CA2443615C - Structurally viscose clear lacquer slurry - Google Patents

Abstract

The invention relates to structurally viscose clear lacquer slurry containin g strong and/or highly viscose particles which are dimensionally stable when stored or used, and at least one water-soluble salt, preferably 0.1 to 50 mm ol per 1000 g water, said salt being residue-free or essentially residue-free decomposable. The invention also relates to a method for the production and use thereof.

Description

STRUCTURALLY VISCOSE CLEAR LACQUER SLURRY

The present invention relates to a novel pseudoplastic clearcoat slurry. The present invention also relates to a novel process for preparing pseudoplastic clearcoat slurries. The present invention additionally relates to the use of the novel pseudoplastic clearcoat slurry for automotive OEM finishing, automotive refinish, the interior and exterior painting of buildings, the coating of doors, windows and furriiture, and industrial coating, including coil coating, container coating, the coating of small parts, the impregnation and/or co.ating of electrical components,' and the coating of white goods. The' present invention relates not least to the use-of the novel clearcoat slurries as adhesives and sealing compounds for producing adhesive films and seals, especiall,y in the aforementioned fields.

Thermally curable clearcoat slurries which are produced by means of grinding and dispersing techniques are known, for example, from the German patent application DE 195 40 977 Al. Similarly, clearcoat slurries curable with actinic radiation, which are produced by means of grinding and dispersing techniq-aes, are ]~nown from the German patent application DE 198 35 206 Al.

Here and below, actinic radiation means electromagnetic radiati on, such as near infrared (NIR), vi sible light, UV radiation or x-rays, especially W radiation, and corpuscular radiation, such as electron beams.

Thermally curable clearcoat slurries which are produced by means of secondary dispersion techniques are known, for example, from the German patent DE 198 41 842 C2, from the German patent application no. DE 196 17 086 Al or from the European patent application EP 0 899 282 Al.

For example, the clearcoat slurries known from the German patent DE 198 41 842 C2 are free from organic solvents and external emulsif:ers and contain solid spherical particles with an average size oi from 0.8 to um and a maximum size of 30 um, and have an ion-forming group content of from 0.05 to 1 meq/g and a neutralizing agent content of from 0.05 to 1 meq/g.
Particles of clearcoat slurry known in the art have for example an average size of from 1.0 to 20 pm, at least 99% of the particles having a size <_ 30 pm.
They contain as binder at least one polyol having an OH number > 110 mg KOH/g, which has potentially ionic groups. The clearcoat slurry contains an overall amount of potentially ionic groups of from 0.05 to 1 meq%g solids- and, at a degree of neutralization of not more-than 50%, contains an amount of ionic groups produced by, neutralizing the poten=tially ionic groups which is from 0.005 to 0.1 meq/g solids.

These known pseudoplastic clearcoat slurries have a viscosity of (i) from 50 to 1 000 mPas at a shear rate of 1 000 s-1, (ii) from 150 to 8 000 mPas at a shear rate of 10 s-1, and (iii) from 180 to 12 000 mPas at'a shear rate of 1 s-l.
15.

In the secondary dispersion technique, the clearcoat slurries are prepared by 1) emulsifying an organic solutioi3 comprising binder ~ 20 and crosslinking agent iri water or an 'aqueous phase, to give an emulsion of the oiI-in=water type , .

2) removing the organic solvent or the organic 25 solvents, and 3) replacing by water some or all of the solvent removed, to give a clearcoat slurry. comprising solid spherical particles, where 4) additionally, at least one ionic, especially anionic, thickener and at least one nonionic associative thickener are added to the clearcoat s?urries.

The German patent application DE 199 08 018 Al discloses clearcoat slurries curable thermally and with actinic radiation - dual-cure clearcoat slurries -which are prepared by the secondai-y dispersion technique.

The German patent application DE 199 59 923 A1 discloses clearcoat slurries prepared by a primary dispersion technique. With this technique, the powder clearcoat particles are prepared directly in a micro-emulsion or a miniemulsion by means of controlled free-radical copolymerization of olefinically unsaturated monomers.

The international patent applications WO 97/45476, WO 98/45356 or WO
00/17256 and the American patent US 4,056,653 A, describe clearcoat slurries curable thermally or both thermally and with actinic radiation and which are prepared with the aid of melt emulsification techniques.

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The known. clearcoat slurries= have very good performance properties and- are especially suitable for the production of clearcoats for high-grade multicoat color and./or. effeet paint systems, as are. used, for example, to coat automobiles. In the course of the production of these multicoat color and/or effect paint systems by the wet-on-wet technique, the clearcoat slurries may be used in combination with any of a very wide variety of aqueous base. coat materials, without any deleterious effects as a result, such as mud cracking.

The known clearcoat slurries do, however, have the disadvantage that they sometimes give clearcoats having microdefects. These microdefects are manifested in particular on black basecoats as optical effects which are reminiscent of metallic effects. These- optical effects are also referred to as "starry sky".

It is an object of the present invention to provide a novel clearcoat slurry which no longer has the disadvantages of the prior art but which instead retains all of the advantages of the known clearcoat slurries while giving clearcoats which no longer have any microdefects, in particular no disruptive optical effects, such as "starry sky".

. . . , The invention accordingly provides the novel pseudoplastic clearcoat slurry comprising solid and/or highly viscous particles which are dimensionally stable under storage and application conditions and at least one water-soluble salt which can be decomposed without residue or substantially without residue.

The present invention, as claimed, is more particularly directed to a pseudoplastic clearcoat slurry comprising an aqueous phase comprising water, particles that are dimensionally stable under storage and application conditions, and at least one water-soluble salt, wherein the salt can be decomposed without residue into decomposition products, and wherein the salt is present in an amount from 0.1 to 50 mmol per 1 000 g of water.

=n the text below, the novel pseudoplastic clearcoat slurry is referred to as the "slurry of the invention".
Further subject matter of the invention will emerge from the description.

in the light of the prior art it was surprising for the skilled worker and unforeseeable that the object on which the present invention is based could be achieved by adding at least one specially selected salt to the continuous phase, i.e., the aqueous phase, of the slurry of the invention. A particular surprise was that the improvement aimed at in accordance with the invention was achieved speci=ically through the use of salts, since salts are generally regarded by those in the coatings art as being destabilizing. Yet more surprising was that the salts for use in accordance with the invention brought forth the improvement aimed at in accordance with the invention across a range of different clearcoat slurries.

6a The slurries of the invention may be of various compositions. For example, - the clearcoat sl~:rries }.n ow-n from _ the Germen patent applications DE 195 40 977 Al or DE 19832 2 06 'A1, prepared by means of grinding and dispersing processes and curable thermally or with actinic radiation, - the clearcoat slurries known from the German patent application DE 199 59 923 Al, prepared by means of primary dispersion processes and curable thermally or both thermally and with actinic radiation, - the clearcoat slurries known from the international patent applications WO 97/45476, WO 98/45356 or WO 00/17256 or from the American patent US 4,056,653 A, prepared by means of melt emulsification processes and curable thermally or both thermally and with actinic radiation, or - the clearcoat slurries known from the German patent applications DE
198 41 842 A1, DE 196 17 086 A1 or DE 199 08 018 A1 or from the European patent application EP 0 899 282 Al, prepared by means of secondary dispersion processes and curable thermally or both thermally and with actinic radiation are a suitable basis for the slurries of the invention.

Of these, the clearcoat slurries known from the German patent applications DE
198 41 842 Al or DE 199 08 018 Al, prepared by means of secondary dispersion processes and curable thermally or both thermally and with actinic radiation, which are free or substantially free from external emulsifiers and organic solvents, are of advantage and are therefore used with preference in accordance with the invention. These clearcoat slurries display particular advantages and are therefore used with particular preference in accordance with the invention.

Very particular preference is given to the clearcoat slurries prepared by the secondary dispersion process and comprising the specific methacrylate copolymers described below as binders in the dimensionally stable particles.

The slurry of the invention comprises as a constituent essential to the invention at least one, especially ,one, water-soluble salt, preferably in an amount of from 0.1 to 50 mmol per 1 000 g of water present in the slurry of the invention. It is preferred.to use from 0.2 to 40, with 'particular preference from 0.3 to 30, with very particular pre-ference from 0.4 to 20, in particular from 0.5 to 10, and especially from 0.5 to 8 mmol/1 000 g of water.

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The salt can be decomposed without residue or substantially without residue. This means that in the course of its decomposition it does not form any residues or forms residues only in an amount that does not induce deleterious technical effects in the clearcoats of the invention.

The salt may-be decomposable by means of heat and/or actinic radiation. Preferably, it is thermally decomposable. It is preferably decomposable under the condi ti ons of the curing of the clearcoat films of the invention produced from the slurries of the invention.
It is of advantage in accordance with the invention if the salt is decomposable at temperatures above 100 C., The decomposition of the salt is preferably.at an end at 250 C, more preferably 200 C, with particular preference 190 C, and in particular 180 C.

The decomposition of the salt may be accompanied by formation of any of a. very wide variety of organic, inorganic and organometallia decomposition products.
The decomposition products, accordingly, may- comprise volatile elements, neutral organic or, inorganic 5-hydrogen compounds, organic and inorganic bases, organic and inorganic acids oroxides.

Examples of volatile elements are phosphorus, sulfur, riitrogen and oxygen,'especially nitrogen.

10 f Examples of neutral organic and inorganic hydrogen compounds are water and hydrocarbons,, especially water.

Examples of organic_and inorganic bases are ammonia, methylamine, dimethylamine and trimethylamine, especially ammonia.

Examples of organic and inorganic acids are formic acid, acetic acid, 'propionic acid,.oxalic acid, citric acid, tartaric acid, hydrochloric acid, hydrogen bromide, phosphoric acid, phosphorous acid, amidosulfonic acid, sulfuric acid, sulfurous acid, thiosulfuric acid, HSCN and hydrogen sulfide, especially acetic acid.

Examples of oxides are carbon dioxide, sulfur dioxide, sulfur trioxide and phosphorus oxide, especially'carbon dioxide.

I i - 11. - . .
It is preferred to select a salt whose decomposition products are of little or no toxicity and/or of little or no corrosiveness. Preference is -given to selecti.ng a salt which forms, as its decomposition products, water, nitrogen, carbon dioxide, ammonia and organic acids.

With particular preference, the salt is selected from the group of ammonium salts, with very particular preference from the -group consisting of salts. of ammonia and of organic amines with organic 'and inorganic acids.

The ammonium salt is selected in= particular from the group consisting of ammonium carbonate, ammonium thiocyanate, ammonium sulfamate, ammonium sulfite monohydrate, ammonium formate, ammonium acetate, ammonium hydrogen oxalate monohydrate, diammonium oxalate monohydrate, ammonium citrate, and ammonium tartrate.- Of these, in turn, ammonium carbonate and ammonium acetate are very particularly advantageous and are therefore used with very-p.articular preference in accordance with the invention.

The slurry of the invention comprises dimensionally stable= particles. In the context of the present invention, "dimensionally stable"means that, under the customary known c*onditions of storage and application of clearcoat slurries, the particles undergo little if any agglomeration, and/or breakdown into smaller ,.. .

n particles, but instead substantially retain their original form even under the influence of shear forces.
The particles may be highly viscous and/or solid.
Preferably, the dimensivnally. =stable particles are solid.

For the. slurry of the invention it is advantageous if the average size of the particles is from 1 to 20 m and with particular preference from. 3 to 15 m. By average particle size is meant the 50% median value as determined by the laser diffraction method., i.e., ,50%
of the particles have a diameter 5 the median value and 50% of the particles have a diameter ? the median value. Preferably, at least 99% of the particles have a size < 30 u.zn.

Slurries having average particle sizes of this kind and a solvent content of < 1% exhibit better application properties and, at the applied filr- thicknesses of > 30 m as presently practiced in the automobile industry for the fiixishing of automobiles, exhibit much less of a tendency toward popping marks and mudcracking than conventional cleareoat slurries.

The upper limit on particle size is reached when the size of the particles means that they are no longer able to flow out fully on baking, and thus film leveling is adversely affected. In cases where requirements regarding the appearance are not very ~ 13.-stringent, however, the limit may als-o be higher. 30 gm is considered a sensible upper 3.imi-t, since above this particle size the spray nozzles and the rinsing ducts.
of the highly sensitive application apparatus are likely to become blocked.

The slurry of the invention is, preferably, substantially or entirely free from organic solvents..
In the context of the present invention this means that it has a residual volatile solvent content of preferably < 3.% by weight, particularly preferably < 2%
by weight, and with very particular preference c 1% by weight.

Preferably, the slurry of the invention is substantially or entirely free, in the. abovementioned context, from external emulsifiers (regarding "emulsifiers" cf. Johan Bieleman, "Lackadditive"
[additives for coatings], pages 160 to 100, "interface-active compounds"). Excluded from this proviso are the alkoxylated C16-C3.8 fatty alcohols which are preferablv added to the slurries of' the invention in the course of their preparatioxi by the secondary dispersion technique, by way of the organic solution of the constituents or by way of the aqueous phase.

The. preferred particle size as described above may also be obtained without the aid of additional external emulsifiers if. the slurry of the invention contains 1 , , ~

from 0.05 to 1, preferably from 0.05 to 0.9, more preferably from 0.05 to 0.8, with particular preference from 0.05 to 0.7, and in particular from 0.05 to 0.6 meq of potentially ionic groups per g of solids.

The amount of neutralizing agents is preferably chosen such that the degree of _ neutralization is 100%, preferably 'below 80%, with particular preference below 60%, and in particular below 50%.

The chemical nature of the binder is generally not . = . C
restricting in this respect, provided it contains ion-forming groups which can be converted into salt groups by neutralization and which, as a result, are able to take over the function of ionic stabilization of the particles in water.

Suitable anion-forming groups include acid groups such as carboxylic acid, sulf.onic acid or phosphonic acid groups, especially carboxylic acid groups. Accordingly, bases, such. as alkali metal hydroxides, ammonia or amines, are used as neutralizing agents. Alkali metal = t, hydroxides can be used only to a limited extent, since the alkali metal ions are not volatile on baking and, owing to their incompatibility with organic substances, may cause=the film to become cloudy and may lead to loss of gloss. Therefore, ammonia or amines are preferred. in the case of amines, tertiary amines are preferred. By way of example, mention may be made of N,N-dimethylethanolamine or aminomethylpropanolamine (AMP).

Suitable cation-fbrming groups include primary,.
secondary and tertiary amines. Accordingly, neutralizing agents used are, in particular, low mol'ecular mass organic acids such as formic acid,' acetic acid, dirciethylolpropionic acid or lactic acid..
For the preferred use of the slurry of the invention in automobile finishing as an unpigmented clearcoat material, preference is given to polymers or oligomers containing acid groups as ion-forming groups, since these so-called anionic binders generally exhibit better. resistance to yellowing than 'the classof the cationic binders.

However, cationic binders containing groups which. can be converted.into cations, such as amino groups, are likewise suitable for use in principle, provided the field of use tolerates their typical secondary properties such as-their tendency toward yellowing.

'Examples of suitable binders are random, alternating and/or block, lin.ear and/or branched and/or comb, addition (co)polymers of ethylenically unsaturated monomers, or polyaddition- resins and/or poly-condensation resins. For further details of * these terms, refer to Rompp Lexikon Lacke urid Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, page 457, "polyaddition" and "polyaddition resins (poly-adducts)", and also pages 463 and 464, "poly-! ii ~

condensates", "polycondensation" and "polycondensation resins", and also pages 73 and 74, "biriders".

Exarnples of suitable addition (co)polymers are (meth)acrylate (co)polymers or partially saponified polyviiayl esters, especially (meth)acrylate copolymers.
Examples of suitable polyaddition resins and/or polycondensation resins are polyesters, alkyds, polyurethanes, polylactones, polycarbonates, poly-ethers, epoxy resins, epoxy resin-amine adducts, polyureas, polyamides, polyimides, polyester-polyurethanes, polyether-polyurethanes or polyester-polyether-polyurethanes.

These oligomers and polymers are known to the skilled worker, and many suitable compounds are available ori the market.

in accordance with the invention the (meth)acrylate copolymers, the polyesters, the alkyd resins, the polyurethanes and/or the acrylated polyurethanes are of acdvantage and are 'therefore-used with preference.

Highly suitable (meth)acrylate copolymers and processes for preparing-them are described, for example, in the German patent application DE 199 08 018 Al, page 9, line 44, to page 10,-~ Iine 53, in the European patent application EP 0 767 185 Al, in the German patents .DE 22 14 650 B1 and DE 27 49 576 B1, and in the ,, , . .

17 American patents US 4,091,048 A, US 3,781,379,A, US 5,480,493 A, US 5,475,073 A, and US 5,534,598 A, or in the sta'ndard 'work by Houben-Weyl, Methoden der organischen Chemie, 4th edition, volume .14/1, pages 24 to 255, 1961. Suitable, reactors for the copolymerization include the customary and known stirred tanks, stirred tank cascades, tube reactors, loop reactors or Taylor reactors, as are described, for example, in the patent applications DE 1 071 241- B1, EP 0 498 583 Al or DE 198 28 742 Al or in the article by K. Kataoka in Chemical Engineering Science, volume 50, No. 9, 1995, pages 1409 to 1416.

Highly suitable polyesters and alkyd resins, and their preparation, are described, for= example, in the standard work Ullmans Encyklopadie der technischen Chemie, 3rd edition, volume 14, Urban & Schwarzenberg, Munich', Berlin, 1963, pages 80 to 89 and pages 99 to 10.5, and'also in the following books: "R6sines Alkydes-Pol.yesters" by J."Bourry, Dunod, Paris, 1952, "Alkyd Resins" by C.R. Martens, Reinhold Publishing Corporation, New York, 1961, and, "Alkyd Resin Technology" by' T.C. Patton, Interscience Publishers, 1962.

Highly suitable polyurethanes and/or acrylated polyurethanes and their preparation are described, for example, in , the - =patents EP 0 708 788 A1-, DE 44 01 544 Al or DE 195 34 361 Al.

Very particular advantages result for the slurries of the invention if their dimensionally stable particles comprise as binder(s) at least one methacrylate copolymer which contains in copolymerized= form, based on a given methacrylate copolyrner, at least 90% by weight,' preferably at least 95% by weight, and in particular at least 99% by weight of methacrylate comonomers, including znethacrylate comonorners containing potentially ionic groups.

Preferably, the (meth)acrylate comonomers containing potentially ionic groups comprise acrylic' acid, beta-carboxyethyl acrylate and/or methacrylic acid, especially methacrylic acid. The (meth)acrylate comonomers containing potentially ionic groups *are preferably copolymerized into the methacrylate copolymers in an amount such that the above-described amount of potentially ionic groups in the particles can be set without problems. They are copolymerized into .20 the methacrylate copolymers preferably in an amount of (..
from 0.1 to 3%, more preferably from 0.2 to 2. 6%, wi th particular preference from 0.3 to 2.6%, with very particular preference from 0.4 to 2.4%, and in particular from 0.5 to 2.2% by weight, based in each case on a given methacrylate copolymer.

The methacrylate copolymers preferably have a glass transition temperature, Tg, of not more than 50 C; at the same tirne the glass transition temperature Tg ." ' =

'should not go below preferably 0 C, more preferably 10-OC, and in particular 20 C.

The glass transition temperature, Tg, of the methacrylate copolymers is preferably set by way of at -least one methacrylate comonomer which is free from reactive functional groups and from potentially ionic groups. More preferably, the glass transition temperature, Tg, is set by way of at least two, in .10 particular two, methacrylate comonomers which are free from reactive functional groups and from potentially ionic groups. Preferably, the glass transition temperatures, Tg, of the respective homopolyrrners of the methacrylate comonomers that are free from reactive functi-onal groups and from potentially ionic groups differ from one another by not more than 40 C.

Examples of suitable methacrylate comonomers free from reactive functional groups and from potentially ionic groups are methyl,=.ethyl, n-propyl, n-butyl, i-butyl, tert-butyl, n-pentyl, isoamyl, cyclopentyl, n-hexyl and cyclohexyl methacrylate. Of these, i-butyl methacrylate (glass transition temperature, Tg, of the homopolymer:
53 C) and n-butyl methacrylate (glass transition temperature, Tg, of the homopolymer: 20 C) are of advantage and are therefore used with particular preference.

The amount of the copolymerized methacrylate comonomers, free from reactive f.unctional groups and from potentially ionic groups, that is copolymerized into the'. methacrylate copolymers 'to be used with preference may vary widely. It is essential that the amount is chosen such that the resulting methacrylate copolymers have the glass transition temperature, Tg, described above.. The amount is preferably at least 50%, more preferably at least 55%, with particular preference at least 60%, with very particular preference at least 65%, and in particular at least 70%
= t by weight, based in each case on a given methacrylate copolymer.

The weight ratio of the methacrylate comonomers used with particular preference, n-butyl methacrylate and i-butyl methacrylate, may vary widely. The n:i weight ratio is preferably from 10:1 to 1:6, more preferably from 8:1 to 1:4, wi=th particular preference from 6:1 to 1:2, with very particular preference from 5:1 to 1:1.5, and in particular from 4:1 to 1:1. ~.
Where the slurries of the invention are physically curable slurries, the methacrylate copolymers contain reactive functional groups, if at all, only in a number which is insubstantial as far as crosslinking is concerned.

Where.the slurries of the invention are thermally self-crosslinking, the methacrylate copolymers contain the r . .

complementary reactive functional groups for thermal .crosslinking, described below,. and/or reactive functional groups which are able to crosslink "with themselves", i.e., with groups of their own kind.

Where the slurries of the invention are curable with actinic radiation, the.' methacrylate copolymers may contain reactive.functional groups having at least one bond which can be activated with actinic radiation.

10. These reactive functi~ onal groups are mandatorily ~. .
present in the methacrylate copolymers of the slurries of the invention that are curable with actinic radiation if the slurries conta.in no other radiation-curable constituents.

Tnlhere the slurries of the invention are. dual-cure .slurries,.the methacrylate copolymers contain reactive functional groups for thermal crosslinking and/or reactive functional groups containing at least one bond ~ 20 which ' can be activated with actinic radiation. The reactive functional groups containing at least' one bond which can be activated with actinic radiation are mandatorily present in the methacrylate copolyrners of the dual-cure slurries of the invention if the dual-cure slurries contain no other radiation-curable constituents.

Examples of suitable complementary reactive functional groups for use in accordance with the invention- are ~ =

placed together in the following overview. in the overview, the variable R stands 'for an acyclic or' cyclic aliphatic radical, an aromatic radical and/or an aromatic-aliphatic (araliphatic) radical; the variables R' and R" stand for identical cir =different alipl-~atic radicals or are linked with one another to form an aliphatic or heteroaliphatic ring.

~
, . . ~, ~: - =

Overview: Examples of complernentary reactive fuactional.
groups Binder and crosslinking agent or Crosslinking agent and binder -SH -C(O)-OH
-NH2 .

-OH -NCO
-O-(CO)-NH-(CO)-NH2 -NH-C(O)-OR
-O-(CO)-NH2 -CH2-OH
>NH -CH2-O-R

-Ni-i-CH2-O-R

-N(-CH2-O-R)2 -NH-C(O)-CH(-C(Q)OR)2 -NH-C(O)-Ci-I(-C(O)OR)(-C(O)-R) -NH-C(O)-NR"R'"

> Si.(OR)2 =C
O

. ~
-C(O)-OH 0 -CH-&z -C( O )-N(CH2-CHz-U H )z The selection of the respective complementary. reactive functional groups is guided on the one hand by the consideration that they should not enter into -any unwanted reactions during the preparation of the binders and during the preparation, storage, .application, and melting of the slurries of, the invention, and in particular shoulcl not form any polyelectrolyte complexes or undergo premature cross-linking, and/or must not disrupt or inhibit curing with actinic radiation, and secondly by the temperature range within which crosslinking is to take place.

. . c "' - 25 -For the slurries -of the invention it is preferred 'to employ crosslinking temperatures of from 60 to 180 C.
Use is therefore made preferably of binders containing thio, hydroxyl, N-methylolamirio, N-alkoxyraethylamino, imino, carbamate, and/or allophanate groups, preferably hydroxyl groups, on the one hand and, preferably, crosslinking agents containing anhydride, epoxy, blocked and unblocked, especially blocked, isocyanate, urethane, methylol; methylol ether, siloxane, carbonate, amino, hydroxyl and/or beta-groups, preferably blocked hydroxyalkylamide = . .

isocyanate, carbarnate and/or N-alkoxymethylamino groups, on the other.

In the case of self-crosslinking slurries of the invention, the binders (A), contain, in particular, methylol, rnethylol ether and/or N-alkoxymethylamino groups.

Complementary reactive functional groups which are especially suitable for use in the thermally externally crosslinking slurries of the invention and the dual-cure slurries of the invention are hydroxyl groups on the one hand and blocked isocyanate groups on the other. The functionality of the binders in respect of the reactive functional groups described above may vary very widely and is guided, in particular by the desired cross,linking density and/or by the functionality of the crosslinking agents that are employed in each case. In the case of hydroxyl-containing binders, for example, the OH number is preferably from 20 to 300, more preferably from '40 to 250, with particular preference from 60 to 200, with very particular preference from 80 to 190, and in particular from 90 to 180 mg KOH/g.

The above-described complementary reactive functional groups may. be incorporated into the binders in accordance with the customary and known methods of polymer chemistry. This can be done, for example, through the incorporation of. methacrylate comonomers which carry the corresponding reactive functional groups, and/or with the aid of polymer-analogous reactions.

Examples of suitable methacrylate comonomers containing~
reactive functional groups are methacrylate comonomers which carry at least one hydroxyl, amino, alkoxymethyl-amino, carbamate, allophanate or imino group 'per molecule, such as - hydroxyal-kyl esters of methacrylic acid, which are derived from an alkylene glycol which i.s esterified with the acid, or which are obtainable by reaction of the snethacrylic acid with an alkylene oxide such as ethylene oxide or propylene oxide, especially hydroxyalkyl esters of = CA 02443615 2003-10-08 methacrylic acid in which the hydroxyalkyl gr.rmp.
contains up to 20 carbon atoms, such as 2-hydroxy-ethyl, 2-hydroxypropyl, 3-hydroxypropyl, 3-hydroxybutyl.or 4-hydroxybutyl methacrylate; or hydroxycycloalkyl esters such as 1,4-bis(hydroxy-methyl)cyclohexane, octahydro-4,7-methano-lH-indenedimethanol. or methylpropanediol monometh-acrylate; or reaction products of cyclic esters, such as epsilon-caprolactone, and these hydroxy-alkyl methacrylates;

- reaction products of methacrylic acid of the glycidyl ester of an alpha-branched monocarboxylic acid having from 5 to 18 carbon atoms per molecule, particularly a Versatic acid, or instead of the 'reaction product an- equivalent amount of inethacrylic acid, which is then reacted, during or after the polymerization reaction, with the glycidyl ester of an alpha-branched monocarboxylic acid having from 5 to 18 carbon atoms per molecule, particularly a xTersatic(D acid;
- aminoethyl- methacrylate or N-methylaminoethyl methacrylate, which may also be used to introduce potentially ionic groups;

- N,N-di(methoxymethyl)arninoethyl methacrylate or N,N-di(butoxymethyl)aminopropyl methacrylate;

- metliacrylamides such as methacrylamide, N-methyl-, N-methylol-, N,N-dimethylol-, N-methoxymethyl-, N, N-di (methoxymethyl ) -, N-ethoxymethyl- ' and/or N,N-di(ethoxyethyl)-methacrylamide;

.5 - methacryloyloxyethyl, -propyl or -butyl carbamate or allophanate; further examples of suitable methacrylate comonomers containing carbamate groups are described , in 'the pa=tents US 3,479,328 A, US 3,674,838 A, US 4,126,747 A, US
4,279,833 A or US 4,340,497 A.=

In minor amounts, the reactive functional groups for thermal crosslinking may be introduced by way of other olefinically unsaturated monomers, such as the corresponding acrylates, allylamine, allyl alcohol or polyols, such as trimethylolpropane monoallyl or diallyl ether or,pentaerythritol monoallyl, diallyl or triallyl.ether.

The binders of the dual-cure slurries of the invention or those of the slurries of the invention which are curable purely with actinic radiation may contain on aver.age per molecule.at least one, preferably at least two, group(s) containing at least one bond which can be activated with actinic radiation.

In the context of the present invention, a bond which can be activated with actinic radiation means a bond = CA 02443615 2003-10-08 = - 29 which, on exposure to actinic radiation, becomes.
reactive and, together with other activated bonds of its kind, enters into polymerization- reactions and/or crosslinking reactions which proceed in accordance with free-radical and/or- ionic mechanisms. 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 used with ~ very particular preference in accordance with the invention. For the sake of brevity, they are referred to below as "double bonds".

Accordingly, the group that is preferred, in accordance with the invention contains one double bond or two, three or four double bonds. Tnlhere more than one double bond is used, the double bonds may be conjugated. In accordance- with the invention, however, it is of ( 20 advantage if the double bonds are present in isolation, in particular each terminally, within -the group in question. it is of particular a-dvantage in accordance with the invention to use two double bonds, especially one double bond. 25 The dual-cure binder contains on average at least one of the above-described groups which. can be activated with actinic . radiation_ This means that the functionality of the binder in this respect is integral, i. e. , for example, is two, three, four, five or more, or is nonintegral, i.e., for example, is from 2.1 to 10.5 or more. The decision as to which functionality is chosen is guided by the requirements which are imposed on the respective dual-cure slurries.
Where on average per molecule more than one group which can be activated with actinic radiation is used, the groups are structurally different from one another or of the same structure.
. . . ~
Where they are structurally different from one another, this means in the context of the present invention that two, three, four or more, but especially two, groups which can be activated with actinic radiation are used which derive from two, three, four or more, but 'especially 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; dicyclo-pentadienyl ether, norbornenyl ether, isoprenyl ether, isopropenyl ether, allyl ether or butenyl ether groups;

dicyclopentadienyl ester, norbornenyl ester, isoprenyl ester, isopropenyl ester, allyl ester or butenyl ester groups, but especially acrylate groups.

The groups are' attached to the respective parent st.ructures of the binders preferably by way of urethane, urea, allophanate, ester, ether- and/or amide groups, but in particular by way of ester groups. This is normally done by means of customary and known continuous= polymer-analogous reactions such as, for instance, the -reaction of pendant glycidyl groups with olefinically unsaturated comonomers containing an acid group, of pendant hydroxyl groups with the halides of these comonomers,.' of hydroxyl groups with= isocyanates containing double bonds, such as vinyl isocyanate, methacryloyl isocyanate and/or 1-(1-isbcyanato-1-methylethyl)-3-(l-methylethenyl)benzene (TMI(D from CYTEC), or of pendant isocyanate groups with the hydroxyl-containing comonomers described above.

In the particles it is, however, also possible to employ mixtures of binders- that are curable by means of heat alone and of. binders =that are curable by means' of actinicxadiation alone.

Processes for preparing the methacrylate copolymers to be used with preference are described in the patent applications, patents and literature references disclosed above. With 'particular preference, the methacrylate copolymers are prepared under pressure.

The amount of the' binders described above in the' dimensionally stable particles of the slurry of the invention may vary widely. In the case of the thermally externally crosslinking=or of the thermally externally crosslinking and actinic-radiation-curable slurries of the invention said amount is preferably from 5 to 80%, more preferably from 6 to 75%, with particular preference from 7 to 70%, with very particular preference from .8 to 65~ and in particular from 9 to 60% by weight, based in each case on the solids of the slurries of the invention. in the case of the slurries of the invention that are curable physically and those that are curable with actinic radiation, but especially those that are curable physically, the amount may be up to 100% by weight.

The dimensionally stable particles of the slurries of the invention that are curable thermally, or thermally and with actinic radiation, may comprise crosslinking agents which contain complementary reactive functional groups for thernal crosslinking and/or reactive functional groups containing at least one bond which can be activated with actinic'radiation.

Suitable crosslinking agents are all crosslinking agents that are customary in the field of light-stable clearcoats. Examples of suitable crosslinking agents are - amino resins, as described for example in Rompp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, 1998, page 29, "amino resins", in the textbook "Lackadditive" [Additives for coatings) by Johan Bieleman, Wiley-VCH, Weinheim, New York, 1998, pages 242 ff., in the book "Paints, Coatings and Solvents", second, completely revised edition, edited by D.-Stoye and W. Freitag, Wiley-VCH, Weinheim, New York, 1998, pages 80 ff., in the patents US 4 710 542 Al or EP 0 245 700 A1,'and in.
the article by, B. Singh and coworkers, "Carbamylmethylated Melamines, Novel Crosslinkers for the Coatings iridustry", in Advanced Organic Coatings Science and. Technology Series, 1991, volume 13, pages 193 to 207; .

- carboxyl-containing compounds or resins, as described for example in the patent DE 196 52 813 Al or 198 41 408 Al, especially 1,1.2-dodecanedioic acid, - resins or compounds containing epoxide groups, as ( 20 described for exainple in the patents EP 0 299 420 Al, DE 22 14 650 31, DE -27 49 576 31, US 4,091,048 A or US 3,781,379 A;

- tris(alkoxycarbonylamino)triazines, as described in the patents US 4 939 213 A, US 5 084 541 A, US 5 288 865 A or in the patent application EP 0 604 922 A;

- blocked polyisocyanates, as described for example in the patents US 4,444,954 Al, DE 196 17 086 Al, DE 196 31 269 Al, EP 0 004 571 Al or -EP 0 582 051 Al; or - beta-hydroxyalkylamides such as N5 N,N',N'.-tetrakis(2-hydroxyethyl)adipamide or N,N,N',N'-tetrakis(2-hydroxypropyl)adipamide.

The crosslinking agents described above may be used individually or as a mixture of at least two crosslinking agents. In accordance with the invention, the blocked polyisocyanates and/or tris(alkoxy-carbonylamino)triazines, especially the blocked poly-isocyanates, afford particular advantages and are therefore used with particular preference.

The amount of crosslinking agent(s) in the dimensionally stable particles may likewise vary widely and is guided primarily by the functionality and amount of the binders on the one hand and by the functionality of the crosslinking agents, on the 'other. The amount is ~
preferably from 10 to 95%, more 'preferably from 12 to 94%, with particular preference from 14 to 93%, with very particular preference from 16 to 92%, and in particular from 18 to 90% by weight, based in each case on the solids of the slurry of the invention.

In addition to the essential. constituents described above, the dimensionally stable particles- of the slurry cf the invention.may comprise additives such 'as are.

commonly used in clearcoat=materials. it is essential that these additives do not substantially lower the glass transition temperature, Tg, of the binders.

Examples of suitable additives are polymers (other than the above-described methacrylate copolymers), crosslinking catalysts, defoamers, adhesion promoters, additives for. -improving substrate wetting, additives for improving surface 'smoothness, flatting agents, light stabilizers, corrosion inhibitors, biocides, flame retardants, and polymerization inhibitors, especially photoinhibitors, as described in the book "Lackadditive".by Johan Bieleman, Wiley-VCH, Weinheim, New York, 1998.

Moreover, the dimensionally stable particles may also comprise constituents curable with actinic radiation, different -than the binders and =crosslinking agents described above, as additives if the slurry of the invention is to be curable thermally and with actinic radiation or with actinic radiation alone.- Examples of such constituents include - the binders envisaged for use in W-curable clearcoat materials and powder clearcoat materials and described in the European patent applicatioris EP 0 928 800 Al, EP 0 636 669 Al, EP 0 410 242 A1;
EP 0 783 534 Al, EP 0 650 978 Al, EP 0 650 979 Al, EP 0 650 985 Al, EP 0 540 884 Al, EP 0 568 967 Al, = - 36 -EP 0 054 505 Al or EP 0=002 866 Al, the German patent applications DE 197 09 467 Al, DE 42 03 278 Al, DE 33 16'593 Al, DE 38 36 370 Al, -DE 24 36 18-6 Al or DE 20 03 579 B1, the international patent applicatzons WO 97/46549 or WO 99/14254 or the American patents US 5,824,373 A; US 4,675,234 A, US 4,634,602 A, US 4,424,252 A, US 4,208,313 A, US 4,163,810 A, US 4,129,488 A, US
4,064,161 A or US 3,974,303 A;

- reactive diluents curable with actinic radiation, such=as those described in.Rornpp Lexikon Lacke und Druckfarben, Georg 'Thieme 'Verlag, Stuttgart, New York, 1998, on page 491 under the headword "reactive diluents"; or - photoinitiators as described in Rompp Chemie Lexikon, 9th, expanded and revised edition, Georg Thieme Verlag, Stuttgart, vol. 4, 1991, or in Rompp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, 1998, pages 444 to 446.

The slurry of the invention may likewise comprise additives.in the aqueous phase.

Preferably, the additives in question are nonionic and/or ionic thickeners. This effectively counters the tendency of the comparatively large solid particles toward sedimentation.

Examples of nonionic= thickeners are hydroxyethyl-cellulose and polyvinyl alcohols. So-called nonionic associative thickeners are likewise available on the market in a diverse selection. They generally comprise water-dilutable ' polyurethanes' which are reaction products of water-soluble polyetherdiols, aliphatic diisocyanates, 'and monofunctional hydroxyl compounds with an organophilic radical.

Likewise available commercially are ionic thickeners.
These normally contain anionic groups and are based in particular on special polyacrylate resins with acid groups, some or all of which may have been neutralized.

Examples.of suitable thickeners for use in accordance with the invention are known from the text book "Lackadditive" by Johan Bieleman, Wiley-VCH, Weinheim, New York, 1998, pages 31 to 65, or from the German patent application DE 199 08 018 Al, page 13, line 18 to page'14, line 48.

For the slurry of the invention it may be advantageous if both of the above-described types of 'thickener are present therein. in by far the majority of cases, however, one thickener is sufficient, particularly a nonionic thickener, to, provide the desired pseudo-plasticity.

= I

The amount of thickeners to be added, and, where two different thickeners are employed, the ratio-of ionic to nonionic thickener, are guided by the desired viscosity of the slurry of the invention, which in turn is determined by the required sedimentation -stability and the specific requirements of spray application. The skilled worker 'is therefore able to determine the amount of the thickeners and, where appropriate, the ratio of the thickener types to one another on the basis of simple considerations, possibly with the aid . . . {.
of preliminary tests.

The viscosity is preferably set to within a range from 50 to 1 500 mPas at a shear rate of 1 000 s'1 and from 150 to 8 000 mPas at a shear rate of 10 s-1, and also from 180 to 12 000 mPas at a shear rate of 1 s-1.

This viscosity behavior, known as. "pseudoplasticity", describes a state which does justice both to the requirements of spray application, on the one hand, and to the requirements in terms of storage and sedimentation stability, on the other: in the state of motion, such as when pumping the slurry of the invention in circulation in the ring circuit of the coating plant and when spraying, for example, the slurry of the invention adopts a state of low.viscosity which ensures easy processability. in the absence of shear stress, on the other hand, the viscosity rises and thus e-nsures. that the coating material already 39. -present on the substrate to be coated has a reduced tendency to form runs on vertical surfaces. In the same way, a result of the higher viscosity in the stationary state, such as during storage, for instance, is that sedimentation of the solid particles is very largely prevented or that any slight degree of settling of the slurry of the invention during the storage period can be removed again by agitation.

The aqu.eous phase of the slurry of the invention may further comprise leveling assistants which can be incorporatedin the film by crosslinking. Examples of suitable constituents of*. this' kind are thermally curable reactive diluents such as positionally isomeric diethyloctanediols or hydroxyl-containing hyperbranched compounds or dendrimers such as are described in the German patent applications DE 198 05 421 Al, DE 198 09 643 Al or DE 198 40 405 Al.

Furthermore, the aqueous phase of the slurry of the invention may also comprise alkoxylated, especially ethoxylated, 'C16-C18 fatty alcohols containing more than 20 oxalkanediyl groups'in the molecule, such as are sold, for example, by BASF Aktiengesellschaft under the brand name Lutensol AT 50.

The slurry of the invention is preferably prepared by the secondary dispersion processes from the German patent application DE 199 08 018 Al or from the German patent DE 198 41 842 C2.

For this process, The ionically stabilizable binders and the crosslinking agents and also, where appropriate, the additives are mixed in organic solution and emulsified together in water with the aid of neutralizing agents. The dispersion is then diluted with water, while stirring. To start with a water-in-oil emulsion is formed, which on further dilution is transformed into an oil-in-water emulsion. This point is generally reached at solids contents of < 50% by weight, based on the emulsion, and is evident externally from a relatively sharp fall in viscosity in the course of the dilution.

The oil-in-water emulsion may also be prepared directly by the melt emulsification of the binders and of the crosslinking agents and also, where appropriate, of the additives ir. water.

The resulting emulsion, which still contains solvents, is subseauently freed from its solvents by azeotropic distillation.

In accordance with the invention it is of advantage if the solvents to be removed are distilled off at a distillation temperature below 70 C, preferably below 50 C, and in particular below 40 C. If desired, the-distillation pressure is chosen so that this temperature range is observed in the case of relatively higher-boiling=solvents.

.5 At its most simple, the azeotropic distillation may be effected by stirring the emulsion at room temperature in an open vessel for several days. Preferably, the solvent-containing emulsion is freed from its solvents by vacuum distillation.
~

In order to avoid high viscosities, the amount of water and solvents removed by evaporation or distillation is replaced by water. The water may .be added before, during, or after the evaporation -or distillation, by addition in portions.

Following the loss of solvents, the glass transition temperature, Tg, of the dispersed particles rises and a dispersion, i.e. the slurry of the invention, forms instead of the previous solvent-containing emulsion.

The salts' for use in accordance. with the invention may be introduced into the slurries of the invention, or the'ir precursors, in a variety of ways. For example, the salts may be added to customary and known clearcoat slurries to give the slurries of the invention. They may also be added to the organic solution of constituents of the 'powder slurry of the invention.

Pre.ferably, they are dissolved in the water or the aqueous phase prior to the emulsification of the organic solution.

If desired, the - particles of the slurry of the invention are mechanically comminuted in the wet state, a procedure also referred to as wet grinding.. In the course of this' treatment it is preferred to employ conditions such that the temperature of the material being ground does not exceed 70 C, more preferably 60 C, and in particular 50 C. The specific energy input during the grinding process is preferably from 10 to 1 000,. more preferably from 15 to 750, and in particular from 20 to 500 Wh/g.

For wet grinding it is possible to 'e.mploy a very wide variety of equipment which produces high or low shear fields.

Examples of suitable equipment producing low shear fields are customary and known stirred tanks, slot homogenizers, microfluidizers, and dissolvers.

Examples of suitable equipment producing high shear fields are customary and known stirred mills and inline dissolvers.

Particular preference is given to employing the equipment which produces high shear fields. Of this equipment, the stirred mills are particularly advantageous in accordance with the invention and are therefore used with very particular preference, During wet. grinding, generally, the slurry of the invention is supplied to the above-described equipment, and circulated. therein, by mearns of appropriate devices, such as pumps, until the desired particle size has been reached.
..

The slurry of the invention advantageously has a solids content of from 10 to 60* by weight, in particular from to 50% by weight.

15 The slurry of the invention is preferably filtered prior to' its use. This is done using the customary and known filtration equipment and filters, such as are also suitable 'for filtering the known clearcoat slurries. The mesh size of the filters may vary widely 20 and is guided primarily by the size and size distribution of the particles- o-f the slurry of the invention. The skilled worker- is therefore easily able todetermine the appropriate filters on the basis of this physical parameter. Examples of suitable filters are bag filters. These= are available on the market under the brand names Pong@) -or Cuno .it is preferred to use bag filters having mesh siz-es of from 25 to 50 u.m, examples being Pong 25 to Pong 50.

I

To produce the clearcoats of. =the invention, the slurry of the invention is applied to the,substrate that is to be coated. No special measures need be taken here;
instead, the application may take place in accordance with the customa.ry arnd known processes, which is another particular advantage of the slurry of the invention.

Following its application, the slurry of the invention dries without problems and does not film at the processing temperature, generally at room temperature.
in other words, the slurry of the invention, applied.as a wet film, loses water when flashed off at room temperature or slightly elevated'temperatures, with the particles present therein changing their originaZ.foran.
As a result, the tendency toward mudcracking is extremely low.-In the subsequent baking step,- the now substantially water-free layer is caused to crosslink. In some cases {.
it may be of advantage to carry .out. the leveling process arid . the crosslinking reaction. with a chronological offset, by operating a staged heating program or a so-called heating ramp. The crosslinking temperature that is appropriate for the present examples is situated between 120 and 160 C. The corresponding baking time is between 20 arid 60 minutes.
In the case of the dual-cure slurry of the invention, -. 45 -thermal curing is supplemented by curing with actini.c' radiation, which may be carried out using the.customary and known radiation sources-and processes, such as are described, for example, in the German patent application DE 198, 18 735 Al, column 10, line 31 to column 11, line 22. These processes and equiprnent may also be used to cure the slurry of the invention that is cu'rable with actinic radiation.

tf. 10 The resultant clearcoat has outstanding performance properties. For instance, it adheres firmly to -all customary and known basecoats or to substrates such as metal, glass, wood, ceramic, stone., concrete or plastic. It is of high gloss, smooth, scratch-resistant, stable to weathering and chemicals, and even at high coat thicknesses is free from defects, such as stress cracks or popping marks. It no longer exhibits any blushing on exposure to moisture. Furthermore, it is free from microdefects and displays no disruptive optical effects, such as a starry sky that is similar to the metallic effect.

On the basis of this advantageous profile of properties, the slurry of the invention is outstandingly suitable for automotive OEM finishing, automotive refinish, the interior and exterior painting of buildings, the coating of doors, windows and furniture, and industrial coating, including coil coating, container coating, the coating of small parts, the impregnation and/or coating of electrical components, or the coating of white goods. It is used in particular to produce clearcoats as part of multicoat color and/or effect paint systems, which are produced from basecoat -materials and the slurry of the invention by the' customary and known wet-on-wet techniques.

For the wet-on-wet technique, the slurry of the invention may readily be combined with numerous basecoat materials, especially aqueous basecoat materials, without the occurrence of problems,- such as cracking, lack of wettability, or poor intercoat adhesion.

15' The slurry of the invention may surprisingly also be used as an adhesive for producing adhesive films and as a sealing compound for producing seals, especially in the technical fields referred to above.

wr.=,rer.tive and comparative eyamples Preparation examp].e l The preparation of a methacrylate copolymer (binder) for inventive use 39.75 parts by weight of methyl ethyl ketone were charged to a reaction vessel eqLiipped with stirrer, reflux condenser, oil heating, nitrogen inlet pipe and two feed vessels, and this initial charge was heated to 78 C.

Thereafter, an initiator solution of. 4 parts by weight of methyl ethyl ketone and 5 parts'by weight of TBPEH
was metered in at a uniform rate from the first feed vessel over the course of 6.75 li.

Fifteen minutes, after the beginning of the initiator l . .
feed, a monomer mixture of 27.5 parts by weight of n-butyl methacrylate, 9.15 parts by weight of i-butyl methacryl.ate, 12.75 parts by weight of hydroxyethyl methacrylate and 0.6 part by weight of methacrylic acid was metered in at a uniform rate from the second feed vessel over the course of 6 h. The monomer line was ,then flushed with 0.25 part by weight of methyl ethyl ketone and the feed vessel with 0.5 part by weight of methyl ethyl ketone. After the end, of the in.itiator feed, the feed vess.el. in question was likewise flushed with 0.5 part by weight .of-methyl ethy"il- ketone.

The reaction mixture was left to react at 78 C- for a further 3 h. The volatile fractions were then removed by vacuum distillation until the solids content was 70%

byy weight. The resin solution was then- discharged. It had a viscosity of from 7.0 to 10.0 dPas (resin solids, 60 percent in xylene, at 23 C). The acid number was from 9.0 to 11.0 and the hydroxyl number was 110 mg = =

- 4=8 -KOH/g-resin solids.

Preparation exa.mple 2 The preparation of a blocked polyisocyanate based on hexamethylene=diisocyanate 534 parts by weight of Desmodur N 3300 (comrnercial ,isocyanurate of hexamethylene diisocyanate from Bayer AG) and 200 parts by weight of methyl ethyl ketone were charged to a reaction vessel and this in,itial charge was heated to 40 C. 100 parts by weight of 2,5-dirnethylpyrazole were added to the solution, with cooling, and the subsidence of the exothermic reaction was awaited. Thereafter, with continued cooling, a further 100 parts by weight of 2,5-dimethylpyrazole were added. After the exothermic reaction had again subsided, a further 66 parts by weight of 2,5-dimethyl-pyrazole were added. Cooling was then switched off, as a result of which the reaction mixture slowly warmed up ~.
to 80= C. It was held at this tempe=rature until its isocyanate content had fallen to below 0.1%. The reaction mixture was then cooled and discharged.

The resulting solution of the blocked polyisocyanate had a solids content of 81% by weight (1 h at 130 C) and a viscosity of 3.4 dPas (70% in methyl ethyl ketone; cone and plate viscometer at 23 C).

- ' = r Example 1 The preparation of an invezztive slurry and an inventive clear coating 961.8 parts by weight of the methacrylate copolymer solution from preparation example I and 484.6 parts by weight of the solution of the blocked polyisocyanate from preparation example 2 were mixed with one another at room temperature in an open stirred vessel for ( . ..
minutes. The resulting mixture was admixed with 21.5 parts by weight of Tinuvin 400. and 10.7 parts by weight of TinuvinCR? 123 (=cornmercial light stabilizers from Ciba Specialty Chemicals, Ync.), after which the 15 mixture was stirred at room temperature for .30 minutes.
Then 1.15 parts by weight of dibutyltin dilaurate and 4.01 parts by weight of- dimethylethanolamine were added. The resulting mixture was stirred at room temperature for a further two hours.

t. 20 SubsEquently, 735.7 parts by weight of deionized water in which 0.485 part by weight of 'ammonium acetate (corresponding -to :6.3 mmol/1 000 g of water) had been dissolved were added in small portions to the mixture.

After an interval of 15 minutes, a further 780 parts by weight of deionized water were. added at a uniform rate over the course of 30 minutes..

The resulting aqueous emulsion was diluted with 739 =r . .

50 ' parts by weight of deionized water. After that the same amount of a mixture of volatile organic -solvents and water was removed from it under reduced pressure on a rotary -evaporator, until the solids content was 37% by weight (1 h at 130 C).

To set the desired pseudoplasticity,- 90 parts by weight of Acrysol@ RM-8W (commercial xnonionic associative thickener from Rohm & Haas) and 15 parts by weight - of Bykg 333 (commercial leveling agent from Byk Chemie) were stirred into the clearcoat slurry.

For application of the inventive slurry 1, a so-called integra.ted system with a black basecoat material was prepared.

For this purpose, steel panels coated cathodically with commercially customary electrocoat material were.first of all coated with a functional coat .(Ecoprime(&; BASF

Coatings AG) using a' gravity-feed cup gun. After 5 minutes flashing -off at room temperature, this film.
was overcoated in the same way with a black aqueous basecoat material (Ecostar ;.BASF Coatings AG) and then subjected to initial drying at $0 C for 5 minutes.

After the panels had cooled, the inventivie slurry 1 was applied in the same way. The panels were then flashed off initially for 5 minutes and subsequently-subjected to initial drying at 40 C for 15 minutes.

= CA 02443615 2003-10-08 i They were then baked at 145 C for 30 minutes.

The wet films applied were chosen so that, after baking, the dry' film thicknesses for the functional coat and the aqueous basecoat were each 15 gm. The inventive clearcoat 1 had. a film thickness of from 40., to 45 The inventive clearcoat 1 was hard, scratch-resistant, clear, bright, resistant to,' chemicals, weathering and (. . condensation, and. free from microdefects which bring forth an optical 'effect -(starry sky) similar to the metallic effect.

Comparative Exam,ple Cl The preparation of a rioninventive clearcoat slurry and production of a noninventive clearcoat ~ 20 Example 1 was repeated, except that no ammonium acetate was added.

The resulting noninventive clearcoat was hard, scratch-resistant, clear, bright, and resistant to chemicals, weathering and condensation. However, it was not free from microdefects. These microdefects brought forth an optical effect (starry sky) similar to the metallic effect.

Claims (21)

WHAT IS CLAIMED IS:

1. A pseudoplastic clearcoat slurry comprising an aqueous phase comprising water, particles that are dimensionally stable under storage and application conditions, and at least one water-soluble salt, wherein the salt can be decomposed without residue into decomposition products, and wherein the salt is present in an amount from 0.1 to 50 mmol per 1 000 g of water.

2. The pseudoplastic clearcoat slurry as claimed in claim 1, which contains from 0.5 to 8 mmol of the salt per 1 000 g of water.

3. The pseudoplastic clearcoat slurry as claimed in claim 1 or 2, wherein the salt is decomposable under the conditions of curing of the clearcoat slurry.

4. The pseudoplastic clearcoat slurry as claimed in any one of claims 1 to 3, wherein the salt is decomposable thermally and/or with actinic radiation.

5. The pseudoplastic clearcoat slurry as claimed in claim 4, wherein the salt is thermally decomposable.

6. The pseudoplastic clearcoat slurry as claimed in any one of claims 1 to 5, wherein the decomposition products of the salt comprise volatile elements, neutral organic or inorganic hydrogen compounds, organic and inorganic bases, organic and inorganic acids or oxides.

7. The pseudoplastic clearcoat slurry as claimed in any one of claims 1 to 6, wherein the salt can be decomposed with the formation of decomposition products that have no toxicity and/or no corrosiveness.

8. The pseudoplastic clearcoat slurry as claimed in any one of claims 1 to 7, wherein the decomposition products are at least one of water, nitrogen, carbon dioxide, ammonia and an organic acid.

9. The pseudoplastic clearcoat slurry as claimed in any one of claims 1 to 8, wherein the salt is an ammonium salt.

10. The pseudoplastic clearcoat slurry as claimed in claim 9, wherein the ammonium salt is selected from the group consisting of salts of ammonia with organic acids, salts of ammonia with inorganic acids, salts of organic amines with organic acids, salt of organic amines with inorganic acids, and combinations thereof.

11. The pseudoplastic clearcoat slurry as claimed in claim 10, wherein the ammonium salt is selected from the group consisting of ammonium carbonate, ammonium thiocyanate, ammonium sulfamate, ammonium sulfite monohydrate, ammonium formate, ammonium acetate, ammonium hydrogen oxalate monohydrate, diammonium oxalate monohydrate, ammonium citrate and combinations thereof.

12. The pseudoplastic clearcoat slurry as claimed in claim 11, wherein the ammonium salt is selected from the group consisting of ammonium carbonate, ammonium acetate and combinations thereof.

13. The pseudoplastic clearcoat slurry as claimed in any one of claims 1 to 12, wherein the particles have an average size of from 0.8 to 20 um and at least 99% of the particles have a maximum size of 30 µm.

14. The pseudoplastic clearcoat slurry as claimed in any one of claims 1 to 13, wherein the slurry is cured thermally and/or with actinic radiation.

15. The pseudoplastic clearcoat slurry as claimed in any one of claims 1 to 14, wherein the slurry has a residual volatile organic solvent content less than 3% by weight.

16. The pseudoplastic clearcoat slurry as claimed in any one of claims 1 to 15, prepared by a process comprising:

1) emulsifying the particles in an organic solvent solution in water to give an emulsion of the oil-in-water type, wherein the salt is added to the water prior to or after the emulsification, 2) removing the organic, and 3) replacing at least by water some of the volume of solvent removed by water.

17. The pseudoplastic clearcoat slurry as claimed in claim 16, wherein the salt is added to the water prior to the emulsification 1).

18. Use of the clearcoat slurry as claimed in any one of claims 1 to 17 for automotive OEM finishing, automotive refinish, interior and exterior painting of buildings, coating of doors, windows and furniture, and industrial coating.

19. The use as claimed in claim 18, for coil coating, container coating, coating of small parts, impregnation and/or coating of electrical components, and coating of white goods.

20. The use as claimed in claim 18 or 19, wherein the clearcoat slurry is used to produce clearcoats as a part of multicoat color and/or effect paint systems.

21. Use of the clearcoat slurry as claimed in any one of claims 1 to 17 as an adhesive or sealing compound for producing adhesive films and seals.