as monomers B3 are n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, styrene and methyl methacrylate, wherein their proportion is ≥99.0% by weight, preferably ≥99.5% by weight and particularly preferably ≥99.9% by weight, in each case based on the total amount of monomers B3. Monomers B3 are particularly advantageously selected to the extent of 100% by weight from n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, styrene and methyl methacrylate.

[0094] According to the invention, the types and amounts of monomers B1 to B3 are selected such that the glass transition temperature Tg of the polymer 2 obtained therefrom after the polymerization reaction 2 is higher than the glass transition temperature Tg 1 by at least 10 °C [Tg 2 = Tg 1 + ≥10 °C]. The glass transition temperature Tg 2 is advantageously higher than the glass transition temperature Tg 1 by at least 15 °C. Thus, the glass transition temperature Tg 2 is in the range of ≥0 °C and ≤80 °C, advantageously ≥10 °C and ≤60 °C and particularly advantageously ≥10 °C and ≤40 °C.

[0095] Advantageously used in the second polymerization stage are:

[0096] ≥0% by weight and ≤95% by weight of n-butyl methacrylate,

[0097] ≥2% by weight and ≤90% by weight of styrene, and

[0098] ≥0% by weight and ≤40% by weight of methyl methacrylate and / or 2-ethylhexyl acrylate,

[0099] and particularly preferably

[0100] ≥5% by weight and ≤95% by weight of n-butyl methacrylate,

[0101] ≥2% by weight and ≤70% by weight of styrene, and

[0102] ≥0% by weight and ≤25% by weight of methyl methacrylate and / or 2-ethylhexyl acrylate.

[0103] Advantageously, the types and amounts of monomers A1 to A3 and B1 to B3 are selected such that the glass transition temperature Tg of the resulting polymer 1 1ranges from ≥ -5 °C and ≤ 10 °C, and the glass transition temperature Tg of the resulting polymer 2 2 ranges from ≥ 10 °C and ≤ 40 °C.

[0104] It should be noted that the quantitative ratio of total monomer amount 1 to total monomer amount 2 is from 70 wt% to 85 wt% to 15 wt% to 30 wt%, and advantageously from 70 wt% to 80 wt% to 20 wt% to 30 wt%.

[0105] According to the present invention, it should be noted that the above monomers A1 to A3 and B1 to B3 can be used individually or in the form of a mixture. In each case, all or part of the monomers A1 to A3 can be first added to the aqueous polymerization medium before initiating the polymerization reaction, and any remaining portion can be added under polymerization conditions. However, all of the monomers A1 to A3 (total monomer amount 1) can also be added to the aqueous polymerization medium under polymerization conditions.

[0106] In a preferred embodiment, in the first polymerization stage, before initiating the polymerization reaction, at least ≤ 10 wt% of the total monomer amount 1 is first added to the aqueous polymerization medium, and the remaining balance is added to the aqueous polymerization medium under polymerization conditions, while in the second polymerization stage, all of the monomers B1 to B3 (total monomer amount 2) are added to the aqueous polymerization medium under polymerization conditions. The monomers A1 to A3 and B1 to B3 can be added to the aqueous polymerization medium discontinuously or continuously in the form of separate streams, in the form of a monomer mixture, or in the form of an aqueous monomer emulsion at a constant or variable flow rate.

[0107] However, it is particularly advantageous when the monomers of the first and second polymerization stages are used in the form of a monomer mixture, particularly advantageously in the form of an aqueous monomer emulsion. Advantageously, at least ≥ 90 wt% and particularly advantageously ≥ 95 wt% or all of the monomer mixture of the first and second polymerization stages are added to the aqueous polymerization medium in the form of an aqueous monomer emulsion under polymerization conditions.

[0108] According to the present invention, free-radical-initiated aqueous emulsion polymerization is generally carried out in the presence of a free-radical polymerization initiator (free-radical initiator). The free-radical initiators considered include all those initiators capable of initiating free-radical aqueous emulsion polymerization. These initiators can in principle be peroxides or azo compounds. Of course, redox initiator systems are also considered. The peroxides that can be used include in principle inorganic peroxides such as hydrogen peroxide or persulfates such as the mono-alkali metal salts or di-alkali metal salts or ammonium salts of persulfuric acid, such as the monosodium salt and disodium salt, monopotassium salt and dipotassium salt or ammonium salt; or organic peroxides such as alkyl hydroperoxides, such as tert-butyl hydroperoxide, p-menthyl hydroperoxide or cumyl hydroperoxide, and dialkyl peroxides or diaryl peroxides, such as di-tert-butyl peroxide or dicumyl peroxide. The azo compounds used are essentially 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile) and 2,2'-azobis(amidinopropyl) dihydrochloride (AIBA, corresponding to V-50 from Wako Chemicals). Of course, so-called redox initiator systems can also be used as free-radical initiators. For redox initiator systems, the suitable oxidants are essentially the peroxides specified above. The corresponding reducing agents that can be used are sulfur compounds in a low oxidation state, such as alkali metal sulfites, such as potassium sulfite and / or sodium sulfite; alkali metal bisulfites, such as potassium bisulfite and / or sodium bisulfite; alkali metal metabisulfites, such as potassium metabisulfite and / or sodium metabisulfite; formaldehyde sulfoxylates, such as potassium formaldehyde sulfoxylate and / or sodium formaldehyde sulfoxylate; alkali metal salts, especially the potassium salts and / or sodium salts of aliphatic sulfonic acids; and alkali metal hydrosulfides, such as potassium hydrosulfide and / or sodium hydrosulfide; salts of polyvalent metals, such as iron(II) sulfate, ammonium iron(II) sulfate, iron(II) phosphate; enediols, such as dihydroxymaleic acid, benzoic acid and / or ascorbic acid; and reducing sugars, such as sorbose, glucose, fructose and / or dihydroxyacetone.

[0109] The initiation of the polymerization reaction should be understood to mean the start of the polymerization reaction of the monomers present in the polymerization reaction vessel after the formation of free radicals by a free radical initiator. The polymerization reaction can be initiated by adding a free radical initiator to the aqueous polymerization mixture in the polymerization reaction vessel under polymerization conditions. However, it is also possible to add a part or the total amount of the free radical initiator to the aqueous polymerization mixture containing the initially added monomers in the polymerization reaction vessel under conditions that are not suitable for initiating the polymerization reaction (for example, at low temperature), and then establish polymerization conditions in the aqueous polymerization mixture. Polymerization conditions should generally be understood to mean such temperature and pressure at which the free radical-initiated aqueous emulsion polymerization reaction proceeds at a sufficient polymerization rate. They depend in particular on the free radical initiator used. Advantageously, the type and amount of the free radical initiator, the polymerization temperature and the polymerization pressure are selected such that the half-life of the free radical initiator < 3 h and particularly advantageously < 1 h, and there is always sufficient initiator radical available for initiating and maintaining the polymerization reaction.

[0110] For free radical-initiated aqueous emulsion polymerization, the reaction temperatures considered are in the entire range from 0 °C to 170 °C. The temperatures used are generally from 50 °C to 120 °C, preferably from 60 °C to 110 °C and particularly preferably from 60 °C to 100 °C. The free radical-initiated aqueous emulsion polymerization can be carried out at a pressure 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 can be up to 170 °C. In the presence of low-boiling monomers A1 to B3, the emulsion polymerization is preferably carried out under high pressure. In this case, the pressure can assume values of 1.2 bar, 1.5 bar, 2 bar, 5 bar, 10 bar, 15 bar (absolute) or even higher values. If the emulsion polymerization is carried out under reduced pressure, a pressure of 950 mbar, usually 900 mbar and often 850 mbar (absolute) is established. Advantageously, the free radical aqueous emulsion polymerization is carried out at 1 atm, in particular under an inert gas atmosphere, for example under nitrogen or argon, excluding oxygen.

[0111] According to the invention, the total amount of the free radical initiator can first be added to the aqueous reaction medium before initiating the polymerization reaction. However, it is also possible to first add only a part of the free radical initiator to the aqueous reaction medium before initiating the polymerization reaction, and then, during the free radical-initiated emulsion polymerization, continuously or discontinuously add the total amount / any remaining residue according to consumption in the first and / or second polymerization stage under polymerization conditions. Of course, different amounts of different free radical initiators can also be used in the first and second polymerization stages. In a preferred embodiment, a part of the free radical initiator is first added to the aqueous reaction medium before initiating the polymerization reaction, and then the remaining residue is added during the addition of the monomers in the first and second polymerization stages.

[0112] The total amount of the free-radical initiator is generally ≥ 0.05% by weight and ≤ 5% by weight, preferably ≥ 0.1% by weight and ≤ 3% by weight, and particularly preferably ≥ 0.1% by weight and ≤ 1.5% by weight, in each case based on the total monomer amount.

[0113] To adjust the weight-average molecular weight of the polymers formed in the first and second polymerization stages, free-radical chain transfer compounds (chain transfer agents) can be used. The compounds used are essentially aliphatic and / or araliphatic halogen compounds such as, for example, n-butyl chloride, n-butyl bromide, n-butyl iodide, dichloromethane, dichloroethane, chloroform, bromoform, bromotrichloromethane, dibromodichloromethane, carbon tetrachloride, carbon tetrabromide, benzyl chloride, benzyl bromide; organic sulfur-containing compounds such as primary, secondary or tertiary aliphatic mercaptans 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 mercaptans such as 2-hydroxyethanethiol; aromatic mercaptans such as benzenethiol, o-methylbenzenethiol, m-methylbenzenethiol or p-methylbenzenethiol; mercaptoalkanoic acids and their derivatives such as 6-methylheptyl 3-mercaptopropionate or 2-ethylhexyl 2-mercaptoacetate; and all other sulfur compounds described in Polymer handbook, 3rd edition, 1989, J. Brandrup and E. H. Immergut, John Wiley & Sons, Section II, pages 133 to 141; and aliphatic aldehydes and / or aromatic aldehydes such as acetaldehyde, propionaldehyde and / or benzaldehyde; unsaturated fatty acids such as oleic acid; dienes having non-conjugated double bonds such as divinylmethane or vinylcyclohexane; or hydrocarbons having easily abstractable hydrogen atoms such as toluene. However, mixtures of non-interfering representatives of the above chain transfer agents can also be used.

[0114] According to the present invention, before initiating the polymerization reaction, the total amount of the chain transfer agent can first be added to the aqueous reaction medium. However, it is also possible to optionally first add only a part of the chain transfer agent to the aqueous reaction medium before initiating the polymerization reaction, and then, during the free-radical-initiated emulsion polymerization, under polymerization conditions, continuously or discontinuously add the total amount / any remaining residue as needed in the first and / or second polymerization stage. Of course, different amounts of different chain transfer agents can also be used in the first and second polymerization stages.

[0115] The total amount of the chain transfer agent is generally ≥ 0% by weight and ≤ 5% by weight, preferably ≥ 0% by weight and ≤ 2% by weight, and particularly preferably ≥ 0% by weight and ≤ 1% by weight, in each case based on the total monomer amount.

[0116] For the present invention, it is necessary that the aqueous emulsion polymerization is carried out in the presence of at least one phosphorus-containing dispersing aid, which keeps both the monomer droplets and the formed polymer particles dispersed in the aqueous phase, thereby ensuring the stability of the prepared aqueous polymer dispersion. Suitable phosphorus-containing dispersing aids in principle include all dispersing aids containing at least one phosphorus-containing group.

[0117] Suitable phosphorus-containing dispersing aids include, for example, monoesters and / or diesters of phosphoric acid with alkoxylated and / or non-alkoxylated C6- 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 should be noted that in the context of this text, these literature citations will be explicitly referred to, and the phosphorus-containing dispersing aids disclosed therein should be regarded as components of this text accordingly.

[0118] However, in the context of this text, it is particularly advantageous to use a phosphorus-containing dispersing aid selected from the compounds of formula II and the alkali metal salts or ammonium salts of the compounds of formula II

[0119] R 1 -O-(AO) m -P(=O)(OR 2 )(OH) Formula (II)

[0120] wherein

[0121] m represents an integer from 0 to 30, preferably from 5 to 25, and particularly preferably from 5 to 20,

[0122] AO represents an alkyleneoxy as defined for the compounds of general formula I

[0123] (alkyleneoxy),

[0124] R 1 represents a C6-C 30 -alkyl group, preferably a C8-C 22 -alkyl group and particularly preferably a C 11 -C 14 -alkyl group, and

[0125] R 2 represents H or the group -(AO) m -R 2a wherein R 2a is as defined for R 1 above, and AO and m have one of the definitions specified above, provided that, however, R 2 advantageously represents H,

[0126] The above-mentioned phosphorus-containing dispersing aids are familiar to those skilled in the art and are commercially available, for example, as

[0127] 24T (BASF BTC),

[0128] 10T (BASF BTC),

[0129] A (DSM Nutritional Products Europe Ltd.),

[0130] CPE (Colonial Chemical, Inc.),

[0131] MCA (Croda Inc.),

[0132] CES (Croda Inc.),

[0133] HCE (Croda Inc.),

[0134] 1435 (Croda Inc.),

[0135] CS20Acid (Croda Inc.),

[0136] CP (Croda Inc.),

[0137] CC100 (Clariant International Ltd.),

[0138] RS-410 (Solvay S.A.),

[0139] RS-610 (Solvay S.A.),

[0140] RS-610 / A25 (Solvay S.A.),

[0141] RS-610E (Solvay S.A.),

[0142] RS-710 (Solvay S.A.),

[0143] RS-710E (Solvay S.A.), or

[0144] A-EP (BASF SE).

[0145] The amount of the at least one phosphorus-containing dispersing aid used according to the invention is ≥ 0.5% by weight, advantageously ≥ 0.5% by weight and ≤ 4.0% by weight, preferably ≥ 0.5% by weight and ≤ 2.0% by weight and particularly preferably ≥ 0.7% by weight and ≤ 1.5% by weight, in each case based on the total monomer amount.

[0146] According to the invention, before initiating the polymerization reaction, the total amount of the phosphorus-containing dispersing aid can first be added to the aqueous reaction medium. However, before initiating the polymerization reaction, optionally only a part of the phosphorus-containing dispersing aid can first be added to the aqueous reaction medium, and then during the free-radical-initiated emulsion polymerization, under polymerization conditions, in the first polymerization stage or in the first and second polymerization stages as required continuously or discontinuously, the total amount / any remaining residual amount can be added. Of course, in the first and second polymerization stages, different amounts of different phosphorus-containing dispersing aids can also be used. Advantageously, during the polymerization reaction, ≥ 50% by weight of the at least one phosphorus-containing dispersing aid is added to the aqueous reaction medium as a component of the aqueous monomer emulsion. However, it should be noted that at least a part of the at least one phosphorus-containing dispersing aid is already present during the first polymerization stage. Advantageously, the amount of the at least one phosphorus-containing dispersing aid during the aqueous emulsion polymerization is always ≥ 0.5% by weight and advantageously ≥ 0.8% by weight, in each case based on the total amount of monomers A1 to B3 added to the aqueous polymerization mixture at that time.

[0147] In addition to the at least one phosphorus-containing dispersing aid, other protective colloids and / or emulsifiers which are customarily used for free-radical aqueous emulsion polymerization may optionally also be used.

[0148] Suitable protective colloids are, for example, polyvinyl alcohol, cellulose derivatives or copolymers containing vinylpyrrolidone. A detailed description of other suitable protective colloids can be found in Houben-Weyl, Methoden der organischen Chemie, Volume XIV / 1, Makromolekulare Stoffe, pages 411 to 420, Georg-Thieme-Verlag, Stuttgart, 1961. Of course, mixtures of emulsifiers and / or protective colloids may also be used. The additional dispersing aids used are preferably only emulsifiers, which differ from protective colloids and generally have a relative molecular weight below 1000. They can be anionic, cationic or nonionic. When using mixtures of surface-active substances, the individual components must of course be compatible with one another, and if there are any doubts, some preliminary experiments can be carried out to check. Anionic emulsifiers are generally compatible with one another and with nonionic emulsifiers. This also applies to cationic emulsifiers, although anionic emulsifiers and cationic emulsifiers are mostly incompatible with one another. Emulsifiers which are customarily used are, for example, ethoxylated monoalkylphenols, dialkylphenols and trialkylphenols (degree of ethoxylation: 3 to 50, alkyl group: C4 to C12), ethoxylated fatty alcohols (degree of ethoxylation: 3 to 50, alkyl group: C8 to C36); and the alkali metal salts and ammonium salts of the following substances: alkyl sulfates (alkyl group: C8 to C12), sulfuric acid monoesters of ethoxylated alkanols (degree of ethoxylation: 4 to 30, alkyl group: C12 to C18) and ethoxylated alkylphenols (degree of ethoxylation: 3 to 50, alkyl group: C4 to C12), alkyl sulfonic acids (alkyl group: C12 to C18) and alkylarylsulfonic acids (alkyl group: C9 to C18). Other suitable emulsifiers can be found in Houben-Weyl, Methoden der organischen Chemie, Volume XIV / 1, Makromolekulare Stoffe, pages 192 to 208, Georg-Thieme-Verlag, Stuttgart, 1961.

[0149] Other surface-active substances which have proven suitable include compounds of the general formula III

[0150]

[0151] wherein R 3 and R 4 represent a hydrogen atom or C4- to C 24-alkyl and not both being hydrogen atoms, M 1 and M 2 may be an alkali metal ion and / or an ammonium ion. In general formula III, R 3 and R 4 preferably represent a straight-chain or branched alkyl group having 6 to 18 carbon atoms, particularly having 6, 12 or 16 carbon atoms, or represent hydrogen, where R 3 and R 4 are not both hydrogen atoms. M 1 and M 2 are preferably sodium, potassium or ammonium, particularly preferably sodium. Particularly advantageous compounds of general formula III are those in which M 1 and M 2 are sodium, R 3 is a branched alkyl group having 12 carbon atoms, and R 4 is a hydrogen atom or R 3 . Industrially available mixtures containing 50% to 90% by weight of the monoalkylated product are usually used, such as 2A1 (a brand of Dow Chemical Company). Compounds of general formula III are common general knowledge, for example from US-A4269749, and are commercially available.

[0152] In addition to the at least one phosphorus-containing dispersing aid, if additional dispersing aids are also used, it is advantageous to use an anionic surfactant and / or a non-ionic surfactant, and particularly advantageously an anionic surfactant.

[0153] The total amount of optional dispersing aids is usually ≥ 0% by weight and ≤ 3.0% by weight, preferably ≥ 0% by weight and ≤ 2.0% by weight, and particularly preferably ≥ 0.1% by weight and ≤ 0.5% by weight, in each case based on the total monomer amount.

[0154] According to the present invention, during the free-radical initiated emulsion polymerization, under the polymerization conditions, the total amount of optional dispersing aids is added continuously or discontinuously as required in the first and / or second polymerization stage. However, before initiating the polymerization reaction, it is also possible to optionally first add the total amount or a part of the optionally used dispersing aids to the aqueous reaction medium, and during the first and / or second polymerization stage, any remaining residue is added continuously or discontinuously.

[0155] It should also be noted that the free-radical initiated aqueous emulsion polymerization in the first polymerization stage can also be optionally carried out in the presence of polymer seeds, for example in the presence of 0.01% to 10% by weight, usually 0.05% to 7.0% by weight, and usually 0.1% to 4.0% by weight of polymer seeds, in each case based on the total amount of monomers.

[0156] According to the invention, especially when it is desired to control the particle size of polymer particles prepared by free-radical-initiated aqueous emulsion polymerization, polymer seeds are used (in this regard, see for example US-A 2520959 and US-A 3397165).

[0157] If polymer seeds are used in the process according to the invention, the weight-average particle size Dw of the polymer seed particles is advantageously ≤100 nm, usually ≥5 nm to ≤50 nm and often ≥15 nm to ≤35 nm.

[0158] Polymer seeds are generally used in the form of an aqueous polymer dispersion.

[0159] If polymer seeds are used, it is advantageous to use exogenous polymer seeds. Different from the so-called in-situ polymer seeds which are prepared in the reaction vessel before the actual emulsion polymerization starts and usually have the same monomer composition as the polymer 1 prepared by subsequent free-radical-initiated aqueous emulsion polymerization, exogenous polymer seeds should be understood to mean polymer seeds that have been prepared in a separate reaction step and have a different monomer composition from the polymer 1 prepared by free-radical-initiated aqueous emulsion polymerization. However, this only means that different monomers or monomer mixtures with different compositions are used for the preparation of exogenous polymer seeds and the preparation of the aqueous polymer dispersion. The preparation of exogenous polymer seeds is familiar to those skilled in the art and is generally carried out by adding a sufficient amount of polymerization initiator to an initial charge of a relatively small amount of monomer and a relatively large amount of emulsifier in the reaction vessel at the reaction temperature.

[0160] According to the invention, it is preferred to use exogenous polymer seeds with a glass transition temperature ≥50 °C, usually ≥60 °C or ≥70 °C and often ≥80 °C or ≥90 °C. Particularly preferred are polystyrene polymer seeds or polymethyl methacrylate polymer seeds.

[0161] The total amount of exogenous polymer seeds can be added to the polymerization vessel first. However, it is also possible to add only a part of the exogenous polymer seeds to the polymerization vessel first and add the remaining residue together with monomers A1 to A3 / B1 to B3 during the polymerization. However, if necessary, the total amount of polymer seeds can also be added during the polymerization process. It is preferred to add the total amount of exogenous polymer seeds to the polymerization vessel first before initiating the polymerization reaction.

[0162] The process of the present invention is advantageously carried out such that the second polymerization stage is only started when the total monomer amount 1 has been converted to ≥98% by weight, advantageously ≥99% by weight and particularly advantageously ≥99.5% by weight, as can be easily determined using calorimetric measurements familiar to those skilled in the art. Correspondingly, the polymerization stage 2 is also carried out to a monomer conversion of up to ≥98% by weight, advantageously ≥99% by weight and particularly advantageously up to 99.5% by weight of the total monomer amount 2.

[0163] According to the present invention, it is advantageous if the aqueous polymerization mixture has a pH range of ≥3 and ≤8, particularly advantageously ≥4.0 and ≤6.5, measured at room temperature during the first and second polymerization stages. According to the present invention, the pH measurement or pH test is carried out in such a way that a small amount of the aqueous polymerization mixture is continuously discharged from the polymerization vessel through a small bypass line and cooled to 20 °C to 25 °C (room temperature), and its pH is determined by means of a calibrated pH electrode, and then the aqueous polymerization mixture is returned to the polymerization vessel. Of course, it is also possible to take a sample of a small amount of the aqueous polymerization mixture, cool it to room temperature, measure the pH, and then return the sample to the aqueous polymerization mixture.

[0164] According to the present invention, any conventional base can be used for pH adjustment, such as hydroxides or carbonates or bicarbonates of alkali metals, alkaline earth metals or ammonium, such as NaOH, KOH, NH4OH, Ca(OH)2, Na2CO3, K2CO3, (NH4)CO3, NaHCO3, KHCO3 or NH4HCO3. Also suitable as bases are ammonia and primary, secondary or tertiary organic amines, such as methylamine, ethylamine, 1-propylamine, 2-propylamine, 1-n-butylamine, 2-n-butylamine, 2-methyl-1-propylamine, 2-methyl-2-propylamine, etc.; dimethylamine, diethylamine, di-n-propylamine, diisopropylamine, di-n-butylamine, di-2-methylpropylamine, etc.; trimethylamine, triethylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, tri-2-methylpropylamine, etc.; and mixed amines, such as N-methyl-N-ethylamine, N,N-dimethyl-N-ethylamine, etc. However, it is advantageous to use a base having a boiling point of ≤20 °C, advantageously ≤10 °C and particularly advantageously ≤0 °C at a pressure of 1.013 bar (absolute) for pH adjustment, such as in particular trimethylamine and ammonia, especially in the form of their aqueous solutions or their basic salts (NH4)2CO3, NH4HCO3. However, ammonia is particularly preferred, especially in the form of its aqueous solution.

[0165] The aqueous polymer dispersion obtained after the second polymerization stage contains polymer particles having a weight-average particle size range of ≥50 and ≤500 nm, advantageously ≥50 and ≤200 nm and particularly ≥80 and ≤150 nm. According to the present invention, the determination of the weight-average particle size is generally carried out according to ISO 13321 using a high-performance particle size analyzer from Malvern at a wavelength of 633 nm and a temperature of 22 °C.

[0166] It should be understood that the preferred embodiments also provide aqueous polymer dispersions obtainable by the process of the invention and polymer powders obtainable by drying them. The preparation of polymer powders 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.

[0167] It should be noted that the aqueous polymer dispersions prepared by the process of the invention are characterized by high stability and low coagulum formation. In addition, the V2A steel reactor or V4A steel reactor used in the process of the invention shows significantly reduced signs of corrosion, if any, especially signs of corrosion due to pH testing.

[0168] It should also be noted that the aqueous polymer dispersions obtainable by the process of the invention and the polymer powders obtainable by drying them are advantageously useful as binders in the preparation of adhesives, sealants, plasters, paper coating slurries, fibrous non-wovens, flexible roof coatings and paints, and as binders in sand consolidation, as components in the preparation of textile or leather auxiliaries and impact modifiers, or can be used for the modification of mineral binders and plastics.

[0169] The aqueous polymer dispersions / their polymer powders of the invention are particularly advantageously suitable as binders in aqueous anti-corrosion preparations for metal surfaces, where metal surfaces should be understood to also include the surfaces of metal alloys. If a multi-layer system is used, the aqueous polymer dispersions / their polymer powders of the invention can be used as binders in one or more layers.

[0170] If the above aqueous preparations are used for the preparation of aqueous anti-corrosion preparations, these aqueous preparations can contain not only conventional components such as organic solvents, coalescing agents, other additives such as dispersion aids, neutralizing agents, defoamers, thickeners and flow additives, and bactericidal or fungicidal aids, but also pigments, fillers and / or preservatives.

[0171] The pigments that can be used in principle include all organic and / or inorganic white pigments or colored pigments familiar to those skilled in the art, the particle size of which, measured using a Hegmann fineness gauge according to ISO 1524, is ≤ 15 μm.

[0172] Due to its high refractive index (rutile: 2.70, anatase: 2.55) and its good covering power, various modified forms of titanium dioxide can be mentioned as the most important white pigments. However, zinc oxide and zinc sulfide are also used as white pigments. These white pigments can be used in coated or uncoated form. However, organic white pigments can also be used, such as non-film-forming styrene- and carboxyl-rich hollow polymer particles (so-called opaque particles) with a particle size of about 300 to 400 nm.

[0173] In addition to white pigments, various different colored pigments familiar to those skilled in the art can also be used to complete coloring, such as inorganic iron oxides or sulfides, cadmium oxides or sulfides, chromium oxides or sulfides, and lead oxides or sulfides, lead molybdate, cobalt blue or carbon black, which are slightly lower in cost, as well as organic pigments, such as phthalocyanine, azo pigments, quinacridone, perylene or carbazole, which are slightly higher in cost.

[0174] Of course, in addition to pigments, the aqueous preparation may also include so-called fillers known to those skilled in the art. Fillers should be understood to mean substantially powdery inorganic materials having a relatively low refractive index compared to pigments (refractive index value of white fillers < 1.7 according to DIN 55943 and DIN 55945) and a particle size ≤ 20 μm (according to Hegmann). Powdery fillers are usually naturally occurring minerals, such as calcite, chalk, dolomite, kaolin, talc, mica, diatomaceous earth, barite, quartz or talc / chlorite assemblage, as well as synthetically prepared inorganic compounds, such as precipitated calcium carbonate, calcined kaolin or barium sulfate and pyrogenic silica. The filler used is preferably calcium carbonate in the form of crystalline calcite or amorphous chalk.

[0175] According to the present invention, the anticorrosive reagents considered particularly include corrosion inhibitors or anticorrosive pigments.

[0176] Examples of corrosion inhibitors are cited in "Corrosion Inhibitors, 2nd Edition, An industrial Guide", Ernest W. Flick, Editor: 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.

[0177] Examples of anticorrosive pigments are modified zinc orthophosphate (such as ZPA, ZPO and ZMP), zinc polyphosphate (such as ZAPP, SAPP, SRPP and CAPP), WSA - broad-spectrum preservatives (such as ZAMPLUS and ZCPPLUS) and modified silicate pigments (such as CTF, 750), for example from Heubach GmbH; and barium borophosphate (such as from 400), barium phosphosilicate (such as BW-111, BW-191), calcium borosilicate (e.g., CW-291, CW-22 / 221, CW-2230), calcium phosphosilicate (e.g., CW-491), strontium phosphosilicate (e.g., SW-111) or strontium zinc phosphosilicate (e.g., SZP-391).

[0178] Accordingly, one embodiment also provides an aqueous anti-corrosion preparation comprising at least one aqueous polymer dispersion of the present invention or at least one polymer powder of the present invention.

[0179] The present invention also provides a method for coating a metal surface, wherein an aqueous anti-corrosion preparation comprising an aqueous polymer dispersion of the present invention or a polymer powder of the present invention is applied to the metal surface and then dried.

[0180] The aqueous anti-corrosion preparation can be applied to the metal surface in a known manner, for example, by spraying, spreading, scraping, brushing, rolling, roller coating or curtain coating. Subsequently, the volatile components of the aqueous preparation are removed by drying. If necessary, this process can be repeated one or more times. Generally, the application amount is selected such that the dry film thickness (after removing the volatile components) is 15 to 150 μm and preferably 30 to 100 μm.

[0181] The substrates treated with the aqueous preparation for anti-corrosion purposes are the surfaces of iron, steel, Zn, Zn alloys, Al or Al alloys. The metal surface, preferably a degreased surface, can be uncoated, coated with zinc, aluminum or their alloys, hot-dip galvanized, electro-galvanized, sherardized or pre-coated with a primer.

[0182] Particular attention is paid herein to the surfaces of iron, steel, zinc, zinc alloys, aluminum or aluminum alloys. Steel may contain conventional alloy components known to those skilled in the art. Attention may be paid herein to the surfaces of articles composed entirely of the said metals or alloys. However, attention may also be paid to the surfaces of articles coated with Zn, Zn alloys, Al or Al alloys, wherein the articles may be made of other materials, such as other metals, alloys, polymers or composite materials. In a preferred embodiment of the present invention, attention is paid to steel surfaces or galvanized and / or aluminized steel surfaces.

[0183] Zinc alloys or aluminum alloys are known to those skilled in the art. The typical composition of zinc alloys particularly includes Al, Pb, Si, Mg, Sn, Cu or Cd. The typical composition of aluminum alloys particularly includes Mg, Mn, Si, Zn, Cr, Zr, Cu or Ti. The term "zinc alloy" should be understood to also include Al / Zn alloys in which Al and Zn are present in approximately equal amounts. Those skilled in the art will select the type and amount of alloy composition according to the intended use. A Zn coating or an aluminum coating can be applied to steel, for example, by hot-dip coating (such as hot-dip galvanizing) or by sherardizing. If the part cannot be moved or the geometry of the part does not allow movement, a thermal spraying method (spray galvanizing, spray aluminizing) can also be used to apply the corresponding layer.

[0184] The aqueous polymer dispersions of the present invention, in particular the aqueous formulations of the present invention, can advantageously be used to protect metal surfaces that are in contact with the atmosphere during use and surfaces that are in contact with water, soil or other corrosive media during use from corrosion.

[0185] The metal surfaces to be protected from corrosion using the aqueous polymer dispersions of the present invention, in particular the aqueous formulations of the present invention, can in principle be any desired surface. However, they are preferably the surfaces of metal building structures or metal structures or the parts required therefor. Metal structures or building structures are generally constructed by riveting, welding or screwing together construction steel such as steel beams, steel pipes or steel plates to form the corresponding structures. In one embodiment of the present invention, the coated article can be a fixed metal structure, such as a building, a bridge, a transmission tower, a tank, a container, a building, a pipeline, a power plant, a chemical plant, a ship, a crane, a pole, a sheet pile, a valve, a pipe, a tank, a fitting, a flange, a coupling, an aircraft hangar, a roof and construction steel. In this embodiment, the anti-corrosion coating is usually applied by in-situ painting or in-situ spraying. This can be the first treatment or a repair. The drying and curing of such anti-corrosion coatings are carried out under atmospheric conditions - that is, at ambient temperature and in the presence of air and at normal atmospheric humidity. The relative atmospheric humidity can take any value, but is preferably between 10% and 80% and particularly preferably between 30% and 70%. Depending on the required protection level, the corrosion protection of the anti-corrosion coating for the surface can also be divided into low corrosion protection, medium corrosion protection and high corrosion protection.

[0186] The present invention will be illustrated with reference to the following non-limiting examples. Examples

[0187] Example 1 (Dispersion 1)

[0188] Under a nitrogen atmosphere, at 20 °C to 25 °C (room temperature), first add to a 2 l polymerization vessel equipped with a feeding device and a temperature control device

[0189] 260.0 g of deionized water, and

[0190] 12.0 g of an aqueous solution of a 25 wt% phosphorus-containing dispersing aid ( RS610 / A25)

[0191] and heated to 90 °C with stirring. Once this temperature is reached, 30.4 g of Feed 1 is added, then 33.8 g of an aqueous solution of 2.5 wt% ammonium persulfate is added over 2 minutes, and then the mixture is stirred for an additional 10 minutes at the above temperature. While adding the ammonium persulfate solution, 32.6 g of an aqueous solution of 5.3 wt% ammonia is continuously added at a constant flow rate over a period of 175 minutes.

[0192] After an additional 10 minutes of stirring time has elapsed and while maintaining the temperature at 90 °C, the remainder of Feed 1 is continuously added at a constant flow rate over 90 minutes. While adding the remainder of Feed 1, 48.4 g of an aqueous solution of 2.5 wt% ammonium persulfate is also continuously added over 90 minutes. The polymerization mixture is then reacted for an additional 15 minutes at 90 °C. Subsequently, and while maintaining the temperature at 90 °C, Feed 2 is continuously added at a constant flow rate over 65 minutes. 15.2 g of an aqueous solution of 2.0 wt% ammonium persulfate is continuously added simultaneously with Feed 2. After Feed 2 is completed, the polymerization mixture is reacted for an additional 20 minutes at 90 °C. The resulting aqueous polymer dispersion is then cooled to 75 °C, and while doing so, 10.1 g of an aqueous solution of 10 wt% tert-butyl hydroperoxide and 9.9 g of an aqueous solution of FF6M (a reducing agent from Brüggemann GmbH & Co. KG) are simultaneously fed in over 10 minutes. Subsequently, the polymerization mixture is stirred at 70 °C for 20 minutes, cooled to room temperature, and mixed with 1.2 g of an aqueous solution of 5 wt% MBS (a biocide from Thor)

[0193] Feed 1 (a homogeneous mixture of the following substances):

[0194] 110.3 g of deionized water,

[0195] 12.0 g RS610 / A25,

[0196] 2.4 g of an aqueous solution of 30 wt% fatty alcohol polyoxyethylene ether sulfate (FES993 from BASF SE) ),

[0197] 196.9 g of styrene,

[0198] 196.9 g of 2-ethylhexyl acrylate,

[0199] 18.2 g PAM-200,

[0200] 14.1 g of methyl methacrylate,

[0201] 22.4 g of acetoacetoxyethyl methacrylate,

[0202] 6.2 g of acrylic acid.

[0203] Feed 2 (A homogeneous mixture of the following substances):

[0204] 42.4 g of deionized water,

[0205] 2.4 g RS610 / A25,

[0206] 0.6 g FES 993,

[0207] 12.1 g of styrene,

[0208] 133.3 g of n-butyl methacrylate.

[0209] Before further use, the obtained polymer dispersion was passed through a 125 μm filter, and the coagulum content was measured to be <0.1 wt%.

[0210] The solids content of the aqueous polymer dispersion obtained after filtration was 50.1 wt%. The weight-average particle size was measured to be 93 mm, and the fine coagulum content was measured to be 227 μg / g of the aqueous polymer dispersion. At the end of the first polymerization stage, the pH was measured to be 4.2, and at the end of the second polymerization stage, the pH was measured to be 6.1. The glass transition temperature Tg of the dispersed polymer 1 was -2.8 °C, and the glass transition temperature Tg 2 was 16 °C.

[0211] The solids content of the obtained aqueous polymer dispersion was generally determined by drying a certain amount (about 0.8 g) of the aqueous polymer dispersion to constant weight at a temperature of 160 °C using a Mettler Toledo HR73 moisture analyzer. Two measurements were made in each case. The values recorded in the examples are the average of the two measurements.

[0212] To determine the fine condensate content, in each case 3.0 g of the obtained aqueous polymer dispersion is diluted to 1500 g with deionized water. After pre-rinsing, 1000 g of the obtained diluted aqueous polymer dispersion is pumped through a Klotz LDS2x2 sensor at room temperature within 2.5 minutes using a Klotz PZG3 sample feeder. In combination with an evaluation unit and a control unit (ABAKUS) with a PC interface, values corresponding to the counted particles in the range of 10 - 500 μm are provided for each case.

[0213] It should be noted that aqueous polymer dispersions with a condensate content > 0.1 wt% and a fine condensate content > 1000 μg / g can lead to filtration problems (e.g., by clogging the filter) and are generally disadvantageous for their use in coating compositions by forming surface defects and / or blemishes in the coating.

[0214] The weight-average particle size is generally determined according to ISO 13321 using a Malvern high-performance particle sizer at a wavelength of 633 nm and a temperature of 22 °C.

[0215] The pH is generally measured using a calibrated 325XpH electrode from Mettler-Toledo GmbH.

[0216] The glass transition temperature is generally determined by differential scanning calorimetry (DSC) according to DIN EN ISO 11357-2 (2013-09) using a DSC Q2000 instrument from TA Instruments at a heating rate of 20 K / min. The midpoint temperature is used for the determination.

[0217] Example 2 (Dispersion 2)

[0218] The preparation of Example 2 was carried out completely analogously to the preparation of Example 1, except that acrylic acid was replaced by the same amount of methacrylic acid in Feed 1.

[0219] The solids content of the obtained polymer dispersion was 50.1 wt%. The weight-average particle size was 99 nm. The condensate content was < 0.1%, and the fine condensate content was determined to be 336 μg / g. The glass transition temperature Tg of the dispersion polymer 1 was -3.5 °C, and the glass transition temperature Tg 2 was 17 °C.

[0220] Example 3 (Dispersion 3)

[0221] The preparation of Example 3 was carried out completely analogously to the preparation of Example 1, except that Feeds 1 and 2 had the following composition:

[0222] Feed 1 (Homogeneous mixture of the following substances):

[0223] 110.3 g of deionized water,

[0224] 12.0 g RS610 / A25,

[0225] 2.4 g FES 993,

[0226] 168.6 g of styrene,

[0227] 176.5 g of 2-ethylhexyl acrylate,

[0228] 13.1 g PAM-200,

[0229] 73.1 g of methyl methacrylate,

[0230] 6.0 g of acetoacetoxyethyl methacrylate,

[0231] 6.7 g of acrylic acid.

[0232] Feed 2 (Homogeneous mixture of the following substances):

[0233] 42.4 g of deionized water,

[0234] 2.4 g RS610 / A25,

[0235] 0.6 g FES 993,

[0236] 72.6 g of styrene,

[0237] 52.4 g of n-butyl methacrylate,

[0238] 8.8 g of methyl methacrylate,

[0239] 22.2 g of 2-ethylhexyl acrylate.

[0240] The solids content of the obtained polymer dispersion was 49.7 wt%. The weight average particle size was measured to be 121 nm, the coagulum content was measured to be <0.1 wt%, and the fine coagulum content was measured to be 507 μg / g. The measured glass transition temperatures Tg 1 and Tg 2 were 6 °C and 23 °C.

[0241] Example 4 (Dispersion 4)

[0242] Under a nitrogen atmosphere, at 20 °C to 25 °C (room temperature), first add to a 2 L polymerization vessel equipped with a feeding device and a temperature control device

[0243] 339.0 g of deionized water, and

[0244] 10.3 g of RS610 / A25,

[0245] and heat to 90 °C with stirring. Once this temperature is reached, add 30.4 g of Feed 1, then add 33.8 g of a 2.2 wt% aqueous solution of ammonium persulfate over 2 minutes, and then stir the mixture at the above temperature for another 10 minutes. While adding the ammonium persulfate solution, start continuously adding 40.5 g of a 4.6 wt% aqueous ammonia solution at a constant flow rate over a period of 175 minutes.

[0246] After another 10 minutes of stirring time has passed, and while maintaining the temperature at 90 °C, continuously add the remainder of Feed 1 at a constant flow rate over 90 minutes. While adding the remainder of Feed 1, also start continuously adding 52.8 g of a 2.4 wt% aqueous solution of ammonium persulfate over 90 minutes. Then allow the polymerization mixture to react at 90 °C for another 15 minutes. Subsequently, and while maintaining the temperature at 90 °C, continuously add Feed 2 at a constant flow rate over 65 minutes. Simultaneously with Feed 2, continuously add 15.2 g of a 2.0 wt% aqueous solution of ammonium persulfate. After the addition of Feed 2 is complete, allow the polymerization mixture to react at 90 °C for another 20 minutes. Then cool the resulting aqueous polymer dispersion to 75 °C and simultaneously start continuously adding 16.2 g of a 6.8 wt% aqueous solution of tert-butyl hydroperoxide and 16.0 g of a 4 wt% aqueous solution of FF6 M while feeding. Subsequently, stir the polymerization mixture at 70 °C for 20 minutes, cool to room temperature, and mix with 14.7 g of a 0.4 wt% aqueous solution of MBS with stirring.

[0247] Feed 1 (A homogeneous mixture of the following substances):

[0248] 79.7 g of deionized water,

[0249] 12.9 g of RS610 / A25,

[0250] 2.6 g of FES 993,

[0251] 208.5 g of styrene,

[0252] 208.5 g of 2-ethylhexyl acrylate,

[0253] 19.5 g PAM - 200,

[0254] 15.2 g methyl methacrylate,

[0255] 24.1 g acetylacetoxyethyl methacrylate,

[0256] 6.7 g acrylic acid,

[0257] 6.5 g vinyltriethoxysilane.

[0258] Feed 2 (A homogeneous mixture of the following substances):

[0259] 33.5 g deionized water,

[0260] 2.6 g RS610 / A25,

[0261] 0.7 g FES 993,

[0262] 13.0 g styrene,

[0263] 143.3 g n - butyl methacrylate.

[0264] Before further use, the obtained polymer dispersion was passed through a 125 μm filter, and the coagulum content was measured to be < 0.1 wt%.

[0265] The solids content of the aqueous polymer dispersion obtained after filtration was 49.8 wt%. The weight - average particle size was measured to be 98 mm, and the fine coagulum content was measured to be 203 μg / g of the aqueous polymer dispersion. At the end of the first polymerization stage, the pH was measured to be 4.1, and at the end of the second polymerization stage, the pH was measured to be 6.0. The glass transition temperature Tg of the dispersed polymer 1 was - 5.4 °C, and the glass transition temperature Tg 2 was 13 °C.

[0266] Example 5 (Dispersion 5)

[0267] The preparation of Example 5 was carried out completely analogously to the preparation of Example 1, except that 32.6 g of a 5.3 wt% aqueous sodium hydroxide solution was used instead of ammonia water.

[0268] The obtained aqueous polymer dispersion has a solids content of 50.2% by weight after filtration. The weight-average particle size is measured to be 106 nm, the coagulum content is measured to be <0.1% by weight, and the fine coagulum content is measured to be 373 μg / g for the aqueous polymer dispersion. At the end of the first polymerization stage, the pH is measured to be 4.0, and at the end of the second polymerization stage, the pH is measured to be 5.9. The glass transition temperature Tg of the dispersed polymer 1 is -2.3 °C, and the glass transition temperature Tg 2 is 15.7 °C.

[0269] Example 6 (Dispersion 6)

[0270] The preparation of Example 6 is carried out completely analogously to the preparation of Example 1, except that 32.6 g of a 5.3% by weight aqueous solution of trimethylamine is used instead of ammonia water.

[0271] The obtained aqueous polymer dispersion has a solids content of 49.9% by weight after filtration. The weight-average particle size is measured to be 98 nm, the coagulum content is measured to be <0.1% by weight, and the fine coagulum content is measured to be 308 μg / g for the aqueous polymer dispersion. At the end of the first polymerization stage, the pH is measured to be 4.5, and at the end of the second polymerization stage, the pH is measured to be 6.2. The glass transition temperature Tg of the dispersed polymer 1 is -2.1 °C, and the glass transition temperature Tg 2 is 16.5 °C.

[0272] Comparative Example 1

[0273] The preparation of Comparative Example 1 is carried out completely analogously to the preparation of Example 1, except that Feed 1 does not contain PAM-200 and Feed 2 additionally contains 18.2 g PAM-200.

[0274] The polymerization mixture coagulated during Feed 1, so the experiment had to be aborted.

[0275] Comparative Example 2

[0276] The preparation of Comparative Example 2 is carried out completely analogously to the preparation of Example 1, except that Feed 1 does not contain acrylic acid and Feed 2 additionally contains 6.2 g of acrylic acid.

[0277] The polymerization mixture coagulated during Feed 1, so the experiment had to be aborted.

[0278] Comparative Example 3

[0279] The preparation of Comparative Example 3 is carried out completely analogously to the preparation of Example 1, except that 25.8 g is used in the initial feed FES 993 instead of 12.0 g RS610 / A25, a total of 28.1 g was used in Feed 1 FES 993, and a total of 5.7 g was used in Feed 2 FES 993, not used in each case RS610 / A25.

[0280] The polymerization mixture coagulated during Feed 1, so the experiment had to be aborted.

[0281] Comparative Example 4

[0282] The preparation of Comparative Example 4 was carried out completely analogously to the preparation of Example 1, except that the 5.3 wt% aqueous ammonia solution was not used, and in the first polymerization stage, the polymerization batch coagulated at a pH of 2.3, so the experiment had to be aborted.

[0283] Comparative Example 5 (Comparative Dispersion V5)

[0284] The preparation of Comparative Example 5 was carried out completely analogously to the preparation of Example 1, except that 16.3 g instead of 32.6 g of the 5.3 wt% aqueous ammonia solution was used.

[0285] The obtained aqueous polymer dispersion had a solids content of 50.1 wt% after filtration. The weight-average particle size was determined to be 90 nm, the coagulum content was determined to be <0.1 wt%, and the fine coagulum content was determined to be 689 μg / g of the aqueous polymer dispersion. At the end of the first polymerization stage, the pH was measured to be 2.9, and at the end of the second polymerization stage, the pH was measured to be 5.3. The glass transition temperature Tg of the dispersion polymer 1 was -2.8 °C, and the glass transition temperature Tg 2 was 15 °C.

[0286] Comparative Example 6 (Comparative Dispersion V6)

[0287] The preparation of Comparative Example 6 was carried out completely analogously to the preparation of Example 1, except that 48.9 g instead of 32.6 g of the 5.3 wt% aqueous ammonia solution was used.

[0288] The obtained aqueous polymer dispersion had a solids content of 49.8 wt% after filtration. The weight-average particle size was determined to be 96 nm, the coagulum content was determined to be 0.2 wt%, and the fine coagulum content was determined to be 1083 μg / g of the aqueous polymer dispersion. At the end of the first polymerization stage, the pH was measured to be 4.9, and at the end of the second polymerization stage, the pH was measured to be 7.3. The glass transition temperature Tg of the dispersion polymer 1 was -2.0 °C, and the glass transition temperature Tg 2is 15 °C.

[0289] Comparative Example 7 (Comparative Dispersion V7)

[0290] Under a nitrogen atmosphere and at room temperature, first add to a 2 l polymerization vessel equipped with a feeding device and a temperature control device

[0291] 260.0 g of deionized water, and

[0292] 12.0 g RS610 / A25,

[0293] and heat to 90 °C with stirring. Once this temperature is reached, add 30.4 g of Feed 1, then add 33.8 g of a 2.5 wt% aqueous solution of ammonium persulfate over 2 minutes, and then stir the mixture at the above temperature for another 10 minutes. While adding the ammonium persulfate solution, start continuously adding 32.6 g of a 5.3 wt% aqueous ammonia solution at a constant flow rate over a period of 175 minutes.

[0294] After another 10 minutes of stirring time and while maintaining the temperature at 90 °C, continuously add the remainder of Feed 1 at a constant flow rate over 175 minutes. While adding the remainder of Feed 1, also start continuously adding 60.7 g of a 2.5 wt% aqueous solution of ammonium persulfate over 170 minutes. After Feed 1 is completed, allow the polymerization mixture to react at 90 °C for another 20 minutes. Then cool the resulting aqueous polymer dispersion to 75 °C and simultaneously start continuously adding 10.1 g of a 10 wt% aqueous solution of tert-butyl hydroperoxide and 9.9 g of a 6 wt% aqueous solution of FF6M while feeding. Subsequently, stir the polymerization mixture at 70 °C for 20 minutes, cool to room temperature, and mix with 1.2 g of a 5 wt% aqueous solution of MBS with stirring.

[0295] Feed 1 (homogeneous mixture of the following substances):

[0296] 152.7 g of deionized water,

[0297] 14.4 g RS610 / A25,

[0298] 3.0 g FES 993,

[0299] 209.0 g of styrene,

[0300] 196.9 g of 2-ethylhexyl acrylate,

[0301] 18.2 g PAM-200,

[0302] 14.1 g of methyl methacrylate,

[0303] 133.3 g of n-butyl methacrylate,

[0304] 22.4 g of 2-acetoxyethyl methacrylate,

[0305] 6.2 g of acrylic acid.

[0306] The aqueous polymer dispersion obtained has a solids content of 50.0 wt% after filtration. The weight-average particle size is determined to be 98 nm, the coagulum content is determined to be <0.1 wt%, and the fine coagulum content is determined to be 467 μg / g for the aqueous polymer dispersion. The pH of the aqueous polymer dispersion is determined to be 5.1. The glass transition temperature Tg of the dispersed polymer is 14 °C.

[0307] Comparative Example 8 (Comparative Dispersion V8)

[0308] The preparation of Comparative Example 8 is carried out completely analogously to the preparation of Example 1, except that 96.9 g instead of 196.9 g of styrene and 296.9 g instead of 196.9 g of 2-ethylhexyl acrylate are used in Feed 1.

[0309] The aqueous polymer dispersion obtained has a solids content of 49.5 wt% after filtration. The weight-average particle size is determined to be 127 nm, the second part is at 880 nm, the coagulum content is determined to be 1 wt%, and the fine coagulum content is determined to be 8744 μg / g for the aqueous polymer dispersion. At the end of the first polymerization stage, the pH is determined to be 4.2, and at the end of the second polymerization stage, the pH is determined to be 6.7. The glass transition temperature Tg of the dispersed polymer 1 is -32 °C, and the glass transition temperature Tg 2 is -8 °C.

[0310] Performance Testing

[0311] For performance testing, clear varnishes and pigmented anticorrosive coatings are prepared from the aqueous polymer dispersions obtained in the examples and comparative examples. For this purpose, polymer dispersions 1 to 6 and V5 to V8 are first diluted with deionized water to a solids content of 49.5 wt%.

[0312] Preparation of Clear Varnish

[0313] The transparent varnishes were prepared as follows. In each case, 96.0 g of the aqueous polymer dispersions 1 to 6 and V5 to V8 diluted to 49.5 wt% were adjusted to pH 9.5 using 50 wt% aqueous dimethylethanolamine solution from Huntsman Corporation with stirring at room temperature, and then 3 g of an organic solvent from Eastman Chemical were added respectively. and 1 g of an anti-corrosion inhibitor from C.H. KG - COAT - CI LNF A4, and the mixture was mixed until homogeneous. The transparent varnishes obtained hereinafter are referred to as varnishes 1 to 6 and V5 to V8. Early water resistance test

[0314] The transparent varnishes 1 to 6 and V5 to V8 to be tested were applied respectively to the surface of a clean and grease - free ungalvanized steel plate of 200 x 80 mm using a box - blade coater, where the gap size was selected such that a dry layer thickness of 40 to 85 μm was obtained. The steel plates thus obtained (hereinafter referred to as steel plates 1 to 6 and V5 to V8) were dried in a climate control cabinet at 23 °C and 50% relative atmospheric humidity for 2 hours respectively. Then the actual test was carried out. The steel plates 1 to 6 and V5 to V8 were vertically placed in a water bath filled with deionized water to a filling height of 15 cm and kept at room temperature for 24 hours. Then the steel plates 1 to 6 and V5 to V8 were taken out of the water bath, gently dried with a soft cotton cloth, and the color tone change between the wetted area and the non - wetted area was evaluated. The color tone change was visually evaluated according to the following grades: 0 (no change) to 5 (obvious color tone change in the whole area). The results obtained are recorded in Table 1 below.

[0315] Table 1: Results of the early water resistance test

[0316] Preparation of the colored anti - corrosion coating

[0317]

[0318] In each case, 167.9 g of the aqueous polymer dispersions 1 to 6 and V5 to V8 diluted to 49.5 wt% were mixed with 1.5 g of a commercially available paint defoamer

[0319] 022 (Byk GmbH; a mixture of polysiloxane and hydrophobic solids in polyethylene glycol) at room temperature. Subsequently, 15.0 g of deionized water, 1.0 g of 25 wt% aqueous ammonia solution, 1.5 g Ultra PA4570 (BASF SE; a dispersion additive based on modified polyacrylate) and 4.5 g were added in each case using a Dispermat. CX 4231 (BASF SE; a dispersion additive of an aqueous ammonium salt solution based on an organic acid copolymer). While stirring, a mixture of 2.2 g of phenoxypropanol (film-forming aid) and 2.2 g of benzine (boiling range 180 °C to 210 °C; film-forming aid) was further incorporated. Subsequently, 25.5 g of hematite pigment was added. 130M (Lanxess AG), 10.8 g of talc 20M 2 (Luzenac; filler: magnesium silicate), 38.3 g L (Sachtleben, a filler based on barium sulfate and zinc sulfide) and 24.6 g ZMP (Heubach, an anticorrosive pigment based on zinc phosphate). Then 0.8 g 022 and a 1:1 mixture of 1.1 g of water and corrosion inhibitor L1 (C.H. KG) were added. The entire mixture was premixed in a dissolver with a toothed disk (diameter 5 cm; 2000 revolutions per minute) for 10 minutes, and then dispersed with an identical PTFE disk (diameter 5 cm; 2300 revolutions per minute) and 200 g of glass beads (diameter 3 mm) for 20 minutes. Then the glass beads were removed by sieving. Finally, each batch was mixed with a mixture of 1.8 g of 25 wt% aqueous ammonia solution and 0.3 g of an aqueous solution of a commercially available urethane-based thickener ( PU 1280, BASF SE) and 1.0 g of butyl glycol (solvent), and the pH was optionally adjusted to 9.5 using 25 wt% aqueous ammonia solution. The obtained anticorrosive preparations 1 to 6 and V5 to V8 had a solids content of 61 wt% and a pigment / volume concentration of 23%. The obtained anticorrosive preparations were diluted with deionized water to a viscosity of approximately 300 mPas (measured at room temperature using a Rotothinner 455N sphere from Sheen Instruments), and the respective solids contents were determined.

[0320] It should be noted in this context that the anticorrosive preparation V6 thickened immediately after preparation, so this preparation could not be used for coating steel plates.

[0321] Salt spray test

[0322] For testing the anti-corrosion performance, a salt spray test was carried out using a 5 wt% aqueous sodium chloride solution according to DIN EN ISO 7253 (test duration 360 hours). For this purpose, the diluted anti-corrosion preparations 1 to 6 and V5, V7 and V8 were applied to one side of a clean ungalvanized steel sheet measuring 200 x 80 mm using a box doctor blade coater, where in each case the gap size was selected such that a dry layer thickness of 60 to 100 μm was obtained. The test plates obtained after coating were stored, and thus dried in a climatic control cabinet at 23 °C and 50% relative atmospheric humidity for 6 days. Then the coated test plates were stored at 50 °C for another 24 hours. After cooling to room temperature, to avoid corrosion, the reverse side of each test plate was coated with a solvent-based paint and then dried at room temperature for 24 hours. Before the actual test, the edges of each test plate were taped with plastic film. Then a scriber was used to scratch the coated side of each test plate down to the steel sheet, and salt spray was applied for 360 hours. The obtained test plates 1 to 6 and V5, V7 and V8 were evaluated by optically comparing the test samples with the standards specified in DIN EN ISO 7253. The corrosion performance of each test plate was evaluated as follows by the cross-cut test, with reference to the subsurface corrosion, surface corrosion and adhesion around the notch.

[0323] Subsurface corrosion around the notch (according to DIN EN ISO 4628-8; 2013)

[0324] The corrosion formed below the coating starts from the artificially damaged area. The values recorded in Table 2 represent the maximum distance in millimeters measured from the notch of the iron oxide thus formed. Before inspection, the loose coating around the notch was removed using tape. The lower the measured value, the better the evaluation result of the present invention.

[0325] Surface corrosion:

[0326] The measurement was carried out by visually observing the ratio of the corroded surface area to the total surface area of the test plate. The values recorded in Table 2 represent the percentage of the corroded surface area. In this case, the lower the measured value, the better the evaluation result.

[0327] Adhesion (cross-cut test according to DIN EN ISO 2409) :

[0328] The adhesion of the anti-corrosion coating to the substrate was determined by the cross-cut test. For this purpose, after the salt spray test, a grid consisting of multiple cuts (row spacing 2 mm) was cut into each lightly dried anti-corrosion coating, covered with tape, and then the tape was removed. After removing the tape, the appearance of the grid was evaluated. A score of 0 to 5 was given according to the following scale:

[0329] Gt 0 The edges of the cuts are completely smooth and no squares of the grid are peeled off.

[0330] The Gt 1 coating peeled off along the notch edge, but the peeled area was not more than 15% of the cross-hatched area.

[0331] For Gt 2, the peeled grid area was more than 15% but not more than 35%.

[0332] For Gt 3, along the notch direction, the coating had partially or completely peeled off in the form of wide strips,

[0333] or some squares had partially or completely peeled off.

[0334] For Gt 4, the affected cross-hatched area was more than 35% but not more than 65%.

[0335] Gt 5 was any peeling that could be classified as more severe than Gt 4.

[0336] The results obtained were also recorded in Table 2 below.

[0337] Table 2: Results of salt spray test

[0338]

[0339] Determination of film hardness

[0340] The film hardness was determined by the pendulum damping test according to DIN EN ISO 1522. The pendulum damping test was carried out in such a way that diluted anticorrosive preparations 1 to 6 and V5, V7 and V8 were applied to one side of a clean ungalvanized steel sheet of 200 x 80 mm using a box doctor coater, where the gap size was selected in each case such that a dry layer thickness of 60 to 100 μm was obtained. The obtained coated test plates were stored in a drying cabinet at 50 °C for 20 hours and then cooled to room temperature. The pendulum damping test according to DIN EN ISO 1522 was carried out on the obtained coated steel sheets. The results obtained during the test of the steel sheets coated with anticorrosive preparations 1 to 6 and V5, V7 and V8 were recorded in Table 3. The higher the number of pendulum strokes, the harder the coating. The results obtained during the test of the steel sheets coated with anticorrosive preparations 1 to 6 and V5, V7 and V8 were recorded in Table 3. The higher the number of pendulum strokes, the harder the coating.

[0341] Table 3: Film hardness results

[0342]

[0343] It is clearly seen from the results of the performance tests that the coatings prepared with the anticorrosive preparations using the polymer dispersions of the present invention showed significantly better values in terms of subsurface corrosion around the notch, surface corrosion, cross-hatch test and film hardness compared to the anticorrosive preparations prepared with the corresponding comparative dispersion systems.

Claims

1. A process for preparing an aqueous polymer dispersion by free-radical-initiated aqueous emulsion polymerization, wherein in polymerization stage 1: in a first polymerization stage, the following are subjected to free-radical polymerization in an aqueous medium in the presence of at least one phosphorus-containing dispersion aid to provide polymer 1: at least one α,β-monoethylenically unsaturated C3- to C6-monocarboxylic or dicarboxylic acid in an amount of ≥ 1.0% by weight and ≤ 3.0% by weight as monomer A1, at least one ethylenically unsaturated compound having at least one phosphorus-containing group in an amount of ≥ 1.5% by weight and ≤ 6.0% by weight as monomer A2, at least one ethylenically unsaturated compound different from monomers A1 and A2 in an amount of ≥ 91.0% by weight and ≤ 97.5% by weight as monomer A3, wherein the amounts of monomers A1 to A3 together as total monomer amount 1 amount to 100% by weight, and subsequently in polymerization stage 2: in a second polymerization stage, the following are subjected to free-radical polymerization in the presence of polymer 1 to provide polymer 2: at least one α,β-monoethylenically unsaturated C3- to C6-monocarboxylic or dicarboxylic acid in an amount of ≤ 0.1% by weight as monomer B1, at least one ethylenically unsaturated compound having at least one phosphorus-containing group in an amount of ≤ 0.1% by weight as monomer B2, at least one ethylenically unsaturated compound different from monomers B1 and B2 in an amount of ≥ 99.8% by weight and ≤ 100% by weight as monomer B3, wherein the amounts of monomers B1 to B3 together as total monomer amount 2 amount to 100% by weight, provided that · the type and amount of monomers A1 to A3 are selected such that the glass transition temperature Tg of the resulting polymer 1 1 is in the range of ≥ -10 °C and ≤ 15 °C, · the type and amount of monomers B1 to B3 are selected such that the glass transition temperature Tg of the resulting polymer 2 2 is ≥ 10 °C and ≤ 60 °C and is at least 10 °C higher than 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% by weight to 85% by weight to 15% by weight to 30% by weight, and · the amount of the at least one phosphorus-containing dispersant is ≥ 0.5% by weight, based on the sum of total monomer amount 1 and total monomer amount 2 as total monomer amount; wherein both polymerization stages 1 and 2 are carried out at a pH in the range of ≥ 3 and ≤ 8 measured at room temperature.

2. The method according to claim 1, wherein the monomer A1 used is acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, and / or crotonic acid.

3. The method according to claim 1 or 2, wherein the monomer A2 used is vinylphosphonic acid and / or (meth)acryloyloxy(poly)alkoxy phosphate.

4. The method according to claim 1 or 2, wherein at least one of the monomers A3 is selected to an extent of ≥80% by weight from n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, styrene, and methyl methacrylate.

5. The method according to claim 1 or 2, wherein the types and amounts of monomers A1 to A3 and B1 to B3 are selected such that the glass transition temperature Tg of the resulting polymer 1 1 is in the range of ≥ -5°C and ≤ 10°C, and the glass transition temperature Tg of the resulting polymer 2 2 is in the range of ≥ 10°C and ≤ 40°C.

6. The method according to claim 1 or 2, wherein no monomers B1 and B2 are used.

7. The method according to claim 1, wherein a base having a boiling point ≤ 20°C measured at an absolute pressure of 1.013 bar is used for pH adjustment.

8. The method according to claim 1 or 2, wherein at least one of the monomers A3 is selected to an extent of > 0% by weight and ≤ 20% by weight from 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.

9. An aqueous polymer dispersion obtained by the method according to any one of claims 1 to 8.

10. A polymer powder obtained by drying the aqueous polymer dispersion according to claim 9.

11. Use of the aqueous polymer dispersion according to claim 9 or the polymer powder according to claim 10 as a binder in the preparation of adhesives, sealants, plasters, paper coating slurries, fibrous nonwovens, and paints, and in sand consolidation, and as a component in the preparation of textile or leather auxiliaries and impact modifiers.

12. Use of the aqueous polymer dispersion according to claim 9 or the polymer powder according to claim 10 as a binder in the preparation of flexible roof coatings.

13. Use of the aqueous polymer dispersion according to claim 9 or the polymer powder according to claim 10 for the modification of mineral binders and plastics.

14. Use of the aqueous polymer dispersion according to claim 9 or the polymer powder according to claim 10 as a binder in an aqueous anti-corrosion preparation for metal surfaces.

15. A method of coating a metal surface, wherein an aqueous anti-corrosion preparation comprising the aqueous polymer dispersion according to claim 9 or the polymer powder according to claim 10 is applied to the metal surface and then dried.

16. An aqueous anti-corrosion preparation comprising the aqueous polymer dispersion according to claim 9 or the polymer powder according to claim 10.

Images