WO2011089154A2

WO2011089154A2 - A process for the production of water-emulsifiable polyurethane-polyacrylate hybrid systems

Info

Publication number: WO2011089154A2
Application number: PCT/EP2011/050686
Authority: WO
Inventors: Rolf Gertzmann; Henricus Peerlings
Original assignee: Bayer Materialscience Ag
Priority date: 2010-01-21
Filing date: 2011-01-19
Publication date: 2011-07-28
Also published as: EP2348061A1; JP2013518137A; CN102741312A; KR20120123666A; WO2011089154A3

Abstract

The present invention relates to processes for the production of cosolvent-free, aqueous, anionic polyurethane-acrylate dispersions and to their use in coating compositions.

Description

A process for the production of water-emulsifiable polyurethane-polyacrylate hybrid systems

The present invention relates to processes for the production of cosolvent-free, aqueous, anionic polyurethane-acrylate dispersions and to their use in coating compositions. Processes for the production of water-dispersible urethane (meth)acrylates are known from the literature and are mainly based on producing polyurethane starting from suitable prepolymers in the presence of acrylate and styrene monomers and, in a second step, subjecting these monomers to free-radical polymerisation. A suitable process is described in EP-B 0309115. A significant disadvantage of this process is the stability of the prepolymers in the presence of acrylate and styrene monomers. The second step of free-radical polymerisation should therefore take place as soon as possible after the production of the prepolymer.

The problem of the lack of stability has been successfully reduced by the introduction of polyurethane-polyacrylate hybrid systems. These hybrid systems are characterised in that the polyurethane prepolymer already has end groups containing acrylate groups. This prepolymer is reacted in a second step with acrylate and styrene monomers to form a polyurethane- polyacrylate hybrid system. This process is described inter alia in EP-B 01831 19 and EP-A 0098752. However, these systems have the disadvantage that polyurethane-polyacrylate hybrid systems may be formed which are insufficiently filterable, particularly if the polyurethane is based on polyether diols as the diol component.

The object of the present invention is therefore to provide processes for the production of polyether-based polyurethane-polyacrylates which can be produced without problems and have good filterability.

Surprisingly, it has now been found that the above-mentioned object is achieved by the subject-matter of the invention.

The present invention therefore provides processes for the production of aqueous dispersions containing polyurethane-polyacrylates, wherein in a first step an NCO prepolymer consisting of ai) 20 to 60 wt.% of at least one diisocyanate, aii) 20-80 wt.% of at least one polyether diol with a number-average molecular weight of 600 to 1600 g/mol, aiii) 0 to 30 g wt.% of at least one polymer diol selected from the group consisting of polyester polyols and polycarbonate diols each with a number-average molecular weight of 500 to 3000 g/mol aiv) 2 to 12 wt.% of at least one 2,2-bis(hydroxymethyl)alkane monocarboxylic acid, av) 0.1 to 15 wt.%) o f at least one hydroxy-functional, ethylenically unsaturated monomer, avi) 0 to 15 wt.%) of at least one short-chain diol with a number-average molecular weight of 62 to 400 g/mol, avii) 0 to 10 wt.% of at least one tri- or polyfunctional alcohol with a number-average molecular weight of 62 to 400 g/mol and aviii) 0 to 10 wt.% of at least one monofunctional alcohol with a number-average molecular weight of 32 to 3500 g/mol, is reacted with b) 0 to 15 wt.%) of at least one diamine with a number-average molecular weight of 60 to 300 g/mol, c) 0 to 10 wt.%) of at least one monofunctional amine with a number-average molecular weight of 32 to 350 g/mol, d) 0 to 10 wt.%) of at least one tri- or polyfunctional amine with a number-average molecular weight of 60 to 300 g/mol and e) 0.1 to 10 wt.%) of at least one neutralising agent to form a polyurethane, the above-mentioned percentages a) to e) adding up to 100 %, and in the second step, ethylenically unsaturated monomers f) are added, the mass ratio of the sum of the mass of the monomers a) to e) to the mass of the monomer f) being in the range between 40:60 and 90:10.

The mass ratio of the sum of the mass of the monomers a) to e) to the mass of the monomer f) is preferably in the range between 45:55 and 85:15.

In the prepolymer step a) an NCO content of preferably 65 to 85 %, particularly preferably of 70 % to 80 %, of the calculated NCO content is established. The acid value of the prepolymer is preferably in the range from 5 to 40 mg KOH/g, particularly preferably in the range from 15 to 35 mg KOH/g.

The polyurethane dispersions produced according to the invention are low in cosolvents. The polyurethane dispersions produced according to the invention contain preferably 0.0 to 0.9 wt.%, particularly preferably 0.0 to 0.5 wt.%, most particularly preferably 0.0 to 0.4 wt.% of cosolvents, based on the total quantity of the polyurethane dispersion.

The coating compositions produced according to the invention are low in cosolvents. The coating compositions produced according to the invention contain preferably 0.0 to 0.9 wt.%, particularly preferably 0.0 to 0.5 wt.%, most particularly preferably 0.0 to 0.4 wt.% of cosolvents, based on the total quantity of the coating composition. Cosolvents within the meaning of the present invention are polar organic solvents. Cosolvents are preferably organic solvents with a Hansen parameter in the range from 7.2 to 16.0 (cal/cm³)^0'5, as published in "Polymer Handbooks", Eds. Brandrup, J.; Immergut, E.H.; Grulke, E.A., 4th Edition, John Wiley, New York, 1999, Vll/pages 675-711.

Preferred cosolvents within the meaning of the present invention are polar organic solvents selected from the group consisting of acetone, methyl ethyl ketone, butyl diglycol, dimethyl sulfoxide, N-ethylpyrrolidone, dimethyl formamide , dimethyl acetamide, N- methylpyrrolidone, butylene glycol and dipropylene glycol dimethyl ether. Diisocyanates in the molecular weight range of 140 to 400 which are suitable as component ai) have aliphatically, cycloaliphatically, araliphatically and/or aromatically bonded isocyanate groups, such as e.g. 1 ,4-diisocyanatobutane, 1,6-diisocyanatohexane (HDI), 2- methyl-l,5-diisocyanatopentane, 1 , 5-diisocyanato-2,2-dimethylpentane, 2,2,4- and 2,4,4- trimethyl- 1,6-diisocyanatohexane, 1 , 10-diisocyanatodecane, 1,3- and 1 ,4-diisocyanato- cyclohexane, 1 ,3- and l,4-bis(isocyanatomethyl)cyclohexane, l-isocyanato-3,3,5-trimethyl-5- isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 4,4'-diisocyanatodicyclohexyl- methane, 1 -isocyanato- 1 -methyl-4(3)-isocyanatomethylcyclohexane, bis(isocyanato- methyl)norbornane, 1 ,3- and l,4-bis(2-isocyanatoprop-2-yl)benzene (TMXDI), 2,4- and 2,6- diisocyanatotoluene ( T D I ) , 2 , 4'- and 4,4'-diisocyanatodiphenylmethane, 1 , 5- diisocyanatonaphthalene or any mixtures of these diisocyanates.

Preferred as component ai) are diisocyanates in the molecular weight range of 140 to 400 with aromatically bonded isocyanate groups.

Component a)i) is preferably used in a quantity of 20 to 60 wt.%, particularly preferably in a quantity of 30 to 55 wt.%, based on the sum of all components a), b), c), d) and e).

Also suitable as diisocyanates ai) are any polyisocyanates with a uretdione, isocyanurate, urethane, allophanate, biuret, iminooxadiazinedione and/or oxadiazinetrione structure, produced by modification of simple aliphatic, cycloaliphatic, araliphatic and/or aromatic diisocyanates, made up of at least two diisocyanates, as described e.g. in J. Prakt. Chem. 336 (1994), pp. 185 - 200.

Polyether diols that are suitable as component aii) are obtainable by a method that is known per se by alkoxylation of suitable starter molecules (e.g. in Ullmanns Enzyklopadie der technischen Chemie, 4^th edition, volume 19, Verlag Chemie, Weinheim pp. 31-38 ).

The production of the polyether diols generally takes place by alkoxylation of the starter molecules in the presence of a catalyst, e.g. an alkali or alkaline earth hydroxide, oxide, carbonate or hydrogencarbonate.

The production of the polyether diols can also take place with the aid of multimetal cyanide compounds, often also referred to as DMC catalysts, which have been known for a long time and are widely described in the literature, e.g. in US 3,278,457 and in US 5,783,513. Suitable starter molecules are e.g. saturated monoalcohols such as methanol, ethanol, n- propanol, isopropanol, n-butanol, isobutanol, sec-butanol, the isomeric pentanols, hexanols, octanols and nonanols, n-decanol, n-dodecanol, n-tetradecanol, n-hexadecanol, n-octadecanol, cyclohexanol, the isomeric methylcyclohexanols or hydroxymethylcyclohexane, 3-ethyl-3- hydroxymethyloxetane or tetrahydrofurfuryl alcohol, diethylene glycol monoalkyl ethers, such as e.g. diethylene glycol monobutyl ether, unsaturated alcohols such as allyl alcohol, 1 , 1- dimethylallyl alcohol or oleyl alcohol, aromatic alcohols such as phenol, the isomeric cresols or methoxyphenols, araliphatic alcohols such as benzyl alcohol, anisyl alcohol or cinnamyl alcohol, secondary monoamines such as dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, bis(2-ethylhexyl)amine, N-methyl- and N- ethylcyclohexylamine or dicyclohexylamine as well as heterocyclic secondary amines such as morpholine, pyrrolidine, piperidine or lH-pyrazole. The alkylene oxides ethylene oxide and propylene oxide can be used during the alkoxylation reaction in any order or in a mixture.

Polyether diols that are suitable as component aii) are also the polytetramethylene glycol polyethers that are known per se in polyurethane chemistry, which can be produced e.g. by polymerisation of tetrahydrofuran by cationic ring opening. Also suitable as component aii) is polypropylene oxide.

The average molecular weight of the polyether diols aii) is preferably 650 g/mol to 1500 g/mol. Particularly preferred as component aii) are polytetramethylene glycol polyethers.

Polyester polyols are suitable as component aiii). Polyester polyols are the known polycondensates of di- and optionally poly(tri,tetra)ols and di- and optionally poly(tri,tetra)carboxylic acids or hydroxycarboxylic acids or lactones. Instead of the free polycarboxylic acids, the corresponding polycarboxylic acid anhydrides or corresponding polycarboxylic acid esters of low alcohols can be used for the production of the polyester polyols.

Examples of suitable diols are ethylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycols such as polyethylene glycol, and also propanediol, butanediol(l,4), hexanediol(l,6), neopentyl glycol or hydroxypivalic acid neopentyl glycol ester. Polyols such as e . g . trimethylolpropane, glycerol, erythritol, pentaerythritol, trimethylolbenzene or trishydroxyethyl isocyanurate may optionally also be used in addition.

Suitable as dicarboxylic acids are e.g. phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid, sebacic acid, glutaric acid, tetrachlorophthalic acid, maleic acid, fumaric acid, itaconic acid, malonic acid, suberic acid, 2-methylsuccinic acid, 3,3-diethylglutaric acid and 2,2-dimethylsuccinic acid. The possible anhydrides of these acids are also suitable. For the purposes of the present invention, the anhydrides are therefore included under the expression " acid" . It is also p o ssib le to us e monocarboxylic acids, such as b enzoic acid, hexanecarboxylic acid or fatty acids, provided that the average functionality of the polyol is greater than 2. Saturated aliphatic or aromatic acids are preferred, such as adipic acid or isophthalic acid. In smaller quantities, it is possible to use polycarboxylic acids such as trimellitic acid. Hydroxycarboxylic acids which can be used as reactants in the production of a polyester polyol with a terminal hydroxyl group are, for example, hydroxycaproic acid, hydroxybutyric acid, hydroxydecanoic acid or hydroxystearic acid. Suitable lactones are e.g. ε-caprolactone or butyrolactone.

Also suitable as component aiii) are polycarbonate diols. The suitable polycarbonate diols having hydroxyl groups are obtainable by reaction of carbonic acid derivatives, e.g. diphenyl carbonate, dimethyl carbonate or phosgene, with diols. Suitable examples of these diols are ethylene glycol, 1 ,2- and 1,3-propanediol, 1,3- and 1 ,4-butanediol, 1,6-hexanediol, 1.8- octanediol, neopentyl glycol, 1 ,4-bishydroxymethylcyclohexane, 2-methyl-l,3-propanediol, 2,2,4-trimethyl-l,3-pentanediol, dipropylene glycol, polypropylene glycols, dibutylene glycol, polybutylene glycols, bisphenol A, tetrabromobisphenol A but also lactone-modified diols. The diol component preferably contains 40 to 100 wt.% hexanediol, preferably 1,6- hexanediol and/or hexanediol derivatives, particularly preferably those having ether or ester groups in addition to terminal OH groups. The hydroxyl polycarbonates are preferably linear. However, they may optionally be readily branched by the incorporation of poly functional components, particularly low-molecular-weight polyols. Suitable for this purpose are e.g. glycerol, trimethylolpropane , 1 , 2 , 6-hexanetriol, 1 ,2,4-butanetriol, trimethylolpropane, pentaerythritol, quinitol, mannitol and sorbitol, methylglycoside or 1,3,4,6-dianhydrohexite. Component a)iii) is used preferably in a quantity of 0 to 30 wt.%, particularly preferably in a quantity of 0 to 20 wt.%, based on the sum of all components a), b), c), d) and e).

The number-average molecular weight of the polyols of component a)iii) is preferably between 500 and 3000, particularly preferably between 500 and 2000 g/mol.

The starting components a)iv) are preferably 2,2-bis(hydroxymethyl)alkane monocarboxylic acids with a total of 5 - 8 carbon atoms, i.e. compounds of the general formula (I),

in which

R denotes an alkyl residue with 1 - 4 carbon atoms. R preferably denotes an unsubstituted alkyl residue with 1 - 4 carbon atoms.

Most particularly preferably, component a)iv) is 2,2-dimethylolpropionic acid.

Component a)iv) is used preferably in a quantity of 2 to 12 wt.%, particularly preferably in a quantity of 4 to 10 wt.%, based on the sum of all components a), b), c), d) and e).

Hydroxy-functional monomers that are suitable as component av) are e.g. hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate or hydroxy monomers containing alkylene oxide units, such as e.g. addition products of ethylene oxide, propylene oxide or butylene oxide to (meth)acrylic acid, (meth)acrylic acid hydroxy ester or (meth)allyl alcohol, as well as the mono- and diallyl ethers of trimethylolpropane, glycerol or pentaerythritol. Particularly preferred as component av) are monomers selected from the group consisting of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate and hydroxybutyl methacrylate. Component a)v) is used preferably in a quantity of 0.1 to 15 wt.%, particularly preferably in a quantity of 1 to 10 wt.%, based on the sum of all components a), b), c), d) and e).

Suitable as starting component a)vi) are short-chain diols with a number-average molecular weight in the range from 62 to 400 g/mol. Particularly preferred as component a)vi) are compounds selected from the group consisting of 1 ,4-butanediol, 1 ,4-cyclohexanedimethanol and 1,6-hexanediol. Component a)vi) is used preferably in a quantity of 0 to 15 wt.%, particularly preferably in a quantity of 0 to 12 wt.%, based on the sum of all components a), b), c), d) and e).

Suitable as component avii) are tri- or polyfunctional alcohols with a number-average molecular weight in the range from 62 to 400 g/mol. Particularly preferred as component a)vii) are compounds selected from the group consisting of trismethylolpropane, trismethyolethane, glycerol, bis(trismethyolpropane), bis(trismethyolethane), pentaerythritol and bis(pentaerythritol). Component a)vii) is used preferably in a quantity of 0 to 10 wt.% particularly preferably in a quantity of 0 to 5 wt.%, based on the sum of all components a), b), c), d) and e).

Suitable as starting component a)viii) are alcohols with a molecular weight in the range from 32 to 3500 g/mol. Alcohols selected from the group consisting of methanol, ethanol, butanol, hexanol, 2-ethylhexanol, octanol and dodecanol are preferably used. Monofunctional polyethylene glycol is also preferably used. Component a)viii) is used preferably in a quantity of 0 to 10 wt.%), particularly preferably in a quantity of 0 to 8 wt.%, based on the sum of all components a), b), c), d) and e).

As component b) it is possible to use any aliphatic and/or cycloaliphatic compounds that have two isocyanate-reactive amino groups and a molecular weight in the range from 60 to 300 g/mol. Component b) is particularly preferably selected from the group consisting of ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, isophorone diamine, piperazine, p-xylylenediamine, 4,4'-diaminodicyclohexylmethane and 4,4'-diamino- 3,3'-dimethyldicyclohexylmethane. Component b) is also particularly preferably selected from the group consisting of N-(2-aminoethyl)-B-alanine, 2-(2-aminoethylamino)ethanesulfonic acid, ethylenediamine propyl- or butylsulfonic acid and 1,2- or l,3-propylenediamine-B- ethylsulfonic acid. Most particularly preferably, component b) is selected from the group consisting of ethylenediamine, isophorone diamine and 4,4'-diaminodicyclohexylmethane. Hydrazine, hydrazine hydrate and substituted hydrazines, such as e.g. N-methylhydrazine, Ν,Ν'-dimethylhydrazine and homologues thereof, as well as acid dihydrazides, such as e.g. adipi c ac i d dihydrazide, semicarbazidoalkylene hydrazides, s u c h a s e . g . β- semicarbazidopropionic acid hydrazide, semicarbazidoalkylene carbazine esters, such as e.g. 2-semicarbazidoethyl carbazine ester, or aminosemicarbazide compounds, such as e.g. β- aminoethyl semicarbazidocarbonate, are also to be understood as diamines within the meaning of the invention.

Component b) is used preferably in a quantity of 0 to 15 wt.%, particularly preferably in a quantity of 0 to 10 wt.%, based on the sum of all components a), b), c), d) and e). Suitable as component c) are monofunctional amines with a number-average molecular weight in the range from 32 to 300 g/mol, such as primary amines selected from the group consisting of methylamine, ethylamine, n-propylamine, n-butylamine, n-octylamine, laurylamine, stearylamine, isopropylamine and cyclohexylamine, as well as secondary amines selected from the group consisting of dimethylamine, diethylamine, diisopropylamine, dibutylamine and piperidine. Secondary amines such as dibutylamine are particularly preferably used. It is of course also possible to use mixtures of these. Component c) is used preferably in a quantity of 0 to 10 wt.%, particularly preferably in a quantity of 0 to 5 wt.%>, based on the sum of all components a), b), c) and d).

Suitable as component d) are tri- or polyfunctional amines with a number-average molecular weight in the range from 32 to 300 g/mol, such as diethylenetriamine. Component d) is used preferably in a quantity of 0 to 10 wt.%>, particularly preferably in a quantity of 0 to 5 wt.%>, based on the sum of all components a), b), c), d) and e).

Suitable as neutralising agent e) are, for example, ammonia, N-methylmorpholine, dimethylisopropanolamine, triethylamine, dimethylethanolamine, methyldiethanolamine, triethanolamine, morpholine, tripropylamine, ethanolamine, diethanolamine, triiso- propanolamine, N-ethyldiisopropylamine and mixtures thereof. Component e) is used preferably in a quantity of 0.1 to 10 wt.%>, particularly preferably in a quantity of 0.1 to 8 wt.%), based on the sum of all components a), b), c), d) and e).

Suitable as component f) are unsaturated, free-radically polymerisable compounds with carboxyl/carboxylate groups or sulfonic acid/sulfonate groups. Examples of these acid- functional monomers are e.g. acrylic acid, methacrylic acid, β-carboxyethyl acrylate, crotonic acid, fumaric acid, maleic acid (anhydride), itaconic acid, monoalkyl esters of dibasic acids/anhydrides such as e.g. maleic acid monoalkyl ester, and the olefinically unsaturated monomers containing sulfonic acid/sulfonate groups described in WO-A 00/39181 (p. 8, 1. 13 - p. 9, 1. 19), among which 2-acrylamido-2-methylpropanesulfonic acid may be cited as an example.

Other suitable monomers f) are e.g. (meth)acrylic acid esters with Ci to Cig hydrocarbon residues in the alcohol portion, e.g. methyl acrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert. -butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate; ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, hexyl acrylate, lauryl acrylate, monomers containing cyclic hydrocarbon residues such as cyclohexyl (meth)acrylate, cyclohexyl (meth)acrylates ring-substituted with alkyl groups, isobornyl (meth)acrylate or norbornyl (meth)acrylate, monomers containing aromatic groups, such as styrene, vinyltoluene or a- methylstyrene but also vinyl esters, vinyl monomers containing alkylene oxide units, such as e.g. condensation products of (meth)acrylic acid with oligoalkylene oxide monoalkyl ethers and monomers with other functional groups, such as e.g. epoxy groups, alkoxysilyl groups, urea groups, urethane groups, amide groups or nitrile groups. Methyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, isobornyl acrylate, isobornyl methacrylate or styrene are preferably used as component f). The reaction of the prepolymer a) with ethylenically unsaturated monomers preferably takes place in the presence of redox systems g) such as e.g. iron-EDTA complexes in combination with Rongalit C or isoascorbic acid in combination with the iron-EDTA complex.

The reaction of the prepolymer a) with ethylenically unsaturated monomers preferably takes place in the presence of initiators h) such as e.g. ammonium persulfate, organic peroxides such as e.g. di-tert. -butyl peroxide or tert.-butylperoxy-2-ethylhexanoate and azo compounds. The amounts of initiator used depend on the desired molecular weight. For reasons of process safety and greater ease of handling, peroxide initiators can also be used as a solution in suitable organic solvents of the type described in more detail below.

In a preferred embodiment, the diisocyanate ai) is added to an initial charge of components aii) to aviii) (one-shot process). This reaction is preferably carried out in the presence of a low-boiling solvent such as e.g. acetone. Components b) to e) can be added either together or separately.

The polymer synthesis reaction, i.e. the production of the prepolymer a), is preferably carried out without the use of catalysts, but it is also possible to use the catalysts known in isocyanate chemistry (e.g. tert. amines such as triethylamine, tin compounds such as tin(II) octoate, dibutyltin dilaurate and other common catalysts).

The desired solids concentration is adjusted by the addition of water and subsequent removal by distillation of the acetone used. Polyurethane-polyurea dispersions which are obtained by the process according to the invention preferably have a solids content in the range from 20 - 60 wt.%, particularly preferably in the range from 25 - 40 wt.%, in water.

The polyurethane dispersion produced according to the invention has particles with an average particle diameter preferably in the range from 20 - 1000 nm, particularly preferably in the range from 40 - 500 nm, measured by the method of dynamic light scattering in accordance with ISO 13320-1. The pH values of the white polyurethane-polyurea dispersions produced according to the invention, which are stable in storage, are in the range from 6 - 9.

The reaction of this polyurethane-polyurea to form the corresponding polyurethane-polyurea- polyacrylate preferably takes place by initially charging the polyurethane-polyurea and adding the ethylenically unsaturated monomers f) and the redox system g). At a suitable temperature, preferably between 10 and 60°C, the initiator h) is added and, on completion of the addition, the reaction mixture is stirred for several more hours at 50°C.

To produce coating compositions, the polyurethane dispersions according to the invention are used either individually or in combination with other aqueous binders.

These aqueous binders can be made up e.g. from polyester, polyacrylate, polyepoxide or polyurethane polymers. They can also be combined with radiation-curing aqueous binders. It is also possible to polymerise polymerisable, vinylically unsaturated monomers in the presence of the polyurethane dispersions according to the invention in order to obtain hybrid dispersions. For this purpose, in the presence of the polyurethane dispersion, an emulsion polymerisation of olefinically unsaturated monomers, such as esters and/or amides o f (meth)acrylic acid and alcohols with 1 to 18 C atoms, styrene, vinyl esters or butadiene, is carried out. The monomers can contain functional groups such as hydroxyl or acetoacetoxy groups as well as one or more olefinic double bonds.

The present invention thus also provides physically-drying coating compositions containing the polyurethane dispersions according to the invention.

It is also possible to add crosslinking agents before the application of the coating compositions containing the polyurethane dispersion according to the invention. Suitable for this purpose are preferably hydrophilic and hydrophobic polyisocyanate crosslinkers with free NCO groups. The polyurethane dispersions produced according to the invention are preferably used as binders in coating compositions. Coatings based on the polyurethane dispersions according to the invention can be applied on to any substrates, e.g. wood, metal, plastics, paper, leather, textiles, felt, glass or mineral substrates and on to already coated substrates. A particularly preferred use is the coating of wood and plastic floors as well as mineral floors. The present invention also provides the use of the polyurethane dispersions according to the invention for the production of clear lacquers, pigmented or unpigmented coatings. Suitable substrates are mineral or ceramic substrates and materials, concrete, hardboard materials, metallic substrates, plastics, paper, cardboard, composite materials, glass, china, textiles and/or leather. Preferred substrates are wooden and timber-like substrates, such as e.g. furniture, fibreboards, parquet, window frames, doors, panels, boards or beams.

Examples

The following abbreviations are used in the following.

Terathane® XXXX PolyTHF with an average molecular weight of XXXX g/mol, wherein XXXX can be: 250, 650, 1000 or 2000. Products from Invista Inc.

LP112 Polypropylene oxide with an average molecular weight of

1000 g/mol. A product from Bayer MaterialScience AG.

DMPS Dimethyolpropionic acid

HDO 1,6-Hexanediol

HEMA Hydroxyethyl methacrylate

T80® Desmodur T80, toluene diisocyanate, a product from Bayer

MaterialScience AG.

PU 1806® Methylene diisocyanatophenyl, a mixture of 4,4' and 2,4' isomers. A product from Bayer MaterialScience AG

Simulsol® P23 Non-ionic surfactant. A product from Seppic

HyHy Hydrazine hydrate

TEA Triethylamine

Sty Styrene

MMA Methyl methacrylate

2-EHA 2-Ethylhexyl acrylate

Fe(II) Iron(II) sulfate heptahydrate

Trilon B® EDTA tetrasodium salt, a product from BASF AG

Rongalit C® Reducing agent based on a sodium salt of a sulfinic acid derivative.

A product from BASF AG.

TBHP Tert. -butyl hydroperoxide

The viscosity is measured in accordance with DIN 3219.

Example 1: Comparison

Polyurethane-polyurea precursor:

33 g DMPS were initially charged in a 2000 ml flask together with 143 g Terathane® 250 and 15 g HEMA, and 138 g of acetone were added. A mixture of 58 g T80 and 166 g PU 1806 was added to the stirred mixture and, after an exothermic reaction was achieved, this was stirred overnight under reflux until the NCO value was 1.30% (theoretical: 1.88%). A further quantity of acetone (40 g) and 2.1 g Simulsol® P23 were then added and the mixture was homogenised. Then, 50 g of this mixture were dispersed in an aqueous initial charge at a controlled temperature of 30°C, consisting of a mixture of 1.3 g hydrazine hydrate and 20 g TEA in 695 g water. The acetone was then distilled off under vacuum (100 mbar) and at a temperature of 40°C. This resulted in a material containing fisheyes, which could not be filtered.

Example 2: Comparison

Polyurethane-polyurea precursor:

31 g DMPS were initially charged in a 2000 ml flask together with 40 g Terathane® 250 and 103 g Terathane®650 with 26 g HDO and 14 g HEMA, and 141 g of acetone were added. A mixture of 54 g T80 and 156 g PU 1806 was added to the stirred mixture and, after an exothermic reaction was achieved, this was stirred overnight under reflux until the NCO value was 1.36% (theoretical: 1.7%). A further quantity of acetone (40 g) and 2.1 g Simulsol® P23 were then added and the mixture was homogenised. Then, 500 g of this mixture were dispersed in an aqueous initial charge at a controlled temperature of 30°C, consisting of a mixture of 1.1 g hydrazine hydrate and 18 g TEA in 696 g water. The acetone was then distilled off under vacuum (100 mbar) and at a temperature of 40°C. This resulted in a material with the following properties:

Solids content: 28.2% (diluted)

Average particle size: 84 nm

pH (10% dilution): 8.81

Viscosity (D=1000 l/s): 35 mPa.s

Fisheye test: 1 Polyurethane-polyurea-polyacrylate:

The polyurethane-polyurea was initially charged in a 2000 ml flask as described above (819 g) and diluted with water (20 ml). Then, within 5 minutes a mixture consisting of styrene (71 g), MMA (32 g) and 2-EHA (17 g) was added, immediately followed by 28.8 of an aqueous mixture consisting of 1.3 g Rongalit® C, 215 mg Trilon B and 10.7 mg Fe(II) in 27.3 g water. Then, at a temperature of 30°C over a period of 20 minutes a solution of TBHP (1.0 g) in 20.4 g water was added dropwise. After an exothermic reaction was achieved, stirring was continued for a further 4 hours at 50°C. The resulting dispersion had the following properties:

Solids content: 35.6%

Average particle size: 89 nm

pH (10% dilution): 8.72

Viscosity (D=l 000 1/s): 11 mPa.s

Fisheye test: 3

Example 3: According to the invention

Polyurethane-polyurea precursor:

31 g DMPS with 148 g Terathane® 650 with 37 g HDO and 14 g HEMA were initially charged in a 2000 ml flask and 147 g acetone were added. A mixture of 54 g T80 and 156 g PU 1806 was added to the stirred mixture and, after an exothermic reaction was achieved, this was stirred overnight under reflux until the NCO value was 1.50% (theoretical: 1.7%). A further quantity of acetone (42 g) and 2.2 g Simulsol® P23 were then added and the mixture was homogenised. Then, 500 g of this mixture were dispersed in an aqueous initial charge at a controlled temperature of 30°C, consisting of a mixture of 1.23 g hydrazine hydrate and 17 g TEA in 697 g water. The acetone was then distilled off under vacuum (100 mbar) and at a temperature of 40°C. This resulted in a material with the following properties:

Solids content: 28.9% (diluted)

Average particle size: 108 nm

pH (10% dilution): 8.75

Viscosity (D=1000 1/s): 56 mPa.s

Fisheye test: 2 Polyurethane-polyurea-polyacrylate:

The polyurethane-polyurea was initially charged in a 2000 ml flask as described above (799 g) and diluted with water (40 ml). Then, within 5 minutes a mixture consisting of styrene (71 g), MMA (32 g) and 2-EHA (17 g) was added, immediately followed by 28.8 of an aqueous mixture consisting of 1.3 g Rongalit® C, 215 mg Trilon B and 10.7 mg Fe(II) in 27.3 g water. Then, at a temperature of 30°C over a period of 20 minutes a solution of TBHP (1.0 g) in 20.4 g water was added dropwise. After an exothermic reaction was achieved, stirring was continued for a further 4 hours at 50°C. The resulting dispersion had the following properties:

Solids content: 34.0%

Average particle size: 99 nm

pH (10% dilution): 8.72

Viscosity (D=1000 l/s): 9 mPa.s

Fisheye test: 1 -2

Example 4: According to the invention

Polyurethane-polyurea precursor:

31 g DMPS with 59 g Terathane® 650 and 91 g Terathane® 1000 with 42 g HDO and 14 g HEMA were initially charged in a 2000 ml flask and 149 g acetone were added. A mixture of 54 g T80 and 156 g PU 1806 was added to the stirred mixture and, after an exothermic reaction was achieved, this was stirred overnight under reflux until the NCO value was 1.30% (theoretical: 1.6%). A further quantity of acetone (42 g) and 2.2 g Simulsol® P23 were then added and the mixture was homogenised. Then, 500 g of this mixture were dispersed in an aqueous initial charge at a controlled temperature of 30°C, consisting of a mixture of 1.1 g hydrazine hydrate and 17 g TEA in 697 g water. The acetone was then distilled off under vacuum (100 mbar) and at a temperature of 40°C. This resulted in a material with the following properties:

Solids content: 28.8% (diluted)

Average particle size: 74 nm

pH (10% dilution): 8.73

Viscosity (D=1000 1/s): 19 mPa.s

Fisheye test: 1 -2

Polyurethane-polyurea-polyacrylate:

The polyurethane-polyurea was initially charged in a 2000 ml flask as described above (803 g) and diluted with water (36 ml). Then, within 5 minutes a mixture consisting of styrene (71 g), MMA (32 g) and 2-EHA (17 g) was added, immediately followed by 28.8 of an aqueous mixture consisting of 1.3 g Rongalit® C, 215 mg Trilon B and 10.7 mg Fe(II) in 27.3 g water. Then, at a temperature of 30°C over a period of 20 minutes a solution of TBHP (1.0 g) in 20.4 g water was added dropwise. After an exothermic reaction was achieved, stirring was continued for a further 4 hours at 50°C. The resulting dispersion had the following properties:

Solids content: 35.3%

Average particle size: 76 nm

pH (10% dilution): 8.71

Viscosity (D=1000 1/s): 14 mPa.s

Fisheye test: 1 -2

Example 5: According to the invention

Polyurethane-polyurea precursor:

32 g DMPS with 150 g Terathane® 1000 with 44 g HDO and 14 g HEMA were initially charged in a 2000 ml flask and 150 g acetone were added. A mixture of 54 g T80 and 156 g PU 1806 was added to the stirred mixture and, after an exothermic reaction was achieved, this was stirred overnight under reflux until the NCO value was 1.44%) (theoretical: 1.6%>). A further quantity of acetone (43 g) and 2.3 g Simulsol® P23 were then added and the mixture was homogenised. Then, 500 g of this mixture were dispersed in an aqueous initial charge at a controlled temperature of 30°C, consisting of a mixture of 1.26 g hydrazine hydrate and 18 g TEA in 697 g water. The acetone was then distilled off under vacuum (100 mbar) and at a temperature of 40°C. This resulted in a material with the following properties:

Solids content: 29.6% (diluted)

Average particle size: 90 nm

pH (10% dilution): 8.63

Viscosity (D=1000 1/s): 45 mPa.s

Fisheye test: 1 -2 Polyurethane-polyurea-polyacrylate:

The polyurethane-polyurea was initially charged in a 2000 ml flask as described above (780 g) and diluted with water (59 ml). Then, within 5 minutes a mixture consisting of styrene (71 g), MMA (32 g) and 2-EHA (17 g) was added, immediately followed by 28.8 of an aqueous mixture consisting of 1.3 g Rongalit® C, 215 mg Trilon B and 10.7 mg Fe(II) in 27.3 g water. Then, at a temperature of 30°C over a period of 20 minutes a solution of TBHP (1.0 g) in 20.4 g water was added dropwise. After an exothermic reaction was achieved, stirring was continued for a further 4 hours at 50°C. The resulting dispersion had the following properties:

Solids content: 35.4%

Average particle size: 82 nm

pH (10% dilution): 8.90

Viscosity (D=1000 l/s):29 mPa.s

Fisheye test: 1 -2

Example 6: According to the invention

Polyurethane-polyurea precursor:

32 g DMPS with 150 g Terathane® 1000 with 44 g HDO in 150 g acetone were initially charged in a 2000 ml flask. A mixture of 54 g T80 and 156 g PU 1806 was added to the stirred mixture and, after an exothermic reaction was achieved, this was stirred overnight under reflux until the NCO value was 1.91% (theoretical: 2.3%). 14 g HEMA was then added and the mixture was likewise stirred again overnight under reflux until the NCO value was 1.49% (theoretical: 1.6%). A further quantity of acetone (43 g) and 2.3 g Simulsol® P23 were then added and the mixture was homogenised. Then, 500 g of this mixture were dispersed in an aqueous initial charge at a controlled temperature of 30°C, consisting of a mixture of 1.21 g hydrazine hydrate and 18 g TEA in 697 g water. The acetone was then distilled off under vacuum (100 mbar) and at a temperature of 40°C. This resulted in a material with the following properties:

Solids content: 33.7% (undiluted)

Average particle size: 88 nm

pH (10% dilution): 8.73

Viscosity (D=1000 l/s):45 mPa.s

Fisheye test: 1 -2

Polyurethane-polyurea-polyacrylate:

The polyurethane-polyurea was initially charged in a 2000 ml flask as described above (686 g) and diluted with water (153 ml). Then, within 5 minutes a mixture consisting of styrene (71 g), MMA (32 g) and 2-EHA (17 g) was added, immediately followed by 28.8 of an aqueous mixture consisting of 1.3 g Rongalit® C, 215 mg Trilon B and 10.7 mg Fe(II) in 27.3 g water. Then, at a temperature of 30°C over a period of 20 minutes a solution of TBHP (1.0 g) in 20.4 g water was added dropwise. After an exothermic reaction was achieved, stirring was continued for a further 4 hours at 50°C. The resulting dispersion had the following properties:

Solids content: 35.2%

Average particle size: 82 nm

pH (10% dilution): 8.63

Viscosity (D=1000 1/s): 14 mPa.s

Fisheye test: 2

Example 7: According to the invention

Polyurethane-polyurea precursor:

31 g DMPS with 153 g LP112 with 45 g HDO and 14 g HEMA were initially charged in a 2000 ml flask and 150 g acetone were added. A mixture of 54 g T80 and 156 g PU 1806 was added to the stirred mixture and, after an exothermic reaction was achieved, this was stirred overnight under reflux until the NCO value was 1.38%) (theoretical: 1.6%). A further quantity of acetone (43 g) and 2.3 g Simulsol® P23 were then added and the mixture was homogenised. Then, 500 g of this mixture were dispersed in an aqueous initial charge at a controlled temperature of 30°C, consisting of a mixture of 1.12 g hydrazine hydrate and 17 g TEA in 697 g water. The acetone was then distilled off under vacuum (100 mbar) and at a temperature of 40°C. This resulted in a material with the following properties:

Solids content: 28.0% (diluted)

Average particle size: 114 nm

pH (10% dilution): 8.79

Viscosity (D=1000 1/s): 74 mPa.s

Fisheye test: 1 -2 Polyurethane-polyurea-polyacrylate:

The polyurethane-polyurea was initially charged in a 2000 ml flask as described above (825 g) and diluted with water (13 ml). Then, within 5 minutes a mixture consisting of styrene (71 g), MMA (32 g) and 2-EHA (17 g) was added, immediately followed by 28.8 of an aqueous mixture consisting of 1.3 g Rongalit® C, 215 mg Trilon B and 10.7 mg Fe(II) in 27.3 g water. Then, at a temperature of 30°C over a period of 20 minutes a solution of TBHP (1.0 g) in 20.4 g water was added dropwise. After an exothermic reaction was achieved, stirring was continued for a further 4 hours at 50°C. The resulting dispersion had the following properties:

Solids content: 35.4%

Average particle size: 98 nm

pH (10% dilution): 8.80

Viscosity (D=1000 1/s): 13 mPa.s

Fisheye test: 1 -2

Example 8: According to the invention

Polyurethane-polyurea precursor:

31 g DMPS with 52 g Terathane® 1000 and 104 g Terathane®2000 with 51 g HDO and 14 g HEMA were initially charged in a 2000 ml flask and 154 g acetone were added. A mixture of 54 g T80 and 156 g PU 1806 was added to the stirred mixture and, after an exothermic reaction was achieved, this was stirred overnight under reflux until the NCO value was 1.33% (theoretical: 1.6%). A further quantity of acetone (44 g) and 2.3 g Simulsol® P23 were then added and the mixture was homogenised. Then, 500 g of this mixture were dispersed in an aqueous initial charge at a controlled temperature of 30°C, consisting of a mixture of 1.08 g hydrazine hydrate and 17 g TEA in 698 g water. The acetone was then distilled off under vacuum (100 mbar) and at a temperature of 40°C. This resulted in a material with the following properties:

Solids content: 29.4% (diluted)

Average particle size: 68 nm

pH (10% dilution): 8.83

Viscosity (D=1000 1/s): 32 mPa.s

Fisheye test: 1 -2 Polyurethane-polyurea-polyacrylate:

The polyurethane-polyurea was initially charged in a 2000 ml flask as described above (785 g) and diluted with water (54 ml). Then, within 5 minutes a mixture consisting of styrene (71 g), MMA (32 g) and 2-EHA (17 g) was added, immediately followed by 28.8 of an aqueous mixture consisting of 1.3 g Rongalit® C, 215 mg Trilon B and 10.7 mg Fe(II) in 27.3 g water. Then, at a temperature of 30°C over a period of 20 minutes a solution of TBHP (1.0 g) in 20.4 g water was added dropwise. After an exothermic reaction was achieved, stirring was continued for a further 4 hours at 50°C. The resulting dispersion had the following properties:

Solids content: 35.1%

Average particle size: 65 nm

pH (10% dilution): 8.88

Viscosity (D=1000 l/s):25 mPa.s

Fisheye test: 1 -2

Example 9: Comparative example

Polyurethane-polyurea precursor:

31 g DMPS with 158 g Terathane® 2000 and 54 g HDO and 14 g HEMA were initially charged in a 2000 ml flask and 155 g acetone were added. A mixture of 54 g T80 and 156 g PU 1806 was added to the stirred mixture and, after an exothermic reaction was achieved, this was stirred overnight under reflux until the NCO value was 1.31% (theoretical: 1.6%). A further quantity of acetone (44 g) and 2.3 g Simulsol® P23 were then added and the mixture was homogenised. Then, 500 g of this mixture were dispersed in an aqueous initial charge at a controlled temperature of 30°C, consisting of a mixture of 1.06 g hydrazine hydrate and 17 g TEA in 698 g water. The acetone was then distilled off under vacuum (100 mbar) and at a temperature of 40°C. This resulted in a material with the following properties:

Solids content: 28.9% (diluted)

Average particle size: 70 nm

pH (10% dilution): 8.91

Viscosity (D=1000 l/s):28 mPa.s

Fisheye test: 1 -2 Polyurethane-polyurea-polyacrylate:

The polyurethane-polyurea was initially charged in a 2000 ml flask as described above (800 g) and diluted with water (39 ml). Then, within 5 minutes a mixture consisting of styrene (71 g), MMA (32 g) and 2-EHA (17 g) was added, immediately followed by 28.8 of an aqueous mixture consisting of 1.3 g Rongalit® C, 215 mg Trilon B and 10.7 mg Fe(II) in 27.3 g water. Then, at a temperature of 30°C over a period of 20 minutes a solution of TBHP (1.0 g) in 20.4 g water was added dropwise. After an exothermic reaction was achieved, stirring was continued for a further 4 hours at 50°C. The resulting dispersion had the following properties:

Solids content: 35.2%

Average particle size: 68 nm

pH (10% dilution): 8.82

Viscosity (D=1000 l/s):27 mPa.s

Fisheye test: 3

Example 10: According to the invention

Polyurethane-polyurea precursor:

31 g DMPS with 80 g Terathane® 1000, 80 g Desmophen C2200 and 43 g HDO and 13 g HEMA were initially charged in a 2000 ml flask and 155 g acetone were added. A mixture of 54 g T80 and 156 g PU 1806 was added to the stirred mixture and, after an exothermic reaction was achieved, this was stirred overnight under reflux until the NCO value was 1.39%) (theoretical: 1.6%). A further quantity of acetone (44 g) and 2.3 g Simulsol® P23 were then added and the mixture was homogenised. Then, 500 g of this mixture were dispersed in an aqueous initial charge at a controlled temperature of 30°C, consisting of a mixture of 1.13 g hydrazine hydrate and 17 g TEA in 698 g water. The acetone was then distilled off under vacuum (100 mbar) and at a temperature of 40°C. This resulted in a material with the following properties:

Solids content: 30.2% (diluted)

Average particle size: 68 nm

pH (10% dilution): 8.94

Viscosity (D=l 000 l/s):43 mPa.s

Fisheye test: 1

Polyurethane-polyurea-polyacrylate:

The polyurethane-polyurea was initially charged in a 2000 ml flask as described above (766 g) and diluted with water (73 ml). Then, within 5 minutes a mixture consisting of styrene (71 g), MMA (32 g) and 2-EHA (17 g) was added, immediately followed by 28.8 of an aqueous mixture consisting of 1.3 g Rongalit® C, 215 mg Trilon B and 10.7 mg Fe(II) in 27.3 g water. Then, at a temperature of 30°C over a period of 20 minutes a solution of TBHP (1.0 g) in 20.4 g water was added dropwise. After an exothermic reaction was achieved, stirring was continued for a further 4 hours at 50°C. The resulting dispersion had the following properties:

Solids content: 34.5%

Average particle size: 67 nm

pH (10% dilution): 8.6

Viscosity (D=l 000 l/s):21 mPa.s

Fisheye test: 1 -2

The fisheye test was carried out as follows: 300 g of water were added to the PUHA (100 g) that formed and this was passed through a black filter. The residue then remaining on the filter was qualitatively assessed with the following scoring:

1 : no residue whatsoever

2. a few small coarse particles

3 : coarse and small particles

4: the filter is almost completely covered with white particles

5. the filter blocks immediately

A score of 1 -2 is acceptable.

Table: Summary of results.

Example/type Polyol type Molecular wt. of ether Fisheye test

1/Comp. Terathane 250 No PAC possible

2/Comp. Terathane 450 3

3/Invention Terathane 650 1-2

4/Invention Terathane 825 1-2

5/Invention Terathane 1000 1-2

6/Invention* Terathane 1000 2

7/Invention LP 112 1000 1-2

8/Invention Terathane 1500 1-2

9/Comp. Terathane 2000 3

10/Invention Terathane/C2200 1000 1-2 *Prepolymer method.

All the examples have approximately the same hard segment content and the same acid value. Owing to the significantly shorter reaction time, the one-shot method is preferred. Comparative Example 1 describes the use of Terathane® 250, wherein the polyurethane urea contains many fisheyes and does not allow any grafting at all with vinyl monomers.

Comparative Example 2 describes a 1 :1 molar mixture of Terathane® 250 and 650. Although the corresponding polyurethane-polyurea can be produced, the corresponding grafted system is difficult to filter. Examples 3 to 8 according to the invention describe the use of Terathane® or LP 112 with a number-average molecular weight of 650 and 1500 g/mol. The corresponding grafted systems can be readily filtered. The same applies to Example 10, wherein a mixture of T1000 and C2200 is used.

Comparative Example 9 describes the use of Terathane® 2000, wherein the corresponding grafted system displays a coating.

The Examples show that a readily filtered grafted system is only possible if ether polyols are used which have an average molecular weight between 650 and 1500 g/mol.

Claims

A process for the production of aqueous dispersions containing polyurethane- polyacrylates, wherein in a first step an NCO prepolymer consisting of ai) 20 to 60 wt.% of at least one diisocyanate, aii) 20-80 wt.% of at least one polyether diol with a number-average molecular weight of 600 to 1600 g/mol, aiii) 0 to 30 g wt.% of at least one polymer diol selected from the group consisting of polyester polyols and polycarbonate diols each with a number-average molecular weight of 500 to 3000 g/mol, aiv) 2 to 12 wt.% of at least one 2,2-bis(hydroxymethyl)alkane monocarboxylic acid, av) 0.1 to 15 wt.%) of at least one hydroxy- functional, ethylenically unsaturated monomer, avi) 0 to 15 wt.%) of at least one short-chain diol with a number-average molecular weight of 62 to 400 g/mol, avii) 0 to 10 wt.% of at least one tri- or polyfunctional alcohol with a number- average molecular weight of 62 to 400 g/mol and aviii) 0 to 10 wt.% of at least one monofunctional alcohol with a number-average molecular weight of 32 to 3500 g/mol is reacted with b) 0 to 15 wt.%) of at least one diamine with a number-average molecular weight of 60 to 300 g/mol, c) 0 to 10 wt.%) of at least one monofunctional amine with a number-average molecular weight of 32 to 350 g/mol, d) 0 to 10 wt.% of at least one tri- or polyfunctional amine with a number- average molecular weight of 60 to 300 g/mol and e) 0.1 to 10 wt.% of at least one neutralising agent to form a polyurethane, the above-mentioned percentages a) to e) adding up to 100%, and in the second step, ethylenically unsaturated monomers f) are added, wherein the mass ratio of the sum of the mass of the monomers a) to e) to the mass of the monomer f) is in the range between 40:60 and 90:10.

2. The process according to claim 1 , wherein the mass ratio of the sum of the mass of the monomers a) to e) to the mass of the monomer f) is in the range between 45:55 and 85:15.

3. The process according to claim 1, wherein the polyether diol has a number-average molecular weight in the range from 650 to 1500 g/mol.

4. The process according to claim 1, wherein the reaction in the second step takes place in the presence of initiators h) selected from the group consisting of ammonium persulfate, organic peroxides and azo compounds.

5. The process according to claim 1, wherein the reaction in the second step takes place in the presence of redox systems.

6. The process according to claim 1, wherein the components aii) to aviii) are mixed and reacted to by addition with ai) (one-shot process).

7. Aqueous dispersions obtainable by a process according to claims 1 to 6.

8. Coating compositions containing an aqueous dispersion according to claim 7 or obtainable by a process according to claims 1 to 6.

9. The use of a coating composition according to claim 8 for the coating of wood, metal, plastics, paper, leather, textiles, felt, glass or mineral substrates.