Field of the Invention

This invention relates to multi-layer coatings, coating compositions therefor, application thereof on substrates, and improvement of interlayer adhesion. Particularly, this invention relates to coating compositions based on epoxy resins which are preferably applied to substrates in the form of an aqueous dispersion, and are combined with an overcoat layer based on coating compositions which are cured by Michael addition chemistry.

Background of the Invention

Epoxy resin based coating compositions are used, i. a., as primer coatings, particularly on metal substrates and mineral substrates where corrosion resistance, mechanical and chemical stability are needed. Such epoxy resins have functional groups which are epoxides, particularly epoxides derived from glycidyl groups present in these resins. For corrosion resistant coatings, basic curing agents are preferably used which comprise Lewis bases, inorganic bases, organic compounds having primary amino groups, organic compounds having secondary amino groups, and organic compounds having tertiary amino groups, and organic amides.

Primer coatings made from epoxy resins are frequently combined with a topcoat made from a coating composition having a different curing chemistry. Such coating compositions for topcoats include those where the binder is based on a polyurethane, a polyurea, an epoxy resin, an alkyd resin, or an acrylic resin, with a suitable crosslinking agent. These topcoat coating resins can be used as a solution in organic solvents, preferably in the form of a high solids (with a mass fraction of solids of at least 60 %) solvent borne coating composition, or preferably, in the form of an aqueous dispersion. Recently, topcoats have been described made from coating compositions which are cured by Michael addition, where the Michael donor component is a C-H acidic compound, and the Michael acceptor is preferably a vinylogous carbonyl compound, under formation of bonds between carbon atoms. These coating compositions are usually solvent-borne, and have a low VOC (less than 250 g/L). See R. Brinkhuis et al., European Coatings Journal 2015, pages 34 to 40.

It has been found that the adhesion of topcoat coating films on an epoxy primer coating layer, particularly on metal substrates, needs improvement.

In a previously filed patent application, EP 17 204 542, lipophilic modification of an amine- based epoxy hardener as been described wherein the lipophilic modification has been made by including dimer fatty acids into the epoxy amine adduct. Epoxy primer coating layers using this hardener have shown improved intercoat adhesion between the epoxy primer layer and a topcoat based on a Michael addition curing system comprising malonate polyesters as Michael donor component, and multifunctional acryloyl compounds as Michael acceptors, as has been found in corrosion testing experiments.

Such lipophilic modification of the epoxy primer coating composition can be made by introducing lipophilic compounds into either or both of epoxy resin systems, and epoxy curing agents, the latter also referred to as "hardeners".

Intercoat adhesion between coating layers depends on the surface tension of the coating being applied and on the surface free energy of the substrate coating, the surface tension of the coating being applied must be lower than the surface free energy of the substrate coating to permit wetting. Several results found empirically have been reported, such as the presence of polar groups in both coatings which permits hydrogen bonding; or the presence of small amounts of amine groups in resins commonly lead to multi-layer coatings with superior intercoat adhesion.

It has been found that modification of the epoxy-based coating compositions, either in the resins, or the hardener or curing agent component, can lead to improved intercoat adhesion with topcoats based on Michael addition curing chemistry.

The following systems have been examined: Water-borne epoxy resins:

internally nonionic modified epoxy resins, externally emulsified epoxy resins

Hardeners or curing agents for water-borne epoxy resins:

Amine hardeners having secondary and/or primary amino groups, amidoamines, epoxy- amine adducts having secondary and/or primary amino groups, Mannich bases, phenalkamines and phenalkamides,

In aqueous epoxy resin dispersions, the epoxy resin must be modified to form a stable dispersion, by introducing nonionic hydrophilic components into an epoxy resin, as epoxides would react with the acid groups of anionic surfactants, and with the neutralisation acid of cationic surfactants. Frequently, the preferred nonionic hydrophilic moiety to be introduced into the epoxy resin using appropriate chemistry is an oligomeric or polymeric oxyethylene, in the form of a polyoxyethylene glycol. Introduction of the commonly used poly (oxy-ethylene) blocks as hydrophilising moiety is a difficult step as strong acid catalysts, mostly Lewis acids such as boron trifluoride, or complexes thereof with ethers or amines, have to be used, and the process is difficult to control. Such chemistry has been described in EP 0 272 595 Bl, and also, in EP 0 346 742 Bl, for epoxy resins. These hydrophilically modified epoxy resins are referred to as "hydrophilic epoxy resins A" hereinafter. Hydrophilic modification of curing agents based on adducts of epoxide-functional compounds and amines has been described, i. a., in EP 0 000 605 Bl ("epoxy hardeners B").

As described in EP 0491 550 Bl, stable dispersions of an epoxy resin in water can also be made by addition of a surfactant based on an alkylaryloxy poly(l-methylethane-l,2-diyl-oxy -block- ethane-l,2-diyl-oxy)ethanol to a modified epoxy resin made by reaction of one or more polyepoxides having terminal glycidyl ether groups, optionally under addition of at least monofunctional aromatic hydroxy compounds, further optionally under addition of chain terminators which are monofunctional aromatic or aliphatic compounds having active hydrogen groups that are reactive towards epoxides, which are preferably selected from the group consisting of hydroxyl groups, amino groups, carboxyl groups, and thiol groups, one or more aliphatic dicarboxylic acids having from twelve to thirty-six carbon atoms or dimers of unsaturated fatty acids. The polyepoxides having terminal glycidyl ether groups can be derived from polyhydroxyhydrocarbons which have, on average, more than one primary or secondary hydroxyl group bound to a compound having aliphatic, cycloaliphatic or aromatic moieties, the latter optionally being at least partially hydrogenated or halogenated. The presence of the long- chain aliphatic dicarboxylic acids in the modified epoxy resin ensures compatibility with the lipophilic moiety of the surfactant used. These dispersions are referred to hereinafter as "aqueous epoxy resin dispersions C".

In US 5,118,729 A, corresponding to WO 1991/010 695 Al, emulsifiers for dispersing epoxy resin in water are disclosed which are defined by formula A - X - O - (CH ₂ -CH ₂ -0-) _n - R, where A is the residue of a polyglycidyl ether of a polyhydroxy hydrocarbon compound, and is the reaction product of an epihalohydrin with one or more polyhydroxy hydrocarbon compounds or halogenated polyhydroxy hydrocarbon compounds; or the reaction product of a polyglycidylether of a polyhydroxy hydrocarbon compound with one or more polyhydroxy hydrocarbon compounds, halogenated polyhydroxy hydrocarbon compounds, or a hydrocarbon compound having a carboxylic acid functionality, or a mixture these latter compounds; the linking group X is the residue of a difunctional compound which is capable of reacting with the primary hydroxyl group of a monoalkylether of a polyethylene glycol and a 1,2-glycidyl ether moiety; R is a to C ₁₀ alkyl moiety; and n is a positive real number such that the composition is emulsifiable in water. The difunctional compound from which the linking group is derived is preferably a dicarboxylic acid, or an anhydride thereof, such as phthalic anhydride, 1,2,5,6-tetrahydrophthalic anhydride, hexahydrophthalic anhydride, or homologues of these such as 3-methyl hexahydrophthalic anhydride, and 3-ethyl hexahydrophthalic anhydride. Dispersions of epoxy resins which are emulsified in water using these emulsifiers are referred to as "aqueous epoxy resin dispersions D" hereinafter.

In WO 1993/012 187 Al, a water-soluble resin with terminal amino groups is described which is useful as a curing agent for an amine curable epoxy resin which is the reaction product of a polyamine component A comprising one or more hydrophilic amine terminated polyalkylene glycols, and optionally one or more relatively hydrophobic polyamines; a polyepoxide component B comprising i) one or more diglycidyl ethers of a polyalkylene glycol, ii) one or more diglycidyl ethers of a cycloalkylene glycol, or a mixture thereof; and optionally iii) one or more hydrophobic polyglycidyl ethers, or a reaction product of i), ii) or a mixture thereof, and optionally iii) with an amine extender having two active amine hydrogen atoms; optionally, a reactive diluent C which is capable of reacting with an epoxy resin; and optionally, a catalyst D for the reaction of an amine with an epoxy resin; and wherein component A is employed in a stoichiometric excess with respect to component B such that the terminal moieties of the reaction product are amine moieties capable of reacting with an epoxy resin, the composition has an "amine hydroxy equivalent weight of from 140 g/mol to 240 g/mol", calculated by dividing the mass of the composition by the amount of substance of amine hydrogen atoms, corresponding to a specific amount of substance n(NH)/m of amine hydrogen atoms in the composition of from 7.14 mol/kg to 4.17 mol/kg, where n(NH) is the amount of substance of amine hydrogen atoms in the composition, and m is the mass of the composition, and wherein the combination of the quantities of the amine terminated polyalkylene glycol A and of the component B comprising a diglycidyl ether of polyalkylene glycol, a diglycidyl ether of a cycloalkylene glycol, or a mixture thereof, is sufficient to render the composition water soluble or water miscible. The water miscible or water soluble amine terminated resins are hereinafter referred to as "aqueously dispersible epoxy curing agents E".

In EP 0548493 Al, a water-dilutable epoxy curing agent is disclosed which is an amidoamine made by reacting in a first step, a xylylene diamine with epichlorohydrin, where the former is used in stoichiometric excess over the epichlorohydrin, and in a second step, the polyamine of the first step is reacted with a carboxylic acid, or a mixtures of carboxylic acids, preferably a dimer fatty acid or tall oil fatty acid, or a fatty acid mixture made from tall oil fatty acid and dimer fatty acid. These amidoamines are water-dilutable, and can be used together with aqueous epoxy resin emulsions to formulate an epoxy-based coating composition. These amidoamines are hereinafter referred to as "aqueously dispersible epoxy curing agents F".

An improved version of this water-dilutable epoxy curing agent is disclosed in EP 0742243 A2, wherein a curing agent is disclosed which is made in a multi-step reaction, the first step being reacting a polyoxyalkylene polyether and an epichlorohydrin in the presence of an acidic catalyst to obtain a polyoxyalkylene halohydrin, the second step being reacting the halohydrin thus obtained with a polyamine in a stoichiometric excess of the latter, in the presence of an alkali, to obtain a hydrophilically modified polyamine. This modified polyamine can then be reacted with a hydrophobic epoxy compound, the amino groups in the modified polyamine being in stoichiometric excess with regard to the epoxide groups in the hydrophobic epoxy compound, to provide a reaction product which is a curing agents for epoxy resin, and which can easily emulsify an epoxy resin. These curing agents are hereinafter referred to as "aqueously dispersible epoxy curing agents G".

In US 5,508,324 A, an epoxy resin curing composition is disclosed which comprises the product of the reaction of a polyamine (A) containing primary amine functionality and a polyepoxide (B) having an "epoxide equivalent weight" (abbreviated as EEW, calculated by dividing the molar mass of (B) by the number of epoxide groups in one molecule, corresponding to a specific amount of substance n(EP)/m(B) of epoxide groups of from 7.69 mol/kg to 2.22 mol/kg, where n(EP) is the amount of substance of epoxide groups in component B, and m( B) is the mass of component B) of from 130 g/mol to 450 g/mol, wherein the quantities of (A) and (B) used are chosen to provide an intermediate (C) which is an adduct of about two moles of polyamine and one mole of polyepoxide, intermediate (C) being then reacted with a polyepoxy resin (D) having an EEW of 450 g/mol to 2000 g/mol (corresponding to a specific amount of substance n(EP)/ (D) of from 2.22 mol/kg to 0.5 mol/kg), in an amount sufficient to react with an amount of substance-fraction of from about 10 % to about 40 % of the primary amino groups in intermediate (C) to provide a polyamine-polyepoxide adduct (E), and adduct (E) being end capped with a monoepoxide composition comprising an aromatic glycidyl ether or an alkyl substituted aromatic glycidyl ether, or both. After neutralisation and dilution with water, this curing agent can be used together with aqueously dispersed epoxy resins to formulate epoxy- based coating compositions. These curing agents are hereinafter referred to as "aqueously dispersible epoxy curing agents H". In EP 1 544 230 Al, a method of preparation of a water-based epoxy curing agent is described which method comprises the steps of combining an active amine-hydrogen containing amine- functional dispersion (A) with an active amine-hydrogen containing amine-functional curing agent (B) in solution or emulsion form, wherein said active amine-hydrogen containing amine- functional dispersion (A) comprises a reaction product of a) a polyamine compound having at least three active amine-hydrogen groups -N-H, and b) an aqueous epoxy resin dispersion having an "epoxy solids equivalent weight" of equal to or greater than 150 g/mol (molar mass of this compound, divided by the number of epoxide groups in this compound, corresponding to a specific amount of substance of epoxide groups in this compound of less than 6.67 mol/kg), and wherein said active amine-hydrogen containing amine-functional curing agent (B) has a "solids hydrogen equivalent weight" of from 50 g/mol to 500 g/mol (molar mass of this compound, divided by the number of active aminic hydrogen groups -N-H in this compound, corresponding to a specific amount of substance of N-H groups in this compound of from 2 mol/kg to 20 mol/kg); is capable of emulsifying a liquid epoxy resin to produce a stable emulsion; and is capable of yielding coating preparations of high gloss. Preferred is a composition comprising an amine-functional dispersion A which is an aqueously dispersed reaction product of polyoxyalkylene polyamines a) and aqueous epoxy resin dispersions of bisphenol A-based epoxy resin having an average epoxy functionality of up to 2, or aqueous epoxy resin dispersions based on novolac epoxy resins having a functionality of greater than 2, as, and as active amine-hydrogen containing amine-functional curing agent B, any amine- functional compound that satisfies the conditions producing a stable emulsion and yielding coating preparations of high gloss. Preferred components B are reaction products of a polyamine and a fatty acid, which reaction product has terminal amino groups, see paragraph [0055], or an optionally modified adduct of an epoxy compound and a polyamine compound, which adduct also has terminal amino groups, or is a salt thereof, see paragraph [0067]. The preferred product B is a modified aliphatic amine mixture of dodecanedioic acid, compounds with 1,3-benzene-dimethanamine, bisphenol A, bisphenol A diglycidylether, diethylene- triamine, glycidylphenylether reaction product-epichlorohydrin-formaldehyde-propylene- oxide-triethylenetetramine polymer, see US Senate bill 2009 to temporarily suspend duties on Epilink® 701. These epoxy curing agents are hereinafter referred to as "aqueously dispersible epoxy curing agents I".

Aqueous epoxy resin compositions are described in EP 2 118 165 Bl, corresponding to WO 2008/110479 Al, they comprise an epoxy compound a), and an aminic curing agent b) which is an aqueous solution of a product from the reaction between i) an adduct between a polyamine and a liquid glycidyl ether which is not a glycidyl ether of a polyalkylene glycol but consists of glycidyl compounds based on bisphenol A or on bisphenol F, and ii) an epoxidised polyalkylene glycol, and a compound c) of the general formula (I) :

R ¹ - [-0-CH ₂ - CH ₂ -] _x - O - C ₄ H ₉ ,

where R ¹ = - H or - C ₄ H ₉ , and x = 1, 2, 3 or 4, and where the mass of compound c) is from 0.5 % to 15 % of the sum of the masses of b) and c), providing due to the presence of component c) an adjustable and recognisable end of pot life during application, for example as coating, as adhesive, as flooring, and in casting, tooling or encapsulating. An especially preferred compound of formula I is diethyleneglycol monobutylether . Preferred components a) are listed in page 6 as mixtures of a glycidyl compound based on bisphenol A, bisphenol F, or a novolac with a so-called reactive diluent which is a monoglycidylether of phenols or mono- or difunctional aliphatic or cycloaliphatic alcohols. In the examples, the epoxy compound a) is an aqueous dispersion of an epoxy resin based on bisphenol A and bisphenol F, having a specific amount of substance of epoxide groups of 3.55 mol/kg and a mass fraction of solids of ca. 67 % (Araldite® PZ 756/67, Huntsman Advanced Materials Switzerland GmbH). Preferred components b) are reaction products of an epoxidised polyalkyleneglycol ii) with adducts i) of liquid glycidyl ethers il) of bisphenol A and/or bisphenol F with poly amines i2) having at least two amino groups, such as polyethylenepolyamines, polypropylene-polyamines, aliphatic diamines such as diaminoethane and hexamethylenediamine, cycloaliphatic polyamines with at least two amino groups such as isophoronediamine, diaminocyclohexane, norbornanediamine, TCD-diamine, 1,3-bis-aminomethylcyclohexane, heterocyclic polyamines such as N-aminethylpiperazine, aromatic diamines such as meta-xylylenediamine and diaminodiphenylmethane, and polyamidoamines which optionally contain imidazoline groups, such as condensation products of monomeric and dimeric fatty acids with polyethylenepolyamines. The aminic curing agents described here are capable of emulsifying liquid epoxy resins in an aqueous system, they are hereinafter referred to as "aqueously dispersible epoxy curing agents J".

In WO 2011/112452 Al, corresponding to EP 2 365 015 A1 and EP 2 545 121 Bl, a curing agent for epoxy resins is described which comprises a first amine adduct (a), which is a reaction product of an amine-terminated intermediate (al) and a monofunctional epoxy compound (a2), wherein the amine-terminated intermediate (al) is prepared by reacting at least one polyamine (alll) or polyamidoamine (all2), having at least three active amine hydrogen atoms per molecule, and at least one epoxy resin (al2) having a functionality of at least 1.5, in a ratio of amount of substance of epoxide groups n(EP, al2) of the epoxy resin to the sum of amounts of substance of polyamine (alll) or polyamidoamine (all2) of from 0.9 mol : 1 mol to 1 mol : 10 mol, the excess of the polyamine or polyamidoamine being eliminated, and wherein the monofunctional epoxy compound is present in a quantity calculated to react away the primary amines still present in the amine-terminated intermediate, (b) an optional second amine adduct which is prepared from a cycloaliphatic alkyl amine or polyamine and an epoxy compound, (c) a sterically hindered hydrophobic alkyl amine or diamine, and/or a hydrocarbon resin, (d) a component having amino or polyamino polyalkyleneglycol moieties and/or a medium to low molar mass amino silane, and (e) optionally a metal powder. This curing composition, hereinafter referred to as "epoxy curing composition K", can be mixed with metal powder, and is fully compatible with a water-borne epoxy resin.

In WO 2011/146304 Al, an advanced liquid epoxy resin is described which is obtained by an advancement reaction comprising the steps (a) reacting a liquid polyepoxide with an aliphatic diol or a reactive diluent in the presence of a catalyst; (b) reacting the product obtained in step (a) with a flexible epoxy resin; and (c) reacting the product obtained in step (b) with a phenolic compound and a nonionic dispersant. In preferred embodiments, the liquid polyepoxide used in step (a) is a polyglycidyl ether based on bisphenol A or bisphenol F and epichlorohydrin, having terminal 1,2-epoxide groups and an "epoxy equivalent weight" (molar mass, divided by the average number of epoxide groups in a molecule) between 100 g/mol and 5000 g/mol, corresponding to a specific amount of substance of epoxide groups of from 0.2 mol/kg to 10.0 mol/kg. The aliphatic diol is preferably a linear or branched aliphatic, cycloaliphatic, or aromatic-aliphatic diol having from two to not more than fifty carbon atoms, including ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol, 1,3- propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,5-hexanediol, 1,4-cyclohexanediol, 1,4-dimethylolcyclohexane, 1,8-octanediol, 2,2,4-trimethyl- 1,3-pentanediol, and 2,2,4,4-tetramethyl-l,3-cyclobutanediol. The reactive diluent is preferably a diepoxide diluent, for example, a diglycidylated C ₄ - to C _1S - aliphatic alcohol or aromatic alcohol, such as a diglycidyl ether of butanediol, a diglycidyl ether of resorcinol; and a diglycidyl ether of neopentyl glycol. The catalyst used in the initial reaction is a cyclic quarternary ammonium compound, such as a quarternary piperidinium salt, a quarternary pyrrolidinium salt, or a quaternary morpholinium salt, where the substituents R ² and R ³ on the nitrogen atom in the cycle are: R ² is a - to C ₈ - alkyl group, and R ³ is C,- to C ₈ - alkyl group, a C ₂ - to C ₈ - hydroxyalkyl group, a C ₃ - to C ₈ - alkoxyhydroxyalkyl group, a C ₃ - to C ₈ - alkenyl group, a C ₃ - to C ₈ - alkoxycarbonylalkyl group, a C ₃ - to C ₈ - alkylcarbonylalkyl group, a C ₇ - to C ₉ - phenylalkyl group, or a C ₇ - to C ₉ - phenylhydroxy alkyl group, and the hydrogen atom in the 4-position of the piperidinium compound may be substituted with a hydroxyl group. The flexible epoxy resin in the second step (b) has an elastomeric chain in the polymer backbone, which is prferably a polyether chain derived from one or more alkylene oxides, such as ethylene oxide, propylene oxide, or butane-1, 4-diyl-oxy. The phenolic compound used in step (c) has preferably one or more than one, and less than three phenolic hydroxyl groups per molecule and preferably obeys the formula HO-Bz(Z ₄ )-A-Bz(Z ₄ )-OH, where A is a divalent group having from one to eight carbon atoms, or is a direct bond, -0-, -CO-, -S-, -SO _z -, -SO-, or a (methyl, phenyl)-methan-diyl group, Bz is a 1,2-, 1,3-, or 1,4-benzene-diyl group where the remaining hydrogen atoms are optionally substituted by Z groups which are independently from each other selected from the group consisting of a halogen and an alkyl group having from one to four carbon atoms. The phenolic compound is preferably selected from the group consisting of phenol, cresol, 2,6- dimethylphenol, ethylphenol, isopropylphenol, tert- butylphenol, hexylphenol, cyclohexylphenol, 2,6-di-(tertiary-butyl)-p-cresol, guaiacol and eugenol; polyhydric phenols such as catechol, resorcinol, hydroquinone, tert-butylcatechol and pyrogallol; biphenols such as biphenol and dimethyl biphenol; bisphenols such as bisphenol A, bisphenol F, bisphenol S, methylene-bis(methyl-tert-butylphenol) and thiobis(methyl-tert- butylphenol); and naphthols such as 1- and 2-naphthol and dihydroxynaphthalene, and their F-, Cl- or Br-substituted derivatives. The non-ionic dispersant is preferably based on an addition product of a polyoxyalkylene glycol and a diglycidyl compound, wherein the polyoxyalkylene glycol preferably has a mass average molar mass as determined by gel permeation chromatography using polystyrene standards of from 200 g/mol to 10 kg/mol, and is a selected from the group consisting of block copolymers of ethylene oxide and propylene oxide, polyoxyethylene glycols, polyoxypropylene glycols and polyoxybutylene glycols and mixtures of these. Particularly preferred are polyxoyethylene glycols. The diglycidyl compounds which are reacted with the polyoxyalkylene glycol are based on polyglycidyl ethers of polyhydroxy compounds and polyglycidyl esters of polycarboxylic acids, examples of aromatic and aliphatic polyhydroxy compounds including resorcinol, hydroquinone, 2,2-bis(4'- hydroxyphenyl)propane (bisphenol A), mixtures of isomers of dihydroxydiphenyl-methane (bisphenol F), tetrabromobisphenol A, 4,4-dihydroxy-diphenylcyclohexane, 4,4'-dihydroxy-3,3'- dimethyldiphenylpropane, 4,4'-dihydroxy-diphenyl, 4,4'-dihydroxybenzo-phenone, l,l-bis(4'- hydroxyphenyl)ethane, 2,2-bis[4'-(2"-hydroxy-prop-oxy)-phenyl]propane, l,l-bis(4'-hydroxy- phenyl)isobutane, 2,2-bis(4'-hydroxy-3'-tert-butyl-phenyl]-propane, bis(2-hydroxynaphthyl)- methane, 1,5-dihydroxynaphthalene, tris(4-hydroxy-phenyl)-methane, bis(4-hydroxyphenyl)- ether, bis(4-hydr oxy-phenyl)-sulf one and the halogenation and hydr o-genation products of the above-mentioned compounds, ethylene glycol, diethylene glycol, triethylene glycol, poly oxyethylene glycols (with degrees of polymerisation of n = 1 to 35), 1,2-propylene glycol, polyoxypropylene glycols (n = 1 to 15), 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2,6-hexanetriol, glycerol, neopentylglycol, trimethylolethane and trimethylol- propane. This advanced liquid epoxy resin which is hereinafter referred to as "hydrophilic epoxy resin L" is then emulsified by adding water, and mixing under high shear.

In WO 2012/082342 Al, an epoxy composition is disclosed, comprising a reaction product prepared by reacting an epoxy component; and an amidoamine composition, wherein the reaction product comprises an epoxyfunctional surfactant having a structure: EP-0-CH ₂ -CH(0H)-CH ₂ -N(H0P)-A-NH-[C0-CH ₂ -(0A) _P -CH ₂ -C0-NH-A-NH-

- C0-CH ₂ -(0A) _p ] _n -0-CH ₂ -C0-NH-A-N(H0P)-CH ₂ -CH(0H)-CH ₂ -0-EP, where "EP" is a monovalent residue of an epoxy resin, preferably an oligomeric or polymeric bisphenol A diglycidylether with from one to nine repeating units, after taking away one terminal glycidylether group of formula

-O-CH ₂ -CH-CH ₂ ,

^L o ^J

"HOP" is a 2-hydroxy-3-oxyacyloyl-propan-l-yl group, "- OA-" is a divalent alkyleneoxy group of formula - CH(X)-{ CH(Y)} _m -O- having alkylene groups with from two to twelve carbon atoms (m is from 1 to 11), which may optionally be substituted with groups X and Y independently selected from the group consisting of methyl, ethyl, and hydroxymethyl groups, n is from 1 to 3, p is the degree of polymerisation of the alkyleneoxy groups in the poly- (alkyleneoxy) moiety and is from 18 to 500, and the acyloyl group in HOP is an alkylcarbonyl group, an arylcarbonyl group, or an acylcarbonyl group which can have up to fifty carbon atoms. The divalent hydrocarbon group A is derived from a diamine having two primary amino groups, or one primary amino group and one secondary amino group, or two secondary amino groups, by removing both amino groups, and can be a branched or linear aliphatic group, a cycloaliphatic group, and aliphatic- aromatic group, or an aromatic group, having from two to eighteen carbon atoms, where one or more than one carbon atoms may be substituted by non-reactive oxygen or nitrogen groups. This reaction product, hereinafter referred to as "epoxy-functional amidoamine surfactant M", is used as surfactant for producing aqueously dispersed epoxy resins, and in another embodiment, it can be converted to an amine functional compounds, by reaction thereof with diamines having at least one primary amino group, and at least one secondary amino group, which amino-functional reaction product can be used as aminic curing agent for epoxy resins, hereinafter referred to as "aminic epoxy curing agent M". It is further possible to react these curing agents with monofunctional epoxide compounds to convert primary amino groups therein to secondary amino groups.

In WO 2012/150312 Al, a hydrophilically modified multifunctional amine AC is disclosed which has more than one primary amino group per molecule, and at least one group per molecule derived from the reaction of an epoxide group with a reactive group selected from the group consisting of secondary amino groups >NH, hydroxyl groups -OH, mercaptan groups -SH, amide groups -CO-NHR, where R can be hydrogen or an alkyl group having from one to twelve carbon atoms, hydroxyester groups, and acid groups, particularly carboxyl groups - COOH, sulphonic acid groups -S0 ₃ H, and phosphonic acid groups -P0 ₃ H ₂ , and preferably, also moieties which are compatible with an epoxy resin. This multifunctional amine AC is made by a multi-step process wherein a multifunctional amine A having two or more primary amino groups, and at least one further reactive group which is preferably a secondary amino group, is first reacted with a blocking agent B that reacts selectively with primary amino groups, and does not react with secondary amino groups. The reaction products AB therefore have only the further reactive groups, preferably secondary amino groups, left as reactive amino groups. In a second step, the secondary amines AB are reacted with a multifunctional, at least difunctional, compounds C that react with the blocked amines AB under formation of adducts ABC which may be of the structure C(AB)n' where n is at least two. The compounds C are preferably selected from the group consisting of glycidyl esters of at least dibasic aromatic or aliphatic or cycloaliphatic acids, of glycidyl ethers of at least dihydric phenols, and of glycidyl ethers of at least dihydric aliphatic or cycloaliphatic alcohols, particularly good compatibility with epoxy resins when used as curing agent for these is obtained when oligomeric glycidyl ethers of bisphenol A and/or bisphenol F are used. The blocking agent B for the primary amino groups is preferably a ketone which forms a Schiff base with a primary amino group, this Schiff base is cleaved by reaction with water to regenerate the free primary amino group. The multifunctional primary amine of this invention is hereinafter referred to as "multifunctional amine N".

In WO 2013/181210 A2, corresponding to US 9,701,864 B2 and EP 2836531 A2, epoxy resins for waterborne dispersions are disclosed which are made from compounds comprising the epoxide functional reaction product of at least one molecule

(a) comprising two terminal epoxy-reactive moieties with two molecules (b) comprising two epoxide moieties, wherein said compound comprises, pendent to the residue of (a), one or more polyoxyalkylene or polyoxyalkylene alkyl ether radical(s) having a mass average molar mass of at least 400 g/mol. Incorporation of the polyoxyalkylene moieties is made via reaction with dicarboxylic acids or anhydrides thereof which in turn add to the epoxide group of the epoxy resins. The modified epoxy resins exhibit lower melt viscosity and have less propensity to foam. These modified epoxy resins are hereinafter referred to as "modified epoxy resins O".

In EP 2 692 778 Al, corresponding to US 9,404,014 B2, aqueous co-dispersions of epoxy resins and silane oligomers are disclosed. Although no further details are given in this patent application, it can be seen from the website of the supplier that this product CoatOSil® MP 200 as mentioned in the examples is an epoxy functional silane oligomer claimed to be stable against hydrolysis. Co-dispersions of epoxy resin and epoxy-functional silane oligomers are hereinafter referred to as "silane-modified epoxy resin dispersions P".

In WO 2014/072308 A2, externally emulsified epoxy-amine adducts are disclosed that are prepared by reacting a compound C having at least one reactive group, and a compound AB having at least one blocked primary amino group, and at least one group that is reactive towards the reactive group(s) of compound C. The externally emulsified epoxy-amine adducts comprise at least one nonionic emulsifier. The compounds C comprise a mass fraction of less than 5 % of oxyethylene and of oxpropylene moieties to achieve faster hardness development. The externally emulsified epoxy-amine adducts are hereinafter referred to as "epoxy curing agent dispersions Q".

In WO 2017/158071 Al, a hardener composition for an epoxy resin is disclosed wherein the hardener composition comprises moieties Ml having at least one structural element of formula

> N - D1 - NH ₂ , and moieties M2 having at least one structural element of formula

> N - D2 - NH - C(O) - Q, wherein D1 is a first bivalent group, D2 is a second bivalent group, which are both independently selected from - (CR ^la R ^lb ) _m - [N - (CR ^lc R ^ld ) _ni ] -, R ^la , R ^lb , R ^lc , and R ^ld are independently of each other and separately for each m and ni, selected from the group consisting of H, and optionally substituted linear or branched alkyl groups having from one to six carbon atoms, or may form a ring, preferably being H, particularly preferred all being H, and Q is a univalent group which is an optionally substituted linear or branched alkyl group or alkenyl group having from five to thirty-nine, preferably from seven to thirty-six, and particularly preferably, from eleven to twenty-three carbon atoms. These epoxy hardeners which are particularly useful for coating of metals and mineral substrates, are referred to as "epoxy hardeners R".

In US 4,541,958 A, a hardening agent for epoxy resins is disclosed which is a reaction product of a polyamine obtained by reacting m-xylylene diamine with epichlorohydrin, and a carboxylic acid which can be a monocarboxylic acid, such as tall oil fatty acid, a dicarboxylic acid such as adipic acid, or a dimer fatty acid, or a poly carboxylic acid, such as a trimer fatty acid having fifty-four carbon atoms. These hardening agents are usually referred to as "amides", correctly "polyamidoamines", and are here referred to as "epoxy curing agents S".

In US 6,262,148 Bl, a low colour Mannichbase reaction product is described, obtained from a cashew nutshell liquid extract which consists of a major portion of cardanol, an aldehyde, preferably formaldehyde, and an aromatic amine, preferably xylylenediamine, or an alicyclic amine, preferably 1,3-bis-aminomethylcyclohexane, or their mixtures. This phenalkamine hardener is referred to here as "phenalkamine curing agent T".

While such coating compositions have merit as coating agent particularly for base metals, and provide excellent corrosion protection without liberation of volatile amines during application and curing, the adhesion to topcoats applied onto paint films made from these two-pack coating compositions as described supra has been found to need improvement, particularly when applying such coating compositions for topcoats that are not in the form of aqueous dispersions, but based on solventless paints, or solvent-based paints, particularly such paints as disclosed, i. a. in EP 2374836 Al, and WO 2014/166880 Al, and WO 2018/005077 A1 where the crosslinking process is a Michael addition reaction between CH-acidic compounds as Michael donors, and electron-deficient olefinically unsaturated compounds as Michael acceptors. Object of the Invention

It has therefore been the object of this invention to develop combinations of epoxy resins with hardeners for epoxy resin based aqueous coating compositions that can be used in a two-pack formulation, and which lead to coating films having excellent corrosion protection, and which allow overcoating with further coatings applied thereon, particularly using such coating compositions that are not water-borne. A further object of this invention is providing a multi layer coating with improved intercoat adhesion, wherein a first layer is based on an epoxy coating composition, and the second layer is based on a coating composition which is cured by Michael addition.

Summary of the Invention

It has been found, in the experiments that have lead to the present invention, that a two-layer coating which comprises a first layer of an epoxy primer applied in the form of a two-pack water-based epoxy coating composition, and a second layer applied in the form of a coating composition comprising a Michael donor component, a Michael acceptor component, and a catalyst for the Michael addition reaction between Michael donor component and Michael acceptor component leads to good substrate adhesion, and good corrosion protection for the substrate, and also, good protection of the epoxy primer layer. In comparison to a two-layer coating where the epoxy primer is not applied in the form of a water-borne coating composition, both corrosion protection and adhesion to the substrate has been improved. It is possible to further improve the adhesion between the epoxy primer coating made from an aqueously dispersed epoxy resin E* and a hardener composition H* for such aqueously dispersed epoxy resins E*, and the further coating layer applied thereon by incorporation of long-chain alkyl groups into the aqueously dispersed epoxy resin E*, or preferably, into a hardener composition H* for such aqueously dispersed epoxy resins E*, or, also preferably, into both of E* and H*.

Incorporation of long-chain alkyl groups L into the modified epoxy resin E* component can be made by adding to an unmodified epoxy resin E a modified epoxy resin E' which comprises at least one constituent which has a long-chain alkyl group L, thereby obtaining a mixture EE', or by at least partially reacting an unmodified epoxy resin E with a compound LE which comprises a long chain alkyl group L and at least one functional group which is reactive with an epoxide group, thereby obtaining a partially modified epoxy resin ELE. It is also possible to use mixtures of EE' and ELE, or to mix an epoxy resin E' with a partially modified epoxy resin ELE. These modified variants of epoxy resins are commonly or individually referred to as E* hereinafter. A modified epoxy resin E* can therefore be any of the group {EE'; ELE; EE' + ELE; E'; E' + ELE; E + ELE}, where "+" stands for "mixture with".

Likewise, incorporation of long-chain alkyl groups L into the hardener H* can be made by adding to a non-modified hardener H a modified hardener H' which comprises at least one constituent which has a long-chain alkyl group L, thereby obtaining a mixture HH', or by at least partially reacting a non-modified hardener H with a compound LH which comprises a long chain alkyl moiety and at least one functional group which is reactive with a functional group in the hardener H, thereby obtaining a partially modified hardener HLH. It is also possible to use mixtures of HH' and HLH, or to mix a hardener H' with a partially modified hardener HLH. These modified variants of hardeners are commonly or individually referred to as H* hereinafter. A modified hardener or epoxy curing agent H* can therefore be any of the group {HH'; HLH; HH' + HLH; H'; H' + HLH; H + HLH}, where "+" stands for "mixture with".

For clarity, the abbreviations E and H are used in this application to designate non-modified epoxy resins and non-modified hardeners. Both can be either water-borne, or solvent borne, or liquid resins or liquid hardeners, optionally diluted with reactive compounds that carry functional groups which react either with an epoxide group or with a functional group such as an acid group, a phenolic hydroxyl group, an amino group, a hydrazine group, a mercaptan or thiol group, or a phosphine group which in turn are reactive with epoxide groups.

It has been found that combinations of epoxy resins and hardener compositions whereof at least one of these components comprises a modified epoxy resin E* and/or a modified hardener H* leads to the desired improved adhesion. The extent of modification can be adjusted by varying the length of the alkyl chains, and the degree of modification, i. e. the fraction of epoxy resin molecules or hardener molecules that are modified by incorporation of alkyl chains.

These combinations are preferably selected from the group consisting of

E + H* comprising E + {HH'; HLH; HH' + HLH; H'; H' + HLH; H + HLH} = E + HH', E +

HLH, E + HH' + HLH, E + H', E + H' + HLH, E + H + HLH,

E* + H comprising {EE'; ELE; EE' + ELE; E'; E' + ELE; E + ELE } + H = EE' + H, ELE + H, EE'

+ ELE + H, E' + H, E' + ELE + H, E + ELE + H,

E* + H* comprising {EE'; ELE; EE' + ELE; E'; E' + ELE; E + ELE } + {HH'; HLH; HH' + HLH;

H'; H' + HLH; H + HLH} = EE' + HH', EE' + HLH, EE' + HH' + HLH, EE' + H', EE' + H' + HLH, EE' + H + HLH, ELE + HH', ELE + HLH, ELE + HH' + HLH, ELE + H', ELE + H' + HLH, ELE + H + HLH, EE' + ELE + HH', EE' + ELE + HLH, EE' + ELE + HH' + HLH, EE' + ELE + H', EE' + ELE + H' + HLH, EE' + ELE + H + HLH, E' + HH', E' + HLH, E' + HH' + HLH, E' + H', E' + H' + HLH, E' + H + HLH, E' + ELE + HH', E' + ELE + HLH, E' + ELE + HH' + HLH, E' + ELE + H', E' + ELE + H' + HLH, E' + ELE + H + HLH, E + ELE + HH', E + ELE + HLH, E + ELE + HH' + HLH, E + ELE + H', E + ELE + H' + HLH, E + ELE + H + HLH

E + E* + H* comprising E + [{EE'; ELE; EE' + ELE; E'; E' + ELE; E + ELE } + {HH'; HLH;

HH' + HLH; H'; H' + HLH; H + HLH}] = E + EE' + HH', EE' + HLH, E + EE' + HH' + HLH, EE' + H', E + EE' + H' + HLH, E + EE' + H + HLH, E + ELE + HH', E + ELE + HLH, E + ELE + HH' + E + HLH, ELE + H', E + ELE + H' + HLH, E + ELE + H + HLH, E + EE' + ELE + HH', E + EE' + ELE + HLH, E + EE' + ELE + HH' + HLH, E + EE' + ELE + H', E + EE' + ELE + H' + HLH, E + EE' + ELE + H + HLH, E + E' + HH', E + E' + HLH, E + E' + HH' + HLH, E + E' + H', E + E' + H' + HLH, E + E' + H + HLH, E + E' + ELE + HH', E + E' + ELE + HLH, E + E' + ELE + HH' + HLH, E + E' + ELE + H', E + E' + ELE + H' + HLH, E + E' + ELE + H + HLH,

H + E* + H* comprising H + [{EE'; ELE; EE' + ELE; E'; E' + ELE; E + ELE } + {HH'; HLH; HH' + HLH; H'; H' + HLH; H + HLH}] = H + EE' + HH', H + EE'

+ HLH, H + EE' + HH' + HLH, H + EE' + H', H + EE' + H' + HLH, H + EE' + HLH, H + ELE + HH', H + ELE + HLH, H + ELE + HH' + HLH, H + ELE + H', H + ELE + H' + HLH, ELE + H + HLH, H + EE' + ELE + HH', H + EE' + ELE + HLH, H + EE' + ELE + HH' + HLH, H + EE' + ELE + H', H + EE' + ELE + H' + HLH, EE' + ELE + H + HLH, H + E' + HH', H + E' + HLH, H + E' + HH' + HLH, H + E' + H', H + E' + H' + HLH, E' + H + HLH, H + E' + ELE + HH', H + E' + ELE + HLH, H + E' + ELE + HH' + HLH, H + E' + ELE + H', H + E' + ELE + H' + HLH, E' + ELE + H + HLH, H + E + ELE + HH', H + E + ELE + HLH, H + E + ELE + HH' + HLH, H + E + ELE + H', H + E + ELE + H' + HLH, E + ELE + H + HLH

E + H + H* comprising E + H + {HH'; HLH; HH' + HLH; H'; H' + HLH; H + HLH} = E +

H + HH', E + H + HLH, E + H + HH' + HLH, E + H', E + H + H' + HLH, E + H + HLH,

E + H + E* comprising E + H + {EE'; ELE; EE' + ELE; E'; E' + ELE; E + ELE } = E + H + EE',

E + H + ELE, E + H + EE' + ELE, E + H + E', E + H + E' + ELE, E + H + ELE, and

E + E* + H + H* comprising E + H + {EE'; ELE; EE' + ELE; E'; E' + ELE; E + ELE } + {HH'; HLH;

HH' + HLH; H'; H' + HLH; H + HLH} = E + H + EE' + HH', E + H + EE' + HLH, E + H + EE' + HH' + HLH, E + H + EE' + H', E + H + EE' + H' + HLH, E + H + EE' + HLH, ELE + HH', E + H + ELE + HLH, E + H + ELE + HH' + HLH, E + H + ELE + H', E + H + ELE + H' + HLH, E + H + ELE + HLH, E + H + EE' + ELE + HH', E + H + EE' + ELE + HLH, E + H + EE' + ELE + HH' + HLH, E + H + EE' + ELE + H', E + H + EE' + ELE + H' + HLH, E + H + EE' + ELE + HLH, E + H + E' + HH', E + H + E' + HLH, E + H + E' + HH' + HLH, E + H + E' + H', E + H + E' + H' + HLH, E + H + E' + HLH, E + H + E' + ELE + HH', E + H + E' + ELE + HLH, E + H + E' + ELE + HH' + HLH, E + H + E' + ELE + H', E + H + E' + ELE + H' + HLH, E + H + E' + ELE + HLH, E + H + ELE + HH', E + H + ELE + HLH,

E + H + ELE + HH' + HLH, E + H + ELE + H', E + H + ELE + H' + HLH.

Compounds Comprising Long Chain Alkyl Groups

Compounds comprising long chain alkyl groups L with functionalities usable for incorporation into components of epoxy systems are preferably compounds having at least one functional group which reacts with an epoxide group:

fatty acids which are selected from the group consisting of monofunctional fatty acids, difunctional fatty acids, and multi-functional fatty acids which comprise those with three or more acid groups,

fatty amines which are selected from the group consisting of monofunctional fatty amines, difunctional fatty amines, and multi-functional fatty amines which comprise those with three or more amino groups, wherein the amino groups can be primary or secondary amino groups, or mixtures of these,

fatty alcohols which are selected from the group consisting of monofunctional fatty alcohols, difunctional fatty alcohols, and multi-functional fatty alcohols which comprise those with three or more hydroxyl groups, and

alkylphenols which can be reacted to amines, via Mannich reaction with formaldehyde and amines, to form amines which can be incorporated into a hardener component, and to novolaks via reaction with formaldehyde with acidic catalysts, which can be reacted with epoxide- functional compounds to form epoxide compounds with a high functionality.

Further compounds can also be used which have comprising long chain alkyl groups and at least one epoxide functional group, which include

glycidyl esters of fatty acids which are selected from the group consisting of monofunctional fatty acids, difunctional fatty acids, and multi-functional fatty acids which comprise those with three or more acid groups,

N-glycidylamines which are selected from the group consisting of N-glycidylamines made from secondary monofunctional fatty amines, N-glycidylamines made from secondary difunctional fatty amines, and N-glycidylamines made from secondary multi-functional fatty amines which comprise those with three or more amino groups, wherein the amino groups of the fatty amines are exclusively secondary amino groups, or mixtures of these,

glycidyl ethers of fatty alcohols which are selected from the group consisting of monofunctional fatty alcohols, difunctional fatty alcohols, and multi-functional fatty alcohols which comprise those with three or more hydroxyl groups, or mixtures of these, and

epoxidised esters of unsaturated fatty acids with alcohols having from one to thirty carbon atoms, epoxidised oils which are triglycerides of unsaturated fatty acids, or mixtures of these.

These compounds comprising long chain alkyl groups can be incorporated into the hardener component or the epoxy resin component or into both the hardener component and the epoxy resin component.

The invention further relates to a process of making the modified hardeners H' and HLH, to a process of making the modified epoxy resins E' and ELE, to prepare combinations comprising at least one of these modified hardeners H' and HLH and modified epoxy resins E' and ELE, to formulate water-borne epoxy-based coating compositions, and to the application of these coating compositions to substrates which are further coated with aqueous or non-aqueous coating compositions.

Detailed Description of the Preferred Embodiments

Modified Hardener Compositions H' Comprising Long Chain Alkyl Groups

A "long chain" alkyl group, in the context of this invention, is a linear or branched alkyl group with more than five carbon atoms in sequence, preferably having from six to thirty carbon atoms, more preferably, from eight to twenty-five carbon atoms, and particularly preferred, from ten to twenty-two carbon atoms.

Hardeners Moieties Derived from Dimer Fatty Acids (Embodiment 1)

One possibility of incorporation of long-chain alkyl groups to prepare a hardener composition H' is incorporation of dimer fatty acids in the form of beta-hydroxyesters into these hardener compositions H'. This modified hardener composition H' provides epoxy-based coating compositions that exhibit very good adhesion to substrates, particularly metal substrates, and also show improved interlayer adhesion for further coatings which are applied upon this epoxy-based coating layer. This embodiment of the invention therefore relates to hardeners H' for epoxy resins, which hardeners H' are reaction products of

at least difunctional epoxides HI,

at least difunctional hydroxypolyoxyalkylenes H2,

optionally, at least difunctional hydroxyaromatic compounds H3,

at least difunctional unsaturated fatty acids H42 having a carboxyl functionality of more than one which are mixtures of the so-called dimer fatty acids and trimer fatty acids, with minor quantities of monofunctional fatty acids also being present in the commercial products, which compounds H42 are incorporated into the hardeners H in the form of beta-hydroxyesters H4 which are formed by reaction of compounds H42 with the at least difunctional epoxides HI,

secondary amines H5 having additional carbonylimine-blocked primary amino groups, obtained by reaction of amines H51 having at least one primary amino group and at least one secondary amino group with carbonyl compounds H52 which have an aldehyde or ketone carbonyl group, and optionally,

hydroxy-functional secondary amines H6 having at least one secondary amino group and at least one hydroxyl group, and

optionally, of amines H7 having at least one primary, and at least one tertiary amino group.

The at least difunctional epoxides HI are preferably glycidyl esters of at least difunctional acid compounds Hll, or glycidyl ethers of at least difunctional hydroxy compounds H12. These said acid compounds Hll are aromatic or aliphatic carboxylic acids havingup to forty carbon atoms, and are preferably selected from the group consisting of terephthalic acid, isophthalic acid, adipic acid, dodecanedioic acid, and cyclohexane dicarboxylic acid, and these said hydroxy compounds H12 are aromatic or aliphatic compounds having at least two hydroxyl groups and up to forty carbon atoms per molecule, and are preferably selected from the group consisting of aliphatic dihydroxy compounds, preferably hexane diol, dihydroxycyclohexane, and oligomeric or polymeric oxyalkylenediols, and of aromatic dihydroxy compounds, particularly hydroquinone, resorcinol, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl-sulphone, 4,4'-di- hydroxybenzophenone, 4,4'-dihydroxydiphenylmethane, 2,2-(4,4'-dihydroxy-diphenyl)pro- pane, or from low molar mass or oligomeric novolaks based on phenol, and/or cresol isomers which have more than two, and up to five phenolic hydroxyl groups for the commercially available grades that are used to prepare the so-called epoxy novolak resins.

The at least difunctional hydroxypolyoxyalkylenes H2 obey the formula HO/R'-O^-H where R ¹ is a divalent linear or branched alkylene group of from two to four carbon atoms, n being preferably from five to one hundred, and have at least two hydroxyl groups, and are preferably oxyethylene homopolymers or copolymers having both oxyethylene and oxypropylene units in their molecular structure, where the amount of substance-fraction of oxyethylene units in the copolymer molecules is preferably at least 50 %. Preferred oxyethylene-based polymeric polyols have preferably a number average molar mass of from 1 kg/mol to 20 kg/mol. As the reactivity of aliphatically bound hydroxyl groups during an advancement reaction is too low, moieties derived from the at least difunctional hydroxypolyoxyalkylenes H2 have to be introduced into the hardeners H' by first forming an adduct of a diepoxide H21 which is preferably selected from the same group of compounds as HI, but independently thereupon, preferably bisphenol A diglycidylether, and the hydroxypolyoxyalkylenes H2 in the presence of a strong acid catalyst Kl, preferably a Lewis acid catalyst, and subjecting this adduct to an advancement reaction with further epoxides and the coreactants as mentioned supra. Preferred Lewis acid catalysts are boron trifluoride BF ₃ , tetrafluoroboric acid HBF ₄ , complexes of boron trifluoride with carboxylic acids or aliphatic ethers, and amine complexes of boron trifluoride with aliphatic or aromatic amines, such as ethylamine, N-methylcyclohexylamine, isopropylamine, piperidine, N-methylpiperidine, benzylamine, dimethylbenzylamine, N- methylaniline, N,N-dimethylaniline, or aniline, or mixtures of two or more of these amines.

The at least difunctional hydroxyaromatic compounds H3 are aromatic dihydroxy or polyhydroxy compounds, preferably selected from the group consisting of hydroquinone, resorcinol, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl- sulphone ("bisphenol S"), 4,4'-dihydroxybenzophenone, bisphenol A, bisphenol F, and novolaks of low to medium degree of oligomerisation. Preferred are bisphenol A and bisphenol F.

The at least difunctional unsaturated fatty acids H42 are mixtures of the so-called dimer fatty acid and trimer fatty acid isomers, with minor quantities of (unreacted) monofunctional acids also being present in the commercial products, which are mostly prepared from tall oil by heat treatment on clay catalysts. Being acids, they directly react with epoxides under advancement reaction conditions, under formation of beta-hydroxy esters H4. The fatty acids H42 replace partly, or completely, the hydroxyaromatic compounds H3 in the advancement reaction.

The secondary amines H5 having additional carbonylimine-blocked primary amino groups are made in a separate reaction from amines H51 having at least one primary amino group and at least one secondary amino group and carbonyl compounds H52 which have an aldehyde or ketone carbonyl group. The stoichiometry is selected so that all primary amino are consumed by reaction with the carbonyl blocking compound H51 to form Schiff bases, or imines having the structure - N = C <, and only the secondary amino groups remain. Preferred amines H51 are diamino-oligoalkyleneimines and diamino-polyalkyleneimines, preferably selected from the group consisting of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, etc., dipropylenetriamine, tripropylenetetramine, tetrapropylenepentamine, etc., dibutylene- triamine, tributylenetetramine, tetrabutylenepentamine, etc., and dihexylenetriamine, tri- hexylenetetramine, tetrahexylenepentamine, etc. These have all two primary amino groups, and a growing number of secondary amino groups. Monosecondary amines function as chain stopper, having an amine functionality of one; disecondary amines lead to linear chains, and amine with a larger number of secondary amino groups should only be used in limited amounts as they give rise to branching and crosslinking during the reaction.

The secondary hydroxyamines H6 have one secondary amino group, and at least one hydroxyl group, and are preferably linear, branched or cyclic aliphatic amines, preferably selected from the group consisting of diethanolamine, dipropanolamine, diisopropanolamine, dibutanol- amine, N-methylethanolamine, N-ethylethanolamine, and 4-hydroxypiperidine.

The amines H7 having at least one primary, and at least one tertiary amino group and are used to introduce basic groups into the reaction product, and are preferably linear, branched or cyclic aliphatic amines, preferably selected from the group consisting of N,N-dimethyl- aminoethylamine, N,N-diethylaminoethylamine, N,N-dimethylaminopropylamine, and N,N- diethylaminopropylamine.

Monofunctional epoxides H8 can be used to adjust the amount of free amine groups of the hardener H. Preferred are glycidyl ethers of phenols, such as the glycidyl ether of cresol, and glycidyl esters of monofunctional aliphatic carboxylic acids having from five to twenty carbon atoms, particularly preferred are glycidyl esters of branched aliphatic carboxylic acids, such as the glycidyl esters of neopentanoic acid, and neodecanoic acid.

The process for the preparation of the hardener H' comprises the following steps:

(a) preparation of a hydrophilically modified epoxy resin by reacting an at least difunctional hydroxypolyoxyalkylene H2 and an at least difunctional epoxide HI in the presence of an acidic catalyst Kl, under heating up to 200 ^° C, preferably from 50 ^° C to 150 ^° C, particularly preferred from 70 ^° C to 110 ^° C,

(b) preparing, in a separate reaction, a carbonylimine H5 from an aliphatic amine H51 having at least one primary amino group, and at least one secondary amino group in its molecule, and a blocking agent H52 for primary amino groups, which blocking agent has preferably carbonyl groups of a ketone or of an aldehyde, to form a ketimine or an aldimine H5,

(c) adding to the product of step (a), the at least difunctional acids H42, and a catalyst (preferably triphenyl phosphine), and optionally, the hydroxyaromatic compounds H3, where in the reaction of these, a part of the epoxide groups is consumed. Optionally, an inert solvent (preferably an aliphatic etheralcohol) is added, and the product H5 from step (b) is added and reacted until the secondary amino groups of H5 have been consumed, (d) secondary hydroxyamines H6 are then added in a preferred embodiment, and the reaction is continued until all secondary amino groups of H6 have been consumed. Then, in a further preferred embodiment, primary-tertiary amines H7 are added and the reaction is conducted until all epoxide groups have been consumed,

(d') further diepoxides HI are optionally added after addition of either or both of H6 and H7 if needed to consume all remaining primary or secondary amino groups,

(e) the reaction product of step (d) is then neutralised by addition of an organic or inorganic acid, and water is added to the neutralised mixture to decompose the ketimine groups, under regeneration of primary amino groups, and of the blocking agent which is then distilled off together with the optional etheralcohol solvent. The amount of free amino groups in the resulting dispersion can be adjusted by addition of monofunctional epoxides H8.

It has been found, in the investigations upon which the present invention is based that the specific amount of substance n(HE) / m _s of beta-hydroxy ester structures derived from component H42 in the hardener H', based on the mass of solids m _s in the aqueous hardener dispersion, is preferably from 0.2 mol/kg to 2 mol/kg, particularly preferably, from 0.25 mol/kg to 1.5 mol/kg, and especially preferred, from 0.28 mol/kg to 1.3 mol/kg. When using lower specific amounts of substance, the increase in adhesion between the epoxy-resin based primer layer and the coating applied onto the said primer layer is not manifest, and when using higher specific amounts of substance, adhesion of the said primer layer to the metal substrate is impaired.

Hardeners Comprising Moieties Derived from Aliphatic Aminesf Embodiment 2)

One further possibility of incorporation of long-chain alkyl groups to prepare a hardener composition H' is incorporation of fatty amines with a long-chain alkyl group L, in the form of beta-hydroxyamines into these hardener compositions H'. This modified hardener composition H' provides epoxy-based coating compositions that exhibit very good adhesion to substrates, particularly metal substrates, and also show improved interlayer adhesion for further coatings which are applied upon this epoxy-based coating layer. This embodiment of the invention therefore relates to hardeners H' for epoxy resins, which hardeners H' are reaction products of at least difunctional epoxides HI,

at least difunctional hydroxypolyoxyalkylenes H2,

optionally, at least difunctional hydroxyaromatic compounds H3,

at least monofunctional linear or branched or cyclic aliphatic amines H43 having from four to twenty-five carbon atoms and at least one amino group which is primary or secondary, preferably primary, and no further reactive groups, particularly no tertiary amino groups and no hydroxyl groups, which aliphatic amines or fatty amines H43 are incorporated into the hardeners H' by reaction of its primary or secondary amino group with an epoxide group to form a beta-hydroxyamine -NR-CH ₂ -CH(OH)- where R is H or an alkyl group having from one to six carbon atoms, and wherein the amines H43 do not have more than three primary or secondary amino groups, particularly preferred being primary monoamines,

secondary amines H5 having additional carbonylimine-blocked primary amino groups, obtained by reaction of amines H51 having at least one primary amino group and at least one secondary amino group with carbonyl compounds H52 which have an aldehyde or ketone carbonyl group, and optionally,

hydroxy-functional secondary amines H6 having at least one secondary amino group and at least one hydroxyl group, and

optionally, of amines H7 having at least one primary, and at least one tertiary amino group.

The process for the preparation of the hardener H' comprises the following steps:

(a) preparation of a hydrophilically modified epoxy resin by reacting an at least difunctional hy droxypoly oxy alkylene H2 and an at least difunctional epoxide HI in the presence of an acidic catalyst Kl, under heating up to 200 ^° C, preferably from 50 ^° C to 150 ^° C, particularly preferred from 70 ^° C to 110 ^° C,

(b) preparing, in a separate reaction, a carbonylimine H5 from an aliphatic amine H51 having at least one primary amino group, and at least one secondary amino group in its molecule, and a blocking agent H52 for primary amino groups, which blocking agent has preferably carbonyl groups of a ketone or of an aldehyde, to form a ketimine or an aldimine H5,

(c) adding to the product of step (a), a catalyst (preferably triphenyl phosphine), and optionally, the hydroxyaromatic compounds H3, where in the reaction of these, a part of the epoxide groups is consumed. Optionally, an inert solvent (preferably an aliphatic etheralcohol) is added, and the product H5 from step (b) is added and reacted until the secondary amino groups of H5 have been consumed,

(d) the aliphatic amines H43 and optionally, the secondary hydroxyamines H6, are then added, separately, in any sequence, or together, and the reaction is continued until all amino groups of H43 and all secondary amino groups of H6 have been consumed. Then, in a further preferred embodiment, primary-tertiary amines H7 are added and the reaction is conducted until all epoxide groups have been consumed,

(d') further diepoxides HI are optionally added after addition of either or both of H6 and H7 if needed to consume ah remaining primary or secondary amino groups,

(e) the reaction product of step (d) is then neutralised by addition of an organic or inorganic acid, and water is added to the neutralised mixture to decompose the ketimine groups, under regeneration of primary amino groups, and of the blocking agent which is then distilled off together with the optional etheralcohol solvent. The amount of free amino groups in the resulting dispersion can be adjusted by addition of monofunctional epoxides H8.

It has been found, in the investigations upon which the present invention is based that the specific amount of substance n( HA) / m _s of beta-hydroxyamine structures derived from component H43 in the hardener H', based on the mass of solids m _s in the aqueous hardener dispersion, is preferably from 0.2 mol/kg to 2 mol/kg, particularly preferably, from 0.25 mol/kg to 1.5 mol/kg, and especially preferred, from 0.28 mol/kg to 1.3 mol/kg. When using lower specific amounts of substance, the increase in adhesion between the epoxy-resin based primer layer and the coating applied onto the said primer layer is not manifest, and when using higher specific amounts of substance, adhesion of the said primer layer to the metal substrate is impaired. Hardeners Derived Comprising Moieties Derived from Fatty Alcohols (Embodiment 3)

One further possibility of incorporation of long-chain alkyl groups to prepare a hardener composition H' is incorporation of fatty alcohols into these hardener compositions H'. Fatty alcohols, for the purpose of this invention, are selected from the group consisting of monofunctional fatty alcohols, difunctional fatty alcohols, and multi-functional fatty alcohols which comprise those with three or more hydroxyl groups, preferably having from four to twenty-five carbon atoms. Incorporation is achieved by reaction of a fatty alcohol with a molecule having an epoxide group, and a further group which reacts with the alcoholic hydroxyl group; the molecule of choice due to its commercial availability being epichlorohydrin. Glycidylethers of fatty alcohols made by such process can be used during the process to prepare a modified hardener composition H' which provides epoxy-based coating compositions that exhibit very good adhesion to substrates, particularly metal substrates, and also show improved interlayer adhesion for further coatings which are applied upon this epoxy-based coating layer. This embodiment of the invention therefore relates to hardeners H' for epoxy resins, which hardeners H' are reaction products of

at least difunctional epoxides HI,

at least difunctional hydroxypolyoxyalkylenes H2,

optionally, at least difunctional hydroxyaromatic compounds H3,

at least monofunctional linear or branched or cyclic aliphatic glycidyl ethers H44 having from four to twenty-five carbon atoms in the aliphatic (alkyl) group, and at least one epoxide group, which alkyl glycidyl ethers H44 are incorporated into the hardeners H' by reaction of its epoxide group during the advancement reaction with aromatic polyols,

secondary amines H5 having additional carbonylimine-blocked primary amino groups, obtained by reaction of amines H51 having at least one primary amino group and at least one secondary amino group with carbonyl compounds H52 which have an aldehyde or ketone carbonyl group, and optionally,

hydroxy-functional secondary amines H6 having at least one secondary amino group and at least one hydroxyl group, and optionally, of amines H7 having at least one primary, and at least one tertiary amino group.

The process for the preparation of the hardener H' comprises the following steps:

(a) preparation of a hydrophilically modified epoxy resin by reacting an at least difunctional hydroxypolyoxyalkylene H2 and an at least difunctional epoxide HI in the presence of an acidic catalyst Kl, under heating up to 200 ^° C, preferably from 50 ^° C to 150 ^° C, particularly preferred from 70 ^° C to 110 ^° C,

(b) preparing, in a separate reaction, a carbonylimine H5 from an aliphatic amine H51 having at least one primary amino group, and at least one secondary amino group in its molecule, and a blocking agent H52 for primary amino groups, which blocking agent has preferably carbonyl groups of a ketone or of an aldehyde, to form a ketimine or an aldimine H5,

(c) adding to the product of step (a), a catalyst (preferably triphenyl phosphine), and optionally, the hydroxyaromatic compounds H3, where in the reaction of these, a part of the epoxide groups is consumed. Optionally, an inert solvent (preferably an aliphatic etheralcohol) is added, and the product H5 from step (b) is added and reacted until the secondary amino groups of H5 have been consumed,

(d) the aliphatic amines H43 and optionally, the secondary hydroxyamines H6, are then added, separately, in any sequence, or together, and the reaction is continued until all amino groups of H43 and all secondary amino groups of H6 have been consumed. Then, in a further preferred embodiment, primary-tertiary amines H7 are added and the reaction is conducted until all epoxide groups have been consumed,

(d') further diepoxides HI are optionally added after addition of either or both of H6 and H7 if needed to consume all remaining primary or secondary amino groups,

(e) the reaction product of step (d) is then neutralised by addition of an organic or inorganic acid, and water is added to the neutralised mixture to decompose the ketimine groups, under regeneration of primary amino groups, and of the blocking agent which is then distilled off together with the optional etheralcohol solvent. The amount of free amino groups in the resulting dispersion can be adjusted by addition of monofunctional epoxides H8.

The alkylglycidylethers H44 can be added in step (a) and/or in step (c) and/or in step (d').

It has been found, in the investigations upon which the present invention is based that the specific amount of substance n(HE) / m _s of beta-hydroxyether structures derived from component H44 in the hardener H', based on the mass of solids m _s in the aqueous hardener dispersion, is preferably from 0.2 mol/kg to 2 mol/kg, particularly preferably, from 0.25 mol/kg to 1.5 mol/kg, and especially preferred, from 0.28 mol/kg to 1.3 mol/kg. When using lower specific amounts of substance, the increase in adhesion between the epoxy-resin based primer layer and the coating applied onto the said primer layer is not manifest, and when using higher specific amounts of substance, adhesion of the said primer layer to the metal substrate is impaired.

Hardeners Derived Comprising Moieties Derived from Alkylphenols (Embodiment 4) Alkylphenols can be introduced into a hardener component for epoxy resins in two ways: they can be reacted via a Mannich reaction of alkylphenols with formaldehyde and amines, to form alkylphenylamines H45 which can be incorporated into a hardener component during its synthesis, or in the form of novolaks H46 made via reaction of alkylphenols with formaldehyde with acidic catalysts, which novolaks can be reacted with epoxide-functional compounds in a Taffy process with epichlorohydrin, or in an advancement process, also called "chain extension process" or "fusion process" in the literature, to form epoxide compounds with a high functionality.

According to embodiment 4, hardeners H' for epoxy resins are provided which are reaction products of

at least difunctional epoxides HI,

at least difunctional hydroxypolyoxyalkylenes H2,

optionally, at least difunctional hydroxyaromatic compounds H3,

alkylphenylamines H45 having from four to twenty-five carbon atoms in the alkyl group, and a phenolic hydroxyl group, a secondary amino group, and optionally, also further amino groups if a diamine or multifunctional amine has been used in the Mannich reaction of phenol, amine, and formaldehyde, which alkylphenylamines H45 are incorporated into the hardeners H' by reaction of its phenolic hydroxyl group, and/or its amino group during the advancement reaction with epoxides,

secondary amines H5 having additional carbonylimine-blocked primary amino groups, obtained by reaction of amines H51 having at least one primary amino group and at least one secondary amino group with carbonyl compounds H52 which have an aldehyde or ketone carbonyl group, and optionally,

hydroxy-functional secondary amines H6 having at least one secondary amino group and at least one hydroxyl group, and

optionally, of amines H7 having at least one primary, and at least one tertiary amino group.

The process for the preparation of the hardener H' of embodiment 4 comprises the following steps:

(a) preparation of a hydrophilically modified epoxy resin by reacting an at least difunctional hydroxypolyoxyalkylene H2 and an at least difunctional epoxide HI in the presence of an acidic catalyst Kl, under heating up to 200 ^° C, preferably from 50 ^° C to 150 ^° C, particularly preferred from 70 ^° C to 110 ^° C,

(b) preparing, in a separate reaction, a carbonylimine H5 from an aliphatic amine H51 having at least one primary amino group, and at least one secondary amino group in its molecule, and a blocking agent H52 for primary amino groups, which blocking agent has preferably carbonyl groups of a ketone or of an aldehyde, to form a ketimine or an aldimine H5,

(c) adding to the product of step (a), a catalyst (preferably triphenyl phosphine), and optionally, the hydroxyaromatic compounds H3, where in the reaction of these, a part of the epoxide groups present in this step is consumed. Optionally, an inert solvent (preferably an aliphatic etheralcohol) is added, and the product H5 from step (b) is added and reacted until the secondary amino groups of H5 have been consumed,

(d) the alkylphenylamines H45 and optionally, the secondary hydroxyamines H6, are then added, separately, in any sequence, or together, and the reaction is continued until all amino groups of H45 and all secondary amino groups of H6 have been consumed. Then, in a further preferred embodiment, primary-tertiary amines H7 are added and the reaction is conducted until all epoxide groups have been consumed,

(d') further diepoxides HI are optionally added after addition of either or both of H6 and H7 if needed to consume all remaining primary or secondary amino groups,

(e) the reaction product of step (d) is then neutralised by addition of an organic or inorganic acid, and water is added to the neutralised mixture to decompose the ketimine groups, under regeneration of primary amino groups, and of the blocking agent which is then distilled off together with the optional etheralcohol solvent. The amount of free amino groups in the resulting dispersion can be adjusted by addition of monofunctional epoxides H8.

It is also possible to add the alkylphenylamines H45 already in step (c), together with, or separately from, the hydroxyaromatic compounds H3. Addition in step (c) canbe made instead of addition in step (d), or H45 can be added in both steps (c) and (d). If an amine with only secondary amino groups is used in the Mannich reaction to prepare the alkylphenylamine H45, obviously, only reaction of the phenolic hydroxyl group during the advancement reaction is possible.

Incorporation of a novolak H46 with long chain alkyl groups may be made by adding H46 in step (a), in step (c), or in step (d').

It has been found, in the investigations upon which the present invention is based that the sum of the specific amount of substance n(HA) / m _s of beta-hydroxyamine structures derived from component H45 in the hardener H', based on the mass of solids m _s in the aqueous hardener dispersion, and of the specific amount of substance n(APA) / m _s of alkylphenylamine bound to the hardener H' is preferably from 0.2 mol/kg to 2 mol/kg, particularly preferably, from 0.25 mol/kg to 1.5 mol/kg, and especially preferred, from 0.28 mol/kg to 1.3 mol/kg. The same limits apply to the specific amount of substance of structures derived from long chain alkyl groups of the novolak H46 in the hardener H'. When using lower specific amounts of substance, the increase in adhesion between the epoxy-resin based primer layer and the coating applied onto the said primer layer is not manifest, and when using higher specific amounts of substance, adhesion of the said primer layer to the metal substrate is impaired.

Further Embodiments of Hardeners Comprising Long Chain Alkyl Moieties

Further compounds can also be used which have comprising long chain alkyl groups and at least one epoxide functional group, which include

fatty acid glycidyl esters H46 which are esters of glycidol and fatty acids selected from the group consisting of monofunctional fatty acids, difunctional fatty acids, and multi functional fatty acids which comprise those with three or more acid groups (embodiment 5), and which are made as mixtures from unsaturated fatty acids by heating in the presence of a catalyst,

N-glycidylamines H47m which are selected from the group consisting of N-glycidyl- amines made from secondary monofunctional fatty amines where one of the aminic hydrogen atoms is substituted with lower alkyl groups having from one to four carbon atoms , N,N-diglycidylamines made from primary monofunctional fatty amines, N,N'- diglycidylamines made from secondary difunctional fatty amines where one of the aminic hydrogen atoms of each one of the nitrogen atoms N and N' is substituted with lower alkyl groups having from one to four carbon atoms, N,N,N',N'- tetraglycidylamines made from difunctional primary fatty amines, and (multi-)N- glycidylamines made from primary or secondary multi-functional fatty amines which comprise those with three or more amino groups, wherein the amino groups of the fatty amines are primary or secondary amino groups, where optionally, one of the aminic hydrogen atoms of each one of the nitrogen atoms is substituted with lower alkyl groups having from one to four carbon atoms (embodiment 6), and N-glycidylamides H47d made from amides of fatty acids, particularly those made from fatty acids, or naturally occurring mixtures of these, and amines having at least one primary amino group, such as aliphatic monoamines having from preferably from four to twenty carbon atoms in the alkyl group which is linear or branched or cyclic, preferably n- butylamine, n-hexylamine, 2-ethylhexylamine, n-decylamine, n-dodecylamine, and stearylamine, diamines or polyamines, particularly ethylene diamine and its oligomers, preferably diethylene triamine, and triethylene tetramine, or alpha, omega-diamino- oligo- or poly-oxyethylene glycols, and homologues thereof, particularly the propylene analogues such as 1,2-diaminopropane, dipropylene triamine, tripropylene tetramine, and alpha, omega-diamino-oligo- or poly-oxy-propylene glycols, where at least one of the remaining secondary amino groups or a secondary amide group is converted to an N-glycidylamide structure by reaction of the secondary amino or amide group with e.g., epichlorohydrin (embodiment 7),

glycidyl ethers of fatty alcohols H48 which are selected from the group consisting of monofunctional fatty alcohols, difunctional fatty alcohols, and multi-functional fatty alcohols which comprise those with three or more hydroxyl groups, or mixtures of these, which also include, e.g., glycidyl ethers prepared from reacting a fatty acid with a dialkylol amine, such as di-n-propanolamine, diisopropanolamine, or diethanolamine, to make an N-alkanoyl-alkylolamide and subsequent formation of a glycidylether by reaction with, e.g. epichlorohydrin (embodiment 8), and

epoxidised esters of unsaturated fatty acids H49 with alcohols having from one to thirty carbon atoms, epoxidised oils which are triglycerides of unsaturated fatty acids, or mixtures of these (embodiment 9).

In embodiments 5, 6, 7, 8, and 9, reaction steps (a) and (b) are conducted as described supra, and the epoxide-functional compounds of embodiments 5, 6, 7, 8, or 9, or mixtures of any two, three, four, or all five of glycidyl esters of fatty acids H46, N-glycidylamines H47m, N- glycidylamides H47d, glycidyl ethers of fatty alcohols H48, and epoxidised esters of unsaturated fatty acids H49 are added during the advancement reaction steps (c) and/or (d), together with, or separately from, the other additions during this step, wherein monofunctional epoxide compounds will form an end group of the resulting chain-extended resin, while compounds having two or more epoxide functionalities will form a part of the polymeric chain, or of a branch if the functionality is more than two. Care has to be taken to limit amounts of compounds having a functionality of more than two to avoid gelation.

A further embodiment of the invention is the use of phenalkamines in the hardener composition H. Phenalkamines are reaction products made from cardanol (a phenol with a long-chain unsaturated alkyl group im meta position to the phenolic hydroxyl group, mostly C ₁₅ H ₂₇ , obtained from distillation of cashew nutshell liquid), formaldehyde, and selected amines or polyamines, such as diethylenetriamine, meta-xylylene diamine or 1,3-bis- aminomethyl-cyclohexane via a Mannich reaction. These phenalkamines as disclosed in already comprise long chain alkyl groups containing from one to three olefinic unsaturations, therefore these have to be accounted for in the degree of modification with additional long chain alkyl groups according to the present invention.

Polyamides are one of the largest volume epoxy curing agents used. They are prepared by the reaction of dimerised and trimerised vegetable oil fatty acids with polyamines, preferably, oligomeric polyalkyleneamines such as diethylene triamine, triethylene tetramine, tetraethylene pentamine etc. Dimer fatty acid is made by a Diels-Alder reaction between 9,12- and 9,11-lino leic acids. Subsequent reaction with diethylenetriamine or other suitable multifunctional amines yields the amine-terminated polyamides. When phenalkamines are used to at least partly replace the mentioned amines in the polyamides, the so-called phenalkamides are the result of this reaction. Their properties as epoxy curing agents he between those of phenalkamines and polyamides. They are available in a range of molar mases and compositions. These polyamides and phenalkamides already comprise long chain alkyl groups, therefore these have to be accounted for in the degree of modification with additional long chain alkyl groups according to the present invention.

The polyamides, phenalkamines and phenalkamides are also useful as hardener compositions H, alone or in mixture with aminic curing agents. These mixtures allow to tailor the desired adhesion, under conservation of the hydrophilic character of the hardener composition H which allows to use the hardener composition H as emulsifier for non-hydrophilic epoxy resins E in aqueous coating compositions, particularly for primers.

Preparation of Solvent-Borne Coating Compositions

Epoxy resins for coatings are converted into solid, infusible, and insoluble three-dimensional thermoset networks for their uses by curing with crosslinkers, also referred to as hardeners or curing agents. The curing agent is selected dependent upon the requirements of the application process techniques, pot life, cure conditions, and desired ultimate physical properties. The type and quantity of curing agent employed determines the types of chemical bonds formed upon curing, and the degree of crosslinking achieved. These, in turn, determine the mechanical properties, heat resistance, chemical resistance, and electrical properties, of the cured coating compositions.

As epoxy resins contain two chemically reactive functional groups: epoxide or oxirane groups and hydroxyl groups. Low molar mass epoxy resins, such as liquid epoxy resins, are considered difunctional epoxy monomers or prepolymers and are generally cured by curing agents that react with the epoxide group under ring opening. Higher molar mass (solid) epoxy resins have a lower specific amount of substance of epoxide groups, whereas the specific amount of substance of hydroxyl groups increases; these can therefore be cured by reaction of both the epoxide groups, and the hydroxyl groups.

Epoxy resins and curing agents are usually mixed prior to use, i. e., application onto the substrate, as a two-pack system.

The curing agents usually used for solvent-borne or reactively-diluted epoxy resins offer little possibility for modification as this goes along with enlarging the molecules and thereby diluting the reactive groups of the curing agents, and also impairing the needed mobility in diffusion reactions. Therefore, modification is usually done on the epoxy resins, in this case.

Modified Epoxide-Functional Resins E' Comprising Long Chain Alkyl Groups

Long-chain alkyl groups can be incorporated into epoxide-functional resins by incorporation of compounds comprising long-chain alkyl groups as mentioned under embodiments 1, 3, 4 (only compounds H46), and 5 to 9. These compounds are admixed to an at least difunctional epoxide compound HI, or to a hydrophilically modified epoxy resin as prepared according to step (a) supra, or they are subjected to an advancement reaction as described in the first part of step (c) supra, either together with HI, or separately from HI, and the separately advanced epoxy resin are then mixed. Advancement of a mixture of HI and any one or more than one of the compounds comprising long-chain alkyl groups as mentioned under embodiments 1, 3, 4 (only compounds H46), and 5 to 9 is preferred as this leads to a homogeneous mixture. These kinds of modification can be used for both solvent-borne and reactively diluted epoxy resins, as well as for water-based epoxy resins.

Preparation of Water-Borne Coating Compositions

In preparing water-borne two-pack coating compositions, an epoxy resin E in liquid form, optionally together with reactive diluents, thereby avoiding an additional step of aqueously dispersing the epoxy resin component of the two-pack coating composition, is added to the aqueous dispersion of a hardener H, under stirring. It is, however, also possible to add an aqueous dispersion of the epoxy resin E to the aqueous dispersion of the hardener H, under stirring.

The epoxy resin E is any liquid epoxy resin, such as the grades known as type 1 liquid epoxy resins which are based on bisphenol A diglycidylether (BADGE, molar mass 340.4 g/mol, melting temperature 43 ^° C) having a mass average molar mass of from 350 g/mol to 380 g/mol and are liquid at room temperature (25 ^° C), or liquid mixtures of higher molar mass epoxy resinsbased on BADGE which themselves are solid atroom temperature, with reactive diluents which are monofunctional such as alkyl phenol glycidylethers, particularly cresylglycidylether, p-tert-butylphenylglycidylether, and glycidylethers and glycidylesters made from cashew nuts shell liquid, long chain alkyl glycidylethers and glycidylesters, particularly glycidyl- neodecanoate and C ₆ - to C ₁₈ -alkyl glycidylethers whereof 2-ethylhexyl glycidylether and mixtures of glycidylethers of C ₈ - to C ₁₀ -alcohols or of C ₁₂ - to C ₁₄ -alcohols are mentioned, or reactive diluents that are difunctional such as butanediol diglycidylether, hexanediol diglycidylether, neopentylglycol diglycidyl-ether, cyclohexanedimethanol diglycidylether, dipropyleneglycol digylcidylether, and polypropyleneglycol diglycidylether, or having higher functionality such as trimethylolpropane trigylcidylether and pentaerythritol tetraglycidyl- ether. An aqueous dispersion of the epoxy resin E can be made by chemically incorporating oxyethylene homopolymers or copolymers into the epoxy resin, or by adding emulsifiers F. The emulsifier F is preferably a non-ionic emulsifier. Alternatively, a combination of a non-ionic emulsifier F with an ionic emulsifier may be used. The emulsifier F is preferably a non-ionic emulsifier where the hydrophilic portion comprises polyoxyalkylene moieties having two or three carbon atoms in the alkylene group, or a combination of a nonionic and an anionic emulsifier.

Non-ionic emulsifiers which can be used for this invention are preferably selected from the group consisting of monoesters of glycerol and fatty acids, partial esters of polyhydric alcohols such as sugar alcohols, with fatty acids, where esters are referred to as "partial ester" if at least one, preferably at least two ethoxylated fatty acids, ethoxylated fatty acid amides, ethoxylated fatty alcohols, ethoxylated alkyl phenols, and propoxylated analogues of these as well as mixed ethoxylated and propoxylated analogues of these, are present in the partial ester. It is also possible to react oligomeric or polymeric oxyalkylenediols with at least two carbon atoms in the alkylene group with diacids, thereby converting the hydroxyl groups to acid groups which can the be reacted with epoxide-functional oligomers or polymers to form molecules having hydrophilic portions derived from the polyoxyalkylene diol and hydrophobic portions derived from the epoxide-functional oligomers or polymers. Particularly good emulsifying properties are obtained when using low to intermediate molar mass epoxy resins as epoxide-functional oligomers or polymers.

Anionic emulsifiers which can be used for this invention are preferably selected from the group consisting of fatty acid salts, alkanolsulphates, fatty alcohol isethionates, alkali alkanesulphonates, alkylbenzene sulphonates, sulphosuccinic acid esters, alkanol ethoxylate- sulphates, and alkanol ethoxylate-phosphates. Cationic emulsifiers which can be used for this invention are tetraalkyl ammonium halogenides where at least one of the alkyl groups has from eight to forty carbon atoms, while the others preferably have from one to eight carbon atoms, quaternary carboxymethylated ammonium salts, and long chain alkyl substituted pyridinium salts such as lauryl pyridinium chloride. Preferred are combinations of anionic and non-ionic emulsifiers, and combinations of cationic and non-ionic emulsifiers.

Non-ionic emulsifiers are preferably selected from those comprising polyoxyalkylene moieties having two or three carbon atoms in the alkylene group or combinations thereof. Examples of such emulsifiers are block co-polymers of ethylene oxide and propylene oxide.

Non-ionic emulsifiers F are preferably selected from those having a weight average molar mass M _w of at least 3000 g/mol, more preferably of at least 6000 g/mol, and most preferably of at least 10000 g/mol.

If nonionic emulsifiers are used alone, particularly preferred are non-ionic emulsifiers made by reaction of low molar mass epoxy resins which are preferably derived from bisphenol A or bisphenol F or bisphenol S or their mixtures, preferably having two epoxide groups per molecule, and from one to ten repeating units, and dihydroxy polyoxyalkylene s having two or three carbon atoms in the alkylene group, viz., dihydroxy polyoxyethylene or dihydroxy polyoxypropylene, or dihydroxy-copolymers having both C ₂ - and C ₃ -alkylene groups in their polymer chain. This reaction is preferably catalysed by a Lewis acid such as boron trifluoride, or complexes of boron trifluoride with Lewis bases such as with ammonia or trimethylamine. A preferred catalyst is made by reacting bisphenol A diglycidylether with dihydroxy polyoxyethylene where the latter has a number average molar mass of from 1 kg/mol to 20 kg/mol, particularly preferred of from 2 kg/mol to 10 kg/mol. Mixtures of two or more different dihydroxy polyoxyalkylenes and/or mixtures of two or more different low molar mass epoxy resins may also be used.

The use of an aqueously dispersible flexibilised epoxy resin is preferred, particularly in the form of its aqueous dispersion, wherein flexibilisation is preferably made by incorporating aliphatic polyesters or polyethers into the polymer chain of the epoxide resins, such as polyesters of adipic acid and butanediol, or polyethers such as oligo- and poly-ethylene glycol, oligo- and poly-propylene glycol, and oligo- and poly-butylene glycol, as well as co-oligomers or copolymers of these. These aliphatic polyesters or polyethers are preferably incorporated into the epoxy resins by co-reacting with their glycidylester or ethers in an advancement reaction.

Coating compositions or paints based on any combination of an epoxy resin component E as described supra, and the hardener composition H, wherein, according to the invention, at least one modified epoxy resin E* of this invention and/or at least one modified hardener H* of this invention is present in the combination, can be used to form primer coatings on any substrate. The are usually formulated by adding usual additives, particularly anti-foaming agents, levelling agents, wetting agents, biocides, light and UV protection agents such as those based on hindered amines, benzophenones and benzotriazoles, and rheology modifiers such as thickeners. Pigmented coating compositions canbe prepared by grinding the pigment together with a wetting agent, and optionally, further additives such as antisettling agents, as well as those additives mentioned supra, and further optionally, fillers and colourants, in the aqueous dispersion of the adduct of this invention, adding further additives such as preservatives, coalescing agents, and the epoxy resin, either in aqueous dispersion, or in liquid form, optionally together with a reactive diluent, and optionally a further amount of the aqueous dispersion of the adduct of this invention, and adjusting the mixture to the desired viscosity by addition of water. The clear-coat paints or pigmented coating compositions can be applied to the substrates e.g. by spraying, rolling, dipping, flooding, or brushing. These coating compositions are particularly useful as primer coating layers, with preference for use on metals, particularly on base metals such as steel, for corrosion protection, and also on mineral substrates such as concrete or tiles.

Top Coat Coating Compositions

The topcoat coating compositions T which are not aqueously dispersed, and optionally, solvent- borne, comprise combinations of resins and adapted crosslinkers. Most resins presently used in solvent-borne, or solvent-less coating compositions have hydroxyl groups as functional groups, and appropriate crosslinkers are mostly multifunctional isocyanates, with isocyanate groups in blocked or free form, or amino resins, mainly melamine resins. The preferred hydroxyl group-containing polymers or resins are mostly solvent-borne alkyd resins, or solvent-borne acrylic resins which also include acrylic or methacrylic copolymers, styrene being frequently used as one of the comonomers.

In EP 3 085 748 Al, a fast-curing anti-corrosive system is disclosed which comprises a primer layer based on at least one epoxy resin, and at least one amine curing agent, and a topcoat layer made from at least one crosslinkable component T1 having at least two acidic C-H protons in a molecule, referred to as "Michael donor", and at least one component T2 referred to as "Michael acceptor" having at least two olefinically unsaturated groups in its molecule that are activated by electron- withdrawing groups.

Coating compositions based on at least one crosslinkable component T1 having at least two acidic C-H protons in a molecule, and at least one component T2 having at least two olefinically unsaturated groups can preferably also be used to provide a topcoat on a primer layer made with epoxy resins E, and the hardener or curative H according to this invention. The Michael addition reaction which provides carbon-carbon bonds between the said components T1 and T2 is usually catalysed by a strong base T3. Examples of such coating compositions are disclosed in EP 2 374 836 Al, where a substituted carbonate salt

X ⁺ O - CO - O - R

is used as latent base catalyst, X ⁺ being a cation, and R is a hydrogen atom, or an alkyl, aryl, or aralkyl group. They show the same improvement in interlayer adhesion to the primer layer that has been found in topcoats made from other solvent-borne coating compositions.

Useful oligomeric or polymeric Michael donor compounds T1 for the topcoat coating compo sition used with the primers of this invention are polyesters, polyamides, polyurethanes or polyacrylates comprising activated methylene or methine groups in alpha-position to electron withdrawing groups such as carbonyl, carboxyl, carboxylate, cyano, nitro, sulfo, or sulfoxide groups. Preferred polymers comprise building blocks derived from malonic acid or acetoacetic acid, such as copolyesters made, e.g., from neopentylglycol, esters of malonic acid, and 1,2- cyclohexanedicarboxylic acid anhydride, or copolymers from acrylic esters having hydroxy functional groups with other comonomers such as methylmethacrylate and styrene, where at least a part of the hydroxyl groups averaging to at least two of the hydroxyl groups in a molecule is esterified with acetoacetic acid or derivatives thereof.

Useful Michael acceptors T2 are esters of acrylic acid or homologues thereof with at least difunctional linear or branched aliphatic hydroxy compounds or hydroxyether compounds having from two to twenty carbon atoms, such as diethyleneglycol diacrylate, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, ditrimethylolpropane tetraacrylate, and dipenta- erythritol penta-/ hexaacrylate mixture.

A preferred basic catalyst T3 as described in EP 2 374836 Al, and further in WO 2011/124663 Al, WO 2011/124664 Al, and WO 2011/124665 Al, is a carbonate salt of the formula

R-O-CO-O M ⁺ ,

where R is H (forming a hydrogen carbonate), or linear or branched alkyl from one to twenty carbon atoms, or aralkyl from seven to twenty-five carbon atoms, (both forming ester- carbonates), M ⁺ is an alkali cation, an earth alkali cation, an organic ammonium cation R' ₄ N ⁺ , or an organic phosphonium cation R" ₄ P ⁺ , where the groups R' and R" are linear or branched or cyclic alkyl groups having from one to ten carbon atoms, such as methyl, ethyl, isopropyl, n-butyl, 2-ethylhexyl, cyclohexyl, and stearyl, or aralkyl from seven to twenty-five carbon atoms, such as benzyl and phenethyl, and may be different from each other in one cation, such as methyltriethyl ammonium, trihexyl tetradecyl phosphonium, triisobutyl methyl phosphonium, and octadecyl trioctyl phosphonium.

Other basic catalysts that accelerate the reaction between Michael donor compounds T1 and Michael acceptor compounds T2 are compounds T41 which are salts of alkali metal cations or organic ammonium cations or organic phosphonium cations, and anions which are preferably carbanions derived from cyanoacetates such as ethylcyanoacetate (pK _a = 9.0), 1,3-diketones such as acetylacetone (pK _a = 8.95), 1,3-cyclohexanedione (pK _a = 5.3), and 5,5-dimethyl-l,3- cyclohexanedione (pK _a = 5.23) and nitroalkanes such as nitromethane (pK _a = 10.2), nitroethane (pK _a = 8.5), and 2-nitropropane (pK _a = 9.98). These can preferably be combined with one or more optional components T42 which have one or more acidic Q-H groups wherein Q is selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and carbon, the Q anion being a Michael addition donor reactable with component T2, wherein the pKa(T42) of the Q-H group in component T42 is more than two lower than the pK _a (Tl) of the first proton of component T1 and being lower than 10.5, and the ratio n( H, T42) / n( C , T41) of the amount of substance of acidic Q-H groups in component T42 to the amount of substance of the carbanion in component T41 is between 0.01 and 50. T42 is preferably an organic amine compound having at least one >NH group where the pK _a value (negative decadic logarithm of the ionisation constant K _a ) for the reaction >N-H >N + H ⁺ is between 4 and 14. These systems are disclosed in WO 2014/166880 Al. Among the preferred organic nitrogen compounds are succinimide, 1,2,4-triazole, and 1,2,3-benzotriazole.

A further catalyst system T5 for crosslinking by Michael addition using components T1 (Michael donor) and T2 (Michael acceptor) under formation of C-C bonds has been disclosed in WO 2018/005 077 A1 which is a dormant carbamate initiator of formula wherein n is an integer equal to, or greater than, one, and A ⁿ⁺ is a cationic species or a polymer, with the proviso that A ⁿ⁺ is not H ⁺ , and optionally, further comprises ammonium carbamate, H R^R^NT O - (CO) NR'^R" ² , wherein each R ¹ , R ² , R' ¹ , R' ² , R" ¹ and R" ² is independently selected from the group consisting of a hydrogen atom, and a linear or branched, substituted or unsubstituted, alkyl group having from one to twenty-two carbon atoms.

Further constituents that can be present in topcoat coating composition T which crosslinks via the Michael addition are light and UV stabilisers, pigments, dispersing agents, flow modifiers, antifoaming agents, matting agents, solvents, and anti-sagging agents. Combinations of Primer Coating Compositions and Top Coat Coating Compositions

The following combinations of epoxy resins and curing agents have been made in the investigations leading to the present invention, where each of the epoxy resin systems as discussed in the introductory portion of this application has been combined with each of the curing agents mentioned:

Table 1 Combinations of epoxy resins and curing agents

(This table discloses individually all combinations of the prior art, as well as all modifications with long chain alkyl groups)

The abbreviations A to T are applied as used in the discussion of the background of the invention. Primer coating layers were made from any of these combinations, denoted as "na" meaning no addition, and also these combinations where modifications have been made by adding a modified epoxy resin E* as discussed supra to any of these combinations, thereby obtaining a combination "+E* ",

adding a modified curing agent H* as discussed supra to any of these combinations, thereby obtaining a combination "+H* "

- adding a modified epoxy resin E* as discussed supra and a modified curing agent H* as discussed supra to any of these combinations, thereby obtaining a combination "+E* + H* " . The adhesion of these primer coating layers was tested with topcoats made according to example 4, using catalyst C4 of EP 2374836 Al, according to example 8 of WO 2014/166880 Al, and according to inventive example 4 of WO 2018/005077 Al, wherein all combinations listed in Table 1 were combined with any one of the three top-coats according to the examples mentioned. Improved intercoat adhesion as measured in the cross-cut adhesion test was noted for all of these combinations where at least one of the epoxy resin and of the curing agent was modified by addition of an appropriate quantity of modified epoxy resin E', or of a modified curing agent H', or of both modified epoxy resin E', or of a modified curing agent H', wherein the specific amount of substance of long chain alkyl groups in the epoxy resin component and in the curing agent component was limited to from 0.2 mol/kg to 2 mol/kg, as discussed supra, in each case.

The two-pack epoxy coating compositions of this invention are useful on mineral substrates such as concrete, stone, and plaster, but can also be used with good success on metal substrates. They provide higher gloss and gloss retention, fast hardness development, good adhesion, and improved mechanical and chemical resistance. Primer coatings formed from the two-pack coating composition comprising the hardener H* and the epoxy resin E* are particularly valuable as primer coatings for base metals to minimise or prevent corrosion of these metal substrates.

It has been found in the experiments underlying the present invention that the interlayer adhesion of coating films made not from aqueously dispersed coating compositions, but from solvent-borne compositions or solventless coating compositions to a coating film prepared from the two-pack combination of epoxy resins E* and the hardener H* according to the present invention is also improved with regard to a similar two-pack combination that does not comprise long chain alkyl moieties.

Physicochemical Parameters

In the specification, and also in the examples, the following parameters have been used to describe physicochemical properties of the compounds and substances: The mass fraction of solids w _s was determined by drying a sample B which comprises a substance which is solid at room temperature (23 ^° C) and is dissolved in a solvent, or disper sed in an aqueous system, with the sample mass of 1 g at 125 ^° C for one hour, and stating the ratio w _s = m _RA / m _B of the mass m _Rd of the residue Rd after drying, and the mass m _B of the sample B taken. Strength of a solution is stated as the mass fraction iv _B of solute B in the solution, calculated as the ratio m _B / m _s of the mass m _B of solute B and the mass m _s of solution S.

The specific amount of substance of epoxide groups in a sample was determined in the usual way by titration of the sample with tetraethylammonium bromide and perchloric acid in glacial acetic acid, as described by R. R. Jay, Anal. Chem. 36, (1964), pages 667 and 668, and stated as the ratio n(EP) / m _B of the amount of substance n(EP) of epoxide groups present in a sample B, and the mass m _B of that sample B; its customary SI unit is "mol/kg".

The acid number or acid value is defined, according to DIN EN ISO 3682 (DIN 53402), as the ratio m _KOH / m _B of that mass m _KOH of potassium hydroxide which is needed to neutralise the sample B under examination, and the mass m _B of this sample B, or the mass m _B of the solids in the sample in the case of a solution or dispersion; its customary unit is "mg/g".

The amine number or amine value is defined, according to DIN EN ISO 3771 (DIN 16 945 , item 5.6; DIN 53 176) as the ratio w _Am = m _KOH / m _B of that mass m _KOH of potassium hydroxide which needs the same amount of acid for neutralisation as the sample B under examination, and the mass m _B of this sample B, or the mass m _B of the solids in the sample in the case of a solution or dispersion; its customary unit is "mg/g". The specific amount of substance of aminic hydrogen groups in a dispersion, n(NH)/m, is calculated from the titration results by dividing the amount of substance of aminic hydrogen atoms, n(NH), (I. e., two from each of the primary amino groups, and one from each of the secondary amino groups) by the mass m of the dispersion.

Dynamic viscosity of the dispersion was measured in a cone-and-plate rheometer at 23 ^° C and a shear rate of 100 s ^.

The invention is further illustrated by the following examples.

Example 1 Preparation of a Ketimine K1 1030 g (10.0 mol) of diethylene triamine (DETA) and 3000 g (30 mol) of methylisobutyl ketone (MIBK) were charged into a four-necked flask equipped with a mechanical stirrer, a water separator and a gas inlet and heated to reflux under a slight nitrogen flow. When the desired amount of water had been collected after approximately eight hours (360 g = 20.0 mol of water), the excess of MIBK was removed to yield the pure DETA-MIBK-ketimine.

Example 2 Preparation of the Emulsifier El

2546 g (6.7 mol) of bisphenol A diglycidyl ether (BADGE), 450 g (0.3 mol) of polyethylene glycol with an average molar mass of 1500 g/mol, and 941 g of methoxypropanol were charged into a four-necked flask equipped with a mechanical stirrer and heated to 100 ^° C under stirring. When this temperature was reached, 3 g of a borontrifluoride ethylamine complex (BF ₃ -C ₂ H _S -NH ₂ ) were charged into the flask and the mixture was heated to 130 ^° C and maintained at this temperature for two hours until a specific content of epoxide groups of 3.24 mol/kg was reached. All hydroxyl groups of the polyethylene glycol had been consumed in this reaction.

Example 3 Preparation of the Epoxy-Amine Adduct A1 (comparative)

The reaction mixture of Example 2 was cooled to 100 ^° C, and 776 g (3.406 mol) of bisphenol A and 3 g of triphenylphosphine were charged into the reaction flask and subjected to an advancement reaction, wherein the reaction mixture was heated again under stirring to 130 ^° C, and was kept at this temperature for two hours until the specific content of epoxide groups in the reaction mixture had reached 1.27 mol/kg. Then, further 380 g of methoxypropanol were added, and the reaction mixture was cooled to 80 ^° C. At this temperature, 1335 g of the ketimine K1 of Example 1 were added, and the mixture was stirred for twenty minutes. The mixture was then heated to 90 ^° C, 84 g of diethanolamine were added under stirring, and the mixture was held for twenty minutes at 90 ^° C. 10.2 g of dimethylamino-propylamine were then added, and the reaction mixture was heated to 100 ^° C and stirred for two hours. 95 g of BADGE were added to scavenge unreacted free amines, and the mixture was stirred at 100 ^° C for one further hour. After cooling to room temperature (23 ^° C), the mass fraction of solids was determined to be 80 %, and the dynamic viscosity measured at 23 ^° C and a shear rate of 25 s ¹ was 5000 mPa S.

Example 4 Preparation of the Epoxy-Amine Adducts A2 to A4 (according to the Invention)

Example 2 was repeated to prepare the epoxy-amine adducts A2 to A4, where instead of bisphenol A alone, mixtures of bisphenol A and of a dimeric fatty acid mixture were used in the preparation of adducts A2 and A3, and dimer fatty acids alone were used in the preparation of adduct A4, according to the data in the following table 1. The reaction mixture was then subjected to an advancement reaction by heating again under stirring to 130 ^° C, and was kept at this temperature for two hours until the specific content of epoxide groups in the reaction mixture had reached indicated in table 1. m(AP) stands for the mass of solids of the advancement product in the reaction solution.

Table 1 Additions to the Emulsifier of Example 2 in Preparation of the Epoxy-Amine

Adducts A2 to A4, and characteristic value (according to the Invention)

Then, for each of A2, A3, and A4, further 380 g of methoxypropanol were added, and the reaction mixture was cooled to 80 ^° C. At this temperature, 1335 g of the ketimine K1 of Example 1 were added, and the mixture was stirred for twenty minutes. The mixture was then heated to 90 ^° C, 84 g of diethanolamine were added under stirring, and the mixture was held for twenty minutes at 90 ^° C. 10.2 g of 3-dimethylamino-l-propylamine were then added, and the reaction mixture was heated to 100 ^° C and stirred for two hours. 95 g of BADGE were added to scavenge unreacted free amines, and the mixture was stirred at 100 ^° C for one further hour. After cooling to room temperature (23 ^° C), the mass fraction of solids ut _sol = m _soi / m in the solution of the epoxy-amine adduct was determined, m being the mass of that solution, as well as the specific amount of substance of beta-hydroxyester groups, p(bHE) / m _sol , based on the mass of solids m _sol in the epoxy-amine adduct, see table 2.

Table 2 Characteristic values for the epoxy-amine adducts A2 to A4

Example 5 Preparation of Hardener Dispersions D1 to D4

Hardener dispersions were prepared from the epoxy-amine adduct Al, A2, A3, and A4 according to the recipe given in table 3:

Table 3 Preparation and Characteristics of Hardener Dispersions D1 to D4

1: aqueous solution of lactic acid having a mass fraction of lactic acid of 50 %

determined by dynamic laser scattering according to ISO 22412

see definition of physicochemical properties supra

see definition of physicochemical properties supra; the specific amount of substance of aminic hydrogen atoms in a dispersion is calculated as n _s (NH) = n(NH) / m _D where n(NH) is the amount of substance of aminic hydrogen atoms present in the dispersion, and m _D is the mass of the dispersion

5: see definition of physicochemical properties supra The mass as stated in table 3 of epoxy-amine adducts A1 (Ai with i=l) from example 3 and A2 to A4 (Ai with i = 2, 3 and 4, respectively) of example 4 were separately heated to 95 ^° C and neutralised each with 429 g of a 50 % strength solution of lactic acid in water followed by the addition of 6700 g of water as the first portion ("water I"). The solvents methoxypropanol and MIBK which latter was split off in the cleavage of the ketimine were distilled off under reduced pressure of 100 hPa at 60 ^° C. When the distillation of solvent had ceased, 821 g of cresyl glycidyl ether as reactive diluent ("RD") were added to the dispersion, and the mixture was stirred for two hours. The mass fraction of solids of the dispersion was adjusted by addition of a further portion of water ("water II") to 35 % (dispersion Dl) and 40 % (dispersions D2, D3, and D4). The median of the particle size distribution was determined by dynamic light scattering using a "Zetasizer nano" (Malvern Instruments Ltd.). The other characteristics were determined as explained supra. Hardener dispersions D2 to D4 are according to the invention, and Dl is a comparative example.

Example 6 Preparation of Pigmented Primer Coating Compositions

A pigment paste was prepared according to the following recipe:

88.5 g of deionised water were charged whereto 30 g of a nonionic polymeric wetting and dispersing agent (Additol® VXW 6208/60, Allnex Austria GmbH), and 2.5 g of a mineral oil based, silicon-free defoamer (Additol® VXW 6393, Allnex Austria GmbH) were added and mixed. To this mixture, the following components were added in the sequence stated: 57.5 g of a natural mixture of corpuscular silica and lamellar kaolinite (Silitin® Z 89, Hoffmann Mineral GmbH), 223.5 g of a rutile type titanium dioxide pigment (Kronos® 2190, Kronos International Inc.), 6.0 g of ayellow iron oxide pigmentbased on 0C-FeO(OH), Pigment Yellow 42 (Bayferrox® 3290, Lanxess Deutschland GmbH), 12.5 g of ablack iron oxide pigmentbased on Fe ₃ 0 ₄ , Pigment black 11 (Bayferrox® 306, Lanxess Deutschland GmbH), and 192 g of a white baryte mineral with low calcium carbonate and silicate content and a brightness R _y of 92 (E WO, Sachtleben Minerals GmbH & Co. KG, distributed by Krahn Chemie). The mixture was homogenised after each addition and then transferred to a bead mill and ground for about thirty minutes. The following further components were then added in the sequence indicated:

2.5 g of the mineral oil based, silicon-free defoamer as supra, 6.5 g of a coalescence agent (2,2,4- trimethylpentane-l,3-diol monoisobutyrate, Texanol®, Eastman Chemical), 5.0 g of a urethane- modified polyether thickener (Additol® VXW 6388, Allnex Austria GmbH), and 2.5 g of a polyether modified polysiloxane substrate wetting agent (Additol® 6503N, Allnex Austria GmbH), this mixture was homogenised to a paste P, and pastes PI to P4 were then completed by adding the masses of the dispersions D1 to D4 as listed in table 4:

Table 4 Pigmented Pastes PI to P4

Shortly before application, 494.5 g each of an aqueous, internally plasticised type 1 epoxide dispersion having a mass fraction of solids of 52 % and a specific amount of substance of epoxide group in the dispersion of 1 mol/kg (Beckopox® EP 387w/52WA, Allnex Germany GmbH) was admixed to the different pigmented pastes to form the primer coating compositions PCC1 to PCC4 which were adjusted to the required viscosity by addition of deionised water, and well mixed before applying.

Example 7 Adhesion Test on Cold Rolled Steel Sheets

Primer coating compositions PCC1 to PCC4 as prepared in Example 6 were applied to untreated cold rolled steel sheets (Gardobond® OC), and after flush-off at room temperature for ten minutes, the coated sheets were dried for twenty minutes at 80 ^° C in an oven, and then left for at 23 ^° C and 50 % of relative humidity for one day, seven days, and fourteen days for post-curing. The dry film thickness of the primer coating was 65 pm (0.065 mm). These sheets were subjected after the time intervals mentioned to a cross-hatch test according to DIN EN ISO 2409 after post-curing, with removal of loose particles using an adhesive tape, where the following results were obtained: Table 5 Cross-Hatch Adhesion Test for Primer Coating onto Cold Rolled Steel Sheets

The GT values were determined in accordance with DIN EN ISO 2409.

As can be seen, after fourteen days of post-cure storage, all inventive primer coating compositions showed good adhesion to the steel substrate, while the comparative example (PCC1, without addition of dimer fatty acid in the advancement step) showed bad adhesion regardless of the post-cure time. A higher amount of dimer fatty acids used in the advancement step accelerates the adhesion of the coating layer to the steel sheet.

Example 8a Inter-Layer Adhesion Test with a Solvent-Borne Pigmented Top-Coat A pigmented topcoat based on Michael Addition crosslinking was prepared according to the following recipe:

8a - 1 Preparation of malonated polyester MPE1

MPE1 was prepared as follows: Into a reactor provided with a distilling column filled with Raschig rings were brought 382 g of neopentyl glycol (M = 104.15 g/mol; 3.668 mol), 262.8 g of hexahydrophthalic anhydride (M = 154.16 g/mol; 1.705 mol) and 0.2 g of butyl stannoic acid (Bu-Sn(O) OH; Fascat® 4100, PMC Vlissingen B.V.). The mixture was polymerised at 240 ^° C under nitrogen to an acid value of less than 1 mg/g. The mixture was cooled down to 130 ^° C and 355 g of diethylmalonate (M = 160.168 g/mol; 2.216 mol) were added. The reaction mixture was heated to 170 ^° C and ethanol was removed under reduced pressure. The resin was subsequently cooled and diluted with butyl acetate to a mass fraction of solids of 85 %, to yield a material with an OH value of 16 mg/g, GPC M _n = 1750 g/mol and a specific amount of substance of activated CH ₂ groups of 2.86 mol/kg, and a specific amount of substance of acidic CH groups of 5.71 mol/kg (malonate equivalent weight of 350 g/Eq; active C-H EQW = 175 g/Eq). 8a - 2 Preparation of malonated polyester MPE2

MPE2 was prepared as follows: Into a reactor provided with a distilling column filled with Raschig rings were brought 382 g of neopentyl glycol, 262.8 g of hexahydrophthalic anhydride and 0.2 g of butyl stannoic acid. The mixture was polymerised at 240 ^° C under nitrogen to an acid value of less than 1 mg/g. The mixture was cooled down to 130 ^° C and 355 g of diethylmalonate were added. The reaction mixture was heated to 170 ^° C and ethanol was removed under reduced pressure. When the viscosity at 100 ^° C reached 0.5 Pa · s, the material was cooled down to 140 ^° C and 11.2 g of solid succinimide were added. This mixture was stirred until all succinimide was dissolved. The resin was further cooled and diluted with butyl acetate to a mass fraction of solids of 85 %.

8a - 3 Composition of catalyst C

For the preparation of Catalyst C, 43.7 g of aqueous tetrabutylammoniun hydroxide (aqueous solution with a mass fraction of the base of 55 %), 19.7 g of diethyl carbonate, 31.8 g of n-propanol and 4.8 g of water were mixed.

8a - 4 Preparation and application of a pigmented topcoat coating formulation

146.4 g of MPE1, 167.5 g of MPE2, 19.9 g of 1,2,4-triazole (solution in n-propanol with a mass fraction of solids of 15 %), 1.9 g of a substrate wetting and levelling agent for solvent-borne coatings based on a silicone acrylate copolymer (BYK® 3550, solution with a mass fraction of solids of 52 %, dissolved in methoxypropylacetate) and 4.3 g of a sterically hindered amine light stabiliser (mixture of bis-(l,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl, (l,2,2,6,6-pentamethyl-4-piperidyl) sebacate, commercially available as Tinuvin® 292 from BASF SE) were mixed with 616.9 g of a previously prepared mill base containing 166.4 g of di-trimethylolpropane tetraacrylate (DiTMPTA), 19.4 g of a wetting and dispersing additive (solution of a polyurethane block copolymer having pigment affinic groups in 2-methoxy-l- methylethylacetate, mass fraction of solids ca. 52 %, commercially available as DISPERBYK® 2150 from BYK Chemie GmbH) and 431.1 g of a surface-treated rutile type titanium dioxide white pigment (commercially available as Kronos® 2310 from Kronos BV). After obtaining a homogeneous mixture, 23.3 g of catalyst C were added and mixed in. Coating formulations were drawn down or spray applied onto the steel sheets of example 7 coated with the WB epoxy primer compositions to obtain a dry layer thickness of from 50 pm to 70 pm onto the steel sheets of Example 7 which were coated with the primer coating compositions PCC1 to PCC4, respectively, and post-cured for seven days at 23 ^° C and 50 % relative humidity.

Interlayer adhesion was tested according to DIN EN ISO 2409 as described supra, after twenty-four hours, seven days, and fourteen days of rest at room temperature (23 ^° C) and 50 % of relative humidity. The results are collected in table 6:

Table 6 Cross-Hatch Adhesion Test for Intercoating Adhesion

Example 8b Inter-Layer Adhesion Test with a Solvent-Borne Pigmented Top-Coat

A further 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 w _Am 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 steel sheets of Example 7 which were coated with the primer coating compositions PCC1 to PCC4, respectively, after post-curing for seven days at 23 ^° C and 50 % relative humidity, within five minutes after addition of the basic catalyst solution. The painted slabs were dried for sixty minutes at ambient temperature (25 ^° C), whereafter the dry film thickness of the top coat was determined to be 55 pm (0.055 mm) and tested for intercoat adhesion according to DIN EN ISO 2409 as described supra, after twenty-four hours, seven days, and fourteen days of rest at room temperature (23 ^° C) and 50 % of relative humidity. The results are collected in table 7.

Table 7 Cross-Hatch Adhesion Test for Intercoating Adhesion

As can be seen, for all of the primer coating compositions according to the invention (PCC2 to PCC4), no lack of adhesion was found in both Examples 8a and 8b. In the comparative example using primer coating composition PCC1, prolonged post-curing (fourteen days) improved the intercoat adhesion, yet there were still loose particles of the coating film at the intersections of the cuts. The total uncovered area after removal of loose particles with adhesive tape accounted for not more than 5 % of the cross-cut area.

Example 9 (Comparative)

Long-Chain Alkyl Modified Epoxy Resin Dispersion

A type 1 epoxide resin dispersion was modified by addition of a mass fraction of 5.6 % of epoxydised soy bean oil made from soy bean oil having a molar mass of 868 g/mol and an average number of double bonds in the triglyceride of 4.7. The epoxydised oil had a calculated molar mass of 933.8 g/mol and no remaining olefinic unsaturation. The specific amount of substance of long chain alkyl groups in the modified epoxy resin was 0.18 mol/kg, based on the mass of solids in the modified resin dispersion. The specific amount of substance of epoxide groups in this dispersion, n(EP) / m(Disp) was 1.333 mol/kg, and its mass fraction of solids was 57 %.

Epoxy Resin-Based Primer Coating Composition

An epoxy resin-based primer composition was made using the pigmented paste P as described in example 6. To 629 g of the paste P, 183.0 g of an aliphatic polyamine hardener dispersion based on an epoxy-amine adduct, having a mass fraction of solids of 44 %, and a specific amount of substance of amino hydrogen atoms n(N-H)/ m(Disp) = 1.754 mol/kg, where n(N-H) is the amount of substance of amino hydrogen atoms, and (Disp) is the mass of the dispersion. This polyamine dispersion does not contain long chain alkyl groups, as defined supra.370 g of the long-chain alkyl modified epoxy resin dispersion supra was added and well mixed with the mixture of the pigmented paste and the hardener dispersion, immediately before use, to obtain the primer coating composition PCC5.

Adhesion Test on Steel

The primer coating composition PCC5 was applied to untreated cold rolled steel sheets (Gardobond® OC), and after flush-off at room temperature for ten minutes, the coated sheets were dried for twenty minutes at 80 ^° C in an oven, and then left for at 23 ^° C and 50 % of relative humidity for one day, seven days, and fourteen days for post-curing. The dry film thickness of the primer coating was 65 pm (0.065 mm). These sheets were subjected after the time intervals mentioned to a cross-hatch test according to DIN EN ISO 2409 after post-curing, with removal of loose particles using an adhesive tape. Values between GT0 and GT1 were found after seven days.

Interlayer Adhesion Test

Coating formulations according to example 8a were drawn down onto steel sheets coated with the water-borne epoxy primer compositions of this example 9 after 14 days from priming, to obtain a dry layer thickness of from 50 pm to 70 pm onto the primed steel sheets. Interlayer adhesion was then tested in a humidity chamber starting twenty-four hours later. After 1000 h of exposure, blister number was rated "2", and size was rated "1". For comparison, the top- coated steel sheets of Example 8a were rated "0" for number of blisters, and "0" for size of blisters.

Conclusion

This comparison shows that a modification with lower specific amount of substance of long chain alkyl groups in the epoxy resin component of 0.2 mol/kg is not sufficient to avoid lack of interlayer adhesion.