WO2004020477A1 - Aqueous polymer dispersions, method for the production thereof and use thereof, especially in anti-corrosion coatings - Google Patents

Abstract

The invention relates to polymer dispersions which are used to protect against corrosion and which have good anti-rust properties, and to the production and use thereof. The polymer dispersions comprise emulsifiers containing phosphate and/or phosphate groups and are (partially) neutralized prior to polymerization by adding bases. As a result, mass produced polymer dispersions having improved anti-rust properties according to condensed water test DIN 50017 and a low coagulate content can be obtained. The polymer dispersions result in improved stability of the anti-corrosion primer produced therewith. High gloss coatings can be obtained using said polymer dispersions.

Description

description

Aqueous polymer dispersions, processes for their preparation and their use, in particular in corrosion protection coatings

The present invention relates to new aqueous copolymer dispersions, processes for their preparation and their use, in particular in corrosion protection coatings.

Aqueous polymer dispersions for use in anti-corrosion coatings are subject to a number of boundary conditions which must be observed in order to ensure adequate protection against rust formation. For example, the coating must have sufficient hydrophobicity to prevent the diffusion of water to the interface between the substrate and the coating, since water is significantly involved in the corrosion process. Furthermore, good adhesion between the substrate and the coating should be ensured in order to minimize the formation of bubbles at the substrate / coating interface due to the infiltration of the anticorrosive protective layer by water. Finally, the corrosion protection layer should have a good diffusion barrier effect against carbon dioxide. Unsaturated ß-ketoester compounds, such as allylacetoacetate and acetoacetoxyethyl methacrylate, have proven themselves in the literature as adhesion-increasing comonomers.

The task of ensuring good adhesion between the substrate and the coating is achieved in WO 99/14278 by acetoacetoxy groups in the polymer. Poly (alkyleneimines) are added to the polymer dispersions, which crosslink with the acetoacetoxy groups during film formation with enamine formation. The premature crosslinking reaction in the polymer dispersion was suppressed by the addition of anionic emulsifiers. In the same way, the stabilization of the crosslinking system with nonionic emulsifiers, such as Example in WO 99/14275 and WO 99/14279. In the latter document, nonionic emulsifiers are subsequently added as stabilizers. Phosphate emulsifiers are used for the polymerization. The dispersions obtained have little tendency to foam.

A disadvantage of these coatings is the need to post-stabilize the dispersions obtained by adding emulsifiers. According to the examples disclosed, larger amounts of the emulsifiers are to be added in order to achieve the required storage stability. The addition of poly (alkyleneimine) emulsifier is therefore on the one hand expensive, on the other hand the water absorption increases with an increased emulsifier content in a coating, which is detrimental to the corrosion protection effect. There is also the danger that the emulsifiers migrate to the substrate / coating interface and there can reduce the adhesion to the substrate. In combination with increased water absorption, this leads to blistering in the coatings ("blistering").

Finally, amines tend to form brown-colored degradation products in aqueous solutions, which are undesirable per se and can also apparently lead to discoloration of the coating. The packaging of the dispersions with the described additives and the necessary final pH reduction with a buffer system further increase the costs for the manufacture of the product.

The crosslinking mechanism of polyamines with acetoacetoxy groups based on aqueous polymer dispersions is i.a. also described in WO 98/54256.

US Pat. No. 5,122,566 discloses a process for the preparation of latices which is carried out by means of aqueous emulsion polymerization in the presence of phosphate emulsifiers and at a pH <3.5. The dispersions described in this document also contain at least one water-insoluble, nonionic surface-active agent and are adjusted to a pH in the range from 7 to 10.5 after the polymerization. The use of adhesion-increasing acetoacetoxy derivatives of (meth) acrylic acid is not disclosed.

EP-A-0 476 528 discloses a process for the (industrial) production of latices, in which copolymers of vinyl aromatics are used by means of aqueous emulsion polymerization in the presence of a seed polymer at pH <3.5 in the presence of phosphate emulsifiers and a water-insoluble, nonionic surface-active agent and acrylates. Except for the presence of at least one seed polymer, this method is identical to that disclosed in US Pat. No. 5,122,566. According to EP-A-0 476 528, polymers with a very high coagulum content are obtained on an industrial production scale in the absence of at least one seed polymer, ie the process according to US Pat. No. 5,122,566.

The present invention was therefore based on the object of providing aqueous polymer dispersions which, in corrosion protection coatings, have a high resistance to corrosion in the condensation water test in accordance with DIN 50017, are accessible on an industrial scale and can be prepared without the complex synthetic methods described in the prior art.

Furthermore, the films of the polymers should be distinguished by high transparency, that is to say the absence of disruptive scattering centers due to the formation of aggregates during the polymerization, so that they can also be used in clearcoats.

The object is achieved according to the invention by an aqueous polymer dispersion having a solids content of 20 to 74% by weight, preferably 40 to 70% by weight, containing at least one copolymer A) which

a) 40 to 99.95% by weight, preferably 60 to 90% by weight, based on the weight of the monomers used to prepare the copolymer, of at least one mono- or oligoethylenically unsaturated monomer which can be polymerized by free radical emulsion polymerization , b) 0.05 to 10% by weight, preferably 0.05 to 5% by weight, based on the weight of the monomers used to prepare the copolymer, at least one ethylenically unsaturated mono- and / or oligocarboxylic acid, or their salts, and c) 0 to 5% by weight, preferably 0.05 to 2% by weight, based on the weight of the monomers used to prepare the copolymer, at least one other ethylenically unsaturated mono- and / or oligo acid derived from phosphoric acid, phosphonic acid, sulfuric acid and / or sulfonic acid or their salts,

contains copolymerized,

which is characterized in that it contains at least 0.3% by weight, preferably 0.3 to 5% by weight, based on the weight of the monomers used to prepare the copolymer, of emulsifiers containing phosphate and / or phosphone groups and that which the at least one monomer b) and, if present, the at least one monomer emulsion template containing the at least one monomer c) has a pH> 4.7.

The copolymer A) used according to the invention usually has a copolymer at least one glass transition temperature T _g in the range from -35 to 80 ° C., preferably one T _g in the range from 0 to 40 ° C. or two T _g ^'s in the range from -30 to +20 ° C (first T _fl ) and from +40 to + 80 ° C (second T _g ).

The glass transition temperature of the copolymer A) used according to the invention is set by selecting the type and amount of the comonomers.

The proportions by weight of the monomers a) to c) are preferably chosen so that a copolymer composed only of them would have a glass transition temperature T _g in the range from -35 to 80.degree.

It was surprisingly found that the aqueous dispersions according to the invention have a significantly improved resistance of the resulting corrosion protection coatings in the condensation test according to DIN 50017. Furthermore, the aqueous dispersions according to the invention have reduced coagulum formation during the polymerization. The dispersions obtained can be produced perfectly on an industrial scale and the corrosion protection primer coatings formulated with them have increased (storage) stability. Finally, coatings with a high gloss can be produced with the dispersions according to the invention.

Preferred building blocks a) of the at least one copolymer are the esters σ, β-ethylenically unsaturated carboxylic acids with alkanols containing 1 to 18 carbon atoms, preferably the esters of acrylic and methacrylic acid with methanol, ethanol, propanols, butanols, pentanols, 2- Ethyl hexanol, iso-octanol, n-decanol and n-dodecanol. Furthermore, vinyl aromatic monomers such as styrene and its alkyl derivatives such as methyl styrene, ethyl styrene and oligo (alkyl) styrenes are preferred monomers. It is also possible to use alkenes, such as ethene, propene, isobutene and derivatives of these compounds, such as vinyl chloride, vinyl ether and esters of (aliphatic) carboxylic acids with alkenes, preferably vinyl acetate, or ethylenically unsaturated esters of versatic acid as building blocks a).

Mono- or oligoethylenically unsaturated mono- or oligocarboxylic acids and their anhydrides or their salts are used as building blocks b). Acrylic acid, methacrylic acid, itaconic acid, maleic acid and / or fumaric acid and their salts are preferably used. If the pH of the aqueous monomer emulsion template containing the building blocks b) and c) is <4.7, it must be raised to at least pH> 4.7. This is done by submitting building blocks b) and (if used) c) in water, optionally together with building blocks d) and emulsifiers and optionally initiators, in the aqueous monomer emulsion template and the monomer emulsion template by adjusting the pH to bases with pH> 4 , 7 is neutralized before the rest of the monomers are added. Partially water-soluble building blocks d), such as, for example, AAEMA, can be added to the aqueous initial charge of the monomer emulsion.

In this document, the mixture of the following is used as the monomer emulsion template Substances in the storage vessel for the production of monomer emulsions: water, building blocks b), building blocks c) (if present), emulsifiers and optionally building blocks d) and optionally initiators.

Sodium and potassium hydroxide are preferably used to raise the pH of the monomer emulsion template. Ammonia is particularly preferably used for the neutralization of the monomer emulsion charge, since the base volatilizes after the film formation of the polymer, which results in less water absorption by the polymer.

Preferred building blocks c) are ethylenically unsaturated derivatives of sulfuric, sulfonic, phosphoric and / or phosphonic acid in the form of their sodium, potassium and ammonium salts. Particularly preferred are sodium ethenesulfonate, 2-acrylamido-2-methylpropanesulfonic acid (AMPS ^®) salts and Kaliumsulfopropyl methacrylate. The ammonium salts are particularly preferably used since after

Film consolidation the free acids are present in the polymer, which have a lower water absorption of the polymer than the corresponding salts.

When specifying the proportions by weight of the individual (comonomer) components in at least one copolymer, it is assumed that all the comonomers used are incorporated 100% into the copolymer.

The aqueous polymer dispersions according to the invention further contain at least 0.3% by weight, preferably 0.3 to 5% by weight, based on the weight of the monomers used to prepare the copolymer, of emulsifiers containing phosphate and / or phosphone groups. The emulsifiers are preferably used as ammonium, sodium and potassium salts of the phosphoric acid esters and / or the phosphonic acid esters. However, the salts of these compounds with other bases can also be used. If the free phosphoric acid and / or phosphonic acid esters are used as raw material, they can be neutralized to pH> 7 (in part) in situ by reacting an aqueous solution of the emulsifier with a base, preferably with ammonia. Emulsifiers containing phosphate groups are preferred, in particular esters of phosphoric acid with alcohols and phenols (also as mixtures of mono-, di- and triesters of phosphoric acid), esters of phosphoric acid with adducts of alcohols or (alkyl) phenols and ethylene oxide and / or propylene oxide and the sodium -, Potassium and ammonium salts of these compounds used. The compounds are commercially available, for example, under the trade name ^® Berol 522 (alkylphosphoric acid potassium salt), ^® Hostaphat1306 (alkyloligoethoxylate phosphoric acid ester and ^® Berol 733 (alkylphenololigoethoxylate phosphate potassium salt). As phosphate group-containing emulsifiers, ethylenically unsaturated esters of phosphoric acid and hydrocarbons derived therefrom with hydrocarbons can also be used Neutralization products with bases can be used.

In a preferred embodiment, the at least one copolymer of the aqueous dispersion additionally contains 0.05 to 10% by weight, particularly preferably 0.5 to 3% by weight, based on the weight of the monomers used to prepare the copolymer, of a free-radically polymerizable one Monomers d) with at least one acetoacetoxy group in copolymerized form.

Acetoacetoxyethyl methacrylate (AAEMA) and acetoacetoxyethyl acrylate (AAEA) are preferably used as preferred monomers d). Also

Acetoacetic acid vinyl ether can be used. According to the invention, the monomers d) can also be introduced with the monomers b) and c) in the initial charge of the monomer emulsion if they, e.g. AAEMA, are partially water-soluble.

In addition, the at least one copolymer of the aqueous dispersion can additionally, based in each case on the weight of the monomers used to prepare the copolymer, from 0 to 10% by weight, preferably 0 to 2% by weight and particularly preferably 0.05 to 1 Wt .-%, at least one (mono) - or (oligo) - ethylenically unsaturated reactive crosslinking monomers e) copolymerized, in addition to it 0 to 30 wt .-%, preferably 0 to 5 wt .-%, other copolymerizable (mono ) - or (oligo) ethylenically unsaturated monomers f) copolymerized and additionally 0 to 5% by weight, preferably 0 to 2 % By weight, particularly preferably 0 to 0.5% by weight, of molecules g) which react with the polymer by polymer-analogous reactions.

As reactive crosslinking monomers e), i.e. Monomers that crosslink during film formation are preferably ethylenically unsaturated derivatives of silane, such as, for example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, (methacrylicoxypropyltrimethoxysilane, vinyltris (2-methoxyethoxy) silane and (methacryoxoxy-2-oxypropyl-methoxysiloxysilane ) silane, used.

Also suitable as monomers e) are glycidyl (meth) acrylates and / or other ethylenically unsaturated derivatives of glycidol, such as, for example, glycidyl vinyl ether.

Diacetone acrylamide can also be used as monomer e). In this case, however, a dihydrazide should be added as a co-crosslinker. Masked derivatives of N-methylolacrylamide, such as N-butoxymethylmethacrylamide, can also be used as crosslinking agents.

Other monomers f) which can be used include, for example, unsaturated nitrogen-containing monomers, such as methacrylamide and dimethylaminoethyl (meth) acrylate, derivatives of urea, such as ß-ureidoethyl acrylate, ß-ureidovinyl ether, and φ-hydroxyalkyl (meth) acrylates, where Methacrylamide is preferred.

Also bifunctional (meth) acrylates, such as 1, 4- and 1, 3-butanediol di (meth) acrylate and 1, 6-hexanediol di (meth) acrylate, bifunctional ethylene derivatives, such as divinylbenzene, butadiene and trifunctional (meth) acrylates, such as trimethylolpropane trimethacrylate, can be used as other unsaturated monomers f) to increase the elasticity of the coating.

In general, substances g) which react with functional groups of the polymer by polymer-analogous reactions can be used as building blocks g). Epoxysilanes are preferably used here, particularly preferably glycidyloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, β- (3,4- Epoxycyclohexyl) ethyltrimethoxysilane, furthermore oligofunctional silanes such as 1 - (triethoxysilyl) -2- (diethoxymethylsilyl) ethane or tris- [3- (trimethoxysilyl) propyljisocyanurate.

In a further embodiment, the aqueous composition according to the invention contains

Polymer dispersion 0 to 5 wt .-%, preferably 0 to 0.5 and particularly preferably 0 to 0.3 wt .-%, based on the weight of the monomers used to prepare the copolymer, of UV-crosslinking substances which are not ethylenically unsaturated are. Preferred UV crosslinkers are acetophenone, benzophenone and acetophenone or benzophenone derivatives which do not contain an ethylenically unsaturated polymerizable group. Derivatives of benzophenone which are present as a liquid mixture at room temperature, optionally with the addition of suitable auxiliary substances, are particularly preferred since these are advantageous in terms of application technology. Phosphine oxide derivatives can also be used.

In addition to the emulsifiers containing phosphate and / or phosphone groups, the aqueous polymer dispersion according to the invention can also contain further emulsifiers. The total amount of emulsifiers is preferably in the range from 0.3 to 10% by weight, particularly preferably 0.3 to 3.5% by weight, based on the total amount of the monomers of the copolymer. Preferred further emulsifiers are those which contain alkyl, aryl or alkylaryl groups. A poly (ethylene oxide), a poly (propylene oxide) or a poly (ethylene oxide / propylene oxide) can be used as a spacer between the hydrocarbon radical and the polar head group. The use of further ionic emulsifiers based on sulfate, sulfonate or carboxylate in addition to the phosphate or phosphonate emulsifiers is less preferred. Nonionic co-emulsifiers in addition to the phosphate and / or phosphone emulsifiers can also be used. The emulsifiers are preferably added before and / or during the polymerization. However, ionic and nonionic emulsifiers can also be added to the finished dispersion in order to increase their stability. The amount of emulsifiers used should be kept as low as possible in order to minimize the water absorption of the coatings. In a further embodiment, the aqueous polymer dispersion according to the invention contains 0 to 5% by weight, preferably 0 to 1% by weight, based on the weight of the monomers used to prepare the copolymer, of protective colloids. All protective colloids known to the person skilled in the art and suitable for the present purpose can be used as protective colloids. However, water-soluble carboxymethyl celluloses are preferably used, particularly preferably in the form of their ammonium or alkali salts. Commercially available products are, for example, ^® Blanose 7M, ^® Blanose 7UL, ^® Blanose 7EL and ^® Ambergum 3021 (Aqualon). Furthermore, the carboxymethyl celluloses can optionally carry further substituents, such as, for example, alkyl or hydroxyalkyl radicals, alkyloxyalkyl radicals and dialkylamino groups. Examples include methylcarboxymethyl cellulose, ethyl carboxymethyl cellulose, hydroxyethyl carboxymethyl cellulose, hydroxypropyl carboxymethyl cellulose, methoxyethyl carboxymethyl cellulose and ethoxyethyl carboxymethyl cellulose.

Furthermore, high-molecular compounds such as, for example, polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylamides, polymethacrylamides or polycarboxylic acids and their alkali metal or ammonium salts can also be used as protective colloids.

In a further preferred embodiment, the aqueous polymer dispersion according to the invention contains 0 to 10% by weight, preferably 0.05 to 3% by weight, based on the weight of the monomers used to prepare the copolymer, of dispersants, preferably of polymeric dispersants. All dispersants known to the person skilled in the art and suitable for the present purpose can be used as dispersants. Examples include water-soluble poly (meth) acrylic acids and / or their alkali or ammonium salts. However, dispersants with hydrophobic components are preferably used, such as, for example, water-soluble copolymers of vinyl aromatics, in particular styrene with ethylenically unsaturated carboxylic acids and / or their anhydrides, in particular maleic anhydride. These copolymers are particularly preferably used in the form of the corresponding ammonium and alkali salts. Some or all of these can also be introduced during or before the polymerization. Specifically, for example, ^® SMA resins, such as the ^® SMA 3000 HNa from Cray Valley, can be used.

In addition, the aqueous polymer dispersion according to the invention can, if appropriate, also film-forming auxiliaries, such as, for example, butyl diglycol and white spirit, plasticizers, such as, for example, dimethyl phthalate and dibutyl phthalate, and / or other auxiliaries, such as, for example, corrosion inhibitors, polyurethane and polyacrylate thickeners, preservatives, defoamers, such as Examples include mineral oil or silicone oil defoamers, wetting agents and other additives, as are usually used for the formulation of coating compositions.

The present invention relates both to the aqueous polymer dispersions and to processes for their preparation and their use, in particular in anti-rust coatings.

The copolymers can be prepared by the methods of free radical suspension, mini-emulsion, microemulsion and emulsion polymerization known to the person skilled in the art. However, emulsion polymerization in water is preferred as the production process. The aqueous polymer dispersions prepared therefrom are the preferred delivery form for the copolymers according to the invention.

The at least one copolymer is accordingly preferably by free radical emulsion polymerization in an aqueous medium under the

Conditions known to those skilled in the art of emulsion polymerization are carried out in the presence of radical-forming initiators and emulsifiers and, if appropriate, in the presence of protective colloids, regulators and other auxiliaries.

The conventional methods of emulsion polymerization emulsify the monomers in the aqueous phase in the presence of the emulsifiers, initiators and, if appropriate, the protective colloid and polymerize them preferably at temperatures in the range from 25 to 95 ° C. The emulsion polymerization can by the processes known to the person skilled in the art, such as, for example, batch or emulsion feed processes, the emulsion feed process being preferred, in which part of the monomer emulsion is initially introduced and polymerized before the remaining monomers are metered in as an aqueous monomer emulsion. A plurality of monomer (emulsion) feeds of different compositions are preferably metered in successively. In this way, multi-stage polymers with heterogeneous morphology of the resulting polymer film are obtained. The preparation of such multistage polymers is described, for example, in EP-A-0 795 568. Suitable multistage polymers have lower minimum film formation temperatures (MFTs) than homogeneous polymers of the same monomer composition and are therefore preferred. The lower MFT can greatly reduce the consumption of environmentally harmful, volatile, film-forming aids. Multi-stage polymers can also be produced in a particularly block-resistant manner. Deviating from this, the monomers can also be metered in according to the so-called power feed technique with a constant or abrupt gradient of the monomer composition. Both the emulsifier (s) and any protective colloids which may be used can be (partly) placed in the reactor and / or (partly) metered in with the monomer emulsion.

One or more monomer emulsion templates can be used in the process according to the invention. According to the invention, the pH of the monomer emulsion template comprising the at least one monomer b) and optionally the at least one monomer c) is> 4.7, preferably 4.7 to 11, particularly preferably 4.7 to 8 and very particularly preferably 5 to 7.

The emulsifiers are usually added together with the monomer emulsion templates, it being possible for different monomer emulsion templates to contain different emulsifiers.

The monomer template containing the at least one monomer b) preferably contains emulsifiers containing phosphate groups. Monomer templates containing monomers a), b) and optionally c) and emulsifiers containing phosphate groups are particularly preferably used.

In the case of several monomer emulsion templates, all preferably have a pH of> 4.7, preferably 4.7 to 11 and particularly preferably 5 to 7.

The polymerization is usually carried out at pH values of> 4.7, preferably 4.7 to 11 and particularly preferably 5 to 7.

Oil and / or water-soluble radical formers or redox initiator systems are used to start and carry out the polymerization. For example, potassium, sodium or ammonium peroxodisulfate, hydrogen peroxide, dibenzoyl peroxide, lauryl peroxide, tert-butyl hydroperoxide, azoisobutyronitrile and other azo initiators are preferably used, optionally together with reducing reagents such as sodium bisulfite, ^® rongalit, glucose, ascorbic acid or tartaric acid. The polymerization initiators are generally used in amounts of 0.1 to 10% by weight, preferably 0.1 to 1% by weight, in each case based on the total weight of the monomers used to prepare the copolymer.

In addition, regulators, such as thiols, can be used, n-dodecyl mercaptan, thiophenol and 2-methyl-5-tert-butylthiophenol being preferably used. The regulator or regulators are generally used in amounts of 0 to 1% by weight, based on the weight of the monomers used to prepare the copolymer.

The final pH of the aqueous dispersions is generally adjusted to pH 6 to 10 using aqueous solutions of ammonia or alkali hydroxide solutions.

The aqueous dispersions according to the invention can be prepared by adding conventional additives, pigments, plasticizers and, if appropriate, other ingredients, for example fillers, dispersants, thickeners, corrosion protection pigments, corrosion inhibitors, wetting agents, UV inhibitors, UV initiators and / or other polymeric binders can be formulated into coating compositions. They are particularly suitable for the production and use of optionally pigmented coatings, such as, for example, anti-rust coatings, clear lacquers, gloss lacquers and decorative coatings, in which increased substrate adhesion is required. The improved substrate adhesion is ensured by the presence of phosphate and, if applicable, wet adhesion promoters such as acetoacetoxy groups in the synthetic resin preparation. AAEMA and / or AAEA are particularly preferably used as functional monomers of the at least one copolymer. Suitable substrates are preferably metals, particularly preferably steel, but also inorganic surfaces containing silicate, and wood. Furthermore, acetoacetoxy groups which may be present ensure that the coatings according to the invention have a low tendency to block, ie have little tendency to block when pressing two drying surfaces which have been treated with the coatings. Good substrate adhesion is also achieved if, instead of the monomers d), reactive-crosslinking monomers e) are used. The determination of the minimum film-forming temperature (MFT) of the polymers was carried out in accordance with DIN-ISO 2115. The glass transition temperatures (T _g ) of the polymers were determined by means of DSC (Differential Scanning Calorimetry). The heating and cooling rate was 20 ° C / min in each case, and the recorded temperature range was -60 ° C to + 130 ° C. The specified glass transition temperatures of the polymers were determined in the 2nd heating cycle (mid-point evaluation). By using the Fox equation, the glass transition temperatures of the polymers can be estimated to a good approximation (see TG Fox, Bull. Am. Phys. Soc. (Ser. II), 1, 123 [1956]). The glass transition temperatures of the homopolymers built up from the monomers a), b) and c) are largely known and are listed, for example, in J. Brandrup, EH Immergut, Polymer Handbook, 2 ^nd Ed., J. Wiley, New York, 1975.

The invention is explained in more detail below on the basis of exemplary embodiments, but without being restricted thereby.

Examples 1 to 10: Preparation of the aqueous copolymer dispersions:

a) Preparation of the initiator solution: 3.75 g of potassium persulfate are dissolved in 96.25 g of deionized water (deionized water).

b) Polymerization Preparation of the monomer emulsion

Monomer emulsion liquor (monomer emulsion template): Become one after the other

491, 2 g of demineralized water, the amount of emulsifier described for the monomer emulsion (see Table 1), 19.2 g of methacrylic acid and optionally 28.8 g of AAEMA are mixed at 1000 rpm using a stirrer equipped with a propeller stirrer. The pH is then optionally adjusted to 5 using the amount described (Table 1) of 12.5% NH ₄ OH.

Finished monomer emulsion: Then a mixture of 480 g of methyl methacrylate and 480 g of n-butyl acrylate is added, the resulting mixture is emulsified for 10 minutes at 1000 rpm.

In a 3 liter glass reactor with anchor stirrer, 526.4 g of demineralized water, the amount of emulsifier described for the initial charge (see Table 1) are heated to 120 ° C. with stirring at 120 rpm, then 15.1 g of the initiator solution a) and 37 g of the monomer emulsion were added and the mixture was stirred for 15 minutes. The start of the polymerization can be recognized by the exothermic heat. The internal temperature of the reactor is always kept at 80 to 82 ° C by an external water bath. The remaining monomer emulsion is then metered in continuously within 180 minutes and the remaining initiator solution within 195 minutes through separate dropping funnels. After the end of the metering, the mixture is heated for another hour at 80 ° C., then cooled to room temperature. The pH is adjusted to 7 to 8 at 30 ° C with 12.5% ammonia water. Table 1 :

¹ : tri-sec-butylphenolhepta (ethylene glycol) ether sulfate sodium salt (approx. 50%) ² : isotridecyl octa (ethylene glycol) ether mono- and diphosphoric acid esters (approx. 100%) ³ : 4-nonylphenol poly (ethylene glycol) ether phosphoric acid monopotassium salt ( approx. 35%)

By raising the pH of the monomer emulsion liquor to pH 5 and polymerizing AAEMA into the polymer, the proportion of coagulum to be filtered off with a 180 μm sieve, including the coagulum adhering to the stirrer, is greatly reduced. This is shown by the comparison of Examples 1 with 2 and 1 with 6. Example 11

Preparation of a rust protection primer formulation with the copolymer

Dispersions of Examples 1 to 10

Table 2:

4.4 g of a 5% strength aqueous solution of Borchigel L 75 are introduced into 8 g of water with stirring. Then add AMP 90, Surfynol SE-F, Additol VXW 4973, SerAd FA 179. Now Heucophos ZP10, Mikrotalkum AT extra, Bayferrox 130 M and Millicarb are added in succession in the amounts given in Table 2 and the mixture sheared at 5000 rpm for 20 minutes in a dissolver.

After storage for one day at room temperature, the dispersions of Examples 1 to 10 (solids content approx. 47%), water and Texanol are added to the paste in the amounts described and the finished coating is stirred for a further 10 minutes at 500 rpm. In Example 11 k and 111 (see Table 3) is before Color formulation each 1.44 wt .-% based on the polymer dispersions gross SMA ^ 3000 HNa solution (Cray Valley, delivery form about 25% solids) added to the dispersion.

Table 3:

Example 12: Testing of anti-rust coatings in a constant condensation test according to DIN 50017 and storage stability of the primer formulations

The primers from Example 11 are applied to galvanized steel sheets with a 100 μm spiral doctor blade (wet layer thickness approx. 100 μm, dry layer thickness approx. 50 μm) and then 14 days at 23 ° C and 50% rel. Humidity dried. Then the dry layer thickness is determined and the sheets parallel to the long axis in the middle of the substrate are scored over the entire length of the test specimen using a scribe tool so that there is a distance of 30 mm from the sheet edges. The test is carried out in a climate change test device from Weiss at 40 ° C. and 100% rel. Humidity carried out at an exposure duration of 864 hours. The corrosion protection value (KSW) specified here is calculated as follows: KSW = (4 x bubble quantity + 1 x bubble size + 1 x degree of rust) / 6 Here, the individual assessments are made on a scale from 0 = very good to 5 = very bad, thus is the best KSW 0 and the worst 5.0. The bubble quantity, bubble size and degree of rust were determined in accordance with DIN 53209 and DIN 53210.

Storage stability is ensured by storing the primers for 3 months at room temperature determined in closed PE vessels. The assessment is carried out on a scale from 1 to 5, 1 meaning excellent storage stability without any settling of the fillers and pigments and 5 very strong settling with considerable serum formation.

Table 4: Final overview table

¹ : V = comparative example; ² : P = example according to the invention; ³ : phosphate emulsifier; ⁴ : sulfate emulsifier;

It can be seen that the use of the dispersions according to the invention, which are produced at pH 5 of the monomer emulsion liquor and thus (partially) neutralized carboxylic acid monomer groups, results in increased stability of the anti-rust primer. While the primer 11i coagulates immediately when the binder is added during the primer preparation, the formulation 11j according to the invention is stable.

As the results show (see Table 4), the storage stability of the coating is increased by the presence of AAEMA in the polymer, and the addition of a styrene-maleic anhydride copolymer to the dispersion improves this Storage stability of the binder-containing rust protection primers further. This yield significantly increases the stability of the anti-corrosion primer.

The dispersions according to the invention surprisingly produce a significantly increased rust protection effect in the constant climate condensation water test in rust protection primers, compared to polymers in which the monomer emulsion template containing carboxylic acid groups b) was not adjusted to at least pH> 4.7. Only by combining the features of the presence of a phosphate emulsifier and using a monomer emulsion template containing the building blocks b) with a pH> 4.7 are the inventive

Obtain dispersions that are low in coagulum and have good to sufficient storage stability in the primer and very good rust protection in the constant climate condensation water test.

Claims

claims: 1. Aqueous polymer dispersion with a solids content of 20 to 74% by weight, preferably 40 to 70% by weight, containing at least one copolymer A) which a) 40 to 99.95% by weight, preferably 60 to 90% by weight, based on the weight of the monomers used to prepare the copolymer, of at least one mono- or oligoethylenically unsaturated monomer which can be polymerized by free radical emulsion polymerization , b) 0.05 to 10 wt .-%, preferably 0.05 to 5 wt .-%, based on the Weight of the monomers used to prepare the copolymer, at least one ethylenically unsaturated mono- and / or oligocarboxylic acid, or their salts, and c) 0 to 5% by weight, preferably 0.05 to 2% by weight, based on the Weight of the monomers used to prepare the copolymer, at least one other ethylenically unsaturated mono- and / or oligoacid derived from phosphoric acid, phosphonic acid, sulfuric acid and / or sulfonic acid or salts thereof, contains copolymerized, which is characterized in that it contains at least 0.3% by weight, preferably 0.3 to 5% by weight, based on the weight of the monomers used to prepare the copolymer, of emulsifiers containing phosphate and / or phosphonate groups and that which the at least one monomer b) and, if present, the at least one monomer emulsion template containing the at least one monomer c) has a pH of> 4.7. 2. Aqueous polymer dispersion according to claim 1, characterized in that the copolymer A) has at least one glass transition temperature T _g in the range from -35 to 80 ° C. 3. Aqueous polymer dispersion according to claim 1, characterized in that as building blocks a) in the copolymer A) esters σ, ß-ethylenically unsaturated carboxylic acids with alkanols containing 1 to 18 carbon atoms, preferably the esters of acrylic and methacrylic acid with methanol, ethanol, propanols, butanols, pentanols, 2-ethylhexanol, iso -Octanol, n-decanol and n-dodecanol, and styrene are copolymerized. 4. Aqueous polymer dispersion according to claim 1, characterized in that the building blocks b) in copolymer A) are mono- or oligoethylenically unsaturated mono- or oligocarboxylic acids and their anhydrides or their salts are contained in copolymerized form, preferably acrylic acid, methacrylic acid, itaconic acid, maleic acid and / or fumaric acid and its salts. 5. Aqueous polymer dispersion according to claim 1, characterized in that as building blocks c) in the copolymer A) ethylenically unsaturated derivatives, in particular esters, of sulfuric, sulfonic, phosphoric and / or phosphonic acid in the form of their sodium, potassium and ammonium Salts are contained in copolymerized form, preferably sodium ethene sulfonate, 2-acrylamido-2-methylpropanesulfonic acid (AMPS) salts and potassium sulfopropyl methacrylate. 6. Aqueous polymer dispersion according to claim 1, characterized in that it contains phosphate group-containing emulsifiers, esters of phosphoric acid with alcohols and (alkyl) phenols, optionally as mixtures of mono-, di- and triesters of phosphoric acid, esters of phosphoric acid with adducts of alcohols or (alkyl ) phenols and ethylene oxide and / or propylene oxide and the sodium, potassium and ammonium salts of these compounds or the salts of these compounds with other bases. 7. Aqueous polymer dispersion according to claim 1, characterized in that the copolymer A) additionally 0.05 to 10 wt .-%, particularly preferably 0.5 to 3 wt .-%, based on the weight of the preparation of the copolymer A) Monomers used, at least one radically polymerizable monomer d) with at least one acetoacetoxy group, preferably acetoacetoxyethyl methacrylate (AAEMA) and acetoacetoxyethyl acrylate (AAEA) or acetoacetic acid vinyl ether, copolymerized. 8. Aqueous polymer dispersion according to claim 1, characterized in that the copolymer A) additionally, based in each case on the weight of the monomers used to prepare the copolymer A), up to 10% by weight, preferably up to 2% by weight. and particularly preferably 0.05 to 1 wt .-%, at least one (mono) - or (oligo) ethylenically unsaturated reactive crosslinking monomers e) copolymerized, up to 30 wt .-%, preferably up to 5 wt .-%, other copolymerizable (Mono) - or (oligo) ethylenically unsaturated monomers f) copolymerized and up to 5 wt .-%, preferably up to 2 wt .-%, particularly preferably up to 0.5 wt .-% reacting with the polymer by polymer-analogous reactions Contains building blocks g) copolymerized. 9. Aqueous polymer dispersion according to claim 1, characterized in that as reactive crosslinking monomers e) in the copolymer A) ethylenically unsaturated Derivatives of silane, in particular vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, (-Methacryloxypropyltrimethoxysilane, vinyl-tris (2-methoxyethoxy) silane and (-Methacryloxypropyl-tris (2-methoxyethoxy) silane, copolymerized or contain glycidyl / meth) or other ethylenically unsaturated derivatives of glycidol, especially glycidyl vinyl ether. 10. Aqueous polymer dispersion according to claim 1, characterized in that as other monomers f) in the copolymer A) unsaturated nitrogen-containing monomers, in particular methacrylamide and dimethylaminoethyl (meth) acrylate, derivatives of urea, in particular ß-ureidoethyl acrylate, ß-ureidovinyl ether, and φ Hydroxyalkyl (meth) acrylates and / or bifunctional (meth) acrylates, in particular 1, 4- and 1, 3-butanediol di (meth) acrylate and 1, 6-hexanediol di (meth) acrylate, bifunctional ethylene derivatives, in particular divinylbenzene and / or butadiene , and trifunctional (meth) acrylates, in particular trimethylolpropane trimethacrylate, are contained in copolymerized form. 11. Aqueous polymer dispersion according to claim 1, characterized in that such building blocks g) in at least one copolymer A) are contained, which react with functional groups of the polymer by polymer-analogous reactions, preferably epoxysilanes, particularly preferably glycidyloxypropyltrimethoxysilane, ß- (3,4-epoxycyclohexyl) ethyltrieth-oxysilane, ß- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, or oligofunctional silanes in particular 1- (triethoxysilyl) -2- (diethoxymethylsilyl) ethane and / or tris [3- (trimethoxysilyl) propyljisocyanurate. 12. Aqueous polymer dispersion according to claim 1, characterized in that it contains up to 5% by weight, preferably up to 0.5 and particularly preferably up to 0.3% by weight, based on the weight of the copolymer A used to prepare the copolymer ) monomers used, on UV-crosslinking substances which are not ethylenically unsaturated, preferably acetophenone, benzophenone and acetophenone or benzophenone derivatives which do not contain any ethylenically unsaturated polymerizable group, particularly preferably derivatives of benzophenone which, at room temperature, optionally with the addition of suitable auxiliary substances, are present as a liquid mixture or contain phosphine oxide derivatives. 13. Aqueous polymer dispersion according to claim 1, characterized in that it also contains, in addition to the emulsifiers containing phosphate and / or phosphonate groups, further emulsifiers, the total amount of emulsifiers preferably being in the range from 0.3 to 10% by weight, particularly preferably 0 , 3 to 3.5% by weight, based on the total amount of the monomers of the copolymer A), preferably those emulsifiers which contain alkyl, aryl or alkylaryl groups, a poly (ethylene oxide) as spacer between the hydrocarbon radical and the polar head group , a poly (propylene oxide) or a poly (ethylene oxide / propylene oxide) can be used. 14. Aqueous polymer dispersion according to claim 1, characterized in that it additionally contains up to 5% by weight, preferably up to 1% by weight, based on the weight of the monomers used to prepare the copolymer A), of protective colloids, preferably water-soluble carboxymethyl celluloses, particularly preferably in the form of their ammonium or alkali salts, or carboxymethyl celluloses, which optionally further substituents, in particular Alkyl or hydroxyalkyl radicals, alkyloxyalkyl radicals and dialkylamino groups, preferably carry methylcarboxymethylcellulose, ethylcarboxymethylcellulose, hydroxyethylcarboxymethylcellulose, hydroxypropylcarboxymethylcellulose, methoxyethylcarboxymethylcellulose and ethoxyethylcarboxymethylcellulose and / or polyvinyl alcohols, polyvinylpyrrolidone Polymethacrylamides and / or polycarboxylic acids and their alkali metal or ammonium salts. 15. Aqueous polymer dispersion according to claim 1, characterized in that it additionally up to 10 wt .-%, preferably 0.05 to 3 wt .-%, based on the Weight of the monomers used to prepare the copolymer A), containing dispersants, preferably containing dispersants containing hydrophobic components, in particular water-soluble copolymers of styrene with ethylenically unsaturated carboxylic acids and / or anhydrides, particularly preferably in the form of the corresponding ammonium and alkali salts. 16. A method for producing an aqueous polymer dispersion according to claim 1 by free radical suspension, mini-emulsion, microemulsion and emulsion polymerization, comprising the steps: i) providing at least one monomer emulsion template containing monomer a) and / or b) and / or c) according to claim 1 in a polymerization reactor, ii) optionally adding at least one further monomer emulsion template containing further comonomers which build up the copolymer A), and iii) carrying out the polymerization in a manner known per se, characterized in that iv) the polymerization in the presence of at least 0.3% by weight, preferably 0.3 to 5% by weight, based on the weight of the monomers used to prepare the copolymer phosphate and / or phosphonate group-containing emulsifiers and that v) the at least one monomer b) and, if present, the at least one monomer emulsion template containing at least one monomer c) has a pH of> 4.7. 17. The method according to claim 16, characterized in that the component b) and, if present, component c) containing at least one monomer emulsion template to a pH of> 4.7 with bases, preferably with sodium or potassium hydroxide and very particularly preferably with ammonia water. 18. The method according to claim 16, characterized in that the pH of the at least one monomer emulsion template is adjusted to a value in the range from 5.0 to 7.0. 19. The method according to claim 16, characterized in that the copolymer A) is prepared by free radical emulsion polymerization in an aqueous medium in the presence of radical-forming initiators and emulsifiers and, if appropriate, in the presence of protective colloids, regulators and other auxiliaries. 20. The method according to claim 16, characterized in that the monomers in the aqueous phase in the presence of emulsifiers, initiators and optionally protective colloid emulsified and polymerized at temperatures in the range from 25 to 95 ° C, the emulsion polymerization as a batch or preferably is carried out as an emulsion feed process, in which part of the monomer emulsion is introduced and polymerized before the remaining monomers are metered in as an aqueous monomer emulsion. 21. The method according to claim 16, characterized in that several monomer (emulsion) feeds of different compositions are metered in successively. 22. The method according to claim 16, characterized in that oil and / or water-soluble radical formers or redox initiator systems are used to start and carry out the polymerization, preferably potassium, sodium or ammonium peroxodisulfate, hydrogen peroxide, dibenzoyl peroxide, lauryl peroxide, tert-butyl hydroperoxide, azoisobutyronitrile and other azo initiators, optionally together with reducing reagents, in particular sodium bisulfite, the sodium salt of hydroxymethanesulfinic acid, glucose, ascorbic acid or tartaric acid. 23. The method according to claim 16, characterized in that polymerization initiators are used in an amount in the range from 0.1 to 10% by weight, preferably from 0.1 to 1% by weight, in each case based on the total weight of the Preparation of the copolymer A) monomers used. 24. The method according to claim 16, characterized in that regulators, in particular thiols, are additionally used for the emulsion polymerization, n-dodecyl mercaptan, thiophenol and 2-methyl-5-tert-butylthiophenol preferably being used in an amount of up to 1% by weight .-% are used, based on the weight of the monomers used to prepare the copolymer A). 25. The method according to claim 16, characterized in that the final pH of the aqueous dispersions with aqueous solutions of ammonia or Alkali hydroxide solutions is adjusted to a pH in the range from 6 to 10. 26. Use of polymer dispersions according to claim 1 as binders in corrosion protection coatings.