The invention relates to cationic water-dilutable binders, to a process of production thereof, and to a method of use of these cationic water-dilutable binders for the preparation of paints.

Background of the Invention

Cathodic electrodeposition, also referred to as "CED", is an accepted and efficient way to provide substrates of base metals with a protective film layer in order to prevent corrosion. These binders usually comprise a film-forming resin based on epoxide resin-amine adducts or acrylic resins having amino groups that can be dispersed in water upon neutralisation with an acid, and forms cations usually based on organically substituted ammonium structures. These cations are deposited on conductive layers that form the cathode of an electrochemical system in a bath containing this cathode metal substrates, an anode, and a bath filled with an aqueous dispersion of the binder, and optionally, pigments and fillers that are admixed to the binder in the form of a pigmented paste, are discharged on this cathode, and build a layer that is subsequently, after rinsing the surface to remove residues of the bath liquid, baked to crosslink the deposited paint film. This film usually has a layer thickness of from 0.015 mm to 0.035 mm. Commonly used crosslinkers include blocked, or capped, isocyanates that are uncapped by the action of heat (up to 185 °C), to split off the blocking agent, and free the isocyanate functional groups of the crosslinker that can then react with hydroxyl groups or amino groups present in the binder to form the cured paint layer. Common blocking agents are volatile organic compounds having functional groups that reversibly add to an isocyanate group under formation of a urethane or urea group, such as hydroxy-functional compounds which may be phenols, oximes, aliphatic alcohols, or partial esters of multivalent alcohols, amine-functional compounds such as aliphatic amines, mixed aromatic-aliphatic amines, lactams, pyrazoles, and also C-H acidic compounds such as malonates. Due to the release of these blocking agents during curing, a loss in mass is observed, referred to as "stoving loss", which also is frequently manifested in the form of bubbles that may be formed in the paint layer during curing if the gaseous blocking agents cannot escape from the paint film due to formation of a less permeable surface of the paint film. Moreover, a substantial amount of energy is used to heat the substrate to a temperature where the blocking agent is cleaved from the blocked isocyanate. Lastly, the gaseous blocking agents which are often irritant or even toxic, have to be collected and removed from the exhaust air of the baking ovens by appropriate treatment such as incineration which also consumes energy.

In WO 2015/055 804 Al, a cationic water-dilutable binder has been provided that can be applied to a conductive substrate by the method of cathodic electrodeposition, and which avoids the disadvantages as mentioned hereinabove. WO 2015/055 805 Al relates to a process to coat conductive substrates by the method of cathodic electrodeposition, followed by removal of the coated substrate, rinsing or otherwise cleaning the surface, and subjecting the coated substrate to a drying step at a temperature of from ambient temperature (25 °C) up to 120 °C, optionally followed by coating the dried coated substrate with at least one further coating layer. While these coatings perform well on zinc phosphated steel, problems with the surface quality have been found with bare steel as substrate. "Micro pin-holes" are formed, depending on coating conditions like deposition-voltage, bath temperature, use of solvents, which are not found in visual inspection, but can give rise to corrosion when the coated item is subjected to a corrosive environment which is simulated by salt-spray test and humidity chamber test in test laboratories. Another macroscopic phenomenon on the surface are deposition failures like "swirls", i. e., inhomogeneous film building caused mainly by turbulences in the dip bath due to stirring, which may lead also to a poor, inhomogeneous surface of a coating layers above the electrodeposited layer.

It is therefore an object of this invention to improve the quality and corrosion resistance of bare steel coated with the cationic water-dilutable binder described in WO 2015/055 804 Al, and in WO 2015/055 805 Al. Summary of the Invention

A cationic water-dilutable binder comprising a urethane additive has been provided by this invention that can be applied to a conductive substrate by the method of cathodic electrodeposition which binder crosslinks physically, i. e. without addition of a chemical substance, referred to as crosslinker, which crosslinker reacts with a resinous binder in a polycondensation or polyaddition reaction, or initiates a polymerisation of polymerisable, usually olefinically unsaturated, resinous binder.

This cationic water-dilutable binder comprises a chain-extended epoxy-amine adduct resin EA and bismuth compound B which is a water-soluble bismuth salt wherein the anion comprises an anion derived from a hydroxycarboxylic acid, or a bismuth chelate complex, both individually, or together, referred to as "B", wherein both the adduct resin EA and the bismuth compound B are dissolved or dispersed in water, and additionally, a urethane additive U.

Preferably, this bismuth salt or chelate B is present in an amount such that the amount of substance n(Bi) of elemental bismuth, divided by the mass m(R) of resin solids present in the dispersion is from 2 mmol/kg to 1000 mmol/kg, preferably from 5 mmol/kg to 500 mmol/kg, and with particular preference, from 10 mmol/kg to 300 mmol/kg.

The urethane additive U which has at least two urethane groups >N-CO-0- in its molecule, and optionally has further functional groups in its molecule which are selected from the group consisting of hydroxyl groups, and carboxyl groups, is obtained by reacting

(a) at least one at least difunctional organic isocyanate Ul, at least one at least difunctional aliphatic alcohol U2, and optionally at least one monohydric aliphatic alcohol U3 to form a hydroxyurethane U123, or

(b) at least one aliphatic diamine U5 with a cyclic aliphatic carbonate U4 to form a dihydroxyurethane U54 or a mixture thereof with unreacted diamine U5, which is then reacted with diisocyanate Ul to form a hydroxyurethane U541 optionally also comprising a hydroxyurea-urethane U51, or (c) at least one oligomeric or polymeric aliphatic diol or triol U6 with at least one at least difunctional organic isocyanate Ul to form a hydroxyurethane U61, and reacting this with a cyclic acid anhydride U7 to convert a part or all of the hydroxyl groups by formation of an ester group, and liberation of an acid group, to form an acid-functional urethane U617.

Paints prepared using the cationic water-dilutable binder comprising a urethane additive can be used to provide corrosion-resistant coatings on a variety of substrates, particularly metal substrates, especially substrates made from base metals. These coatings have good adhesion to these substrates, and also, show very good interlayer adhesion when combined with topcoat materials based on different chemistries, such as water-borne one-pack and two-pack acrylic resin based paints, air-drying alkyds, solvent-borne two-pack polyurethane paints based on hydroxyfunctional acrylic resins or acrylic copolymer resins, powder topcoats, and particularly, paints based on crosslinking by Michael addition. One aspect of the present invention is therefore also to provide a process to coat metal substrates, particularly base metal substrates, which comprises coating a metal substrate with the cationic water-dilutable binder comprising a urethane additive, preferably by dipping the substrate into a bath comprising the cationic water-dilutable binder with the urethane additive, forming a paint film on the metal surface preferably by cathodic electrodeposition, optionally removing nonadherent paint by rinsing or otherwise cleaning the painted surface, drying and heating to effect crosslinking of the paint film, and optionally, overcoating the dried substrate with at least one further coating layer.

General Composition and Process

The cationic water-dilutable binders of this invention comprise a water-soluble bismuth salt or chelate complex, both individually, or together, referred to as "B", comprising bismuth ions and ions of an organic acid-functional moiety which is preferably able to form a chelate complex with bismuth, a chain-extended epoxy-amine adduct EA, and a urethane additive U, which has at least one urethane group in its molecule, and optionally, at least one active hydrogen- containing functional group selected from the group consisting of hydroxyl groups and carboxyl groups, wherein the chain-extended epoxy-amine adduct EA optionally comprises moieties derived from epoxide compounds El having on average at least one, and less than two, epoxide groups per molecule, and wherein the chain-extended epoxy-amine adduct EA mandatorily comprises moieties derived from

epoxide compounds E2 having at least two epoxide groups per molecule,

low molar mass epoxide compounds E3 having two epoxide groups per molecule, and a molar mass of from 170 g/mol to 800 g/mol, and one or more of

amidoamines A41 having at least one amide group and at least one amino group, made from amines Al having at least two amino groups per molecule, and from three to twenty carbon atoms, selected from the group consisting of at least two primary amino groups per molecule, at least one primary and at least one secondary amino group per molecule, and at least two secondary amino groups per molecule, and a fatty acid A4 which has from six to thirty carbon atoms and optionally, at least one olefinic unsaturation per molecule,

amines Al having at least two amino groups per molecule, and from three to twenty carbon atoms, selected from the group consisting of at least two primary amino groups per molecule, at least one primary and at least one secondary amino group per molecule, and at least two secondary amino groups per molecule,

amines A2 which have from three to twenty carbon atoms and at least one secondary amino group per molecule, and optionally, at least one further reactive group which are preferably hydroxyl groups,

amines A3 having from four to twenty carbon atoms and at least one tertiary, and at least one primary amino group per molecule,

fatty acids A4 having from six to thirty carbon atoms, and one carboxylic acid group, or mixtures of two or more of such fatty acids, whereto optionally, an amount of up to 60 % of the mass of fatty acids A4, of a dicarboxylic or higher functional acid A4' may be added, which higher functional acids A4' are preferentially dimeric fatty acids, and phenolic compounds A5 having from six to twenty carbon atoms and at least two phenolic hydroxyl groups. oxy-amine adduct is preferably made in a process wherein

in step a, a mixture Ml is prepared from one or more of A41, Al, A2, A3, A4, and A5, in an optional step b, the mixture Ml is reacted with an epoxide compound El to reduce the number of epoxide-reactive groups to between 50 % and 90 % of the number of such groups in the mixture Ml before this reaction step, to yield a mixture M2

in an optional step c, at least one of Al, A2, A3, A4, and A5 are added to the mixture Ml of step a, or to the mixture M2 of step b, to yield a mixture M3,

in step d, the mixture Ml of preceding step a, or the mixture M2 of preceding step b, or the mixture M3 of preceding step c, is diluted with an inert solvent S, and epoxide compound E2 is added under heating, wherein the quantity of E2 is preferably chosen such that the amount of substance n(EP;E2) of epoxide groups in E2 is

from 30 % to 70 % of the amount of substance n(RG;Ml) of epoxide-reactive groups RG comprised in mixture Ml, or

from 30 % to 70 % of the amount of substance n(RG;M2) of epoxide-reactive groups RG comprised in mixture M2 if optional step b is performed, or from 30 % to 70 % of the amount of substance n(RG;M3) of epoxide-reactive groups RG comprised in mixture M3 if optional steps b and c are performed, wherein the epoxide-reactive groups RG are primary, secondary or tertiary amino groups, aromatic and aliphatic hydroxyl groups, thiol groups, and acid groups, such as carboxyl groups, which are present in the mixtures, their reactivity being controlled by their chemical nature and by steric considerations, and

the reaction is continued until at least 95 % of the epoxide groups in E2 are consumed, to form an intermediate I

in step e, a solution of the bismuth salt or chelate B in deionised water is prepared by heating under stirring, bismuth oxide B12O3 or a basic bismutyl compound, both individually or collectively referred to as Bl, with an excess of from 100 % to 700 % of the stoichiometric amount of an organic acid B2 and/or an organic chelate former B3, in step f, the solution of the intermediate I of step d is added under stirring to the solution of the bismuth salt or chelate B in deionised water prepared in step e, to form a dispersion, and

in step g, after optional addition of further water, the dispersion of step f is heated, and epoxide compound E3 is added and reacted until all epoxide groups are consumed to form the chain-extended epoxy-amine adduct EA.

Chain-extension refers to the reaction made in the last step g which is made in the aqueous phase.

The urethane additive U is added after step g, or preferably, added to the solution of the bismuth salt or chelate, B, together with the solution of the intermediate I, during step f, or separately after step f, or it is added, in another preferred embodiment, to the solution of the intermediate I after step d.

The aqueously dispersed mixture of chain-extended epoxy-amine adducts EA, a urethane additive U, and a bismuth salt or chelate B as described hereinabove, or made by the process as detailed hereinabove can be used to form coating films on substrates where comprising mixing and homogenising the binder mixtures, where optionally, pigments and/or fillers may be added to this binder mixtures to form a coating composition, which said coating composition is applied to a substrate preferably by cationic electrodeposition, and subjected to drying without addition of a curing agent.

Detailed Disclosure of the Preferred Embodiments

A compound is defined herein by comprising "moieties derived from" certain starting materials, if it is made from starting materials which are molecules having functional groups that lead to reaction between these starting materials under formation of compound molecules that contain fragments of the molecules of the starting materials with the functional groups removed, and newly formed bonding groups from these functional groups that connect these fragments. Starting materials having, e. g., hydroxyl groups react under esterification with an acid or an acid anhydride, thereby forming an ester which comprises the part of the hydroxy-functional molecule with the hydroxyl group removed, which part is referred to as "moiety derived from that molecule", and the bonding group is an ester group in this example. So a moiety derived from 1,6-dihydroxyhexane is 1,6-hexanediyl. Likewise, a moiety derived from a diisocyanate of formula 0=C=N-X-N=C=0 which is reacted with an alcohol to form a urethane is the divalent group -X-. A moiety derived from an oxirane molecule which is reacted with an acid under formation of an ester is then R-CH(OH)-CH2 - when the oxirane ring is bound to a monovalent group R.

In a preferred embodiment, moieties derived from an amidoamine A41 and at least one of the amines Al, A2, and A3 are present in the epoxy-amine adduct EA.

In a further preferred embodiment, an amidoamine A41 and at least one of the amines Al, A2, and A3 are present in mixture Ml.

In a further preferred embodiment, an amidoamine A41, an amine Al, and at least one of the amines A2 and A3 are present in mixture Ml. In a further preferred embodiment, an amidoamine A41, an amine A2 and at least one of the amines Al and A3 are present in mixture Ml.

In a further preferred embodiment, an amidoamine A41, an amine A3, and at least one of the amines Al and A2 are present in mixture Ml.

In a further preferred embodiment, at least one of the amines Al, A2, and A3 is added to the mixture M2.

In a further preferred embodiment, moieties derived from an amidoamine A41, an amine Al, and at least one of the amines A2 and A3 are present in the epoxy-amine adduct EA. In a further preferred embodiment, moieties derived from an amidoamine A41, an amine A2, and at least one of the amines Al and A3 are present in the epoxy-amine adduct EA. In a further preferred embodiment, moieties derived from an amidoamine A41, an amine A3, and at least one of the amines Al and A2 are present in the epoxy-amine adduct EA.

In a further preferred embodiment, a fatty acid A4 is present in mixture Ml. In a further preferred embodiment, moieties derived from a phenolic compound A5 are present in the epoxy-amine adduct EA.

In a further preferred embodiment, a phenolic compound A5 is present in the mixture M2. In a further preferred embodiment, the mixture Ml is reacted with an epoxide compound El having on average, at least one, and less than two, epoxide groups per molecule.

It is also preferred to use more than one of the above preferred selections together.

The epoxide components El have at least one, and less than two, 1,2 -epoxide groups per molecule, and are of aromatic or aliphatic nature. Glycidyl ethers of monohydric aliphatic or mixed aliphatic-aromatic alcohols, or glycidyl esters of aliphatic or aromatic monocarboxylic acids are preferred as monoepoxides. The alcohols are preferably selected from the group consisting of 2-ethyfhexanol, decanol, tridecanol, stearyl alcohol, and benzyl alcohol. The acids are preferably selected from the group consisting of branched aliphatic monocarboxylic acids having from 5 to 11 carbon atoms, particularly, glycidyl neopentanoate, glycidyl 2-ethyl hexanoate, glycidyl neodecanoate, and the mixtures of such acids which are commercially available under the trade names of ©Versatic acids. Mixtures of such ethers and such esters can likewise be used. Such mixtures are preferably made in a way that the average number of epoxide groups per molecule, is at least 1.0, and less than 2.0, preferably, from 1.2 to 1.8. The epoxide components E2 have at least two, preferably on average two, epoxide groups per molecule. Preferred are glycidyl esters of multifunctional organic acids, and glycidyl ethers of multifunctional organic hydroxy compounds, both of which may be aliphatic or aromatic. Further preferably, they have a specific amount of epoxide groups in the range of from 3.0 mol/kg to 5.8 mol/kg ("epoxide equivalent" from 170 g/mol to 333 g/mol). Particularly preferred are aromatic epoxide resins based on aromatic dihydroxy compounds where the hydroxyl group is bound to an aromatic carbon atom, such as those derived from bisphenol A, bisphenol F, particularly the so-called "liquid epoxy resins".

As epoxide component E3, a selection from the group E2 is made, particularly diglycidyl ethers of aromatic or aliphatic diols, and diglycidyl esters of aromatic or aliphatic diacids, or mixtures of these. Among the diglycidyl ethers of diols, the diglycidyl ethers of bisphenol A (2,2-bis-(4- hydroxyphenyl)-propane), and of bisphenol F (bis-(4-hydroxyphenyl)-methane) are preferred, as well as the diglycidyl ethers of ethylene glycol, 1,-4-butylene glycol, and of oligomeric or polymeric 1,2-propylene glycols. As diglycidyl esters, particularly those derived from dimeric fatty acids are mentioned here. Both the glycidyl ethers of aliphatic oligomeric or polymeric diols, as well as the diglycidyl esters of aliphatic diacids act as flexibilising components in the epoxy-amine adducts of this invention. Particularly preferred as E3 are epoxide compounds having a molar mass of from 170 g/mol up to 800 g/mol, and among these, epoxide resins made from bisphenol A and epichlorohydrin. It is especially preferred to use the diglycidyl ether of bisphenol A, having a specific amount of epoxide groups of 5.9 mol/kg ("epoxide equivalent" of 170 g/mol), the commercial product having a slightly lower specific amount of epoxide groups of from 5.7 mol/kg to 5.8 mol/kg.

It is possible to use the same compounds in E2 and in E3, the distinction is made to reflect the step of addition of these epoxide-functional compounds E2 and E3 in the process according to the invention. The amines Al are selected from aliphatic linear, branched, or cyclic amines each having at least one secondary and at least one primary amino group, preferably two primary amino groups, and from three to twenty carbon atoms. Preferred amines include N-methyl ethylene diamine, 3- or 4-aminopiperidine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, N,N'-bis-(2-aminoethyl)-l,3-diamino-propane, N,N'-bis-(3-aminopropyl)-l,2-di-aminoethane, N,N'-bis-(3-aminopropyl)-l,3-diaminopropane, N,N'-bis-(3-aminopropyl)-l,4-diaminobutane, N,N'-bis-(4-aminobutyl)-l,4-diaminobutane, 4,4'-diaminodibutylamine (di-butylene triamine), N,N'-bis-(6-aminohexyl)-l,6-diaminohexane, and 6,6'-diaminodihexyl-amine (bis- hexamethylene triamine).

The acids A4 are fatty acids having one carboxyl group, and from six to thirty carbon atoms, preferably from eight to twenty-four carbon atoms. They are either saturated or singly or multiply unsaturated, and may also be used as mixtures, particularly in the form of naturally occurring mixtures as obtained by processsing of fatty oils and fats. Preferred fatty acids include stearic acid, palmitic acid, oleic acid, linoleic acid, linolenic acid, arachidonic acid, behenic acid, erucic acid, and ricinoleic acid, and among the mixtures, linseed oil fatty acid, soy bean oil fatty acid, coconut oil fatty acid, rapeseed oil fatty acid, and tall oil fatty acid.

In a preferred embodiment, an amount corresponding to a mass of preferably not more than 60 % of the mass of the fatty acids A4, of dicarboxylic acids A4' which are preferably aliphatic, such as glutaric acid, adipic acid, and cyclohexane dicarboxylic acid, can be added to the fatty acids A4. Preferred as acids A4' are dimeric fatty acids, which preferably have a mass fraction of aromatic constituents of not more than 20 %. The amines A2 are aliphatic linear, branched or cyclic secondary amines having preferably one secondary amino group, and from three to twenty carbon atoms, preferably from four to fourteen carbon atoms. They may also carry further substituents that can be non-functional, such as alkoxy groups, or can be functional such as hydroxyl groups or thiol groups. Among the preferred amines are di-n-butylamine, diethanolamine, and bis-2-hydroxypropylamine. Mixtures of these can also be used.

The amines A3 are aliphatic linear, branched or cyclic amines having one tertiary, and at least one primary amino group, and from four to twenty carbon atoms. Preferred amines are N,N- dimethylaminoethylamine, Ν,Ν-diethylaminoethylamine, N,N-dimethylaminopropyl-amine-3, N,N-diethylaminopropylamine-3, N-(2-aminethyl)-piperidine, and N,N'-bis(2-aminoethyl)- piperazine. Mixtures of these amines can also be used. The phenolic compounds A5 having from six to twenty carbon atoms and at least two phenolic hydroxyl groups are preferably dihydroxy aromatic compounds such as resorcinol, hydroquinone, dihydroxydiphenyl, dihydroxydiphenyl sulphone, bisphenol A, bisphenol F, and may optionally be substituted by alkyl or alkoxy groups such as methyl or methoxy groups, halogen groups, or trifluoromethyl groups. If phenolic compounds having three or more phenolic hydroxyl groups are used in mixture with dihydroxy aromatics, the amount of higher functional compounds should be limited to not more than 10 % of the mass of all such phenolic compounds, or compensated by addition of monofunctional phenolic compounds to limit the degree of branching in the resultant polymeric adduct EA. The amidoamines A41 are reaction products of the fatty acids A4 as defined supra, and of amines Al which are also defined supra, which have at least one amide group, and at least one amino group which has not been converted to an amide group. Usually, in an amine having both primary and secondary amino groups, and with a stoichiometry that provides one mole of fatty acid per one mole of primary amino groups, the main reaction product is an amidoamine with amide groups stemming from the primary amino groups, and with unreacted secondary amino groups. In the preferred case of using an amine Al which has two primary amino groups, and at least one secondary amino group, amidoamines A41 are formed that have two amide groups, and at least one secondary amino group. In a preferred embodi-ment, the amidoamines A41 are made by reaction of fats or fatty oils which are substantially triglycerides of fatty acids A4, or of mixtures of two or more different fatty acids A4.

Any water-soluble bismuth salt or bismuth chelate complex B can be used in the context of this invention. Preferred salts are bismuth salts having an anion derived from an organic acid, which may be a carboxylic, sulphonic, or phosphorus-based acid. Particularly preferred are bismuth hydroxycarboxylates, such as salts of organic hydroxy acids having at least one carboxylic group and at least one hydroxyl group, such as the salts of glycolic acid, lactic acid, 2- or 3-hydroxybutyric acid, 3-hydroxyisobutyric acid, 2,2-bis-hydroxymethyl propionic acid, 2,2-bis-hydroxymethyl butyric acid, malic acid, and tartaric acid. If bismuth salts of inorganic acids, such as nitric acid, or bismuth salts of an organic acid such as methanesulphonic acid that do not have hydroxyl groups or keto groups or amino groups are used, it has proven advantageous to add a chelate former such as a mercaptocarboxylic acid, e. g., dimercapto- succinic acid, hydroxycarboylic acids as mentioned supra, and particularly preferred, aminopoly carboxylic acids and their salts, notably iminodiacetate, nitrilotriacetate, ethylenediamine tetraacetate, diethylenetriamine pentaacetate, 2-hydroxy-ethyliminodiacetate, and pyridine dicarboxylate, etc. A salt or chelate is regarded as "water-soluble" in the context of this invention if a saturated salt solution at 23 °C has a mass fraction of dissolved bismuth salt or bismuth chelate complex in the solution of at least 0.05 g / 100 g.

The process to form the chain extended epoxy-amine adduct by reaction, in the aqueous phase, with the epoxide component E3 and quaternisation of tertiary amino groups present in the reaction mixture is generally conducted at a temperature of from 40 °C to not more than 105 °C, and under thorough stirring to ensure temperature control. Chain extension of the epoxy-amine adduct in the last step is preferably made, according to the process of the present invention, in the aqueously dispersed phase in order to be able to cope with the high resin viscosity.

In a preferred embodiment, in step a of the process, the mixture Ml is prepared from an amidoamine A41, an amine A2, and an amine A3. In a further preferred embodiment, step c of the process is executed, and amines A2 and A3 and a phenolic compound A5 are added to the mixture of preceding step a, Ml, or to the mixture of preceding step b, M2, to yield a mixture M3.

It is also preferred to use more than one of the above preferred selections together in the process.

In a particularly preferred embodiment of the process, an amidoamine A41 is made in a separate step from an amine Al and a fatty acid A4, where preferably, the amine Al has one secondary amino group and two primary amino groups, such as diethylene triamine, dibutylene triamine, and bis-hexamethylene triamine, and the fatty acid A4 preferably has an iodine number of from 120 cg/g to 195 cg/g. The amidoamine A41 is made, in a further preferred embodiment, by reacting an oil or fat which is a triglyceride of a fatty acid A4, or a mixture of two or more different fatty acids A4, with an amine Al. Depending on the stoichiometry, mixtures of diglycerides and monoglycerides, and glycerol, are concurrently formed in this reaction.

It is also preferred to prepare a mixture comprising the amidoamine A41, a further fatty acid A4 which is preferably unsaturated, and has an iodine number of from 100 cg/g to 150 cg/g, and a further amine Al, and to react this mixture with a monoepoxide El, preferably a glycidyl ester of an aliphatic branched monocarboxylic acid having from four to twelve carbon atoms, to reduce the functionality of the mixture. After addition of a phenolic compound A5, preferably, bisphenol A or bisphenol F, an amine A2 which is preferably diethanolamine, and an amine A3 which is preferably diethylaminopropylamine or dimethylaminopropylamine, the inert solvent and an epoxide resin E2 are added and reacted until the epoxide groups were consumed. This resin is then dispersed in water wherein a bismuth salt or chelate complex had been dissolved before. After heating this dispersion to a temperature of preferably between 60 °C and 90 °C, a second epoxide compound E3 is added, where preferably the amount n(EP;E3) of epoxide groups in this epoxide compound E3 divided by the amount n(EP;E2) of epoxide groups of the epoxide resin E2 is from 0.05 mol/mol to 0.35 mol/mol, particularly preferred from 0.1 mol/mol to 0.30 mol/mol. The urethane additive U has at least one, preferably two or more, urethane groups in its molecule, and has optionally functional groups which are preferably hydroxyl groups and carboxylic acid groups, and is made by reaction of

(a) at least one at least difunctional organic isocyanate Ul, at least one at least difunctional aliphatic alcohol U2, and optionally at least one monohydric aliphatic alcohol U3 to form a hydroxyurethane U123, or

(b) at least one aliphatic diamine U5 with a cyclic aliphatic carbonate U4 to form a dihydroxyurethane U54 or a mixture thereof with unreacted diamine U5, which is then reacted with diisocyanate Ul to form a hydroxyurethane U541 optionally also comprising a hydroxyurea-urethane U51, or

(c) at least one oligomeric or polymeric aliphatic diol or triol U6 with at least one at least difunctional organic isocyanate Ul to form a hydroxyurethane U61, and reacting this with a cyclic acid anhydride U7 to convert a part or all of the hydroxyl groups by formation of an ester group, and liberation of an acid group, to form an acid-functional urethane U617.

If U is a hydroxy-functional urethane additive, it is preferred to have a specific amount of urethane groups n(-0-CO-NH)/m(U) in the urethane additive of at least 2.5 mol/kg, preferably at least 3 mol/kg, and particularly preferred, at least 3.5 mol/kg. Lower values such as down to 1.0 mol/kg can be used in the case of acid-functional urethane additives that do not have hydroxyl groups. The urethane additives U are preferably dissolved in alcohol or etheralcohol solvents. The urethane additive U is preferably added to the intermediate I before step f. The components used in the synthesis of the urethane additives U are preferably the following:

Ul is an at least difunctional organic isocyanate of formula X ¹ (NCO) _m where m is 2 or more, and X ¹ is an aromatic or aliphatic or araliphatic group having up to fifteen carbon atoms, and Ul is preferably selected from the group consisting of 1,6-hexanediisocyanate, isophorone diisocyanate, bis-4-isocyanatophenylmethane, the 2,4- and 2,6 isomers of toluene diisocyanate, and tetramethyl-l,3-xylylene diisocyanate. U2 is an at least difunctional aliphatic alcohol of formula X ² (OH)n where n is 2 or more, and X ² is an aliphatic linear or branched group having up to sixty carbon atoms where one or more carbon atoms are optionally replaced by an oxygen group -0-, or an ester group -CO-0-, where such oxygen or ester groups are separated by at least two neighbouring carbon atoms, and U2 is preferably selected from the group consisting of ethylene glycol, 1,2- and 1,3-propanediol, 1,4- butanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 2,2,4-trimethyl-l,3-pentanediol, and glycerol, trimethylolethane, trimethylolpropane, diglycerol, ditrimethylolethane, ditrimethylol- propane, erythritol and pentaerythritol, dierythritol and dipentaerythritol. It is also possible to use oligomeric or polymeric hydroxy-functional compounds U2 having at least four carbon atoms such as oligomeric or polymeric ethyleneglycol, oligomeric or polymeric propylene- glycol, and oligomeric or polymeric caprolactonediol which is preferably made from caprolactone and any of the di- or multifunctional alcohols mentioned herein. U2 can also have further reactive groups such as carboxyl groups, particularly preferred as such are dimethylolpropionic acid and dimethylolbutanoic acid. U3 is a monohydric aliphatic linear or branched or cyclic alcohol having from one to twenty carbon atoms and one hydroxyl group; preferred alcohols are methanol, ethanol, propanol, butanol, 2-ethylhexanol, decylalcohol, tridecylalcohol, and stearylalcohol. U4 is a cyclic aliphatic carbonate having at least three carbon atoms and at least one cyclic carbonate group, and is preferably ethylenecarbonate, propylenecarbonate (4-methyl-l,3- dioxolan-2-one), 1,2-butylenecarbonate, or 2,3-butylenecarbonate. U5 is an aliphatic diamine having two primary amino groups, and at least six carbon atoms, and may be a linear, branched or cyclic aliphatic amine or an aliphatic-aromatic amine having amino groups bound to aliphatic carbon atoms. Useful diamines are 1,2-diaminoethane, 1,3- diaminopropane, 1,4-diaminobutane and 1,6-diaminohexane, 1,2- and 1,4-diaminocyclo-hexane, isophoronediamine, xylylenediamine, and diamines derived from oligomeric and polymeric polyoxyalkylenes having from two to four carbon atoms in the alkylene groups, such as alpha,omega-diamino-polyoxyethylene and alpha,omega-diamino-polyoxypropylene.

U6 is an oligomeric or polymeric aliphatic dihydroxy compound or an oligomeric or polymeric aliphatic trihydroxy compound, which is preferably obtained by reaction of linear or branched aliphatic diols or triols preferably selected from the group consisting of ethyleneglycol, 1,2- dihydroxypropane, glycerol, trimethylolethane, and trimethylolpropane with ethyleneoxide or propyleneoxide or mixtures of these to form a hydroxyfunctional polyether, or by reaction of linear or branched aliphatic diols or triols preferably selected from the group consisting of ethyleneglycol, 1,2-dihydroxypropane, glycerol, trimethylolethane, and trimethylolpropane with lactones such as butyrolactone, valerolactone, caprolactone, and lactide to form a hydroxyfunctional polyester. For the purpose of this invention, an oligomeric compound comprises up to ten repeating units, and is referred to as polymer if it has more than ten repeating units. U7 is a cyclic acid anhydride derived from a dicarboxylic acid having at least four carbon atoms, and is preferably selected from the group consisting of maleic anhydride, phthalic acid anhydride, tetrahydrophthalic acid anhydride, and hexahydrophthalic acid anhydride. The aqueous dispersions thus obtained have generally a mass fraction of solids of between 20 % and 60 %. The epoxy-amine adducts EA have preferably an amine number of from 40 mg/g to 150 mg/g, and hydroxyl numbers of from 30 mg/g to 150 mg/g, in each case in relation to the mass of solid resin. Their Staudinger index is preferably from 30 cm ³ /g to 100 cm ³ /g, particularly preferably from 40 cm ³ /g to 90 cm ³ /g, as measured on solutions in N-methyl pyrrolidone at room temperature (23 °C). A value of 60 cm ³ /g corresponds to a weight-average molar mass of 40 kg/mol, as measured by gel permeation chromatography using polystyrene standards in the usual way. The quantity formerly referred to as "limiting viscosity number", called "Staudinger index" / _g in accordance with DIN 1342, part 2.4, is the limiting value of the Staudinger function Jv measured with decreasing concentration and shear stress, wherein Jv is the ratio of the relative change in viscosity - 1, divided by the mass concentration ¾ = ni / V of the solute B (mass TU of the solute in a volume V of the solution), given by Jv = (η _τ - 1) / ¾ . - 1 stands for the relative change in dynamic viscosity, according to - 1 = (η - ψ) I ψ. The relative viscosity is the ratio of the dynamic viscosity η of the solution under consideration and the dynamic viscosity of the pure solvent. The physical significance of the Staudinger index is that of a specific hydrodynamic volume of the solvated polymer coil at infinite dilution and at rest. The unit conventionally used for / is "cm ³ /g"; formerly also "dL/g".

The aqueous dispersion of the present invention can be used to formulate coating compositions by adding usual additives such as coalescing agents, wetting agents, optionally pigments, and rheology additives. These coating compositions can be applied by any process, particularly, by brushing, roller-coating, curtain-coating, spraying, or dipping, on any substrate, such as concrete, plaster, mortar or stone, or wood, paper, cardboard, leather, or rubber, or metals, glasses, thermoplastic materials, duromeric materials, and elastomeric materials. A particularly useful method of application is electrophoretic deposition on electrically conductive substrates such as base metals. For this purpose, the dispersions are usually diluted with further water to a mass fraction of solids of about 15 %, and are deposited from a bath containing this dispersion onto metal substrates which serve as cathodes. The coating film applied by any of the techniques mentioned hereinbefore is dried at a temperature of from ambient temperature (25 °C) to 160 °C, preferably from 50 °C to 130 °C. As the film is physically drying, there is no need to add a chemical crosslinker such as blocked isocyanates. Consequently, there is no need to split off a blocking agent which needs higher temperature, and thus, more energy, and leads to air pollution by the cleavage products of the blocked isocyanates. If cleavage products from the blocked isocyanates are trapped in the coating film and cannot escape due to premature solidification of the surface of the coating film, they may lead to formation of bubbles in the dried coating film.

The invention therefore further relates to a process to coat substrates, preferably metal or metal containing substrates, comprising dipping the substrates in a bath comprising the cationic water-dilutable binders of the present invention and preferably containing a mass fraction of less than 1 % of crosslinker, by cathodic electrodeposition, followed by removing the substrate from the bath, and subjecting the coated substrate to a drying step at a temperature of between 20 °C and 130 °C for a time between five minutes and twenty-four hours. The drying step is preferably done at a temperature of from 60 °C to 120 °C, most preferably from 65 °C to 100 °C, for a time between five minutes and two hours. Crosslinker as used in this description is a resin or a chemical compound that has at least two reactive groups which can react with functional groups in the epoxy amino adduct EA for to form a crosslinked network. The bath is preferably substantially free of any crosslinker, more specifically of isocyanate or blocked isocyanate crosslinkers. After the drying step a coating film is formed on the substrate and this coating film does not need further heating at a temperature of higher than 120 °C. It has been found that good surface appearance and high corrosion resistance can already be obtained with coating film thickness of about 0.010 mm. The coated substrate can then be used as such or can be coated by one or more further coating layers, such as filler and surfacer coatings, and pigmented or unpigmented topcoats.

The cationic binders and the process according to the invention permit to obtain good quality coatings with a very good corrosion resistance, even in severe conditions. The binders and process according to the invention permit a substantial energy saving over the current CED processes in that it is not needed to heat coated substrates to a high temperature to activate the crosslinker. Moreover the collection and removal of blocking agents usually used in combination with commonly used CED resins is no longer necessary.

It has further been found that the cationic binders according to the invention permit to obtain good adhesion between primer layers made with the cationic binder of the present invention, and topcoats applied to substrates having a primer layer from the said cationic binder. Adhesion, and thereby also corrosion resistance, is particularly good for a combination of these primer layers and top coats made from binders which are crosslinked by Michael addition chemistry, these binders comprising a component having at least two activated carbon-carbon double bonds (Michael acceptor groups) and a component having at least two acidic C-H groups (Michael donor groups), catalysed with a base. The invention is further illustrated by the following examples. In these examples as well as in the whole specification, all quantities measured in "%" relate to mass fractions or mass ratios, as measured in cg/g or g/hg, except where specifically denoted otherwise.

The acid value or acid number WAC of a sample is defined, according to DIN EN ISO 3682 (DIN 53 402), as the ratio WJKOH / r of that mass WJKOH of potassium hydroxide which is needed to neutralise the sample under examination, and the mass rm of this sample, or the mass of the solids in the sample in the case of a solution or dispersion; its customary unit is "mg/g". The hydroxyl value or hydroxyl number WOH of a sample is defined according to DIN EN ISO 4629 (DIN 53 240) as the ratio WJKOH / r of the mass of potassium hydroxide WJKOH having the same number of hydroxyl groups as the sample, and the mass rm of that sample (mass of solids in the sample for solutions or dispersions); the customary unit is "mg/g".

The amine value or amine number WAm of a sample is defined according to DIN 53 176 as the ratio THKOH I rm of the mass of potassium hydroxide WJKOH that needs the same amount of an acid for neutralisation as the sample, and the mass rm of that sample (mass of solids in the sample for solutions or dispersions); the customary unit is "mg/g".

The following abbreviations are used in the examples:

EC Ethylenecarbonate M = 88 g/mol

TDI Toluenediisocyanate (mixture of isomers) M = 174 g/mol

MDI Diphenylmethane-4,4'-diisocyanate M = 250 g/mol

HDI 1,6-Hexamethylenediisocyanate M = 168 g/mol

IPDI Isophoronediisocyanate M = 222 g/mol

PC Propylenecarbonate M = 102 g/mol

PPGD Polypropylenegly c ol-diamine M = 230 g/mol (®Jeff amine D-230, Huntsman)

XDA m-Xylylenediamine M = 136 g/mol

BG Butylglycol M = 118 g/mol

BDG Butyldiglycol M = 162 g/mol

BD 1,4-Butanediol M = 90 g/mol

CD Caprolactonediol M = 550 g/mol (®Capa 2054, Perstorp)

PE Polyestertriol 3050 M = 540 g/mol (®Capa 3050, Perstorp)

PD 1,2-Propanediol M = 76 g/mol

TMP Trimethylolpropane M = 134 g/mol

HG Hexyleneglycol (2-Methyl-2,4-pentanediol) M = 118 g/mol

PPG Polypropylenegly col 400 M = 400 g/mol

THPSA Tetrahydrophthalic anhydride M = 152 g/mol DMPS Dimethylolpropionic acid M = 134 g/mol

M is the rounded molar mass of these chemicals. Example 1 Bismuth salt preparation

362 g (2.7 mol) of dimethylolpropionic acid and 675 g of deionised water were charged into a 4 1 glass flask equipped with a stirrer and a reflux-condenser. The solution was heated to 75 °C. Ill g (0.24 mol) of B12O3 were added under good stirring in small portions within sixty minutes. Then the mixture was allowed to stir for further sixty minutes at this temperature, whereby a greyish-white, slightly opaque solution was obtained (no more undissolved yellow parts of B12O3 to be seen). Finally, 1282 g of deionised water were added and the solution was cooled to room temperature. The obtained bismuth salt preparation has a mass fraction of bismuth of 4.1 %. Example 2 Amino-functional fatty acid amide FA

146 g (1.0 mol) of triethylenetetramine and 1320 g(1.5 mol) of linseed oil were charged into a 3 1 three-necked vessel equipped with a thermocouple, a stirrer and a reflux condenser and heated to 95 °C under stirring. This temperature was held for approximately six hours until at least 95 % of the primary amino groups had reacted, as monitored by the decrease in the amine number measured, starting from 153 mg/g. Approximately 1460 g of a mixture of the amide and glycerides were obtained, which mixture had an amine number of 79 mg/g.

Example 3.1 Preparation of the urethane component U01

1463 g (12.4 mol; n(OH) = 24.8 mol) of HG, 162 g (0.3 mol; n(OH) = 0.9 mol) of PE and 292 g of BDG (1.8 mol; n(OH) = 1.8 mol) were charged into a glass vessel and heated to 80 °C. 2266 g (9.1 mol; n(NCO) = 18.2 mol) of MDI were added in portions within one hour under cooling, keeping the temperature in the range from 80 °C to 85 °C. When the whole amount of MDI had been added, the reaction mass was kept for one further hour at 80 °C, in order to allow the complete consumption of the isocyanate groups. Finally, the reaction product was diluted to a mass fraction of 80 % with methoxypropanol.

Further urethane components (U02 to U05, U07; examples 3.2 to 3.5; 3.7) had been produced, following this procedure. Kind and mass of the reactants (educts) are compiled in Table 1.

Table 1 Urethane components

FG stands for "functional group", with the kind indicated as chemical formula, and its amount of substance stated in the SI unit "mol". n(-O-CO-NH-) / m(U) is the specific amount of substance of urethane groups -O-CO-NH- in the urethane reaction product U. Example 3.6 Preparation of the urethane component U06

230 g (1.0 mol; n(NH2) = 2 mol) of PPGD and 163 g (1.6 mol) of PC were charged into a glass vessel and heated within one hour to 110 °C. Temperature was kept for two hours at 110 °C under stirring and occasional cooling (slight exothermy) until an amine value of 60 mg/g was obtained. The reaction mixture was then cooled to 80 °C and 34 g (0.2 mol) of HDI were added within fifteen minutes, whereby the temperature had risen to 90 °C by exothermy. Temperature was kept at 90 °C for two hours, in order to consume all amino groups (amine value < 1 mg/g). Finally, the reaction product was diluted to a mass fraction of 80 % with methoxypropanol. A further urethane component U08 had been produced, following this procedure (Example 3.8). Example 3.9 Preparation of the urethane component U09

800 g (2.0 mol; n(OH) = 4.0 mol) of PPG were charged into a glass vessel and heated to 60 °C. 250 g (1.0 mol, n(NCO) = 2.0 mol) of MDI were added in portions within one hour under cooling, keeping the temperature in the range from 80 °C to 85 °C. When the whole amount of MDI had been added, the reaction mass was kept for one further hour at 80 °C, in order to allow the complete consumption of the isocyanate groups. 304 g (2.0 mol) of THPSA were added in portions within 15 minutes, then the temperature was increased to 160 °C in one hour. This temperature was maintained for two hours in order to react all anhydride groups (acid value of the reaction product: 83 mg/g). Finally, the reaction product was diluted to a mass fraction of 80 % with methoxypropanol.

Example 3.10 Preparation of the urethane component U10

522 g (3.0 mol; n(NCO) = 6.0 mol) of TDI were charged into a glass vessel and heated to 30 °C. 236 g (2.0 mol; n(OH) = 2.0 mol) of BG were added continuously within two hours under cooling (strong exothermy), while keeping the temperature below 50 °C. After the whole amount of BG had been added, the reaction mass was kept for one further hour at 50 °C, in order to complete the reaction with BG (mass fraction of NCO groups in the reaction mixture: 22 %). Afterwards the reaction mixture was diluted with methoxypropylacetate to a mass fraction of 80 %. The temperature was then adjusted to 90 °C and 268 g (2.0 mol) of DMPS were added in small portions within two hours. Temperature was allowed to rise to 100 °C by exothermy, applying temporary cooling to keep. After the DMPS addition had been finished, temperature was kept for one hour to complete the reaction of all isocyanate groups (residual mass fraction of NCO groups in the reaction mixture < 0,1 %). The reaction product was finally diluted to a mass fraction of 80 % with methoxypropanol.

Example 4.1 : Preparation of the urethane containing, epoxide-amine adduct dispersion (EA1)

1466 g (1.0 mol) of the amino-functional fatty acid amide FA of example 2 and 561 g (2.0 mol) of linseed oil fatty acid were charged into a three necked vessel equipped with a stirrer and a reflux condenser and heated to 80 °C. Under stirring and in this sequence, 730 g (3.2 mol) of bisphenol A, 315 g (0.5 mol) of a dimeric fatty acid (®Pripol 1017, Croda, Mw = 630 g/mol), 210 g (2.0 mol) of diethanolamine and 184 g (1.8 mol) of dimethylaminopropylamine were added. After one hour, when the reaction mixture was a homogenous melt, 4530 g (11.9 mol) of a liquid diepoxide based on bisphenol A (Mw = 380 g/mol) were added over ninety minutes while the temperature rose due to exothermy up to 160 °C. The reaction mixture was held at 160 X2 for one further hour until no more free epoxide groups in the modified epoxide amine adduct EA1 could be detected. Finally, 800 g of the urethane component U01 were added and the mixture was allowed to stir for thirty minutes. A dilution vessel was prepared into which 9 kg of deionised water, 640 g of lactic acid (aqueous solution with a mass fraction of lactic acid of 50 %), and 1732 g of the bismuth salt preparation BP of example 1 were charged. The resin from the reaction vessel was poured into the pre-charged dilution vessel under stirring within thirty minutes. The temperature of the mixture was adjusted to 70 °C, and the mixture was then stirred at this temperature for one hour. By sequential addition of portions of water, the mixture was further diluted to a mass fraction of 43 %. The aqueous dispersion thus obtained was then heated to 80 °C whereupon a second portion of 400 g (1.05 mol) of a liquid diepoxide based on bisphenol A (Mw = 380 g/mol) was added, and the resulting mixture was stirred for two further hours at 80 °C. By the addition of further water and under cooling to room temperature, the mixture was diluted to a dispersion having a mass fraction of solids of 40 %, with a bismuth content of 0.3 % based on the mass of the dispersion.

Examples 4.2 to 4.15

The procedure of Example 4.1 was repeated, replacing the 800 g of solution of urethane U01 which corresponds to a mass of solid urethane U01 of 640 g by solutions of urethanes U02 to U10 (examples 4.2 to 4.10), by a mixture of solutions of urethanes U02 and U09 with a mass ratio of solids of 550 g to 250 g (example 4.11), by a mixture of solutions of urethanes U03 and U10 with a mass ratio of solids of 750 g to 150 g (example 4.12), by 850 g of a hydroxy-functional ethoxylate of bisphenol A "CI" with n(OE) / n(BPA) of 6 mol : 1 mol, where n(OE) is the amount of substance of oxyethylene moieties -O-CH2-CH2-, and n(BPA) is the amount of substance of 2,2-bis(4-oxyphenyl)propane moieties in the ethoxylate CI (comparative example 4.13), and by 850 g of a hydroxy-functional polyester C2 made from 1,4-dihydroxy-butane and adipic acid with a mass-average molar mass of 2200 g/mol, as determined by size-exclusion chromatography using polystyrene standards (comparative example 4.14). A non-modified epoxy-amine adduct binder as used in example 4.1 without any additive was used as further comparison (comparative example 4.15). The variable constituents of the coating compositions prepared as explained in Examples 4.1 to 4.15, and the total mass of solids, as well as the glass transition temperature measured on a film prepared therefrom (dried for seven days at 23 °C and 50 % of relative humidity, heating rate of 10 K/min, second heating cycle) is summarised in table 2. Table 2 Variable Constituents of Coating Composition and Data

ms is the total mass of solids in the coating composition,

m(U) is the mass of the additive (solid urethane additive Ul to U10, comparative additive

CI or C2, not including solvent)

n(-O-CO-NH-) is the amount of substance of urethane groups contributed by the additives # comparative example

The following results have been found when coating untreated (blank) and zinc-phosphated steel. Coating was performed by electrodeposition of a coating film having a dry thickness of 0.010 mm after drying for ten minutes at 80 °C was obtained. Tests were made Salt Spray Test (for Scribe and Edge, values in mm) according to DIN EN ISO 9227, and surface quality was inspected visually, with a ranking from 1 (no defects) to 5 (whole surface shows marked defects): Table 3 Data for Coating Films on Steel Substrates

1 ... 2: value lies between 1 and 2

* surface is sticky

It can be seen from these results that the admixture of a urethane additive has a beneficial effect on corrosion resistance and surface quality. No decisive influence has been found whether a polyester or a polyether structure is comprised in the urethane. Slightly better values, however, have been found when a branched polyester triol (PE) was used as constituent compound in the urethane additive. The presence of urethane groups has a markedly stronger effect on the improvement of both corrosion resistance and surface quality, as can be seen from the comparison with the comparative additives CI and C2 which are hydroxy-functional polyester or polyether.

Inspection of the coated steel sheets, both from blank steel and Zn-phosphated steel, where binders according to the invention were used has revealed that the surface coated with paints prepared from these does not show any swirls or micro-pinholes (ranking of less than 3 in surface quality), which defects have, however, been found in paints of identical composition where no urethane additives were present (ranking of 3 or higher).

Example 5 Intercoat Adhesion

Adhesion of further topcoat paint film layers on dried cold rolled steel substrates (Gardobond OC 6800) coated with the paints of example 4 was tested, with a dry layer thickness of 60 μιη (0.06 mm). For this purpose, pigmented topcoat liquid paints 5.1 to 5.4 and 5.6 as well as a powder clear coat 5.5 were prepared: Example 5.1 one-pack pigmented topcoat based on a water-borne acrylic binder resin

The following components were added to a vessel in the order shown, mixed and dispersed for about thirty minutes in a bead mill: 25.10 g of an aqueous styrene acrylic copolymer dispersion (Allnex, Viacryl® SC6807w/42WA), having a hydroxyl value WOH of approx. 75 mg/g, 21.30 g of a rutile type titanium dioxide pigment (Kronos International Inc., Kronos® 2310), 0.90 g of a wetting and dispersing agent (Byk Additives and Instruments, DISPERBYK® 190; acidic high molar mass block copolymer), 1.10 g of a non-ionic polymeric pigment dispersing agent (eChem Ltd, eCheml459; polyoxyalkylene glycol ester), 0.10 g of a silicone based slip and levelling agent (Byk Additives and Instruments, BYK® 302; polyether-modified polydimethylsiloxane), 4.00 g of 2-(2-butoxyethoxy)ethanol, and 4.00 g of deionised water.

This pigmented mixture was then completed with a further mixture made by addition in the order shown, and homogenisation of the following ingredients: 22.50 g of the aqueous styrene acrylic copolymer dispersion mentioned supra, 7.30 g of a methylated high-imino melamine- formaldehyde crosslinker (Allnex, Cymel® 327; solution in isobutanol, mass fraction of resin ca. 90 %), 0.90 g of 2-(2-butoxyethoxy)ethanol, 0.90 g of n-dodecane, 2.70 g of 2,2,4-trimethyl-l,3- pentanediol monoisobutyrate (Eastman Chemical, Texanol®), 1.70 g of dipropyleneglycol dimethylether (Dow Chemical, Proglyde® DMM), and 7.50 g of deionised water.

The mixture was homogenised and diluted with further deionised water to an efflux time (measured in a 4 mm cup according to DIN 53 211, at 23 °C) of 30 s before application. Example 5.2 two-pack pigmented topcoat based on a water-borne acrylic binder resin

The following components were added to a vessel in the order shown, mixed and dispersed for about thirty minutes in a bead mill: 56.6 g of an aqueous styrene acrylic copolymer dispersion, having a hydroxyl value WOH of ca. 135 mg/g (Allnex, Macrynal® SM 6810w/42WA), 2.05 g of a wetting agent based on alkylolammonium salt of a polycarboxylic acid copolymer (Byk Additives and Instruments, DISPERBYK®), 34.03 g of a rutile type titanium dioxide pigment (Kronos International Inc., Kronos® 2310), 0.07 g of a carbon black pigment (Evonik Industries, Printex® 201), 0.36 g of a polyacrylate levelling agent (Byk Additives and Instruments, BYK® 381), 3.21 g of deionised water, 1.83 g of a mixture of mass fractions of 90 % of diethanolamine and 10 % of water, and further 1.67 g of deionised water.

This first mixture was mixed and homogenised, before application, with a crosslinker mixture made by addition in the order shown, and homogenisation of the following ingredients: 21.10 g of a mixture of 1,6-diisocyanatohexane and 5-isocyanato-l-(isocyanatomethyl)-l,3,3-trimethyl- cyclohexane, dissolved in n-butylacetate, having a mass fraction of solids of ca. 85 %, and a mass fraction zt>(NCO, solution) of isocyanate groups in the solution of ca. 15.8 %(Vencorex Holding; Easaqua® XD 401), and 8.06 g of a mixture of alkylated benzenes, having a boiling temperature range at 0.1 MPa from 150 °C to 180 °C (DHC Solvent Chemie, Solvent Naphtha 150/180).

Immediately before application of the combined mixtures, the homogenised mixture was diluted with further deionised water to an efflux time (4 mm cup, DIN 53 211, at 23 °C) of 30 s.

Example 5.3 one-pack air drying topcoat based on a water-borne alkyd resin

The following components were added to a vessel in the order shown, mixed and dispersed for about sixty minutes with glass beads in a bead mill:

66.00 g of an aqueous acrylate-modified short-oil alkyd resin dispersion having a hydroxyl value ZVOH of ca. 135 mg/g (Allnex; Resydrol® AY 6150w/45WA), 0.30 g of an aqueous solution of ammonia with a mass fraction of solute of 25 %, 0.10 g of a mixture of mass fractions of 90 % of 2-amino-2-methyl-l-propanol and 10 % of water (Angus Chemical Company; AMP-90®), 0.75 g of a cobalt combination siccative (Borchers GmbH, Octa-Soligen® 123 aqua), 0.75 g of deionised water, (the combination siccative was diluted immediately before addition with the same mass of water), 0.30 g of an antiskinning agent (Borchers GmbH, Ascinin® 0445; solution of a mass fraction of about 10 % of Ν,Ν-diethylhydroxylamine in 1,2-dihydroxypropane), 23.20 g of a rutile type titanium dioxide pigment (Kronos International Inc., Kronos® 2310), 0.50 g of a wetting and anti-settling agent (Borchers GmbH, Borchi® Gen TS; solution of ca. 17.5 g of ethoxylated isononylphenol, and ca. 17.5 g of Ν,Ν-bishydroxyethylcocoamide in 65 g of a mixed solvent comprising approx. 20 g of propylene carbonate and approx. 45 g of 2- butoxy-ethanol), 0.80 g of a non-ionic polymeric pigment dispersing agent (polyoxyalkylene glycol ester; eChem Ltd, eChem 1459), 0.40 g of a deaerator (Dow Corning, Dow Corning 62 additive; aqueous emulsion of a mass fraction of approx. 6.5 % of a reaction product of silica powder with functional oligomeric dimethylsiloxane, further comprising approx. 5.4 % of a mixture of ethoxylated branched aliphatic Cn- to Cis- alcohols), and 0.40 g of a defoamer (Byk Additives and Instruments, BYK® 093; mixture of polysiloxanes and hydrophobic solids in poly glycol).

To this pigmented topcoat mixture, a mixture of 5.65 g of deionised water and 0.15 g of an associative polyurethane rheology modifier (BASF SE, Rheovis® PU1291; aqueous solution of mass fractions of approx. 25 % of a polyurethane and approx. 20 % of ethoxylated octanol) was then added under stirring. The resulting coating mixture was set to an efflux time of 30 s from a 4 mm cup at 23 °C (DIN 53 211) by adding deionised water, applied by spraying onto coated panels, and left to dry at room temperature for fourteen days.

Example 5.4 two-pack solvent-borne polyurethane topcoat

The following components of part A as detailed here under were mixed in mentioned order and dispersed for approx. thirty minutes on a bead mill:

45.4 g of a solution of an acrylate styrene copolymer (mass fraction of polymer of 75 %, dissolved in butylacetate, having a mass fraction of hydroxyl groups in the solid polymer of 4.2 % (Allnex, Macrynal® SM 2810/75BAC), 2.05 g of a dispersing agent (Byk Additives and Instruments, DISPERBYK® 111; phosphoric acid polyester copolymer with acid groups having an acid value of approx. 129 mg/g), 40.7 g of a rutile type titanium dioxide pigment (Kronos International Inc., Kronos® 2090), 0.4 of an antisettling agent (Byk Additives and Instruments, BYK® 7410 ET; solution of a mass fraction of 40 % of a modified urea in an etheramide solvent), 3.7 g each of xylene, methoxypropylacetate, and butylacetate, and 0.2 g of a silicone based levelling agent (Byk Additives and Instruments, BYK® 320; solution of a mass fraction of 52 % of a polyether-modified polymethylalkyl siloxane in a mixture of white spirit and methoxypropylacetate in a mass ratio of 9:1).

Before application the components of Part B were added in the mentioned order, the resulting mixture was homogenised, and adjusted to an efflux time of approximately 30 s (according to DIN 53 211, at 23 °C, from a 4 mm cup) by adding a mixture of butylacetate, solvent naphtha (boiling temperature range from 150 °C to 180 °C) and xylene in a mass ratio of 60:15:25. After application, the topcoat was dried for thirty minutes at 80 °C. Example 5.5 Unpigmented Powder Topcoat

A clear powder topcoat as detailed in EP 0 509 393 Al, example lc, was applied by electrostatic spray application at 60 kV onto the coated substrates, to form a clear coat layer having a film thickness of 60 μιτι (0.06 mm) after heating to 140 °C and curing for thirty minutes. Example 5.6 Topcoat based on malonate polyester resin crosslinked with tetrafunctional aery late

A pigmented topcoat based on Michael Addition crosslinking was prepared according to Example 17 of WO 2014/166 880 Al. A pigment dispersion was prepared by charging 125.28 g of a rutile titanium dioxide pigment (Kronos International Inc., Kronos® 2310), 3.77 g of a wetting and dispersing additive based on a block copolymer having aminic pigment affinic groups, with an amine value WAm of 10 mg/g, dissolved in a mixture of xylene, butylacetate, and methoxypropylacetate in a mass ratio of 3:1:1, to yield a solution having a mass fraction of solids of 45 % (Byk Additives and Instruments, DISPERBYK® 163), 59.62 g of ditrimethylolpropane tetraacrylate (Sartomer subsidiary of Arkema; Sartomer® SR 355), and 100 g of a malonate polyester resin having an acid value of 0.3 mg/g, a hydroxyl value of 20 mg/g, and a mass average molar mass of 3400 g/mol, measured on a THF solution via gel permeation chromatography, using a calibration with polystyrene samples. After milling in a bead mill with glass beads, for thirty minutes, further 8.51 g of ditrimethylolpropane tetraacrylate as above, 0.92 g of a mixture of a solution of (a) a mass fraction of 25 % of a polyester-modified polydimethylsiloxane in a mixture of xylene isomers and ethyl benzene in a mass ratio of about 3:1 (Byk Additives and Instruments, BYK® 310) and (b) a mass fraction of 25 % of a polyester- modified polymethylalkyl siloxane in a mixture of equal masses of methoxypropyl acetate and phenoxyethanol (Byk Additives and Instruments, BYK® 315N), 0.87 g of lH-l,2,3-benzotriazol, 0.31 g of succinimide, 14.69 g of n-propanol, and 13.50 g of ethanol were added to the pigmented mixture, and homogenised well. Finally, 17.71 g of a solution of an amount of substance of 0.125 mol of the potassium salt of lH-l,2,3-benzotriazol in 63 g of ethanol as basic catalyst were admixed, and the resulting paint was sprayed onto the coated plates within five minutes after addition of the basic catalyst solution. The painted slabs were dried for sixty minutes, and tested after 24 h rest at room temperature (23 °C).

Example 6 Salt Spray and Humidity Test

The coated panels of examples 5.1 to 5.6 were put in a salt spray chamber (DIN EN ISO 9227) and a humidity test chamber (ASTM D2247-02), each at room temperature (23 °C), for 1000 h exposure time. The test was passed if the delamination from scratch was 3 mm or less (salt spray chamber), and if the rating of blisters did not exceed a value of 1 for both number and size of blisters on a panel with a size of 10 x 20 cm ² (humidity chamber) after this exposure time. It was found that these results were reached with all top coat formulations tested, in combination with paints 4.1 to 4.12. Primer layers made with paints 4.13 to 4.15 in combination with topcoats 5.1 to 5.6 failed before 1000 h of exposure time were reached.