DE10101103A1 - Preventing the yellowing of clear coats in multilayer color and effect paints, involves incorporation of blocked polyisocyanate in the primer, applying thermally curable clear coat and curing primer and clear coat - Google Patents

Abstract

Preventing the yellowing of clear coats involves (1) application of a pigmented primer paint containing an isocyanate reactive group and a blocked polyisocyanate as crosslinker, (2) application of a thermally curable clear coat, via epoxide groups or thermally cured via epoxide groups to give a clear coat layer and (3) mutual curing of the primer and clear coat. A process for retarding the yellowing of clear coats in multilayer color and effect paints deposited by a wet on wet process by: (1) application of at least one pigmented primer paint containing (A) at least one independently crosslinked primer binder and at least one isocyanate reactive group and (B) at least one blocked polyisocyanate as crosslinker, (AB) at least one self-crosslinked primer binder with at least one isocyanate reactive group and at least one blocked polyisocyanate group, to an optionally primed base, where at least one primer layer is the result; (2) application of at least one thermally curable clear coat, via epoxide groups or thermally cured via epoxide groups and with actinic radiation to the primer layer, to give at least one clear coat layer; and (3) mutual curing of the primer layer or layers and the clear coat layer or layers. The blocking agent is selected from: pyrazole, 2,2,4-triazole, and substituted 1,2,4-triazoles.

Description

The present invention relates to a new method for preventing the yellowing of clearcoats in color and / or effect multi-layer coatings, which by the wet-on-wet method

• A) Application of at least one pigmented basecoat containing
  • A) at least one externally crosslinking basecoat binder with at least one isocyanate-reactive group and
  • B) at least one blocked polyisocyanate as crosslinking agent and / or
  • C) at least one self-crosslinking basecoat binder with at least one isocyanate-reactive group and at least one blocked polyisocyanate group
  on a primed or unprimed substrate, which results in at least one basecoat layer,
• B) Application of at least one thermally via epoxy groups or thermally via Epoxy groups and clear lacquer curable with actinic radiation on the Basecoat, which results in at least one clearcoat, and
• C) joint hardening of the basecoat layer (s) and clearcoat layer (s)

are producible.

The production of color and effect multi-layer coatings after wet-on-wet The procedure is known. In this process, basecoats are used which are the usual applied with oximes such as butanone oxime (methyl ethyl ketoxime) Contain polyisocyanates as crosslinking agents, and clear coats that have epoxy groups  can be thermally cured, it can become a thermal cure Yellowing of the clearcoats come what the hues and the optical Overall impression (appearance) of the color and effect multi-layer coatings adversely changed. Then come the color and effect Multi-layer paintwork no longer for demanding and economically significant Applications such as the automotive OEM painting into consideration.

Speck-free, aqueous polyurethane dispersions are known from DE 199 12 896 A1. These can be used for the production of aqueous coating materials. To For this purpose you can use a variety of different crosslinking agents be mixed, u. a. also blocked polyisocyanates. The blocking agents can come from a total of 16 compound classes or mixtures of Blocking agents from different classes of compounds, three Mixtures are called expressis verbis. The aqueous coating materials can as water-based paints for the production of color and / or effect Multicoat paint systems can be used according to the wet-on-wet process. As Clearcoats can be used with all common and known clearcoats. a. also Powder slurry clear coats that are thermally cross-linked via epoxy groups. For the Examples based on the European patent application EP 0 574 417 A1 (PAT 91304) were carried out, however, in the waterborne basecoats as Crosslinking agent melamine resins and as two-component clear coats as clear coats used. Evidence of prevention of yellowing of over epoxy groups thermally hardened clear coats by using pyrazoles and / or Triazoles blocked polyisocyanates as crosslinking agents in the basecoats thus not given in the patent application.

In the unpublished German patent applications DE 199 48 004.4 and DE 10 03 9262.8 comparable waterborne basecoats are known. In the examples however, only melamine resins are used as crosslinking agents. The corresponding Waterborne basecoats become thermally curable with epoxy groups Powder slurry clear coats according to international patent application WO 96/32452 (DE 196 13 547 A1) overlaid, after which the two layers were baked together become. Evidence of prevention of yellowing of over epoxy groups  thermally hardened clear coats by using pyrazoles and / or Triazoles blocked polyisocyanates as crosslinking agents in the basecoats are used in the patent applications also not given.

In the unpublished German patent applications DE 199 53 203.6 and DE 199 53 445.4 become self-crosslinking waterborne basecoats based on polyurethanes described the blocked isocyanate groups and isocyanate-reactive functional groups contain. As the blocking agent, the blocking agent derived from the above German patent application DE 199 12 896 A1 cited are used. Butanone oxime (methyl ethyl ketoxime) is used with particular preference. The Corresponding water-based lacquer layers become thermal with the over epoxy groups curable powder slurry clearcoats according to international patent application WO 96/32452 (DE 196 13 547 A1), after which the two layers together be branded. Indications of prevention of yellowing from over Epoxy groups thermally hardened clear coats by using Pyrazoles and / or triazoles blocked polyisocyanates as crosslinking agents in the Basecoats are not given in the patent applications.

From DE 196 52 842 A1 a waterborne basecoat is known which contains an acrylate dispersion containing 30 to 60% by weight of C ₁ -C ₈ -alkyl (meth) acrylate-containing monomers and 30 to 60% by weight vinyl aromatic Monomers and 0.5 to 10 wt .-% (meth) acrylic acid and a rheology aid, which is a synthetic polymer with ionic and / or associative groups. Only melamine formaldehyde resins are disclosed as crosslinking agents. The waterborne basecoat and the waterborne basecoat produced therefrom have better compatibility with powder slurry clearcoats and with the clearcoats produced therefrom. There are no indications in the patent application of preventing the yellowing of clearcoats which have been thermally cured via epoxy groups by the use of polyisocyanates blocked with pyrazoles and / or triazoles as crosslinking agents in the basecoats.

Powder slurry clearcoats that are thermally cured via epoxy groups for example from patent applications DE 196 18 657 A1, WO 96/32452 or DE 198 41 408 A1  or the patents DE 196 13 547 C2 EP 0 820 490 B1. she are used to produce color and / or effect multi-layer coatings the wet-on-wet method, mainly for the overlaying of Waterborne basecoats based on polyesters, polyurethane resins and aminoplast resins are suitable. As a result, there is no evidence of these writings Prevention of yellowing of thermally hardened epoxy groups Clear coats by using blocked with pyrazoles and / or triazoles Derive polyisocyanates as crosslinking agents in the basecoats.

The use of polyisocyanates with 3,5-dimethylpyrazole and / or 1,2,4-triazole are blocked, for the production of clearcoats that do not or during thermal curing yellowing only to a very small extent are from the article by Th. Engbert, E. König and E. Jürgens, "Use of one-component stoving urethane coatings, an overview about systems with low thermal yellowing and low baking temperature ", color + lack, 102nd volume, issue 7, pages 51 to 58, 1996, and the international Patent application WO 95/06674 known. These clear coats are because of their material composition is not suitable to solve yellowing problems, which in the In connection with clear lacquers that can be hardened via epoxy groups.

From European patent application EP 0 159 117 B1 are electrocoat materials and Solid-color topcoats known as polyisocyanates blocked with substituted pyrazoles Contain crosslinking agents and binders containing active hydrogen atoms. A Use of these coating materials in a wet-on-wet process will not described.

Basecoats are known from German patent application DE 198 22 631 A1, which are associated with substituted pyrazoles blocked as polyisocyanate polyurethane polymers Crosslinking agents included. The clear coats with those from these basecoats Basecoats can be overcoated, are not closer specified.

European patent application EP 0 500 495 A2 describes adhesives and base colors known, the blocked with substituted pyrazoles polyisocyanates and polyamines as  Contain hardener. A wet-on-wet process using the thermosetting Compositions for the production of color and effect coating materials not apparent from the patent application.

The preparation of substituted pyrazoles is described in German patent application DE 198 31 656 A1 described. They serve as starting products for the production of dyes, Pharmaceuticals and in particular pesticides. 3,4-dimethylpyrazole and its Acid addition salts are nitrification inhibitors.

The object of the present invention is to provide a new method which the production of color and / or effect multi-layer coatings after the wet-on-wet process described at the outset without the yellowing of the clearcoats Change of their material composition effectively prevented, so that the resulting color and / or effect multicoat paint systems no disadvantage Color shifts and a loss of appearance, but still suffer for so technologically and aesthetically demanding and economically significant Applications such as automotive painting are used with advantage can.

Accordingly, the new process for preventing the yellowing of clearcoats in color and / or effect multi-coat coatings, which was carried out by the wet-on-wet process

• A) Application of at least one pigmented basecoat containing
  • A) at least one externally crosslinking basecoat binder with at least one isocyanate-reactive group and
  • B) at least one blocked polyisocyanate as crosslinking agent and / or
  • C) at least one self-crosslinking basecoat binder with at least one isocyanate-reactive group and at least one blocked polyisocyanate group,
    on a primed or unprimed substrate, which results in at least one basecoat layer,
• B) Application of at least one thermally via epoxy groups or thermally via Epoxy groups and clear lacquer curable with actinic radiation on the Basecoat, which results in at least one clearcoat, and
• C) joint hardening of the basecoat layer (s) and clearcoat layer (s)

are produced, where the blocking agent or agents from the group, consisting of pyrazole, substituted pyrazoles, 1,2,4-triazole and substituted 1,2,4- Triazoles, is or will be selected.

The following is the new method for preventing yellowing of Clear lacquers in color and / or effect multi-coat lacquers, which after the wet-on-wet process can be produced as the "process according to the invention" designated.

In view of the prior art, it was surprising and not for the person skilled in the art predictable that the use of the specially selected blocked polyisocyanates in the basecoats the problems of yellowing from over Epoxy groups thermally curing clearcoats could be solved. Because on and fit it would have been more likely that only measures aimed at the Straighten clear coats or clear coats as such, such as changing theirs material composition or the use of additives, the problem to be able to solve.

The method according to the invention is based on the application of a pigmented one Basecoat, especially a pigmented waterborne basecoat on a primed or unprimed substrate.

The basecoat contains at least one basecoat binder, which in the case of Waterborne basecoat is soluble or dispersible in water (to the term "binder"  see. Römpp Lexicon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, "Binders", pages 73 and 74).

The basecoat binders are thermal or thermal and with actinic radiation curable. The latter is also referred to by experts as "dual cure". Under actinic radiation is electromagnetic radiation, such as near infrared (NIR), visible light, UV radiation or X-rays, in particular UV radiation, and To understand corpuscular radiation like electron radiation.

The basecoat binders can be thermally crosslinking or self-crosslinking, especially cross-linking. Designated within the scope of the present invention the term "self-crosslinking" means the property of a binder with itself Crosslinking reactions. The prerequisite for this is that in the binders both types of complementary reactive functional groups are already contained, which are necessary for thermal crosslinking, in the present case the isocyanate-reactive ones Groups and the blocked polyisocyanate groups to be used according to the invention. On the other hand, binders are referred to as crosslinking in which the isocyanate-reactive groups, and the blocked to be used according to the invention Polyisocyanate groups are present in a hardener or crosslinking agent. Complementary on Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, "Hardening", pages 274 to 276, in particular page 275, below.

The basecoat binder contains at least one, preferably at least two and in particular at least three isocyanate-reactive groups. Examples of more suitable Isocyanate-reactive groups are hydroxyl groups, thiol groups, primary or secondary Amino groups or imino groups, of which the hydroxyl groups are preferably used become.

In the case of self-crosslinking basecoat binders, they also contain at least one, in particular at least two and in particular at least three of the Blocked polyisocyanate groups to be used according to the invention.  

In the case of the waterborne basecoats preferably used according to the invention, the basecoat binders contain functional groups which make them water-dispersible and / or water-soluble. These are either

• - functional groups by neutralizing agents and / or Quaternizing agents can be converted into cations, or
• - functional groups which are converted into anions by neutralizing agents can, and / or anionic groups and / or
• - Nonionic hydrophilic groups, especially poly (alkylene ether) groups.

Examples of suitable functional groups by neutralizing agents and / or Quaternizing agents that can be converted into cations are primary, secondary or tertiary amino groups, secondary sulfide groups or tertiary phosphine groups, especially tertiary amino groups or secondary sulfide groups.

Examples of suitable cationic groups are primary, secondary, tertiary or quaternary ammonium groups, tertiary sulfonium groups or quaternary Phosphonium groups, preferably quaternary ammonium groups or tertiary Sulfonium groups, but especially tertiary sulfonium groups.

Examples of suitable functional groups by neutralizing agents in anions can be transferred are carboxylic acid, sulfonic acid or phosphonic acid groups, especially carboxylic acid groups.

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

Examples of suitable neutralizing agents for functional convertible into cations Groups are inorganic and organic acids such as sulfuric acid, hydrochloric acid, Phosphoric acid, formic acid, acetic acid, lactic acid, dimethylolpropionic acid or Citric acid.  

Examples of suitable neutralizing agents for functional anions convertible into anions Groups are ammonia, amines or amino alcohols, such as. B. trimethylamine, Triethylamine, tributylamine, dibutylamine, dimethylaniline, diethylaniline, triphenylamine, Dimethylethanolamine, diethylethanolamine, methyldiethanolamine, 2- Aminomethylpropanol, dimethylisopropylamine, dimethylisopropanolamine or tri ethanolamine. Dimethylethanolamine and dibutylamine are preferred as neutralizing agents and / or triethylamine used.

The complementary reactive functional groups described above can according to the usual and known methods of polymer chemistry in the Basecoat binders can be installed. This can be done, for example, by installing Monomers which carry the corresponding reactive functional groups and / or with With the help of polymer-analogous reactions.

The content of the water-based paint binders is preferably the functional one Groups that make them water-dispersible and / or water-soluble, at 2 to 200 mEqu./100 g Water-based paint binders. The degree of neutralization is preferably 40 to 150%.

The dual-cure basecoat binders also contain a statistical average at least one, preferably at least two, group (s) with at least one bond activated by actinic radiation per molecule.

Under a bond that can be activated with actinic radiation is a bond understood that becomes reactive when irradiated with actinic radiation and with others activated bonds of their kind polymerization reactions and / or Crosslinking reactions, based on radical and / or ionic mechanisms expire. Examples of suitable bonds are carbon-hydrogen single bonds or carbon-carbon, carbon-oxygen, carbon-nitrogen, Carbon-phosphorus or carbon-silicon single bonds or Double bonds. Of these, the carbon-carbon double bonds are  particularly advantageous and are therefore very particularly preferred according to the invention used. For the sake of brevity, they are referred to below as "double bonds".

Accordingly, the group preferred according to the invention contains one double bond or two, three or four double bonds. More than one double bond can be used the double bonds are conjugated. According to the invention, however, it is advantageous if the Double bonds isolated, in particular each one individually, in the here in question standing group. According to the invention, it is particularly advantageous two especially one to use double bond.

On average, more than one group can be activated with actinic radiation applied per molecule, the groups are structurally different from each other or from same structure.

If they are structurally different from one another, this means within the scope of the present one Invention that two, three, four or more, but especially two, with actinic Radiation-activatable groups can be used, which differ from two, three, four or more, but in particular derive two monomer classes.

Examples of suitable groups are (meth) acrylate, ethacrylate, crotonate, cinnamate, Vinyl ether, vinyl ester, dicyclopentadienyl, norbornenyl, isoprenyl, isopropenyl, Allyl or butenyl groups; Dicyclopentadienyl, norbornenyl, isoprenyl, isopropenyl, Allyl or butenyl ether groups or dicyclopentadienyl, norbornenyl, isoprenyl, Isopropenyl, allyl or butenyl ester groups, but especially acrylate groups.

The groups are preferably via urethane, urea, allophanate, ester, ether and / or amide groups, but in particular via ester groups, to the respective Basic structures of the binders bound. This is usually done by usual and known polymer-analogous reactions such as the reaction of pendant Glycidyl groups with the olefinically unsaturated monomers described above, which contain an acid group, from pendant hydroxyl groups with the Halides of these monomers, containing hydroxyl groups with double bonds Isocyanates such as vinyl isocyanate, methacryloyl isocyanate and / or 1- (1-isocyanato-1-  methylethyl) -3- (1-methylethenyl) benzene (TMI® from CYTEC) or from Isocanate groups with the hydroxyl-containing monomers described above.

In the case of, for example, polyurethanes, the groups can be introduced with the aid of compounds which contain at least one, in particular one, of the isocyanate-reactive groups described above and at least one, in particular one, bond which can be activated with actinic radiation. Examples of suitable compounds of this type are

• - 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 3-hydroxybutyl, 4- Hydroxybutyl, bis (hydroxymethyl) cyclohexane, neopentyl glycol, Diethylene glycol, dipropylene glycol, dibutylene glycol, triethylene glycol acrylate, methacrylate, ethacrylate, crotonate, cinnamate, vinyl ether, allyl ether, -dicyclopentadienyl ether, -norbornenyl ether, -isoprenyl ether, -isopropenyl ether or -butenylether;
• - trimethylolpropane mono-, glycerol mono-, trimethylolethane mono-, Pentaerythritol mono-, homopentaerythritol mono-, pentaerythritol di-, Homopentaerythritol, trimethylolpropane, glycerol, trimethylolethane, Pentaerythritol tri or homopentaerythritol triacrylate, methacrylate, ethacrylate, crotonate, cinnamate, vinyl ether, allyl ether, dicyclopentadienyl ether, -norbornenyl ether, -isoprenyl ether, -isopropenyl ether or -butenyl ether; or
• - Reaction products from cyclic esters, such as. B. epsilon-caprolactone, and hydroxyl-containing monomers described above; or
• - 2-aminoethyl (meth) acrylate and / or 3-aminopropyl (meth) acrylate.

The basecoat binders are oligomeric and polymeric resins. Among oligomers are Resins understood that contain at least 2 to 15 monomer units in their molecule. In the context of the present invention, polymers are understood to be resins which contain at least 10 recurring monomer units in their molecule. additional  becomes these terms on Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, "Oligomere", page 425.

Examples of suitable basecoat binders are statistical, alternating and / or linear and / or branched and / or comb-like structures (Co) polymers of ethylenically unsaturated monomers, or polyaddition resins and / or polycondensation resins. These terms are supplemented by Römpp Lexicon of lacquers and printing inks, Georg Thieme Verlag, Stuttgart, New York, 1998, page 457, "Polyaddition" and "Polyaddition Resins (Polyadducts)", as well as pages 463 and 464, "Polycondensates", "Polycondensation" and "Polycondensation Resins", as well as pages 73 and 74, "Binder".

Examples of suitable (co) polymers are (meth) acrylate (co) polymers or partially saponified polyvinyl esters, especially (meth) acrylate copolymers, especially polyurethane modified (meth) acrylate copolymers.

Examples of suitable polyaddition resins and / or polycondensation resins are polyesters, Alkyds, polyurethanes, polylactones, polycarbonates, polyethers, epoxy resins, epoxy resin Amine adducts, polyureas, polyamides, polyimides, polyester-polyurethanes, polyether Polyurethanes or polyester-polyether-polyurethanes, but especially the polyurethanes, which are particularly preferably used as waterborne paint binders.

The preferred waterborne paint binders and waterborne basecoats are described in detail in patent applications and patent specifications EP 0 089 497 A1, EP 0 256 540 A1, EP 0 260 447 A1, EP 0 297 576 A1, WO 96/12747, EP 0 523 610 A1, EP 0 228 003 A1, EP 0 397 806 A1, EP 0 574 417 A1, EP 0 531 510 A1, EP 0 581 211 A1, EP 0 708 788 A1, EP 0 593 454 A1, DE-A-43 28 092 A1, EP 0 299 148 A1, EP 0 394 737 A1, EP 0 590 484 A1, EP 0 234 362 A1, EP 0 234 361 A1, EP 0 543 817 A1, WO 95/14721; EP 0 521 928 A1, EP 0 522 420 A1, EP 0 522 419 A1, EP 0 649 865 A1, EP 0 536 712 A1, EP 0 596 460 A1, EP 0 596 461 A1, EP 0 584 818 A1, EP 0 669 356 A1, EP 0 634 431 A1, EP 0 678 536 A1, EP 0 354 261 A1, EP 0 424 705 A1, WO 97/49745, WO 97/49747, EP 0 401 565 A1, EP 0 817 684, column 5, lines 31 to 45, DE 44 37 535 A1, page 7, line 8, to page 8, line 49, EP 0 787 195 A1, DE 40 05 961 A1, DE 41 10 520 A1, EP 0 752 455 B1,  DE 198 55 455 B1, DE 199 488 121 A1, DE 198 469 171 A1, EP 0 788 523 B1 or WO 95/12626.

The basecoat based on externally crosslinking basecoat binders contains at least a blocked polyisocyanate as crosslinking agent, at least according to the invention a blocking agent selected from the group consisting of pyrazole, unsubstituted pyrazoles, 1,2,4-triazole and substituted 1,2,4-triazoles becomes.

Examples of suitable substituted pyrazoles are those described in European Patent EP 0 159 117 B1, Page 2, line 35, to page 3, line 17, and claims 1 to 3, in the international patent application WO 95/06674, page 7, line 24, to page 8, line 15, in German patent application DE 198 22 631 A1, page 3, lines 56 to 65, in the European patent application EP 0 500 495 A1, page 4, line 27, to page 5, line 25, or in German patent application DE 198 31 656 A1, page 2, line 16, to page 5, Line 2. 3,5- and 3,4-dimethylpyrazole are preferred, in particular 3,5-dimethylpyrazole.

Examples of suitable substituted 1,2,4-triazoles are 3- or 5-methyl, 3- or 5-ethyl, 3- or 5-chloro, 3- or 5-bromo, 3- or 5-acetyl, 3,5-dimethyl, 3,5-dimethyl, 3,5- Dichloro, 3-methyl-5-ethyl, 3-methyl-5-acetyl or 3-methyl-5-chloro-1,2,4-triazole.

3,5-Dimethylpyrazole, 3,4-dimethylpyrazole and / or 1,2,4-triazole are preferred Blocking agents used.

Suitable polyisocyanates to be blocked contain on average at least 2.0, preferably more than 2.0 and in particular more than 3.0 isocyanate groups per molecule such as

• - Diisocyanates such as isophorone diisocyanate (= 5-isocyanato-1-isocyanatomethyl-1,3,3- trimethyl-cyclohexane), 5-isocyanato-1- (2-isocyanatoeth-1-yl) -1,3,3-trimethyl cyclohexane, 5-isocyanato-1- (3-isocyanatoprop-1-yl) -1,3,3-trimethyl-cyclohexane, 5- Isocyanato- (4-isocyanatobut-1-yl) -1,3,3-trimethyl-cyclohexane, 1-isocyanato-2- (3-  isocyanatoprop-1-yl) cyclohexane, 1-isocyanato-2- (3-isocyanatoeth-1- yl) cyclohexane, 1-isocyanato-2- (4-isocyanatobut-1-yl) cyclohexane, 1,2- Diisocyanatocyclobutane, 1,3-diisocyanatocyclobutane, 1,2- Diisocyanatocyclopentane, 1,3-diisocyanatocyclopentane, 1,2- Diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4- Diisocyanatocyclohexane, dicyclohexylmethane-2,4'-diisocyanate, tri methylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, Hexamethylene diisocyanate (HDI), ethyl ethylene diisocyanate, trimethylhexane diisocyanate, heptamethylene diisocyanate or diisocyanates derived from Dimer fatty acids, such as those available under the trade name DDI 1410 from the company Henkel sold and in the patents WO 97/49745 and WO 97/49747 are described, in particular 2-heptyl-3,4-bis (9-isocyanatononyl) -1-pentyl cyclohexane, or 1,2-, 1,4-or 1,3-bis (isocyanatomethyl) cyclohexane, 1,2-, 1,4- or 1,3-bis (2-isocyanatoeth-1-yl) cyclohexane, 1,3-bis (3-isocyanatoprop-1- yl) cyclohexane, 1,2-, 1,4- or 1,3-bis (4-isocyanatobut-1-yl) cyclohexane or liquid bis (4-isocyanatocyclohexyl) methane with a trans / trans content of up to 30 wt .-%, preferably 25 wt .-% and in particular 20 wt .-%, as in the Patent applications DE 44 14 032 A1, GB 1220717 A1, DE 16 18 795 A1 or DE 17 93 785 A1 is described, preferably isophorone diisocyanate, 5- Isocyanato-1- (2-isocyanatoeth-1-yl) -1,3,3-trimethylcyclohexane, 5-isocyanato-1- (3- isocyanatoprop-1-yl) -1,3,3-trimethyl-cyclohexane, 5-isocyanato- (4-isocyanatobut-1- yl) -1,3,3-trimethyl-cyclohexane, 1-isocyanato-2- (3-isocyanatoprop-1-yl) - cyclohexane, 1-isocyanato-2- (3-isocyanatoeth-1-yl) cyclohexane, 1-isocyanato-2- (4- isocyanatobut-1-yl) cyclohexane or HDI, in particular HDI;
• - Isocyanurate, biuret, allophanate, iminooxadiazinedione, urethane, urea Carbodiimide and / or uretdione polyisocyanates, which in Usual and known manner from the diisocyanates described above getting produced; Examples of suitable manufacturing processes and polyisocyanates are for example from the patents CA 2,163,591 A, US 4,419,513 A, US 4,454,317 A, EP 0 646 608 A, US 4,801,675 A, EP 0 183 976 A1, DE 40 15 155 A1, EP 0 303 150 A1, EP 0 496 208 A1, EP 0 524 500 A1, EP 0 566 037 A1,  US 5,258,482 A, US 5,290,902 A, EP 0 649 806 A1, DE 42 29 183 A1 or EP 0 531 820 A1 known; or
• - Dual-cure polyisocyanates made from the polyisocyanates described above and the compounds described above which contain at least one in particular one, isocyanate-reactive group (s) and at least one, in particular contain a bond which can be activated with actinic radiation, can be produced (see, for example, European patent application EP 0 928 800 A 1).

The self-crosslinking basecoat binders contain isocyanate groups with the Substituted and / or unsubstituted pyrazoles and / or described above 1,2,4-triazoles are blocked.

From a methodological point of view, the blocking of the polyisocyanates or those in the isocyanate groups present in self-crosslinking basecoat binders Special features, but takes place, for example, as in the European Patent application EP 0 159 117 B1, Example 1, page 4, lines 31 to 38, or Example 2, Page 4, lines 40 to 51 of European patent application EP 0 500 495 A2, example 1, Page 9, lines 34 to 54, example 2, page 9, line 55, to page 10, line 10, example 3, Page 10, lines 12 to 29, example 4, page 10, lines 31 to 44, example 5, page 10, line 46, to page 11, line 3, or Example 8, page 11, lines 41 to 56, or in the German Patent application DE 198 22 631 A1, example 1, page 4, lines 35 to 49, or example 2, Page 4, lines 51 to 65.

The content of the basecoats in the crosslinking agents described above Basecoat binders and those described above according to the invention using crosslinking agents or on the self-crosslinking basecoat binders can vary widely. The content is preferably, in each case based on the Solids of the basecoat, 10 to 90, preferably 15 to 80, particularly preferably 20 to 80, very particularly preferably 25 to 80 and in particular 30 to 80% by weight. Here will the weight ratio of externally crosslinking basecoat binders  Crosslinking agents are preferably chosen so that a ratio of isocyanate-reactive Groups of blocked isocyanate groups from 2: 1 to 1: 2, preferably 1.8: 1 to 1: 1.8; particularly preferably 1.6: 1 to 1: 1.6, very particularly preferably 1.4: 1 to 1: 1.4 and in particular 1.2: 1 to 1: 1.2 results. In the self-crosslinking basecoat binders the isocyanate-reactive groups and the blocked isocyanate groups are preferably in the proportions given above.

The basecoat also contains color and / or effect, fluorescent, electrical conductive and / or magnetically shielding pigments. He can also fillers and / or contain dyes soluble in water or in organic solvents.

Examples of suitable effect pigments are metal flake pigments such as commercially available Aluminum bronzes, aluminum bronzes chromated according to DE 36 36 183 A1, and commercially available stainless steel bronzes and non-metallic effect pigments, such as Pearlescent or interference pigments, platelet-shaped effect pigments based on Iron oxide, which has a color from pink to brown-red or liquid crystalline Effect pigments. In addition, varnishes and printing inks, Georg, are added to Römpp Lexikon Thieme Verlag, 1998, pages 176, "effect pigments" and pages 380 and 381 "metal oxide Mica pigments "to" metal pigments ", and the patent applications and patents DE 36 36 156 A1, DE 37 18 446 A1, DE 37 19 804 A1, DE 39 30 601 A1, EP 0 068 311 A 1, EP 0 264 843 A1, EP 0 265 820 A1, EP 0 283 852 A1, EP 0 293 746 A1, EP 0 417 567 A1, US 4,828,826 A or US 5,244,649 A.

Examples of suitable inorganic color pigments are white pigments such as Titanium dioxide, zinc white, zinc sulfide or lithopone; Black pigments such as carbon black, iron Manganese black or spinel black; Colored pigments such as chromium oxide, Chromium oxide hydrate green, cobalt green or ultramarine green, cobalt blue, ultramarine blue or Manganese blue, ultramarine violet or cobalt and manganese violet, iron oxide red, Cadmium sulfoselenide, molybdate red or ultramarine red; Iron oxide brown, mixed brown, Spinel and corundum phases or chrome orange; or iron oxide yellow, nickel titanium yellow, Chromium titanium yellow, cadmium sulfide, cadmium zinc sulfide, chrome yellow or bismuth vanadate.  

Examples of suitable organic color pigments are monoazo pigments, Bisazo pigments, anthraquinone pigments, benzimidazole pigments, quinacridone pigments, Quinophthalone pigments, diketopyrrolopyrrole pigments, dioxazine pigments, Indanthrone pigments, isoindoline pigments, isoindolinone pigments, azomethine pigments, Thioindigo pigments, metal complex pigments, perinone pigments, perylene pigments, Phthalocyanine pigments or aniline black.

In addition, Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, 1998, Pages 180 and 181, "Iron Blue Pigments" to "Iron Oxide Black", Pages 451 to 453 "Pigments" to "Pigment Volume Concentration", page 563 "Thioindigo Pigments", page 567 "Titanium dioxide pigments", pages 400 and 467, "Naturally occurring pigments", Page 459 "Polycyclic Pigments", page 52, "Azomethine Pigments", "Azo Pigments", and page 379, "Metal Complex Pigments".

Examples of fluorescent pigments (daylight pigments) are bis (azomethine) - Pigments.

Examples of suitable electrically conductive pigments are titanium dioxide / tin oxide pigments.

Examples of magnetically shielding pigments are pigments based on Iron oxides or chromium dioxide.

Examples of suitable metal powders are powders made of metals and metal alloys Aluminum, zinc, copper, bronze or brass.

Suitable soluble organic dyes are lightfast organic dyes with a little or no tendency to migrate from the powder slurry particles and the coatings made from it. The skilled worker can determine the tendency to migrate estimate based on his general knowledge and / or with the help of simple Determine preliminary tests, for example in the context of tinting tests.

Examples of suitable organic and inorganic fillers are chalk, calcium sulfates, Barium sulfate, silicates such as talc, mica or kaolin, silicas, oxides such as  Aluminum hydroxide or magnesium hydroxide or organic fillers such as Plastic powder, in particular made of polylamide or polyacrylonitrile. In addition, on Römpp Lexicon Lacke und Druckfarben, Georg Thieme Verlag, 1998, pages 250ff., "Fillers" referenced.

Examples of suitable transparent fillers are those based on silicon dioxide, Aluminum oxide or zirconium oxide, but in particular nanoparticles on this basis.

In addition, the basecoats can also be conventional and known additives such as reactive diluents curable thermally and / or with actinic radiation, other Crosslinking agents for thermal curing, which differ from those of the invention use differentiate, low-boiling organic solvents and high-boiling organic solvents ("long solvents"), water, UV absorbers, light stabilizers, Radical scavengers, thermolabile free radical initiators, catalysts for the thermal Crosslinking, photoinitiators, deaerating agents, slip additives, polymerization inhibitors, Defoamers, emulsifiers, wetting and diperging agents, adhesion promoters, leveling agents, film-forming aids, rheology-controlling additives (thickeners), flame retardants, Drying agents, drying agents, skin preventives, corrosion inhibitors, waxes and Contain matting agents in usual and known amounts. Further examples suitable paint additives are described in the textbook "Paint Additives" by Johan Bieleman, Wiley-VCH, Weinheim, New York, 1998.

The production of the basecoats has no special features, but takes place in the usual way and in a known manner by mixing the components described above in suitable mixing units, such as stirred kettles, dissolvers, agitator mills, static Mixers, gear rim dispersers or extruders, according to those used to manufacture the appropriate basecoats.

All primed and unprimed come for the process according to the invention Substrates into consideration, such as those used in industrial painting, including the coil Coating and container coating, furniture painting or coating of Buildings can be used indoors and outdoors. The special advantages of However, the method according to the invention occurs primarily in the painting of  Automotive bodies in series painting or refinishing, in particular in the serial painting. Accordingly, it is the most preferred Substrates for automobile bodies.

The steel automobile bodies used in the method according to the invention usually have a cathodically deposited and thermally hardened Electrocoating as a primer. But you can also use a cathodic one have deposited electrodeposition coating, which is not thermally hardened, but is only dried or partially hardened. The electro dip painting or the Electrocoating layer can be covered with a filler, either on its own cured alone or together with the electrocoat layer (wet-on-wet Method). The overlay with a filler takes place especially in the areas that a strong mechanical stress, such as by stone chips, are exposed.

Examples of suitable cathodic electrocoating materials and, if appropriate, examples of wet-on-wet Methods are known from Japanese Patent Application 1975-142501 (Japanese Publication JP 52-065534 A2, Chemical Abstracts Unit No. 87: 137427) or the patents US 4,375,498 A1, US 4,537,926 A1, US 4,761,212 A1, EP 0 529 335 A1, DE 41 25 459 A1, EP 0 595 186 A1, EP 0 074 634 A1, EP 0 505 445 A1, DE 42 35 778 A1, EP 0 646 420 A1, EP 0 639 660 A1, EP 0 817 648 A1, DE 195 12 017 C1, EP 0 192 113 A2, DE 41 26 476 A1 or WO 98/07794 known.

Likewise, suitable fillers, especially aqueous fillers, are also available as Rockfall protection primers or functional layers are designated, for example from the patents US 4,537,926 A1, EP 0 529 335 A1, EP 0 595 186 A1, EP 0 639 660 A1, DE 44 38 504 A1, DE 43 37 961 A1, WO 89/10387, US 4,450,200 A1, US 4,614,683 A1 or WO 490/26827 known.

These fillers can also be applied to the burned-in electrocoat are then pre-dried or partially thermally hardened. At this Variant of the method according to the invention they are then together with those on the  Filler coats applied basecoat coats and clearcoat co-hardened (Extended wet-on-wet process).

Provided that electrocoat layers and filler layers are also used their layer thicknesses in the case of electrocoating at 5 to 50, preferably 6 to 45, particularly preferably 7 to 40 and in particular 8 to 35 microns and in the case of Filler coating at 10 to 150, preferably 10 to 120, particularly preferably 10 to 100 and in particular 10 to 90 µm.

The interior of the car body can also be applied to the filler paint or Stone chip protection primer can be dispensed with because i. a. no danger of a mechanical stress exists.

If the automobile body consists essentially of aluminum, one is usually Layer of anodized aluminum applied as a primer.

Primed or non-primed plastics are also suitable as substrates are dimensionally stable at the baking temperatures used, such as Polyphenylene ether, SMC, BMC or polyether sulfone or ketone. The plastics can of course also polymer blends, modified plastics or fiber-reinforced Be plastics. In the case of non-functionalized and / or non-polar These plastics can be substrate surfaces in a known manner before coating pretreatment, such as with a plasma or with flame, or with be provided with a hydro primer.

The application of the basecoats can be done by all common application methods, such as. B. Spraying, knife coating, brushing, pouring, dipping, watering, trickling or rolling. The substrate to be coated can rest as such, the Application device or system is moved. However, what is to be coated can also be Substrate, in particular a coil, are moved, the application system relative to Substrate rests or is moved in a suitable manner.  

Spray application methods, such as, for example, are preferably used Compressed air spraying, airless spraying, high rotation, electrostatic spray application (ESTA), possibly connected with hot spray application such as hot air Hot spraying. The applications can be used at temperatures of max. 70 to 80 ° C be carried out so that suitable application viscosities are achieved without a change in the briefly acting thermal load or Damage to the coating material of the invention and, if appropriate, its reprocessing overspray to be reprocessed. This is how hot spraying can be designed be that the coating material is heated only very briefly in or just before the spray nozzle becomes.

The spray booth used for the application can be used, for example, with a optionally temperature-controlled circulation can be operated with a suitable Absorbent medium for the overspray, e.g. B. the respective applied basecoat itself, is operated.

If the basecoat is curable thermally and with actinic radiation, the application becomes preferred for illumination with visible light with a wavelength of over 550 nm or carried out in the dark. This will result in a material change or Damage to the dual-cure basecoat and overspray avoided.

In general, in the process according to the invention the basecoats are mixed in one Applied wet film thickness that after curing, layers with that for your Functions necessary and advantageous layer thicknesses result; preferably lie it at 5 to 50, preferably 6 to 40, particularly preferably 7 to 30 and in particular 8 to 25 µm.

The basecoat film is preferably dried before the clearcoat is applied, whereby it is not or only partially hardened.

In the method according to the invention, the second essential method step at least one, in particular one thermally via epoxy groups or thermally via Epoxy groups and clear coat curable with actinic radiation to the above  Applied basecoat layer applied, preferably the above described methods are used. Preferably, the Wet layer thickness of the clear lacquer layer is adjusted so that clear coats after curing a layer thickness of 10 to 100, preferably 15 to 80, particularly preferably 20 to 70 and in particular 25 to 60 microns result.

The clearcoats to be used in the process according to the invention are customary and known aqueous or conventional clear coats, essentially water and solvent-free liquid clear coats (100% systems), essentially water and Solvent-free powder clearcoats or powder clearcoat dispersions, which are also available from experts are called powder slurries. The powder slurries are preferably used.

As is known, these clearcoats contain oligomers and / or epoxy groups polymeric clear coat binders and low molecular weight carboxyl groups Clearcoat crosslinking agent. Or they contain low molecular weight epoxy groups Clear coating crosslinking agents and carboxyl group-containing oligomers and / or polymers Clearcoat binder. The clear coat binders and / or crosslinking agents can moreover, on average, at least one, preferably at least two, of the Group (s) described above with at least one with actinic radiation contain activatable bond per molecule.

Examples of suitable powder slurries as well as the processes for their production and their application properties are described in detail in the

• - international patent application WO 99/50359, page 3, line 8, line 22, i. V. m. Example "A. Preparation of Powdered Resin", line 22, line 22, to page 23, line 1, example "B. Production of the powder coating", page 23, lines 3 to 13, Example "C. Non-ionic stabilized powder slurry", page 23, line 15, to page 24, line 7, and example "2nd embodiment", page 24, lines 9 to 23;
• - German patent application DE 198 41 408 A1, page 2, line 32, to page 7, line 26, i. V. m. Example 1, page 7, line 28, to page 10, line 2;  
• - German patent application DE 196 13 547 A1, column 1, line 48, to column 5, Line 33, i. V. m. the examples "1. Production of the acrylic resin", column 5, Lines 37 to 47, "2. Production of the powder coating" Column 5, Lines 49 to 58, "3. Preparation of the dispersion ", column 5, line 60, to column 6, line 9," 4. Application of the dispersion ", column 6, lines 11 to 22;
• - German patent application DE 196 18 657 A1, column 1, line 53, to column 6, Page 5, i. V. m. the example "example of the production of a powder slurry", Column 6, lines 7 to 45;
• - German patent application DE 196 52 813 A1, column 3, line 10, up to column 9, Line 12; or in the
• - German patent application DE 195 40 977 A1, "Task and solution", column 2, Line 49 to column 3, line 49, "Implementation of the Invention", "Component of aqueous powder coating dispersion ", column 3, line 61 to column 6, line 54," Die Preparation of the aqueous powder coating dispersion ", column 6, line 56, to column 8, Line 10, "Applications of the aqueous Powder coating dispersions ", column 8, line 13 to column 9; line 10, in conjunction with the Example "Preparation of the powder coating dispersion according to the invention", column 9, Lines 12 to 59;

described.

After the application of the clear coat, the basecoat layers and the resulting Clear coat together thermally or thermally and with actinic radiation hardened (wet-on-wet method).

The hardening can take place after a certain rest period. It can last for 30 s to 2 h, preferably 1 min to 1 h and in particular 1 min to 30 min. The Rest time is used, for example, for the course and for degassing the applied layers or to evaporate volatile components such as solvents or water. The Rest time can be supported and / or by using elevated temperatures up to 80 ° C  be shortened, provided there is no damage or changes to the applied Shifts occur, such as early full networking.

The thermal hardening has no special features in terms of method, but takes place according to the usual and known methods such as heating in a forced air oven or Irradiate with IR lamps. The hardening can also be carried out in stages. she preferably takes place at temperatures of 60 to 180 ° C, preferably for a period of time from 1 min to 2 h, particularly preferably 2 min to 1 h and in particular 3 min to 45 min.

Even curing with actinic radiation has no special methodological features, but takes place with the help of electromagnetic radiation such as near infrared, visible Light, UV radiation or X-rays, in particular UV radiation, and / or Corpuscular radiation like electron radiation. UV radiation is preferred applied.

In the case of electron beams, work is preferably carried out under an inert gas atmosphere. This can be done directly by adding carbon dioxide and / or nitrogen, for example the surface of the applied layers can be guaranteed. Even in the case of Curing with UV radiation can, in order to avoid the formation of ozone, under inert gas be worked.

For curing with actinic radiation, the usual and well-known Radiation sources and optical auxiliary measures applied. Examples of more suitable Radiation sources are high or low pressure mercury vapor lamps, which optionally doped with lead to open a radiation window up to 405 nm, or Electron beam sources. Further examples of suitable radiation sources are given in the German patent application DE 198 18 735 A1, column 10, lines 31 to 61. Their arrangement is known in principle and can take into account the conditions of the workpiece and the process parameters are adjusted. For complicated shaped workpieces like Automobile bodies can be the areas not accessible to direct radiation (Shadow areas) such as cavities, folds and other design-related Undercuts with spot, small area or all-round emitters connected with one  automatic moving device for the irradiation of cavities or edges, be cured.

The facilities and conditions of these hardening methods are also described in R. Holmes, U. V. and E. B. Curing, Formulations for Printing Inks, Coatings and Paints, SITA Technology, Academic Press, London, United Kindom, 1984.

The hardening can take place in stages, i. H. by multiple exposure or Irradiation with actinic radiation. This can also take place alternately, i. that is for example, alternately cured with UV radiation and electron radiation.

Thermal curing and curing with actinic radiation can be carried out simultaneously or can be used alternately. The two hardening methods will alternate used, for example, can begin with actinic radiation and end with thermal curing. In other cases, it can prove to be beneficial prove to start and end with curing with actinic radiation. The person skilled in the art can determine the hardening method which is appropriate for the individual case The most advantageous is due to his general specialist knowledge if necessary under Determine simple preliminary tests.

The method according to the invention supplies color and / or by the wet-on-wet method effect-giving multi-layer coatings, the clearcoats of which no longer yellowing have so that they have no adverse hue shifts and no loss of Suffering from appearance and therefore for such technologically and aesthetically demanding and economically important uses such as automotive painting Advantage can be used.

Examples and comparative tests Production Example 1 The production of a polyester polyol

It became a polyester polyol from 39.487 parts by weight of a polymeric fatty acid (Dimer content at least 98% by weight, trimere content at most 2.0% by weight, Monomer content at most traces; Pripol® 1013), 21.739 parts by weight of 1,6-hexanediol and 11.689 parts by weight of isophthalic acid (99 percent) in 25.985 parts by weight Methyl ethyl ketone in the presence of 1.1 parts by weight of cyclohexane as an entrainer manufactured. The solids content was 72% by weight.

Preparation example 2 The production of an olefinically unsaturated polyurethane dispersion

23.738 were used to prepare the olefinically unsaturated polyurethane dispersion Parts by weight of the polyester polyol of Preparation Example 1, 8.808 parts by weight Isophorone diisocyanate, 0.722 parts by weight of trimethylolpropane monoallyl ether and 2.021 Parts by weight of dimethylolpropionic acid in 1.444 parts by weight of methyl ethyl ketone and 4,332 parts by weight of N-methylpyrrolidone reacted with one another. The resulting Polyurethane was neutralized with 1.444 parts by weight of triethylamine and in 53.846 Parts by weight of deionized water and 0.733 parts by weight of aminoethylethanolamine dispersed. The methyl ethyl ketone was removed by vacuum distillation. The the resulting dispersion was mixed with 2.912 parts by weight of deionized water.

Preparation example 3 The production of an acrylated polyurethane dispersion

In a steel boiler, equipped with monomer feed, initiator feed, thermometer, Oil heating and reflux condenser were 46.32 parts by weight of the olefinically unsaturated Polyurethane dispersion of preparation example 2 and 26.367 parts by weight of deionized Submitted water and heated to 110 ° C with stirring.

Then a solution of 0.263 parts by weight of t-butyl perethylhexanoate in 3.5 Parts by weight of methoxypropanol at such a rate evenly added that the addition was complete after 5.5 hours.  

With the start of initiator addition, a mixture of 5.005 Parts by weight of styrene, 5.005 parts by weight of methyl methacrylate, 3.745 parts by weight Butyl acrylate, 3.745 parts by weight of hydroxyethyl methacrylate, 5.150 parts by weight of olefinically unsaturated polyurethane dispersion of preparation example 2 and 0.5 Parts by weight of deionized water started. The mixture was made with one Speed evenly added that the addition is completed in five hours was. After the initiator solution had been added completely, the Reaction temperature kept at 110 ° C for one hour. Then was the acrylated polyurethane dispersion with 0.4 parts by weight of methoxypropanol added.

Preparation example 4 The production of a rubbing resin

The rubbing resin was analogous to that in German patent application DE 44 37 535 A1 Page 7, lines 36 to 53, "C Preparation of an Acrylated Polyurethane Dispersion", specified regulation produced.

For this purpose, a polyester diol of 29.41 parts by weight was first Neopentyl glycol, 16.698 parts by weight of 1,6-hexanediol and 44.198 parts by weight Adipic acid in 8.834 parts by weight of methyl isobutyl ketone and 0.860 parts by weight Cyclohexane produced as an entrainer.

Analogous to the above specification, a polyurethane made from 1.875 Parts by weight of neopentyl glycol, 17.398 parts by weight of the polyester diol solution, 0.6 Parts by weight of trimethylolpropane monoallyl ether and 12.823 parts by weight Isophorone diisocyanate in the presence of 0.010 part by weight of dibutyltin dilaurate and 20.527 parts by weight of methyl isobutyl ketone and 3.056 Parts by weight of trimethylolpropane extended chain.  

The resulting polyurethane solution was used as a template for the copolymerization of a Monomer mixture of 14.041 parts by weight of n-butyl acrylate, 14.041 parts by weight Methyl methacrylate, 3.359 parts by weight of hydroxypropyl methacrylate and 2.626 Parts by weight of acrylic acid are used. A mixture of 6.722 was used as the initiator solution Parts by weight of methyl isobutyl ketone and 1.022 parts by weight of tert-butylperoxy-2- ethylhexanoate.

51.840 parts by weight of the resulting solution of the acrylated polyurethane were mixed with Dimethylethanolamine in 47.051 parts by weight of water, after which the Methyl isobutyl ketone was distilled off. The resulting acrylated Polyurethane dispersion had a solids content of 44% by weight.

Preparation example 5 The production of a white paste

To produce the white paste, 29.3 parts by weight of the rubbing resin Preparation Example 4, 9.8 parts by weight of deionized water, 50.6 parts by weight Titanium dioxide pigment (titanium rutile), 0.95 parts by weight of Aerosil® R 972 and 0.35 Parts by weight of Aerosil® R 805 (fumed silica from Degussa), 0.3 Parts by weight of Agitan® 281 (100%) from Münzing Chemie, 2.25 parts by weight Lusolvan® FBH (isobutyl ester of a dicarboxylic acid mixture from BASF Aktiengesellschaft), Disperbyk® 184 from Byk Chemie (52 percent in Dipropylene glycol monomethyl ether / propylene glycol 2: 1) and 4.4 parts by weight Surfynol® 104 (2,4,7,9-tetramethyl-5-decin-4,7-diol, 52% in butyl glycol, from Air Products) mixed together. The resulting mixture was on a Agitator mill ground to a grain size of 15 to 5 µm according to Hegmann. The resulting white paste was adjusted to a pH of 7.6 to 7.8.

Preparation example 6 Production of an aerosil paste

To produce the aerosil paste, 45.9 parts by weight of the rubbing resin Preparation example 4, 0.3 part by weight of Agitan® 281 (100%), 0.4 part by weight Surfynol® 104, 7.4 parts by weight of butyl glycol, 6.9 parts by weight of Aerosil® R 805 and 0.25 Parts by weight of aqueous ammonia (15%) mixed together. The resulting one Mixing was carried out on an agitator mill to a grain size according to Hegmann of 15 ground to 5.0 µm. The resulting aerosil paste was adjusted to a pH of 7.6 to 8.0 set.

Manufacturing Examples 7 to 9 The production of waterborne basecoats to be used according to the invention (Preparation examples 7 and 8) and one not to be used according to the invention Waterborne basecoat (preparation example 9)

The waterborne basecoat materials from Preparation Examples 7 to 9 were obtained from those in Table 1 specified starting products manufactured. The starting products in the mixed in the order given in Table 1.

Table 1

The Production of the Waterborne Basecoats to be Used According to the Invention (Examples 7 and 8) and of the Waterborne Basecoat to be Used According to the Invention (Manufacturing Example 9)

Examples 1 and 2 and comparative experiment V1 The production of multi-layer coatings according to the invention Method (Examples 1 and 2) and by methods not according to the invention (Comparative experiments V1 to V4)

For example 1 and comparative experiment V2, the waterborne basecoat of Manufacturing example 7 used.

For example 2 and comparative experiment V3, the waterborne basecoat of Manufacturing example 8 used.

For the comparative test V1 and the comparative test V4, the water-based paint was used of preparation example 9 used.

For the test of the yellowing resistance of the multi-layer coatings, in Test boards measuring 30 × 70 cm are produced in a customary and known manner. For this were steel sheets (body panels), with a usual and known, cathodic deposited and baked electrodeposition coating had been coated with coated with a commercially available filler from BASF Coatings AG, after which the resulting filler layer for five minutes at 20 ° C and a relative Air humidity of 65% and vented in a forced air oven for 30 minutes 140 ° C was baked.

After the test panels had cooled to 20 ° C, the waterborne basecoats were applied in two Spray coats applied. The first order is made using ESTA (bell speed: 45,000 rpm. Steering air: 120 Nl / min. Voltage: 65 KV; Distance: 0.25 m; Outflow amount of paint: 170 ml / min), corresponding to a dry film thickness of 8 to 10 µm. The second job  was carried out pneumatically (distance: 0.32 m; paint flow rate: 540 ml / min. Quantity: 300 Nl / min. Atomizing air pressure: 4.8 bar; Horn air pressure: 5.2 bar; Hornluft- Quantity: 395 Nl / min), corresponding to a dry film thickness of 4 to 6 µm. The Waterborne basecoats were applied after the first and second coats, respectively flashed off for two minutes.

After application, the waterborne basecoats were left at 80 ° C for 15 minutes dried, cooled and in accordance with a customary and known powder slurry clearcoat German patent application DE 198 41 408 A1, page 7, lines 28 to 39, page 7, Lines 41 to 49, page 7, line 65, to page 8, page 2, and page 8, lines 4 to 20, (Clear powder coating 2.2 according to the invention and clear powder coating slurry 3.2 according to the invention) coated (Examples 1 and 2 and Comparative Experiment V1).

After ten minutes of predrying at 40 ° C., the water-based lacquer layers and Clear coats baked together at 145 ° C for 30 minutes. The According to this, clear lacquer layers had a dry layer thickness of 45 µm.

For purposes of comparing yellowing resistance, Examples 1 and 2 were and the comparison experiment V1 is repeated, except that instead of the powder slurry clearcoat commercially available two-component clearcoat from BASF Coatings AG was not prone to yellowing (comparative tests V2 to V4).

To evaluate the color change due to yellowing, the yellowness index according to DIN 6167 was the difference between the yellowness values (average of three measurements in each case) of the multi-layer coatings

• - Example 1 and comparative experiment V2: Δb * = 0.2;
• - Example 2 and comparative experiment V3: Δb * = 0.1; and
• - Comparative test V1 and comparative test V4: Δb * = 0.5;

determined. The comparison shows that those produced in the procedure according to the invention Multi-layer coatings of Examples 1 and 2 have a significantly lower tendency to Yellowing than that produced in a procedure not according to the invention Multi-layer painting of comparative test V1.

Claims (12)

1. A method for preventing the yellowing of clearcoats in color and / or effect-giving multi-layer coatings, by the wet-on-wet method

• A) Application of at least one pigmented basecoat containing
  • A) at least one externally crosslinking basecoat binder with at least one isocyanate-reactive group and
  • B) at least one blocked polyisocyanate as crosslinking agent
  • C) at least one self-crosslinking basecoat binder with at least one isocyanate-reactive group and at least one blocked polyisocyanate group,
  on a primed or unprimed substrate, which results in at least one basecoat layer,
• B) application of at least one clearcoat curable thermally via epoxy groups or thermally via epoxy groups and with actinic radiation to the basecoat film, resulting in at least one clearcoat film, and
• C) joint hardening of the basecoat layer (s) and clearcoat layer (s)

Are produced, characterized in that the blocking agent or blocking agents is or are selected from the group consisting of pyrazole, substituted pyrazoles, 1,2,4-triazole and substituted 1,2,4-triazoles. 2. The method according to claim 1, characterized in that the to Epoxy groups complementary reactive functional groups Are carboxyl groups. 3. The method according to claim 1 or 2, characterized in that

• a) the epoxy groups in oligomeric and / or polymeric clear coat binders and the carboxyl groups in low molecular weight clear coat crosslinking agents or alternatively
• b) the epoxy groups are present in low molecular weight clear coat crosslinking agents and the carboxyl groups are in oligomeric and / or polymeric clear coat binders.

4. The method according to any one of claims 1 to 3, characterized in that the Clear coat binders and / or crosslinking agents and / or the basecoat binders and / or crosslinking agents with at least one reactive functional group contain at least one bond that can be activated with actinic radiation. 5. The method according to any one of claims 1 to 4, characterized in that the with bonds activatable from actinic radiation from the group consisting of Carbon-hydrogen single bonds or carbon-carbon, Carbon-oxygen, carbon-nitrogen, carbon-phosphorus or Carbon-silicon single bonds or double bonds selected become. 6. The method according to claim 5, characterized in that carbon Double carbon bonds ("double bonds") can be used.   7. The method according to claim 7, characterized in that the double bonds as (Meth) acrylate, ethacrylate, crotonate, cinnamate, vinyl ether, vinyl ester, Ethenylarylene, dicyclopentadienyl, norbomenyl, isoprenyl, isoprenyl, Isopropenyl, allyl or butenyl groups; Ethenylarylene, dicyclopentadienyl, Norbornenyl, isoprenyl, isopropenyl, allyl or butenyl ether groups or Ethenylarylene, dicyclopentadienyl, norbornenyl, isoprenyl, isopropenyl, allyl or butenyl ester groups are present. 8. The method according to any one of claims 1 to 7, characterized in that the Clear coat a liquid aqueous or conventional clear coat, a liquid, in essential water- and solvent-free clear coat (100% system) Powder clearcoat or a powder slurry clearcoat. 9. The method according to claim 8, characterized in that the clear coat Powder slurry clearcoat is. 10. The method according to any one of claims 1 to 9, characterized in that the Basecoat is a waterborne basecoat. 11. The method according to any one of claims 1 to 10, characterized in that the isocyanate-reactive functional groups from the group consisting of Hydroxyl, thiol, imino and primary and secondary amino groups, to be selected. 12. The method according to any one of claims 1 to 11, characterized in that the Polyisocyanates from the group consisting of aliphatic, cycloaliphatic and aliphatic cycloaliphatic polyisocyanates.