EP3083733A1

EP3083733A1 - Aqueous coating composition and production of multilayer coatings with use of the coating composition

Info

Publication number: EP3083733A1
Application number: EP14809870.0A
Authority: EP
Inventors: Bernhard Steinmetz; Nadia Luhmann; Peggy JANKOWSKI; Michael MATURA; Hardy Reuter; Peter Hoffmann
Original assignee: BASF Coatings GmbH
Current assignee: BASF Coatings GmbH
Priority date: 2013-12-18
Filing date: 2014-12-11
Publication date: 2016-10-26
Also published as: US20160319151A1; CN105940031B; CN105940031A; US9976052B2; EP2886570A1; JP2017507201A; JP6449302B2; WO2015091194A1

Abstract

The present invention relates to an aqueous coating composition containing at least one aqueous dispersion containing at least one copolymer (MP), where the copolymer (MP) can be produced by (i) providing an aqueous dispersion of at least one polyurethane, and then (ii) polymerizing a mixture of olefinically unsaturated monomers in the presence of the polyurethane from (i), where (a) a water-soluble initiator is used, (b) the manner of metering of the olefinically unsaturated monomers into the system is such as to avoid exceeding a concentration, in relation to the total quantity of olefinically unsaturated monomers used for the polymerization reaction, of 6.0 % by weight in the reaction solution during the entire reaction time, and (c) the mixture of the olefinically unsaturated monomers contains at least one olefinically polyunsatured monomer, at least one linear hydroxy-functional reaction product (R) with acid number smaller than 20 mg KOH/g, produced with use of at least one compound (v) containing two functional groups (v.a) and also, arranged between the functional groups, an aliphatic or araliphatic hydrocarbon moiety (v.b) having from 12 to 70 carbon atoms, and also at least one polyurethane resin (X) produced with use of at least one compound (x.1) containing at least one carboxylic acid group and at least one group reactive towards isocyanate groups. The present invention also relates to a process for producing a multilayer coating with use of the coating composition, and to the resultant multilayer coating.

Description

Aqueous coating composition and production of multicoat paint systems using the coating composition

The present invention relates to an aqueous coating composition comprising a copolymer, a hydroxy-functional reaction product and a polyurethane resin. The present invention also relates to a process for the production of multicoat paint systems using the aqueous coating composition and to the multicoat paint systems that can be prepared by means of said process. In addition, the present invention relates to the use of the aqueous coating composition for improving the stability of multicoat paint systems against optical defects, in particular pinholes.

State of the art

A variety of methods for the production of color and / or effect multi-layer coatings are known. From the prior art (see for example the German patent application DE 199 48 004 A1, page 17, line 37, to page 19, line 22, or the German patent DE 100 43 405 C1, column 3, paragraph [0018], and column 8, paragraph [0052] to column 9, paragraph [0057], in connection with column 6, paragraph [0039] to column 8, paragraph [0050]), for example, the following method is known, in which

(1) a pigmented aqueous basecoat is applied to a substrate,

(2) a polymer film is formed from the varnish applied in step (1),

(3) a clearcoat is applied to the basecoat so obtained and then

(4) the basecoat layer is cured together with the clearcoat layer.

For example, this process is widely used both for automotive OEM painting and the painting of metal and plastic attachments. By means of the processes described, it is possible to prepare different multicoat paint systems which, although they have different application-technological properties, are still worthy of improvement in some aspects. A recurrent problem of multicoat paint systems in the automotive industry lies in the fact that some of the optical quality, which is very important for automobiles and is subject to high quality control, is not reached. In addition to properties such as gloss or sharpness of image (DOI), the optical quality of a multicoat system depends in particular on the number of locally limited, optical defects. It is precisely such locally limited, optically discreet detectable defects are very noticeable within an otherwise homogeneous paint surface and set the optical quality significantly. In particular, there are needlesticks. As is known, these are produced, in particular, in the production of multicoat paint systems by undesired air, solvent and / or moisture inclusions during the application processes of coating compositions. These inclusions may be in the form of bubbles below the surface of the overall finish and may break during the subsequent cure. The resulting holes are also called pinholes. The higher the layer thickness of the coating composition is chosen, the greater the amount of air, organic solvents and / or water that must escape from the applied layers. As a result, the tendency to form pinholes increases. The layer thickness at which pinholes occur (pinprick limit) can therefore serve as proof of the stability against pinholes, just as the number of pinholes at a given layer thickness.

The influencing of certain application-technological properties of multicoat paint systems can be carried out, for example, by the specific coordination and combination of special components, such as binders or additives, in the coating compositions used for the production of the coatings.

Task and technical solution

The object of the present invention was therefore to improve the stability of multicoat paint systems against optical defects, in particular pinholes. In this way, it should be possible in particular to meet the ever-increasing demands of automobile manufacturers on the To meet application technological properties of multi-layer coatings.

It was found that the stated objects could be achieved by an aqueous coating composition comprising at least one aqueous dispersion comprising at least one copolymer (MP), wherein the copolymer (MP) can be prepared by

(I) presentation of an aqueous dispersion of at least one polyurethane, and then

(ii) polymerizing a mixture of olefinically unsaturated monomers in the presence of the polyurethane of (i),

in which

(a) a water-soluble initiator is used,

(b) the addition of the olefinically unsaturated monomers takes place in such a way that in the reaction solution a concentration of 6.0% by weight, based on the total amount of olefinically unsaturated monomers used for the polymerization, is not exceeded during the entire reaction time, and

(C) the mixture of olefinically unsaturated monomers contains at least one polyunsaturated monomer, at least one linear hydroxy-functional reaction product (R) having an acid number less than 20 mg KOH / g, in its preparation at least one compound (v) containing two functional groups (especially ) and an aliphatic or araliphatic hydrocarbon radical (vb) having 12 to 70 carbon atoms arranged between the functional groups, and at least one polyurethane resin (X), in the preparation of which at least one compound (x.1) containing at least one carboxylic acid group and at least one isocyanate-reactive group is used.

The novel aqueous coating composition is also referred to below as a coating composition according to the invention. Preferred embodiments of the coating composition of the invention will become apparent from the following description and the appended claims.

Likewise provided by the present invention is a process for the production of multicoat paint systems using the aqueous coating composition and the multicoat paint systems which can be prepared by means of said process. In addition, the present invention relates to the use of the aqueous coating composition for improving the stability of multicoat paint systems against optical defects, in particular pinholes.

It has been shown that the stability of these coatings against optical defects can be markedly improved by the use of the coating composition according to the invention for the production of coatings, in particular multi-layer coatings. The use of the aqueous coating composition as basecoat achieves in particular outstanding pinhole resistance in the resulting multicoat paint system.

Detailed description

The coating composition of the invention

The coating composition according to the invention contains a special aqueous dispersion comprising at least one special copolymer (MP), preferably exactly one copolymer (MP).

A copolymer according to the present invention refers to polymers which are composed of different types of polymers, for example a polyurethane and a (meth) acrylate polymer. It is expressly both Including polymers which are covalently bonded to each other, as well as those in which the various polymers are bonded to each other by adhesion. Combinations of both types of binding are also covered by this definition. The term "(meth) acrylate" covers acrylates, methacrylates and mixtures thereof The terms polymer and polymer are identical in content and therefore interchangeable.

The copolymer (MP) can be prepared by

in which

a. a water-soluble initiator is used, b. the addition of the olefinically unsaturated monomers is such that in the reaction solution, a concentration of 6.0 wt .-%, based on the total amount of olefinically unsaturated monomers used for the polymerization, is not exceeded during the entire reaction time, and

c. the mixture of olefinically unsaturated monomers contains at least one polyunsaturated monomer.

In the first production step, an aqueous dispersion of a polyurethane resin is introduced.

Suitable saturated or unsaturated polyurethane resins are described, for example, in

German Patent Application DE 199 48 004 A1, page 4, line 19 to page 11 line 29 (polyurethane prepolymer B1)

European Patent Application EP 0 228 003 A1, page 3, line 24 to page 5, line 40, European Patent Application EP 0 634 431 A1, page 3, line 38 to page 8, line 9, or

International Patent Application WO 92/15405, page 2, line 35 to page 10, line 32.

For the preparation of the polyurethane resin on the one hand preferably known to those skilled aliphatic, cycloaliphatic, aliphatic-cycloaliphatic, aromatic, aliphatic-aromatic and / or cycloaliphatic-aromatic polyisocyanates are used. Particularly preferred are aliphatic and aliphatic-cycloaliphatic polyurethane resins.

As the alcohol component for the preparation of the polyurethane resins, it is preferred to use the saturated and unsaturated polyols known to those skilled in the art and also, if appropriate, in minor amounts also monoalcohols. In particular, diols and optionally minor amounts of triols are used to introduce branching. Examples of suitable polyols are saturated or olefinically unsaturated polyester polyols and / or polyether polyols. In particular, as polyols polyester polyols, in particular those having a number average molecular weight of 400 to 5000 g / mol used. The number average molecular weight is determined in the context of the present invention, unless specifically stated otherwise, by means of steam pressure osmosis. Was measured by means of a vapor pressure osmometer (Model 10.00, Fa Knauer) in concentration series of the component to be tested in toluene at 50 ° C with benzophenone as a calibration substance for determining the experimental calibration constant of the measuring instrument used (after E. Schröder, G. Müller, K.- F. Arndt, "Leitfaden der Polymercharakterisierung", Akademie-Verlag, Berlin, pp. 47-54, 1982, in which benzil was used as calibration substance).

Preferably, the polyurethane introduced in aqueous dispersion is a hydrophilically stabilized polyurethane. For hydrophilic stabilization or for increasing the dispersibility in an aqueous medium, the polyurethane resin may contain certain ionic groups and / or groups that can be converted into ionic groups (potentially ionic groups). Such polyurethane resins are considered ionic in the context of the present invention hydrophilic stabilized polyurethane resins called. Also included may be nonionic hydrophilic modifying groups. However, the ionically hydrophilically stabilized polyurethanes are preferred. Specifically, the modifying groups are either um

functional groups which can be converted into cations by neutralizing agents and / or quaternizing agents and / or cationic groups (cationic modification)

or

functional groups which can be converted into anions by neutralizing agents and / or anionic groups (anionic modification) or

nonionic hydrophilic groups (nonionic modification)

or

- Combinations of the aforementioned groups.

As those skilled in the art know, the functional groups for cationic modification are, for example, primary, secondary and / or tertiary amino groups, secondary sulfide groups and / or tertiary phosphine groups, especially tertiary amino groups and secondary sulfide groups (functional groups neutralized by neutralizing agents and / or Quaternizing agents can be converted into cationic groups). Also to be mentioned are the cationic groups prepared from the abovementioned functional groups using neutralizing agents and / or quaternizing agents known to those skilled in the art, such as primary, secondary, tertiary and / or quaternary ammonium groups, tertiary sulfonium groups and / or quaternary phosphonium groups, in particular quaternary ammonium groups and tertiary sulfonium groups ,

As is known, the functional groups for anionic modification are, for example, carboxylic acid, sulfonic acid and / or phosphonic acid groups, in particular carboxylic acid groups (functional groups which can be converted into anionic groups by neutralizing agents) and from the abovementioned functional groups using the One skilled in the art neutralizing agent prepared anionic groups such as carboxylate, sulfonate and / or phosphonate.

The functional groups for nonionic hydrophilic modification are preferably poly (oxyalkylene) groups, in particular poly (oxyethylene) groups.

The ionic hydrophilic modifications may be introduced into the polyurethane resin by monomers containing the ionic or potentially ionic groups. The nonionic modifications are introduced, for example, by the incorporation of poly (ethylene oxide) polymers as lateral or terminal groups of the polyurethane molecules. The hydrophilic modifications are introduced, for example, via compounds which contain at least one isocyanate-reactive group, preferably at least one hydroxy group. To introduce the ionic modification, it is possible to use monomers which contain at least one hydroxy group in addition to the modifying groups. To introduce the nonionic modifications, preference is given to using the polyether diols known to the person skilled in the art and / or alkoxy poly (oxyalkylene) alcohols.

Preferably, at least one organic solvent is added to the initially charged polyurethane dispersion, the organic solvent preferably being miscible in any proportion with water and in any proportion with the mixture of olefinically unsaturated monomers. Suitable organic solvents are N-methylpyrrolidone, N-ethylpyrrolidone and ether alcohols such as, in particular, methoxypropanol, it being noted that it is already possible, for ecological reasons, to dispense with pyrrolidone-based solvents. However, the amount of organic solvent is chosen so that the aqueous character of the dispersion is maintained.

In the second production step, a polymerization of a mixture of olefinically unsaturated monomers in the presence of the polyurethane is carried out by the methods of so-called free-radical emulsion polymerizations in the presence of at least one polymerization initiator. The polymerization initiator used must be a water-soluble initiator. Examples of suitable initiators are potassium, sodium or ammonium peroxodisulfate, and hydrogen peroxide, tert-butyl hydroperoxide, 2,2'-azobis (2-amidoisopropane) dihydrochloride, 2,2'-azobis (N, N'-dimethyleneisobutyramidine) dihydrochloride or 2,2'-azo-bis (4-cyano) pentanoic acid). The initiators are used either alone or in mixture, for example mixtures of hydrogen peroxide and sodium persulfate.

The known redox initiator systems can also be used as polymerization initiators. Such redox initiator systems contain at least one peroxide-containing compound in combination with a redox coinitiator, for example reducing sulfur compounds, for example bisulfites, sulfites, thiosulfates, dithionites or tetrathionates of alkali metals and ammonium compounds, sodium hydroxymethanesulfinate dihydrate and / or thiourea. Thus, it is possible to use combinations of peroxodisulfates with alkali metal or ammonium hydrogen sulfites, for example ammonium peroxydisulfate and ammonium bisulfite. The weight ratio of peroxide-containing compounds to the redox coinitiators is preferably 50: 1 to 0.05: 1. In combination with the initiators or the redox initiator systems it is additionally possible to use transition metal catalysts, for example iron, nickel, cobalt, manganese, copper, vanadium or chromium salts, such as iron (II) sulfate, cobalt (II) chloride. Nickel-ll-sulfate, copper-l-chloride, manganese-ll-acetate, vanadium-l-acetate, manganese-ll-chloride. Based on the monomers, these transition metal salts are usually used in amounts of from 0.1 to 1000 ppm. So you can use combinations of hydrogen peroxide with iron-Il salts, such as 0.5 to 30% hydrogen peroxide and 0.1 to 500 ppm Mohr's salt.

The initiators are preferably used in an amount of from 0.05 to 20% by weight, preferably from 0.05 to 10, particularly preferably from 0.1 to 5% by weight, based on the total weight of the olefinically unsaturated monomers used for the polymerization. The terms total and total weight are synonymous. The use of the water-soluble initiator implies that olefinically unsaturated monomers added to the initially charged aqueous dispersion can immediately react to form oligomers. These oligomers have less tendency to penetrate into the polyurethane particles of the initially introduced dispersion than the smaller monomers.

The polymerization is expediently carried out, for example, at a temperature of greater than 0 to 160.degree. C., preferably 60 to 95.degree.

In this case, preference is given to operating under exclusion of oxygen, preferably in a stream of nitrogen. In general, the polymerization is carried out at atmospheric pressure, but the use of lower pressures or higher pressures is possible, especially when polymerization temperatures are used which are above the boiling point of the monomers and / or the organic solvent.

The preparation of the copolymers (MP) to be used according to the invention is carried out by free-radical aqueous emulsion polymerization, wherein surfactants or protective colloids can be added to the reaction medium. A list of suitable emulsifiers and protective colloids can be found for example in Houben Weyl, Methods of Organic Chemistry, Volume XIV / 1 Macromolecular substances, Georg Thieme Verlag, Stuttgart 1961, S 41 1 ff.

Important for the preparation of the aqueous dispersions to be used according to the invention comprising the copolymer (MP) is the control of the conditions of the polymerization reaction of the mixture of olefinically unsaturated monomers in the presence of the polyurethane. This is done so that it is a so-called "starving polymerization" (also known as "starve feed", "starve fed" or "starved feed" polymerization).

As starving polymerization in the context of the present invention, an emulsion polymerization is considered in which the content of residual monomers in the reaction solution is minimized during the reaction time, that is, the metered addition of the olefinically unsaturated monomers is such that in the Reaction solution has a concentration of 6.0 wt .-%, preferably 5.0 wt .-%, particularly preferably 4.0 wt .-%, particularly advantageously 3.5 wt .-%, each based on the total amount of used for the polymerization olefinically unsaturated monomers, is not exceeded during the entire reaction time. Of these, even more preferred are concentration ranges of the olefinically unsaturated monomers of 0.01 to 6.0 wt .-%, preferably 0.02 to 5.0 wt .-%, particularly preferably 0.03 to 4.0 wt .-%, in particular 0.05 to 3.5% by weight, in each case based on the total amount of olefinically unsaturated monomers used for the polymerization. For example, the highest proportion to be detected during the reaction (or the concentration) at 0.5% by weight, 1, 0 wt .-%, 1, 5 wt .-%, 2.0 wt .-%, 2, 5 wt .-% or 3.0 wt .-% are, while all other detected values are then below the values given here. The term concentration in this context is therefore obviously synonymous with the term proportion.

The concentration of monomers in the reaction solution, hereinafter referred to as free monomers, can be controlled in various ways.

One way to keep the concentration of free monomers low is to choose the dosing rate of the mixture of olefinically unsaturated monomers very low. If the addition rate is so low that all monomers can react as quickly as they are in the reaction solution, it can be ensured that the concentration of the free monomers is minimized.

In addition to the metering rate, it is important that always sufficient radicals are present in the reaction solution, so that the metered monomers can be brought as soon as possible to the reaction. For this purpose, the reaction conditions are preferably to be selected so that the initiator feed is started even before the beginning of the metering of the olefinically unsaturated monomers. Preferably, the dosage is started at least 5 minutes before, more preferably at least 10 minutes before. Preference is given to at least 10% by weight of the initiator, particularly preferably at least 20% by weight, very particularly preferably at least 30% by weight, of the initiator, based in each case on the Total amount of initiator added before starting the dosage of olefinically unsaturated monomers.

The amount of initiator is an important factor for the sufficient presence of radicals in the reaction solution. The amount of initiator should be chosen so that sufficient free radicals are available at all times so that the added monomers can react. If the amount of initiator is increased, even larger amounts of monomers can be reacted at the same time.

Another factor that can determine the reaction rate is the structure of the monomers, that is, in particular their structural properties and the resulting reactivity.

The control of the concentration of the free monomers can thus be controlled by the interaction of amount of initiator, rate of initiator addition, rate of monomer addition and by the choice of monomers. Both the slowing of the dosage, as well as the increase in the amount of initiator, as well as the early start with the addition of the initiator serve in particular the goal of keeping the concentration of the free monomers below the limits mentioned above.

The concentration of the monomers in the reaction solution can be determined by gas chromatography at any time during the reaction. Typical parameters for the gas chromatographic determination are the following: 50m silica capillary column with polyethylene glycol phase or 50m silica capillary column with polydimethylsiloxane phase, carrier gas helium, split injector 150 ° C, oven temperature 40 to 220 ° C, flame ionization detector, detector temperature 275 ° C, internal standard isobutyl acrylate. In the context of the present invention, the determination of the concentration of the monomers is preferably carried out by gas chromatography, in particular while maintaining the abovementioned parameters.

Should a concentration of free monomers close to the limit value for the starving polymerization be determined in this analysis, for example due to a high proportion of olefinically unsaturated monomers have low reactivity, the above parameters can be used to control the reaction. In this case, for example, the metering rate of the monomers can be reduced and / or the amount of initiator can be increased.

Suitable olefinically unsaturated monomers may be mono- or poly-olefinically unsaturated. At least one monoolefinically unsaturated monomer and at least one polyunsaturated monomer are preferably present.

Examples of suitable monoolefinically unsaturated monomers include vinylic monoolefinically unsaturated monomers such as, in particular, (meth) acrylate-based monoolefinically unsaturated monomers and allyl compounds. Examples are also alpha-beta unsaturated carboxylic acids. In any case, but not necessarily exclusively, (meth) acrylate-based monoolefinically unsaturated monomers are preferably used.

The (meth) acrylate-based, mono-olefinically unsaturated monomers may be, for example, (meth) acrylic acid and esters, nitriles, or amides of (meth) acrylic acid.

Preferred are esters of (meth) acrylic acid, with a radical R, which is not olefinically unsaturated.

The radical R may be aliphatic or aromatic. The radical R is preferably aliphatic.

The radical R may be, for example, an alkyl radical or contain heteroatoms. Examples of radicals R which contain heteroatoms are ethers. To be favoured in any case, but not necessarily exclusively, monomers used in which the radical R is an alkyl radical.

In the event that R is an alkyl radical, it may be, for example, a linear, branched or cyclic alkyl radical. In all three cases, these may be unsubstituted or functional groups substituted alkyl radicals. The alkyl radical preferably has 1 to 20, particularly preferably 1 to 10, carbon atoms.

Particularly preferred monounsaturated esters of (meth) acrylic acid having an unsubstituted alkyl group are methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth acrylate, tert-butyl (meth) acrylate, amyl (meth) acrylate, hexyl (meth) acrylate, ethylhexyl (meth) acrylate, 3,3,5-trimethylhexyl (meth) acrylate, stearyl (meth) acrylate, Lauryl (meth) acrylate, cycloalkyl (meth) acrylates such as cyclopentyl (meth) acrylate, isobornyl (meth) acrylate and cyclohexyl (meth) acrylate wherein n- and tert-butyl (meth) acrylate and methyl methacrylate are very particularly preferred.

Suitable monounsaturated esters of (meth) acrylic acid with a substituted alkyl radical may preferably be substituted by one or more hydroxyl groups.

Particularly preferred monounsaturated esters of (meth) acrylic acid with an alkyl radical substituted by one or more hydroxyl groups are 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate.

Possible further vinylic monounsaturated monomers are monomers having a radical R 'on the vinyl group which is not olefinically unsaturated.

The radical R 'may be aliphatic or aromatic, with aromatic radicals being preferred. The radical R 'may be a hydrocarbon radical or contain heteroatoms. Examples of radicals R 'which contain heteroatoms are ethers, esters, amides, nitriles and heterocycles. The radical R 'is preferably a hydrocarbon radical. In the event that R 'is a hydrocarbon radical, this may be substituted or unsubstituted with heteroatoms, unsubstituted radicals being preferred. The radical R 'is preferably an aromatic hydrocarbon radical.

Particularly preferred further vinylic olefinically unsaturated monomers are vinylaromatic hydrocarbons, in particular vinyltoluene, alpha-methylstyrene and in particular styrene.

Other preferred monomers containing heteroatoms are olefinically unsaturated monomers such as acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, N-dimethylacrylamide, vinyl acetate, vinyl propionate, vinyl chloride, N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylformamide, N-vinylimidazole and N-vinyl -2-methyl-imidazoline.

Examples of suitable poly olefinically unsaturated monomers include esters of (meth) acrylic acid with an olefinically unsaturated radical R "and allyl ethers of polyhydric alcohols.

respectively.

The radical R "may be, for example, an allyl radical or a (meth) acrylic ester radical.

Preferred poly olefinically unsaturated monomers are ethylene glycol di (meth) acrylate, 1,2-propylene glycol di (meth) acrylate, 2,2-propylene glycol di (meth) acrylate, butanediol-1,4-di (meth) acrylate, neopentyl glycol di (meth) acrylate, 3-methylpentanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (neth) acrylate, hexanediol di (meth) acrylate and allyl (meth) acrylate.

Preferred multiply olefinically unsaturated compounds are also acrylic acid and methacrylic acid esters of alcohols having more than two OH groups, for example trimethylolpropane tri (meth) acrylate or glycerol tri (meth) acrylate, but also trimethylolpropane di (meth) acrylate monoallyl ether, trimethylolpropane (meth) acrylate diallyl ether, pentaerythritol tri (meth) acrylate monoallyl ether, pentaerythritol di (meth) acrylate diallyl ether, pentaerythritol (meth) acrylate triallyl ether, triallyl sucrose, and pentaallylsucrose.

Allyl methacrylate is particularly preferably used as a multiply olefinically unsaturated monomer.

The mixture of olefinically unsaturated monomers contains at least one poly olefinically unsaturated monomer. Preferably, the mixture of olefinically unsaturated monomers also contains one or more monounsaturated esters of (meth) acrylic acid with an unsubstituted alkyl radical.

The mixture of the olefinically unsaturated monomers preferably contains from 0.1 to 6.0 mol%, particularly preferably from 0.1 to 2.0 mol%, very particularly preferably from 0.1 to 1.0 mol%, of multiply olefinically unsaturated monomers. Preferably, the remainder of the olefinically unsaturated monomers is monounsaturated.

The mixture of the olefinically unsaturated monomers preferably contains 0.1 to 6.0 mol%, particularly preferably 0.1 to 2.0 mol%, very particularly preferably 0.1 to 2.0 mol% allyl methacrylate. Apart from allyl methacrylate, no further poly olefinically unsaturated monomers are particularly preferably contained in the mixture.

The mixture of olefinically unsaturated monomers preferably contains less than 10.0% by weight, particularly preferably less than 5.0% by weight, of vinylaromatic hydrocarbons, based on the total amount of olefinically unsaturated monomers used in the polymerization. Very particular preference is given to vinylaromatic hydrocarbons in the mixture of olefinic contain unsaturated monomers. It is particularly preferred if less than 10.0% by weight, particularly preferably less than 5.0% by weight, based on the total amount of olefinically unsaturated monomers used in the polymerization, of olefinically unsaturated monomers having aromatic groups are used , In particular, no olefinically unsaturated monomers having aromatic groups are included in the mixture of olefinically unsaturated monomers.

It follows that the vinylaromatic hydrocarbons specified above as preferred, in particular vinyltoluene, alpha-methylstyrene and styrene, are of course preferred only within the group of monomers containing aromatic groups. Nevertheless, for the purposes of the invention, these monomers are preferably not used. If, in individual cases, the use of such monomers is still feasible, preference is given to using the monomers which are identified as being preferred and containing aromatic groups.

In a preferred embodiment, the mixture of olefinically unsaturated monomers comprises:

98.0 to 99.5% by weight of one or more monounsaturated esters of (meth) acrylic acid with unsubstituted alkyl radicals, the alkyl radicals preferably having 1 to 10 carbon atoms, and

0.5 to 2.0% by weight of one or more polyunsaturated esters of (meth) acrylic acid,

in each case based on the total amount of olefinically unsaturated monomers used in the polymerization.

Preferably, at least one solvent is added to the mixture of olefinically unsaturated monomers, wherein the solvent is preferably miscible in any proportion with water and in any proportion with the mixture of olefinically unsaturated monomers. Suitable organic solvents are N-methylpyrrolidone, N-ethylpyrrolidone and ether alcohols such as in particular methoxypropanol, wherein it should be noted that even for ecological reasons, the waiver of pyrrolidone-based solvents can offer. The amount of organic solvent but is chosen so that the aqueous character of the dispersion ultimately obtained is maintained.

As a result of the described production process, the copolymers in the aqueous dispersion according to the invention have, in particular, a core-shell structure which can be achieved by the stated production process. The core-shell structure is characterized by a core comprising at least one polyurethane, and a shell containing at least polymer which has been obtained by polymerization of olefinically unsaturated monomers.

The described core-shell construction is achieved by the special reaction conditions of the starving polymerization. There are never any major amounts of olefinically unsaturated monomers present in the presence of the polyurethane present during the entire reaction time, which could penetrate into the polyurethane particle. By always present during the monomer addition in the aqueous phase radicals, which provides the water-soluble initiator, oligomers are formed immediately upon addition, which can not penetrate into the polyurethane. These then polymerize on the surface of the polyurethane.

In a preferred embodiment, the weight ratio of core to shell is 80:20 to 20:80, more preferably 60:40 to 40:60. What is meant here is the ratio of the amounts of components used to prepare the core (step (i), polyurethane) and shell (step (ii), mixture of olefinically unsaturated monomers).

The copolymers (MP) in the aqueous dispersion preferably have a particle size (z-average) of 60 to 130, particularly preferably 70 to 15 nm, measured by photon correlation spectroscopy with a Malvern Nano S90 (Malvern Instruments) at 25 ± 1 ° C. The device, equipped with a 4mW He-Ne laser at a wavelength of 633nm, covers a size range from 1 to 3000 nm. The copolymers (MP) may preferably be crosslinked. The gel fraction of the aqueous dispersion according to the invention is preferably from 40 to 97% by weight, particularly preferably from 75 to 90% by weight, in each case based on the solids content of the dispersion.

The gel fraction can be determined gravimetrically by freeze-drying the dispersion, determining the total mass of the freeze-dried polymer (corresponding to the solid content of the dispersion as part of the determination of the gel content) and then the polymer in an excess of tetrahydrofuran (ratio Tetrahydrofuran to freeze-dried polymer = 300: 1) is extracted. The insoluble portion is separated and dried at 50 ° C for four hours in a convection oven. Subsequently, the dried, insoluble fraction is weighed and the quotient with the total mass of the freeze-dried polymer is formed. The value obtained corresponds to the gel content.

The weight average molecular weight of the copolymers (MP) is preferably 3 ^* 10 ⁷ g / mol to 8.5 ^* 10 ⁹ g / mol, wherein the weight average molecular weight can be determined with small angle laser light scattering.

The acid number of the copolymers (MP) is preferably 0 to 220 mg KOH / g of solid resin, preferably 0 to 40 mg KOH / g of solid resin, more preferably 0 to 25 mg KOH / g of solid resin. The OH number is preferably less than 70, preferably less than 20 mg KOH / g of solid resin. The terms solid resin and solid state with respect to a polymer or a dispersion of a polymer are meaningfully identical. It is therefore in particular the solid or solid content of a polymer dispersion as explained below.

The acid number can be determined, for example, based on DIN EN ISO 21 14 in a homogeneous solution of THF / water (9 parts by volume of THF and 1 part by volume of distilled water) with ethanolic potassium hydroxide solution.

The OH number can be modeled on R.-P. Krüger, R. Gnauck and R. Algeier, Plaste und Kautschuk, 20, 274 (1982), by means of acetic anhydride in the presence of 4-dimethylaminopyridine as catalyst in a tetrahydrofuran (THF) / Dimethylfornnannid (DMF) solution can be determined at room temperature, the remaining excess of acetic anhydride is completely hydrolyzed after acetylation and the acetic acid is potentiometrically titrated back with alcoholic potassium hydroxide solution.

The aqueous dispersions of the at least one copolymer (MP) preferably have a solids content of from 15 to 45% by weight, particularly preferably from 25 to 35% by weight. Such solid contents can be easily adjusted by the use of appropriate amounts of organic solvents and in particular water in the preparation of the copolymers and / or by appropriate dilution after preparation.

The proportion of the copolymers (MP) is preferably in the range of 0.5 to 15 wt .-%, preferably 0.75 to 12.5 wt .-%, particularly preferably 1, 0 to 10 wt .-%, in particular 1, 5 to 7.5 wt .-%, each based on the total weight of the coating composition of the invention.

The coating composition according to the invention also contains at least one specific reaction product (R), preferably exactly one reaction product (R).

The reaction products are linear. In principle, linear reaction products can be obtained by the reaction of difunctional reactants, in which case the linking of the reactants via reaction of the functional groups results in a linear, ie chain-like structure. For example, in the case where the reaction product is a polymer, the backbone has a linear character. If the reaction product is a polyester, for example, diols and dicarboxylic acids can be used as reactants, in which case the sequence of ester bonds in the reaction product has a linear character. Preferably, therefore, mainly difunctional reactants are used in the preparation of the reaction product (R). Other reactants such as in particular monofunctional compounds are therefore preferably not used or only in minor amounts. In particular, at least 80 mol%, preferably at least 90 mol%, very particularly preferably exclusively difunctional reactants are used. If other reactants are used, these are preferably selected exclusively from the group of monofunctional reactants. However, it is preferred that only difunctional reactants are used.

Suitable functional groups of the reactants are the functional groups known to the person skilled in the art. Also, the combinations of reactants with appropriate functional groups that can be linked together and thus can serve for the preparation of the reaction product are known in principle. The same applies to the reaction conditions necessary for linking. Preferred functional groups of the reactants are hydroxyl, carboxyl, imino, carbamate, allophanate, thio, anhydride, epoxy, isocyanate, methylol, methylol ether, siloxane, and / or amino groups, more preferably hydroxyl and carboxyl groups. Preferred combinations of functional groups which can be linked together are hydroxyl and carboxyl groups, isocyanate and hydroxyl groups, isocyanate and amino groups, epoxy and carboxyl groups and / or epoxy and amino groups, care being taken in the choice of functional groups in that the hydroxy functionality and acid number of the reaction product described below are obtained. The linkage then forms the linking sites known to the person skilled in the art, for example ester groups, urethane groups and / or urea groups. Very particularly preferred is a combination of hydroxyl and carboxyl groups. In this embodiment, therefore, at least one reactant has hydroxyl groups and at least one further reactant has carboxyl groups. Preferably, a combination of dihydroxy-functional and dicarboxy-functional reactants is used. By known reaction guide formed in the reaction of these reactants reaction products containing ester bonds.

The reaction product is hydroxy-functional. It is preferred that the reactants are reacted so that resulting linear molecules have two terminal hydroxyl groups. This means that one hydroxyl group is present at each end of these molecules. The reaction product has an acid number of less than 20, preferably less than 15, more preferably less than 10 and most preferably less than 5 mg KOH / g. It therefore preferably has only a very small amount of carboxylic acid groups. The acid number is determined in the context of the present invention, unless explicitly stated otherwise, according to DIN 53402. It therefore refers to the reaction product itself, that is, to the solid (for determination of solids see below).

If reference is made in the context of the present invention to an official standard without reference to the official period of validity, this naturally includes the version of the standard applicable at the filing date or, if no valid version at that time, the last valid version.

The described hydroxyl functionality can be obtained as well as the low acid number, for example in a conventional manner by using appropriate ratios of reactants with corresponding functional groups. In the preferred case of using dihydroxy-functional and dicarboxy-functional reactants in the preparation, therefore, a corresponding excess of the dihydroxy-functional component is used. In this connection, the following should be explained. For purely statistical reasons, of course, in a real implementation not only molecules are obtained, for example, have the desired (di) -Hydroxyfunktionalität. By choosing suitable conditions, for example an excess of dihydroxy-functional reactants, and conducting the reaction until the desired acid number is obtained, it is guaranteed that the reaction products or molecules constituting the reaction product are on average hydroxy-functional. The person skilled in the art knows how to choose appropriate conditions.

In the preparation of the reaction product, at least one compound (v) is used or reacted as a reactant which has two functional groups (va) and an aliphatic or araliphatic hydrocarbon radical (vb) with 12 to 70, preferably 22 to 55, arranged between the two functional groups. particularly preferably has 30 to 40 carbon atoms. The compounds (v) thus consist of two functional groups and the hydrocarbon radical. As functional groups, of course, the above-described functional groups in question, in particular hydroxyl and carboxyl groups. Aliphatic hydrocarbon radicals are known to be acyclic or cyclic, saturated or unsaturated hydrocarbon radicals which are not aromatic. Araliphatic hydrocarbon radicals are those which contain both aliphatic and aromatic structural units.

The number average molecular weight of the reaction products can vary widely and is preferably from 600 to 40,000 g / mol, in particular from 800 to 10,000 g / mol, very particularly preferably from 1200 to 5000 g / mol. The number average molecular weight is determined in the context of the present invention, unless explicitly stated otherwise, by means of steam pressure osmosis. Was measured by means of a vapor pressure osmometer (Model 10.00, Fa Knauer) in concentration series of the component to be tested in toluene at 50 ° C with benzophenone as a calibration substance for determining the experimental calibration constant of the measuring instrument used (after E. Schröder, G. Müller, K.- F. Arndt, "Leitfaden der Polymercharakterisierung", Akademie-Verlag, Berlin, pp. 47-54, 1982, in which benzil was used as calibration substance).

Preferred compounds (v) are dinner fatty acids or are contained in dinner fatty acids. In the preparation of the reaction products (R) are thus preferably, but not necessarily exclusively, dimer fatty acids used as compound (v). As dimer fatty acids (also known for a long time as dimerized fatty acids or dimer acids) are generally and in particular in the context of the present invention mixtures referred to, which are prepared by oligomerization of unsaturated fatty acids. They can be prepared, for example, by catalytic dimerization of vegetable, unsaturated fatty acids, in particular unsaturated C 12 to C 22 fatty acids being used as starting materials. The linkage proceeds primarily according to the Diels-Alder type and, depending on the number and position of the double bonds of the fatty acids used to prepare the dimer fatty acids, mixtures of predominantly dimeric products which are cycloaliphatic, linear-aliphatic, branched aliphatic and also between the carboxyl groups C6 aromatic hydrocarbon groups exhibit. Depending on the mechanism and / or optionally subsequent hydrogenation, the aliphatic radicals may be saturated or unsaturated and also the proportion of aromatic groups may vary. The residues between the carboxylic acid groups then contain, for example, 24 to 44 carbon atoms. Preferably, fatty acids containing 18 carbon atoms are used for the preparation, so that the dimeric product thus has 36 carbon atoms. Preferably, the radicals linking the carboxyl groups of the dinner fatty acids have no unsaturated bonds and no aromatic hydrocarbon radicals.

For the purposes of the present invention, therefore, cis fatty acids are preferably used in the preparation. Linolenic, linoleic and / or oleic acid are particularly preferably used.

Depending on the reaction regime, mixtures are formed in the above-mentioned oligomerization, which contains mainly dimeric but also trimeric molecules as well as monomeric molecules and other by-products. Usually, it is purified by distillation. Commercially available dinner fatty acids generally contain at least 80% by weight of dimeric molecules, up to 19% by weight of trimeric molecules and at most 1% by weight of monomeric molecules and other by-products.

It is preferred to use dimer fatty acids which consist of at least 90 wt .-%, preferably at least 95 wt .-%, most preferably at least 98 wt .-% of dimeric fatty acid molecules.

For the purposes of the present invention, it is preferred to use dimer fatty acids which consist of at least 90% by weight of dimeric molecules, less than 5% by weight of trimeric molecules and less than 5% by weight of monomeric molecules and other by-products , It is particularly preferred to use dimer fatty acids which 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 other by-products. Likewise particularly preferred dimer fatty acids are used which consist of at least 98 wt .-% of dimeric molecules, less than 1, 5 wt .-% of trimeric molecules and less than 0.5 wt .-% of monomeric molecules and other byproducts. The determination the proportions of monomeric, dimeric and trimeric molecules and other by-products in the dinner fatty acids can be carried out, for example, by means of gas chromatography (GC). The dinner fatty acids are converted before the GC analysis via the boron trifluoride method to the corresponding methyl esters (see DIN EN ISO 5509) and then analyzed by GC.

In the context of the present invention, the basic characteristic of "dimer fatty acids" is that their preparation comprises the oligomerization of unsaturated fatty acids, which is predominantly formed, ie preferably at least 80% by weight, more preferably at least 90% by weight. %, very particularly preferably at least 95% by weight and in particular at least 98% by weight of dimeric products The fact that predominantly dimeric products are formed during the oligomerization and contain exactly two fatty acid molecules justifies this already common name The term "dimer fatty acids" thus refers to "mixture containing dimerized fatty acids." The use of dimeric fatty acids thus automatically implements the use of difunctional compounds (v), which justifies the statement chosen in the context of the present invention that prefers dimer fatty acids as V compound (v) are used. For compounds (v) are evidently the main constituent of the mixtures known as dimer fatty acids. Thus, if dimer fatty acids are used as compounds (v), it is meant that these compounds (v) are used in the form of corresponding mixtures with monomeric and / or trimeric molecules and / or other by-products as described above.

The dimer fatty acids to be used can be obtained as commercial products. Examples include 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 Croda, Empol 1008, Empol 1061 and Empol 1062 of BASF and Unidyme 10 and Unidyme Tl from Arizona Chemical.

Further preferred compounds (v) are dimer diols or are contained in dimerdiols. Dimer diols have long been known and used in the scientific literature also referred to as dimeric fatty alcohols. These are mixtures which are prepared, for example, by oligomerization of unsaturated fatty acids or their esters and subsequent hydrogenation of the acid or ester groups or by oligomerization of unsaturated fatty alcohols. As starting materials, unsaturated C12 to C22 fatty acids or their esters or unsaturated C12 to C22 fatty alcohols can be used. The hydrocarbon radicals linking the hydroxyl groups in the dimer diols are defined as the hydrocarbon radicals separating the carboxyl groups of the dinner fatty acids.

Thus, for example, in DE-1 1 98 348 their preparation is described by dimerization of unsaturated fatty alcohols with basic alkaline earth metal compounds at more than 280 ° C.

They can also be prepared by hydrogenation of Dinnerfettsäuren as described above and / or their esters according to the German patent application DE-B-17 68 313. Under the circumstances described therein, not only the carboxyl groups of the fatty acids are hydrogenated to hydroxyl groups, but also partially or completely hydrogenated optionally also contained in the dimer fatty acids or their esters double bonds. However, it is also possible to carry out the hydrogenation in such a way that the double bonds are completely retained during the hydrogenation. In this case, unsaturated dimer diols are obtained. The hydrogenation is preferably carried out in such a way that the double bonds are hydrogenated as completely as possible.

Another possibility for the preparation of dimerdiols is the dimerization of unsaturated alcohols in the presence of silica / alumina catalysts and basic alkali metal compounds according to International Application WO 91/13918.

Regardless of the methods described for preparing the dimer diols, preference is given to using those dimer diols which have been prepared from cis-fatty acids or their esters or cis-fatty alcohols. In this way predominantly dimer diols with 36 carbon atoms are formed. Dimer diols, which have been prepared by the above-mentioned technical processes, always have varying amounts of trimer triols and monofunctional alcohols. As a rule, the proportion of dimeric molecules is more than 70% by weight and the remainder are trimeric molecules and monomeric molecules. For the purposes of the invention, both these dimer diols can be used as well as purer dimer diols with over 90 wt .-% of dimeric molecules. Particularly preferred are dimer diols with more than 90 to 99 wt .-% of dimeric molecules, of which such dimer diols are again preferred, the double bonds and / or aromatic radicals are at least partially or completely hydrogenated. An alternative term for the term "dimer diols" is thus "mixture containing dimers obtainable by dimerization of fatty alcohols". The use of dimer diols therefore automatically implements the use of difunctional compounds (v). This also justifies the choice made in the context of the present invention that dimer diols are used as compound (v). For compounds (v) are evidently the main constituent of the mixtures called dimer diols. Thus, if dimer diols are used as compounds (v), it is meant that these compounds (v) are used in the form of corresponding mixtures with monomeric and / or thmeric molecules and / or other by-products as described above.

Preferably, the average hydroxy functionality of the dimer diols should be 1.8 to 2.2.

For the purposes of the present invention, it is therefore particularly preferred to use such dimer diols which can be prepared by hydrogenation from the above-described dinner fatty acids. Very particular preference is given to those dimer diols which consist of> 90% by weight of dimeric molecules, <5% by weight of thmerene molecules and <5% by weight of monomeric molecules and other by-products and / or a hydroxyl functionality of 1 , 8 to 2.2. It is particularly preferred to employ such diols which can be prepared by hydrogenation from dinner fatty acids containing from 95 to 98% by weight of dimeric molecules, less than 5% by weight of thmerene molecules and less than 1% by weight. consist of monomeric molecules and other by-products. Likewise particularly preferred are those diols to be used which are characterized by Hydrogenation can be prepared from Dinnerfettsäuren consisting of> 98 wt .-% of dimeric molecules, <1, 5 wt .-% of trimeric molecules and <0.5 wt .-% of monomeric molecules and other by-products.

Dinner fatty acids which can be used to prepare the dimer diols contain, as already described above, depending on the reaction procedure, both aliphatic and optionally aromatic molecular fragments. The aliphatic molecular fragments can also be divided into linear and cyclic, which in turn may be saturated or unsaturated. By means of a hydrogenation, the aromatic and the unsaturated aliphatic molecule fragments can be converted into corresponding saturated aliphatic molecule fragments. The dimer diols which can be used as component (v) can accordingly be saturated or unsaturated. The dimer diols are preferably aliphatic, in particular aliphatic and saturated.

For the purposes of the present invention, preference is given to using those dimer diols which can be prepared by hydrogenating the carboxylic acid groups of preferably saturated aliphatic dimer fatty acids.

Particular preference is given to those diols which can be prepared by hydrogenation from dimer fatty acids containing> 98% by weight of dimeric molecules, <1, 5% by weight of trimeric molecules and <0.5% by weight of monomeric compounds Molecules and other by-products.

The dimer diols particularly preferably have a hydroxyl number of 170 to 215 mg KOH / g, very particularly preferably 195 to 212 mg KOH / g and in particular 200 to 210 mg KOH / g, determined by means of DIN ISO 4629. The dimer diols particularly preferably have a viscosity from 1500 to 5000 mPas, most preferably from 1800 to 2800 mPas (25 ° C, Brookfield, ISO 2555).

Particularly preferred dimer diols to be used are the commercial products Pripol® 2030 and in particular Priopol® 2033 from Uniquema or Sovermol® 908 from BASF. Preferred reaction products (R) can be prepared by reacting dinner fatty acids with aliphatic, araliphatic or aromatic dihydroxy-functional compounds. Aliphatic compounds are organic compounds that are not aromatic. They can be linear, cydic or branched. Possible examples are compounds which consist of two hydroxyl groups and one aliphatic hydrocarbon radical. Also possible are compounds which, in addition to the oxygen atoms contained in the two hydroxyl groups, contain further heteroatoms such as oxygen or nitrogen, in particular oxygen, for example in the form of linking ether and / or ester bonds. Araliphatic compounds are those containing both aliphatic and aromatic structural units. However, it is preferred that the reaction products (R) are prepared by reaction of dinner fatty acids with aliphatic dihydroxy-functional compounds.

The aliphatic, araliphatic or aromatic dihydroxy-functional compounds preferably have a number-average molecular weight of from 120 to 6000 g / mol, more preferably from 200 to 4500 g / mol.

The indication of a number-average molecular weight thus implies that the preferred dihydroxy-functional compounds are mixtures of dihydroxy-functional molecules of different sizes. The dihydroxy-functional compounds are preferably polyether diols, polyester diols or dimer diols.

In the context of the present invention, preference is given to using the dimer fatty acids and the aliphatic, araliphatic and / or aromatic, preferably aliphatic dihydroxy-functional compounds in a molar ratio of from 0.7 / 2.3 to 1.6 / 1, 7, preferably from 0, 8 / 2.2 to 1, 6/1, 8 and most preferably from 0.9 / 2.1 to 1, 5/1, 8 are reacted together. The excess of hydroxyl groups thus hydroxy-functional reaction products are obtained, which also have a low acid number. By the amount of excess, the molecular weight of the reaction product can be controlled. If only a slight excess of the hydroxy-functional reactant is used, correspondingly longer-chain products are formed, since only then is the complete one possible Implementation of existing acid groups is guaranteed. With a higher excess of the hydroxy-functional reactant, correspondingly shorter-chain reaction products are formed. The number average molecular weight of the reaction products is, of course, also influenced by the molecular weight of the reactants, for example the preferred aliphatic dihydroxy-functional compounds. The number-average molecular weight of the preferred reaction products can vary widely and is preferably from 600 to 40,000 g / mol, in particular from 800 to 10,000 g / mol, very particularly preferably from 1200 to 5000 g / mol.

The preferred reaction products can therefore also be described as linear blocky compounds A- (BA) _n . At least one type of blocks is then based on a connection (v). Preferably, the blocks B are based on dimer fatty acids, that is, compounds (v). The blocks A are preferably based on aliphatic dihydroxy-functional compounds, more preferably on aliphatic polyether diols, polyester diols or dimerdiols. In the latter case, the respective reaction product is therefore based exclusively on interconnected compounds (v).

Very particularly preferred reaction products (R) can be prepared by reaction of dimer fatty acids with at least one aliphatic dihydroxy-functional compound of the general structural formula (I):

H R H

O O

(I) wherein R is a C3 to C6 alkylene radical and n is selected accordingly so that the compound of formula (I) has a number average molecular weight of 120 to 6000 g / mol, the dinner fatty acids and the compounds of Formula (I) in a molar ratio of 0.7 / 2.3 to 1, 6/1, 7 are used and wherein the resulting reaction product has a number average molecular weight of 600 to 40,000 g / mol and an acid number of less than 10 mg KOH / g owns.

In a very particularly preferred embodiment, n is chosen here such that the compound of the formula (I) has a number-average molecular weight of 450 to 2200 g / mol, in particular 800 to 1200 g / mol. R is preferably about a C 3 or C ₄ alkylene radical. Particularly preferred is an iso-propylene or a tetramethylene radical. Most preferably, the compound of formula (I) is polypropylene glycol or polytetrahydrofuran. The dinner fatty acids and the compounds of the formula (I) are preferably used here in a molar ratio of 0.7 / 2.3 to 1.3 / 1.7. The resulting reaction product in this embodiment preferably has a number average molecular weight of from 1500 to 5000 g / mol, preferably from 2000 to 4500 g / mol and very particularly preferably from 2500 to 4000 g / mol.

Very particularly preferred reaction products (R) can be prepared by reacting dinner fatty acids with at least one dihydroxy-functional compound of the general structural formula (II):

in which

R is a divalent organic radical containing 2 to 10 carbon atoms, R ¹ and R ² independently of one another represent straight-chain or branched alkylene radicals having 2 to 10 carbon atoms,

X and Y independently of one another are O, S or NR ³ , in which R ^{3 is} hydrogen or an alkyl radical having 1 to 6 carbon atoms, and

m and n are chosen in such a way that the compound of the formula (II) has a number-average molecular weight of 450 to 2200 g / mol,

wherein the components (a) and (b) are used in a molar ratio of 0.7 / 2.3 to 1.6 / 1, 7 and the resulting reaction product has a number average molecular weight of 1200 to 5000 g / mol and an acid number of less than 10 mg KOH / g.

In structural formula (II), R represents a divalent organic radical comprising from 2 to 10 carbon atoms and preferably from 2 to 6 carbon atoms. The radical R may be, for example, aliphatic, aromatic or araliphatic. The rest R can in addition to carbon atoms and hydrogen atoms also contain heteroatoms such as O or N. It can be saturated or unsaturated. Preferably, R is an aliphatic radical having from 2 to 10 carbon atoms, more preferably an aliphatic radical having from 2 to 6 carbon atoms, and most preferably an aliphatic radical having from 2 to 4 carbon atoms. For example, the radical R is C ₂ H, C ₃ H 6, C ₄ H ₈ or C ₂ H - OC ₂ H ₄ .

R ¹ and R ² independently of one another represent straight-chain or branched alkylene radicals having 2 to 10 carbon atoms, preferably 2 to 6 carbon atoms and particularly preferably 3 to 5 carbon atoms. Preferably, these radicals contain only carbon and hydrogen.

In the compounds of structural formula (II), all n radicals R ¹ and all m radicals R ^{2 may be} identical. Likewise, it is also possible that different types of radicals R ¹ and R ² are present. Preferably, all radicals R ¹ and R ^{2 are the} same.

R ¹ and R ² are very particularly preferably a C ₄ - or a C ₅ -alkylene radical, in particular a tetramethylene or pentamethylene radical. In a very particularly preferred embodiment of the present invention, both radicals R ¹ and R ^{2 are} pentamethylene radicals.

X and Y independently represent O, S or NR ³ , wherein R ^{3 is} hydrogen or an alkyl radical having 1 to 6 carbon atoms. Preferably, X and Y independently of one another are O or NR ³ , more preferably these are independently of one another O and NH, very particularly preferably X and Y are O.

The indices m and n are correspondingly chosen so that the compounds of structural formula (II) has a number average molecular weight of 450 to 2200 g / mol, preferably 500 to 1400 g / mol, particularly preferably 500 to 1200 g / mol. The polyester polyols of the general structural formula (I) can be prepared in a first route by acting compounds HX-R-YH as so-called starter compounds and by ring-opening polymerization of lactones of the hydroxycarboxylic HO-R ¹ -COOH and HO-R ² -COOH the hydroxy-terminated polyester chains are polymerized to the initiator compound. Of course, according to a second route, alpha-hydroxy-gamma-carboxy-terminated polyesters can first be prepared, for example by ring-opening polymerization of lactones of the hydroxycarboxylic acids HO-R ¹ -COOH and HO-R ² -COOH or by polycondensation of the hydroxycarboxylic acids HO-R ¹ -COOH and HO-R ² -COOH. The alpha-hydroxy-gamma-carboxy-terminated polyesters can then in turn be reacted with compounds HX-R-YH by means of a condensation reaction to give the polyester diols to be used according to the invention.

Corresponding methods are described, for example, in the German Offenlegungsschrift 2234265 "hydroxyl-terminated polylactones" of the Applicant Stamicarbon N.V.

The dinner fatty acids and the compounds of the formula (II) are used here preferably in a molar ratio of 0.7 / 2.3 to 1.3 / 1.7. The resulting reaction product in this embodiment preferably has a number average molecular weight of 1200 to 5000 g / mol, preferably 1200 to 4500 g / mol and very particularly preferably 1200 to 4000 g / mol.

Also very particularly preferred reaction products (R) can be prepared by reaction of dinner fatty acids with dimerdiols, the dimer fatty acids and dimer diols in a molar ratio of 0.7 / 2.3 to 1, 6/1, 7 are used and the resulting reaction product a number average Molecular weight of 1200 to 5000 g / mol and an acid number of less than 10 mg KOH / g.

Preferred dimer diols have already been described above. It is preferred here that the dimer fatty acids and dimer diols are used in a molar ratio of 0.7 / 2.3 to 1.3 / 1.7. The resulting reaction product here preferably has a number-average molecular weight of 1200 to 5000 g / mol, preferably 1300 to 4500 g / mol and very particularly preferably 1500 to 4000 g / mol.

It follows from the above that the reaction products (R) can be prepared by the exclusive use of compounds (v). For example it is it is possible to prepare the reaction products through the use of the preferred dinner fatty acids and dimer diols described above. Both classes of compounds are compounds (v) or both classes of compounds are mixtures containing difunctional compounds (v). However, it is equally possible to prepare reaction products (R) by reacting compounds (v), preferably dinner fatty acids, with other organic compounds, especially those of the structural formulas (I) and (II).

In the context of the present invention, it is preferred that from 25 to 100 mol% of at least one compound (v) be used in the preparation of the reaction products. If only compounds (v) are used, then evidently at least two compounds (v) are used.

The proportion of the reaction products (R) is preferably in the range of 0.1 to 15 wt .-%, preferably 0.5 to 12 wt .-%, particularly preferably 0.75 to 8 wt .-%, each based on the total weight the aqueous coating composition according to the invention.

If the content of the reaction products (R) is less than 0.1% by weight, it may be possible that no improvement in pinhole resistance is achieved. If the content is more than 15% by weight, disadvantages may occur under certain circumstances, such as an incompatibility of the said reaction product in the aqueous coating agent. Such incompatibility may be manifested, for example, by uneven trajectory as well as by flooding or settling.

The reaction product to be used according to the invention is generally sparingly soluble in aqueous systems. It is therefore preferably used directly in the preparation of the aqueous coating composition and not added only after the preparation in the otherwise finished coating composition.

The coating composition according to the invention comprises at least one specific polyurethane resin (X), preferably exactly one such polyurethane resin. Polyurethane resins are basically known, their preparation and the starting compounds which can be used in the preparation, in particular polyisocyanates and polyols, which are also used for the preparation of the polyurethane resin (X), are described, for example, in WO 92/15405 A1, page 4, line 28 to page 10, Line 32 and page 14, line 13 to page 15, line 28, or also in DE 199 48 004 A1, page 4, line 19 to page 9, line 62 and / or also above in the description of the in step (i) the preparation of the copolymer (MP) polyurethane used described.

It is preferred that the at least one polyurethane resin (X) is carboxy-functional. It preferably has an acid number of 5 to 100 mg KOH / g, more preferably 7 to 50 mg KOH / g, particularly preferably 15 to 35 mg KOH / g. In particular, by the presence of carboxylic acid groups, the polyurethane resin (X) can be stabilized hydrophilic or the polyurethane resin (X) has an increased dispersibility in aqueous media, so that it can be converted into aqueous dispersions without adverse effects as described below and thus also in the inventive aqueous Coating can be integrated. Such carboxylic acid groups may also be present as ionic carboxylate groups, depending on the pH or, depending on the use of neutralizing agents known in this sense. Carboxylic acid groups thus belong to the functional groups that can be converted into ionic groups (potentially ionic groups). To neutralize the carboxyl groups, for example, ammonia, amines and / or amino alcohols such as di- and triethylamine, dimethylaminoethanol, diisopropanolamine, morpholines and / or N-alkylmorpholines are used.

The carboxylic acid groups are used in the preparation of the polyurethane resin (X) by the use of appropriate starting compounds for the preparation of these polyurethane resins, namely by carboxyl-containing compounds (x.1) containing at least one carboxylic acid group and at least one isocyanate-reactive functional group, preferably hydroxyl groups. In this way, the incorporation of the compound (x.1) in the polyurethane backbone and at the same time the introduction of carboxylic acid groups in the polyurethane resin (X) succeeds. Preferably contains the Compound (x.1) at least one carboxylic acid group and at least two hydroxyl groups, most preferably one carboxylic acid group and two hydroxyl groups.

As compounds (x.1) are, if carboxyl groups, for example, polyether polyols and / or polyester polyols, in particular polyester polyols, into consideration. Such polyester polyols are described for example in DE 39 03 804 A1 and can be prepared in a manner known to those skilled in the art. Thus, the stated polyester polyols (x.1) can be prepared, for example, by a common polyester synthesis in organic solvents and in the presence of common catalysts such as dibutyltin laurate, besides typically used difunctional monomeric starting compounds, that is diols and dicarboxylic acids and corresponding anhydrides, and trifunctional starting compounds such Triols, tricarboxylic acids and corresponding anhydrides such as trimellitic anhydride and dihydroxycarboxylic acids can be used. In this way, the introduction of possible branching points allows the preparation of polyesters which may contain both hydroxyl groups and carboxylic acid groups. Since a polyester as a polymeric system always represents a mixture of molecules of different sizes, the abovementioned features, for example with regard to the existence of carboxylic acid groups or hydroxyl groups in polyesters (x.1), are evidently understood as statistical mean values. Such compounds (x.1) preferably have number-average molecular weights of from 300 to 3000 g / mol. The preparation of such compounds (x.1) is achieved by simple adaptation of, for example, reaction conditions and ratios of the starting materials described.

However, as compound (x.1), preference is given to using low molecular weight compounds which have at least one carboxylic acid group and at least one isocyanate-reactive functional group, preferably hydroxyl groups. In the context of the present invention, the term "low molecular weight compound" is to be understood as meaning, in contrast to relatively high molecular weight compounds, in particular polymers, those which, as preferably monomeric compounds, have a discrete molecular weight can be assigned. A low molecular weight compound is thus in particular not a polymer, since the latter always represent a mixture of molecules and must be described by means of average molecular weights. The term low molecular weight compound is preferably to be understood as meaning that corresponding compounds have a molecular weight of less than 300 g / mol. Preferably, the range is from 100 to 200 g / mol.

Preferred compounds (x.1) in this sense are, for example, monocarboxylic acids containing two hydroxyl groups, for example dihydroxypropionic acid, dihydroxysuccinic acid and dihydroxybenzoic acid. Very particularly preferred compounds (x.1) are alpha, alpha dimethylolalkanoic acids such as 2,2-dimethylolacetic acid, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid and 2,2-dimethylolpentanoic acid, in particular 2,2-dimethylolpropionic acid.

The preparation of the polyurethane resins (X) can be carried out by known and established methods in bulk or solution, more preferably by reacting the starting compounds used in typical organic solvents such as methyl ethyl ketone at elevated temperatures and optionally using catalysts typical for polyurethane production. Such catalysts are known to the person skilled in the art, an example being dibutyltin laurate.

It is preferred, however, that the preparation at temperatures of not higher than 120 ° C, preferably from 30 to 100 ° C, in particular from 40 to 90 ° C. This has the advantage that the carboxylic acid groups present in the compounds (x.1) do not or only to a minor extent react with the polyols present to form ester bonds, so that the carboxylic acid groups remain in their free form and thus the carboxy functionality of the polyurethane resin (X ). In any case, the stated temperatures are sufficient to permit an effective reaction of isocyanates with alcohols and amines. In this sense, it is likewise preferred if no catalysts suitable for polyurethane production, for example dibutyltin laurate, are used. For it is known that catalysts which can be used for the production of polyurethane generally also catalyze ester formation. Preference is given to the polyurethane resin after the preparation, which preferably in organic solvents, is converted into an aqueous dispersion. This is preferably done by adding neutralizing agents already mentioned above and adding water and distilling off the at least one organic solvent. The addition of water is carried out so that the dispersions of the polyurethane resin (X) have a solids content (non-volatile content) of preferably 10 to 60 wt .-%, in particular 15 to 45 wt .-%. The polyurethane resin (X) is preferably used in the form of such dispersions in the coating composition according to the invention.

The preparation of the polyurethane resins (X) preferably proceeds such that first difunctional starting compounds, preferably diols and diisocyanates, and one component (x.1) are reacted with one another to give a prepolymer which still contains isocyanate groups and then this with at least three hydroxyl groups, preferably exactly three hydroxyl groups having reacted starting compound. Preference is given to monomeric triols, in particular trimethylolethane, trimethylolpropane and glycerol. Subsequently, it is then neutralized as described with preferably tertiary amines and the polyurethane resin (X) dispersed in water.

At least one polyester diol, at least one monomeric diol, at least one monomeric compound (x.1) as described above and at least one polyisocyanate are preferably reacted in the first step and then reacted with at least one monomeric triol as described above in the second step.

In the context of the present invention, it is preferred that at least 70% by weight of the starting compounds used for the preparation of the polyurethane resin (X) are those which are polymerizable (that is to say suitable for the construction of polymeric backbones) groups exclusively of isocyanate groups, hydroxyl groups and carboxylic acid groups and thereof containing derived anhydride groups. In this way, and by the suitable choice of known reaction conditions for the preparation of polyurethane resins succeeds in the production of resins in which the linkage of the starting compounds mainly urethane bonds (by reaction of isocyanate groups and hydroxyl groups) runs and the carboxylic acid groups Realization of the invention essential acid number remain in unreacted form in the polymer. The polyurethane resin (B) is thus a resin in which the combination of these starting compounds is realized primarily by urethane bonds by the appropriate choice of starting compounds. Other functional polymerizable groups are known to the person skilled in the art. Ultimately, this all come into question for the production of polycondensation and polyaddition resins in question groups and olefinically unsaturated groups, as in vinyl group-containing, allylgruppenhaltigen and acrylic and methacrylgruppenhaltigen starting compounds for the production of free-radical polymerization resins such as (meth) acrylate (co) polymers consider. Examples which may be mentioned are thio, N-methylolamino-N-alkoxymethylamino, imino, carbamate, allophanate, epoxy, methylol, methylol ether, siloxane, carbonate, amino, and beta-hydroxyalkylamide groups and vinyl, allyl and acrylic, methacrylic groups. It is preferred that at least 80 wt .-%, preferably at least 90 wt .-%, most preferably 100 wt .-% of the starting compounds used for the preparation of polyurethane resins (X) exclusively isocyanate groups, hydroxyl groups and carboxylic acid groups as polymerizable groups. It is therefore particularly preferred that the polyurethane resin (X) is not a copolymer.

The number average molecular weight of the polyurethane resins (X) can vary widely. It is preferably in the range from 1000 to 50,000 g / mol, in particular from 2000 to 30,000 g / mol.

The proportion of the polyurethane resins (X) is preferably in the range of 0.1 to 15 wt .-%, preferably 0.5 to 10 wt .-%, particularly preferably 0.75 to 8 wt .-%, each based on the total weight the aqueous coating composition according to the invention.

The coating compositions of the invention preferably contain pigments, that is, color and / or effect pigments. Such color pigments and effect pigments are known to the person skilled in the art and are described, for example, in Rompp-Lexikon Lacke and Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, pages 176 and 451. The terms coloring pigment and Color pigment as well as the terms optically effecting pigment and effect pigment are interchangeable.

Preferred effect pigments are, for example, platelet-shaped metallic effect pigments such as platelet-shaped aluminum pigments, gold bronzes, fire-colored bronzes and / or iron oxide-aluminum pigments, pearlescent pigments such as fish-silver, basic lead carbonate, bismuth oxychloride and / or metal oxide-mica pigments and / or other effect pigments such as bubble-shaped graphite, platelet-shaped iron oxide, multilayer Effect pigments from PVD films and / or liquid crystal polymer pigments. Particular preference is given to platelet-shaped metallic effect pigments, in particular platelet-shaped aluminum pigments.

Typical color pigments include, in particular, inorganic color pigments, such as white pigments, such as titanium dioxide, zinc white, zinc sulfide or lithopone; Black pigments such as carbon black, iron manganese black or spinel black; Colored pigments such as chromium oxide, chromium oxide hydrate green, cobalt green or ultramarine green, cobalt blue, ultramarine blue or manganese blue, ultramarine violet or cobalt and manganese violet, iron oxide red, cadmium sulfoselenide, molybdate red or ultramarine red; Iron oxide brown, mixed brown, spinel and corundum phases or chrome orange; or iron oxide yellow, nickel titanium yellow, chromium titanium yellow, cadmium sulfide, cadmium zinc sulfide, chrome yellow or bismuth vanadate.

The proportion of the pigments can be, for example, in the range from 1 to 30% by weight, preferably from 1 to 5% by weight, particularly preferably from 2.0 to 15% by weight, based on the total weight of the coating composition according to the invention.

The coating compositions according to the invention comprise, by the use of components (MP), (R) and (X), curable binders, in particular physically and thermally curable binders. In the context of the present invention, the binder according to the relevant DIN EN ISO 4618 is understood as meaning the nonvolatile fraction of a coating composition without pigments and fillers. Accordingly, special binders are, for example, also paint-typical additives, the copolymer (MP), the reaction product (R), the polyurethane resin (X) or other usable polymers as described below and typical as described below Networking agent. However, for the sake of clarity, the term below is used mainly in relation to certain physically and thermally curable polymers, for example certain polyurethanes, polyesters, polyacrylates and / or copolymers of said polymers.

In the context of the present invention, the term "physical curing" means the formation of a film by the release of solvent from polymer solutions or polymer dispersions, usually without the need for crosslinking agents.

In the context of the present invention, the term "thermal curing" means the heat-initiated crosslinking of a lacquer layer in which either a separately present crosslinking agent or else self-crosslinking binder is applied in the underlying lacquer The crosslinking agent contains reactive functional groups which belong to those described in US Pat Usually, this is referred to by the experts as extraneous crosslinking If the complementary reactive functional groups or autoreactive functional groups, ie groups which react with groups of the same type, are already present in the binder molecules, self-crosslinking binders are present Examples of suitable complementary reactive functional groups and autoreactive functional groups are known from German patent application DE 199 30 665 A1, page 7, line 28 to page 9, lines 24.

The coating composition according to the invention preferably also contains at least one polymer other than the copolymers (MP), the reaction products (R) and the polyurethane resins (X) as binder, in particular at least one polymer selected from the group consisting of polyurethanes, polyesters, polyacrylates and / or copolymers said polymers, in particular polyurethane-polyacrylates. Preferred of the copolymers (MP) different polyurethane-polyacrylate copolymers (acrylated polyurethanes) and their preparation are described for example in WO 91/15528 A1, page 3, line 21 to page 20, line 33 and in DE 4437535 A1, page 2, line 27 to page 6, line 22 described. The polymers described as binders are preferably hydroxy-functional. Preferably, the inventive Coating composition in addition to the at least one copolymer (MP), the at least one reaction product (R) and the at least one polyurethane resin (X) at least one of the copolymers (MP) different polyurethane-polyacrylate copolymer.

The proportion of the further polymers as binders, preferably the at least one of the copolymers (MP) different polyurethane-polyacrylate copolymer, is preferably in the range of 0.5 to 20.0 wt .-%, preferably 1, 0 to 15.0 Wt .-%, particularly preferably 1, 5 to 10.0 wt .-%, each based on the total weight of the coating composition of the invention.

In addition, the coating composition according to the invention preferably contains at least one typical crosslinking agent known per se. It preferably contains as crosslinking agent at least one aminoplast resin and / or a blocked polyisocyanate, preferably an aminoplast resin. Among the aminoplast resins, melamine resins are particularly preferred.

The proportion of crosslinking agents, in particular aminoplast resins and / or blocked polyisocyanates, more preferably aminoplast resins, preferably melamine resins, is preferably in the range from 0.5 to 20.0% by weight, preferably from 1 to 0 to 15.0% by weight. , Particularly preferably 1, 5 to 10.0 wt .-%, each based on the total weight of the coating composition of the invention.

It follows from the above that the coating composition according to the invention is preferably thermally curable and externally crosslinking. Because by the use of hydroxy-functional reaction products (R), preferably hydroxy-functional polyurethane-polyacrylate copolymers which are different from the copolymers (MP) and crosslinking agents, in particular melamine resins, a corresponding external crosslinking can be realized. By specifying that a coating agent is self-crosslinking and / or externally crosslinking, it is to be understood in the context of the present invention that this coating composition contains polymers as binders and optionally crosslinking agents which can crosslink together accordingly. The underlying mechanisms as well as usable binders and crosslinking agents are described above. The coating composition according to the invention preferably also comprises at least one thickener. Suitable thickeners are inorganic thickeners from the group of layered silicates. Particularly suitable are lithium-aluminum-magnesium silicates. In addition to the inorganic thickeners, however, it is also possible to use one or more organic thickeners. These are preferably selected from the group consisting of (meth) acrylic acid (meth) acrylate Copolymerisat- thickeners, such as the commercial product Rheovis AS S130 (BASF) and polyurethane thickeners, such as the commercial product Rheovis PU 1250 (BASF). The thickeners used are different from the polymers described above, for example the preferred binders. Preference is given to inorganic thickeners from the group of layered silicates.

The proportion of thickeners is preferably in the range of 0.01 to 5.0 wt .-%, preferably 0.02 to 4 wt .-%, particularly preferably 0.05 to 3.0 wt .-%, each based on the Total weight of the coating composition according to the invention.

In addition, the coating composition of the invention may contain at least one additional additive. Examples of such additives are residue-free or substantially residue-free thermally decomposable salts, of the polymers mentioned as binders various physically, thermally and / or actinic radiation curable resins as binders, other crosslinking agents, organic solvents, reactive diluents, transparent pigments, fillers, molecular disperse soluble dyes, nanoparticles, light stabilizers, antioxidants, deaerators, emulsifiers, slip additives, polymerization inhibitors, free radical polymerization initiators, primers, leveling agents, film forming aids, sag-control agents (SCAs), flame retardants, corrosion inhibitors, waxes, siccatives, biocides and matting agents.

Suitable additives of the aforementioned type are, for example, from German Patent Application DE 199 48 004 A1, page 14, line 4, to

page

17, line 5, German Patent DE 100 43 405 C1, column 5, paragraphs [0031] to [0033]. They are used in the usual and known quantities. For example, their proportion may be in the range of 1.0 to 20.0% by weight, based on the total weight of the aqueous coating agent.

The solids content of the coating compositions according to the invention can vary depending on the requirements of the individual case. In the first place, the solids content depends on the viscosity required for application, in particular spray application, so that it can be adjusted by the person skilled in the art on the basis of his general knowledge, if appropriate with the aid of less orienting tests.

The solids content of the coating composition according to the invention is preferably from 5 to 70% by weight, more preferably from 8 to 60% by weight, most preferably from 12 to 55% by weight.

The term solids content (non-volatile content, solids content) is to be understood as the proportion by weight which remains under evaporation as a residue under defined conditions. In the present application, the solids are determined according to DIN EN ISO 3251. For this purpose, the basecoat is evaporated for 60 minutes at 130 ° C.

Unless stated otherwise, this test method is also used, for example, to specify or predetermine the proportion of various components of the coating composition, for example a copolymer (MP) or a crosslinking agent, in the total weight of the coating composition. Thus, the solid is determined from a dispersion of a copolymer (MP) or a crosslinking agent to be added to the coating composition. By taking into account the solids content of the dispersion and the amount of dispersion used in the coating composition, it is then possible to determine or determine the proportion of the component in the overall composition. The coating composition according to the invention is aq. The term "aqueous" is known to the person skilled in the art in this context, which is basically a coating agent which is not based exclusively on organic solvents, that is to say not exclusively as solvent on an organic basis, but on the contrary as solvent contains a significant amount of water In the context of the present invention, "aqueous" is to be understood as meaning that the respective coating agent has a proportion of at least 40% by weight, preferably at least 50% by weight, very particularly preferably at least 60% by weight, in particular at least 70 wt .-% water, in each case based on the total amount of the solvent contained (that is, water and organic solvents). Of these, the proportion of water is preferably from 40 to 95% by weight, in particular from 50 to 92.5% by weight, very particularly preferably from 60 to 90% by weight, particularly preferably from 70 to 87.5% by weight, in each case based on the total amount of solvents contained.

The same definition of aqueous, of course, applies to all other systems described in the context of the present invention, for example for the aqueous character of the aqueous dispersions of the copolymers (MP).

The preparation of the coating compositions according to the invention can be carried out using the customary and known for the production of basecoats mixing methods and mixing units.

The coating composition according to the invention is preferably a basecoat material or the coating composition is preferably used as the basecoat material. This applies in particular in the context of the method according to the invention described below.

A basecoat is to be understood as meaning an intermediate coating substance which is generally used in the automotive finishing and general industrial coating, and which is generally colored and / or effects. This is generally applied to a pre-treated with filler or Grundierfüller metal or plastic substrate, sometimes even applied directly to the plastic substrate. Even old paints, which may still have to be pretreated (for example, by Sanding), can serve as substrates. Meanwhile, it is quite common to apply more than one basecoat. Accordingly, in such a case, a first basecoat film is the background for a second. In order to protect a basecoat film in particular against environmental influences, at least one additional clearcoat film is applied to it.

The inventive method and the multi-layer coating according to the invention

Likewise provided by the present invention is a process for the production of multicoat paint systems in which

(1) an aqueous basecoat is applied to a substrate,

(2) a polymer film is formed from the varnish applied in step (1),

(3) a clearcoat is applied to the basecoat so obtained and then

(4) the basecoat film is cured together with the clearcoat film, which is characterized in that the aqueous basecoat used in step (1) is a coating composition according to the invention.

All above-mentioned statements with regard to the coating composition according to the invention also apply to the process according to the invention. This applies in particular to all preferred, particularly preferred and very particularly preferred features. Particularly preferably, the basecoat contains a pigment, so it is pigmented.

Said method is preferably used for the production of multicoat color finishes, effect paints and color and effect finishes.

The application of the aqueous basecoat material to be used in accordance with the invention is usually carried out on metal or metal primer or primer filler pretreated Plastic substrates. Optionally, said basecoat can also be applied directly to the plastic substrate.

If a metal substrate is to be coated, it is preferably coated with an electrodeposition coating before application of the filler or primer filler.

If a plastic substrate is coated, this is preferably pretreated before the application of the filler or Grundierfüllers. The most commonly used methods are flaming, plasma treatment and corona discharge. Preferably, the flaming is used.

The application of the pigmented aqueous basecoat material according to the invention to a metal substrate can take place in the layer thicknesses customary within the framework of the automobile industry in the range of, for example, 5 to 100 micrometers, preferably 5 to 60 micrometers. Spray application methods are used, such as compressed air spraying, airless spraying, high rotation, electrostatic spray application (ESTA), if necessary combined with hot spray application such as hot air hot spraying.

After application of the pigmented aqueous basecoat, it can be dried by known methods. For example, (1-component) basecoats, which are preferred, may be flashed off at room temperature for 1 to 60 minutes, and subsequently preferably dried at optionally slightly elevated temperatures of 30 to 90 ° C. In the context of the present invention, flash drying and drying is understood to mean evaporation of organic solvents and / or water, as a result of which the paint is drier but not yet cured, or a completely crosslinked paint film is not yet formed.

Then, a commercial clearcoat is also applied according to common methods, wherein the layer thicknesses are again in the usual ranges, for example 5 to 100 micrometers. Preference is given to two-component clearcoats. After application of the clearcoat, it may be flashed off at room temperature for, for example, 1 to 60 minutes and, if appropriate, dried. Then the clearcoat is cured together with the applied basecoat. In this case, for example, crosslinking reactions take place, as a result of which a color and / or effect multilayer coating according to the invention is produced on a substrate. The curing is preferably carried out thermally at temperatures of 60 to 200 ° C.

All layer thicknesses specified in the context of the present invention are understood as dry layer thicknesses. It is therefore the layer thickness of the respective cured layer. If, therefore, it is stated that a lacquer is applied in a certain layer thickness, it is to be understood that the lacquer is applied in such a way that the said layer thickness results after hardening.

The coating of plastic substrates is basically analogous to that of metal substrates. However, it is generally cured at much lower temperatures of 30-90 ° C to avoid damaging and / or deforming the substrate.

With the aid of the method according to the invention, therefore, it is possible to coat metallic and non-metallic substrates, in particular plastic substrates, preferably automobile bodies or parts thereof.

The process according to the invention can also be used for double-coating in the OEM coating. This is to be understood as meaning that a substrate which has been coated with the aid of the method according to the invention is lacquered a second time, likewise with the aid of the method according to the invention.

The invention further relates to multi-layer coatings, which can be produced by the method described above. These multicoat paint systems will be referred to below as multicoat paint systems according to the invention.

All above-mentioned statements with regard to the aqueous coating composition according to the invention and the method according to the invention also apply correspondingly to said multi-layer coating. This is especially true also for all preferred, particularly preferred and very particularly preferred features.

The multicoat paint systems according to the invention are preferably multicoat color finishes, effect paint systems and color and effect paint systems.

A further aspect of the invention relates to the process according to the invention, wherein the said substrate from step (1) is a multicoat system which has defects. In this multi-layer substrate coating, which has defects, so it is an original paint, which is repaired ("Spot Repair") or completely over-painted (double-coating) is.

The inventive method is therefore also suitable for repairing defects on multi-layer coatings. Defects or film defects are generally termed disturbances on and in the coating, which are usually named according to their shape or appearance. A variety of possible types of such film defects are known to those skilled in the art. These are described, for example, in Rompp-Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, page 235, "film defects".

In addition, the present invention relates to the use of the aqueous coating composition for improving the stability of multicoat paint systems against optical defects, in particular pinholes. If the aqueous coating compositions according to the invention are thus used in the coating of metal and plastic substrates, their use leads, in particular, to an improvement in the stability of the painted coating against pinholes. This applies in particular when the aqueous coating composition according to the invention is used as a basecoat and a multi-layer coating according to the invention is built up by the process according to the invention.

The stability against pinholes can be tested by known methods. In particular, the already described at the beginning of the needlestick and the offer Number of pinholes at a given layer thickness as proof of pinhole stability.

In the following the invention will be explained by means of examples. Examples

Specification of certain components used and measurement methods

Dinner fatty acid:

The dinner fatty acid used contains less than 1.5% by weight of trimeric molecules, 98% by weight of dimeric molecules and less than 0.3% by weight of fatty acid (monomer). It is produced on the basis of linoleic, linoleic and oleic acid (Pripol ™ 1012-LQ (GD) (Croda)).

Polyester 1 (P1):

Prepared according to Example D, column 16, lines 37 to 59 of DE 4009858 A. The corresponding solution of the polyester has a solids content of 60% by weight, the solvent used being butylglycol instead of butanol, that is to say mainly butylglycol and water as solvent are included.

Determination of the number average molecular weight:

The number average molecular weight was determined by steam pressure osmosis. Was measured by means of a vapor pressure osmometer (Model 10.00, Fa Knauer) in concentration series of the component to be tested in toluene at 50 ° C with benzophenone as a calibration substance for determining the experimental calibration constant of the measuring instrument used (after E. Schröder, G. Müller, K.- F. Arndt, "Leitfaden der Polymercharakterisierung", Akademie-Verlag, Berlin, pp. 47-54, 1982, in which benzil was used as calibration substance). Preparation of a Mixed Polymer (MP) to be Used According to the Invention

A copolymer (MP) or an aqueous dispersion containing this polymer was prepared as follows. a) A dispersion of an alpha-methylstyryl-containing polyurethane was prepared in accordance with the patent DE 19948004 B4, page 27, Example 1, "Preparation of a polyurethane (B) according to the invention", wherein additionally trimethylolpropane was used and the solid content of the resulting dispersion only 29 instead of 35.1% by weight, based on the adduct (B2), preparation example 1 mentioned in the patent DE 19948004 B4, an adduct with monoethanolamine instead of diethanolamine was prepared:

For this purpose, 200.0 parts by weight of methyl ethyl ketone, 800.0 parts by weight of N-methylpyrrolidone and 221, 3 parts by weight of monoethanolamine (BASF SE) were initially charged at 20 ° C in a reaction vessel equipped with stirrer, internal thermometer, reflux condenser and electric heating under nitrogen. Were during one and a half hours 778.7 parts by weight of 1 to this mixture, - (1 -lsocyanato- 1-methylethyl) -3- (1 -methylethenyl) -benzene having an isocyanate content of (TMI ^® (META) Aliphatic Unsaturated isocyanates, Cytec). 20.4 wt .-% isocyanate was added dropwise, so that the reaction temperature 40 ° C was not exceeded. The resulting reaction mixture was stirred until no more free isocyanate groups were detectable. Thereafter, the reaction mixture was stabilized with 200 ppm hydroquinone.

The theoretical solids content of the thus prepared solution of the adduct described was 50 wt .-%.

Now, in another reaction vessel equipped with stirrer, internal thermometer, reflux condenser and electric heater, 431.7 parts by weight of a linear polyester polyol and 69.7 parts by weight of dimethylolpropionic acid (GEO Specialty Chemicals) in 355.8 parts by weight of methyl ethyl ketone and 61.6 parts by weight of N Methylpyrrolidone dissolved under nitrogen. The linear polyester polyol was previously from dimerized fatty acid (Pripol ^® 1012 Fa. Uniqema), isophthalic acid (From BP Chemicals) and hexane-1,6-diol (from BASF SE) (weight ratio of the starting materials: dimer fatty acid to isophthalic acid to hexane-1,6-diol = 54.00: 30.02: 15.98 ) and had a hydroxyl number of 73 mg KOH / g solids and a number average molecular weight of 1379 g / mol. 288.6 parts by weight of isophorone diisocyanate (Basonat® I, BASF SE) having an isocyanate content of 37.75% by weight were added to the resulting solution at 45 ° C. After the exothermic reaction subsided, the reaction mixture was slowly heated to 80 ° C with stirring. It was further stirred at this temperature until the isocyanate content of the solution was 3.2 wt .-% and was constant. Thereafter, the reaction mixture was cooled to 65 ° C and 85.2 parts by weight of the above-described adduct was added together with 21.8 parts by weight of trimethylolpropane (BASF SE). The resulting reaction mixture was stirred at 65 ° C until the isocyanate content of the solution had dropped to 1, 0 wt .-%. Now 22.2 wt .-% diethanolamine (BASF SE) were added and the content of isocyanate groups followed until no more free isocyanate groups were detectable. The resulting, dissolved polyurethane was admixed with 139.7 parts by weight of methoxypropanol and 43.3 parts by weight of triethylamine (BASF SE). Thirty minutes after the addition of the amine, the temperature of the solution was lowered to 60 ° C, followed by adding 1981 parts by weight of deionized water while stirring for 30 minutes. From the resulting dispersion, the methyl ethyl ketone was distilled off at 60 ° C under vacuum. Thereafter, any solvent and water losses were compensated.

The resulting dispersion of an alpha-methylstyryl-containing polyurethane had a solids content of 29.0% by weight, the acid number was 34.0 mg KOH / g solids content and the pH was 7.0 (measured at 23 ° C ). b) For the preparation of the aqueous primary dispersion of the copolymer (MP) according to the invention under nitrogen atmosphere 1961, 2 parts by weight of the alpha-methylstyryl-containing polyurethane dispersion according to a) with 40.0 parts by weight of methoxypropanol (0.07% on polyurethane) and 686.5 parts by weight deionized Diluted with water and heated to 80 ° C. After the reactor contents were heated to 80 ° C, 0.6 parts by weight of ammonium peroxodisulfate, dissolved in 35.7 Parts by weight of deionized water, added under normal pressure in the reactor. Subsequently, with continued stirring, a mixture of 301, 6 parts by weight of methyl methacrylate, 261, 6 parts by weight of n-butyl acrylate, 5.6 parts by weight of allyl methacrylate (0.87 mol% based on total vinyl monomer) and 134.9 parts by weight of N-methylpyrrolidone for 5 hours evenly added. At the beginning of the addition of the monomer mixture, a solution of 1.1 parts by weight of ammonium peroxodisulfate in 71.3 parts by weight of deionized water was also added over five hours.

During the radical polymerization, the content of free monomers was determined by gas chromatography (GC) every 30 minutes (GC: once 50m silica capillary column with polyethylene glycol phase and once with 50m silica capillary column with polydimethylsiloxane phase, carrier gas helium, split injector 150 ° C, oven temperature 40-220 ° C, Flammionisationsdetektor, detector temperature 275 ° C, internal standard isobutyl acrylate), after 30 min, the highest total monomer content based on dispersion with 0.5 wt .-% was determined (3.1 wt. % based on the total amount of olefinically unsaturated monomers used for the polymerization).

After simultaneous termination of the monomer and initiator feed, the resulting reaction mixture was stirred at 80 ° C for a further hour and then cooled to room temperature.

The resulting primary dispersion of the copolymer had a very good storage stability. Their solids content was 32.5 wt .-%, the acid number at 18.8 mg KOH / g solids content and its pH at 7.0. The particle size (z-average) by means of photon correlation spectroscopy was 96 nm. By gas chromatography (GC: once with 50m silica capillary column with polyethylene glycol phase and once 50m silica capillary column with polydimethylsiloxane phase, carrier gas helium, split injector 250 ° C, oven temperature 40 - 220 ° C., flame ionization detector, detector temperature 275 ° C., internal standard n-propylglycol), a content of 2.7% by weight of methoxypropanol and 5.7% by weight of N-methylpyrrolidone was determined. The gel content was determined gravimethsch after extraction of the freeze-dried polymer by means of tetrahydrofuran with 80.3 wt .-%. For this purpose, the dispersion was freeze-dried, the mass of the freeze-dried polymer was determined to extract the polymer then 24 hours at 25 ° C in an excess of tetrahydrofuran (ratio of tetrahydrofuran to freeze-dried copolymer = 300: 1). The insoluble fraction (gel fraction) was isolated, dried for 4 hours at 50 ° C in a convection oven, and then weighed back.

Preparation of a Reaction Product (R) to be Used According to the Invention

In a 4 l stainless steel reactor equipped with anchor stirrer, thermometer, condenser, thermometer for head temperature measurement and water separator were added 2000.0 g of linear diol polyTHF 1000 (2 mol), 579.3 g of dinner fatty acid (1 mol) and 51 g of cyclohexane in the presence of 2 , 1 g of di-n-butyltin oxide ( ^Axion® CS 2455, Chemtura) heated to 100 ° C. It was slowly heated until the onset of condensation. At a maximum head temperature of 85 ° C was then gradually heated up to 220 ° C. The progress of the reaction was monitored by determining the acid number. After reaching an acid number of <3 mg KOH / g still existing cyclohexane was distilled off under vacuum. A viscous resin was obtained.

Condensate amount (water): 34.9 g

Acid value: 2.7 mg KOH / g

Solids content (60 min at 130 ° C): 100.0%

Molecular weight (vapor pressure osmosis):

Mn: 2200 g / mol

Viscosity: 5549 mPas,

(measured at 23 ° C with a rotary viscometer from. Brookfield, type CAP 2000+, spindle 3, shear rate: 1333 s ^"1 ) Production of aqueous basecoats

1 . Preparation of a Comparison Waterborne Basecoat 1

The components listed under "aqueous phase" in Table A were stirred together in the order given to form an aqueous mixture, and in the next step an organic mixture was prepared from the components listed under "organic phase". The organic mixture was added to the aqueous mixture. The mixture was then stirred for 10 minutes and with the aid of deionized water and dimethylethanolamine to a pH of 8 and an injection viscosity of 58 mPas at a shear stress of 1000 s ^-1 , measured with a rotary viscometer (device Rheomat RM 180 from the company Mettler). Toledo) at 23 ° C, adjusted.

Table A: Waterborne basecoat 1

component

parts by weight

Aqueous phase

3% NaMg layered silicate solution 26.2

Deionized water 9.87

Butyl glycol 5.3

Polyester P1 5,6

3% by weight aqueous Rheovis® AS S130 solution;

6.2

Rheology agent, available from BASF, in water

Melamine-formaldehyde resin (Luwipal® 052 from BASF SE) 5,65

10% dimethylethanolamine in water 0.7

Polyurethane-modified polyacrylate; manufactured according to p. 7,

3.9

Z. 55 to p.8, Z. 23 of DE 4437535 A1

Pluriol® P 900 from BASF SE 1, 1

Byk-347® from Altana 0.5

As described above, prepared interpolymer

6.63

Dispersion (MP)

Acrylated polyurethane dispersion (binder dispersion A

4.4 according to WO 91/15528)

Red paste 7,4 Soot paste 6,8

2-ethylhexanol 1

Tributoxyethyl phosphate 1

Paliocrom-Schlämnne 2,25

Mica sludge 3.8

Organic phase

Aluminum pigment, available from Altana-Eckart 0.45

Butyl glycol 0.5

As described above, prepared interpolymer

0.75

Dispersion (MP)

Preparation of the red paste:

The red paste was composed of 40 parts by weight of an acrylated polyurethane dispersion prepared according to International Patent Application WO 91/15528 Binder Dispersion A, 34.5 parts by weight of Cinilex® DPP Red, 2 parts by weight of a commercially available polyether (Pluriol® P900 from BASF SE), 3 parts by weight of 1-propoxy 2-propanol and 20.5 parts by weight of deionized water.

Production of the carbon black paste:

The carbon black paste was composed of 25 parts by weight of an acrylated polyurethane dispersion prepared according to International Patent Application WO 91/15528 Binder Dispersion A, 10 parts by weight of carbon black, 0.1 part by weight of methyl isobutyl ketone, 1, 36 parts by weight of dimethylethanolamine (10% in dem. Water), 2 parts by weight of commercially available polyethers (Pluriol® P900 BASF SE) and 61, 45 parts by weight of deionized water.

Preparation of Paliocrom Sludges:

The Paliocrom slurry was obtained by mixing by means of a stirrer of 0.75 parts by weight of butyl glycol, 0.75 parts by weight of the copolymer dispersion (MP) prepared as described above and 0.75 parts by weight of the commercially available Paliocrom Orange L 2804 from BASF SE. Preparation of Mica sludge:

The mica slurry was prepared by mixing by means of a stirrer of 2 parts by weight of butyl glycol, 1.35 parts by weight of a mixing varnish prepared according to EP 1534792 - B1, column 11, lines 1-17 (without aluminum paste), and 0.45 parts by weight of the commercial mica Mearlin Ext. Super Copper 359Z Merck received.

1 .1 Preparation of a Comparative Waterborne Basecoat 2

The aqueous basecoat material 2 was prepared analogously to Table A, but instead of the polyester P1, the reaction product (R) prepared as described above was used. The conditional by the different solids of the dispersion containing P1 and the resulting reaction product R different amounts of butyl glycol were balanced in the water-based paint 2 by appropriate addition of butyl glycol.

1 .2 Preparation of a water-based paint E1 according to the invention.

The aqueous basecoat E1 was prepared analogously to the comparative aqueous basecoat material 2, but instead of the acrylated polyurethane dispersion (binder dispersion A according to WO 91/15528), a polyurethane resin (X) was used. The preparation of the polyurethane resin (X) depends on WO 92/15405, page 14, line 13 to page 15, line 13. The resin has an acid number of 25 mg KOH / g and a number average molecular weight of 12000 g / mol. The different amounts of water due to the different solids of the binder dispersion A according to WO 91/15528 and the dispersion containing the polyurethane resin (X) were compensated in the water-based paint E1 by correspondingly lower addition of water (see position 2 in Table A).

1 .3 Preparation of a water-based paint E2 according to the invention.

The preparation was carried out analogously to the water-based paint E1, although a different polyurethane resin (X) was used. The preparation of the polyurethane resin used in water-based lacquer E2 depends on WO 92/15405, page 15, lines 23 to 28. The resin has an acid number of 25 mg KOH / g and a number average molecular weight of 5000 g / mol.

1 .4 Preparation of a water-based paint E3 according to the invention.

The preparation was carried out analogously to the water-based paint E1, although a different polyurethane resin (X) was used. The preparation of the polyurethane resin used in aqueous basecoat E3 is governed by WO 92/15405, page 15, lines 16 to 20. The resin has an acid number of 20 mg KOH / g and a number average molecular weight of 1 1000 g / mol.

Comparison between waterborne paints 1, 2 and E1 to E3

To determine the needlestick and number of pinholes, multicoat paint systems were prepared according to the following general procedure:

A 30 x 50 cm sheet steel coated with a surfacer coating was provided with an adhesive strip on one longitudinal edge in order to be able to determine the layer thickness differences after coating. The respective water-based lacquer was applied wedge-shaped electrostatically. The resulting aqueous basecoat film was flashed off at room temperature for one minute and then dried in a convection oven at 70 ° C. for 10 minutes. On the dried aqueous basecoat, a conventional two-component clearcoat was applied in a layer thickness of 35 to 45 micrometers pneumatically. The resulting clearcoat layer was flashed off at room temperature for 20 minutes. Subsequently, the aqueous basecoat film and the clearcoat film were cured in a circulating air oven at 140 ° C for 20 minutes. After the visual evaluation of the pinholes in the resulting wedge-shaped multi-layer coating, the layer thickness of the pinhole limit was determined. The results are shown in Table 1. Table 1: Needle-stitch limit and number of pin-pricks of waterborne basecoats 1, 2 and E1 to E3

WBL Needle stitch limit Needle stitch number

(Microns)

1 10 161

2 21 54 E1 28 31 E2 26 37 E3 25 24

The results substantiate that the use of a coating material according to the invention as basecoat material in the production of multicoat paint systems markedly increases the stability of these multi-layer coatings against pinholes.

Claims

claims

1 . Aqueous coating composition comprising at least one aqueous dispersion containing at least one copolymer (MP), wherein the copolymer (MP) can be prepared by

in which

(a) a water-soluble initiator is used,

(C) the mixture of olefinically unsaturated monomers contains at least one polyunsaturated monomer, at least one linear hydroxy-functional reaction product (R) having an acid number less than 20 mg KOH / g, in its preparation at least one compound (v) containing two functional groups (especially ) and one between the functional groups arranged aliphatic or araliphatic hydrocarbon radical (vb) is used with 12 to 70 carbon atoms, and at least one polyurethane resin (X), in its preparation at least one compound (x.1) containing at least one carboxylic acid group and at least one opposite Isocyanate groups reactive group is used.

2. Coating composition according to claim 1, characterized in that the mixture used in step (ii) of the olefinically unsaturated monomers contains 0.1 to 6.0 mol% of multiply olefinically unsaturated monomers.

3. Coating composition according to claim 1 or 2, characterized in that the mixture used in step (ii) of the olefinically unsaturated monomers contains allyl methacrylate and no further poly olefinically unsaturated monomers are contained.

4. Coating composition according to one of claims 1 to 3, characterized in that the functional groups (v.a) of the at least one compound (v) are selected from the group consisting of hydroxyl groups and carboxyl groups.

5. Coating composition according to one of claims 1 to 4, characterized in that in the preparation of the reaction product (R) dimer fatty acids and / or dimer diols are used as compound (v).

6. Coating composition according to one of claims 1 to 5, characterized in that the reaction product (R) can be prepared by reaction of dinner fatty acids with aliphatic, araliphatic and / or aromatic dihydroxy-functional compounds having a number average molecular weight of 120 to 6000 g / mol, wherein dihydroxy-functional compounds, polyether diols, polyester diols and / or dimer diols can be used.

7. Coating composition according to one of claims 1 to 6, characterized in that the at least one reaction product (R) is selected from the group consisting of

Reaction products can be prepared by reaction of dinner fatty acids with at least one aliphatic dihydroxy-functional compound of the general structural formula (I):

wherein R is a C3 to C6 alkylene radical and n is selected accordingly so that the compound of formula (I) has a number average molecular weight of 120 to 6000 g / mol, the dimer fatty acids and the compounds of formula (I ) are used in a molar ratio of 0.7 / 2.3 to 1, 6/1, 7 and wherein the resulting reaction product has a number average molecular weight of 600 to 40,000 g / mol and an acid value of less than 10 mg KOH / g,

Reaction products can be prepared by reaction of dinner fatty acids with at least one dihydroxy-functional compound of the general structural formula (II):

in which

R is a divalent organic radical comprising 2 to 10 carbon atoms,

R ¹ and R ² independently of one another represent straight-chain or branched alkylene radicals having 2 to 10 carbon atoms,

X and Y independently of one another are O, S or NR ³ , in which R ^{3 is} hydrogen or an alkyl radical having 1 to 6 carbon atoms, and m and n are correspondingly chosen such that the compound of formula (II) has a number average molecular weight of 450 to 2200 g / mol, wherein the components (a) and (b) in a molar ratio of 0.7 / 2.3 to 1, 6/1, 7 are used and the resulting reaction product has a number average molecular weight of 1200 to 5000 g / mol and an acid number of less than 10 mg KOH / g, Reaction products can be prepared by reaction of dinner fatty acids with dimerdiols, the dinner fatty acids and dimer diols being used in a molar ratio of 0.7 / 2.3 to 1.6 / 1, 7 and the resulting reaction product having a number average molecular weight of 1200 to 5000 g / mol and an acid number of less than 10 mg KOH / g.

8. Coating composition according to one of claims 1 to 7, characterized in that for the preparation of the polyurethane resin (X) used at least one compound (x.1) is selected from the group consisting of carboxy-functional polyether polyols containing carboxy-functional polyester polyols and / or monomeric monocarboxylic acids two hydroxyl groups.

9. Coating composition according to one of claims 1 to 8, characterized in that for the preparation of the polyurethane resin (X) in any case at least one alpha, alpha dimethylolalkanoic acid is used as compound (x.1).

10. Coating composition according to claim 9, characterized in that the at least one alpha, alpha dimethylolalkanoic acid is selected from the group consisting of 2,2-dimethylolacetic acid, 2,2-dimethylolpropionic acid, 2,2-dimethylol butyric acid and / or 2,2-dimethylolpentanoic acid ,

1 1. Coating composition according to one of claims 1 to 10, characterized in that in addition at least one of (MP), (R) and (X) different hydroxy-functional polymer as a binder selected from the group consisting of polyurethanes, polyesters, polyacrylates and copolymers of these polymers, a Melamine resin is included as a crosslinking agent and at least one dye and / or effect pigment.

12. A process for producing multicoat paint systems, in which

(1) an aqueous basecoat is applied to a substrate,

(2) a polymer film is formed from the varnish applied in step (1), (3) a clearcoat is applied to the basecoat so obtained and then

(4) the basecoat film is cured together with the clearcoat film, characterized in that the aqueous basecoat used in step (1) is a coating agent according to any one of claims 1 to 11.

13. The method according to claim 12, characterized in that a metallic substrate or a plastic substrate is used as the substrate, wherein the substrate is untreated, pretreated or precoated.

14. Multicoat paint system, produced by a process according to claim 12 or 13.

15. Use of a coating composition according to any one of claims 1 to 1 1 for improving the stability of multi-layer coatings against optical defects.