Aqueous binder compositions and their use

Abstract

Mixtures of at least one acrylic resin dispersion A and a second dispersion B, which is at least one of a polyurethane dispersion B1 and a mixture B2 of dispersions, wherein the polyurethane dispersion B1 comprises in its polymer components derived from grafted fatty acids with an average of at least 1.1 acid groups per molecule, and is producible by a multi-step reaction, wherein - in the first step, a fatty acid with at least one olefinic unsaturation is grafted with a mixture of olefinic unsaturated monomers, wherein the mixture comprises at least one acid-functional olefinic unsaturated monomer, resulting in a grafted fatty acid with an average of at least 1.1 acid groups per molecule, - in the second step, a compound that is hydroxy-functional is produced by reacting the grafted fatty acid with at least one polyhydric alcohol with at least two hydroxyl groups, at least one fatty acid and optionally at least one polyfunctional acid with at least two acid groups and / or an anhydride thereof, - in the third step, a polyurethane is produced by reacting the hydroxy-functional compound from the second step with a polyfunctional isocyanate, - the product from the third step is reacted with at least one chain extender having at least two functional groups that react with isocyanate groups, and - wherein in the reaction of the third step between the hydroxy functional compounds and the polyfunctional isocyanate, the ratio of the amount of substance n(-NCO) of isocyanate groups in the polyfunctional isocyanate to the sum of the amount of substance n(-OH) of hydroxyl groups in the hydroxy functional compounds used in the third step is at least 1.05 mol / mol, and wherein the mixture B2 of dispersions comprises a polyurethane dispersion B21, identical to B1, and an aqueous dispersed alkyd resin B22.

Description

Field of the invention

[0001] The invention relates to aqueous binder compositions, to a process for their preparation and to a process for their use. Background of the invention

[0002] Aqueous binders have been used for a variety of purposes, particularly in the production of coating compositions, adhesives, and impregnating agents. In these applications, the binders perform various functions, such as sealing pores in a porous substrate or forming a film on the surface of a substrate. The film can serve as a protective layer or as a functional layer, such as an adhesive layer, decorative layer, reflective layer, thermal insulation layer, or a layer with specific electrical or magnetic properties.

[0003] The chemical nature of the binder is crucial for the adhesion, mechanical, and chemical properties of the resulting film or layer. Although there is a certain range of properties available for a specific chemical system through modification of the base polymer, determined by the type of polymer formed in the crosslinking reaction that results in a solid film or layer, it is often desirable to be able to tailor the properties of the polymers formed in the crosslinking reaction by combining, for example, the gloss of an alkyd resin, the lightfastness of an aliphatic polymer such as aliphatic acrylate copolymers, the corrosion protection of an epoxy resin system, the scratch resistance of silicones, and the mechanical and chemical resistance of polyurethanes. State of the art

[0004] Combinations of aqueous dispersions of polyurethane resins and acrylic resins have been described in EP 0 350 157 A2. These dispersions are prepared from an aqueous polyurethane dispersion, an aqueous acrylic resin dispersion, and a further dispersion prepared by radical polymerization of a mixture of acrylic monomers in the presence of the former polyurethane resin dispersion. The polyester polyol used in this document can be prepared by reacting an unsaturated carboxylic acid with a glycol component, which embodiment provides a functional bond between the radically polymerizable acrylic monomers. If hydrazine is used for chain extension of the polyurethane, the reaction of the hydrazine groups with carbonyl or carboxamido groups of the acrylic polymer takes place during or after film formation.However, since hydrazine poses an environmental and toxicological problem, such systems cannot be widely used.

[0005] A primer composition comprising an aqueous acrylic resin and a urethane resin emulsion is known from EP 0 379 158 A2. An aqueous acrylic resin is admixed with a urethane resin emulsion, wherein the acrylic resin has an acid value of 20 mg / g to 150 mg / g and a number-average molar mass of 5 kg / mol to 30 kg / mol. The urethane resin is prepared by reacting in a solvent an aliphatic or alicyclic diisocyanate, a polyether diol or a polyester diol, a polyhydroxy compound of low molar mass and a dimethylolalkanoic acid, neutralization and dispersing in water with chain extension with water and optionally removing the solvent. The two resins are mixed in a ratio of m A of the acrylic resin to the mass m Uof the polyurethane resin, where the mass in each case is the mass of the solid resin, is mixed from 12 / 88 to 1 / 99, since it has been found that water resistance is impaired when the mass fraction of the acrylic resin exceeds 12%, and that the pigments added to the mixed dispersion are not stably maintained in a dispersed state when the mass fraction of the acrylic resin is reduced to below 1%. The primer is cured with an isocyanate crosslinker together with a clear coat.

[0006] EP 0 421 609 A2 discloses a water-based acrylic coating composition whose binder comprises mass fractions of 60% to 90% of an acrylic copolymer and 10% to 40% of a polyurethane. The acrylic copolymer is prepared in an emulsion polymerization process and comprises mass fractions of 1% to 10% of components derived from one or both of methylol methacrylamide and methylolacrylamide.

[0007] Aqueous coating compositions comprising an acrylic copolymer and a urethane oligomer dispersion are also described in EP 0 458 243 A1. The acrylic copolymer has a number-average molar mass of 6 kg / mol to 50 kg / mol and contains amide groups, acid groups, and hydroxyl groups. The urethane oligomer is derived from a hydroxyl-terminated diol, a diisocyanate compound, and active hydrogen-containing hydrophilic compounds. The prepolymer prepared therefrom is neutralized and chain-extended in an aqueous medium comprising primary or secondary polyamines. The mass fraction of the acrylic copolymer in the binary mixture is 95% to 10%, the mass in each case being the mass of the solid resin. The mixture of the two resin dispersions is crosslinked with a melamine-formaldehyde resin.

[0008] EP 0 580 163 discloses an aqueous coating composition comprising an acrylic resin emulsion and a urethane emulsion, a crosslinker, and an acid phosphate or phosphite ester. The acrylic resins have an acid value of 20 mg / g to 150 mg / g and a number-average molar mass of 5 kg / mol to 30 kg / mol. The urethane emulsion is prepared by first synthesizing a urethane prepolymer from an aliphatic or cycloaliphatic diisocyanate, a polyether diol or polyester diol with a number-average molar mass of 500 g / mol to 5 kg / mol, a low-molar-mass polyhydroxyl compound, and a dimethylolalkanoic acid. This prepolymer is mixed with water after or during neutralization of the prepolymer with a tertiary amine, and the resulting mixture is chain-extended with water. The organic solvent used during prepolymer formation is then distilled off.Melamine-formaldehyde resins and phenol-formaldehyde resins can be used as crosslinkers. The ratio of mass m. A of acrylic resin to the mass m U of urethane resin is between 90 kg / 10 kg and 60 kg / 40 kg, and the ratio of the sum of the mass m A of acrylic resin and the mass m U of urethane resin to the mass m C of the crosslinking resin (m A + m U ) / m C is between 95 kg / 5 kg and 60 kg / 40 kg, whereby the masses of the resins are always the mass of the solid resin present in the emulsion or dispersion. The acid phosphate or phosphite esters have the general formula HO-P(O)(OR 1 )(OR 2 ) or HO-P(OR 1 )(OR 2 ).

[0009] A water-based coating composition, the binder of which comprises an acrylic silane copolymer having an acid number of 2 mg / g to 100 mg / g and a hydroxyl number of up to 100 mg / g, a glass transition temperature of -40 °C to 25 °C and a weight-average molar mass of 500 kg / mol to 3000 kg / mol, and a polyurethane, which may be a polyester urethane, polyether urethane, or a polyacrylic urethane, comprising components derived from a compound having groups reactive with isocyanate groups and groups capable of forming an anion. The acrylic copolymer contains components derived from a silane acrylate or methacrylate of the formula (R1O)(R2O)RSi−CH2−(CH2)n−CH2−O−CO−C(R2)=CH2 derived from ethylenediaminesulfonate (EPS), in a mass fraction of 1% to 10%. These coating compositions are used as primers that are cured at ambient temperature for 21 days.

[0010] EP 1 435 370 A1 discloses a coating composition comprising an emulsion of an acrylic copolymer, an aqueous urethane resin, a wax emulsion, an alkaline soluble resin, and a UV absorber. The resins are defined only very generally, specifying monomers that can be used and referring to brand names in the examples, without any explanation of the composition or values ​​of characteristic parameters.

[0011] A method for forming a three-layer, once-cured film is disclosed in EP 1 477 236 A1, in which an intermediate coat, a base coat, and a clear coat are sequentially applied to an electrodeposited coating film and cured by applying heat after the final layer is applied. The intermediate coat comprises a urethane-modified polyester resin having a number-average molar mass of 1.5 kg / mol to 3 kg / mol, a melamine crosslinker resin, a blocked isocyanate, the blocker having an activated methylene group, and a non-aqueous dispersion of an acrylic resin having a core-shell structure.

[0012] An aqueous coating composition used in the formation of a multilayer film was disclosed in EP 1 852 478 A1, in which the second aqueous coating consists of three successively applied coating layers of an emulsion polymer of a monomer mixture comprising a vinyl crosslinking monomer, a carboxyl group-containing vinyl monomer, a hydroxy group-containing vinyl monomer and other polymerizable vinyl monomers, a water-soluble acrylic resin containing amide groups, a urethane emulsion and a curing agent, the former emulsion polymer having a core-shell structure.

[0013] Hybrid resins for airbag coatings are known from EP 1 887 060 A1. The hybrid resins are urethanes blended with acrylate resins, vinyl resins, silicone resins, and combinations thereof, wherein at least one of the components has a glass transition temperature of 20°C or less. The urethanes are preferably derived from polycarbonate, polytetramethylene glycol, silicon-based diol, or olefin-based diol and are prepared from these components together with an aliphatic diisocyanate and a carboxylic or sulfonic acid that also has two hydroxyl groups. These resins are said to form an interpenetrating network.

[0014] Waterborne coating compositions comprising a mixture of a urethane-based resin, a chlorinated polyolefin resin, and optionally also an acrylic-based resin are described in EP 1 958 995 A2. All resins are described only very generally. While the polycarbonate-based polyurethane resin used in the examples is identified not only by its brand name, but also by the elongation at break and tensile strength of a film produced therefrom, measured on an unspecified sample using an unspecified test method, the acrylic-based resin is identified only by its brand name.

[0015] An aqueous primer composition is disclosed in EP 2 009 071 A1. This primer comprises a modified polyolefin dispersion, an aqueous urethane resin and / or aqueous acrylic resin, a conductive metal oxide, and aluminum flakes. The urethane resin is described very generally in the specification, and no specific information can be gleaned from the examples, as the urethane resin is identified only by its brand name.

[0016] Furthermore, US 4,977,207 A discloses water-dilutable coating compositions for producing a filler based on aqueous polyurethane dispersions, as well as a process for producing a filler and the use of said water-dilutable coating composition in the automotive industry. US 6,610,784 B1 describes an aqueous crosslinkable coating composition comprising i) an autooxidatably crosslinkable polymer, ii) a non-autooxidatably crosslinkable vinyl polymer containing carbonyl groups, and iii) carbonyl-reactive groups for crosslinking the vinyl polymer. EP 2 067 562 A2 describes a process for producing water-dilutable, air-drying coating binders based on vinyl- or acrylic-modified alkyd resin emulsions and their use in water-dilutable paints that air-dry by oxidation at temperatures up to 100°C.GB 2 100 271 A describes aqueous emulsions based on combinations of acrylic-modified and urethane-modified alkyd resins for air-drying paints.

[0017] None of the cited documents disclose combinations of polyurethane resins, acrylic resins, and alkyd resins. Likewise, there is no suggestion of incorporating an alkyd resin component or oil-based component into a polyurethane resin and blending this modified polyurethane resin into an acrylic resin dispersion. Summary of the invention

[0018] In the experiments leading to the present invention, it was found that combinations of polyurethane resins, alkyd resins and acrylic resins in the form of their aqueous dispersions and, alternatively, combinations of polyurethane resins comprising components derived from grafted fatty acids with acrylic resins, both in the form of their aqueous dispersions, resulted in binders for coating compositions having the desired combination of application properties with the advantageous features of all components.

[0019] The invention therefore relates to mixtures of at least one acrylic resin dispersion A and a second dispersion B according to claim 1.

[0020] The invention further relates to the use of such mixtures according to claim 12. Detailed description of the preferred embodiments

[0021] The acrylic dispersion A preferably has a minimum film-forming temperature of less than 35°C, which corresponds to a glass transition temperature of up to 30°C, a hydroxyl number of 0 mg / g to 50 mg / g, and an acid number of 2 mg / g to 25 mg / g, prepared by emulsion copolymerization of at least two olefinically unsaturated monomers A1 and A2. Typically, at least one of the olefinically unsaturated monomers A1 and A2 is an acrylate or a methacrylate, which gives A the name "acrylic dispersion." The acrylic dispersions A preferably have particle sizes of 50 nm to 300 nm, more preferably 70 nm to 250 nm, and most preferably 90 nm to 180 nm. The mass fraction of solids in the dispersions is preferably 33% to 55%.

[0022] The monomers A1 are preferably selected from the group consisting of olefinically unsaturated monomers which have no functional group other than olefinic double bonds, i.e. the monomers which are free of hydroxyl groups, amino groups, mercapto groups, epoxy groups and acid groups, wherein the monomers A1 are selected from the group consisting of esters A11 of olefinically unsaturated carboxylic acids with monohydroxy compounds such as aliphatic, linear, branched or cyclic alcohols, olefinically unsaturated aromatic compounds A12 having at least one olefinically unsaturated aliphatic substituent on an aromatic radical which is derived from optionally substituted aromatic compounds by removing a hydrogen atom bonded to an aromatic ring, olefinically unsaturated esters A13 of an unsaturated aliphatic alcohol and a saturated aliphatic carboxylic acid, ethers A14 of the formula R 1-OR 2 , where both R 1 as well as R 2 are linear or branched aliphatic radicals having one to twenty carbon atoms and at least one of R 1 and R 2 is olefinically unsaturated, in which case the number of carbon atoms is at least two, unsaturated aliphatic ketones A15 of the formula R 3 -CO-R 4 , where both R 3 as well as R 4 are linear or branched or cyclic aliphatic radicals having one to twenty carbon atoms and at least one of R 3 and R 4 is olefinically unsaturated, in which case the number of carbon atoms is at least two, and unsaturated aliphatic halides and nitriles A16 of the formula R S -X, where X is F, Cl, Br, I or CN and R 5is an unsaturated aliphatic radical having two to twenty carbon atoms, it also being possible for more than one hydrogen atom of the olefinically unsaturated aliphatic compound R 5 -H is substituted by atoms or groups X.

[0023] Preferred monomers A11 are esters of olefinically unsaturated carboxylic acids with aliphatic alcohols having one to twenty carbon atoms, in particular methyl (meth)acrylate, ethyl (meth)acrylate, the isomeric propyl (meth)acrylates, the isomeric butyl (meth)acrylates, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, tridecyl (meth)acrylate and stearyl (meth)acrylate, where (meth)acrylate stands for acrylate or methacrylate. Other usable monomers A11 are diesters of olefinically unsaturated dicarboxylic acids with aliphatic alcohols having one to twenty carbon atoms, such as diesters of maleic, fumaric, itaconic, citraconic and mesaconic acids, with methanol, ethanol, butanol, n- and iso-propanol, n-, iso-, sec- and tert-butanol, 2-ethylhexanol, decanol, tridecanol and stearyl alcohol as well as mixed esters of these.

[0024] Preferred monomers A12 are dimethyl maleate, diethyl maleate, dimethyl fumarate and diethyl fumarate.

[0025] Preferred monomers A13 are vinyl and allyl esters of aliphatic linear or branched monocarboxylic acids such as vinyl acetate, vinyl propionate, vinyl 2-ethylhexanoate, vinyl neopentanoate, vinyl pivalate and vinyl neodecanoate and the commercially available mixture of vinyl esters of alpha-branched decanoic acids (“®Versatic acid”) as well as the analogous esters of allyl and methallyl alcohols.

[0026] Preferred monomers A14 are styrene, the isomeric mixture of vinyltoluenes, 4-vinylpyridine and 2-vinylnaphthalene.

[0027] Preferred monomers A15 are ethers of vinyl and allyl alcohols with saturated aliphatic linear or branched alcohols having one to twenty carbon atoms such as methyl vinyl ether, ethyl vinyl ether, n- and iso-butyl vinyl ether, methyl allyl ether and propyl allyl ether.

[0028] Preferred monomers A16 are olefinically unsaturated ketones, in particular ketones having a vinyl or allyl group and a linear or branched or cyclic aliphatic group having one to twenty carbon atoms, such as methyl vinyl ketone, ethyl vinyl ketone and n-propyl vinyl ketone.

[0029] The monomers A2, in addition to being olefinically unsaturated, have additional functionalities, wherein the functionalities are preferably selected from the group consisting of acid, hydroxyl and acid amide, wherein the acid functionalities can be carboxylic acid -COOH, sulfonic acid -SO2OH, sulfuric acid -O-SO2OH, phosphonic acid -PO(OH)2, phosphoric acid -O-PO(OH)2 and the acid amide functionalities can be those of the corresponding amides.

[0030] One group of monomers A21 belonging to group A2 are acid-functional olefinically unsaturated monomers that have at least one acid group, which can preferably be a carboxylic acid group -COOH, a sulfonic acid group -SO3H, a sulfinic acid group -SO2H, and a phosphonic acid group -PO(OH)2. Usable monomers A21 are acrylic acid, methacrylic acid, maleic acid, fumaric acid, the half esters of maleic or fumaric acid, vinylsulfonic acid, vinylphosphonic acid, and allyloxyhydroxypropylsulfonic acid, as well as salts thereof.

[0031] Another group of monomers A22 belonging to group A2 are hydroxyalkyl esters of the monomers listed in group A21, such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate and hydroxybutyl (meth)acrylate.

[0032] Another group of monomers A23 belonging to group A2 are acid amides based on the acid monomers A21, such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide and homologs thereof.

[0033] Further optional monomers are monomers A3, which contribute to improving the adhesion of coatings made with the acrylic copolymers comprising these optional monomers to coated substrates. These optional monomers A3 are olefinically unsaturated and carry additional groups, which can be trialkylsilane groups, trialkoxysilane groups, mixed alkyl / alkoxysilane groups, ureido groups, beta-keto acid groups, or beta-hydroxy acid groups. Particularly preferred are vinyltrimethoxysilane, vinyldimethoxymethylsilane, vinyltris(2-methoxyethoxy)silane, (methacryloxymethyl)methyldimethoxysilane, trimethoxysilane(meth)acrylate, 2-ethyl(2-oxoimidazolidin-1-yl)methacrylate, 2-ethyl(2-oxoimidazolidin-1-yl)(meth)acrylate, Acetoacetoxyethyl (meth)acrylate, beta-ketoglutaric acid vinyl ester and beta-hydroxybutyric acid allyl ester.

[0034] The mass fraction of components derived from monomers A1 in the polymer A, calculated as the ratio of the mass m A1 of monomers A1 and the mass m A of polymer A, is preferably 80% to 99.5%, particularly preferably 85% to 99%. The mass fraction of components derived from monomers A2 in polymer A, calculated as the ratio of the mass m A2 of all monomers of group A2 present in the monomer mixture and the mass m A of polymer A, is preferably 0.5% to 20%, particularly preferably 1% to 15%. The mass fraction of components derived from monomers A3, which may also be present in polymer A, is calculated as the ratio of the mass m A3 of monomers A3 and the mass m A of polymer A, is preferably 0.1% to 7%, more preferably 0.5% to 5% and most preferably 1% to 4%.

[0035] The minimum film-forming temperature (MFT) of polymer A, measured according to DIN 53787 and DIN 53 366 (ISO 2115), is preferably between -5 °C and 35 °C. In a preferred embodiment, the MFT can be in the range of 0 °C to 20 °C.

[0036] The abbreviation “(Meth)acryl” stands for acrylic or methacrylic or both.

[0037] The second aqueous dispersion B is at least one of a polyurethane dispersion B1 comprising in its polymer components derived from grafted fatty acids with an average of at least 1.1 acid groups per molecule and preparable by a multi-step reaction, and a mixture B2 of a polyurethane dispersion B21 identical to B1 and an aqueously dispersed alkyd resin B22.

[0038] The aqueous polyurethane dispersion B1 preferably comprises in its polymer a component derived from a polyfunctional isocyanate, a component derived from at least one polyhydric alcohol having at least two hydroxyl groups, a component derived from at least one fatty acid, and a component derived from a hydroxy-functional compound prepared from a grafted fatty acid, which in turn was prepared from a fatty acid having at least one olefinic unsaturation and grafted with a mixture of olefinically unsaturated monomers, wherein the mixture comprises at least one acid-functional olefinically unsaturated monomer, wherein the grafted fatty acid has an average of at least 1.1 acid groups per molecule. This aqueously dispersed polyurethane B1 is prepared in a multi-step reaction,wherein in the first step, a fatty acid having at least one olefinic unsaturation is grafted with a mixture of olefinically unsaturated monomers, the mixture comprising at least one acid-functional olefinically unsaturated monomer, resulting in a grafted fatty acid having on average at least 1.1 acid groups per molecule, in the second step, a compound which is hydroxy-functional is prepared by reacting the grafted fatty acid with at least one polyhydric alcohol having at least two hydroxyl groups, at least one fatty acid and optionally at least one polyfunctional acid having at least two acid groups and / or an anhydride thereof,and in the third step, a polyurethane is prepared by reacting the hydroxy-functional compound with a polyfunctional isocyanate and optionally a low molar mass polyhydric alcohol having a molar mass of up to 2000 g / mol and at least two hydroxyl groups per molecule and further optionally a polymeric polyol having at least two hydroxyl groups per molecule and which is derived from a polyester, a polyacrylate, a polycarbonate, a polyether or an olefin polymer and further optionally a dihydroxyalkanoic acid having a sterically hindered acid group in which the carbon atom carrying the carboxyl group is a tertiary or quaternary carbon atom. In a further step, the product from the third step is reacted with at least one chain extender having at least two functional groups that react with isocyanate groups and optionally at least one of monofunctional compounds,which are also referred to as chain stoppers and have only one group that is reactive towards isocyanate groups, and compounds that have at least two different types of groups that are differently reactive towards isocyanate groups, selected from the group consisting of primary hydroxyl groups -CH2OH, secondary hydroxyl groups >CH(OH), tertiary hydroxyl groups >C(OH)-, primary amino groups -NH2, secondary amino groups >NH and mercapto groups -SH, which are used to add further functional groups to the polyurethane.

[0039] In the third-step reaction between the hydroxy-functional compounds and the polyfunctional isocyanate, the stoichiometry must be selected such that a polyurethane is formed, i.e., the molar amount n(-NCO) of the isocyanate groups in the polyfunctional isocyanate must be at least 0.9 of the sum of the molar amount n(-OH) of the hydroxyl groups in the hydroxy-functional compounds used in the third step; in other words, the ratio n(-NCO) / n(-OH) must be ≥ 0.9 mol / mol, but preferably not more than 1.3 mol / mol. Preferably, the ratio n(-NCO) / n(-OH) is at least 1.05 mol / mol and particularly preferably at least 1.1 mol / mol. However, an excess of isocyanate groups is also necessary to add a chain extension step, as is generally known to those skilled in the art.

[0040] The mixture B2 of a polyurethane dispersion B21 and an aqueous dispersed alkyd resin B22 is obtained by mixing an aqueous polyurethane dispersion B21, which is identical to B1, and an aqueous dispersion of an alkyd resin B22.

[0041] Preferably, the aqueous polyurethane dispersion B21 has a mass fraction of solids of 30% to 65%, a hydroxyl number of 20 mg / g to 200 mg / g, which corresponds to an average hydroxy functionality a) of at least 1.8 in the polyurethane molecules, b) a mass fraction of -NH-CO- groups (molar mass = 43.02 g / mol) in the polyurethane of 5% to 25%, c) a specific content of chemically incorporated anionic groups in the polyurethane of 0 mmol / hg to 200 mmol / hg and d) a mass fraction of ethylene oxide units (molar mass = 44.05 g / mol) of 0% to 25% in the polyurethane, which are incorporated in terminal and / or lateral polyether chains in the polyurethane, wherein either the groups c) or the groups d) or both are present in the polyurethane in an amount sufficient to make the polyurethane stable in water to keep them dispersed, are chemically bonded. According to the invention, the polyurethane dispersion described as B1 is used.

[0042] Preferably, the aqueously dispersed alkyd resin B22 is as described in US 4,333,865 A1, especially preferably that of US 6,489,398 B1, particularly preferably that described in Example A3 of the latter.

[0043] The mixtures according to the invention of at least one acrylic resin dispersion A and a second dispersion B, which is at least one of a polyurethane dispersion B1 comprising in its polymer components derived from grafted fatty acids, and a mixture B2 of a polyurethane dispersion B21 and an aqueously dispersed alkyd resin B22, can preferably be used for formulating coating compositions for wood and other porous materials such as paper, cardboard, leather, textiles and concrete, but also plastic, glass and metals.

[0044] Preferably, the mixtures comprise mass fractions of 20% to 70% of acrylic resins A and 80% to 30% of the polymer of the second dispersion B, wherein the masses are always the mass of the solid resin present in the dispersion. In the case of B1, the mass fraction of components derived from grafted fatty acids in the polyurethane is preferably 12% to 40%, particularly preferably 15% to 35%, and most preferably 20% to 30%. In the case of B2, the mass fraction of the alkyd resin in the sum of the mass of alkyd resin and polyurethane resin is preferably 30% to 80%, particularly preferably 40% to 70%, and most preferably 50% to 60%.

[0045] The mixtures can be applied to substrates as is, or they can be mixed with additives such as flow or leveling additives, defoamers, wetting agents, as well as dyes or pigments. The addition of commonly used driers, such as those based on lead, cobalt, or manganese, optionally in a mixture with calcium, barium, or zirconium salts, accelerates crosslinking through air drying.

[0046] The mixtures according to the invention result in good wood penetration, rapid drying, a low tendency to form water spots and reduced dirt absorption when used to coat wood.

[0047] Particularly good results were achieved when the mixtures were prepared from aqueous dispersions of acrylic resins A and aqueous dispersions of the second polymer B, combining the preferred compositions and parameter ranges as claimed in the subclaims. ExamplesExample 1 Production of an acrylic resin

[0048] A mixing vessel was charged with 800 g of deionized water. A mixture of 102 g of an emulsifier (sodium salt of a fatty alcohol ether sulfate, Disponil® FES 32 P, Cognis GmbH) and a monomer mixture comprising 400 g of styrene, 400 g of methyl methacrylate, 900 g of butyl acrylate, 270 g of a solution comprising 67.5 g of 2-ethyl(2-oxoimidazolidin-1-yl) methacrylate and 202.5 g of methyl methacrylate, and 30 g of acrylic acid was added and stirred to form a homogeneous emulsion. A reactor was charged with 1600 g of deionized water and 12.2 g of the above-mentioned emulsifier. The contents were stirred thoroughly and heated to 80 °C under a nitrogen blanket. An initiator solution comprising 36 g of water and 4 g of ammonium peroxodisulfate was added with stirring, followed by the monomer pre-emulsion over five hours. The reaction mixture was then kept at 80 °C for another hour and then cooled to 60 °C.The remaining monomers were consumed by adding another initiator solution of 1.14 g of tert-butyl hydroperoxide and 6.68 g of water, and a solution of a reducing agent (1 g of the sodium salt of hydroxymethanesulfinic acid with 19 g of water) during a 30-minute post-reaction. The reaction mixture was then cooled to 30 °C and neutralized by adding 16 g of a 25% ammonia solution in water (25 g of NH3 in 100 g of the solution). The resulting acrylic resin dispersion had a viscosity (measured at 23 °C and 100 s) of -1 ) of 200 mPa · s, a mass fraction of solids of 44%, a pH of 8.4 and a mass average particle size of 110 nm. Example 2 Preparation of an oxidatively drying polyurethane resin2.1 (Grafted fatty acids)

[0049] 71 g of linseed fatty acid were loaded into a reactor and heated to 140 °C. A monomer mixture consisting of 55 g of isobutyl methacrylate, 10 g of para-methylstyrene, and 35 g of methacrylic acid, along with 4 g of di-tert-butyl peroxide, was added continuously over eight hours. The mixture was then kept at 140 °C until a polymer conversion of at least 99% was achieved, as confirmed by the measured mass fraction of solids. Finally, the reaction mixture was diluted with xylene. The solution had a mass fraction of solids of 75% and an acid number of 203 mg / g. 2.2 (Polyol)

[0050] 270 g of pentaerythritol, 150 g of phthalic anhydride, and 1000 g of soybean oil fatty acid were charged into a reactor and heated to 250 °C. The mixture was maintained under esterification conditions, namely at a constant temperature of 250 °C with removal of water by azeotropic distillation with xylene, until an acid number of about 4 mg / g or less was reached. The reactor was then cooled to about 170 °C, and 1000 g of the grafted fatty acid mixture from Example 1 were charged into the reactor. The mixture was heated to 205 °C and stirred at this temperature until the mixture was transparent (about 20 minutes). The reaction mixture was then cooled to 170 °C, and the remaining xylene was removed by distillation under reduced pressure until a mass fraction of solids of at least 99% was reached. The mixture was kept at 170 °C with stirring until the final acid value of 50 mg / g was reached and then cooled down.The hydroxyl number of this polyol when repeating this example ranged from 36 mg / g to 44 mg / g, with an average of 40 mg / g. 2.3 (Polyurethane)

[0051] 375 g of the polyol from Example 2.2 were charged into a vessel along with 273 g of tetramethyl-meta-xylylene diisocyanate (TMXDI) and heated to 90 °C. The resulting reaction mixture was stirred at this temperature until the isocyanate concentration (mass fraction of isocyanate groups in the reaction mixture) reached 1.5%. The prepolymer was cooled to 80 °C, and 24.5 g of triethylamine were added. After 15 minutes of homogenization, 374 g of warm (40 °C) water were added over five minutes, followed by a mixture of 2.7 g of hydrazine and 47 g of water. The product was stirred for two hours at the resulting temperature, after which the formation of a polyurethane dispersion with a mass fraction of solids of 48% was complete.The dispersion had an acid number of 45 mg / g, a pH of a 10% dispersion in water of 8.8, a mass-average particle size of 130 nm and a dynamic viscosity of 900 mPa s (measured at 23 °C and a shear rate of 10 s). -1 ). Example 3 Mixture of polyurethane and alkyd resin3.1 Synthesis of a polyurethane

[0052] A mixture of 132.8 g of a polyesterdiol prepared from phthalic anhydride and hexanediol with a hydroxyl number of 56 mg / g, 5.0 g of a monohydric polyether alcohol with a hydroxyl number of 26.2 mg / g and prepared from n-butanol, and a mixture of 83 mol of ethylene oxide and 17 mol of propylene oxide, 13.4 g of neopentyl glycol, 20.6 g of 2,2-dimethylolpropionic acid, and 90 g of N-methylpyrrolidinone was heated to 70 °C with stirring. 127.6 g of 4,4'-dicyclohexylmethane diisocyanate was added to this mixture, and the resulting mixture was stirred and heated at 110 °C for one hour until the theoretical isocyanate content was reached. The reaction mixture was cooled to 70 °C, and 15.6 g of triethylamine was added. After stirring for 15 minutes at 70 °C, 17.0 g of ethanolamine and 50 g of N-methylpyrrolidinone were added.After the reaction mixture reached 92 °C due to the exothermic reaction, the mixture was cooled to 70 °C and stirred until no free NCO groups were detected by infrared spectroscopy. Then, 5.0 g of the above monohydric polyether alcohol in 50 g of N-methylpyrrolidone was added, and the reaction mixture was stirred for 30 minutes. 391.3 g of distilled water at 50 °C was added to the mixture, and the resulting dispersion was stirred for 1 hour. The following data were determined: a pH of 9.3, a mass fraction of solids of 35%, an average hydroxy functionality per molecule of 2, and a mass fraction of NH-CO groups of 13%. 3.2 Synthesis of a urethane-modified alkyd resin

[0053] 200 g of the grafted fatty acid from Example 2.1 were loaded into a reactor along with 67 g of trimethylolpropane and 140 g of sunflower oil fatty acid and heated to 175 °C. The mixture was maintained under esterification conditions at a constant temperature of 175 °C, removing water by azeotropic distillation with xylene until an acid number of approximately 65 mg / g was reached. All solvent was then removed by distillation under reduced pressure. Within 30 minutes, 55 g of toluene diisocyanate were added at 70 °C, during which time the temperature slowly rose to 100 °C due to the exothermic reaction. The reaction was continued at this temperature until a Staudinger index of 8.5 cm 3 / g was reached. If necessary, further diisocyanate was added when repeating this experiment, taking care to ensure that no residual free isocyanate remained after the desired Staudinger index value was reached. The solid resin was then emulsified by adding 610 ml of water and 15 g of a 25% aqueous ammonia solution, resulting in an aqueous emulsion of the binder with a mass fraction of solids of 40%, a dynamic viscosity measured at 23 °C, and a shear rate of 10 s -1 of 3500 mPa s, an average particle size of 120 nm, an acid number of 52 mg / g and a pH of 8.8, measured at 10% in water. 3.3 Preparation of a mixture of polyurethane and alkyd resin

[0054] 445 g of the polyurethane dispersion from Example 3.1 and 555 g of the urethane-modified alkyd resin dispersion from Example 3.2 were stirred in a resin kettle for 30 minutes. A homogeneous dispersion was obtained. Example 4 Application test4.1 Mixture of the polyurethane dispersion from Example 2 and the acrylic resin dispersion from Example 1

[0055] 300 g of the acrylic resin dispersion from Example 1 and 700 g of the polyurethane dispersion from Example 2 were mixed with stirring in a resin kettle until a homogeneous dispersion was obtained. 4.2 Mixture of the polyurethane / alkyd resin dispersion from Example 3 and the acrylic resin dispersion from Example 1

[0056] 300 g of the acrylic resin dispersion from Example 1 and 700 g of the mixed polyurethane / alkyd resin dispersion from Example 3 were mixed with stirring in a resin kettle until a homogeneous dispersion was obtained. 4.3 Acrylic-modified alkyd resin dispersion (comparison)

[0057] An alkyd resin dispersion was prepared according to Example 1.3, resin dispersion B1 from US 5,698,625. 4.4 Results of the application test

[0058] The dispersions according to Examples 4.1, 4.2, and 4.3 (comparison) were formulated into varnishes P1, P2, and P3 by adding 1.8 g of a red pigment (Pigment Red 101), 1.7 g of a yellow pigment (Pigment Yellow 42), 0.04 g of a black pigment (Pigment Black 7 / 77266), and 38 g of water to 56 g of each dispersion. For varnishes P1 and P2, 0.6 g of a water-emulsifiable combination drier, free of nonylphenol ethoxylate and comprising organic salts of cobalt, lithium, and zirconium, was added, and 0.9 g of the drier was added to varnish 4.3.

[0059] These varnishes were applied in two coats, drying (7 days) after each application, to pressure-treated pine with a residual moisture content of less than or equal to a mass fraction of water of 5%. The first coat was applied at a wet film thickness of 107 µm (380 sq ft / gal), dried for 7 days, and then the second coat was applied at a wet film thickness of 73 µm (560 sq ft / gal) and dried again for 7 days.

[0060] Chemical resistance to vinegar and household bleach was ok in all cases on once coated pine (7 days drying). Drying time was determined as the time when no paint was removed after blotting the coating at this specified time: P1 P2 P3 (cf.) Drying time - 1st layer 9 minutes 12 minutes 13 minutes Drying time - 2nd layer 9 minutes 11 minutes 18 minutes Residual stickiness after drying 4 4 2 Residual stickiness after ninety minutes 4 4 2

[0061] Stickiness was assessed according to the following list: 0: sticky; 1: strong stickiness; 2: stickiness; 3: moderate stickiness; 4: very moderate stickiness; 5: no stickiness

[0062] In addition to the rapid drying performance observed in both inventive coatings P1 and P2 compared to P3, a significant and unexpected improvement in soil pickup performance was observed when two coats each of coatings P1, P2, and P3 were applied to pressure-treated pine, with each coat dried for 7 days. The coated panels were then preheated to 104 °F (40 °C), and a red iron oxide slurry was applied to a wet film thickness of 73 µm (560 sq ft / gal) and allowed to stand for four hours. Afterward, the slurry was washed off with water and a brush, and the surface was visually assessed (5: no damage; 4: very moderate damage; 3: moderate damage; 2: damage and moderate discoloration; 1: damage and severe discoloration; 0: severe damage). Paint P1 had a rating of 4 to 5, paint P2 had a rating of 3, and paint P3 (comparison) had a rating of 2.

[0063] These data confirm that the binder mixtures according to the invention show extremely satisfactory and unexpected results, particularly with regard to their use as a topcoat stain.

Claims

[1] Mixtures of at least one acrylic resin dispersion A and a second dispersion B, which is at least one of a polyurethane dispersion B1 and a mixture B2 of dispersions, wherein the polyurethane dispersion B1 comprises in its polymer components derived from grafted fatty acids with on average at least 1.1 acid groups per molecule, and is preparable by a multi-step reaction, wherein - in the first step, a fatty acid having at least one olefinic unsaturation is grafted with a mixture of olefinically unsaturated monomers, the mixture comprising at least one acid-functional olefinically unsaturated monomer, resulting in a grafted fatty acid having on average at least 1.1 acid groups per molecule, - in the second step, a compound which is hydroxy-functional is prepared by reacting the grafted fatty acid with at least one polyhydric alcohol having at least two hydroxyl groups, at least one fatty acid and optionally at least one polyfunctional acid having at least two acid groups and / or an anhydride thereof, - in the third step, a polyurethane is produced by reacting the hydroxy-functional compound from the second step with a polyfunctional isocyanate, - the product from the third step is reacted with at least one chain extender having at least two functional groups that react with isocyanate groups, and - wherein in the reaction of the third step between the hydroxy-functional compounds and the polyfunctional isocyanate, the ratio of the molar amount n(-NCO) of isocyanate groups in the polyfunctional isocyanate to the sum of the molar amount n(-OH) of hydroxyl groups in the hydroxy-functional compounds used in the third step is at least 1.05 mol / mol, and wherein the mixture B2 of dispersions comprises a polyurethane dispersion B21 which is identical to B1 and an aqueously dispersed alkyd resin B22. [2] Mixtures according to claim 1, wherein the mixtures comprise mass fractions of 20% to 70% of acrylic resins A and 80% to 30% of the polymer of the second dispersion B, the masses always being the mass of the solid resin present in the dispersion. [3] Mixtures according to claim 1 or 2, wherein the polymer of the second dispersion B is a polyurethane dispersion B1 comprising a mass fraction of components derived from grafted fatty acids in the polyurethane of 12% to 40%. [4] Mixtures according to claim 1 or 2, wherein the polymer of the second dispersion B is a mixture B2 of a polyurethane dispersion B21 and an aqueously dispersed alkyd resin B22 and wherein the mass fraction of the alkyd resin in the sum of the mass of alkyd resin and polyurethane resin is 30% to 80%. [5] Mixtures according to claim 4, wherein the aqueously dispersed alkyd resin B22 comprises components derived from grafted fatty acids, and wherein the mass fraction of components derived from grafted fatty acids having on average at least 1.1 acid groups per molecule in the mixture B2 is 12% to 40%. [6] Mixtures according to claim 1, wherein the acrylic resin dispersion A has a minimum film formation temperature of less than 35 °C, which corresponds to a glass transition temperature of up to 30 °C, a hydroxyl number of 0 mg / g to 50 mg / g and an acid number of 2 mg / g to 25 mg / g, prepared by emulsion copolymerization of at least two olefinically unsaturated monomers A1 and A2. [7] Mixtures according to claim 6, wherein the monomers A1 are selected from the group consisting of olefinically unsaturated monomers A1 selected from the group consisting - from esters A11 of olefinically unsaturated carboxylic acids with monohydroxy compounds such as aliphatic, linear, branched or cyclic alcohols, - from olefinically unsaturated aromatic compounds A12 having at least one olefinically unsaturated aliphatic substituent on an aromatic radical, derived from optionally substituted aromatic compounds by removing a hydrogen atom bonded to an aromatic ring, - from olefinically unsaturated esters A13 of an unsaturated aliphatic alcohol and a saturated aliphatic carboxylic acid, - from ethers A14 of formula R 1 -OR 2 , where both R 1 as well as R 2 are linear or branched aliphatic radicals having one to twenty carbon atoms, and at least one of R 1 and R 2 is olefinically unsaturated, in which case the number of carbon atoms is at least two, - from unsaturated aliphatic ketones A15 of the formula R 3 -CO-R 4 , where both R 3 as well as R 4are linear or branched or cyclic aliphatic radicals having one to twenty carbon atoms and at least one of R 3 and R 4 is olefinically unsaturated, in which case the number of carbon atoms is at least two, and - from unsaturated aliphatic halides and nitriles A16 of the formula R S -X, where X is F, Cl, Br, I or CN and R 5 is an unsaturated aliphatic radical having two to twenty carbon atoms, it being also possible that more than one hydrogen atom of the olefinically unsaturated aliphatic compound R 5 -H is substituted by atoms or groups X. [8] Mixtures according to claim 6 or 7, wherein the monomers A2, in addition to being olefinically unsaturated, have additional functionalities, wherein the functionalities are selected from the group consisting of acid, hydroxyl and acid amide, wherein the acid functionalities may be carboxylic acid -COOH, sulfonic acid -SO2OH, sulfuric acid -O-SO2OH, phosphonic acid -PO(OH)2, phosphoric acid -O-PO(OH)2 and the acid amide functionalities may be those of the corresponding amides. [9] Mixtures according to one of the preceding claims, wherein the aqueous polyurethane dispersion B1 comprises in its polymer a component derived from a polyfunctional isocyanate, a component derived from at least one polyhydric alcohol having at least two hydroxyl groups, a component derived from at least one fatty acid, and a component derived from a hydroxy-functional compound prepared from a grafted fatty acid, which in turn was prepared from a fatty acid having at least one olefinic unsaturation and grafted with a mixture of olefinically unsaturated monomers, the mixture comprising at least one acid-functional olefinically unsaturated monomer, the grafted fatty acid having on average at least 1.1 acid groups per molecule. [10] Mixtures according to one of the preceding claims 1 to 8, wherein in the mixture B2 of a polyurethane dispersion B21 and an aqueously dispersed alkyd resin B22, the aqueous polyurethane dispersion B21 has a mass fraction of solids of 30% to 65%, a hydroxyl number of 20 mg / g to 200 mg / g, which corresponds to an average hydroxyl functionality a) of at least 1.8 in the polyurethane molecules, b) a mass fraction of -NH-CO- groups, calculated with a molar mass of 43.02 g / mol, in the polyurethane of 5% to 25%, c) a specific content of chemically incorporated anionic groups in the polyurethane of 0 mmol / hg to 200 mmol / hg and d) a mass fraction of ethylene oxide units, calculated with a molar mass of 44.05 g / mol, of 0% to 25% in the Polyurethane, which are embedded in terminal and / or lateral polyether chains in the polyurethane,wherein either the groups c) or the groups d) or both are chemically bonded in the polyurethane in an amount sufficient to keep the polyurethane stably dispersed in water. [11] Mixtures according to any one of the preceding claims, which additionally comprise a siccative. [12] Use of the mixtures according to claim 1 for formulating coating compositions for wood, leather, paper, cardboard, textiles, concrete, plastic, glass and metals.