WO2003074617A1

WO2003074617A1 - Insoluble-solid-free electrodip coatings

Info

Publication number: WO2003074617A1
Application number: PCT/EP2003/001540
Authority: WO
Inventors: Michael Hartung; Karl-Heinz Grosse Brinkhaus; Ursula Kaletta; Margret Neumann
Original assignee: Basf Coatings Ag
Priority date: 2002-03-02
Filing date: 2003-02-15
Publication date: 2003-09-12
Also published as: AU2003206908A1

Abstract

The invention relates to insoluble-solid-free electrodip coatings (ETL), containing (A) at least one binder with (potentially) cationic or anionic groups and reactive function groups which can enter into thermal cross-linking reactions with complementary reactive groups present in components (B) and (C); (B) at least one blocked polyisocyanate and (C) at least one melamine-formaldehyde resin containing (c 1), on a statistical average, at least 1-4 triazine rings in the molecule and (c 2) in relation to the hydrogen atoms of the amino groups which were originally provided for reaction with formaldehyde (c 21) 10 - 40 mol % hydroxymethylene groups, (c 22) 50 - 85 mol % methoxymethylene or methoxymethylene and butoxymethylene groups and (c 23) 0 -15 mol % imino groups (> NH).

Description

Electrophoretic paints free from insoluble solids

The present invention relates to new electrodeposition paints (ETL) free of insoluble solids. In addition, the present invention relates to a new process for the production of ETL free from insoluble solids. Furthermore, the present invention relates to the use of the new ETL free of insoluble solids for the production of electrocoating.

Pigment-free, cathodically depositable ETL (KTL) are known, for example, from German patent applications DE 199 30 060 A1, DE 100 01 222 A1 or DE 100 52 438 A1. They contain cationic resins as binders and blocked polyisocyanates as crosslinking agents. In addition, they can contain additional crosslinking agents such as aminoplast resins, for example melamine, guanamine, benzoguanamine or urea resins. However, these are not specified in terms of their composition and quantities.

The known pigment-free KTL have the advantage over the pigment-containing ones that no pigment pastes and elaborate grinding processes have to be used to manufacture them. Otherwise, they already have good application properties and provide electrocoating with good properties.

However, they still have to be developed further so that they can also be supplied without the addition of pigments, in particular corrosion protection pigments, or other insoluble solids, such as microgels, and electro-dip coatings, which ensure excellent corrosion protection and edge protection. In addition, the unhardened or only partially hardened layers from the known pigment-free ETL are often difficult to mix with aqueous ones Overlay coating materials such as water primers or water fillers without problems and bake together.

The object of the present invention is to find new electrodeposition paints (ETL) which are free from insoluble solids and which can be produced just as easily as the known pigment-free ETL and which no longer have the disadvantages of the prior art, but which are in the form of a The deposited, unhardened or only partially hardened layer can be covered easily and trouble-free wet-on-wet with aqueous coating materials and baked together with them, and deliver electrocoating with excellent corrosion protection and edge protection.

Accordingly, the new electrodeposition paints (ETL) free of insoluble solids have been found to contain

(A) at least one binder with (potentially) cationic or anionic groups and reactive functional groups, the thermal with the complementary reactive functional groups present in the components (B) and (C)

Cross-linking reactions,

(B) at least one blocked polyisocyanate and

(C) containing at least one melamine-formaldehyde resin

(d) on average at least 1 to 4 triazine rings in the molecule and, (c 2) based on the hydrogen atoms of the amino groups which were originally available for the reaction with formaldehyde,

(c 21) 10 to 40 mol% of hydroxymethylene groups,

(c 22) 50 to 85 mol% of methoxymethylene or methoxymethylene and butoxymethylene groups and

(c 23) 0 to 15 mol% of imino groups (> NH).

In the following, the new electrodeposition paints (ETL) free of insoluble solids are referred to as “ETL according to the invention”.

With regard to the starid of technology, it was surprising and unforeseeable for the person skilled in the art that the object on which the invention is based could be achieved with the aid of the ETL according to the invention. In particular, it was surprising that the ETLs according to the invention were simple to produce and were stable in storage. They could easily be deposited electrophoretically on electrically conductive substrates. The deposited, unhardened or only partially hardened layers of the ETL according to the invention could be covered without problems wet-on-wet with aqueous coating materials, such as water primers or water fillers, and then baked together with them. The resulting electrocoating offered excellent corrosion protection and edge protection.

The ETLs according to the invention are free of insoluble solids.

The property "insoluble" means that the solid in question is in the aqueous media, as in the invention ETL are included and do not dissolve, or dissolve only very slowly, in conventional and known polar and non-polar organic solvents. Examples of insoluble solids are pigments, such as anti-corrosion pigments, or highly cross-linked microparticles or microgels.

The property "free from" means that the ETLs according to the invention contain no insoluble solids or only traces thereof, which, however, have no influence on the application properties of the ETLs according to the invention.

The ETL according to the invention preferably have a solids content of 5 to 50, preferably 5 to 35,% by weight. Here, “solid” is to be understood as the proportion of an ETL that builds up the electro-dip coating produced from it.

The ETL according to the invention contain at least one binder (A).

The binder (A) potentially contains cationic and / or cationic groups. Binders (A) of this type are used in cathodically depositable electrocoat materials (KTL).

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, in particular 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, 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.

Examples of suitable binders (A) for KTL are from the publications EP 0 082 291 A1, EP 0 234 395 A1, EP 0 227 975 A1, EP 0 178 531 A1, EP 0 333 327, EP 0 310 971 A. 1, EP 0 456 270 A1, US 3,922,253 A, EP 0 261 385 A1, EP 0 245 786 A1, EP 0 414 199 A1, EP 0 476 514 A1, EP 0 817 684 A1, EP 0 639 660A 1, EP 0 595 186 A1, DE 41 26 476 A1, WO 98/33835, DE 33 00 570 A1, DE 37 38 220 A1, DE 35 18 732 A1 or DE 196 18 379 A1 known. These are preferably primary, secondary, tertiary or quaternary amino or ammonium groups and / or resins (A) containing tertiary sulfonium groups with amine numbers, preferably between 20 and 250 mg KOH / g and a weight average molecular weight of preferably 300 to 10,000 daltons. In particular, amino (meth) acrylate resins, amino epoxy resins, amino epoxy resins are terminated

Double bonds, aminoepoxy resins with primary and / or secondary hydroxyl groups, amino polyurethane resins, amino group-containing polybutadiene resins or modified epoxy resin-carbon dioxide-amine reaction products are used.

Alternatively, the binder (A) can potentially contain anionic and / or anionic groups. Binders (A) of this type are used in anionically depositable electrocoat materials (ATL). Examples of suitable potentially anionic groups which can be converted into anions by neutralizing agents are carboxylic acid, sulfonic acid or phosphonic acid groups, in particular carboxylic acid groups.

Examples of suitable anionic groups are carboxylate, sulfonate or phosphonate groups, especially carboxylate groups.

Examples of suitable neutralizing agents for the potentially anionic groups are ammonia, ammonium salts, such as, for example, ammonium carbonate or ammonium hydrogen carbonate, and amines, such as, for example, Trimethylamine, triethylamine, tributylamine, dimethylaniline, diethylaniline, triphenylamine, dimethylethanolamine, diethylethanolamine, methyldiethanolamine, triethanolamine and the like.

Examples of suitable binders (A) for ATL are known from German patent application DE 28 24 418 A1. These are preferably polyesters, epoxy resin esters, poly (meth) acrylates, maleate oils or polybutadiene oils with a weight average molecular weight of 300 to 10,000 daltons and an acid number of 35 to 300 mg KOH / g.

In general, the amount of neutralizing agent is chosen so that 1 to 100 equivalents, preferably 50 to 90 equivalents, of the potentially cationic or potentially anionic groups of a binder (A) are neutralized.

Furthermore, the binders (A) contain reactive functional groups which can undergo thermal crosslinking reactions with the complementary reactive functional groups present in the components (B) and (C) described below. Examples of more suitable reactive functional groups are hydroxyl groups, thiol groups and primary and secondary amino groups, especially hydroxyl groups.

KTL are preferably used as ETL.

The content of the above-described binders (A) in the ETL according to the invention depends primarily on their solubility and dispersibility in the aqueous medium and on their functionality with regard to the crosslinking reactions with the constituents (B) and (C) and can therefore be described by the person skilled in the art on the basis of his general Expertise, if necessary with the help of simple preliminary tests.

The ETL according to the invention contain at least one blocked polyisocyanate (B).

The blocked polyisocyanates (B) are produced from customary and known paint polyisocyanates with aliphatic, cycloaliphatic, araliphatic and / or aromatically bound isocyanate groups.

Lacquer polyisocyanates with 2 to 5 isocyanate groups per molecule and with viscosities of 100 to 10,000, preferably 100 to 5,000 and in particular 100 to 2,000 mPas (at 23 ° C.) are preferably used. In addition, the lacquer polyisocyanates can be modified in a conventional and known manner to be hydrophilic or hydrophobic.

Examples of suitable paint polyisocyanates are described, for example, in "Methods of Organic Chemistry", Houben-Weyl, Volume 14/2, 4th Edition, Georg Thieme Verlag, Stuttgart 1963, pages 61 to 70, and by W. Siefken, Liebigs Annalen der Chemie, Volume 562, pages 75 to 136. Further examples of suitable lacquer polyisocyanates are isocyanurate, biuret, allophanate, iminooxadiazinedione, urethane, urea, carbodiimide and / or uretdione polyisocyanates which are obtainable from customary and known diisocyanates. Preferred diisocyanates are hexamethylene diisocyanate, isophorone diisocyanate, 2-isocyanatopropylcyclohexyl isocyanate, dicyclohexyl methane-2,4'-diisocyanate, dicyclohexyl methane-4,4'-diisocyanate or 1,3-

Bis (isocyanatomethyl) cyclohexane (BIC), diisocyanates derived from dimer fatty acids, 1,8-diisocyanato-4-isocyanatomethyl-octane, 1,7-diisocyanato-4-isocyanatomethyl-heptane, 1-isocyanato-2- (3-isocyanatopropyl) Cyclohexane, 2,4- and / or 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, naphthalene diisocyanate or mixtures of these polyisocyanates are used.

Examples of suitable blocking agents for the preparation of the blocked polyisocyanates (B) are

i) phenols, such as phenol, cresol, xylenol, nitrophenol, chlorophenol, ethylphenol, t-butylphenol, hydroxybenzoic acid, esters of this acid or 2,5-di-tert-butyl-4-hydroxytoluene;

ii) lactams, such as ε-caprolactam, δ-valerolactam, γ-butyrolactam or ß-propiolactam;

iii) active methylenic compounds such as diethyl malonate, dimethyl malonate, ethyl or methyl acetoacetate or acetylacetone;

iv) alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, n-amyl alcohol, t-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 acid ester, lactic acid, lactic acid ester, methylolurea, methylolmelamine, diacetone alcohol, ethylene chlorohydrin,

Ethylene bromohydrin, 1, 3-dichloro-2-propanol, 1,4-

Cyclohexyldimethanol or acetocyanhydrin;

v) mercaptans such as butyl mercaptan, hexyl mercaptan, t-butyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole,

Thiophenol, methylthiophenol or ethylthiophenol;

vi) acid amides such as acetoanilide, acetoanisidinamide, acrylamide, methacrylamide, acetic acid amide, stearic acid amide or benzamide;

vii) imides such as succinimide, phthalimide or maleimide;

viii) amines such as diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine or butylphenylamine;

ix) imidazoles such as imidazole or 2-ethylimidazole;

x) ureas such as urea, thiourea, ethylene urea, ethylene thiourea or 1,3-diphenylurea;

xi) carbamates such as phenyl N-phenylcarbamate or 2-oxazolidone;

xii) imines such as ethyleneimine; xiii) oximes such as acetone oxime, formal doxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, diisobutyl ketoxime, diacetyl monoxime,

Benzophenone oxime or chlorohexanone oximes;

xiv) salts of sulfurous acid such as sodium bisulfite or potassium bisulfite;

xv) hydroxamic acid esters such as benzyl methacrylohydroxamate (BMH) or allyl methacrylohydroxamate; or

xvi) substituted pyrazoles, imidazoles or triazoles; such as

xvii) mixtures of these blocking agents.

The ETL according to the invention further contain at least one melamine-formaldehyde resin (C).

The statistical average of the melamine-formaldehyde resin (C) contains at least 1 to 4, in particular 2 to 3, triazine rings in the molecule. Based on the hydrogen atoms of the amino groups originally available for the reaction with formaldehyde, (C) contains 10 to 40, in particular 25 to 35, mol% of hydroxymethylene groups, 50 to 85, preferably 60 to 70, mol% of methoxymethylene or methoxymethylene and butoxymethylene groups, in particular 60 to 70 mol% of methoxymethylene groups, and 0 to 15, in particular 0 to 3 mol% of an imino group (> NH).

The melamine-formaldehyde resins (C) to be used according to the invention are known compounds which are commercially available. An example of a suitable melamine-formaldehyde resin (C) is Cymel® 370, which is sold by the company CYTEC. In the ETL according to the invention, the weight ratio of component (B) to component (C) can vary widely. Component (B) is preferably used in excess. The weight ratio of (B): (C) is preferably 1.1: 1 to 20: 1, particularly preferably 1.5: 1 to 15: 1 and in particular 2: 1 to 10: 1.

The content of the components (B) and (C) of the ETL according to the invention can vary widely and depends on the requirements of the individual case. The content, based on the solid of a respective ETL, is preferably 20 to 40, in particular 25 to 35,% by weight.

The ETL according to the invention preferably also contain at least one customary and known catalyst (D) for thermal crosslinking, such as inorganic and organic salts and complexes of tin, lead, antimony, bismuth, iron or manganese, preferably organic salts and complexes of bismuth and tin , preferably bismuth, especially bismuth lactate, ethylhexanoate or dimethylol propionate.

In addition, the ETL according to the invention can also contain at least one customary and known, soluble and / or dispersible additive (E) selected from the group consisting of anti-crater additives; crosslinking agents other than ingredients (B) and (C) described above; polyvinyl alcohols; thermally curable reactive thin; molecularly dispersible dyes; Light stabilizers such as UV absorbers and reversible radical scavengers (HALS); antioxidants; low and high boiling ("long") organic solvents; Venting means; Wetting agents; emulsifiers; slip additives; polymerization inhibitors; thermolabile free radical initiators; Adhesion promoters; Leveling agents; film-forming aids; Flame retardants; Corrosion inhibitors; anti-caking agents; To grow; driers; Biocides and matting agents, contained in effective amounts.

Further examples of suitable soluble and / or dispersible additives (E) are described in the textbook “Lackadditive” by Johan Bieleman, Wiley-VCH, Weinheim, New York, 1998, in D. Stoye and W. Freitag (Editors), “Paints, Coatings and Solvents «, Second, Completely Revised Edition, Wiley-VCH, Weinheim, New York, 1998,» 14.9. Solvent Groups «, pages 327 to 373, described in detail.

The ETLs according to the invention are produced by mixing and homogenizing the constituents described above with the aid of customary and known mixing processes and devices such as stirred kettles, agitator mills, extruders, kneaders, Ultraturrax, in-line dissolvers, static mixers, micromixers, gear rim dispersers, pressure relief nozzles and / or microfluidizers , At least the constituents (B) and (C) and optionally the catalyst (D) and at least one additive (E) are preferably mixed with an organic solution or melt of the binder (A). The resulting organic mixture is then dispersed in an aqueous medium containing water and at least one of the neutralizing agents described above.

The ETL according to the invention is applied in a customary and known manner by immersing an electrically conductive substrate in an electrodeposition bath according to the invention, switching the substrate as a cathode or anode, preferably as a cathode, depositing an ETL layer by direct current, the coated substrate is removed from the electrocoating bath and the deposited ETL layer thermally in the usual and known manner is hardened (baked). The resulting electrocoat can then be overcoated with a filler or a stone chip protection primer and a solid-color topcoat or alternatively with a basecoat and a clearcoat using the wet-on-wet method. The filler layer or layer from the stone chip protection primer and the solid-color lacquer layer are preferably each baked on individually. The basecoat and the clearcoat are preferably baked together. The result is multi-layer coatings with excellent application properties

The multi-layer coatings are preferably produced by wet-on-wet methods, in which the deposited ETL layer is not or only partially thermally cured and immediately covered with the other coating materials, in particular aqueous coating materials, after which it is coated with at least one of the layers Coating materials (ETL layer + filler layer; ETL layer + filler layer + solid color lacquer layer; ETL layer + filler layer + basecoat layer or ETL layer + filler layer + basecoat layer + clear lacquer layer) are baked together. This also results in multi-layer coatings with excellent application properties, the production processes being particularly economical and energy-saving. It can be seen that the ETL layers according to the invention can be overlayed wet-on-wet in a particularly trouble-free manner.

In all cases, electro-dip coatings according to the invention are obtained which offer excellent corrosion protection and edge protection. Examples and comparative tests

Production Example 1

The production of a blocked polyisocyanate (B)

810 parts by weight of isomers and higher functional oligomers based on 4,4'-diphenylmethane diisocyanate with an isocyanate equivalent weight of 135 g / equ (Basonat® A 270 from BASF Aktiengesellschaft) were placed in a reactor equipped with a reflux condenser, internal thermometer and nitrogen inlet tube under a nitrogen atmosphere. 0.6 part by weight of dibutyltin dilaurate was added. 988 parts by weight of butyl diglycol were metered into the resulting mixture at a rate such that the temperature of the reaction mixture did not exceed 60.degree. The temperature of the reaction mixture was then kept at 100 ° C. for two hours. According to this, free isocyanate groups can no longer be detected. The reaction mixture was diluted with 87 parts by weight of phenoxypropanol and 87 parts by weight of butoxypropanol and then cooled to 70 ° C. The solids content of the solution was 90% by weight.

example 1

Production of a KTL according to the invention

541 parts by weight of a commercial epoxy resin based on bisphenol A with an epoxy equivalent weight of 188 g / equ, 42 parts by weight of phenol, 123 parts by weight of bisphenol A and 21 parts by weight of butoxypropanol were placed in a reactor equipped with a reflux condenser, internal thermometer and nitrogen inlet tube and heated under nitrogen to 130 ° C with stirring. 0.7 part by weight of triphenylphosphine was added with stirring, whereupon an exothermic reaction started and the temperature of the reaction mixture rose to 155.degree. The temperature of the reaction mixture was allowed to drop to 130 ° C and then the epoxy equivalent weight was determined. It was 525 g / equ and thus corresponded to the setpoint of 520 to 530 g / equ. The reaction mixture was then mixed with 73 parts by weight of a polypropylene glycol (Pluriol® P 600 from BASF Aktiengesellschaft) and cooled to 95 ° C. At this temperature, 52 parts by weight of diethanolamine were added, whereupon an exothermic reaction occurred and the temperature of the reaction mixture rose to 115 ° C. After 40 minutes, 25.3 parts by weight of N, N-dimethylaminopropylamine were added at this temperature, whereupon the temperature of the reaction mixture rose to 140.degree. The reaction mixture was then stirred at 130 ° C. until the viscosity remained constant after two hours.

In the resulting reaction mixture were 408 parts by weight of the 70 ° C warm solution of the blocked polyisocyanate (B) of Preparation 1 and 41.7 parts by weight of a melamine-formaldehyde resin

on average 2.5 triazine rings in the molecule and,

- Based on the hydrogen atoms originally present in the primary amino groups of melamine, 30 mol% hydroxymethylene groups, 68.5 mol% methoxymethylene groups and 1.5 mol% imino groups

contained (Cymel ® 370 from CYTEC) stirred in quickly. The resulting mixture became intense at 115 ° C for 30 minutes touched. Then 29 parts by weight of bismuth ethylhexanoate were added, after which the mixture was immediately dispersed in an aqueous medium composed of 969 parts by weight of water, 18.7 parts by weight of formic acid and 108 parts by weight of a 5% aqueous solution of polyvinyl alcohol. After adding 543 parts by weight of water, a stable dispersion resulted with the following key figures:

Solids: 43.5% by weight

pH: 5.3

average particle size: 110 nm (determined using photon correlation spectroscopy)

Comparative experiment V 1

The production of a KTL not according to the invention

Example 1 was repeated, except that no Cymel ® 370 was added. A stable dispersion with the following key figures was obtained:

Solid: 43% by weight

- pH value: 5.6% by weight

average particle size: 110 nm (determined by photon correlation spectroscopy).

Comparative experiment V2 The production of a KTL not according to the invention

Example 1 was repeated, except that hexamethoxymelamine (Cymel® 300) was used instead of Cymel® 370. A stable dispersion with the following key figures was obtained:

Solids: 43.5% by weight

pH: 5.6

average particle size: 110 nm (determined using photon correlation spectroscopy).

Example 2 and comparative tests V 3 and V 4

The manufacture of electro-dip coatings

For the production of the electrodeposition coating, 2,310 parts by weight of the KTL of Example 1 (= Example 2), the comparative test V 1 (= comparative test V 3) and the comparative test V 2 (= comparative test V 4) were each diluted with 2,690 parts by weight of deionized water. The resulting electrocoat baths were aged with stirring for two days at room temperature. The electrodeposition coating layers were deposited for two minutes on cathodically connected, zinc-phosphated steel test panels which had not been rinsed with chromium (VI). The coated steel test panels were removed from the electrocoating baths. The electrocoat layers thereon were rinsed with deionized water. In each case a part of the steel test panels of Example 2 and the comparative tests V 3 and V 4 were coated wet-on-wet with a commercially available water filler from BASF Coatings AG, after which the electrocoating and the layers from the water filler were carried out together for 30 minutes at 180 ° C branded object temperature. No defects in the layers had occurred in the coated steel test panels of Example 2, whereas in the coated steel test panels of the comparative tests V 3 and V 4, the layers had been disrupted by strike-in.

The other part of the steel test panels of Example 2 and the comparative tests V 3 and V 4 was then baked at an object temperature of 180 ° C. for 20 minutes. The resulting electrodeposition coatings had a layer thickness of 20 μm. The coated steel test panels were each scored and subjected to a climate change test (VDA-KWT). The infiltration of the scratch and the degree of rust on the edges were assessed. The results can be found in the table. They underline that the electrocoat materials according to the invention were also superior to those not according to the invention in corrosion protection and edge protection.

Table: Results of the climate change test

Example 2

V 3 V 4

Infiltration (10 cycles) (mm) 1, 5 3.0 3.0 Edges are snapping

(6 cycles) Note ^a)

a) 0 = best value; 5 = worst value

Claims

claims

1. Containing electrodeposition paints (ETL) free from insoluble solids

(A) at least one binder with (potentially) cationic or anionic groups and reactive functional groups which can undergo thermal crosslinking reactions with the complementary reactive functional groups present in components (B) and (C),

(B) at least one blocked polyisocyanate and

(C) containing at least one melamine-formaldehyde resin

(c 1) on average at least 1 to 4 triazine rings in the molecule and,

(c 2) based on the hydrogen atoms of the amino groups which were originally available for the reaction with formaldehyde,

(c 21) 10 to 40 mol% of hydroxymethylene groups,

(c 22) 50 to 85 mol% of methoxymethylene or

Methoxymethylene and

Butoxymethylene groups and

(c 23) 0 to 15 mol% of imino groups (> NH).

2. ETL according to claim 1, characterized in that the melamine-formaldehyde resin contains on average 2 to 3 triazine rings in the molecule.

3. ETL according to claim 1 or 2, characterized in that the melamine-formaldehyde resin, based on the hydrogen atoms of the amino groups which were originally available for the reaction with formaldehyde, contains 25 to 35 mol% of hydroxymethylene groups.

4. ETL according to one of claims 1 to 3, characterized in that the melamine-formaldehyde resin, based on the hydrogen atoms of the amino groups which were originally available for the reaction with formaldehyde, contains 60 to 70 mol% of methoxymethylene groups.

5. ETL according to one of claims 1 to 4, characterized in that the melamine-formaldehyde resin, based on the hydrogen atoms of the amino groups which were originally available for the reaction with formaldehyde, contains up to 3 mol% of imino groups.

6. ETL according to one of claims 1 to 5, characterized in that the weight ratio of component (B) to component (C) = 1.1: 1 to 20: 1.

7. ETL according to claim 6, characterized in that (B): (C) = 1, 5: 1 to 15: 1.

8. ETL according to claim 7, characterized in that (B): (C) = 2: 1 to 10: 1.

9. ETL according to one of claims 1 to 8, characterized in that they contain the components (B) and (C) in an amount of 20 to 40% by weight, based on the solids of each ETL.

10. ETL according to claim 9, characterized in that they contain the components (B) and (C) in an amount of, based on the solids of each ETL, 25 to 35 wt .-%.

11. ETL according to one of claims 1 to 10, characterized in that the binders (A) contain (potentially) cationic groups.

12. ETL according to one of claims 1 to 11, characterized in that the binders (A) as reactive functional groups

Contain hydroxyl groups.

13. ETL according to one of claims 1 to 12, characterized in that they contain a catalyst (D) for thermal crosslinking.

14. ETL according to one of claims 1 to 13, characterized in that the catalyst (D) is bismuthaltig.

15. A method for producing the ETL according to one of claims 1 to 14, characterized in that

(1) at least components (B) and (C) are mixed with an organic solution or the melt of the binder (A), whereby the organic mixture (1) results, and (2) the organic mixture (1) is dispersed in an aqueous medium containing water and at least one neutralizing agent.

16. The method according to claim 15, characterized in that the catalyst (D) is mixed with an organic solution or the melt of the binder (A).

17. Use of the ETL according to one of claims 1 to 14 or those produced by the method according to claim 15 or 16

ETL for the production of multi-layer coatings using the wet-on-wet process.