Aqueous dispersion for use in electrodeposition coating compositions

Abstract

The invention relates to aqueous dispersions (AD) comprising cationic polymer particles, the cationic polymer particles comprising one or more amine functional epoxy addition resins, the amine functional epoxy addition resins being obtainable by reacting at least one aromatic substance (A) comprising at least two epoxy groups; at least one aromatic substance (B) comprising at least two hydroxyl groups; at least one aliphatic substance (C) selected from dicarboxylic acids (C1), and / or polyalkylene glycol diglycidyl ethers (C2); at least one amine substance (D); and optionally reacting the thus formed product with an acid substance (E). The invention further relates to a process for producing such aqueous dispersion, an aqueous electrocoating material comprising such aqueous dispersion, process for producing an at least partially coated substrate by the afore-mentioned method, and a thus coated substrate.

Description

[0001] AQUEOUS DISPERSION FOR USE IN ELECTRODEPOSITION COATING COMPOSITIONS

[0002] The invention relates to aqueous dispersions comprising cationic polymer particles, the cationic polymer particles comprising amine functional epoxy addition resins. The invention further relates to a process for producing such aqueous dispersions and aqueous electrocoating materials containing such aqueous dispersions as well as a process for producing substrates which are at least partially coated with the aqueous electrocoating materials and thus coated substrates.

[0003] BACKGROUND OF THE INVENTION

[0004] A normal requirement within the automobile sector is that the metallic components used for manufacture must be protected against corrosion. The requirements concerning the corrosion prevention to be achieved are very stringent, especially as the manufacturers often give a guarantee against rust perforation over many years. Such corrosion prevention is typically achieved by coating the components, or the substrates used in their manufacture, with at least one coating apt for the purpose, typically an electrodeposition coating.

[0005] The electrodeposition process can be anodic or cathodic; typically, the article to be coated serves as the cathode. Electrodeposition processes are advantageous both economically and environmentally due to the high transfer efficiency of coating resin to the substrate and the low levels of organic solvent, if any, that are employed. Another advantage of electrocoat compositions and processes is that the applied coating composition forms a uniform and continuous layer over a variety of metallic substrates regardless of shape or configuration. This is especially advantageous when the coating is applied as an anticorrosive coating onto a substrate having an irregular surface, such as a motor vehicle body. The even and continuous coating layer formed over all portions of the metallic substrate provides maximum anticorrosion effectiveness.

[0006] Electrocoating baths typically comprise an aqueous dispersion or emulsion of a film forming material, such as an epoxy resin, having ionic stabilization. A dispersion is typically a two-phase system of one or more finely divided solids, liquids, or combinations thereof in a continuous liquid medium such as water or a mixture of water and organic cosolvent. An emulsion is a dispersion of liquid droplets in a liquid medium, preferably water or a mixture of water and various cosolvents. Accordingly, an emulsion is a type of dispersion. A suspension is a dispersion of solid particles in a liquid medium, preferably water or a mixture of water and various cosolvents. Accordingly, a suspension is also a type of dispersion.

[0007] For automotive or industrial applications, the electrocoat compositions are formulated to be curable compositions by using self-crosslinking resins or those including a crosslinker. During electrodeposition, a coating composition containing an ionically-charged resin is deposited onto a conductive substrate by submerging the substrate in an electrocoating bath having dispersed therein the charged resin and then applying an electrical potential between the substrate and a pole of opposite charge, for example, a stainless-steel electrode. The charged coating particles are plated or deposited onto the conductive substrate and the coated substrate is then heated to cure the coating.

[0008] Suitable automotive metals include inter alia cold rolled steel ("CRS"), electrogalvanized steel ("EGS"), hot dipped galvanized steel ("HDG"), galvanneal (annealed hot-dipped galvanized steel), aluminum and aluminum alloys, and other zinc-alloy coated metals. To improve adhesion of the electrocoat to the metal surface, the metal is typically treated with a zinc phosphate conversion coating.

[0009] Continuing problems with cathodic electrocoating compositions have been the lack of edge protection or edge coverage of the substrate. Said edge protection is normally a compromise of edge coverage and good flow / levelling of surface of the coating film formed after application. It is known in the state of the art to use cationic epoxy microgels in electrocoating compositions to improve the edge coverage especially for higher film build electrocoats in the ASM (automotive supply metal) market, because the presence of these microgels significantly increases the melt viscosity and thereby reduces the flow of the applied coating composition away from the edges of the substrate. This significant increase in melt viscosity, however, does no longer provide a sufficient leveling of the applied coating composition on the substrate and therefore results in a rough coating surface.

[0010] Of advantage accordingly would be a polymeric resin which can be used in aqueous electrocoating materials as binder and which would result in a higher film thickness at the edges of the substrates, thus leading to improved edge protection. At the same time, said binder should provide a sufficient low viscous melt layer at the coating surface to achieve good flow / leveling properties of the applied coating material. The improvement in edge protection and / or smoothness should, however, not result in a negative influence on the storage stability or the deposition process of the electrocoating material.

[0011] Furthermore, standard prior art polymeric resins used for such purposes are typically bisphenol-based. Nowadays, the amount of, e.g., bisphenol A and its derivatives should be reduced for environmental reasons and safety at work. Thus, it is also desired to provide an aqueous dispersion for use in electrocoating materials for the above purposes making use of a reduced amount of bisphenols and their derivatives in their production.

[0012] Accordingly, the object of the present invention is to provide an aqueous dispersion which can be incorporated in aqueous electrocoating materials and which results in a higher film thickness of the electrocoating material at the edges of the substrate, thus resulting in an improved edge coverage. Moreover, cured layers obtained from the aqueous electrocoating material should have sufficient surface smoothness and adhesion to the substrate. Additionally, the aqueous electrocoating materials should possess an adequate particle size, filterability and electrochemical depositability. SUMMARY OF THE INVENTION

[0013] The objects described above are achieved by the subject matter claimed in the claims and by the preferred embodiments of that subject matter that are described in the description hereinafter.

[0014] A first subject of the present invention is therefore an aqueous dispersion (AD) comprising cationic polymer particles, the cationic polymer particles comprising one or more amine functional epoxy addition resins, the amine functional epoxy addition resins being obtainable by

[0015] (1) reacting a. at least one aromatic substance (A) comprising at least two epoxy groups; b. at least one aromatic substance (B) comprising at least two hydroxyl groups; c. at least one aliphatic substance (C) selected from

[0016] I. dicarboxylic acids (C1), and / or ii. polyalkylene glycol diglycidyl ethers (C2); and d. at least one amine substance (D); and

[0017] (2) optionally reacting the product obtained in (1) with an acid substance (E).

[0018] The above-specified aqueous dispersion (AD) is hereinafter also referred to as aqueous dispersion of the invention or microgel dispersion of the invention and accordingly is a subject of the present invention. Preferred embodiments of the aqueous dispersion of the invention are apparent from the description hereinafter and from the dependent claims.

[0019] A further subject of the present invention is a process for preparing an aqueous dispersion (AD) of the invention comprising the cationic polymer particles, said process comprising the following steps of:

[0020] (1) reacting a. at least one aromatic substance (A) comprising at least two epoxy groups; b. at least one aromatic substance (B) comprising at least two hydroxyl groups; c. at least one aliphatic substance (C) selected from

[0021] I. dicarboxylic acids (C1), and / or ii. polyalkylene glycol diglycidyl ethers (C2); and d. at least one amine substance (D), to form a polymeric product;

[0022] (2) dispersing the polymeric product obtained in (1) an aqueous medium and

[0023] (3) optionally reacting the polymeric product obtained in (1) with an acid substance (E).

[0024] Another subject of the present invention is an aqueous electrocoating material (ECM) comprising (a) at least one inventive aqueous dispersion (AD) or at least one aqueous dispersion (AD) prepared according to the inventive process,

[0025] (b) at least one further binder B being different from the cationic polymer particles contained in the aqueous dispersion (AD) and optionally containing a crosslinker (CL),

[0026] (c) at least one pigment,

[0027] (d) optionally at least one additive, and

[0028] (e) optionally at least one catalyst.

[0029] Yet another subject of the present invention is a process for producing an at least partially coated substrate, said process comprising the following steps:

[0030] (i) at least partially contacting a substrate with an inventive aqueous electrocoating material (ECM), thus forming a coating film from the aqueous electrocoating material (ECM);

[0031] (ii) optionally rinsing the coating film formed in step (i) with an aqueous medium;

[0032] (iii) curing the coating film obtained after step (i) or optionally (ii); and

[0033] (iv) optionally applying at least one further coating layer and curing said coating layer(s).

[0034] A final subject of the present invention is an at least partially coated substrate obtained by the inventive process.

[0035] DETAILED DESCRIPTION

[0036] The analytical methods used in the context of the present invention for determining certain characteristic variables can be found in the Examples section. Unless explicitly indicated otherwise, these methods are to be employed for determining the respective characteristic variable. Where reference is made in the context of the present invention to an official standard without any indication of the issue date, the reference is implicitly to that version of the standard, which is valid on the filing date of this application; or, in the absence of any valid version at that point in time, to the last valid version.

[0037] All film thicknesses reported in the context of the present invention should be understood as dry film thicknesses. It is therefore the thickness of the cured film in each case. Hence, where it is reported that a coating material is applied at a particular film thickness, this means that the coating material is applied in such a way as to result in the stated film thickness after curing.

[0038] All temperatures elucidated in the context of the present invention should be understood as the ambient temperature of the room in which the substrate or the coated substrate is located. It does not mean, therefore, that the substrate itself is required to have the temperature in question. Aqueous dispersion (AD)

[0039] The aqueous dispersion (AD) comprises cationic polymer particles, the cationic polymer particles themselves comprise or consist of one or more amine functional epoxy addition resins. The amine functional epoxy addition resins are obtained by reacting at least one aromatic substance (A) comprising at least two epoxy groups; at least one aromatic substance (B) comprising at least two hydroxyl groups; at least one aliphatic substance (C) selected from dicarboxylic acids (C1), and / or polyalkylene glycol diglycidyl ethers (C2); at least one amine substance (D); followed by an optional reaction with an acid substance (E) in order to neutralize the amino groups at least partially. Since the dispersion is an aqueous dispersion, the afore-mentioned reaction product obtained from (A), (B), (C) and (D) is dispersed in an aqueous medium, such as water prior to or together with adding substance (E), which can be contained in the aqueous medium.

[0040] The inventive aqueous dispersions (AD) contain cationic polymer particles (i.e., microgel particles), in which the polymer is present in the form of comparatively small discrete particles, or discrete microparticles. Said microparticles are preferably at least partly intramolecularly crosslinked. The latter means that the polymer structures present within a particle correspond to a typical macroscopic network with a three-dimensional network structure.

[0041] The expression "aqueous” is known in this context to the skilled person. It refers fundamentally to a system which comprises as its dispersion medium not exclusively or primarily organic solvents (also called solvents); instead, it comprises as its dispersion medium a significant fraction of water. Preferred embodiments of the aqueous character, defined on the basis of the maximum amount of organic solvents and / or on the basis of the amount of water, are described later on below.

[0042] The cationic polymer particles being present in the aqueous dispersion (AD) preferably have a z-average particle size (z-mean) of 50 to 1,000 nm, more preferably of 100 to 700 nm, even more preferably of 100 to 600 nm, very preferably of 100 to 400 nm, as determined according to DIN EN ISO 22412:2018-09.

[0043] The fraction of the cationic polymer particles in the aqueous dispersion (AD) is preferably 10 to 40 wt.%, very preferably 15 to 30 wt.%, based on the total weight of the aqueous dispersion (AD). This fraction can be determined by drying the aqueous dispersion (AD) for 1 hour at a temperature of 130 °C. The ratio of the weight of the remaining dry substance to the sample weight before drying multiplied by 100 is the respective solids content. The difference to 100 wt.-% is the volatile content, which comprises water, preferably as its main content.

[0044] The pH value of the aqueous dispersion is preferably in the range from 5 to 8. Aromatic substance (A) comprising at least two epoxy groups

[0045] The terms "aromatic” and "aliphatic” as used herein are used mutually excluding each other.

[0046] According to "IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"), compiled by A. D. McNaught and A. Wilkinson, Blackwell Scientific Publications, Oxford (1997). Online version (2019-) created by S. J. Chalk. ISBN 0-9678550-9-8. https: / / doi.org / 10.1351 / goldbook" an "aliphatic compound” is an "acyclic or cyclic, saturated or unsaturated carbon compound, excluding aromatic compounds”. With other words an "aromatic compound is a "compound which contains at least one aromatic ring system.” If more than one aromatic ring is contained in a compound, such aromatic rings may, e.g., be fused with each other or be linked by aliphatic residues, which however changes nothing with respect to the classification of such compounds as being "aromatic compounds.”

[0047] The term "substance” as used herein includes the meaning "compounds,” i.e., "chemical substances being composed of many identical molecules,” but the term "substance” also includes oligomeric substances, and polymeric substances alike, such as, e.g., resins, containing entities of the same kind, which however, may have different molecular weights, i.e., possess a polydispersibility.

[0048] The at least one aromatic substance (A) comprises at least two epoxy groups, preferably two epoxy groups. The epoxy groups are even more preferred in form of glycidyl groups.

[0049] The aromatic substance (A) employed herein is preferably a liquid epoxy resin (LER). Preferably, the aromatic substance (A) is a bisphenol diglycidyl ether resin, such as a bisphenol A diglycidyl ether and or bisphenol F diglycidyl ether, or mixtures thereof.

[0050] Aromatic substance (B) comprising at least two hydroxyl groups

[0051] The aromatic substance (B) preferably possesses two hydroxy groups, preferably two phenolic hydroxyl groups. Preferably the at least one aromatic substance (B) is a bisphenol substance, such as bisphenol A, bisphenol F, or a mixture thereof.

[0052] Aliphatic Substances (C)

[0053] The aliphatic substances (C) particularly serve to increase the smoothness of the cured films formed by the electrocoat material containing the aqueous dispersions comprising the cationic polymer particles, with other words they reduce the roughness of such cured films, but should still provide sufficient edge corrosion protection and / or scribe corrosion protection, by simulaneously reducing the amounts of aromatic ingredients (A) and (B), compared to the manufacture of conventional microgel particles. The aliphatic substances (C) carry preferably terminal functional groups which are either reactive towards epoxy groups, or towards hydroxyl groups and carboxyl groups. The residues linking the preferably terminal functional groups of the aliphatic substances (C) comprise or consist of carbon atoms and hydrogen atoms in case of (C1) and additionally ether oxygen atoms in case of (C2). The number of carbon atoms in the linking residues, which link the terminal functional groups of the aliphatic substances (C) comprise preferably at least 6 carbon atoms and up to preferably 50 carbon atoms, more preferably 8 to 46 carbon atoms. The linking residue may by linear, e.g., in most cases of (C2), or branched, e.g., in some cases of (C1) and may comprise alicyclic moieties, e.g., in some cases of (C1).

[0054] Aliphatic substances (C1) ideally carry two carboxyl groups which are reactive towards epoxy groups, while aliphatic substances (C2) carry two epoxy groups, preferably in form of glycidyl groups, which are reactive towards hydroxyl groups and carboxyl groups.

[0055] Dicarboxylic Acids (C1)

[0056] Dicarboxylic acids as used in the present invention are preferably depicted by the following general formula (I)

[0057] HOOC-R-COOH (I), wherein R is a divalent aliphatic hydrocarbon residue, which preferably comprises 4 to 48 carbon atoms, more preferred 6 to 44 carbon atoms, event more preferred 8 to 44 carbon atoms. R can be linear or branched, and may comprise or consist of cyclic moieties.

[0058] Preferred dicarboxylic acids are, e.g., adipic acid, pimelic acid, suberic acid, cyclohexanedicarboxylic acid, such as 1 ,4-cyclohexane dicarboxylic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, thapsic acid, japanic acid, phellogenic acid and equisetolic acid. However, most preferred dicarboxylic acids of formula (I) are dimer fatty acids.

[0059] Dimer Fatty Acids (C1)

[0060] As stated above, particularly preferred dicarboxylic acids are so-called dimer fatty acids (also known as dimerized fatty acids or simply dimer acids). The term "fatty acid” denotes for an aliphatic monocarboxylic acid, which can be linear or branched. Dimer fatty acids are prepared by oligomerization of unsaturated fatty acids. The term "dimer fatty acid,” as defined herein, includes technical grade products which are the direct reaction products of the oligomerization reaction, as well as purified products obtained by purification distillation and at least partial hydrogenation of purified or un-purified products of the oligomerization reaction. Starting materials which can be used for die oligomerization reaction preferably include unsaturated C12 to C22 fatty acids. Depending on the number and position of the double bonds in the C12 to C22 fatty acids used for preparing the dimer fatty acids, the carboxyl groups of the dimer fatty acids are linked to one another by saturated or unsaturated hydrocarbon radicals having preferably and predominantly 24 to 44 carbon atoms. These hydrocarbon radicals are commonly branched and may contain double bonds and Ce-cycloaliphatic hydrocarbon radicals; these cycloaliphatic radicals may also be fused. Possibly formed aromatic residues, should preferably be at least partially hydrogenated.

[0061] Depending on the reaction regime, the oligomerization referred to above produces a substance which primarily comprises dimeric molecules (idealized dimer fatty acids) but also trimeric molecules (idealized trimer fatty acids) and the substance may also comprise minor amounts of monomeric molecules and (other) byproducts.

[0062] Such commercial technical grade dimer fatty acids preferably contain at least 80 wt.-% of dimeric molecules, up to 19 wt.-% of trimeric molecules, and not more than 2 wt.-% of monomeric molecules and of other byproducts. Purification commonly takes place by distillation.

[0063] For the purposes of the present invention, it is preferred that dimer fatty acids are used that comprise or consist of: > 90 wt.-% of dimeric molecules, < 5 wt.-% of trimeric molecules, and < 5 wt.-% of monomeric molecules and of other byproducts. Particular preference is given to the use of dimer fatty acids which comprise or consist of: 95 to 98 wt.-% of dimeric molecules, less than 5 wt.-% of trimeric molecules, and less than 1 wt.-% of monomeric molecules and of any other byproducts present. Likewise, particularly preferred is the use of dimer fatty acids which comprise or consist of > 98 wt.-% of dimeric molecules, < 1.5 wt.-% of trimeric molecules, and < 0.5 wt.-% of monomeric molecules and of other byproducts.

[0064] In the present invention, of course, mixture of different dimeric fatty acids may be used.

[0065] Dimer fatty acids for particularly preferred use in the present invention are commercially available under the tradenames Radiacid 0970, Radiacid 0971, Radiacid 0972, Radiacid 0975, Radiacid 0976, and Radiacid 0977 from Oleon, Pripol 1006, Pripol 1009, Pripol 1012, and Pripol 1013 from Unichema, Empol 100S, Empol 1061 , and Empol 1062 from Cognis, and Onidyme 10 and Unidyme Tl from Arizona Chemical.

[0066] Polyalkylene Glycol Diglycidyl Ethers (C2)

[0067] The polyalkylene glycol diglycidyl ethers (C2) contain two glycidyl groups and are preferably linear, the glycidyl ether groups typically being terminal. Preferably the polyalkylene glycol diglycidyl ether (C2) has the following general formula (I): wherein

[0068] EO = ethylene oxide unit, PO = propylene oxide unit and BO = butylene oxide unit, and each of x, y and z = preferably 0 to 60, more preferred 5 to 50, even more preferred 8 to 45, with the proviso that x + y + z = preferably 5 to 60, more preferred 5 to 50 and even more preferred 8 to 45; and the ethylene oxide units, propylene oxide units and butylene oxide units can be arranged in any order.

[0069] Such substances can be obtained by reacting the polyalkylene glycols having two terminal hydroxy groups with epichlorohydrin.

[0070] Particularly preferred amongst the EO, PO and BO units are EO and PO units. Consequently, it is preferred that z = 0, and x + y = preferably 5 to 60, more preferred 5 to 50 and even more preferred 8 to 45.

[0071] Most preferred amongst the EO, PO and BO units are PO and BO units, particularly PO units. Consequently, it is preferred that z = x = 0, and y = preferably 5 to 60, more preferred 5 to 50 and even more preferred 8 to 45, such as 10 to 30.

[0072] The x EO, y PO and z BO units can be arranged in any order, including a random distribution, a gradient like distribution along the chain or a distribution in form of blocks or any combination of the afore-mentioned architectures.

[0073] Polyalkylene glycol diglycidyl ethers for particularly preferred use in the present invention are commercially available polypropylene glycol diglycidyl ethers under the tradenames Eposir 7103 or Eposir 7110 from SIR Industrials (Macherio, Italy).

[0074] Amine Substance (D)

[0075] The amine substance (D) is used to introduce the amino groups in the formation of the amine functional epoxy addition resins. This is preferably achieved by adding the amine substance (D) to the reaction product of substances (A), (B) and (C), which preferably contains epoxy groups that can react with amino groups in a ring-opening reaction.

[0076] The amine substance (D) preferably comprises primary and / or secondary amino groups, the primary amino groups, if comprised, preferably being in blocked form. Blocking primary amino groups is preferably done with ketones and / or aldehydes which typically react with the primary amino groups under formation of so-called ketimines and / or aldimines. Secondary amino groups present are evidently unable to be blocked in this reaction, and therefore remain free. Consequently, a polyamine which as well as blocked primary amino group(s) also contains free secondary amino group(s) can be prepared readily by way of the stated preferred blocking reactions from a corresponding polyamine which contains free secondary and primary amino groups. Suitable examples of blocking agents may be selected from acetone, methyl ethyl ketone, methyl isobutyl ketone, diisopropyl ketone, cyclopentanone, cyclohexanone or mixtures thereof, preferably methyl ethyl ketone and / or methyl isobutyl ketone. Preferred blocking agents are ketones wherein the reaction product of (A), (B), (C) and (D) can also be dissolved or dispersed.

[0077] Examples of preferred amine substances (D) are those obtainable by blocking of the primary amino groups of diethylenetriamine, 3-(2-aminoethyl)aminopropylamine, dipropylene-triamine, N1-(2-(4-(2-aminoethyl)piperazin-1- yl)ethyl)ethane-1 ,2-diamine (one secondary amino group, two primary amino groups for blocking), triethylenetetramine, N,N'-bis(3-aminopropyl)ethylenediamine (two secondary amino groups, two primary amino groups for blocking) and mixtures thereof, very preferably from diethylenetriamine.

[0078] The reaction conditions for deblocking of blocked primary amino groups are also known by one of skill in the art. For example, the transfer of a blocked amine to the aqueous phase is sufficient to shift the equilibrium back to the side of the deblocking, as a result of the concentration pressure that exists, exerted by the water, and thereby to generate free primary amino groups and a free ketone and / or aldehyde, with consumption of water. Thus, if the reaction product of (A), (B), (C) and (D) is dispersed in an aqueous medium deblocking occurs.

[0079] If the primary amino groups of polyamines are not blocked, one primary amine group may tend to react in a ringopening reaction with two epoxy groups, which is not preferred.

[0080] Acid Substance (E)

[0081] The acid substance (E) is preferably selected from inorganic acids and / or organic acids, preferably carboxylic acids. The acid substance is apt to react with the amino groups, thus forming the respective salts enhancing the dispersability of the particles in the aqueous medium, keeping them stable in the dispersion and providing a good depositability in a cathodic electrocoating procedure.

[0082] Amongst the inorganic acids sulfuric acid and phosphoric acid are preferred over hydrochloric acid, which tends to promote corrosion of metallic substrates.

[0083] However, organic acids are preferred over inorganic acids. Suitable organic acids are, for example, carboxylic acids, sulfonic acids and phosphonic acids. With preference, carboxylic acids are used. Examples of suitable carboxylic acids include lactic acid, acetic acid and formic acid. Amounts and Ratios

[0084] Substance(s) (C) partially substitute components (A) and (B) as used in prior art standard microgels. Therefore, it is preferred that the total amount of (C), based on the total amount of (A), (B) and (C) is in the range from 1 to 50 wt.-%, preferably 5 to 45 wt.-%, more preferably 10 to 40 wt.-%.

[0085] In case dicarboxylic acids (C1), preferably dimer fatty acids (C1) and polyalkylene glycol digylcidyl ethers (C2) are both used in (C) (i.e., (C1 )+(C2)), preparing the aqueous dispersion according to the invention, it is preferred that the amount of dicarboxylic acid (C 1 ), preferably dimer fatty acid (C1) is in the range from 5 to 95 wt.-%, preferably 10 to 90 wt.-%, more preferred 20 to 80 wt.-%, and most preferred 30 to 70 wt.-% based on the total amount of (C) and the amount of the polyalkylene glycol diglycidyl ether (C2) is in the range from 5 to 95 wt.-% preferably 10 to 90 wt.-%, more preferred 20 to 80 wt.-%, and most preferred 30 to 70 wt.-% based on the total amount of (C).

[0086] Due to the different property profiles of the dicarboxylic acids, preferably the dimer fatty acids (C1 ), and polyalkylene glycol diglycidyl ethers (C2) it is possible, if using both, to customize and optimize the aqueous dispersions of the present invention to show the desired properties.

[0087] To react amino groups of substance (D) with the epoxy containing substances (A) and (C2), it is preferred that the molar amount of epoxy groups contained in (A) plus (C2) exceeds the combined molar amounts of hydroxy groups contained in (B) plus carboxy groups contained in (C1) and that substances (A), (B), and (C) are at least partially reacted before substance (D) is added.

[0088] The total amount of water in the aqueous dispersion is preferably from 55 to 85 wt.%, very preferably 60 to 80 wt.%, based in each on the total weight of the aqueous dispersion (AD).

[0089] The total fraction of cationic polymer particles plus water in the aqueous dispersion (AD) is preferably at least 75 wt.%, preferably at least 80 wt.%, very preferably at least 85 wt.%, even more preferred at least 90 wt.-%, or at least 95 wt.-%, based on the total weight of the aqueous dispersion. The fraction of cationic polymer particles plus water can be determined by adding up the amount of particles (determined, for example by the solid content as previously described) and the amount of water added. Despite the low fraction of further components, such as organic solvents, the aqueous dispersions (AD) show a high storage stability. Moreover, the low amount of solvents being present in said dispersions (AD) allow to add additional fractions of organic solvents that are necessary to formulate the electrocoating material (ECM) without significantly increasing the overall VOC of the aqueous electrocoating material (ECM). Inventive process to produce the aqueous dispersion (AD)

[0090] A further aspect of the present invention is a process for preparing an aqueous dispersion (AD) comprising cationic polymer particles, said process comprising the following steps:

[0091] (1) reacting a. at least one aromatic substance (A) comprising at least two epoxy groups; b. at least one aromatic substance (B) comprising at least two hydroxyl groups; c. at least one aliphatic substance (C) selected from

[0092] I. dicarboxylic acids (C1), and / or ii. polyalkylene glycol diglycidyl ethers (C2); and d. at least one amine substance (D); to form a polymeric product;

[0093] (2) dispersing the polymeric product obtained in (1) an aqueous medium and

[0094] (3) optionally reacting the polymeric product obtained in (1) with an acid substance (E).

[0095] In step (1) it is preferred to first react substances (A), (B) and (C) in step (1-A) to produce an intermediate (IM) containing epoxy groups, preferably in form of glycidyl groups, and to subsequently, in step (1-B), to react the excess of epoxy groups, preferably all epoxy groups contained in the intermediate (IM), with substance (D)

[0096] Step (1-A) is preferably carried out in substance (i.e., solvent-free) or in the presence of organic solvents. Such solvents should not interfere in the reaction. This step can be carried out in the absence or presence of a catalyst. If a catalyst is used, it is preferably selected from the groups of tertiary amines and phosphorous containing catalysts such as triaryl phosphine, like triphenyl phosphine.

[0097] After mixing (A), (B) and (C) (typically liquid ingredients are weighed in first), preferably at room temperature or a temperature of about 15 to 40 °C, the temperature of the reaction mixture is raised to a reaction temperature in step (1-A) being preferably in the range from 120 °C to 160 °C, more preferably in the range from 125 °C to 155 °C, and even more preferred in the range from 125 °C to 145 °C. The reaction is preferable carried out until the epoxy equivalent weight (EEW) of the obtained intermediate (IM) is preferably greater than 700 g / eq such as from 700 g / eq to 1500 g / eq, preferably 900 g / eq to 1300 g / eq, more preferably 1000 g / eq to 1200 g / eq.

[0098] Preferably after cooling to a temperature of preferably below 120 °C (further) one or more organic solvents may be added such as an linear or branched alkanol, preferably comprising 3 to 6 carbon atoms, more preferred 4 or 5 carbon atoms, like propanol, butanol, pentanol, or hexanol to lower the viscosity of the microgel, if desired. The intermediate (IM) formed in step (1-A) is than reacted with substance (D) at a temperature being preferably in the range form 5 °C to 120 °C, more preferably being in the range from 10 °C to 80 °C, even more preferred 20 °C to 60 °C, and more preferred 30 °C to 50 °C.

[0099] Step (1) is preferably carried out in the absence of water as a solvent, this is particularly preferred if in step (1-B) a blocked amine substance containing blocked primary amino groups, preferably in form of a ketimine or aldimine is employed as substance (D). Ketimines and aldimines are typically not stable in aqueous media and are deblocked in aqueous medium, thus forming free amine groups.

[0100] To obtain the aqueous dispersion (AD) of the invention, the polymeric product produced in step (1) is dispersed in an aqueous medium such as water (step (2)).

[0101] In optional step (3) the polymeric product obtained in (1) is reacted (i.e., neutralized), at least partially, with an acid substance (E).

[0102] It is also possible to combine steps (2) and (3), e.g., by adding the acid substance (E) to the aqueous medium used in step (2), while or before using the aqueous medium in step (2).

[0103] With respect to preferred embodiments of substances used in the inventive process and steps performed according to the inventive process, reference is made to description of the inventive aqueous dispersion (AD). What has been said about the inventive aqueous dispersion therefore applies mutatis mutandis with respect to further preferred embodiments of the inventive method.

[0104] Inventive aqueous electrocoating composition

[0105] The inventive aqueous dispersion (AD) is used to prepare an aqueous electrocoating material (ECM). Thus, a further aspect of the present invention is an aqueous electrocoating material (ECM), comprising:

[0106] (a) at least one inventive aqueous dispersion (AD) or at least one aqueous dispersion (AD) prepared according to the inventive process,

[0107] (b) at least one further binder B being different from the cationic polymer particles contained in the aqueous dispersion (AD) and optionally containing a crosslinker (CL),

[0108] (c) at least one pigment,

[0109] (d) optionally at least one additive, and

[0110] (e) optionally at least one catalyst. "Aqueous electrocoating material (ECM)" in the context of the present invention should be understood preferably to mean that the electrocoating material (ECM) comprises a water fraction of at least 70 wt.%, preferably at least 80 wt.%, very preferably at least 95 wt.%, and even more preferably at least 98 wt.% based in each case on the total amount of the solvents present (that is, water and organic solvents). The water fraction is preferably 70 to 100 wt.%, more particularly 75 to 100 wt.%, very preferably 80 to 100 wt.%, based in each case on the total amount of the solvents present.

[0111] The solids content (180 °C, 30 min, 1 g sample) of the ECM is preferably in the range from 5 to 35 wt.-%, more preferred from 12.5 to 25 wt.-% and most preferred from 15 to 22.5 wt.-% and 15 to 20 wt.%, based on the total weight of the ECM.

[0112] The pH value of the ECM is preferably in the range from 2 to 10, more preferred 3.5 to 7, and even more preferred 4.0 to 6.5, most preferably in the range of 4.5 to 6.0.

[0113] Aqueous dispersion (AD)

[0114] The electrocoating material (ECM) preferably comprises the aqueous dispersion (AD) previously described in a total amount of 0.5 to 15.0 wt.%, more preferably of 0.7 to 10.0 wt.%, even more preferably of 0.8 to 8.0 % by weight, very preferably of 1.0 to 6.0 wt.%, based in each case on the total weight of the aqueous electrocoating material (ECM).

[0115] Particularly preferred, the combined amounts of solid ingredients contained in the one or more aqueous dispersions (AD), are in the range from 0.1 to 1.5 wt.-%, preferably 0.2 to 1.2 wt.-% and more preferably 0.25 to 1.0 wt.-%, based on the total weight of the electrocoating material (ECM).

[0116] Any of the afore-mentioned aqueous dispersions according to the invention can be used in the electrocoating material of the invention, independently if the amine functional epoxy addition resin used therein contains only (C1), only (C2) or both, (C1) and (C2).

[0117] Particularly, if the electrocoating materials of the invention contain just one aqueous dispersion according to the present invention, they contain an aqueous dispersion containing cationic particles being a reaction product of (A), (B), (C1), (D) and optionally (E); or an aqueous dispersion containing cationic particles being a reaction product of (A), (B), (C2), (D) and optionally (E); or an aqueous dispersion containing cationic particles being a reaction product of (A), (B), (01), (C2), (D) and optionally (E).

[0118] All such electrocoating materials possess an improved corrosion resistance and an improvement regarding a reduced surface roughness. This is particularly the case, where the at least one aqueous dispersion contains cationic particles being a reaction product of (A), (B), (01), (02), (D) and optionally (E).

[0119] It is further preferred that the electrocoating materials of the invention contain two or more aqueous dispersions according to the present invention, such as at least one aqueous dispersion containing cationic particles being a reaction product of (A), (B), (C1 ), (D) and optionally (E); at least one aqueous dispersion containing cationic particles being a reaction product of (A), (B), (C2), (D) and optionally (E); or at least one aqueous dispersion containing cationic particles being a reaction product of (A), (B), a first substance (C1), (D) and optionally (E); and containing cationic particles being a reaction product of (A), (B), a seond substance (C1), differing from the first substance (C1 ), (D) and optionally (E); preferably the first and second substances (01) being different dicarboxylic acids of formula (I), more preferred different dimer fatty acids; or at least one aqueous dispersion containing cationic particles being a reaction product of (A), (B), a first substance (C2), (D) and optionally (E); and containing cationic particles being a reaction product of (A), (B), a second substance (C2), differing from the first substance (C2), (D) and optionally (E); preferably the first and second substances (02) being different polyalkylene glycol diglycidy lethers, more preferred different polypropyleneglycol diglycidyl ethers.

[0120] Binder B being different from cationic particles in the aqueous dispersion (AD)

[0121] The term "binder" in the sense of the present invention and in agreement with DIN EN ISO 4618 (German version, date: March 2007), refers preferably to those nonvolatile fractions of the composition of the invention that are responsible for forming the film, with the exception of any pigments and fillers therein, and more particularly refers to the polymeric resins which are responsible for film formation. The nonvolatile fraction may be determined by the method described in the examples section. The binder B may be self-crosslinking and / or externally crosslinking. Self-crosslinking binders B contain reactive functional groups which can undergo thermal crosslinking reactions with themselves and / or with complementary reactive functional groups in the self-crosslinking binders B. In contrast, externally crosslinking binders B contain reactive functional groups which can undergo thermal crosslinking reactions with complementary reactive functional groups in crosslinker CL. Suitable reactive functional groups of externally crosslinking binders B are hydroxyl groups, thiol groups, and primary and secondary amino groups, especially hydroxyl groups. Suitable complementary reactive functional groups present in the crosslinker CL or - in case of self-crosslinking binders - in the binder B, are blocked isocyanate groups, hydroxymethylene and alkoxymethylene groups, preferably methoxymethylene and butoxymethylene groups, and especially methoxymethylene groups. Preference is given to using externally crosslinking binders having hydroxyl groups.

[0122] Crosslinkers CL belong to the binders B. Thus, the amount of crosslinker is part of the amount of binders B.

[0123] The amount of the at least one binder B in the electrocoating materials (ECMs) of the invention is guided in particular by its solubility and its dispersibility in the aqueous medium as well as by its functionality with regard to the crosslinking reactions with itself or with the crosslinker CL, and may therefore be determined readily by the skilled worker on the basis of the skilled workers general art knowledge. Preferably, the at least one binder B is present in a total amount of 10 to 30 wt.%, more preferred 12 to 28 wt.-% and most preferred 14 to 26 wt.-% based on the total weight of the electrocoating material (ECM)

[0124] The at least one binder B preferably contains potentially cationic groups and / or cationic groups. Examples of suitable potentially cationic groups which can be converted into cations by neutralizing agents and / or quaternizing agents are primary, secondary, or tertiary amino groups, secondary sulfide groups or tertiary phosphine groups, especially tertiary amino groups, or secondary sulfide groups. Examples of suitable cationic groups are primary, secondary, tertiary, or quaternary ammonium groups, tertiary sulfonium groups or quaternary phosphonium groups, preferably quaternary ammonium groups or tertiary sulfonium groups, but especially quaternary ammonium groups. Examples of suitable neutralizing agents for the potentially cationic groups are inorganic and organic acids such as sulfuric acid, hydrochloric acid, phosphoric acid, formic acid, acetic acid, lactic acid, dimethylolpropionic acid or citric acid, especially formic acid, acetic acid, or lactic acid.

[0125] Examples of suitable binders B containing potentially cationic or cationic groups are resins containing primary, secondary, tertiary, or quaternary amino or ammonium groups and / or tertiary sulfonium groups and having amine numbers of preferably between 20 and 250 mg KOH / g and a weight-average molecular weight of from 300 to 10,000 Daltons. In particular, use is made of amino (meth)acrylate resins, amino epoxy resins, amino epoxy resins with terminal double bonds, amino epoxy resins with primary and / or secondary hydroxyl groups, amino polyurethane resins, amino- containing polybutadiene resins or modified epoxy resin-carbon dioxide-amine reaction products. Particularly preferred aqueous coating materials (ECM) are cathod leal ly depositable and thus comprise at least one binder B having cationic groups as described before.

[0126] Optional crosslinker CL being Part of the Binder B of Component (b)

[0127] The inventive aqueous electrocoating material (ECM) may comprise as component (b) at least one crosslinker CL, being by definition part of the binder. With preference, at least one externally crosslinking binder B is used in combination with at least one crosslinker CL. With particular preference, at least one externally crosslinking binder B containing potentially cationic or cationic groups is used in combination with at least one crosslinker CL. The crosslinker CL differs from the binder B.

[0128] Suitable crosslinkers CL include all customary and known crosslinking agents which contain suitable complementary reactive functional groups. The crosslinkers CL are preferably selected from the group consisting of blocked polyisocyanates, melamine- formaldehyde resins, tris(alkoxycarbony lamino)tri azi nes, and polyepoxides. The crosslinkers CL are more preferably selected from the group consisting of blocked polyisocyanates and highly reactive melamine-formaldehyde resins. Blocked polyisocyanates are used with particular preference.

[0129] Blocked polyisocyanates CA can be prepared from customary and known polyisocyanates containing aliphatically, cycloaliphatically, araliphatically and / or aromatically attached isocyanate groups. Preference is given to using polyisocyanates having from 2 to 5 isocyanate groups per molecule and having viscosities of from 100 to 10,000 mPas, preferably from 100 to 5,000 mPas, and in particular from 100 to 2,000 mPas (at 23°C). Moreover, the polyisocyanates may be hydrophilically or hydrophobically modified.

[0130] Suitable polyisocyanates include aliphatic polyisocyanates, aromatic polyisocyanates or mixtures of aromatic and aliphatic polyisocyanates. It is possible here to use not only monomeric polyisocyanates, dimers or trimers of the polyisocyanates, but also oligomeric or polymeric polyisocyanates. Preferred isocyanates are those whose monomeric constituent contains about 3 to about 36, more particularly about 8 to about 15 carbon atoms. Examples of such suitable monomeric polyisocyanates are diisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, propylene diisocyanate, ethylethylene diisocyanate, methyltrimethylene diisocyanate, trimethylhexamethylene diisocyanate, xylylene diisocyanate, 1 ,3- cyclopentylene diisocyanate, 1 ,4- cyclohexylene diisocyanate, 1 ,2-cyclohexylene diisocyanate, 4,4'- diphenylmethane diisocyanate, 1 ,5-naphthylene diisocyanate, toluene 2,4-diisocyanate, isophorone diisocyanate, and 4,4'-diisocyanatodicyclohexylmethane. Polyisocyanates of higher isocyanate functionality can also be used, such as tris(4-isocyanatophenyl)methane, 2,4,4'-triisocyanatodiphenylmethane, or bis(2,5-diisocyanato-4- methylphenyl)- methane. These polyisocyanates may be used in the form of the dimer or trimer or may serve as building blocks for oligomeric or polymeric polyisocyanates. Furthermore, mixtures of polyisocyanates can also be utilized. Examples of suitable blocking agents for preparing the blocked polyisocyanates CA are phenols, such as phenol, cresol, xylenol, nitrophenol, chlorophenol, ethylphenol, tert-butylphenol, hydroxybenzoic acid, esters of this acid or 2 , 5-d i-tert-buty 1-4- hydroxytoluene; lactams, such as E-caprolactam, 5-valerolactam, y-butyrolactam or p- propiolactam; active methylenic substances, such as diethyl malonate, dimethyl malonate, methyl, or ethyl acetoacetate or acetylacetone; alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, n-amyl alcohol, tert-amyl alcohol, lauryl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, methoxymethanol, glycolic acid, glycolic esters, lactic acid, lactic esters, methylolurea, methylolmelamine, diacetone alcohol, ethylenechlorohydrin, ethylenebromohydrin, 1 ,3-dichloro-2- propanol, acetocyanohydrin, 1 ,4-cyclohexyl-dimethanol or propane diol; mercaptans such as butyl mercaptan, hexyl mercaptan, tert-butyl mercaptan, tert- dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methylthiophenol or ethylthiophenol; acid amides such as acetoanilide, acetoanisidinamide, acrylamide, methacrylamide, acetamide, stearamide or benzamide; imides such as succinimide, phthalimide or maleimide; amines such as diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine or butylphenylamine; imidazoles such as imidazole or 2-ethylimidazole; ureas such as urea, thiourea, ethyleneurea, ethylenethiourea or 1 ,3-diphenylurea; carbamates such as phenyl N- phenylcarbamate or 2-oxazolidone; imines such as ethylenimine; oximes such as acetone oxime, formaldoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, diisobutyl ketoxime, diacetyl monoxime, benzophenone oxime or chlorohexanone oximes; salts of sulfurous acid such as sodium bisulfite or potassium bisulfite; hydroxamic esters such as benzyl methacrylohydroxamate (BMH) or allyl methacrylohydroxamate; or substituted pyrazoles, imidazoles or triazoles; and also 1 ,2-polyols such as ethylene glycol, propylene glycol, and 1 ,2-butanediol; 2-hydroxy esters such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate; and mixtures of these blocking agents BA.

[0131] The amount of the above-described crosslinker CL In the electrocoating materials (ECMs) of the invention is guided in particular by their functionality with regard to the crosslinking reaction with the cationic polymer particles being present in the aqueous dispersion (AD) and the binder B described previously and may therefore readily be determined by the skilled worker on the basis of his or her general art knowledge.

[0132] Pigment

[0133] The inventive aqueous electrocoating materials (ECMs) further comprise at least one pigment. The pigments are preferably selected from the group consisting of customary and known color pigments, fluorescent pigments, extender pigments, and anticorrosion pigments. The total amount of pigments, based in each case on the total weight of the aqueous electrocoating material (ECM), is preferably in the range from 0.1 to 30 wt.% or in the range from 0.1 to 20 wt.%, more preferably in the range from 0.1 to 15 wt.%, very preferably in the range from 0.1 to 10 wt.%, and more particularly in the range from 0.1 to 5 wt.%, or in the range from 0.1 to 4 wt.%, or in the range from 0.1 to 3.5 wt.%. The pigment or pigments are typically employed in form of pigment pastes. Any solvents and / or binders contained in the pigment paste are not part of the pigment, but part of the volatile content of the electrocoating material (ECM) or of the binder B, respectively, and thus belong in terms of weight percentages to the non-pigment components of the electrocoating material (ECM).

[0134] Additives

[0135] The inventive electrocoating material (ECM) may further comprise at least one customary additive. The expression "additive” defines the presence of a substance as a molecularly independent unit in the aqueous electrocoating material (ECM) and in particular not as a component incorporated reactively into a binder, resin, or the like. Suitable additives include fillers such as calcium sulfate, barium sulfate, silicates such as talc or kaolin, silicas, oxides such as aluminum hydroxide or magnesium hydroxide, nanoparticles, organic fillers; free-radical scavengers; slip additives; polymerization inhibitors; defoamers; emulsifiers, especially nonionic emulsifiers such as alkoxylated alkanols and polyols, phenols and alkylphenols or anionic emulsifiers such as alkali metal salts or ammonium salts of alkanecarboxylic acids, alkanesulfonic acids, and sulfo acids of alkoxylated alkanols and polyols, phenols and alkylphenols; wetting agents such as siloxanes, fluorine compounds, carboxylic monoesters, phosphoric esters, polyacrylic acids and their copolymers, or polyurethanes; adhesion promoters; leveling agents; film-formation auxiliaries such as cellulose derivatives; flame retardants; organic solvents; low molecular mass, oligomeric and high molecular mass reactive diluents which can participate in thermal crosslinkings, especially polyols such as tricyclodecanedimethanol, dendrimeric polyols, hyperbranched polyesters, polyols based on metathesis oligomers or branched alkanes having more than eight carbon atoms in the molecule; anticrater agents; polyvinyl alcohol polymers and mixtures thereof. The total amount of additive, based on the total weight of the aqueous electrocoating material (ECM), is preferably 0.1 to 20 wt.%, more preferably 0.1 to 15 wt.%, very preferably 0.1 to 10 wt.%, especially preferably 0.1 to 5 wt.%, and more particularly 0.1 to 2.5 wt.%. The additives belong per definition to the binders.

[0136] Catalyst

[0137] The inventive electrocoating material (ECM) may further comprise at least one crosslinking catalyst. Suitable catalysts are organic and inorganic salts and complexes of tin, lead, antimony, bismuth, iron or manganese, preferably inorganic and organic salts, and complexes of bismuth and of tin.

[0138] Preferred tin catalysts are selected from dibutyltin oxide or dibutyltin dilaurate.

[0139] Preferred inorganic salts of bismuth include bismuth subnitrate. Preferred organic salts and complexes of bismuth are selected from bismuth subsalicylate, bismuth lactate, bismuth ethylhexanoate and bismuth dimethylolpropionate. With particular preference, bismuth subsalicylate or bismuth subnitrate is used as crosslinking catalyst.

[0140] Based on their solids, the electrocoating materials (ECMs) of the invention preferably contain a total amount of catalyst, in particular bismuth subsalicylate, of 0.05 to 5 wt.%, more preferably of 0.1 to 4 wt.%, and in particular of 0.2 to 4 wt.%. The catalysts belong per definition to the binders.

[0141] Preparation of aqueous electrocoating materials (ECMs)

[0142] The electrocoating materials (ECMs) of the invention are prepared by mixing and homogenizing the abovedescribed constituents (a), (b) and (d) and optionally (c), (e) and (f), using customary and known mixing techniques and apparatus such as stirred tanks, stirred mills, extruders, kneading apparatus, Ultraturrax, inline dissolvers, static mixers, micromixers, toothed-gear dispersers, pressure relief nozzles and / or microfluidizers. With particular preference, the aqueous dispersion (AD) is mixed with binder B including, if present, crosslinker CL before adding the pigment paste and further additives. The pigments and bismuth containing catalysts are preferably incorporated in the form of pigment pastes or pigment preparations into the electrocoating materials (ECMs) (of. Rompp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, N.Y., 1998, "Pigment preparations”, page 452).

[0143] What has been said about the inventive aqueous dispersion (AD) and inventive process to produce the aqueous dispersion (AD) applies mutatis mutandis with respect to further preferred embodiments of the inventive aqueous electrocoating composition.

[0144] Inventive process to produce an at least partially coated substrate

[0145] The inventive aqueous electrocoating material (ECM) can be used to coat an electrically conductive substrate, such as a metal substrate, at least partially. The electrically conductive substrate preferably comprises a motor vehicle or part thereof.

[0146] Thus, a further subject-matter of the present invention is a process for producing an at least partially coated substrate by contacting the substrate with the inventive aqueous electrocoating material (ECM), forming a film from said material and curing the formed film. The process can further include rinsing the formed film and applying at least one further coating layer onto the cured electrocoating material (ECM).

[0147] Step (i)

[0148] In step (I) of the inventive method, the substrate is a least partially contacted with the inventive aqueous electrocoating material (ECM) to form a coating film of the aqueous electrocoating material. "Contacting” in the sense of the present invention refers to the application of the aqueous electrocoating material (ECM) to the substrate. The application of the electrocoating material (ECM) to the substrate, or the production of a coating film on the substrate, are understood as follows: the electrocoating material (ECM) is applied in such a way that the coating film produced therefrom is arranged on the substrate but need not necessarily be in direct contact with the substrate. Thus, other layers can be present between the coating film and the substrate. For example, a conversion coating, such as a zinc phosphate coating, may be arranged between the substrate and the cured electrocoating layer. This application can be achieved, for example, by immersing the substrate in the aqueous electrocoating material (ECM) or by spraying or roll application of said material onto the substrate. With preference, application is achieved by immersing the substrate in said material. With preference, the coating of the substrate in step (I) is done by electrophoretic, preferably cataphoretic, deposition of this coating material onto substrate surface. This is accomplished by introducing the substrate at least partly, preferably completely, preferably into a dip-coating bath containing the inventive electrocoating material (ECM) and applying an electrical voltage between the substrate and at least one counter electrode. The counter electrode may in this case be located in the dip coating bath. Alternatively, or additionally, the counter electrode may also be present separately from the dip-coating bath, for example via an anion exchange membrane which is permeable to anions. In this case, anions formed during dip coating are transported from the coating material through the membrane into the anolyte, allowing the pH in the dip-coating bath to be regulated or kept constant. The counter electrode is preferably separate from the dip-coating bath. The passage of electrical current between anode and cathode is accompanied by deposition of a firmly adhering paint film on the cathode, i.e., on the substrate.

[0149] Step (I) of the method of the invention is carried out preferably at a temperature in a range from 25 to 38°C and a voltage of 100 to 400 V, preferably of 140 to 350 V. The voltage may be kept constant during the stated duration. Alternatively, however, the voltage may also adopt different values during the deposition duration within the minimum and maximum previously listed - for example, it may swing back and forth or rise in ramp or step form from the minimum to the maximum deposition voltage. In step (I) of the method of the invention, preferably, there is full coating of the substrate with the aqueous electrocoating material (ECM) of the invention, by complete electrophoretic, preferably cataphoretic, deposition on the entire substrate surface.

[0150] In step (I) of the method of the invention, the aqueous electrocoating material (ECM) of the invention is preferably applied such that the resulting cured electrocoat film has a dry film thickness in the range from 5 to 70 pm, more preferably from 10 to 60 pm, especially preferably from 10 to 45 pm. Typically, in OEM (original equipment manufacturing) coating processes the dry layer thickness is in the range from 15 to 25 pm, while in ASM (automotive supply metal) coating processes the dry layer thickness is typically in the range from 20 pm to 45 pm.

[0151] Optional step (ii)

[0152] In step (II), the coating film formed in step (I) may be rinsed with an aqueous medium. In one example, the aqueous medium primarily contains water but also may contain further additives in small amounts. In another example, the aqueous medium consists of ultrafiltrate obtained from the aqueous electrocoating material (ECM). The implementation of optional step (ii) allows to recycle excess aqueous electrocoating material (ECM), present after step (i) on the at least partly coated substrate, into the dip-coating bath.

[0153] Step (Hi):

[0154] In step (iii) of the inventive method, the coating film obtained from at least partially applying the inventive aqueous electrocoating material (ECM) on the substrate after step (I) or (II) is cured.

[0155] Curing of the electrocoating film is understood to mean the conversion of such a film to the ready-to-use state, i.e. , to a state in which the substrate provided with the respective coating film can be transported, stored, and used as intended. More particularly, a cured coating film is no longer soft or tacky, but has been conditioned as a solid coating film which does not undergo any further significant change in its properties, such as hardness or adhesion on the substrate, even under further exposure to curing conditions.

[0156] Step (iii) of the method of the invention is carried out preferably by means of baking after step (I) or (ii), preferably in an oven. The curing here takes place preferably at a substrate temperature in the range from 100 to 250 °C, more preferably 130 to 190 °C. Step (iii) takes place preferably over a duration of 10 to 40 minutes, more preferably 15 to 30 minutes.

[0157] Optional step (iv):

[0158] After curing the coating layer in step (iii), at least one further coating layer may be applied on the cured coating layer. The resulting electrocoat can then be overcoated with a surfacer or with a primer and a solid-color topcoat material or, alternatively, with a basecoat material and a clearcoat material by the wet-on-wet technique. The surfacer film or primer film and also the solid-color topcoat film are preferably each baked individually. The basecoat film and the clearcoat film are preferably baked together. This procedure results in multicoat paint systems having outstanding performance properties. What has been said about the inventive aqueous dispersion (AD), the inventive process to produce the aqueous dispersion (AD) and the inventive aqueous electrocoating composition (ECM) applies mutatis mutandis with respect to further preferred embodiments of the inventive process to produce an at least partially coated substrate.

[0159] Inventive coated substrate

[0160] A further subject of the present invention is an at least partly coated electrically conductive substrate which is obtainable by means of the method of the invention.

[0161] What has been said about the inventive aqueous dispersion (AD), the inventive process to produce the aqueous dispersion (AD), the inventive aqueous electrocoating composition (ECM) and the inventive process to produce an at least partially coated substrate applies mutatis mutandis with respect to further preferred embodiments of the inventive coated substrates.

[0162] The substrates used in the present invention are preferably metallic substrates such as pure metals or alloys, which may be uncoated or coated with conversion coating layers such as zinc phosphate layers. Suitable metallic substrates are, e.g., bare steel, cold rolled steel, electrogalvanized steel, hot-dip galvanized steel, zinc and its alloys and aluminum and its alloys.

[0163] The shape of the substrates can be any, such as flat panels or 3-dimensionally curved substrates. Preferred substrates are vehicle bodies and parts thereof, such as used in automotive coating.

[0164] EXPERIMENTAL PART

[0165] The present invention will now be explained in greater detail by use of working examples, but the present invention is in no way limited to these working examples. Moreover, the terms "parts", "%" and "ratio" in the examples denote "parts by mass", "mass %" and "mass ratio" respectively unless otherwise indicated.

[0166] Analytical Methods

[0167] Solids content (solids, nonvolatile fraction)

[0168] Unless stated otherwise, the solids content (also called proportion of solids, solid-state content, proportion of nonvolatiles) was determined to DIN EN ISO 3251 : 2019-09 at 130°C for 60 min with a sample starting weight of 1 .0 g; and in the same way, but at 180 °C for 30 min in case of electrocoating materials.

[0169] Epoxy equivalent weight

[0170] The epoxy equivalent weight was determined according to DIN EN ISO 3001 :2019-08.

[0171] Average particle size (z-mean)

[0172] The average particle size (z-mean) of the cationic particles contained in the aqueous dispersion (AD) was determined according to DIN EN ISO 22412:2018-09.

[0173] Corrosion Testing General Remarks Applicable to Salt spray test (SST) and VDA climate change test

[0174] If the coating to be tested is present on a metallic substrate having holes, these holes simulate a real-life metallic substrate having a comparably high number of edges I edge zones. Also, in case of substrates having holes whose edges are not post processed, like, for example, sanded or polished before any pretreatment and coating processes start, these substrates are even more challenging in terms of coating and thus corrosion edge protection. The degree of corrosion on the edges of these holes (also called "edges of holes corrosion” or "edge corrosion”) may be assessed visually by observing the degree I portion of the hole edge being corroded after the SST and climate change test (rating scale from 0 to 5, wherein "5” means 100 % corrosion (the whole edge of the hole is corroded) and "0” means 0 % corrosion). Salt spray test (SST)

[0175] The corrosion resistance of coatings is determined by a salt spray test. The salt spray testing is carried out according to DIN EN ISO 9227 NSS (date: September 2012) for the coated substrate under study. The samples under study are accommodated in a chamber in which at a temperature of 35°C - continuously over duration of 504 hours or 1008 hours - a mist is produced from a 5% strength sodium chloride solution with a controlled pH in the range from 6.5 to 7.2. The mist deposits on the samples under study and covers them with a corrosive saltwater film.

[0176] If prior to the salt spray testing according to DIN EN ISO 9227 NSS, the coating on the samples under study is scored down to the substrate with a blade incision, the samples can be investigated for their level of corrosive undermining to DIN EN ISO 4628-8 (03- 2013), since the substrate corrodes along the score line during the DIN EN ISO 9227 NSS salt spray testing. As a result of the progressive process of corrosion, the coating is undermined to a greater or lesser extent during the test. The extent of undermining in [mm] is a measure of the resistance of the coating to corrosion.

[0177] Each rating result shown further below is the average of 3 individual test results. Each individual test result was generated by means of an individual panel (i.e. , coated test substrate). In case the individual panel exhibits seven individual holes, the individual test result of one individual panel on edges of holes protection thus itself is an average of analysis of the seven individual holes.

[0178] VDA climate change test

[0179] The VDA climate change test is used to determine the corrosion resistance of a coating on a substrate and is either performed according to DIN EN ISO 11997-1 :2018-01 (denoted VDA1 hereinafter) in 5 or 10 so-called cycles or according to VDA 233-102 (June 2013) in 12 so-called cycles (denoted VDA2 hereinafter).

[0180] If the coating of the samples to be tested is scored down to the substrate with a knife cut before the climate change test is performed, the samples can be tested for their degree of under-film corrosion in accordance with DIN EN ISO 4628-8 (03-2013), since the substrate corrodes along the scoring line during the climate change test. As corrosion progresses, the coating is more or less infiltrated during the test. The degree of undermining in [mm] is a measure of the corrosion resistance of the coating (so called scribe corrosion).

[0181] Each rating result shown further below is the average of 3 individual test results. Each individual test result was generated by means of an individual panel (i.e., coated test substrate). In case the individual panel exhibits seven individual holes, the individual test result of one individual panel on edges of holes protection thus itself is an average of analysis of the seven individual holes. Surface Roughness

[0182] The surface roughness is determined according to DIN EN 10049:2014-03.

[0183] Dry Layer Thickness (DLT)

[0184] The DLT is determined according to DIN EN ISO 2178:2016-11.

[0185] Preparation of Aqueous Dispersion

[0186] Preparation of a Comparative Aqueous Dispersion (CAD1 to CAD4)

[0187] 13.3 parts of a liquid epoxy resin (EEW = 184 to 189 g / Eq.) (substance (A)), 6.1 parts bisphenol A (substance (B)) and 2.2 parts of phenoxy propanol were mixed in a reactor and heated to 150 °C before 0.036 parts of P-containing catalyst were added. The contents of the reactor were cooled to 130 °C and stirring was continued until the EEW of the obtained reaction product is greater than 1097 g / Eq. Afterwards, the mixture was diluted with 3.7 parts of an alkanol and cooled to 105 °C before 2.2 parts of amine substance (D) (di-ketimin of diethylentriamine; methylethyl keton was used) were added over the course of 30 minutes. The resulting mixture was diluted with 5.4 parts of alkanol and 22 parts of water. Afterwards, 0.38 parts of formic acid (substance (E)) were added and the mixture was dispersed in 44.4 parts of water and 0.34 parts of an alkanol to obtain the aqueous dispersion having a solids content of around 22 wt.% and an average particle size (z-mean) of around 100 nm.

[0188] Preparation of Inventive Aqueous Dispersions (AD1 to AD10)

[0189] AD1

[0190] 10.115 parts of a liquid epoxy resin (bisphenol A based; EEW = 184 to 189 g / Eq., used in all Examples as "Liquid Epoxy Resin”) (substance 1 table S1), 4.001 parts of a polypropylenglycol diglycidyl ether (epoxy equivalent weight = 320 to 450 g / Eq.) (substance 2 table S1), 5.223 parts bisphenol A (substance 5 table S1) and 2.153 parts of phenoxy propanol (substance 4 table S1) were mixed in a reactor and heated to 125 to 150 °C before 0.038 parts of P-containing catalyst (substance 6 table S1) were added. The contents of the reactor were cooled to 130 °C and stirring was continued until the EEW of the obtained reaction product is greater than 1033 g / Eq. Afterwards, the mixture was diluted with 9.428 parts of an alkanol (substance 7 table S1) and cooled to 105 °C before 2.247 parts of amine (di-ketimin of diethylentriamine; methyl ethyl ketone was used) (substance 8 table S1) were added over the course of 5 to 10 minutes and 30min further stirring to homogenize the reaction mixture. The resulting mixture was diluted with 21.960 parts of water (substance 9 table S1). Afterwards, 0.392 parts of formic acid (substance 10 table S1) were added, and the mixture further diluted by 44.444 parts of water (substance 11 table S1) to obtain the aqueous dispersion having a solids content of around 21 wt.% and an average particle size (z-mean) of around 150 nm. AD2

[0191] The synthesis was carried out in analogy to AD1. Composition according to table S1 , (with epoxy weight to be exceeded: 1037 g / eq for AD2)

[0192] AD3 and AD4

[0193] The synthesis was carried out in analogy to AD1 . Composition according to table S1 . Instead of (substance 2 table S1 ), (substance 3, i.e. polypropylenglycol diglycidyl ether with epoxy equivalent weight of 1000 to 1300 g / eq., table S1) was used for aliphatic epoxy, (with epoxy weight to be exceeded: 1084 g / eq for AD3; with epoxy weight to be exceeded: 1028 g / eq for AD4).

[0194] Table S1 - Microgels (MG)

[0195] AD5

[0196] 12.778 parts of a liquid epoxy resin (EEW = 184 to 189 g / Eq.) (substance 1 table S2), 5.098 parts bisphenol A (substance 3 table S2), 2.155 parts of phenoxy propanol (substance 2 table S2) and 1.485 parts of dimeric fatty acid (substance 4 table S2; acid value: 196 mg KOH / g, dimer content > 96 wt.-%, monomers < 2 wt.-% and trimers < 1 wt.-%; use in all Examples as "Dimer Fatty Acid”) were mixed in a reactor and heated to 125 to 150 °C before 0.037 parts of P-containing catalyst (substance 5 table S2) were added. The contents of the reactor were cooled to 130 °C and stirring was continued until the EEW of the obtained reaction product is greater than 1077 g / Eq. Afterwards, the mixture was diluted with 9.438 parts of(substance 6 table S2) and cooled to 105 °C before 2.167 parts of amine (di-ketimin of diethylentriamine) (substance 7 table S2) were added over the course of 5 to 10 minutes and 30min further stirring to homogenize the reaction mixture. The resulting mixture was diluted with 22.018 parts of water (substance 8 table S2). Afterwards, 0.738 parts of formic acid (substance 9 table S2) were added and the mixture further diluted by 44.444 parts of water (substance 10 table S2) to obtain the aqueous dispersion having a solids content of around 21 wt.% and an average particle size (z-mean) of around 101 nm.

[0197] AD6 to AD8

[0198] The synthesis was carried out in analogy to example AD5. Composition according to table S2 (with epoxy weight to be exceeded: 1075 g / eq for AD6; with epoxy weight to be exceeded: 1087 g / eq for AD7; with epoxy weight to be exceeded: 1073 g / eq for AD8)

[0199] Table S2 - Microgels (MG)

[0200] AD9

[0201] 9.801 parts of a liquid epoxy resin (EEW = 184 to 189 g / Eq.) (substance 1 table S3), 4.014 parts of poly propyl eng ly col diglycidyl ether with epoxy equivalent weight of 1000 to 1300 g / eq (substance 3 table S3), 3.502 parts bisphenol A (substance 5 table S3), 2.151 parts of phenoxy propanol (substance 4 table S3) and 2.003 parts of dimeric fatty acid (substance 6 table S3) were mixed in a reactor and heated to 125 to 150 °C before 0.039 parts of P-containing catalyst (substance 7 table S2) were added. The contents of the reactor were cooled to 130 °C and stirring was continued until the EEW of the obtained reaction product is greater than 1048 g / Eq. Afterwards, the mixture was diluted with 9.419 parts of an alkanol (substance 8 table S3) and cooled to 105 °C before 2.310 parts of amine (di-ketimin of diethylentriamine) (substance 9 table S3) were added over the course of 5 to 10 minutes and 30min further stirring to homogenize the reaction mixture. The resulting mixture was diluted with 21.913 parts of water (substance 10 table S3). Afterwards, 0.403 parts of formic acid (substance 11 table S3) were added and the mixture further diluted by 44.444 parts of water (substance 12 table S3) to obtain the aqueous dispersion having a solids content of around 21 wt.% and an average particle size (z-mean) of around 101 nm. AD10A and AD10B

[0202] The synthesis was carried out in analogy to AD9 (with epoxy weight to be exceeded: 1090 g / eq for AD10A; with epoxy weight to be exceeded: 745 g / eq for AD10B). Instead of substance 3 table S3, substance 2 table S3 was used for aliphatic epoxy. Table S3 - Microgels (MG)

[0203] AD10C

[0204] 8.205 parts of a liquid epoxy resin (EEW = 184 to 189 g / Eq.) (substance 1 table S4), 4.113 parts of poly propylenglycol diglycidyl ether with epoxy equivalent weight of 320 to 450 g / eq (substance 2 table S4), 2.252 parts bisphenol A (substance 6 table S4), 2.156 parts of phenoxy propanol (substance 5 table S4) and 4.798 parts of dimeric fatty acid (substance 7 table S4) were mixed in a reactor and heated to 125 to 150 °C before 0.037 parts of P-containing catalyst (substance 10 table S4) were added. The contents of the reactor were cooled to 130 °C and stirring was continued until the EEW of the obtained reaction product is greater than 1090 g / Eq. Afterwards, the mixture was diluted with 9.441 parts of an alkanol (substance 11 table S4) and cooled to 105 °C before 2.143 parts of amine (di-ketimin of diethylentriamine) (substance 12 table S4) were added over the course of 5 to 10 minutes and 30min further stirring to homogenize the reaction mixture. The resulting mixture was diluted with 22.035 parts of water (substance 13 table S4). Afterwards, 0.374 parts of formic acid (substance 14 table S4) were added and the mixture further diluted by 44.444 parts of water (substance 15 table S4) to obtain the aqueous dispersion having a solids content of around 21 wt.% and an average particle size (z-mean) of around 295 nm.

[0205] AD10D

[0206] The synthesis was carried out in analogy to AD10C according to table S4 (with epoxy weight to be exceeded: 745 g / eq). Instead of a single polypropylenglycol diglycidyl ether with epoxy equivalent weight of 320 to 450 g / eq (substance 2 table S4), therefore (substance 2 and 3 (polypropylenglycol diglycidyl ether with epoxy equivalent weight of 1000 to 1300 g / eq.), table S4) were used.

[0207] Table S4 - Microgels (MG) Preparation of Electro Deposition Coating Materials (ECM)

[0208] For testing as cathodically depositable electrocoat materials (ECM), the aqueous binder dispersion (BD) (aqueous dispersion of a cationic binder B) and a crosslinking agent CL (commercially available product CathoGuard® 570 from BASF with a solids content as indicated (based on total weight)), the pigment paste (PP) (aqueous pigment paste (commercially available product CathoGuard® 570 from BASF with a solids content as indicated)), the respective aqueous dispersion(s) (AD) described above are combined in accordance with Tables E1 to E6 below. The procedure here is to introduce the binder dispersion (BD) as an initial charge and to dilute it with deionized water. Subsequently, with stirring, the respective aqueous dispersion(s) (AD) are added. Afterwards, the pigment paste (PP) are introduced with stirring. In all cases, a stable aqueous electrocoating composition was obtained.

[0209] Table E1

[0210] Table E2 Table E3

[0211] Table E4 Table E5

[0212] Table E6 Preparation of coated substrates

[0213] As test panels different substrates have been used, namely substrates S1 (bare steel, degreased), S2 (steel substrates pretreated with a phosphatizing composition (Gardobond® GB26S 6800 OC)) and S3 (galvanized steel substrates pretreated with a phosphatizing composition (Gardobond® GB26S 6800 OG)). Prior to coating said substrates with the electrocoating materials, a strip was cut off at an edge of substrate S1 using tin snips. Before pretreatment of substrates S2 and S3, said substrates were punched to result in seven individual holes. These holes and their edges, respectively, were not sanded or polished, meaning that they resemble respective non- sanded / polished edges of real-life substrates. The comparative electrocoating materials (CECM) and inventive electrocoating material (ECM) prepared as described above are aged at room temperature with stirring for 24 h, respectively. The electrocoat materials are then each deposited on substrates S1 to S3 connected as cathodes within 2 to 3 minutes at a bath temperature of 32 to 33 °C, rinsed with deionized water and baked in an oven at 175 °C (oven temperature) for 25 minutes (oven time). In case of substrate S1 , a deposition voltage of 140 to 160 V was used while the electrocoating materials on substrates S2 and S3 were deposited using 140 to 260 V.

[0214] Results

[0215] The corrosion resistance, especially the edge corrosion resistance, the surface roughness as well as the dry layer film thickness of the cured electrocoating material prepared as described above was determined as described. The results are listed in the following Tables R1 to R6.

[0216] In Result Tables R1 and R2 it is shown that an improvement in the corrosion resistance after salt spray test conditions (1008h; hole panels) regarding the average scribe corrosion is observed. The results in Table R1 obtained for a lower amount of the polypropylene glycol diglycidyl ether based inventive aqueous dispersions in the electrocoating material already show an improvement, while the improvement is even more significant at a higher amount (Table R2). Particularly, there is a big improvement in surface roughness at the higher amount of the inventive aqueous dispersion.

[0217] Table R1 Table R2

[0218] In Result Table R3 it is shown that only a slight improvement in the corrosion resistance after salt spray test conditions (1008h; hole panels) and the VDA test regarding the average edge corrosion and surface roughness is observed. However, the results in Table R3 obtained for even a low amount of the dimer fatty acid based inventive aqueous dispersions in the electrocoating material show at least no drawback, but make use of a lower amount of aromatic moieties in the microgel compared to conventional microgels.

[0219] Table R3

[0220] In Result Table R4 it is shown that a significant improvement in the corrosion resistance after salt spray test conditions (1008h; hole panels) regarding the average scribe corrosion and surface roughness is observed for higher amounts of the dimer fatty acid based inventive aqueous dispersions in the electrocoating material compared to Table R3, which is also the case for a mixture of a polypropylene glycol diglycidyl ether based inventive aqueous dispersion with a dimer fatty acid based inventive aqueous dispersion in ECM 15.

[0221] Table R4

[0222] The results in Table R5 were obtained by the use of mixtures of polypropylene glycol diglycidyl ether and dimer fatty acid already in the production of microgel particles contained in the inventive aqueous dispersions. Even at the low concentrations of the aqueous dispersions used in the electrocoat material there is a significant improvement in edge protection while roughness remains at the same level as for the comparative example (CECM5). Table R5

[0223] Improvements in surface roughness, are, however, observed when higher amounts of aqueous dispersions containing microgels are used, when the microgels are obtained from mixtures of polypropylene glycol diglycidyl ether and dimer fatty acid in their production (see Table R6).

[0224] Table R6 In summary, from the above date, it is to be concluded that even if a low amount of the inventive aqueous dispersion containing the microgels is used in electrocoat materials, some slight improvements are observable or at least no detrimental effect, if compared to the comparative examples. At higher amounts significant improvements are shown with respect to surface roughness and corrosion resistance.

Claims

CLAIMS1 . Aqueous dispersion (AD) comprising cationic polymer particles, the cationic polymer particles comprising one or more amine functional epoxy addition resins, the amine functional epoxy addition resins being obtainable by(1) reacting a. at least one aromatic substance (A) comprising at least two epoxy groups; b. at least one aromatic substance (B) comprising at least two hydroxyl groups; c. at least one aliphatic substance (C) selected fromI. dicarboxylic acids (C1), and / or ii. polyalkylene glycol diglycidyl ethers (C2); and d. at least one amine substance (D); and(2) optionally reacting the product obtained in (1) with an acid substance (E).

2. Aqueous dispersion according to claim 1, characterized in that the at least one aromatic substance (A) comprises two epoxy groups, preferably the at least one aromatic substance (A) being a bisphenol diglycidyl substance.

3. Aqueous dispersion according to claim 1 or 2, characterized in that the at least one aromatic substance (B) comprises two hydroxyl groups, preferably two phenolic hydroxyl groups, preferably the at least one aromatic substance (B) being a bisphenol substance.

4. Aqueous dispersion according to any one of claims 1 to 3, wherein the dicarboxylic acids have the following general formula (I)HOOC-R-COOH (I), wherein R is a divalent aliphatic hydrocarbon residue, which comprises 4 to 48 carbon atoms.

5. Aqueous dispersion according to one or more of claims 1 to 4, characterized in that the dicarboxylic acid (C1) is a dimer fatty acid (C1) having a purity of at least 80 wt.-% of dimeric molecules based on its total weight, and / or the dimeric molecules in the dimer fatty acid (C1) comprise 24 to 44 carbon atoms.

6. Aqueous dispersion according to one or more of claims 1 to 5, characterized in that the polyalkylene glycol diglycidyl ether (C2) has the following general formula (I):whereinE0 = ethylene oxide unit, PO = propylene oxide unit and BO = butylene oxide unit, and each of x, y and z = 0 to 60, with the proviso that x + y + z = 5 to 60; and the ethylene oxide units, propylene oxide units and butylene oxide units can be arranged in any order.

7. Aqueous dispersion according to claim 6, characterized in that x and z = 0 and / or y is in the range from 5 to 60.

8. Aqueous dispersion according to one or more of claims 1 to 7, characterized in that the amine substance (D) comprises primary and / or secondary amino groups, the primary amino groups, if comprised, preferably being in blocked form; and / er the acid substance (E) being selected from inorganic acids and / or organic acids, preferably carboxylic acids.

9. Aqueous dispersion according to one or more of claims 1 to 8, characterized in that the total amount of (C), based on the total amount of (A), (B) and (C) is in the range from 1 to 60 wt.-%, preferably 5 to 55 wt.- %, more preferably 10 to 50 wt.-%.

10. Aqueous dispersion according to one or more of claims 1 to 9, characterized in that the molar amount of epoxy groups contained in (A) plus (C2) exceeds the combined molar amounts of hydroxy groups contained in (B) plus carboxy groups contained in (C1).11 . Aqueous dispersion according to one or more of claims 1 to 10, characterized in that the amount of dimer fatty acid (C1) is in the range from 5 to 95 wt.-%, preferably 10 to 90 wt.-%, more preferred 20 to 80 wt.- %, and most preferred 30 to 70 wt.-% based on the total amount of (C) and the amount of the polyalkylene glycol diglycidyl ether (C2) is in the range from 5 to 95 wt.-% preferably 10 to 90 wt.-%, more preferred 20 to 80 wt.-%, and most preferred 30 to 70 wt.-% based on the total amount of (C).

12. Aqueous dispersion according to one or more of claims 1 to 11 , characterized in that the cationic polymer particles possess a z-average particle size in the range from 50 to 1 ,000 nm; and / or the solids content of the cationic polymer particles in the aqueous dispersion is preferably 10 to 40 wt.%, more preferred 15 to 30 wt.%, based on the total weight of the aqueous dispersion (AD).

13. Process for preparing an aqueous dispersion (AD) comprising cationic polymer particles as defined in claims 1 to 12, said process comprising the steps of:(1) reacting a. at least one aromatic substance (A) comprising at least two epoxy groups;b. at least one aromatic substance (B) comprising at least two hydroxyl groups; c. at least one aliphatic substance (C) selected fromI. dicarboxylic acids (C1), and / or ii. polyalkylene glycol diglycidyl ethers (C2); and d. at least one amine substance (D); and to form a polymeric product;(2) dispersing the polymeric product obtained in (1) an aqueous medium and(3) optionally reacting the polymeric product obtained in (1) with an acid substance (E).

14. Process according to claim 13, characterized in that the epoxy groups of substance (A), and if present, the epoxy groups of substance (C2) are reacted with the hydroxyl groups of substance (B) and, if present, the carboxy groups of substance (C1 ), thus forming an epoxy group containing intermediate, the epoxy group containing intermediate being reacted under consumption of the epoxy groups with the amine substance (D), and subsequently reacting the amino groups of the thus obtained amine functional epoxy addition resin in an aqueous medium with an acid (E).

15. Aqueous electrocoating material (ECM) comprising(a) at least one aqueous dispersion (AD) as defined in any one or more of claims 1 to 12 or as prepared according to the process as defined in claims 13 or 14,(b) at least one further binder B being different from the cationic polymer particles contained in the aqueous dispersion (AD) and optionally containing a crosslinker (CL),(c) at least one pigment,(d) optionally at least one additive, and(e) optionally at least one catalyst.

16. Aqueous electrocoating material (ECM) according claim 15, characterized in that at least two aqueous dispersions (AD) as defined in any one or more of claims 1 to 12 or as prepared according to the process as defined in claims 13 or 14 are comprised, wherein in a first aqueous dispersion the aliphatic substance (C) is a dicarboxylic acid (C1) and in a second aqueous dispersion the aliphatic substance (C) is a polyalkylene glycol diglycidyl ether (C2).

17. Aqueous electrocoating material (ECM) according any one or more of claims 15 and 16, characterized in that the combined amounts of solid ingredients contained in the one or more aqueous dispersions (AD), are in the range from 0.1 to 1.5 wt.-%, preferably 0.2 to 1.2 wt.-% and more preferably 0.25 to 1.0 wt.-%, based on the total weight of the electrocoating material (ECM).

18. Process for producing an at least partially coated substrate, said process comprising the following steps:(i) at least partially contacting a substrate with an aqueous electrocoating material (ECM) as defined in claims 15 to 17, thus forming a coating film from the aqueous electrocoating material (ECM);(ii) optionally rinsing the coating film formed in step (i) with an aqueous medium;(iii) curing the coating film obtained after step (i) or optionally (ii); and (iv) optionally applying at least one further coating layer and curing said coating layer.

19. Process for producing an at least partially coated substrate according to claim 18, characterized in that the substrate is a metallic substrate selected from the group vehicle bodies and parts thereof.

20. An at least partially coated substrate obtainable by the process according to claim 18 or 19.

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