EP1149137A1

EP1149137A1 - Aqueous coating agent consisting of two constituents and use thereof in multi-layer enamels

Info

Publication number: EP1149137A1
Application number: EP99948851A
Authority: EP
Inventors: Armin Göbel; Bettina Vogt-Birnbrich; Jörg-Peter ZÖLLNER
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1998-10-26
Filing date: 1999-09-24
Publication date: 2001-10-31
Also published as: DE19849208A1; WO2000024835A1; DE19849208C2

Abstract

An aqueous coating agent consisting of one or several water-dilutable hydroxy functional polyurethane urea paste resins containing 10-30 mmol urea groups (calculated asHCONH-), 20-300 mmol urethane groups (calculated asHCOO)espectively per 100 g of solid resin, with a hydroxyl value of 20-250, an acid value of 15-80 and a molar mass Mn of 1000-20000 g/mol, obtained in the following manner: I) production of a polyurethane prepolymer containing NCO groups by reacting a1) hydroxy functional compounds with a molar mass Mn of 360-8000 g/mol with a2) polyisocyanates and a3) compounds with at least one group that can react with isocyanate and at least one ionic group, II) subsequent reaction of the polyurethane prepolymer with a4) hydrdroxy functional monoamines in addition to, optionally, polyols and III) neutralization of groups that can be transformed into ionic groups, in addition to one or several polyisocyanates, and optionally pigments, filling materials, organic solvents and/or usual additives for enamels.

Description

Aqueous two-component coating agent and its use in multi-layer painting

The invention relates to aqueous two-component (2K) coating compositions based on water-dilutable polyurethane resins and polyisocyanates, which are particularly suitable for the production of filler and / or primer layers in a multi-layer structure. The coating compositions can be used in particular in vehicle and industrial painting, in particular in vehicle refinishing, for coating plastic and metal substrates.

Multi-layer vehicle refinishing generally consists of a filler layer applied to optionally precoated substrates and one

Top coat consisting of a color and / or effect basecoat and a transparent clearcoat. However, the top coat can also be created from a pigmented single-layer top coat.

For ecological reasons, efforts are also being made to reduce the solvent emissions of the coating agents in vehicle refinishing. For example, aqueous or so-called high-solid coating agents have already been developed for almost all paint layers. For example, two-component aqueous systems based on hydroxy-functional binders and polyisocyanate hardeners and on the basis of epoxy / polyamine systems are known for use as fillers.

However, the coatings obtained with these varnishes do not yet correspond in all points to the level of properties of conventional solvent-based fillers.

WO-A-9403511 describes aqueous coating compositions based on hydroxy-functional polyurethane resins and polyisocyanates which can be used as fillers. The hydroxy-functional polyurethane resins are produced from a precursor product containing NCO groups, formed from compounds with a Acid group, and two groups reactive with isocyanate and diisocyanates, and an optionally fatty acid-modified polyester polyol in excess. Filler coating compositions produced on the basis of these binders, however, still show considerable weaknesses in terms of sandability and, at higher layer thicknesses, for example 110 to 140 μm, bubble-free application is not guaranteed.

EP-A-0 355 682 describes water-dilutable polyurethane resins which can be used in filler coating compositions and are produced from polyisocyanates, polyols with a molecular weight Mn of at least 400, compounds with two groups which are reactive toward isocyanate and one capable of forming anions

Group and compounds which are monofunctional or contain active hydrogen of different reactivity, the last-mentioned building blocks each being located at the chain end of the polyurethane resin, and / or compounds which contain at least two groups reactive with NCO groups and serve as chain extenders. Can be used as crosslinkers in the filler coatings

Melamine resins or blocked polyisocyanates may be included. The curing temperatures of these filler coatings are between 150 and 170 ° C.

Furthermore, from EP-A-469 389 aqueous two-component polyurethane coating compositions are known which contain water-thinnable hydroxy-functional polyurethane resins with a total urethane and urea content of 9 to 20% by weight, based on the weight of the polyurethane, and contain water-dispersible polyisocyanates. The coating compositions can additionally contain, as the third component, up to 20% by weight of a polyol with a molecular weight of 62 to 1000, preferably of 62 to 250, which may optionally have polyether groups. The coating compositions are preferably used as clear lacquers.

Fillers formulated from these coating materials have inadequate sandability and short pot lives. It also comes with the

Application in higher layer thicknesses for blistering, which significantly affects the surface quality. It was therefore an object of the invention to provide suitable aqueous coating compositions for the production of filler layers in a multi-layer structure, which have a sufficient pot life and also guarantee perfect bubble-free application in higher layer thicknesses. The coating compositions are said to produce coatings with a very good surface quality and very good sandability both in the dry and in the wet state. Good pigment and filler wetting should also be ensured. A good top coat level should be achieved when painting over.

The object is achieved by two-component coating compositions containing

A) one or more water-dilutable hydroxy functional

Polyurethane urea resins with a urea group content (calculated as -NHCONH-) from 10 to 300 mmol in 100 g solid resin, preferably from 20 to

250 mmol in 100 g solid resin, a urethane group content (calculated as -NHCOO-) of 20 to 300 mmol in 100 g solid resin, preferably from 80 to 250 mmol in 100 g solid resin, an OH number of 20 to 250, preferably 40 to 200 , particularly preferably from 60 to 150, an acid number from 15 to 80, preferably from 18 to 65 and a number-average molar mass Mn from 1000 to 20,000 g / mol, preferably from 1,500 to 15,000 g / mol, which are obtainable from

I) Preparation of a polyurethane prepolymer containing NCO groups by

implementation

al) one or more hydroxy-functional compounds with a number average molecular weight (Mn) of 360 to 8000 g / mol, preferably 500 to

5000 g / mol, with

a2) one or more polyisocyanates and

a3) at least one compound with at least one isocyanate-reactive Group and at least one ionic group or one capable of ion formation,

II) Subsequent reaction of the polyurethane prepolymer containing NCO groups with

a4) one or more hydroxyl-functional monoamines and optionally with one or more polyols, in proportions such that the resulting polyurethane has the desired hydroxyl numbers and urea and urethane groups,

III) at least partially neutralizing the ionic groups or the groups of the polyurethane obtained which can be converted into ionic groups before or after the reaction in stage II and transfer of the reaction product obtained into the aqueous phase,

B) one or more polyisocyanates and

optionally pigments, fillers, water, organic solvents and / or additives customary in paint.

The water-thinnable hydroxy-functional polyurethane urea resins present as component A) in the coating compositions of the invention and their preparation are described below.

To produce the water-dilutable polyurethane urea resins, an NCO-functional polyurethane prepolymer is first prepared in a first step (I). The polyurethane prepolymer is obtained by reacting components a1 to a3).

In component al) for the production of the NCO-functional

Polyurethane prepolymers are hydroxy-functional linear or branched compounds which preferably have an OH functionality of 2 to 3, particularly preferably from 2, have an OH number from 50 to 250 and a number-average molar mass (Mn) from 360 to 8000 g / mol, preferably from 500 to 5000 g / mol.

Polyester polyols, polycarbonate polyols,

Polyether polyols, polylactone polyols and / or poly (meth) acrylate polyols or the corresponding diols. The polyols and diols can each be used individually or in combination with one another.

Preferred component a1) are polyester polyols, e.g. Polyester diols used. These are particularly preferably linear polyester polyols, in particular linear polyester diols. The polyester polyols preferably have an acid number of <3 mg KOH / g, particularly preferably <1 mg KOH / g.

The polyester polyols can be prepared in a conventional manner known to the person skilled in the art, for example by polycondensation from organic dicarboxylic acids or their anhydrides and organic polyols. The dicarboxylic acids and the polyols can be aliphatic, cycloaliphatic or aromatic in nature.

The acid component for the production of the polyester polyols is preferably low molecular weight dicarboxylic acids or their anhydrides with 2 to 17, preferably less than 16, particularly preferably less than 14 carbon atoms in the molecule. Suitable dicarboxylic acids are, for example, phthalic acid, isophthalic acid, alkyl isophthalic acid, terephthalic acid, hexahydrophthalic acid, adipic acid, trimethyladipic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid,

Glutaric acid, succinic acid, itaconic acid and 1,4-cyclohexanedicarboxylic acid. The corresponding anhydrides, if they exist, can also be used instead of the acids. To achieve branches, proportions of higher functional carboxylic acids can also be added, e.g. trifunctional carboxylic acids such as trimellitic acid, malic acid and dimethylolpropionic acid.

Polyols which can be used to prepare the polyester polyols are preferably diols, for example glycols such as ethylene glycol, 1,2-propanediol, 1,2-butanediol, 1,3 and -1,4, 1,2-propanediol 2, 3, 1,6-hexanediol, 1,2-cyclohexanediol and -1, 4, hydrogenated bisphenol A and neopentyl glycol.

The diols can optionally be modified by small amounts of higher alcohols.

Examples of higher alcohols which can be used are trimefhylolpropane, pentaerythritol, glycerol and hexanetriol. Proportionate chain-terminating monohydric alcohols, for example those having 1 to 18 carbon atoms in the molecule, such as

Propanol, butanol, cyclohexanol, n-hexanol, benzyl alcohol, isodecanol and saturated and unsaturated fatty alcohols can be used.

The components are reacted in such proportions that the desired OH numbers of the polyester polyols are obtained.

The polyester polyols are preferably essentially free of carboxyl groups. For example, they can have acid numbers of <3, preferably <1. However, it is also possible for the polyester polyols to contain carboxyl groups, for example they can then have acid numbers of 5 to 50 mg KOH / g. The carboxyl groups can, for example, via di- or trifunctional carboxylic acids, e.g. Trimellitic acid, malic acid and dihydroxymonocarboxylic acids such as e.g. Dimethylolpropionic acid are introduced.

The polyester polyols can be used individually or in combination with one another.

Also preferred as component a1) are polycarbonate polyols and in particular polycarbonate diols.

The polycarbonate polylenes are esters of carbonic acid which are formed by the reaction of carbonic acid derivatives, for example diphenyl carbonate or phosgene Polyols, preferably diols, can be obtained. Examples of suitable diols are ethylene glycol, 1,2-and 1,3-propanediol, 1,4 and 1,3-butanediol, 1,6-hexanediol, neopentyl glycol, 2-methyl-1,3-propanediol and 1,4 -Bishydroxymethylcyclohexane in question.

The polycarbonate polyols can be used individually or in combination with one another.

Polyether and / or polylactone polyols are also very suitable as component a1).

Examples of suitable polyether polyols are polyether polyols of the following general formula:

H [ÖT- (CHR _m OH,

in which R ^{4 is} hydrogen or a lower alkyl radical (for example C ₁ to C ₆ ), optionally with different substituents, n = 2 to 6 and m = 10 to 50. The radicals R ⁴ can be the same or different. Examples of polyether polyols are poly (oxytetramethylene) glycols, poly (oxyethylene) glycols and

Poly (oxypropylene) glycols or mixed block copolymers containing different oxytetramethylene, oxyethylene and / or oxypropylene units.

The polyether polyols can be used individually or in combination with one another.

The polylactone polyols are polyols, preferably diols, which are derived from lactones, preferably caprolactones. These products are obtained, for example, by reacting an epsilon caprolactone with a diol. The polylactone polyols are characterized by recurring polyester components, which are derived from the lactone. These recurring molecular parts can correspond, for example, to the following general formula: O

C - (CHR ⁵ ) _n CH, O

where n is preferably 4 to 6 and R ^{5 is} hydrogen, an alkyl radical is a cycloalkyl radical or an alkoxy radical and the total number of carbon atoms in the substituents of the lactone ring 12 does not exceed. Lactones which are preferably used are the epsilon-caprolactones in which n has the value 4. Unsubstituted epsilon-caprolactone is particularly preferred. The lactones can be used individually or in combination.

Diols suitable for the reaction with the lactones are e.g. Ethylene glycol, 1,3-propanediol, 1,4-butanediol and dimethylolcyclohexane.

The polylactone polyols can be used individually or in combination with one another.

Poly (meth) acrylate polyols can also be used as component a1). The poly (meth) acrylate polyols are free-radical polymerization polymers made from hydroxy-functional polymers

(Meth) acrylic acid esters and other radically polymerizable unsaturated monomers. Poly (meth) acrylate polyols which have a selective structure with terminal OH groups due to the special production process can preferably be used. The poly (meth) acrylate polyols can also be used individually or in combination with one another.

In addition, one or more low molecular weight polyhydric alcohols, preferably difunctional alcohols with a molar mass of 62 to 356 g / mol, can optionally also be used in component a1). Examples include ethylene glycol, 1,2-propanediol and 1,3, butanediol 1,3 and 1,4, 1,6-hexanediol,

Octanediol-1,8, cyclohexanediol-1, 2 and -1, 4, dimethylolpropane, neopentyl glycol, cyclohexanedimethanol and hydroxyethylated or hydroxypropylated bisphenol A or bisphenol F.

Any organic polyisocyanates, preferably diisocyanates, can be used individually or in combination as component a2) for the preparation of the NCO-functional prepolymers. The polyisocyanates can e.g. be aromatic, aliphatic and / or cycloaliphatic in nature. These can also be diisocyanates containing ether or ester groups. Examples of suitable diisocyanates are trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, propylene diisocyanate, ethylene diisocyanate, 2,3-dimethylethylene diisocyanate, 1-methyltrimethylene diisocyanate,

1,3-cyclopentylene diisocyanate, 1,4-cyclohexylene diisocyanate, 1,2-cyclohexylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, l-isocyanatomethyl 5-isocyanato-1,3,3-trimethylcyclohexane, bis (4-isocyanato-phenyl) methane, norbornene diisocyanate, 4,4-diisocyanatodiphenyl ether, 1,5-dibutylpentamethylene diisocyanate, 2,3-bis (8- isocyanatooctyl) -4-octyl-5-hexylcyclohexane, 3-isocyanatomethyl-1-methylcyclohexyl isocyanate, and / or 2,6-diisocyanatomethyl capronate.

It is also possible to use non-yellowing and / or sterically hindered isocyanates having 4 to 25, preferably 6 to 16, carbon atoms which are in the alpha position

NCO group contain one or two linear, branched or cyclic alkyl groups with 1 to 12, preferably 1 to 4 carbon atoms as substituents on the basic structure. The basic structure can consist of an aromatic or alicyclic ring or of an aliphatic linear or branched carbon chain with 1 to 12 carbon atoms. Examples include isophorone diisocyanate, bis (4-isocyanatocyclohexyl) methane,

1, 1, 6,6-tetramethyl-hexamethylene diisocyanate, 1, 5-dibutyl-pentamethylene diisocyanate, 3-isocyanatomethyl-l-methyl-cyclohexyl-isocyanate, p- and m-tetramethylxylylene diisocyanate and / or the corresponding hydrogenated homologues.

Component a3) for the preparation of the NCO-functional prepolymers are preferably low-molecular compounds which have at least one, preferably more than one, particularly preferably two, reactive with isocyanate groups Have groups and at least one ionic group or capable of ion formation. These connections can either be used to break the chain or they are built into the chain. Suitable groups for anion formation are, for example, carboxyl, phosphoric acid and sulfonic acid groups. Groups capable of forming cations are, for example, primary, secondary and tertiary amino groups or onium groups, such as quaternary ammonium, phosphonium and / or tertiary sulfonium groups. Anionic groups or those capable of forming anions are preferred. Preferred anionic groups are carboxyl groups.

Suitable groups that are reactive with isocyanate are, in particular, hydroxyl groups and primary and / or secondary amino groups.

Preferred compounds suitable as component a3) are those which contain carboxyl and hydroxyl groups. Examples of such connections are

Hydroxyalkanecarboxylic acids of the following general formula:

(HO) _χ Q (COOH) _y

wherein

Q represents a straight or branched hydrocarbon radical with 1 to 12 carbon atoms and x and y each represent 1 to 3. Examples include citric acid and tartaric acid. Carboxylic acids with x = 2 and y = 1 are preferred.

A preferred group of dihydroxyalkanoic acids are alpha, alpha

Dimethylolalkanoic acids.

Alpha, alpha-dimethylolpropionic acid and alpha, alpha-dimethylolbutyric acid are preferred.

Further examples of usable dihydroxyalkanoic acids are dihydroxypropionic acid, dimethylolacetic acid, dihydroxysuccinic acid or Dihydroxybenzoic acid.

Other compounds which can be used as component a3) are amino group-containing acids, for example alpha, alpha-diamino-valeric acid, 3,4-diaminobenzoic acid, 2,4-diamino-toluenesulfonic acid and 4,4-diamino-di-phenyl ether sulfonic acid and

Dihydroxy compounds which contain a tertiary and / or quaternary amino group, such as, for example, N-methyldiefhanolamine, N-methyldiisopropanol and 2-N, N-dimethylamino-2-ethyl-1,3-propanediol.

The reaction of components a1), a2) and a3) with one another is carried out in a conventional manner known to the person skilled in the art, for example at temperatures from 50 to 120 ° C., preferably 70 to 100 ° C., if appropriate using catalysts.

Components a1), a2) and a3) are used in amounts such that a reaction product with free isocyanate groups is formed, i.e. it will be with one

Excess poly isocyanate worked. For example, an equivalent ratio of NCO groups: OH groups of 1.1: 1 to 2.0: 1, preferably 1.2: 1 to 1.9: 1 can be used.

The polyurethane prepolymer obtained in stage I and containing NCO groups is then reacted in a further stage II) with component a4) and thus converted into a urea group-containing and hydroxy-functional polyurethane. Component a4) is one or more hydroxy-functional monoamines, each with a primary or secondary amino group. The hydroxy-functional monoamines can optionally be used together with one or more polyols. The reaction takes place with complete consumption of the amino groups. The monoamines which can be used can contain one or preferably more hydroxyl groups. For example, it can be alkanolamines, dialkanolamines, alkylalkanolamines and / or arylalkanolamines with at least 2 and not more than 18 carbon atoms in the alkanol, alkyl and aryl radical. Examples of usable monoamines with a hydroxyl group are monoethanolamine, N-methylethanolamine, 3-amino-l-propanol, 2-amino-2- methylpropanol, 3-amino-2,2-dimethylpropanol-l, 2-amino-2-ethyl-l, 3-propanediol, N-phenylmethanolamine and N-cyclohexylethanolamine. Examples of monoamines with two or more hydroxyl groups are diethanolamine, diisopropanolamine, 2-amino-2-hydroxymethylpropane-1, 3-diol.

The hydroxyamines and any polyols present (component a4) are used in such an amount that OH numbers from 20 to 250, preferably from 40 to 200, particularly preferably from 60 to 150 and urea group contents from 10 to 300 are preferred in the reaction product obtained 20 to 250 mmol in 100 g of solid resin result. Here, complete conversion is aimed for with a practically equivalent molar ratio between the reactive amino group and the isocyanate group. If necessary, a very small excess of NCO can be used. The equivalent ratio of NCO groups to amino groups should be less than 1.05: 1, but is preferably 1: 1.

The reaction takes place, for example, at temperatures from 30 to 80 ° C., preferably 30 to 50 ° C.

The polyols which can optionally be used in addition to the hydroxyamines can be used to introduce hydroxyl groups into the polyurethane. They are preferably low molecular weight alcohols with 2 or more hydroxyl groups. Examples include neopentyl glycol, trimethylol propane, pentaerythritol, dipentaerythritol, glycerin, hydroxypivalic acid neopentyl glycol ester, 2-ethyl-2-methyl-propanediol-1,3, hexanediol-1,6, cyclohexanedimethanol and ditrimethylol propane.

By reacting the NCO-functional polyurethane prepolymer with the amino alcohols and, if appropriate, further polyols, a polyurethane urea resin with the urea and urethane group contents already mentioned, molar masses and OH numbers is obtained. The

Polyurethane urea resins have acid numbers from 15 to 80, preferably from 18 to 65, particularly preferably 19 to 45. However, it is also possible to introduce a proportion of cationic groups into the polyurethane urea resin in addition to the anionic groups. The cationic groups should only be present in a proportion, based on the anionic groups. The cationic ones are preferred

Groups around tertiary and / or quaternary amino groups. For example, 0.05 to 25%, preferably 0.1 to 10%, of cationic groups, based on equivalents of anionic groups, can be present. Additional cationic groups can be introduced, for example, by reacting the NCO prepolymer with compounds having at least one hydroxyl group and one tertiary or quaternary amino group. For example, the procedure can be such that the compounds mentioned having tertiary and / or quaternary amino groups are reacted together with the amino alcohols with the NCO prepolymer. Examples of compounds having at least one hydroxyl group and one tertiary or quaternary amino group are N-methyldiethanolamine, N-

Methyl diisopropanol and 2-N, N-dimethylamino-2-ethyl-1,3-propanediol.

In order to achieve sufficient water dilutability, the ionic or groups of the polyurethane urea resin which can be converted into ionic groups are at least partially neutralized in a further stage III. The neutralization can take place before or after the reaction with the hydroxy amines. The polyurethane resins preferably contain anionic groups. The anionic groups are neutralized with bases. Preferred examples of basic neutralizing agents are tertiary amines such as trimethylamine, triethylamine, dimethylethylamine, dimethylbutylamine, N-methylmorpholine, dimethylethanolamine and dimethylisopropanolamine.

Isocyanate group-free polyurethane urea resins can also be neutralized with amines containing isocyanate group reactive groups, e.g. with primary or secondary amines or amino alcohols.

After neutralization, the polyurethane resin is transferred to the aqueous phase.

However, neutralization and transfer into the aqueous phase can also take place simultaneously. The polyurethane urea resin is in a colloidal state in the aqueous phase and exhibits a pseudoplastic behavior. The latter means that the viscosity decreases with increasing speed gradient. The viscosity of the polyurethane urea dispersion, measured at a speed gradient of 231 s and a solids content of 35% by weight, is 0.5 to 10 Pas. The degree of neutralization is preferably 60 to 120%, particularly preferably 70 to 100%. The aqueous resin dispersion has a solids content of preferably 25 to 50% by weight, particularly preferably 28 to 42% by weight.

The particle size of the polyurethane urea resin in the aqueous phase is preferably in the range from 25 to 200 nm, preferably from 30 to 100 nm.

The aqueous polyurethane urea dispersion can preferably have the following composition, for example:

20 to 50 parts by weight of the polyurethane urea resin

0.3 to 18 parts by weight of neutralizing agent, preferably ammonia and / or

Amine 4 to 25 parts by weight of one or more at least partially water-miscible organic solvents and 15 to 75 parts by weight of water.

If necessary, the water-thinnable hydroxy-functional polyurethane resins can also be used in combination with other water-thinnable hydrooxy functional resins. These can be, for example, customary water-dilutable hydroxy-functional poly (meth) acrylate, polyester and, optionally, modified polyurethane resins which are different from component A).

One embodiment of the invention consists in the water-thinnable hydroxy-functional polyurethane resins defined above Binder composition in combination with polyether polyols with a number average molecular weight (Mn) of 400 to 5000, preferably 500 to 3000 g / mol. For example, this binder composition can then be 2.0 to 25% by weight, preferably 3.0 to 20% by weight, particularly preferably 4 to 15% by weight, of the polyether polyols, based on the solids content of the polyols used

Amount of polyurethane resin included.

Examples of suitable polyether polyols are poly (oxytetramethylene) glycols, poly (oxyethylene) glycols and poly (oxypropylene) glycols or mixed block copolymers which contain different oxytetramethylene, oxyethylene and / or

Contain oxypropylene units. Preferred are polyether polyols which are used without the use of ethylene oxide, i.e. can be obtained in particular using only propylene oxide or tetrahydrofuran. The use of polyoxypropylene glycols with molar masses of 500 to 3000 g / mol is particularly preferred. Different polyether polyols can be combined.

This binder composition can be produced from polyurethane resin and polyether polyols by mixing the two components. This can be done in different ways. Thus it is possible to add the polyether polyols to the water-dilutable polyurethane resin before, during or after the emulsion formation, i.e. before, during or after the transfer of the water-dilutable polyurethane resin into the aqueous phase. The procedure can preferably be such that the polyether polyols are admixed with the water-dilutable polyurethane resin before being converted into the aqueous phase. If the addition of

Polyether polyols before the conversion into the aqueous phase can also be carried out in such a way that the polyether polyols are already added to the NCO prepolymer together with the hydroxy-functional monoamines. The reaction conditions for reacting the NCO prepolymer with the hydroxy-functional monoamines are chosen in a manner familiar to the person skilled in the art so that the NCO groups react only with the amino groups. The coating compositions of the invention contain one or more polyisocyanates as component B). Conventional polyisocyanates are suitable as crosslinking agents, for example any organic polyisocyanates with aliphatic, cycloaliphatic, araliphatic and / or aromatically bound free isocyanate groups. They are liquid at room temperature or liquefied by the addition of organic solvents. The

At 23 ° C, polyisocyanates generally have a viscosity of 1 to 6000 mPas, preferably above 5 and below 3000 mPas. Such polyisocyanates are well known and e.g. described in DE-A 38 29 587 or DE-A 42 26 243.

The polyisocyanates are preferably polyisocyanates or

Polyisocyanate mixtures with exclusively aliphatic and / or cycloaliphatic isocyanate groups with an average NCO functionality of 1.5 to 5, preferably 2 to 3.

Particularly suitable are, for example, “paint polyisocyanates” based on hexamethylene diisocyanate (HDI), 1-isocyanato-3, 3, 5-trimethyl-5-isocyte anatomethylcyclohexane (IPDI) and / or bis (isocyanatocyclohexyl) - methane and the known biuret, AUophanat, urethane and / or isocyanurate groups derivatives of these diisocyanates. Triisocyanates such as nonanetriisocyanate can also be used. Sterically hindered are also very suitable

Polyisocyanates. Examples include 1, 1,6,6-tetramethyl-hexamethylene diisocyanate, 1,5-dibutyl-penta-methyl diisocyanate, p- or m-tetramethylxylylene diisocyanate and the corresponding hydrogenated homologues. These diisocyanates can also be converted in a suitable manner to give more highly functional compounds, for example by trimerization or by reaction with water or

Trimethylol propane.

The polyisocyanate crosslinkers can be used individually or in a mixture. These are the polyisocyanate crosslinkers customary in the coatings industry, which have been extensively described in the literature and are also available as commercial products. Components A) and B) are used in proportions such that the equivalent ratio of hydroxyl groups of component A) to isocyanate groups of component B) is preferably 4: 1 to 1: 4, particularly preferably 1.5: 1 to 1: 1, 5 is.

The coating compositions according to the invention can contain pigments and / or fillers. The pigments can be color and / or effect pigments. All paint-typical pigments of organic or inorganic nature are suitable as color pigments. Examples of inorganic or organic color pigments are titanium dioxide, micronized titanium dioxide, iron oxide pigments, carbon black,

Azo pigments, phthalocyanine pigments, quinacridone or pyrrolopyrrole pigments. Examples of effect pigments, but which are not typical for filler formulations, are metal pigments, e.g. made of aluminum, copper or other metals; Interference pigments, e.g. metal oxide coated metal pigments, e.g. Titanium dioxide coated or mixed oxide coated aluminum, coated

Mica, e.g. titanium dioxide coated mica and graphite effect pigments. Corrosion protection pigments, e.g. Zinc phosphate.

Fillers may also be present in the coating compositions. These are the usual fillers that can be used in the paint industry. examples for

Fillers are silicon dioxide, aluminum silicate, barium sulfate, calcium carbonate and talc.

The coating compositions according to the invention can furthermore contain water and small amounts of organic solvents and conventional paint additives.

The organic solvents which may be present in the coating compositions are customary paint solvents. These can originate from the production of the binders or are added separately. They are preferably water-miscible solvents. Examples of suitable solvents are monohydric or polyhydric alcohols, for example propanol, butanol, hexanol; Glycol ether or ester, for example diethylene glycol dialkyl ether, dipropylene glycol dialkyl ether, each with Cl- bis C6 alkyl, ethoxy propanol, butyl glycol; Glycols, for example ethylene glycol, propylene glycol and their oligomers, N-methylpyrrolidone and ketones, for example methyl ethyl ketone, acetone, cyclohexanone; aromatic or aliphatic hydrocarbons, for example toluene, xylene or linear or branched aliphatic C6-C12 hydrocarbons. In proportion, the organic solvents are, for example, up to a maximum of 15

% By weight, preferably up to 10% by weight, based on the total coating composition.

The coating compositions according to the invention can furthermore contain customary paint additives. Examples of customary paint additives are leveling agents, rheology-influencing agents, such as highly disperse silica or polymeric urea compounds, thickeners, such as crosslinked polycarboxylic acid or polyurethanes, defoamers, wetting agents, anti-cratering agents and hardening accelerators. The additives are used in customary amounts known to the person skilled in the art.

The coating compositions of the invention can be produced in a conventional manner. For example, the pigments and / or fillers can be dispersed in the polyurethane component (component A). However, it is also possible to carry out the dispersion with an additional network resin. Since it is a two-component coating agent (two-component coating agent), the mutually reactive binder components A) and B) must be stored separately and can only be mixed with one another shortly before application.

Generally, water or organic can be used before application

Solvents are still adjusted to spray viscosity.

The coating compositions according to the invention are particularly suitable for producing filler and / or primer layers of an air-drying or forced-drying, e.g. up to 80 ° C, preferably up to 60 ° C drying, multi-layer coating.

However, they can also be hardened at higher temperatures of, for example, 80 to 140 ° C. The invention therefore also relates to the use of the coating compositions for the production of multilayer coatings, in particular the filler and / or primer layers of multilayer coatings being created by the coating compositions according to the invention.

The preferred area of application of the coating compositions according to the invention is vehicle and vehicle parts painting. Depending on the curing conditions, the coating agents are both for vehicle refinishing (curing temperatures of, for example, 20 to 80 ° C.) and for

Vehicle series painting (curing temperatures of, for example, 100 to 140 ° C) applicable. However, other industrial applications are also possible.

The coating compositions are applied by customary methods, preferably by spray application.

Suitable substrates are metal and plastic substrates, in particular the substrates known in the automotive industry, such as Iron, zinc, aluminum, magnesium, stainless steel or their alloys, as well as polyurethanes, polycarbonates or polyolefins. The filler layers can optionally be pretreated

Substrates are applied as such or on conventional primers. They adhere well to a wide variety of substrates such as bright steel sheet, sanded, polyvinyibutyral primer, 2K epoxy primers, sanded factory or old paintwork. After drying and optionally grinding, the coating compositions according to the invention can be overcoated with conventional top coats without any problems. These can be single-layer topcoats, e.g. act on 2K acrylate / polyisocyanate basis or conventional basecoat / clearcoat structures. It can be painted over with solvent-based or water-based coating agents. The coating compositions according to the invention can, for example, be used over a long period, e.g. within 18 hours (overnight) at

Dried at room temperature. However, you can also, if necessary after a flash-off time of about 10 to 30 minutes, dry at higher temperatures Temperatures, for example for 20 to 50 minutes at 40 to 60 ° C, for example.

The coating compositions of the invention have sufficient processing times of at least 120 minutes. The coating compositions can in particular as

Filler coating agents can be applied in layers up to 140 μm without bubbles. After the curing process, homogeneously coated substrates with smooth, trouble-free surfaces are obtained. The covers show no pinpricks. After a short drying time, the covers can be sanded wet and dry without any problems. In particular, the good dry sandability in comparison to known binder systems is to be emphasized. There is no rapid clogging of the sanding paper.

When overpainting with conventional topcoats, a very good topcoat level is achieved with the filler coating compositions according to the invention.

The invention is illustrated by the following examples.

1st example

Production of polyurethane urea dispersions

Positions 1-3 are weighed into a 21-flask with stirrer and thermometer, heated to 80 ° C under protective gas and held until the dimethylolpropionic acid is completely dissolved. It is cooled to 50 ° C., position 4 is added and the mixture is heated again to 80 ° C. The batch is kept at 80 ° C. until the isocyanate number (based on solution) is 4.2 to 4.5%. Then it is cooled to approx. 40 ° C and positions 5 and 6 are added together (exothermic

Reaction). After an hour at 80 ° C, the isocyanate number is less than 0.1%. Then position 7 is added at 80 ° C. After 15 minutes, the mixture is diluted with position 8, adjusted to a solids content of approx. 35% and stirred homogeneously at 50 ° C. for one hour. Positions 1 to 8 for two polyurethane dispersions are given below. Wt. are parts by weight.

Demineralized water: Deionized or deionized water produced by distillation or with the help of ion exchangers.

Polyurethane dispersion 1:

1. 16.16 parts by weight commercial polytetrahydrofuran with OHZ 115 mg KOH / g

2.2, 11 parts by weight Dimethylolpropionic acid 3. 5.85 parts by weight N-methylpyrrolidone

4. 11, 10 parts by weight of isophorone diisocyanate

5. 3.70 parts by weight Diethanolamine

6. 3.70 parts by weight Butoxyethanol

7. 2.02 parts by weight a 1: 1 mixture of dimethylethanolamine and demineralized water

8. 55.36 parts by weight. VE water

Final values:

Solids (30 min, 150 ° C): 35.1% in N-methylpyrrolidone / butoxyethanol / demineralized water

Acid number: 25.9

MEQ (amine): 34.4 (milliequivalents of amine based on 100 g solid resin)

Degree of neutralization: 74.5%

OH number: 120 viscosity (measured at 25 ° C with a rotary measuring device at a

Speed gradient of 231 s ^"1 ): 1.168 Pas

Urea group content: 100 mmol in 100 g solid resin

Urethane group content: 185 mmol in 100 g solid resin

Polyurethane dispersion 2:

1. 15.84 parts by weight commercial polycarbonate diol with OHZ 115 mg KOH / g

2. 2, 14 parts by weight Dimethylol propionic acid 3. 5.74 parts by weight N-methylpyrrolidone

4. 10.97 parts by weight of isophorone diisocyanate

5. 3.62 parts by weight. Diefhanolamine

6. 2.45 parts by weight Polypropylene glycol with molecular weight 900 7. 2.18 parts by weight. a 1: 1 mixture of dimethylethanolamine and demineralized water

8. 57.06 parts by weight VE water

Final values:

Solids (30 min, 150 ° C): 35% in N-methylpyrrolidone / butoxyethanol / demineralized water Acid number: 26

MEQ (amine): 34.4

Degree of neutralization: 74%

OH number: 120

Viscosity (measured at 25 ° C with a rotation measuring device at a speed gradient of 231 s ^"1 ): 1.090 Pas

Urea group content: 99 mmol in 100 g solid resin

Urethane group content: 183 mmol in 100 g solid resin

2. Example production of filler coatings

Filler was prepared in the usual way from the following ingredients by mixing and dispersing:

Filler 1:

31.0% by weight of a polyurethane dispersion from Example 1 13.6% by weight of fully demineralized water

0.1% by weight of dimethylethanolamine 0.8% by weight of a commercially available dispersant

0.1% by weight of a commercially available anti-corrosion agent (inhibitor Ll)

0.7% by weight of fumed silica 0.7% by weight iron oxide yellow

4.0% by weight quartz flour 14.8% by weight kaolin 16.4% by weight titanium dioxide 17.8% by weight heavy spar

Filler 2:

The components correspond to those from filler 1 with the difference that 31% by weight of the polyurethane dispersion 2 were used as the binder component.

Shortly before the application, a commercially available polyisocyanate crosslinker based on HDI trimer was added in such an amount that the equivalent ratio of hydroxyl groups of the polyurethane resin to isocyanate groups of the crosslinker was 1: 1.

The filler coating compositions thus obtained were applied to metal substrates precoated with customary primers in a resulting dry layer thickness of approximately 60 μm. Curing took place at 60 ° C for 30 minutes. The coatings could be sanded dry very well. It was then overpainted with a pigmented, solvent-based two-pack topcoat (based on polyhydroxyacrylate resin / polyisocyanate) and cured at 60 ^° C. for 30 minutes.

The multilayer structure showed a very good topcoat level.

Claims

Claims:

1. Aqueous two-component coating composition containing

A) one or more water-dilutable hydroxy functional

Polyurethane urea resins with a urea group content (calculated as -NHCONH-) of 10 to 300 mmol in 100 g solid resin, one

Urethane group content (calculated as -NHCOO-) of 20 to 300 mmol in 100 g of solid resin, an OH number of 20 to 250 and a number-average molar mass Mn of 1000 to 20,000 g / mol, which are obtainable from

I) Preparation of a polyurethane prepolymer containing NCO groups by reaction

al) one or more hydroxy-functional compounds with a number-average molar mass Mn of 360 to 8000 g / mol, with

a2) one or more polyisocyanates and

a4) one or more hydroxy-functional monoamines and optionally with one or more polyols, in such Proportions that the resulting polyurethane has the desired hydroxyl numbers and urea and urethane groups,

B) one or more polyisocyanates and

2. Coating composition according to claim 1, characterized in that as component A) one or more water-dilutable hydroxy functional

Polyurethane urea resins with a urea group content (calculated as -NHCONH-) from 20 to 250 mmol in 100 g solid resin, a urethane group content (calculated as -NHCOO-) from 80 to 250 mmol in 100 g solid resin, an acid number from 15 to 80, an OH- Number from 40 to 200 and a number average molecular weight Mn from 1500 to 15000 g / mol are included.

3. Coating composition according to claim 1 or 2, characterized in that component al) is a hydroxy-functional linear or branched compound with an OH functionality of 2 to 3, an OH number of 50 to 250 and a number-average molar mass Mn of 300 to 8000 g / mol.

4. Coating composition according to claim 1, 2 or 3, characterized in that as component al) polyester polyols, polycarbonate polyols, polyether polyols, polylactone polyols and / or poly (meth) acrylate polyols are used.

5. A method for producing a coating composition according to one of the Claims 1 to 4, characterized in that a water-dilutable hydroxy-functional polyurethane urea resin with a urea group content (calculated as -NHCONH-) of 10 to 300 mmol in 100 g solid resin, a urethane group content (calculated as -NHCOO-) of 20 to 30 mmol in 100 g solid resin, an OH number of 20 to 250 and a number-average molar mass Mn of 1000 to 20,000 g / mol, produced by

I) Preparation of a polyurethane prepolymer containing NCO groups by reaction

al) one or more hydroxy-functional compounds with a number-average molar mass Mn of 360 to 8000 g / mol

a2) one or more polyisocyanates and

II) subsequent reaction of the NCO group-containing

Polyurethane prepolymers with

a4) one or more hydroxy-functional monoamines and optionally with one or more polyols, in proportions such that the resulting polyurethane has the desired hydroxyl numbers and urea and urethane group proportions,

III) at least partially neutralizing the ionic groups or the groups of the polyurethane obtained which can be converted into ionic groups before or after the reaction in stage II and transfer of the reaction product obtained into the aqueous phase and the polyurethane resin thus obtained is mixed with one or more pigments, fillers, water, organic solvent and / or additives customary in lacquer and, before use, with one or more polyisocyanates with free isocyanate groups.

6. A process for the multi-layer coating of substrates, in particular of vehicles or their parts, by applying a filler layer to an optionally primed substrate and then overpainting with a top coat layer or a combination of basecoat and clear coat, characterized in that the preparation of the

Filler layer applies a coating agent according to any one of claims 1 to 4.

7. Use of the coating compositions according to one of claims 1 to 4 for the production of filler layers in multi-layer coating.

8. Use of the coating agent according to one of claims 1 to 4 in the painting of vehicles and vehicle parts.

9. A substrate provided with a multi-layer coating, containing one

Filler layer made of a coating agent according to one of claims 1 to 4.