MULTI-STAGE COPOLYMERS AS BINDERS FOR COATING COMPOSITIONS

Description

[0001] The invention relates to multistage copolymers of vinyl acetate and (meth)acrylic acid esters or vinyl aromatics in the form of aqueous dispersions, processes for their preparation and their use, for example, as binders for aqueous coating compositions, in particular with a high pH, ​​for example for emulsion paints or plasters.

[0002] Conventional aqueous coatings, such as emulsion paints or plasters, with vinyl acetate copolymers as binders are usually protected against biocontamination by adding biocides, such as isothiazolinones, as in-can preservatives to inhibit the growth of microorganisms and ensure storage stability. However, such biocides have been under increased regulatory pressure for some time, resulting in increasing market demand for preservative-free aqueous coatings. One approach to this is to achieve in-can preservation by adjusting the aqueous coatings to high pH values, for example, to pH values ​​of 10 to 11.5, thus preventing the growth of microorganisms, achieving storage stability, and thus eliminating the need for preservatives.

[0003] For preservative-free coating materials with high pH values, styrene-acrylate copolymers or poly(meth)acrylates are commonly used as binders. However, such copolymers do not achieve the pigment-binding capacity of vinyl acetate copolymers. Conventional vinyl acetate copolymers, however, are unstable at pH values ​​of, for example, 10 to 11.5, which is why such vinyl acetate copolymers are not suitable for coating materials with high pH values. Such vinyl acetate-based binders hydrolyze in alkaline formulations, lowering the pH of the alkaline coating material, so that the coating material is no longer adequately protected against biocontamination over time. Therefore, there is a need to provide storage-stable, water-based coating materials with high pH values ​​that contain vinyl acetate copolymers as binders.

[0004] Preservative-free emulsion paints with high pH values ​​and pure acrylate or styrene-acrylate copolymers as binders have been widely described. For example, WO2002000798 describes corresponding emulsion paints with styrene-acrylate dispersions as binders for preservative-free high-pH paints, particularly for interior use, with water glass as an additive. The preservative-free high-pH emulsion paints of US10988627 and DE102014013455 specifically contain acrylate or styrene-acrylate copolymers as binders and alkali metal alkyl siliconate or siliconates in general as additives to stabilize the emulsion paints, particularly the pH value. Further biocide-free high-pH dispersion paints with (styrene)acrylate copolymers are disclosed, for example, in DE202017106112, DE202018101199.EP3974479 mentions preservative-free coating compositions with a high pH value that contain hybrid binders made of silicon dioxide and (meth)acrylate polymers and optionally other polymers. DE102017008984 also deals with storage-stable coating compositions. US2021269653 AA describes corresponding dispersion paints containing emulsion polymers based on ethylhexyl acrylate, butyl acrylate, and vinyl aromatics.

[0005] US2021002506 AA describes the production of styrene-acrylate copolymers by multi-stage emulsion polymerization, wherein styrene and acrylates are used as main monomers in all polymerization stages, as well as the use of these multi-stage polymers in biocide-free gloss and semi-gloss coating compositions adjusted to a pH of at least 10 by means of water-soluble alkali metal or alkaline earth metal alkyl siliconate.

[0006] High-pH emulsion paints containing vinyl acetate copolymers are also known from individual publications. For example, US Pat. No. 778 9959 recommends copolymers of vinyl esters of short-chain carboxylic acids (C 1 -C 4 carbon atoms), vinyl esters of long-chain carboxylic acids (C 5 -C 18 carbon atoms), and olefins as binders for preservative-free emulsion paints or varnishes. US Pat. No. 1,089,9918 describes water-resistant copolymers comprising a first polymer phase based on vinyl esters, optionally an intermediate polymer phase, and a second polymer phase based on (meth)acrylic acid esters and / or styrene, wherein the intermediate polymer phase mediates between the hydrophilicity and hydrophobicity, and the second polymer phase specifically contains acid monomer units.

[0007] US9902785 recommends the addition of a two-stage copolymer to improve the mechanical or fire-retardant properties and to reduce the soiling tendency or water absorption of mortars or paint coatings. This copolymer can be obtained by copolymerizing vinyl esters and ethylene in the first stage and (meth)acrylic acid esters in the second stage. Optionally, any other monomers can be used in the first and / or second stages, such as epoxy-, silicon-, carboxylic acid-, sulfonic acid-, phosphonic acid-, hydroxy-, or N-methylol-functional monomers, or even polyethylenically unsaturated monomers. US8993668 describes something similar to provide coatings with improved tensile strength.To reduce the water absorption of paints or mortars, US2021230315 teaches multistage copolymers with average particle diameters of < 200 nm and pH values ​​of 2.5 to 8, produced by multistage emulsion polymerization of 1) vinyl acetate and long-chain vinyl esters and 2) (meth)acrylic acid esters or vinyl aromatics and acid monomers. Acid monomers in the second stage are therefore essential.

[0008] The documents EP-A1-1308468, WO-A2-2004 / 065441, EP-A1-2017313 and EP-A2-1153979 describe multi-stage copolymers based on vinyl acetate, ethylene, silicon-functional monomers and (meth)acrylates in general, but not all details of the different polymerization stages.

[0009] Against this background, the task was to provide vinyl acetate copolymers in the form of aqueous dispersions which, when used in emulsion paints with pH values ​​of 10 to 11.5, produce paints with high pH stability and also high pigment binding capacity and, after application, also lead to paint coatings with advantageous wet abrasion resistance and high hiding power.

[0010] The invention relates to processes for the preparation of multistage copolymers in the form of aqueous dispersions by multistage, radically initiated emulsion polymerization, characterized in that a) in a first stage, 20 to 75% by weight of vinyl acetate, optionally ethylene and optionally one or more further ethylenically unsaturated monomers are polymerized, b) in a second stage, in the presence of the polymer from the first stage a) 1 to 25% by weight of vinyl acetate, 0.01 to 2% by weight of one or more ethylenically unsaturated silicon-functional monomers and optionally one or more further ethylenically unsaturated monomers are polymerized and c) in a third stage, in the presence of the polymer from the second stage b) 5 to 40% by weight of one or more monomers selected from the group comprising esters of acrylic acid, esters of methacrylic acid and vinyl aromatics and optionally one or more further ethylenically unsaturated monomers are polymerized, with the proviso that in the third stage c) no ethylenically unsaturated carboxylic acid is polymerized, where the data in wt.% refer to the total weight of the monomers used in steps a) to c).

[0011] The invention further relates to multistage copolymers in the form of aqueous dispersions obtainable by the aforementioned multistage, radically initiated emulsion polymerization process.

[0012] In the first stage a), preferably 30 to 65 wt.%, particularly preferably 35 to 60 wt.% and most preferably 40 to 55 wt.% of vinyl acetate are polymerized, based on the total weight of the monomers used in stages a) to c).

[0013] In the first stage a), preferably ≥ 40 wt.%, particularly preferably 50 to 90 wt.% and most preferably 60 to 80 wt.% of vinyl acetate are polymerized, based on the total weight of the monomers of stage a).

[0014] In the first stage a), preferably 1 to 40 wt.%, particularly preferably 2 to 30 wt.% and most preferably 5 to 15 wt.% of ethylene are polymerized, based on the total weight of the monomers used in stages a) to c).

[0015] In the first stage a), preferably 1 to 30 wt.%, particularly preferably 5 to 25 wt.% and most preferably 10 to 20 wt.% of ethylene is polymerized, based on the total weight of the monomers of stage a).

[0016] Preferred further ethylenically unsaturated monomers for the first stage a) are vinyl esters of unbranched or branched carboxylic acids having 3 to 18 C atoms and ethylenically unsaturated acids.

[0017] Preferably, in the first stage a) one or more vinyl esters of unbranched or branched carboxylic acids having 3 to 18 C atoms and one or more ethylenically unsaturated acids are used as further monomers.

[0018] Preferred vinyl esters of unbranched or branched carboxylic acids with 3 to 18 carbon atoms are vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate, 1-methylvinyl acetate, vinyl pivalate, and vinyl esters of α-branched monocarboxylic acids with 9 to 11 carbon atoms, for example VeoVa9R or VeoVa10R (trade names of Momentive). Vinyl versatate and vinyl laurate are particularly preferred.

[0019] Preferred ethylenically unsaturated acids are ethylenically unsaturated carboxylic acids, ethylenically unsaturated phosphonic and phosphoric acids and in particular ethylenically unsaturated sulfonic acids and their salts.

[0020] Examples of ethylenically unsaturated sulfonic acids are vinylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-acryloyloxyethanesulfonic acid, and 2-methacryloyloxyethanesulfonic acid, 2-acryloyloxy- and 3-methacryloyloxypropanesulfonic acid. Vinylsulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid are preferred.

[0021] Examples of ethylenically unsaturated carboxylic acids, such as mono- or dicarboxylic acids, are acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid. Acrylic acid, methacrylic acid, and fumaric acid are preferred.

[0022] Examples of ethylenically unsaturated phosphonic acids or phosphoric acids are vinylphosphonic acid, esters of phosphonic acid or phosphoric acid with hydroxyalkyl (meth)acrylates and ethylenically unsaturated polyethoxyalkyl ether phosphates.

[0023] In addition to or instead of the above-mentioned acids, their salts can also be used, preferably their alkali or ammonium salts, particularly preferably their sodium salts, such as, for example, the sodium salts of vinylsulfonic acid and 2-acrylamidopropanesulfonic acid.

[0024] The other ethylenically unsaturated monomers of the first stage a) are generally different from vinyl acetate and ethylene.

[0025] In the first stage a), preferably 0 to 25% by weight, particularly preferably 0.1 to 20% by weight and most preferably 1 to 15% by weight of further ethylenically unsaturated monomers of the first stage a), in particular vinyl esters of unbranched or branched carboxylic acids having 3 to 18 C atoms, are polymerized, based on the total weight of the monomers used in stages a) to c).

[0026] In the first stage a), preferably 0 to 40 wt.%, particularly preferably 0.1 to 30 wt.% and most preferably 1 to 20 wt.% of further ethylenically unsaturated monomers of the first stage a), in particular vinyl esters of unbranched or branched carboxylic acids having 3 to 18 C atoms, are polymerized, based on the total weight of the monomers of stage a).

[0027] In the first stage a), preferably 0 to 2 wt.%, particularly preferably 0.01 to 1 wt.% and most preferably 0.1 to 0.5 wt.% of ethylenically unsaturated acids are polymerized, based on the total weight of the monomers used in stages a) to c).

[0028] In the first stage a), preferably 0 to 10 wt.%, particularly preferably 0.01 to 5 wt.% and most preferably 0.1 to 2 wt.% of ethylenically unsaturated acids are polymerized, based on the total weight of the monomers of stage a).

[0029] Preferably, no ethylenically unsaturated carboxylic acids are copolymerized in the first step a).

[0030] The further ethylenically unsaturated monomers of the first stage a) preferably do not comprise any ethylenically unsaturated silicon-functional monomers and / or any ethylenically unsaturated epoxy-functional comonomers.

[0031] Examples of ethylenically unsaturated epoxy-functional comonomers are glycidyl methacrylate and glycidyl acrylate. Examples of ethylenically unsaturated silicon-functional monomers are listed below.

[0032] Preferably, the further ethylenically unsaturated monomers of the first stage a) do not comprise esters of acrylic acid or methacrylic acid, nor vinylaromatics. Preferably, no esters of acrylic acid or methacrylic acid, nor vinylaromatics, are copolymerized or used in the first stage a).

[0033] In the second stage b), preferably 2 to 20% by weight, particularly preferably 5 to 15% by weight, of vinyl acetate are polymerized, based on the total weight of the monomers used in stages a) to c).

[0034] In the second stage b), preferably 40 to 99.9 wt.%, more preferably 50 to 99 wt.%, even more preferably 55 to 95 wt.%, particularly preferably 60 to 90 wt.%, very particularly preferably 65 to 85 wt.% and most preferably 70 to 80 wt.% of vinyl acetate are polymerized, based on the total weight of the monomers of stage b).

[0035] Alternatively, in the second stage b), preferably 40 to 99.99 wt.%, more preferably 80 to 99.9 wt.%, particularly preferably 85 to 99.5 wt.% and most preferably 90 to 99 wt.% of vinyl acetate are polymerized, based on the total weight of the monomers of stage b).

[0036] Ethylenically unsaturated silicon-functional monomers of the second stage b) are, for example, ethylenically unsaturated silicon compounds of the general formula R 1< SiR 2< 0-2 (OR 3< ) 1-3 , where R 1< has the meaning CH 2 =CR 4< -(CH 2 ) 0-1 or CH 2 =CR 4< CO 2 (CH 2 ) 1-3 , R 2< has the meaning C 1 - to C 3 -alkyl radical, C 1 - to C 3 -alkoxy radical or halogen, preferably C 1 or Br, R 3< is an unbranched or branched, optionally substituted alkyl radical having 1 to 12 C atoms, preferably 1 to 3 C atoms, or an acyl radical having 2 to 12 C atoms, where R 3< can optionally be interrupted by an ether group, and R 4< stands for H or CH 3.

[0037] Preferred ethylenically unsaturated silicon-functional monomers are γ-acryl- or γ-methacryloxypropyltri(alkoxy)silanes, α-methacryloxymethyltri(alkoxy)silanes, γ-methacryloxypropylmethyldi(alkoxy)silanes; vinylsilanes such as vinylalkyldi(alkoxy)silanes and vinyltri(alkoxy)silanes, wherein, for example, methoxy, ethoxy, methoxyethylene, ethoxyethylene, methoxypropylene glycol ether or ethoxypropylene glycol ether radicals can be used as alkoxy groups.

[0038] Beispiele für bevorzugte ethylenisch ungesättigte siliciumfunktionelle Monomere sind 3-Methacryloxypropyltrimethoxysilan, 3-Methacryloxypropylmethyldimethoxysilan, Vinyltrimethoxysilan, Vinylmethyldimethoxysilan, Vinyltriethoxysilan, Vinylmethyldiethoxysilan, Vinyltripropoxysilan, Vinyltriisopropoxysilan, Vinyltris-(1-methoxy)-isopropoxysilan, Vinyltributoxysilan, Vinyltriacetoxysilan, Methacryloxymethyltrimethoxysilan, 3-Methacryloxypropyl-tris(2-methoxyethoxy)silan, Vinyltrichorsilan, Vinylmethyldichlorsilan, Vinyltris-(2-methoxyethoxy)silan, Trisacetoxyvinylsilan, Allylvinyltrimethoxysilan, Allyltriacetoxysilan, Vinyldimethylmethoxysilan, Vinyldimethylethoxysilan, Vinylmethyldiacetoxysilan, Vinyldimethylacetoxysilan, Vinylisobutyldimethoxysilan, Vinyltriisopropyloxysilan, Vinyltributoxysilan, Vinyltrihexyloxysilan, Vinylmethoxydihexoxysilan, Vinyltrioctyloxysilan, Vinyldimethoxyoctyloxysilan, Vinylmethoxydioctyloxysilan, Vinylmethoxydilauryloxysilan,Vinyldimethoxylauryloxysilane as well as polyethylene glycol-modified vinylsilanes.

[0039] Suitable ethylenically unsaturated silicon-functional monomers of the second stage b) are also silane-group-containing (meth)acrylamides of the general formula CH 2 =CR 5 -CO-NR 6< -R 7< -SiR 8< n -(R 9< ) 3-m , where n= 0 to 4, m= 0 to 2, R 5< is either H or a methyl group, R 6< is H or an alkyl group having 1 to 5 C atoms; R 7< is an alkylene group with 1 to 5 carbon atoms or a bivalent organic group in which the carbon chain is interrupted by an O or N atom, R 8< is an alkyl group with 1 to 5 carbon atoms, R 9< is an alkoxy group with 1 to 40 carbon atoms, which may be substituted by further heterocycles. In monomers containing two or more R 5< or R 9< groups, these may be identical or different.

[0040] Beispiele für solche (Meth)acrylamido-alkylsilane sind: 3-(Meth)acrylamido-propyltrimethoxysilan, 3-(Meth)acrylamidopropyltriethoxysilan, 3-(Meth)acrylamido-propyltri(β-methoxyethoxy)silan, 2-(Meth)acrylamido-2-methylpropyltrimethoxysilan, 2-(Meth)acrylamido-2-methylethyltrimethoxysilan, N-(2-(Meth)acrylamido-ethyl)aminopropyltrimethoxysilan, 3-(Meth)ac-rylamido-propyltriacetoxysilan, 2-(Meth)acrylamido-ethyltrimethoxysilan, 1-(Meth)acrylamido-methyltrimethoxysilan, 3-(Meth)acrylamido-propylmethyldimethoxysilan, 3-(Meth)acryl-amido-propyldimethylmethoxysilan, 3-(N-Methyl-(Meth)acryl-amido)-propyltrimethoxysilan, 3-((Meth)acrylamido-methoxy)-3-hydroxypropyltrimethoxysilan, 3-((Meth)acrylamido-methoxy)-propyltrimethoxysilan, N,N-Dimethyl-N-trimethoxysilylpropyl-3-(Meth)acrylamido-propylammoniumchlorid und N-N-Dimethyl-N-tri-methoxysilylpropyl-2-(Meth)acrylamido-2-methylpropylammoniumchlorid.

[0041] Most preferred ethylenically unsaturated silicon-functional monomers are vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyltris-(1-methoxy)-isopropoxysilane, methacryloxypropyltris(2-methoxyethoxy)silane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane and methacryloxymethyltrimethoxysilane and mixtures thereof.

[0042] In the second stage b), preferably 0.01 to 2 wt.%, particularly preferably 0.05 to 1.5 wt.% and most preferably 0.1 to 1.0 wt.% of ethylenically unsaturated silicon-functional monomers are polymerized, based on the total weight of the monomers used in stages a) to c).

[0043] In the second stage b), preferably 0.1 to 20 wt.%, particularly preferably 0.5 to 15 wt.% and most preferably 1 to 10 wt.% of ethylenically unsaturated silicon-functional monomers are polymerized, based on the total weight of the monomers of stage b).

[0044] Preferred further ethylenically unsaturated monomers for the second stage b) are one or more vinyl esters of unbranched or branched carboxylic acids having 3 to 18 carbon atoms, one or more ethylenically unsaturated acids, and optionally one or more ethylenically unsaturated epoxy-functional comonomers. These monomers can, for example, take on the preferred, particularly preferred, and exemplary embodiments listed above.

[0045] The other ethylenically unsaturated monomers of the second stage b) are generally different from vinyl acetate and ethylenically unsaturated silicon-functional monomers.

[0046] In the second stage b), preferably 0 to 15 wt.%, particularly preferably 0.5 to 10 wt.% and most preferably 1.0 to 5 wt.% of further ethylenically unsaturated monomers of the second stage b) are polymerized, based on the total weight of the monomers used in stages a) to c).

[0047] In the second stage b), preferably 0 to 30 wt.%, particularly preferably 0.1 to 20 wt.% and most preferably 1 to 10 wt.% of further ethylenically unsaturated monomers of the second stage b) are polymerized, based on the total weight of the monomers of stage b).

[0048] In the second stage b), preferably up to 2 wt.%, particularly preferably 0.01 to 1.5 wt.% and most preferably 0.1 to 1.0 wt.% of ethylenically unsaturated epoxy-functional comonomers are polymerized, based on the total weight of the monomers used in stages a) to c).

[0049] In the second stage b), preferably 0.1 to 20 wt.%, particularly preferably 0.5 to 15 wt.% and most preferably 1 to 10 wt.% of ethylenically unsaturated epoxy-functional comonomers are polymerized, based on the total weight of the monomers of stage b).

[0050] Particularly preferably, no ethylenically unsaturated acids, in particular no ethylenically unsaturated carboxylic acids, are used and / or copolymerized in the second stage b).

[0051] Most preferably, none of the above-mentioned further ethylenically unsaturated monomers are used and / or copolymerized in the second step b).

[0052] Esters of acrylic acid or methacrylic acid that do not carry an epoxy group, as well as vinylaromatics, are preferably not included in the further ethylenically unsaturated monomers of the second stage b). More preferably, the further ethylenically unsaturated monomers of the second stage b) do not include esters of acrylic acid or methacrylic acid and no vinylaromatics. The further ethylenically unsaturated monomers of the second stage b) also particularly preferably do not include any ethylenically unsaturated epoxy-functional comonomers. Preferably, no additional ethylene is introduced in the second stage b).

[0053] Esters of acrylic acid or methacrylic acid of the third stage c) are, for example, esters of unbranched or branched alcohols having 1 to 15 C atoms, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate.

[0054] Particularly preferred is the copolymerization of 2-ethylhexyl acrylate and / or n-butyl acrylate and one or more esters of acrylic acid or methacrylic acid selected from the group comprising methyl methacrylate, tert-butyl methacrylate, tert-butyl acrylate, lauryl acrylate, stearyl acrylate and methyl methacrylate.

[0055] Methylstyrene and vinyltoluene, and especially styrene, are preferred as vinylaromatics.

[0056] Preference is also given to the copolymerization of one or more esters of (meth)acrylic acid and one or more vinyl aromatics, in particular styrene.

[0057] In the third stage c), preferably 5 to 40 wt.%, particularly preferably 10 to 35 wt.% and most preferably 20 to 30 wt.% of one or more monomers selected from the group comprising esters of (meth)acrylic acid and vinyl aromatics are polymerized, based on the total weight of the monomers used in stages a) to c).

[0058] In the third stage c), preferably 70 to 100 wt.%, particularly preferably 80 to 100 wt.% and most preferably 95 to 100 wt.% of one or more monomers selected from the group comprising esters of (meth)acrylic acid and vinyl aromatics are polymerized, based on the total weight of the monomers of stage c).

[0059] Preferred further ethylenically unsaturated monomers for the third step c) are one or more ethylenically unsaturated silicon-functional monomers and optionally one or more ethylenically unsaturated epoxy-functional comonomers. These monomers can, for example, take on the preferred, particularly preferred, and exemplary embodiments listed above.

[0060] The other ethylenically unsaturated monomers of the third stage c) are generally different from vinylaromatics. The other ethylenically unsaturated monomers of the third stage c) preferably comprise exclusively ethylenically unsaturated epoxy-functional comonomers, as esters of acrylic acid or methacrylic acid.

[0061] In the third stage c), preferably 0.01 to 2 wt.%, particularly preferably 0.05 to 1.5 wt.% and most preferably 0.1 to 1.0 wt.% of ethylenically unsaturated silicon-functional monomers are polymerized, based on the total weight of the monomers used in stages a) to c).

[0062] In the third stage c), preferably 0.1 to 20 wt.%, particularly preferably 0.5 to 15 wt.% and most preferably 1 to 10 wt.% of ethylenically unsaturated silicon-functional monomers are polymerized, based on the total weight of the monomers of stage c).

[0063] In the third stage c), preferably up to 2 wt.%, particularly preferably 0.01 to 1.5 wt.% and most preferably 0.1 to 1.0 wt.% of ethylenically unsaturated epoxy-functional comonomers are polymerized, based on the total weight of the monomers used in stages a) to c).

[0064] In the third stage c), preferably 0.1 to 20 wt.%, particularly preferably 0.5 to 15 wt.% and most preferably 1 to 10 wt.% of ethylenically unsaturated epoxy-functional comonomers are polymerized, based on the total weight of the monomers of stage c).

[0065] Preferably, no ethylenically unsaturated acids are used and / or copolymerized in the third step c).

[0066] It is also preferred not to use and / or copolymerise vinyl esters of unbranched or branched carboxylic acids having 1 to 18 C atoms, in particular no vinyl acetate, in the third stage c).

[0067] Preferably, no additional ethylene is introduced in the third stage c).

[0068] Esters of acrylic acid or methacrylic acid that do not carry an epoxy group, as well as vinylaromatics, are preferably not included in the further ethylenically unsaturated monomers of the third stage c). Particularly preferably, the further ethylenically unsaturated monomers of the third stage c) do not include esters of acrylic acid or methacrylic acid and vinylaromatics.

[0069] With the preferred embodiments regarding acid monomers or silicon-functional monomers in steps a) to c), the object of the invention can be achieved even better, in particular the wet abrasion resistance can be improved.

[0070] Multistage copolymers are based on preferably 40 to 80 wt.%, in particular 50 to 70 wt.% vinyl acetate, 0.01 to 3 wt.%, in particular 0.1 to 0.5 wt.% ethylenically unsaturated silicon-functional monomers, 10 to 40% by weight, in particular 20 to 35% by weight of monomers selected from the group comprising esters of (meth)acrylic acid and vinyl aromatics, optionally 1 to 30% by weight, in particular 5 to 15% by weight of ethylene and optionally 0 to 25% by weight, in particular 3 to 20% by weight of further ethylenically unsaturated monomers, the data in % by weight relating to the total weight of the monomers.

[0071] As further ethylenically unsaturated monomers, preferably 0 to 20% by weight, in particular 3 to 15% by weight, of vinyl esters of unbranched or branched carboxylic acids having 3 to 18 C atoms and optionally 0 to 5% by weight, in particular 0.1 to 2% by weight, of ethylenically unsaturated acids, in particular ethylenically unsaturated sulfonic acids, or their salts are used, each based on the total weight of the monomers.

[0072] The multistage copolymers are preferably stabilized with an emulsifier and / or protective colloid. The multistage, radically initiated emulsion polymerization preferably takes place in the presence of one or more emulsifiers and / or one or more protective colloids.

[0073] Preferably, 15 to 30 wt.% protective colloids are used, based on the total amount of protective colloids and emulsifiers.

[0074] Preferably, 70 to 85 wt.% emulsifiers are used, based on the total amount of protective colloids and emulsifiers.

[0075] Preferably, 40 to 70 wt.% of non-ionic emulsifiers are used, based on the total amount of protective colloids and emulsifiers.

[0076] Preferably, 15 to 30 wt.% of anionic emulsifiers are used, based on the total amount of protective colloids and emulsifiers, in particular in steps a) to c), preferably in step a).

[0077] Examples of protective colloids are polyvinyl alcohols; polyvinyl acetals; polyvinylpyrrolidones; polysaccharides in water-soluble form such as starches (amylose and amylopectin), celluloses and their carboxymethyl, methyl, hydroxyethyl, hydroxypropyl derivatives, dextrins and cyclodextrins; proteins such as casein or caseinate, soy protein, gelatin; ligninsulfonates; synthetic polymers such as poly(meth)acrylic acid, copolymers of (meth)acrylates with carboxyl-functional comonomer units, poly(meth)acrylamide, polyvinylsulfonic acids and their water-soluble copolymers; melamine formaldehydesulfonates, naphthalene formaldehydesulfonates, styrene-maleic acid and vinyl ether-maleic acid copolymers.

[0078] Partially saponified or fully saponified polyvinyl alcohols with a degree of hydrolysis of preferably 80 to 100 mol% are preferred. Partially saponified polyvinyl alcohols with a degree of hydrolysis of 80 to 95 mol% are particularly preferred, in particular with a Höppler viscosity in 4% aqueous solution of 1 to 30 mPas (Höppler method at 20°C, DIN 53015). Most preferred are polyvinyl alcohols with a degree of hydrolysis of 85 to 94 mol%, in particular with a Höppler viscosity in 4% aqueous solution of 3 to 15 mPas (Höppler method at 20°C, DIN 53015). The protective colloids mentioned are accessible by methods known to those skilled in the art.

[0079] Protective colloids can be used in any of steps a) to c), but are preferably used in the first step a), especially in the initial stage. Protective colloids are particularly preferably used exclusively in the first step a).

[0080] Protective colloids are present in an amount of preferably 0.01 to 10 wt.%, particularly preferably 0.05 to 5 wt.% and most preferably 0.1 to 1.5 wt.%, based on the total weight of the monomers used in steps a) to c).

[0081] In the first stage a), preferably 0.5 to 15 wt.%, particularly preferably 0.5 to 10 wt.% and most preferably 0.5 to 5 wt.% of protective colloids are used, based on the total weight of the monomers of stage a).

[0082] Suitable emulsifiers are generally cationic emulsifiers, especially nonionic emulsifiers and / or anionic emulsifiers. The multi-stage, free-radically initiated emulsion polymerization preferably takes place in the presence of one or more nonionic emulsifiers and one or more anionic emulsifiers.

[0083] Examples of anionic emulsifiers are alkyl sulfates with a chain length of 8 to 18 carbon atoms, alkyl or alkylaryl ether sulfates with 8 to 18 carbon atoms in the hydrophobic moiety and up to 40 ethylene or propylene oxide units, alkyl or alkylaryl sulfonates with 8 to 18 carbon atoms, esters and half-esters of sulfosuccinic acid with monohydric alcohols or alkylphenols. Alkyl sulfonates and alkyl sulfates, especially lauryl sulfates, are particularly preferred.

[0084] Examples of non-ionic emulsifiers are those with alkylene oxide groups, in particular acyl, alkyl, oleyl or alkylaryl ethoxylates, such as alkyl polyglycol ethers or alkylaryl polyglycol ethers with 8 to 40 ethylene oxide units. Preferred are ethoxylated mono-, di- and trialkylphenols (preferably with an EO degree of 3 to 50 and an alkyl substituent radical of C 4 to C 12 ) and ethoxylated fatty alcohols (preferably with an EO degree of 3 to 80 and an alkyl radical of C 8 to C 36 ), in particular C 10 -C 14 fatty alcohol (3-40) ethoxylates, polyoxyethylene sorbitan monooleate with 20 ethylene oxide groups, copolymers of ethylene oxide and propylene oxide with a minimum ethylene oxide content of 10 percent by weight, the polyethylene oxide (4-40) ethers of oleyl alcohol and the polyethene oxide (4-40) ethers of nonylphenol. Particularly preferred are the polyethylene oxide (4-40) ethers of fatty alcohols, in particular oleyl alcohol, stearyl alcohol or C 11 alkyl alcohols.

[0085] Emulsifiers can be used in any of steps a) to c), but are preferably used in the first step a), especially in the initial stage. Emulsifiers are particularly preferably used exclusively in the first step a).

[0086] In the first stage a), preferably 0.4 to 15 wt.%, particularly preferably 0.8 to 10 wt.% and most preferably 1.5 to 5 wt.% of emulsifiers are used, based on the total weight of the monomers of stage a).

[0087] Emulsifiers are used in an amount of preferably 0.1 to 10 wt.%, particularly preferably 0.2 to 7 wt.% and most preferably 0.7 to 4 wt.%, based on the total weight of the monomers used in steps a) to c).

[0088] Non-ionic emulsifiers are used in an amount of preferably 0.05 to 10 wt.%, particularly preferably 0.1 to 5 wt.% and most preferably 0.5 to 3 wt.%, based on the total weight of the monomers used in steps a) to c).

[0089] Anionic emulsifiers are used in an amount of preferably 0.05 to 5 wt.%, particularly preferably 0.1 to 2 wt.% and most preferably 0.2 to 1 wt.%, based on the total weight of the monomers used in steps a) to c).

[0090] With the preferred provisions regarding protective colloids and emulsifiers, the object of the invention can be achieved even better.

[0091] The multi-stage copolymers are produced using the emulsion polymerization process.

[0092] The temperature for the emulsion polymerization is preferably 40°C to 120°C, particularly preferably 60°C to 95°C. The copolymerization of gaseous comonomers such as ethylene, 1,3-butadiene, or vinyl chloride can also be carried out under pressure, generally between 5 bar and 100 bar.

[0093] Suitable radical initiators are common oil-soluble or water-soluble initiators. Examples of oil-soluble initiators are oil-soluble peroxides, such as t-butyl peroxy-2-ethylhexanoate, t-butyl peroxypivalate, t-butyl peroxyneodecanoate, dibenzoyl peroxide, t-amyl peroxypivalate, di-(2-ethylhexyl)peroxydicarbonate, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, di-(4-t-butylcyclohexyl)peroxydicarbonate, dilauroyl peroxide, cumyl hydroperoxide, or oil-soluble azo initiators, such as azobisisobutyronitrile or dimethyl 2,2'-azobis(2-methylpropionate). Examples of water-soluble initiators are peroxodisulfates, such as potassium peroxodisulfate, hydrogen peroxide, water-soluble hydroperoxides such as tert-butyl hydroperoxide, manganese(III) salts, or cerium(IV) salts. The initiators are generally used in an amount of 0.005 to 3.0 wt. %, preferably 0.01 to 1.5 wt. %, based in each case on the total weight of the ethylenically unsaturated monomers. The use of redox initiators is preferred.Redox initiators used are combinations of the aforementioned initiators in combination with reducing agents. Suitable reducing agents include, for example, sodium sulfite, iron(II) salts, sodium hydroxymethanesulfinate, and ascorbic acid. Preferred redox initiators are cerium(IV) salts, such as ammonium cerium(IV) nitrate, manganese(III) salts, or peroxodisulfates, as well as combinations of these initiators. When using reducing agents, the amount of reducing agent is preferably 0.01 to 0.5 wt. %, based on the total weight of the ethylenically unsaturated monomers.

[0094] In the multi-stage emulsion polymerization of the present process, monomers from stage a) are generally used or polymerized first, followed by monomers from stage b), and finally by monomers from stage c). Each stage of the multi-stage polymerization is carried out by radical emulsion polymerization.

[0095] Step a) can be carried out by initially introducing all or some of the components of the reaction mixture, by partially introducing and subsequently metering in all or some of the components of the reaction mixture, or by the metering method without initial introduction. The monomers of step a) and the initiators in step a) are initially introduced in full or preferably in part, and any remaining amounts of ethylenically unsaturated monomers and initiators are metered in.

[0096] Following the first stage a), the monomers of the second stage b) are added, for example in the form of a solution or an emulsion or preferably in pure form.

[0097] The monomers of the second stage b) are generally added after complete addition of the monomers of the first stage a), in particular the monomers of the second stage b) are added immediately after complete addition of the monomers of the first stage a).

[0098] The first polymerization stage a) is carried out until preferably at least 70% by weight, particularly preferably at least 80% by weight, of the monomers used in stage a) have been polymerized (degree of conversion).

[0099] Preferably, the polymerization is not interrupted after addition of the monomers of the first stage a) and before addition of the monomers of the second stage b).

[0100] Alternatively, the polymerization can be interrupted before adding the monomers of the second stage b) and can be initiated again upon addition of monomers of stage b), for example by adding initiator.

[0101] Preferably, the initiator addition is not interrupted during the transition from the first stage a) to the second stage b). Initiator for the second stage b) can be added completely at the beginning of the second stage b), or partially added at the beginning of the second stage b) and the remainder added during the course of the second stage b), or preferably completely added during the second stage b).

[0102] The degree of conversion is preferably determined by means of 1< H NMR spectroscopy, in particular based on the polymerized vinyl acetate units and the residual vinyl acetate monomer content.

[0103] Following the second stage b), the monomers of the third stage c) are added, for example in the form of a solution or an emulsion or preferably in pure form.

[0104] The monomers of the third stage c) are generally added after complete addition of the monomers of the second stage b), in particular the monomers of the third stage c) are added immediately after complete addition of the monomers of the second stage b).

[0105] The second polymerization stage b) is carried out until preferably at least 85% by weight, particularly preferably at least 90% by weight, of the monomers used in stages a) and b) have been polymerized (degree of conversion).

[0106] Preferably, the polymerization is not interrupted after addition of the monomers of the second stage b) and before addition of the monomers of the third stage c).

[0107] Alternatively, the polymerization can be interrupted before adding the monomers of the third stage c) and can be initiated again upon addition of monomers of stage c), for example by adding initiator.

[0108] Preferably, the initiator addition is not interrupted during the transition from the second stage b) to the third stage c). Initiator for the third stage c) can be added completely at the beginning of the third stage c), or partially added at the beginning of the third stage c) and the remainder added during the third stage c), or preferably completely added during the third stage c).

[0109] Emulsifiers and / or protective colloids, which are also used for stabilization, can be fully introduced before initiating the first step a), or partially introduced and the remaining residue can be added, or completely added.

[0110] Emulsifiers and / or protective colloids can generally be introduced before and / or during the first stage a) and / or during the second stage b) and / or during the third stage c).

[0111] Preferably, emulsifiers and / or protective colloids are introduced completely before or during the first stage a). Particularly preferably, all amounts of emulsifiers and / or protective colloids are introduced completely before initiating the first stage a).

[0112] After the third step c), post-polymerization can be carried out using known methods to remove residual monomers. Volatile residual monomers and other volatile components can also be removed by distillation or stripping, preferably under reduced pressure.

[0113] The aqueous dispersions of the multistage copolymers have a solids content of preferably 30 to 75 wt.%, particularly preferably 45 to 60 wt.%.

[0114] The multistage copolymers have weight-average particle diameters Dw preferably between 200 and 3000 nm, more preferably between 300 and 2500 nm, particularly preferably between 400 and 2000 nm and most preferably between 500 and 1500 nm.

[0115] The determination of the parameters Dw and Dn or the particle size distribution is carried out by means of laser light diffraction and laser light scattering on the multi-stage copolymers using the measuring device LS13320 with the optical model PVAC.RF780D, including PIDS, from Beckmann-Coulter and in compliance with the instructions of the device manufacturer after sufficient dilution of the aqueous polymer dispersions with deionized water.

[0116] The multistage copolymers have a polydispersity PD of preferably ≤ 6, more preferably ≤ 5, even more preferably ≤ 4, particularly preferably ≤ 3.5, and most preferably ≤ 3.1. The polydispersity PD represents the ratio of weight-average particle diameter Dw to number-average particle diameter Dn, PD = Dw / Dn.

[0117] With the parameters Dw and PD of the multistage copolymers, the object of the invention can be achieved even better.

[0118] The Brookfield viscosity of the aqueous dispersions of the multistage copolymers is preferably 100 to 6000 mPas, more preferably 300 to 4000 mPas and most preferably 500 to 2000 mPas (determined with a Brookfield viscometer at 23°C at 20 rpm at a solids content of the dispersions of 55%).

[0119] The monomer selection or the selection of the weight fractions of the comonomers is carried out such that the multi-stage copolymers have a glass transition temperature Tg of -50°C to +120°C, preferably -35°C to +45°C. The glass transition temperature Tg of the polymers can be determined in a known manner using differential scanning calorimetry (DSC). The Tg can also be approximately calculated using the Fox equation. According to Fox TG, Bull. Am. Physics Soc. 1, 3, page 123 (1956), the following applies: 1 / Tg = x1 / Tg1 + x2 / Tg2 + ... + xn / Tgn, where xn is the mass fraction (wt. % / 100) of monomer n, and Tgn is the glass transition temperature in Kelvin of the homopolymer of monomer n. Tg values ​​for homopolymers are listed in Polymer Handbook 2nd Edition, J. Wiley & Sons, New York (1975).

[0120] The multi-stage copolymers are suitable, for example, as binders for coating materials, such as emulsion paints or plasters, particularly with high pH values ​​of, for example, 10 to 11.5, generally for indoor and outdoor use.

[0121] Preferably, the emulsion paints or plasters do not contain biocides.

[0122] Dispersion paints contain, for example, one or more pigments and / or one or more fillers, one or more multi-stage copolymers, optionally one or more other organic polymers of ethylenically unsaturated monomers other than the multi-stage copolymers, optionally water glass, optionally siliconates or silicates and optionally one or more additives and water.

[0123] Preferred formulations for emulsion paints contain 5 to 75% by weight of pigment and / or filler, in particular 1 to 35% by weight of pigments and / or 0 to 60% by weight of fillers, 1 to 25% by weight, in particular 5 to 15% by weight of multi-stage copolymers (solid / solid), preferably in the form of aqueous dispersions, optionally 0.1 to 25% by weight of other organic polymers of ethylenically unsaturated monomers (solid / solid), preferably in the form of aqueous dispersions, up to 5% by weight, in particular 0.1 to 3.5% by weight of water glass, up to 5% by weight, in particular 0.1 to 3.5% by weight of siliconates, in particular alkali metal alkyl siliconates, or silicates, in particular water-soluble alkali metal silicates, up to 10% by weight, in particular 0.1 to 5% by weight of additives and water, where the data in % by weight refer to the dry weight of the emulsion paints and Add up to 100% by weight.

[0124] The coating compositions can be produced conventionally using standard equipment. Common pigments, fillers, siliconates, silicates, or additives can be used. Examples of additives include dispersants, wetting agents, thickeners, stabilizers, defoamers, and hydrophobic agents. Further information on preferred components of the coating compositions or their preparation can be found, for example, in WO2017 / 144694.

[0125] Surprisingly, despite their significant vinyl acetate content, the multistage copolymers of the invention are very stable even in aqueous dispersions or aqueous compositions with high pH values. The pH of the dispersions remains constant even after prolonged storage, even at pH values ​​of 10 to 11.5. Advantageously, the multistage copolymers of the invention enable the production of preservative-free coating compositions. Furthermore, when used in paints, the multistage copolymers exhibit excellent pigment dispersion behavior and, after application of the paint, very good wet abrasion resistance and high hiding power.

[0126] By polymerizing vinyl esters of unbranched or branched carboxylic acids having 3 to 18 carbon atoms according to the invention, the pH stability can be further improved.

[0127] The following examples serve to further explain the invention without limiting it: Emulsifier 1: Block copolymer of ethylene oxide and propylene oxide 40 / 60, 20% in water (Genapol PF40); Emulsifier 2: Isotridecyl ethoxylate with 15 ethylene oxide units, 40% in water (Genapol X150); Emulsifier 3: secondary alkyl sulfonate, 30% in water (Mersolate); Protective colloid 4: partially saponified polyvinyl alcohol with a Höppler viscosity of 25 mPas and a saponification number of 140; TBHP: tertiary butyl hydroperoxide; Brüggolit FF6: Mixture of various low-valent sulfur compounds, Brüggemann. Example 1:

[0128] In a 5-liter pressure autoclave, 835 g of water, 54 g of a 20% aqueous solution of emulsifier 1, 94 g of a 40% aqueous solution of emulsifier 2, 54 g of a 30% aqueous solution of emulsifier 3, 209 g of a 10% aqueous solution of protective colloid 4, and 17 g of a 25% aqueous sodium vinylsulfonate solution were placed and thoroughly mixed. This mixture was adjusted to pH 4.0 with 2 g of 50% formic acid. 6.5 g of a 1% ferric ammonium sulfate solution and 214 g of vinyl acetate were then added to this mixture. The emulsion was stirred at 550 rpm and heated to 70°C, after which ethylene was injected at 27 bar, corresponding to a quantity of 130 g.

[0129] The polymerization was then initiated by adding TBHP (10%) at 4.1 g / h and Brüggolit FF6 (5%) at 13.4 g / h. 20 minutes after the start of the reaction, the following feed rates were initiated: 1500 g of vinyl acetate over 2.5 h, and a solution of 3.5 g of formic acid in 722 g of water over 3.0 h. The initiator feed rates were increased to 8.0 g / h of TBHP (10%) and 29 g / h of Brüggolit FF6 (5%). The ethylene pressure was increased to 35 bar until a total amount of 330 g of ethylene (including the above-mentioned 130 g of ethylene) had been introduced.

[0130] After the end of dosing of vinyl acetate, a dosing of 6.5 g vinyltriethoxysilane and 191 g vinyl acetate was started at 394 g / h for 30 min.

[0131] Subsequently, a dosing of 324 g of butyl acrylate and 324 g of methyl methacrylate was initiated and added at a rate of 865 g / h over 45 minutes. After dosing, the initiator rates were increased to 9.6 g / h of TBHP (10%) and 35.7 g / h of Brüggolit FF6 (5%), and polymerization was completed for 40 minutes.

[0132] The autoclave was then cooled, and the reaction mixture was freed of unreacted ethylene by depressurizing. To reduce free monomer, another 13 g of TBHP (10%) and 47.4 g of Brüggolit FF6 (5%) were added over 1 h. Finally, the dispersions were diluted with water to a maximum solids content of 54%, filtered through 250 µm, and bottled. Example 2:

[0133] The procedure was the same as Example 1 with the following changes: In the initial batch, 27 g of Versatic acid vinyl ester and 187 g of vinyl acetate were used instead of 214 g of vinyl acetate; instead of 1500 g of vinyl acetate, a mixture of 135 g of Versatic acid vinyl ester and 1365 g of vinyl acetate was added in 2.5 h. Example 3:

[0134] The procedure was the same as Example 1 with the following changes: In the initial batch, 27 g of Versatic acid vinyl ester and 186 g of vinyl acetate were used instead of 214 g of vinyl acetate; instead of 1500 g of vinyl acetate, a mixture of 269 g of Versatic acid vinyl ester and 1225 g of vinyl acetate was added in 2.5 h; the mixture of butyl acrylate and methyl methacrylate consisted of 322 g each instead of 324 g. Example 4:

[0135] The procedure was the same as Example 1 with the following changes: 203 g of vinyl acetate were used in the initial charge and the vinyl acetate dosage consisted of 1430 g of vinyl acetate; the mixture of vinyltriethoxysilane and vinyl acetate consisted of 6.5 g and 310 g, respectively; the mixture of butyl acrylate and methyl methacrylate consisted of 386 g each instead of 324 g. Example 5:

[0136] The procedure was the same as Example 1 with the following changes: 198 g of vinyl acetate were used in the initial charge and the vinyl acetate dosage consisted of 1390 g of vinyl acetate; the mixture of vinyltriethoxysilane and vinyl acetate consisted of 6.0 g and 302 g, respectively; the mixture of butyl acrylate and methyl methacrylate consisted of 450 g each instead of 324 g. Example 6:

[0137] The procedure was the same as Example 1 with the following changes: In the initial batch, 25 g of Versatic acid vinyl ester and 172 g of vinyl acetate were used instead of 214 g of vinyl acetate; instead of 1500 g of vinyl acetate, a mixture of 247 g of Versatic acid vinyl ester and 1128 g of vinyl acetate was metered in over 2.5 h; the mixture of vinyltriethoxysilane and vinyl acetate consisted of 6.0 g and 300 g, respectively; the mixture of butyl acrylate and methyl methacrylate consisted of 445 g each instead of 324 g.

[0138] Comparative Example 7: Commercially available aqueous dispersion of a polyvinyl alcohol and emulsifier-stabilized vinyl acetate-ethylene copolymer, without VeoVa and acrylate comonomer units.

[0139] Comparative Example 8: As Example 1, except that 32.4 g of methacrylic acid are added together with butyl acrylate and methyl methacrylate in the last step.

[0140] Comparative Example 9: commercially available aqueous styrene-acrylate copolymer dispersion.

[0141] Comparative Example 10: As Example 1, with the difference that steps a) and b) were combined into a single step: 1691 g of vinyl acetate and 6.5 g of vinyltriethoxysilane were simultaneously added to the initial charge containing the monomers vinyl acetate, ethylene and sodium vinylsulfonate, under an ethylene pressure as described for Example 1.

[0142] Subsequently, 324 g of butyl acrylate and 324 g of methyl methacrylate were polymerized as described in Example 1.

[0143] Comparative Example 11: As Example 1, with the difference that no vinyltriethoxysilane was used in step b) and 6.5 g of vinyltriethoxysilane were added together with butyl acrylate and methyl methacrylate in step c). Example 12:

[0144] As example 2, with the difference that in step c) an additional 6.5 g of vinyltriethoxysilane were added together with butyl acrylate and methyl methacrylate.

[0145] Comparative Example 13: As in Example 2, except that the 6.5 g of vinyltriethoxysilane, the 191 g of vinyl acetate, the 324 g of butyl acrylate, and the 324 g of methyl methacrylate were added simultaneously. Steps b) and c) of Example 2 were thus combined into a single step in Comparative Example 13. Table 1: Monomer composition of the (comparative) examples: Monomer a)< Example 1 Example 2 Example 3 Example 4 [g] [%] [g] [%] [g] [%] [g] [%] VAM 1905 67,33 1743 61, 60 1602 56, 84 1943 64, 95 E 270 9,54 270 9,54 270 9, 58 270 9,03 Veova10 0 0,00 162 5,73 296 10,50 0 0,00 Silane 6,5 0,23 6,5 0,23 6,5 0,23 6,5 0,22 BA 324 11,45 324 11,45 322 11,42 386 12,90 MMA 324 11,45 324 11,45 322 11,42 386 12,90 sum 2829,5 100 2829,5 100 2818,5 100 2991,5 100 a) VAM: vinyl acetate; E: ethylene; Veova10: vinyl versatic acid ester; silane: vinyltriethoxysilane; BA: butyl acrylate; MMA: methyl methacrylate; MAS: methacrylic acid. Continuation of Table 1: Monomer composition of the (comparative) examples: Monomer Example 5 Example 6 VBsp.7 VBsp. 8 [g] [%] [g] [%] [g] [%] [g] [%] VAM 1905 67,33 1600 52,67 2517 89, 9 1905 66,57 E 270 9,54 270 8,89 274 9, 8 270 9,44 Veova10 0 0,00 272 8,95 0 0 0 0,00 Silane 6,5 0,23 6 0,20 8 0,3 6,5 0,23 BA 324 11, 45 445 14,65 0 0 324 11,32 MMA 324 11, 45 445 14, 65 0 0 324 11,32 MAS 0 0 0 0 0 0 32,4 1,13 sum 3066 100 3038 100 2800 100 2861,5 100 Continuation of Table 1: Monomer composition of the (comparative) examples: Monomer VBsp. 10 VBsp. 11 Example 12 VBsp.13 [g] [%] [g] [%] [g] [%] [g] [%] VAM 1890 61, 64 1905 67,33 1743 61,5 1743 61, 60 E 270 8,81 270 9,54 270 9,52 270 9,54 Veova10 0 0,00 0 0,00 162 5,71 162 5,73 Silane 6 0,20 6,5 0,23 13 0,46 6,5 0,23 BA 450 14, 68 324 11,45 324 11,4 324 11,45 MMA 450 14, 68 324 11,45 324 11,4 324 11,45 MAS 0 0 sum 2829, 5 100 2829,5 100 2829, 5 100 2829, 5 100

[0146] The information on the monomer compositions in Table 1 takes into account that 20 wt.% of the ethylene used was not polymerized but discarded as residual gas. Table 2: Analytical data on the polymer dispersions of the (comparative) examples: Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 VBsp. 7 VBsp. 8 FG* 54,0 52,3 53,6 54,0 54,0 53,9 55,5 58,2 pH* 4,2 5,2 5,1 4,8 5,7 4,8 4,2 4,55 Viscosity* 290 256 770 820 310 596 1475 2080 Tg* 1 -0,5 -0,2 2,9 2,8 -0,2 6,5 6 Dw* 983 1240 845 984 1214 1489 604 745 Dn* 452 398 433 497 576 491 380 412 Dw / Dn* 2,4 3,1 1,95 1,98 2,1 3,03 1,59 1,81 *: FG: solids content [%]; pH: pH value; viscosity: [mPas]; Tg: glass transition temperature [°C]; Dw: weight-average particle diameter [nm]; Dn: number-average particle diameter [nm]; Dw / Dn: polydispersity PD. Continuation of Table 2: analytical data on the polymer dispersions of the (comparative) examples: VBsp.10 VBsp.11 Example 12 VBsp.13 FG* 54,7 52,2 52,3 52,3 pH* 4,5 5,0 4,8 4,8 Viscosity* 852 996 652 1290 Tg* 2,4 -0,7 -0, 9 0,4 Dw* 1863 1451 1252 2014 Dn* 431 459 423 432 Dw / Dn* 4,32 3,16 2,96 4,66 Production of an emulsion paint:

[0147] A color matrix was prepared by conventional mixing of the formula given below. The pH of the color matrix was 11.9. Color matrix recipe:

[0148] 301,5 g Water, 7,6 g dispersants, 4,4 g Defoamers, 4,3 g thickener, 385,8 g Filler (CaCO 3 ), 129,3 g titanium dioxide, 2,0 g pH adjuster, 15,0 g alkaline component.

[0149] Mixing the paint matrix with the polymer dispersion of the respective (comparative) example according to the specifications in Table 3 resulted in matte, ready-to-use interior emulsion paints. The solids content of the polymer dispersion of the respective (comparative) example was previously adjusted to 50%. Table 3: Composition of emulsion paints: Binder content of the emulsion paint 7% polymer dispersion 14% polymer dispersion Color matrix [g] 279 258 Polymer dispersion (50%) [g] 21 42 Dispersion paint [g] 300 300 Testing the storage stability of emulsion paints:

[0150] After mixing the color matrix with the polymer dispersion, the pH value of the respective dispersion paint was determined ("pH Start").

[0151] The emulsion paints were then stored in a drying cabinet at a temperature of 50°C. After a storage period of 14 days, the paints were removed from the drying cabinet, cooled to room temperature, and the pH value was determined ("pH 14d / 50°C").

[0152] The decisive factor for assessing pH stability is the difference ("Delta pH") between the pH value after production ("pH Start") and storage of the emulsion paint ("pH 14d / 50°C").

[0153] The results of the testing are summarized in Table 4 below. Table 4: pH stability of the emulsion paints: Polymer dispersion Dispersion paint 7 wt.% polymer dispersion 14 wt.% polymer dispersion pH pH Start* 14d / 50°C* Delta* Start* 14d / 50°C* Delta* Example 1 11,47 10,62 0,85 11,31 10,21 1,10 Example 2 11,42 10,96 0,46 11,21 10,60 0,61 Example 3 11,41 10,99 0,42 11,32 10,63 0,69 Example 4 11,42 11,05 0,37 11,29 10,52 0,77 Example 5 11,40 10,98 0,42 11,30 10,70 0,60 Example 6 11,30 11,05 0,25 11,18 10, 65 0,53 VBsp.7 11,30 9,90 1,40 11,20 9,40 1,80 VBsp.8 11,41 11,01 0,40 11,31 10,68 0,63 VBsp.9 11,40 10,84 0,56 11,21 10,64 0,57 *: Start: pH value of the emulsion paint after production; 14d / 50°C: pH value of the emulsion paint after storage for 14 days at 50°C; Delta: difference between the pH values ​​of "Start" and "14d / 50°C".

[0154] The emulsion paints containing polymer dispersions according to the invention all exhibited pH values ​​above 10 after storage. This is the prerequisite for the production of preservative-free emulsion paints, since under these conditions the growth of microorganisms in the paint is strongly suppressed.

[0155] In contrast, in the case of the non-inventive emulsion paint containing the VAE polymer dispersion of Comparative Example 7, the pH had already fallen below a pH of 10 after 2 weeks of storage.

[0156] Surprisingly, the pH stability of the emulsion paints according to the invention, despite their vinyl acetate content, is comparable to or even better than in the case of the emulsion paint with the acrylate polymer dispersion of Comparative Example 9 as binder.

[0157] This means that the desired pH stability of vinyl acetate copolymers is achieved by the multi-stage polymerization according to the invention. Testing the opacity of the emulsion paints:

[0158] The opacity was determined using the method described in the "Guideline for the Determination of Hiding Power" of the Association of the German Paint Industry, July 2002 edition, in accordance with DIN EN 13300.

[0159] The respective emulsion paints were applied using an automatic film applicator with a squeegee with a gap height of 150 µm and 225 µm, each on black-and-white contrast cards (Type 3H from Leneta) with a standard color value Y over black of 7 or less and a standard color value Y over white of 80 to 90. The coated contrast cards were dried for 24 hours at 23°C and 50% relative humidity and then weighed.

[0160] The coverage in m 2 / l was calculated from the application quantity in g / m 2< and the color density.

[0161] Using a colorimeter (Elrepho 450X from Datacolor), the standard color values ​​Y (color standards) were measured over the black and white base and the "contrast ratio" was calculated in percent.

[0162] The contrast ratio values ​​thus determined were plotted against the corresponding yield (m 2 / l). The contrast ratio was determined at 6, 7, and 8 m 2 / l by interpolation.

[0163] The covering power of the paints was tested using a 14% binder.

[0164] The results of the testing are summarized in Table 5. Table 5: Coverage of emulsion paints: 6 m 2 < / L 7 m 2 < / L 8 m 2 < / L Example 1 99,2 98,9 98,6 Example 2 99,1 98,8 98,4 Example 3 99,1 98,7 98,3 Example 4 99,2 98,8 98,4 Example 5 99,1 98,8 98,4 Example 6 99,2 98,9 98,6 VBsp.7 99,0 98,6 98,2 VBsp.8 99,2 98,8 98,4 VBsp.9 98,6 98,0 97,4

[0165] The pigment binding capacity or hiding power of emulsion paints with vinyl acetate copolymers as binders is known to be greater than that of corresponding emulsion paints with acrylate copolymers as binders, as discussed above and demonstrated with Comparative Example 7 (vinyl acetate copolymer) and Comparative Example 9 (acrylate copolymer). Surprisingly, the emulsion paints with copolymers according to the invention, despite their acrylate content, exhibit better hiding power than the emulsion paint of Comparative Example 7, which contained a vinyl acetate copolymer without acrylate content as binder.

[0166] This means that the multi-stage polymerization according to the invention increases the hiding power of binders containing acrylate units.

[0167] In addition to the improved hiding power, the dispersion paints according to the invention also show the required stability at high pH values ​​despite their vinyl acetate content and thus make biocide-free dispersion paints possible.

[0168] The binders according to the invention show a comparable stability of the pH value in the paint during storage as the commercially available styrene-acrylate dispersions and at the same time improved properties with regard to hiding power, which allows a more efficient use of white or color pigments. Testing the abrasion resistance SF (wet abrasion resistance) of the emulsion paints:

[0169] Wet abrasion resistance was determined using the nonwoven method according to ISO 11998. For this purpose, the respective emulsion paint was applied to a Leneta film (PVC film) with an applicator in a layer thickness of 300 µm (wet). The emulsion paints described above, each containing 14 wt.% polymer dispersion, were used.

[0170] The samples were then stored for 72 hours at standard climate (DIN 50014, 23°C and 50% relative humidity), then for 24 hours at 50°C and finally for 24 hours at standard climate.

[0171] The result was a dry film thickness of 200 µm.

[0172] Then three test strips measuring 2.5 cm x 7.5 cm were cut out and then weighed.

[0173] The test strips were subjected to a 200-cycle abrasion test with a scouring pad (3M Scotch-Brite®, Hand Pad 7448, gray, Type S UFN) and then reweighed. The paint removal in µm was then calculated from the paint density of the scrubbed area and the mass loss of the paint film.

[0174] Lower paint removal means higher wet abrasion resistance.

[0175] An average of three measurements was determined. The test results are summarized in Table 6 below.

[0176] Table 6 shows that the emulsion paints containing the polymer dispersions of Example 1 and Example 2 as binders exhibited considerably higher wet abrasion resistance than the corresponding emulsion paints containing the polymer dispersions of Comparative Example 8 (additionally copolymerized with acid in stage c)), Comparative Example 10 (polymerization stages a) and b) combined into one stage), Comparative Example 11 (silane in stage c), but not polymerized in stage b), or Comparative Example 13 (polymerization stages b) and c) combined into one stage). A particularly high wet abrasion resistance was obtained with the polymer dispersion of Example 12 (silane in stage b) and also polymerized in stage c). Table 6: Wet abrasion resistance of the emulsion paints with the polymer dispersions of (comparative) examples 1, 8 and 10 as binders: Polymer dispersion Wet abrasion [µm] Example 1 32 Comparative example 8 48 Comparison example 10 36 Comparative example 11 34 Example 2 31 Example 12 20 Comparison example 13 37

Claims

1. A process for preparing multistage copolymers in the form of aqueous dispersions by multistage, radically initiated emulsion polymerization, characterized in that a) in a first stage, 20% to 75% by weight of vinyl acetate, optionally ethylene and optionally one or more further ethylenically unsaturated monomers are polymerized, b) in a second stage, in the presence of the polymer from the first stage a), 1% to 25% by weight of vinyl acetate, 0.01% to 2% by weight of one or more ethylenically unsaturated silicon-functional monomers and optionally one or more further ethylenically unsaturated monomers are polymerized, and c) in a third stage, in the presence of the polymer from the second stage b), 5% to 40% by weight of one or more monomers selected from the group encompassing esters of acrylic acid, esters of methacrylic acid and vinyl aromatics and optionally one or more further ethylenically unsaturated monomers are polymerized, with the proviso that in the third stage c), no ethylenically unsaturated carboxylic acid is polymerized, where the figures in % by weight are based on the total weight of the monomers used overall in stages a) to c).

2. The process for preparing multistage copolymers in the form of aqueous dispersions as claimed in claim 1, characterized in that in the first stage a), ≥ 40% by weight of vinyl acetate are polymerized, based on the total weight of the monomers of stage a).

3. The process for preparing multistage copolymers in the form of aqueous dispersions as claimed in claim 1 or 2, characterized in that in the first stage a), 1% to 40% by weight of ethylene are polymerized, based on the total weight of the monomers used overall in stages a) to c).

4. The process for preparing multistage copolymers in the form of aqueous dispersions as claimed in claim 1 to 3, characterized in that in the first stage a), 1% to 30% by weight of ethylene are polymerized, based on the total weight of the monomers of stage a).

5. The process for preparing multistage copolymers in the form of aqueous dispersions as claimed in claim 1 to 4, characterized in that in the first stage a), 0.1% to 25% by weight of vinyl esters of unbranched or branched carboxylic acids having 3 to 18 carbon atoms are polymerized, based on the total weight of the monomers used overall in stages a) to c).

6. The process for preparing multistage copolymers in the form of aqueous dispersions as claimed in claim 1 to 5, characterized in that in the first stage a), 0.01% to 2% by weight of ethylenically unsaturated acids are polymerized, based on the total weight of the monomers used overall in stages a) to c).

7. The process for preparing multistage copolymers in the form of aqueous dispersions as claimed in claim 1 to 6, characterized in that in the first stage a), no esters of acrylic acid, no esters of methacrylic acid and no vinyl aromatics are copolymerized.

8. The process for preparing multistage copolymers in the form of aqueous dispersions as claimed in claim 1 to 7, characterized in that in the second stage b), 40% to 99.9% by weight of vinyl acetate are polymerized, based on the total weight of the monomers of stage b).

9. The process for preparing multistage copolymers in the form of aqueous dispersions as claimed in claim 1 to 8, characterized in that one or more ethylenically unsaturated silicon-functional monomers of the second stage b) are silicon compounds of the general formula R1SiR20-2(OR3)1-3, where R1 has the meaning CH2=CR4-(CH2)0-1 or CH2=CR4CO2(CH2)1-3, R2 has the meaning C1 to C3 alkyl radical, C1 to C3 alkoxy radical or halogen, R3 is an unbranched or branched, optionally substituted alkyl radical having 1 to 12 carbon atoms or an acyl radical having 2 to 12 carbon atoms, where R3 may optionally be interrupted by an ether group, and R4 is H or CH3; and / or one or more ethylenically unsaturated silicon-functional monomers of the second stage b) are (meth)acrylamides of the general formula CH2=CR5-CO-NR6-R7-SiR8n-(R9)3-m, where n = 0 to 4, m = 0 to 2, R5 is either H or a methyl group, R6 is H or an alkyl group having 1 to 5 carbon atoms, R7 is an alkylene group having 1 to 5 carbon atoms or is a divalent organic group in which the carbon chain is interrupted by an O or N atom, R8 is an alkyl group having 1 to 5 carbon atoms, and R9 is an alkoxy group having 1 to 40 carbon atoms which may be substituted by further heterocycles.

10. The process for preparing multistage copolymers in the form of aqueous dispersions as claimed in claim 1 to 9, characterized in that in the second stage b), 0.1% to 20% by weight of ethylenically unsaturated silicon-functional monomers are polymerized, based on the total weight of the monomers of stage b).

11. The process for preparing multistage copolymers in the form of aqueous dispersions as claimed in claim 1 to 10, characterized in that in the second stage b), no ethylenically unsaturated acids, no esters of acrylic acid, no esters of methacrylic acid and no vinyl aromatics are copolymerized.

12. The process for preparing multistage copolymers in the form of aqueous dispersions as claimed in claim 1 to 11, characterized in that in the third stage c), 70% to 100% by weight of one or more monomers selected from the group encompassing esters of (meth)acrylic acid and vinyl aromatics are polymerized, based on the total weight of the monomers of stage c).

13. The process for preparing multistage copolymers in the form of aqueous dispersions as claimed in claim 1 to 12, characterized in that in the third stage c), 0.01% to 2% by weight of ethylenically unsaturated silicon-functional monomers are polymerized, based on the total weight of the monomers used overall in stages a) to c).

14. A multistage copolymer in the form of an aqueous dispersion obtainable by the multistage, radically initiated emulsion polymerization process of claim 1 to 13.

15. The multistage copolymer in the form of an aqueous dispersion as claimed in claim 14, characterized in that the multistage copolymer is stabilized by one or more protective colloids, one or more nonionic emulsifiers and one or more anionic emulsifiers.

16. The multistage copolymer in the form of an aqueous dispersion as claimed in claim 14 or 15, characterized in that the multistage copolymer has a weight-average particle diameter Dw of between 200 and 3000 nm.

17. The multistage copolymer in the form of an aqueous dispersion as claimed in claim 14 to 16, characterized in that the multistage copolymer has a polydispersity PD of ≤ 3.5.

18. The use of the multistage copolymer in the form of an aqueous dispersion from claim 14 to 17 as a binder for coating materials, such as emulsion paints or renders.

19. The use of the multistage copolymer in the form of an aqueous dispersion from claim 14 to 17 as a binder for emulsion paints or renders with pH levels of 10 to 11.5.