DE19907988A1 - Aqueous polyurethane dispersion for use as binder in quick-drying paint for cars, is based on high- and low-molecular weight diol compounds with polyhydroxy component, polyisocyanate and hydroxy- or amino-acid - Google Patents

Abstract

Aqueous polyurethane dispersion from high- and low-mol. wt. diols, polyisocyanates and compounds with an acid group and 1 or 2 hydroxyl or amino groups, in which all the neutralizing agent is added before chain extension, the degree of neutralization is 40-105%, one of the diols contains at least 1 wt% tri- or higher-functional component and the urea group content is 1-4 wt%. An aqueous polyurethane (PUR) dispersion contains the reaction product of: (A) difunctional polyol(s) with a mol. wt. of 500-6000; (B) at least difunctional low-mol. wt. alcohol(s); (C) di- and/or tri-functional isocyanate(s); and (D) compound(s) with an acid group and one or two hydroxyl and/or prim. or sec. amino groups in an amount such that the product shows an acid number of less than 25 mg KOH/g solid. In this system: (i) all the neutralizing agent is added before the chain extension reaction; (ii) the degree of neutralization is in the range 40-105% based on acid groups; (iii) the starting materials for polyol(s) (A) or the low-mol. wt. component (B) contain(s) at least 1 wt% tri- or higher-functional components, based on total solid in (A-D); and (iv) the content of isolated urea groups, i.e. groups -(NH-CO-NH)- in the formula (I) is 1-4 wt%. (PUR-DIR)-(NH-CO-NH)-(DIR-PUR) (I) DIR = a di-isocyanate residue. Independent claims are also included for: (a) a process for the production of aqueous PUR dispersions by making an NCO- and acid-functional prepolymer from components (A-D) in organic solution, adding neutralizing agent (NA) equivalent to 40-105% of the acid groups, dispersing the prepolymer in or with water, possibly adding more NA up to the maximum (equivalent to 105%), stirring at 25-75 deg C to complete the chain extension with the NCO/water reaction and removing solvent (to a content of less than 5%) during or after dispersion or during or after chain extension; and (b) paint for barrier layers, containing 30-90 wt% PUR dispersion as described, 0-20 wt% crosslinker, 5-70 wt% pigments and/or fillers and 0-65 wt% other binders, plus the usual additives etc. for vehicle paint and possibly water to adjust the spray viscosity.

Description

The invention relates to new polyurethane dispersions, a process for their preparation position and their use in aqueous binders for quick-drying Coatings in automotive painting.

A multi-layer structure has established itself in automotive OEM painting is increasingly realized by aqueous coating compositions. Watery Due to the special properties of the dispersing or Solvent water often has the problem of achieving optimal coating properties drying at relatively high temperatures and / or for relative long times must be done. However, modern coatings increasingly need also meet requirements regarding high cost-effectiveness. An essential The goal is z. B., the coating structure in the automotive painting in poss As few and as inexpensive as possible, that is, above all, quickly to apply the subsequent individual steps. High drying temperatures, long Flash-off times or long drying times stand in the way of this requirement.

In the usual paint build-up in the original car painting, cathodi is used electrodeposition (KTL) primed metal surface first a stone impact protection layer and a filler layer or a combination of both ("Rockfall protection filler") applied. A pigment is then applied to these layers ter basecoat, followed by a clearcoat or alternatively a pigmented topcoat upset.

The stone chip protection filler layer compensates for unevenness in the Surface and creates a good elasticity and deformability Resistance to stone chips. So far, polyester has been used for this layer and polyurethanes as well as polyisocyanate or melamine crosslinkers. Before Ap Application of basecoat and clearcoat or topcoat becomes the stone chip protection filler branded. This is necessary to improve the topcoat level and possibly  to close any remaining imperfections in the filler layer. After application the clearcoat or topcoat is then baked again. Disadvantage of this The method is that two expensive baking processes are necessary. Physically, d. H. without stoving, quick-drying paints, such as those made from Polyacrylates can be formulated do not have the required stone chips stability, as they harden to films with insufficient film mechanical Lead property level.

The object of the present invention was to use a binder for a barrier layer Stone chip protection function to provide that in addition to a good stone impact resistance above all ensures very fast physical drying and wherein the coating obtained after the rapid physical drying has a very good water resistance and against dissolving by the subsequent applied base or topcoat is resistant. In addition, the Adhesion or interlayer adhesion should be excellent in order to ensure optimal Ensure paint build-up. In addition, the binder must be lightfast in order to in the case of moderately opaque topcoats or basecoats or in places where completely a pigmented topcoat or basecoat is omitted, a weather-resistant To produce coating. Excellent stability is also required, ins special viscosity stability according to formulated paints and a practical Right repair ability for necessary repairs directly on the line.

A proposed solution for stone chip-resistant coatings and / or filler layers The basis of aqueous binders is e.g. B. described in EP-A-0 330 139. The bean As is known, dispersions of acid-functional polyesters are known only to be present limits storage stability since it prevents rapid chemical degradation by splitting Subject to ester linkages (e.g. Jones, T.E .; McCarthy, J.M., J. Coatings Technol. 76 (844), p. 57 (1995)).

EP-A-0 498 156 describes polyester dispersions containing urethane groups wrote that very well for the production of stone chip protection intermediate primer  en or of stoving fillers with high stone chip resistance. To the However, to achieve this high level of properties are high curing temperatures or long burn-in times required.

DE-A-39 36 794 describes polyurethane dispersions containing carbonate groups and their use in automotive painting z. B. for basecoats, both under baking conditions at approx. 140 ° C, as well as in the case of repairs on the line approx. 80 ° C. Important requirements that these dispersions have to meet are e.g. B. Adhesion, weather resistance and condensation resistance even at 80 ° C Drying.

DE-A-44 38 504 describes paint layer formulations based on water ver thinnable polyurethane resins with an average molecular weight Mn of 4000 to 25000 g / mol, with which as thin as possible lacquer films for filler and stone chips base layers can be produced.

However, there is still a need for further improved products that are in the Are able to cover the ever increasing demands and diverse range enable turns. In particular, a very fast physical Drying, a quickly accessible, very good water resistance and a very high Hardness-elasticity level required, what with the products according to the state of the art nik cannot always be reached.

Surprisingly, it has now been found the special high-molecular solvent free, a relatively high content of carboxylate groups and isolated urea group pen-containing polyurethane dispersions of reaction products from minde at least one polyol component, at least one, at least dihydroxy-functional low molecular weight compound, at least one hydrophilizing component and at least one at least difunctional isocyanate is particularly suitable are the requirements placed on a barrier layer with stone chip protection function gen to meet. It was also found that such products can be used after a  very simple, and therefore particularly inexpensive, method consisting of a one-step, rapid urethanization reaction, Dis and then simultaneous solvent distillation and Chain extension reaction. This makes it possible to to manufacture environmentally friendly products at low cost.

The invention thus relates to aqueous polyurethane dispersions from implementation products of

• A) at least one, at least difunctional polyol of molecular weight rich 500-6000,
• B) at least one, at least difunctional, low molecular weight alcohol,
• C) at least one, di- and / or trifunctional isocyanate and
• D) at least one compound with an acid group and one or two hydroxy and / or primary or secondary amino groups in such an amount that an acid number based on solids content of <25 mg KOH / g substance ensures

the total amount of neutralizing agent being added before the chain extension reaction,
wherein the degree of neutralization is at least 60, but at most 105% based on the amount of acid groups,
where either in the starting components of the polyols A) or in the never dermolecular component B) trifunctional or higher functional components in an amount of at least 1 wt .-%, based on the total amount of solids of A) to D), and
a content of isolated urea groups (in the bracket of formula I) of 1 to 4 wt .-% is contained.

Formula I.

The invention also relates to a process for the production of the invention moderate polyurethane dispersions, characterized in that from the above Components A), B), C), and D) in organic solution first an NCO and acid made of a functional polyurethane prepolymer, then for at least 65, at most 105% of the acid groups neutralizing agent added and that prepolymer thus obtained is dispersed in or with water, then optionally Neutralizing agent up to the maximum amount of neutralization 105% added and stirred at 25 to 75 ° C until the under NCO Water reaction chain extension is complete, while during or after the dispersion or during or after the chain extension reaction on the organic solvent up to an amount <2.5, preferably <0.5%, d. H. practically completely removed.

The invention also relates to the use of the poly according to the invention urethane dispersions in paints and coatings.

Suitable components A) are at least difunctional polyesters, polyethers, Polyether polyamines, polycarbonates, polyester amides of the molecular range 500- 6000. These can be dihydroxy polyester from dicarboxylic acids or their anhy three, e.g. B. adipic acid, succinic acid, phthalic anhydride, isophthalic acid, Terephthalic acid, suberic acid, azelaic acid, sebaceic acid, tetrahydrophthalic acid, Maleic anhydride, dimer fatty acids and diols, e.g. B. ethylene glycol, propy  lenglycol, 1,3-propanediol, diethylene glycol, triethylene glycol, 1,4-butanediol, hexane diol-1,6, trimethylpentanediol, cyclohexanediol-1,4, cyclohexanedimethanol-1,4, Neopentyl glycol, octanediol-1,8. Polyester can also be used, the certain amounts of mono-, tri- or tetrafunctional raw materials, such as B. 2-ethyl hexanoic acid, benzoic acid, soybean oil fatty acid, oleic acid, stearic fatty acid, sunflowers oleic acid, trimellitic anhydride, trimethylolpropane, glycerin, pentaerythritol ent hold.

Polyesters on lactone, in particular ε-capro, can also be used lactone base, polycarbonates, such as those obtained by implementing, for example, the above named diols are accessible with diaryl or dialkyl carbonates or phosgene, as well as castor oil. Also suitable are polyethers such as z. B. using of diols, triplets, water or amines as a starter molecule by polymerization of propylene oxide and / or tetrahydrofuran, possibly with the use of less Amounts of ethylene oxide and / or styrene oxide can be obtained.

Components A) which are preferably used are difunctional polyesters of the mole Kularweightes 840 to 2600 based on aliphatic raw materials such. B. adipic acid, Maleic anhydride, hexanediol, neopentyl glycol, ethylene glycol, propylene glycol, Diethylene glycol, especially aliphatic polyester diols of molecular weight 1700 to 2100 based on adipic acid, hexanediol and neopentyl glycol.

Components A) which are preferably used are likewise aliphatic polycarbo natural diols or polyester carbonate diols with a molecular weight of 840 to 2600.

The total amount of component A) very particularly preferably consists of one Mixture of 20 to 80 wt .-% of an aliphatic polyester diol of the molecular weight 840 to 2100 and from 80 to 20 wt .-% of an aliphatic polycarbonate diols or polyester carbonate diols of molecular weight 1000 to 2100.  

Surprisingly, it was found that such a mixture e.g. B. particularly good Properties related to rapid drying of the dispersion combined with very good water resistance and high stone chip protection level of the barrier layer. If polyester diols are used alone, they are good for water resistance and Hydrolysis stability the selection of special polyester diols z. B. based on Adipin Acid, hexanediol, neopentyl glycol in the molecular weight range 1700 to 2100 advantageous. The sole use of polycarbonate diols can cause problems in the film optics z. B. by not optimal course and under unfavorable circumstances also lead to non-optimal interlayer adhesion, which then elaborates special recipes.

Suitable low molecular weight components B) can be e.g. B. ethylene glycol, 1,4- Butanediol, 1,6-hexanediol, neopentyl glycol, trimethylol propane, glycerin, pentae rythritol, trimethylpentanediol, propylene glycol, 1,3-propanediol, 1,4-cyclohexadi methanol, or their reaction products with ethylene and / or propylene oxide. The Molecular weight of B) can be between 62 and 400.

A trifunctional or higher functional lower mole is preferably used as component B) Kular alcohol such as trimethylolpropane, glycerol, pentaerythritol, or their implementation tion products with 1 to 6 moles of ethylene and / or propylene oxide used.

The use of trifunctional alcohols such as trimes is very particularly preferred thylolpropane or glycerin in an amount of 0.5 to 4.0, preferably from 1.0 to 3.0% by weight.

Suitable components C) can be di- and / or trifunctional aliphatic Isocyanates such as B. hexamethylene diisocyanate, butane diisocyanate, isophorone diisocy anate, 1-methyl-2,4 (2,6) -diisocyanatocyclohexane, norbornane diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, hexahydroxylylene diisocyanate, nonantrii socyanate, 4,4'-diisocyanatodicyclohexylmethane. Mitver is also suitable use of aromatic isocyanates such. B. 2,4 (2,6) -diisocyanatotoluene or 4,4'-  Diisocyanatodiphenylmethane and higher molecular weight or oligomeric polyisocyanates of the molecular weight range 336 to 1500 based on the aliphati mentioned above isocyanates.

4,4'-Diisocyanatodicyclohexylmethane and / or isophorone diisocyanate and / or hexamethylene diisocyanate and / or 1-methyl-2,4 (2,6) -diiso are preferred cyanatocyclohexane used.

The use of isophorone diisocyanate and / or is very particularly preferred Hexamethylene diisocyanate or mixtures of 4,4'-diisocyanatodicyclo hexylmethane with isophorone diisocyanate or hexamethylene diisocyanate.

The very particularly preferred components C) enable the production particularly high-quality polyurethane dispersions for barrier layers with excellent stone chip protection level and overall convincing property level.

Component D) consists of at least one (potentially) ionic compound with at least one acid group and at least one against isocyanate groups reactive hydroxyl and / or amino group.

These compounds are preferably at least one, before preferably one or two hydroxyl and / or amino groups containing carbon acid. Suitable acids of this type are, for example, 2,2-bis (hydroxymethyl) alkane carboxylic acid such as dimethylolacetic acid, 2,2-dimethylolpropionic acid, 2,2-dimethyl butyric acid or 2,2-dimethylol-pentanoic acid, dihydroxysuccinic acid, hydroxypi valic acid or mixtures of such acids. Preferably as a component D) Dimethylolpropionic acid and / or hydroxypivalic acid used. Likewise possible, but less preferred, is the use of optionally ether group-containing sulfonic acid diols of the type described in US Pat. No. 4,108,814 as anionic structural component D). The free acid groups are the first referred to as "potentially ionic" groups, while the by  Neutralization with salt-like groups obtained, in particular whose carboxylate groups are "ionic" groups.

Component D) is used in amounts such that the acid number is based on Solids content of the dispersion at <25, preferably at <20 mg / KOH g substance lies.

Surprisingly, it was found that despite the relatively high acid number or resulting high content of salt groups, e.g. B. carboxylate groups, Dis Persions are obtained that are used to make barrier layers very quickly achieve achieved, earlier water resistance. Despite the high salt group content tes and the high molecular weight of the dispersions of the invention Surprisingly possible, coatings for barrier layers with an extraordinarily high mechanical, e.g. B. hardness-elasticity level and excellent stone chip protection veau to formulate a solids content of 50 at application viscosity Have wt .-% or more.

In addition to the structural components A), B), C), D) can optionally in small to the extent, in amounts <4% by weight, also a component E) in the production of the polyurethane dispersions can also be used. Components E) cannot be ionic-hydrophilic polyethers, one or two per molecule compared to Isocya-. nat groups reactive groups, especially hydroxyl groups.

The aqueous polyurethane dispersions according to the invention preferably contain reaction products of:

• A) 50 to 80 wt .-% of at least one, at least difunctional aliphatic Polyols based on polyester, polyester carbonate and / or polycarbonate of Mo molecular weight 840 to 2600,
• B) 0.5 to 4% by weight of at least one, at least difunctional, low molecular weight ren alcohol with molecular weight 62 to 400,  
• C) 18 to 38% by weight of at least one di- and / or trifunctional isocyanate,
• D) 2.5 to 6% by weight of dimethylolpropionic acid and / or dimethylolbutyric acid and / or hydroxypivalic acid,

the total amount of neutralizing agent being added before the chain extension reaction,
wherein the degree of neutralization is at least 60, but at most 105% based on the amount of acid groups,
where either in the starting components of the polyols A) or in the never dermolecular component B) trifunctional or higher functional components in an amount of at least 1 wt .-%, based on the total amount of solids of A) to D), and
a content of isolated urea groups (in the bracket of formula I) of 1 to 4 wt .-% is contained.

Particularly preferred aqueous polyurethane dispersions according to the invention contain reaction products of:

• A) 55 to 75 wt .-% of a mixture of 20 to 80 wt .-% of an aliphatic Polyester diols of molecular weight 840 to 2100 and from 80 to 20% by weight an aliphatic polycarbonate diol or polyester carbonate diol of the molecule Lar weight 1000 to 2100,
• B) 1 to 3% by weight of a trifunctional, low molecular weight alcohol, in particular Trimethylolpropane or glycerin,
• C) 20 to 35 wt .-% isophorone diisocyanate and / or hexamethylene diisocyanate and / or a mixture of 4,4'-diisocyanatodicyclohexylmethane with isopho rondiisocyanate or hexamethylene diisocyanate,
• D) 3.5 to 4.9% by weight of dimethylolpropionic acid.

The reaction of the hydroxy-functional components A), B), D) and optionally E) with the isocyanate-functional component C) is carried out in a manner known per se se one or more stages, the proportions of the reactants so ge  be chosen that the equivalent ratio of NCO: OH groups at 2.5: 1 to 1.2: 1, preferably 1.7: 1 to 1.4: 1. The reaction can be reduced with the addition Amounts of catalysts such. B. dibutyltin dilaurate, tin 2-octoate, dibutyltin oxide or diazabicyclononane can be carried out.

To avoid viscosity, stirring, mixing and heat dissipation problems the reaction in 35 to 97% organic solution, particularly preferably in 55 to 75% acetone solution carried out.

Before dispersing the organically dissolved, NCO-functional polyurethane pre polymer is used for at least 60, preferably at least 70%, but at most 105% of the acid groups added neutralizing agent.

It is also possible to add the neutralizing agent to the dispersing water.

Preferred neutralizing agents are e.g. B. triethylamine, N-methylmorpholine, Di methylisopropylamine, diethylisopropylamine, may also be suitable, e.g. B. Diisopropylaminoethanol, dimethylethanolamine, dimethylisopropanolamine. It can mixtures of different neutralizing agents can also be used. On moniak is also suitable as a neutralizing agent in some cases.

Diethylisopropylamine, optionally in a mixture with an, is particularly preferred their amines.

After the polyurethane prepolymer has been dispersed in / by water stirred until all NCO groups by NCO water reaction with chain ver prolonged reaction over isolated urea structural units. It can if necessary, other neutralizing agents are added, the new Degree of talization based on built-in acid groups is at most 105%.  

The solvents used to produce the polyurethane prepolymer can partially or preferably completely separated from the dispersion by distillation become. Dispersions according to the invention preferably contain less than 2.5 % By weight, particularly preferably practically no organic solvent.

The distillation is carried out in such a way that no neutralizing agent used is distilled off is, should this be due to unfavorably chosen distillation conditions If so, the appropriate amount of neutralizing agent will be added to the dispersion finally added again.

When extending the chain of the NCO-functional polyurethane prepolymer in Water can optionally mo up to 40% of the existing NCO groups no-, di- or trifunctional chain extension or chain termination agent from be known type, which may also include ionic groups, acid groups or Hy droxyl groups can be added. However, it is preferred to finally a chain extension was carried out via the NCO-water reaction.

The dispersions according to the invention have a (calculated and based on 100% solids content) content of isolated urea structural units of the following type (formula in square brackets):

from 1.0 to 4.0%, preferably from 1.75 to 3.25%.

The calculation is based on the assumption that half of the NCO groups of the polyurethane prepolymer react with water with CO ₂ elimination to form amino groups, which then react with the second half of the NCO groups to form isolated monourea bridges with an increase in molecular weight.

The dispersions of the invention have particle diameters, determined, for. B. by LKS measurements, from 20 to 600, preferably from 50 to 150 nm.

The solids content of the dispersions is at least 30, preferably at least at least 35%. The pH of the dispersion is below 8.5, preferably below 7.8 average molecular weights Mn of the dispersion are <20,000, preferably < 30,000 and very particularly preferably <40,000 g / mol (determined, for example, by gelper meation chromatography). In a special embodiment, the disper proportionally very high molecular weight, no longer completely in organic solvents contain soluble fractions, which then ent a molecular weight determination pull.

The products according to the invention are arbitrary for coating or painting Substrates, especially wood, ceramics, stone, concrete, bitumen, hard fiber, glass, por cellan, plastics and metallic substrates of all kinds. They can also be used as a finish or finish for textile and leather applications layering.

The preferred area of application is vehicle painting, especially as a barrier layer with a high level of stone chip protection and excellent water resistance.

To use the dispersions according to the invention the usual auxiliaries and additives are added to them. These include at for example inorganic or organic pigments, fillers such as Carbon black, silica, talc, chalk, silica, kaolin, glass as powder or in form of fibers, cellulose or cellulose acetobutyrate, and crosslinking agents such as blocked polyisocyanates, polyisocyanates, melamine resins, urea resins, urea  Aldehyde resins, carbodiimides, carbamates, tris (alkoxycabonylamino) triazines, carba mat modified amino crosslinking resins. The crosslinking agents can be in water dis pergierbar or not used in water-dispersible form.

Examples of suitable polyi on which the blocked polyisocyanates are based socyanates are cycloaliphatic or aliphatic polyisocyanates such as hexamethy lendiisocyanate (HDI), 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (Isophorone diisocyanate, IPDI), methylene bis (4-isocyanatocyclohexane), tetrame thylxylylene diisocyanate (TMXDI). Polyisocyanates, He contain teroatoms in the radical containing the isocyanate groups. Examples here for are carbodiimide groups, allophanate groups, isocyanurate groups, urethane polyisocyanates containing groups and biureth groups. Especially good for the he the known polyisocyanates, which are mainly used in the manufacture position of paints are used, for. B. biureth, isocyanurate or urethdione group-containing modification products of the above-mentioned simple polyi socyanate, especially hexamethylene diisocyanate or isophorone diisocyanate nats. Low molecular weight polyisocya containing urethane groups are also suitable nate, as by using IPDI or TDI in excess simple polyhydric alcohols in the molecular weight range 62-300, esp especially with trimethylolpropane or glycerol can be obtained. It can also any mixtures of the polyisocyanates mentioned for the preparation of the inventions products according to the invention are used. Suitable polyisocyanates are also known prepolymers containing terminal isocyanate groups, as described in particular especially by implementing the simple polyisocyanates mentioned above, especially Diisocyanates, with insufficient amounts of organic compounds with at least at least two functional groups that are reactive towards isocyanates are accessible are.

The isocyanate groups of the polyisocyanates are blocked. As a blocking agent usual compounds can be used, such as those on the Paint sector are used. Examples of suitable blocking agents are malon  acid dimethyl ester, malonic acid diethyl ester, acetoacetic acid ethyl ester, caprolactam, secondary aliphatic amine, butanone oxime, 3,5-dimethylpyrazole.

The blocked polyisocyanates described can be in non-hydrophilic form are used, the transfer into the aqueous dispersion z. B. by Mix and disperse with the polyurethane prepolymer can be made. However, it can also be the polyurethane according to the invention dispersion as a polymeric emulsifier for non-water-dispersible crosslinking alone agents are used. It is also possible to use the polyu according to the invention rethane dispersion a hydrophilized, water-dispersible or already in water to add the more dispersible form of the blocked polyisocyanate present. Hydro Philated blocked polyisocyanates are known and z. B. described in EP-A- 0 566 953.

Reactive amino crosslinking resins or Melamine resins such as B. ®Cymel 328 (Cytec), and / or trisalkoxycarbonylami notriazines such as B. ®TACT (Cytec) and / or reactive, e.g. B. malonic ester blocked Polyisocyanate crosslinking agents and / or urethanized melamine resins are used.

The polyurethane dispersions according to the invention can be used with other binders be combined. The combination with water-soluble or water is preferred insoluble melamine resins and water-emulsifiable or water-dispersible Polyester resins or polyester-polyurethane resins.

Processing the dispersion to make coatings according to any Methods, for example by brushing, pouring, spraying, dipping, rolling or Squeegees.

The dispersions of the invention are e.g. B. suitable for the production of paints, Coatings, sealants and adhesives.  

The drying of the products obtained using various application techniques can at room temperature or at elevated temperature up to 200 ° C, preferably at 60-150 ° C take place.

In the preferred use according to the invention as physically very fast coating that dries at low temperatures in vehicle paintwork The application takes place as a barrier layer with a high level of stone chip protection preferably by spraying and drying, preferably for 5 to 10 minutes 50 to 80 ° C.

The dry film layer thickness can be, for example, 15-50 μm, it is however, coatings with a higher layer thickness are possible. The coating can highly elastic, but, depending on the requirement profile, can also be set hard. To After drying, the barrier layer can be sanded and painted over very well. After this Paint over with a basecoat / clearcoat or a pigmented topcoat then a common burn-in process takes place, e.g. B. for 20-25 minutes at 120- 160 ° C.

The coating produced in this way has optically and mechanically comparable or bes results like a lacquer build-up, in which instead of the barrier layer as usual Lich used filler with z. B. 35-45 microns dry film thickness with a own burn-in of z. B. 20-25 minutes at 135-165 ° C and in addition Basecoat / clear coat or top coat can be applied.

The dispersions according to the invention can be combined with other ionic or nonionic rule dispersions or aqueous solutions are mixed, for. B. with polyester Polyvinyl acetate, polyethylene, polystyrene, polybutadiene, polyurethane, Po lyvinylchloride, polyester-polyacrylate, polyacrylate and copolymer Dispersions or solutions. Even the addition of chemically known, not known fixed, preferably ionic emulsifiers are possible.  

The use of water-soluble or water-dispersible is preferred Polyesters, polyester-polyurethanes, polyester-polyacrylates and others Polyurethane dispersions, especially of polyurethane dispersions with faster physical drying and high hard segment contents.

Lacquers for barrier layers according to the invention are also included in the automotive industry painting usual additives and auxiliaries and optionally water for one provide the spray viscosity.

• a) 30 to 90, preferably 45 to 75 wt .-% polyurethane disper according to the invention sion,
• b) 0 to 20, preferably 1 to 10% by weight of crosslinking agent,
• c) 5 to 90, preferably 10 to 60% by weight of pigments and / or fillers,
• d) 0 to 90, preferably 10 to 50% by weight of other binders, preferably aqueous polyester or polyester-polyurethane solutions or dispersions.

The coatings for barrier layers according to the invention have solids contents of at least 45, preferably at least 50% with application viscosity on and show even in the presence of highly reactive crosslinking agents for stoving enamels, e.g. B. based on melamine resin, very good viscosity stability during storage.

At the same time, the barriers prepared from the dispersions according to the invention have layers have excellent stone chip resistance and very good adhesion or interlayer liability.

The polyurethane dispersions according to the invention can also be used for production more active stoving lacquers that can be hardened at low temperatures, especially Ein burning fillers are used. They are preferably ge with the above called reactive crosslinking resins and possibly other polymers so com biniert, which optionally with the use of suitable catalysts and the conventional pigments, additives and auxiliaries that can be hardened at 90 to 120 ° C. layers are obtained.  

The following examples are intended to illustrate the invention:

Example 1

Place in a dry 2-liter reaction vessel with a stirring, cooling and heating device 144 g of an aliphatic polycarbonate diol (Desmophen® 2020, Bayer AG, Mol weight 2000), 108 g of a polyester diol based on adipic acid, hexanediol, Neopentylglycol (molecular weight 2000) and 17.6 g dimethylolpropionic acid under stick Weighed the substance atmosphere and heated to 65 ° C. Then 6.0 grams of trime ethyl propane, 200 g acetone, 59.5 isophorone diisocyanate and 39.0 g hexamethylene diisocyanate added and heated to reflux temperature. It is heated as long until the theoretical NCO value is reached or slightly undershot. After cooling 10.0 g of triethylamine (degree of neutralization, i.e.% of that in the Salt form converted carboxyl groups, is 75%) and then 550 g of distilled Water added. The mixture is stirred at 40 to 50 ° C until no free NCO Groups are more detectable. The acetone is then removed by distillation. An approximately 40% finely divided dispersion 1) with a pH of 7.3 and a viscosity of approx. 200 mPa.s / 23 ° C.

Example 2) (comparison)

Polyester dispersion containing urethane groups according to EP-A-0 498 156, Example 2), approx. 41% solids content. Viscosity approx. 1000 mPa.s / 23 ° C.

Application example 3) (according to the invention) Creation of a barrier layer

A varnish for a barrier layer 3) is produced from 117 g of pigment paste ^A), 182 g of dispersion 1), 9.8 g of amino crosslinking resin (®Cymel 328, Cytec) and 10 g of distilled water. The varnish has a pH of 7.6, a solids content of 52% and an ISO 5 cup run-out time of 21 seconds. After the paint had been stored for 14 days at room temperature, the viscosity rose only slightly (24 seconds).

^A) The pigment paste is produced from the following raw materials by grinding on a bead mill: 42.2 g ® Bayhydrol D270 (water-dispersible polyester resin, 70% dissolved in organic solvents, Bayer), 82.4 g distilled water, 6 g of a 10% aqueous solution of dimethylethanolamine, 5.4% of a 50% solution of ®Surfynol 104 (wetting aid, Air Products) in NMP, 5.4 g ®Additol XW 395, 108.2 g ®Bayertitan R-FD-I (titanium dioxide , Bayer), 1.2 g ®Bayferrox 303T (iron oxide, Bayer), 108.9 g ®Blanc fixe micro (Sachtleben), 26.6 g ®Talkum IT extra (Norwegian Talk) and 3.7 g ®Aerosil R 972 (Degussa).

The following paint structure is applied to sheets provided with cathodic dip coating (KTL) and cured as indicated:

• a) barrier layer 3), 20 µm dry film thickness, 10 minutes 70 ° C drying,
• b) Commercial basecoat, black, 15 µm dry film thickness, 10 minutes 80 ° C drying,
• c) Commercial medium solid clear coat, 40 µm dry film thickness, 25 minutes Burn in at 145 ° C.

The following test results were then obtained:
Appearance of the coating after application: OK
Intermediate liability barrier topcoat (grades from 1 to 3, 1 is very good, 3 is bad): 1
Intermediate liability barrier-KTL (grades from 1 to 3, 1 is very good, 3 is bad): 1
Stone chip resistance (grades from 1 to 10, 1 is very good, 10 is very bad): 1.

Testing in the event of a repair, ie in the paint build-up, the basecoat and clearcoat are applied and hardened again as described above (ie there are a total of 6 paint layers on top of each other):
Flake off the filler (grades from 1 to 7, 1 is very good, 7 is very bad): 1
Stone chip resistance (grades from 1 to 10, 1 is very good, 10 is very bad): 1.

A film with 20 µm is used to check the water resistance of the barrier layer Dry film thickness applied and dried for 10 minutes at 70 ° C. Then it will be sensitivity to water swelling measured (grades 0 to 5, 0 means no no action, 5 means film dissolved): 1.

To check the film hardness and the solubility, a film with 20 µm dry film thickness is applied, flashed off at 80 ° C for 5 minutes and baked at 145 ° C for 22 minutes:
Film hardness: 58 pendulum seconds (according to König)
Solvent resistance (test for solubility after one minute exposure to the following solvents: toluene, methoxypropylacetate, ethyl acetate, acetone, ratings 0 to 5, 0 is unchanged, 5 is detached): 2/2/2/2

Dispersion 1) fulfills all requirements placed on a barrier layer.

Example of use 4) (comparison)

As described in Example 3), using comparative dispersion 2) instead of the dispersion 1) a varnish for a barrier layer is produced, corresponding Coatings applied and cured, and the properties checked.

The following test results were obtained:
Solids paint: 51%, pH 7.5
Appearance of the coating after application: not in order, base coat does not adhere optimally to the barrier layer, it bursts.
A liability or stone chip protection test in the paint structure is not possible.
Check the water resistance of the barrier layer after drying for 10 minutes at 70 ° C: 5
Film hardness: 14 pendulum seconds (after König)
Resistance to solvents: 4/3/4/4

The comparison product is unsuitable as a barrier layer, and are also solvent-free stability and above all the film hardness and water resistance are inadequate.

Example 5) (comparison)

Place in a dry 2-liter reaction vessel with a stirring, cooling and heating device 144 g of an aliphatic polycarbonate diol (Desmophen® 2020, Bayer AG, Mol weight 2000), 108 g of a polyester diol based on adipic acid, hexanediol, Neopentylglycol (molecular weight 2000) and 17.6 g dimethylolpropionic acid under stick Weighed the substance atmosphere and heated to 65 ° C. Then 6.0 grams of trime ethyl propane, 200 g acetone, 59.5 isophorone diisocyanate and 39.0 g hexamethylene diisocyanate added and heated to reflux temperature. It is heated as long until the theoretical NCO value is reached or slightly undercut. After cooling 5.8 g of ethylenediamine, diluted with 30 g of water, are added to 60 ° C. in 5 minutes given, which corresponds to a chain extension degree of approx. 60% (i.e. for approx. 60% of the remaining NCO groups become reactive amino groups in the form a diamine added), after stirring for 15 minutes, 10.0 g of triethylamine (Degree of neutralization 75%) and then 5500 g of distilled water. The mixture is stirred at 40 to 50 ° C until no more free NCO groups are detectable. The acetone is then removed by distillation. After adding Another distilled water to reduce viscosity gives an approx. 32% finely divided dispersion 5) with a pH of 7, 8 and a viscosity of approx. 1100 mPa.s / 23 ° C.

Application example 6 (comparison)

As described in Example 3), using comparative dispersion 5) instead of the dispersion 1) a varnish for a barrier layer is produced, corresponding Coatings applied and cured, and the properties checked.

The following test results were obtained:
Paint solids: 42%, pH value paint 8.1
Appearance of the coating after application: Not OK, bubbles in the clear coat.

The paint solid is clearly too low, the use as a barrier leads to unacceptable results.

Example 7 (comparison)

Polyurethane dispersion containing carbonate groups according to DE-A-29 26 794, example A), approx. 40% solids content. Viscosity approx. 50 mPa.s / 23 ° C.

Application example 8) (comparison)

As described in Example 3), using comparative dispersion 7) instead of the dispersion 1) a varnish for a barrier layer is produced, corresponding Coatings applied and cured, and the properties checked.

The following test results were obtained:
Solids paint: 52%, pH 7.5
Appearance of the coating after application: limited in order (bursting of the basecoat after drying for 5 minutes at 80 ° C).
Check the water resistance of the barrier layer after drying for 10 minutes at 70 ° C: 5
Film hardness: 34 pendulum seconds
Resistance to solvents: 2/3/3/4.

The comparative example is unsuitable as a barrier layer since there is no homogeneous coating construction is achieved, and the film hardness, but above all the water resistance is insufficient is.

Example 9

Place in a dry 2-liter reaction vessel with a stirring, cooling and heating device 420 g of a polyester diol based on adipic acid, hexanediol, neopentyl glycol (mol weight 2000) and 29.2 g of dimethylolpropionic acid under a nitrogen atmosphere weighed and heated to 65 ° C. Then 10.0 g of trimethylolpropane, 210 g  Acetone, 114.9 isophorone diisocyanate and 52.9 g hexamethylene diisocyanate ben and heated to reflux temperature. It is heated until the theoretical NCO value reached or slightly undershot. After cooling to 45 ° C 20.6 g of diethylisopropylamine (degree of neutralization 80%) and then 970 g of distile added water. The mixture is stirred at 40 to 50 ° C until no free NCO groups are more detectable. The acetone is then distilled away. An approximately 39% finely divided dispersion 9) with a pH is obtained of 7.3 and a viscosity of approx. 800 mPa.s / 23 ° C.

Application example 10) (according to the invention) Creation of a barrier layer

A varnish for a barrier layer 10) is produced from 117 g of pigment paste ^A) , 195 g of dispersion 9), 9.8 g of amino crosslinking resin (®Cymel 328, Cytec) and 8 g of distilled water. The varnish has a pH of 7.5, a solids content of 50.3% and an ISO 5 cup run-out time of 21 seconds. After 14 days of storage of the varnish at room temperature, the viscosity rose only slightly (27 seconds).

The following test results in the paint structure were obtained:
Appearance of the coating after application: OK
Intermediate liability barrier topcoat (grades from 1 to 3, 1 is very good, 3 is bad): 1
Intermediate liability barrier-KTL (grades from 1 to 3, 1 is very good, 3 is bad): 1
Stone chip resistance (grades from 1 to 10, 1 is very good, 10 is very bad): 1 test in case of repair:
Flake off the filler (grades from 1 to 7, 1 is very good, 7 is very bad): 1,
Stone chip resistance (grades from 1 to 10, 1 is very good, 10 is very bad): 1
Water resistance of the barrier layer: 1.

To check the film hardness and the solubility, a film with 20 µm dry film thickness is applied, flashed off at 80 ° C for 5 minutes and baked at 145 ° C for 22 minutes:
Film hardness: 48 pendulum seconds (after König)
Resistance to solvents (test of solubility at one minute exposure to X / Y / Z / W,
Rating 0 to 5, 0 is unchanged, 5 is replaced): 1/1/2/3
Dispersion 9) meets all requirements.

Example 11

Place in a dry 2-liter reaction vessel with a stirring, cooling and heating device 272 g of an aliphatic polycarbonate diol (Desmophen® 2020, Bayer AG, Mol weight 2000), 272 g of a polyester diol based on adipic acid, hexanediol, Neopentylglycol (molecular weight 1700) and 26.8 g dimethylolpropionic acid under stick Weighed the substance atmosphere and heated to 65 ° C. Then 11.3 grams of trime ethyl propane, 250 g acetone, 106.6 isophorone diisocyanate and 75.9 g hexamethylene diisocyanate and 0.025% dibutyltin dilaurate added and at reflux temperature heated. It is heated until the theoretical NCO value is reached or slightly is under. After cooling to 45 ° C, 17.2 g of triethylamine (neutralized onsgrad 85%) and then added 1250 g of distilled water. It will be so long at 40 to 50 ° C until no more free NCO groups can be detected are. The acetone is then removed by distillation. You get an approx. 38% very fine dispersion 11) with a pH of 7, 7 and a viscosity of approx. 7500 mPa.s / 23 ° C.

Application example 12) (according to the invention) Creation of a barrier layer

A varnish for a barrier layer 10) is produced from 117 g of a pigment paste ^A) , 209 g of dispersion 11), 9.8 g of amino crosslinking resin (®Cymel 328, Cytec) and 8 g of distilled water. The varnish has a pH value of 7.5, a solids content of approx. 49% and an ISO 5 cup run-out time of 15 seconds. After 14 days of storage of the paint at room temperature, the viscosity increased only slightly (17 seconds).

The following test results in the paint structure were obtained:
Appearance of the coating after application: OK
Intermediate liability barrier topcoat (grades from 1 to 3, 1 is very good, 3 is bad): 1
Intermediate liability barrier-KTL (grades from 1 to 3, 1 is very good, 3 is bad): 1
Stone chip resistance (grades from 1 to 10, 1 is very good, 10 is very bad): 1
Inspection in the event of a repair:
Flake off the filler (grades from 1 to 7, 1 is very good, 7 is very bad): 1
Stone chip resistance (grades from 1 to 10, 1 is very good, 10 is very bad): 1
Water resistance of the barrier layer: 1
To check the film hardness and the solubility, a film with 20 µm dry film thickness is applied, flashed off at 80 ° C for 5 minutes and baked at 145 ° C for 22 minutes:
Film hardness: 41 pendulum seconds (after König)
Resistance to solvents: 2/2/2/3
Dispersion 11) meets all requirements, but due to the reduced content of dimethlol propionic acid the film hardness is in the lower range of the acceptable values.

Claims (15)

1. Aqueous polyurethane dispersion containing reaction products of

• A) at least one, at least difunctional polyol of the molecular weight range 500-6000,
• B) at least one, at least difunctional, low molecular weight alcohol,
• C) at least one, di- and / or trifunctional isocyanate and
• D) at least one compound with an acid group and one or two hydroxy and / or primary or secondary amino groups in an amount which ensures an acid number based on solids content of <25 mg KOH / g substance,

wherein the degree of neutralization is at least 60, but at most 105%, based on the amount of acid groups,
where either in the starting components of the polyols A) or in the never dermolecular component B) trifunctional or higher functional components in an amount of at least 1 wt .-%, based on the total amount of solids of A) to D), and
a content of isolated urea groups (in the bracket of formula I)
from 1 to 4% by weight is contained. 2. Aqueous polyurethane dispersion according to claim 1 containing Umsaltungspro products of

• A) 50 to 80% by weight of at least one, at least difunctional aliphatic polyol based on polyester, polyester carbonate and / or polycarbonate with a molecular weight of 840 to 2600,
• B) 0.5 to 4% by weight of at least one, at least difunctional, low-molecular alcohol with a molecular weight of 62 to 400,
• C) 18 to 38% by weight of at least one di- and / or trifunctional isocyanate,
• D) 2.5 to 6% by weight of dimethylolpropionic acid and / or dimethylolbutyric acid and / or hydroxypivalic acid and
• E) less than 4% by weight of nonionic-hydrophilic, monofunctional polyethers with molecular weights from 350 to 2500,

the total amount of neutralizing agent being added before the chain extension reaction,
wherein the degree of neutralization is at least 60, but at most 105%, based on the amount of acid groups,
where either in the starting components of the polyols A) or in the never dermolecular component B) trifunctional or higher functional components in an amount of at least 1 wt .-%, based on the total amount of solids of A) to D), and
a content of isolated urea groups (in the bracket of formula I)
from 1 to 4% by weight is contained. 3. Aqueous polyurethane dispersion according to claims 1 and 2 containing implementation products of

• A) 55 to 75% by weight of a mixture of 20 to 80% by weight of an aliphatic polyester diol with a molecular weight of 840 to 2100 and from 80 to 20% by weight of an aliphatic polycarbonate diol or polyester carbonate diol with a molecular weight of 1000 to 2100,
• B) 1 to 3% by weight of a trifunctional, low molecular weight alcohol,
• C) 20 to 35 wt .-% isophorone diisocyanate and / or hexamethylene diisocyanate and / or a mixture of 4,4'-diisocyanatodicyclohexylmethane with isophore diisocyanate or hexamethylene diisocyanate, and
• D) 3.5 to 4.9% by weight of dimethylolpropionic acid.

4. Aqueous polyurethane dispersion according to claims 1 and 2 containing implementation products of

• A) 55 to 75% by weight of an aliphatic polyester diol based on adipic acid, hexanediol, neopentyl glycol with a molecular weight of 1700 to 2100,
• B) 1 to 3% by weight of a trifunctional, low molecular weight alcohol,
• C) 20 to 35 wt .-% isophorone diisocyanate and / or hexamethylene diisocyanate and / or a mixture of 4,4'-diisocyanatodicyclohexylmethane with isophore diisocyanate or hexamethylene diisocyanate, and
• D) 3.5 to 4.9% by weight of dimethylolpropionic acid.

5. Aqueous polyurethane dispersion according to claims 1 to 4, characterized ge indicates that trifunctional raw materials only in component B) are included. 6. Aqueous polyurethane dispersion according to claims 1 to 5, characterized ge indicates that the average molecular weight of the polyurethane Mn <30000 g / mol   7. Aqueous polyurethane dispersion according to claims 1 to 5, characterized ge indicates that they are solvent-free, the acid number (based on solids) <20 mg KOH / g substance and the molecular weight Mn is <30000 g / mol. 8. A process for the preparation of the polyurethane dispersions according to the claims 1 to 7, characterized in that from components A), B), C), and D) in organic solution first an NCO and acid functional Prepared polyurethane prepolymer, then for at least 65, at most however, 105% of the acid groups added neutralizing agent and so he holding prepolymer is dispersed in or by water, then optionally Neutralizing agent up to the maximum amount of neutralization 105% added and stirred at 25 to 75 ° C until the under NCO Water reaction chain extension is complete, while wuh rend or after the dispersion or during or after the chain extensions tion reaction removed the organic solvent to an amount <2.5% becomes. 9. Varnishes for barrier layers, characterized in that they contain, in addition to the additives and auxiliaries customary in automotive coating, and optionally water for adjusting the spray viscosity

• a) 30 to 90% by weight polyurethane dispersion according to claim 1),
• b) 0 to 20% by weight of crosslinking agent,
• c) 5 to 90% by weight of pigments and / or fillers,
• d) 0 to 90% by weight of other binders.

10. Varnishes for barrier layers, characterized in that they contain, in addition to additives and auxiliaries customary in automotive coating, and optionally water for adjusting the spray viscosity

• a) 45 to 75% by weight polyurethane dispersion according to claim 1),
• b) 1 to 10% by weight of crosslinking agent,
• c) 10 to 60% by weight of pigments and / or fillers,
• d) 10 to 50% by weight of aqueous polyester or polyester-polyurethane solutions or dispersions.

11. Varnishes for barrier layers according to claims 9 and 10, characterized records that as a crosslinking agent reactive melamine resins and / or reactive contain blocked polyisocyanates and / or trisalkoxycarbonylaminotriazines are. 12. Varnishes for barrier layers according to claims 9 to 11, characterized net that they are using a pigment paste based on a water ver thinnable polyester resin have been produced, a reactive melamine resin as a crosslinking resin and contain a maximum of 2.5% organic solvents. 13. Use of an aqueous polyurethane dispersion according to claim 1 in com combination with one or more water-dispersible melamine resins and / or hydrophilized polyisocyanates and / or polyester and / or poly ester polyurethane resins for lightfast, physically fast drying be coatings with very good water resistance and high hardness-elasticity level, especially for barrier layers in automotive OEM painting. 14. Use of the dispersions according to the invention according to claims 1 to 7 in combination with polyurethane dispersions with faster physical Drying and high hard segment contents or / and reactive crosslinking resins for the production of reactive, d. H. in the temperature range from 90 to 120 ° C curable stoving fillers or single-layer paints e.g. B. for automotive paint tion or the plastic coating. 15. Use of the polyurethane dispersions according to claims 1 to 7 in Paints, coatings, sealants and adhesives.