CA2168451A1 - Coating composition comprising at least one polyester which contains hydroxyl groups, process for its preparation, and its use as basecoat and in processes for the production of amulticoat protective and/or decorative coating - Google Patents

Abstract

Coating composition based on polyesters which contain hydroxyl groups, process for the preparation, and its use as basecoat in the process for the production of a multicoat protective and/or decorative coating Abstract The present invention relates to coating compositions, especially basecoats, comprising at least one hydroxyl group-containing polyester, characterized in that 1. the hydroxyl group-containing polyester has a weight-average molecular weight Mw of 40,000-200,000 and a polydispersity Mw/Mn > 8, and 2. at least 50% by weight of aromatic dicarboxylic acids or their esterifiable derivatives have been employed for the preparation of the polyester, but with the maximum content of phthalic anhydride being 80% by weight and the percentages by weight being based in each case on the overall weight of the acid components employed for the preparation of the polyester.

The present invention also relates to processes for the preparation of the coating compositions and to its [sic] use as basecoat in the process for the production of a multicoat protective and/or decorative coating.

Description

21684~

~ L ~ L . ~
09.08.1993 ~ tr~

BASF Lacke + Farben Aktiengesellschaft, ~unst-r Coating composition comprt~ing at lea~t on~ polyester which contains hydroxyl y~ r ~ 8 for ~ts preparation, and its u~e a~ h~ oat and in proce~ses for th- product~on of a multicoat protoctive and/or decorative coat$ng The present invention relates to a coating composition, in particular a basecoat, comprising at least one polyester which contains hydroxyl groups.
The present invention also relates to a proce~s for the preparation of the coating compositions and to pro-cesses for the production of a multicoat protective and/or decorative coating on a substrate ~urface.
Finally, the invention alfio relates to the use of the coating compositions as ba~ecoat and to the use of the coating compositions in the refinishing of, in particular, motor vehicle bodies.

Especially in the finishing of motor vehicles, but also in other sectors where coatings which combine a good decorative effect with good protection against corrosion are desired, it is known to provide sub-strates with a plurality of ~uperposed coats. In this context, great importance has become attached to multi-coat finishes in which the substrate is first coated 5 ~

with a pigmented basecoat and subsequently a clearcoatis applied.

The preferred procedure here is the so-called wet-on-wet method, in which the basecoat is flashed off briefly without a hAki ng step, then the clearcoat i8 applied, and subsequently basecoat and clearcoat are cured together.

In the basecoat it i8 common to use metallic pigments which lead to the so-called metallic fini~hes. In order to achieve a good metallic effect it is of paramount importance to ensure a good disposition and fixing of the metallic pigments in the paint film. For this purpose it is necessary for the incipient dissolution undergone by the basecoat when the clearcoat is applied to the predried but not cured basecoat film to be very slight, or in some cases even nonexistent. On the other hand, a certain degree of incipient dissolution of the basecoat when the clearcoat i~ applied is wholly desirable, for reason~ of adhesion between ba~ecoat and clearcoat.

For the production of the multicoat coatings, both con-ventional (i.e. solvent-containing) basecoats and clearcoats and water-dilutable systems are employed.

For example, DE-A-40 24 204 and the International Patent Application bearing the Publication

2~ 6~5~

No. WO 88/02010 disclose multicoat coatings in which the conventional basecoat used is based on polyester resin, melamine resin, cellulose acetobutyrate and aluminum flakes. However, more detailed information on the polye~ter resin used and the type of cellulose acetobutyrate are contained in neither of the two documents.

In addition, DE-C-28 18 093 discloses multicoat coatings in which the ba~ecoat used is based on a polyester resin as film-forminq component, but in which no information is present on the molecular weight of the polyester in DE-C-28 18 093. As a component essen-tial to the invention, these basecoats described in DE-C-28 18 093 comprise polymer microparticles. These polymer microparticles are intended to lead to an improvement in the spray properties of the basecoat6.

The object of the present invention is therefore to provide coating compositions, especially basecoats, which have properties which are improved with respect to the known coating compositions. In particular, the coating compositions, when used as basecoats, should ensure both a good metallic effect of the multicoat finish and good adhesion to the clearcoat disposed on the basecoat. Furthermore, the coating compositions should cure at room temperature or slightly elevated temperature, so that they can be employed in automotive refinishing. They should also fulfill the requirements - 2 16~5 1 which are commonly placed on a basecoat. The coating compositions should therefore, for example, dry rapidly, be stable on storage and ~Yhihit over-coatability, good flop (a good metallic effect) and good adhesion to the clearcoat.

This object is surprisingly achieved by a coating com-po~ition, especially a basecoat, compri~ing at least one polyester which contains hydroxyl group~, the ~aid coating composition being characterized in that 1. the hydroxyl group-contA i n i~g polyester has a weight-average molecular weight Mw of 40,000-200,000 and a polydisper~ity Mw/Mn > 8, and 2. at least 50% by weight of aromatic dicarboxylic acids or their esterifiable derivatives have been employed for the preparation of the polye~ter, but with the maximum content of phthalic anhydride being 80~ by weight and the percentages by weight being based in each ca~e on the overall weight of the acid components employed for the preparation of the polyester.

The present invention also relates to a process for the preparation of these coating compositions.
In addition, the present invention also relates to a process for the production of a multicoat protective and/or decorative coating on a substrate surface, in 84~1 which 1. a basecoat i~ applied, 2. from the composition applied in step (1) a polymer film i8 formed on the surface

3. a transparent topcoat iB applied to the resulting basecoat, and

4. the topcoat i~ cured together with the basecoat, which proces~ iB characterized in that the ba~ecoat employed in step (1) is the coating composition accor-ding to the invention.

Finally, the pre6ent invention also relates to the use of the coating compofiitions a~ ba~ecoat and to the use of the coating compositions for refinishing, in particular for the refinishing of motor vehicle bodie~.

It is surprising and was not foreseeable that the coating compositions obtained with the polyesters u~ed in accordance with the invention ensure both a good metallic effect of the multicoat fini~h and good adhesion to the clearcoat which is disposed on the basecoat. Moreover, the coating composition~ have the advantage that they cure at room temperature or slightly elevated temperature and can thus be employed in automotive refinishing. A further advantage is that - 21684S~

the coating composition~ according to the invention fulfill the re~uirements conventionally placed on a basecoat. For example, the coating composition~ dry rapidly, are stable on ~torage and exhibit over-coatability, good flop and good adhe~ion to theclearcoat. Furthermore, they display good color uniformity even when mixed with basecoats based on other polyesters having different molecular weights and degrees of branching.

In the text below, then, the individual components of the coating composition according to the invention are described in more detail.

It iB essential to the invention that the coating compositions comprise as binder a hydroxyl y~u~
containing polyester having a weight-average molecular weight of 40,000-200,000, preferably from 50,000 to 120,000, and a polydispersity (the polydispersity is defined as the quotient of the weight-average molecular weight Mw and the number-average molecular weight Mn) of ~ 8, preferably > 8 to 200 and particularly preferably from 10 to 100. The weight-average and the number-average molecular weight in this context are determined by gel permeation chromatography against a polystyrene standard.

The hydroxyl group-cont~;ni ng polyesters preferably have OH nl~mher~ of 20-150 mg of KOHtg, preferably - 216~

60-110 mg of KO~/g. Moreover, these polyesters pre-ferably have acid numbers of 5-20 mg of KOH/g, particularly preferably 10-15 mg of KO~/g, and/or amine numbers of 0-40 mg of KOH/g.

Also essential to the invention is that, for the pre-paration of these hydroxyl group-cont~i n; ng polyesters, at least 50~ by weight of aromatic dicarboxylic acids are employed, but with the maximu~ content of phthalic anhydride being 80% by weight. It i6 further preferred for less than 20% by weight of cycloaliphatic dicar~oxylic acids to be employed. In this context the percentages by weight are based in each case on the overall weight of the acid components employed for the preparation of the polyesters. It is only this combina-tion of high weight-average molecular weight with broad molecular weight distribution and the use of a minimum proportion of aromatic dicarboxylic acids as structural component that ensures that the coating compositions have the good properties re~uired, and in particular good adhesion coupled with a good metallic effect.

The polyester employed in accordance with the invention are obtainable by reaction of a) polycarboxylic acids or their esterifiable deriva-tive~, together if de~ired with monocarboxylic acids, - ~168~51 b) polyols, together if desired with monools, c) if desired, further modifying components, and d) if desired, a component which is reactive with the reaction product of a), b) and, if appropriate, c ) .

It is essential to the invention that the acid com-ponent (a) employed for the preparation of the polye~ters comprises at least 50~ by weight of aromatic dicarboxylic acids or their esterifiable derivatives, based on the overall weight of the carboxylic acids employed for the preparation of the polyesters.
Inasmuch as phthalic anhydride is employed for the preparation of the polyesters, a maximum of 80% by weight of the acid component may comprise phthalic anhydride. Together with the aromatic dicarboxylic acids up to 50% by weight of ~lirh~tic and/or cycloaliphatic polycarboxylic acids may be employed. In this context it is preferred to employ less than 20% by weight, and particularly preferred to employ no cycloaliphatic di- or polycarboxylic acid~.

Example~ of aromatic dicarboxylic acids which are suitable for the preparation of the hydroxyl group-con-taining polyesters according to the invention are phthalic acid, isophthalic acid, terephthalic acid, halophthalic acids such as tetrachloro- and 2`~ s ~-tetrabromophthalic acid, and the like.

Examples of aliphatic dicarboxylic acids which are suitable for the preparation of the hydroxyl group-con-

5 tA i n i~g polyesters according to the invention areadipic acid, glutaric acid, acelaic tsic] acid, sebacic acid, fumaric acid, maleic acid, succinic acid, muconic acid, itaconic acid and the like.

Other suitable compounds are the esterifiable deriva-tives of the abovementioned polycarboxylic acid~, for example their monoesters or multiple esters with aliphatic alcohols having 1-4 carbon atoms or hydroxy alcohols having 1-4 carbon atoms. Moreover, it i~ also possible to employ the anhydrides of the acids men-tioned above, provided they exist.

If desired, it is also possible - together with the polycarboxylic acids - to employ monocarboxylic acids such as, for example, benzoic acid, tert-butylbenzoic acid, lauric acid, isononanoic acid and fatty acids of naturally occurring oils. The preferred monocarboxylic acid employed is isononanoic acid. The proportion of monocarboxylic acids is advantageously less than 20% by weight based on the overall weight of the carboxylic acids employed for the preparation of the polyester~.

It is preferred for the component (a) which is employed to comprise less than 20% by weight of and, in - 216~4~ 1 particular, no cycloaliphatic dicarboxylic acids, for example tetrahydrophthalic acid, hexahydrophthalic acid, cyclohexanedicarboxylic acids, 4-methylhexa-hydrophthalic acid, endomethylenetetrahydrophthalic acid, tricyclodecanedicarboxylic acid, endomethylene-hexahydrophthalic acid, camphoric acid, cyclo-hexanetetracarboxylic acid, cyclobutanetetracarboxylic acid etc.

Alcohol component~ (b~ which are ~uitable for the preparation of the polyester are polyhydric alcohols such as ethylene glycol, propanediols, butanediols, hexanediols, neopentyl glycol, diethylene glycol, cyclohexanediol, cyclohexanedimethanol, trimethyl-pentanediol, ethylbutylpropanediol, ditrimethylol-propane, trimethylolethane, trimethylolpropane, glycerol, pentaerythritol, dipentaerythritol, trishydroxyethyl isocyanate, polyethylene glycol, polypropylene glycol, together if desired with monohydric alcohols such as, for example, butanol, octanol, lauryl alcohol, and ethoxylated and/or propyoxylated t 8iC ] phenol.

Compounds which are suitable as component (c) for the preparation of the polyesters are in particular tho~e which have a group which iB reactive toward the func-tional groups of the polyester, with the exception of the compounds stated as component (d). As modifying component (c) it is preferred to use polyisocyanates - 2 ~ 3~ 8 ~

and/or diepoxide compounds, and also, if desired, monoisocyanates and/or monoepoxide compo~n~.
Examples of suitable polyisocyanates are tolylene diisocyanates, hexamethylene diisocyanates and isophorone diisocyanate. DiepoYi~e compounds are to be understood as epoxy resins contA i ni ng on average approximately 2 epoYi~e group~ per molecule. Examples of suitable monoepoxide compound6 are olefin oxides, such as octylene oxide, butyl glycidyl ether, allyl glycidyl ether, phenyl glycidyl ether, p-butylphenol glycidyl ether, cresyl glycidyl ether, styrene oxide, glycidyl methacrylate, glycidylhexanevinyl monoxide, dipentene monoxide, ~-pinene oxide and glycidyl esters of tertiary carboxylic acids.

Suitable examples of component (d) for the preparation of the polyesters are compounds which contain not only a group which is reactive towards the functional groups of the polyester but also a tertiary amino group.

As components ~d) which are reactive with the reaction product of (a), (b) and, if appropriate, Ic), pre-ference is given to the use of monoisocyanates con-tA i n ing at least one tertiary amino group. These com-pounds can be prepared, for example, by reactingsuitable diisocyanates, such as isophorone diiso-cyanate, with amino alcohols cont~ining a tertiary amino group, for example hydroxyethylpyridine or dimethylaminoethanol, or with polyamines cont~ining at - 2 ~ 4 j l least one tertiary and at least one secondary or primary amino group. The monoisocyanate~ are attached to the binder ~y6tem by reaction with free hydroxyl groups of the polyester, accompanied by the formation of a urethane formation [8iC]- As component (d) it is also possible to u~e polyamines contAin;ng at least one tertiary and at least one primary or secondary amino group. A corresponding example which may be mentioned is dimethylaminopropylamine.

Apart from by the use of component (d) (polymer-analo-gous reaction), the tertiary ~mino groups can also be introduced into the polyester by using polycarboxylic acids and/or polyo~s which contain amino groups.

As component (a), together with the polycarboxylic acids, it is pos6ible to use aminocarboxylic acids con-taining at least one tertiary amino group. Examples of these are pyridine-2-carboxylic acid, pyridine-3-carboxylic acid, pyridine-4-carboxylic acid and pyridine-2,6-dicarboxylic acid. Moreover, it is possible to u6e the reaction product of an amino alcohol containing at lea~t one tertiary amino group and a polycarboxylic anhydride, and the reaction pro-duct of a polyamine containing at least one tertiaryand at least one primary or secondary amino group and a polycarboxylic anhydride.

A8 alcohol component (b) it is possible to use amino 2 ~ S ~

alcohols contAining at least one tertiary amino group.
Examples of these are 2-hydroxyethylpyridine, dimethylaminopropanol, methyldiethanolamine, methyl-dipropanolamine and dihydroxyethylaniline.

As alcohol component (b) it is also possible to employ reaction product~ of epoxy resins with carboxylic acids and/or amines. Thus, the reaction product of low molecular weight epoxy resins with polycarboxylic acids and/or polycarboxylic anhydrides and aminocarboxylic acid~ cont~ining at least one tertiary amino group can be used as alcohol component (b), the product sub-sequently, if desired, being esterified with the acid component and the alcohol component and, if desired, modified with polyisocyanates. Low molecular weight epoxy resins are understood as epoxy resins having a molecular weight of less than approximately 2000. When epoxy resins are used, low-chlorine grades should be employed, since otherwise severe di6coloration of the products may occur.

The polyesters can be prepared by the known and conven-tional methods as are described, for example, in various stAn~rd works, for example 1. Temple C. Patton, Alkyd Resin Technology, Interscience Publishers John Wiley & Sons, New York, London 1962;

~6~5 1 2. Dr. Johanne~ Schreiber, Chemie und Technologie der kunstlichen ~arze [Chemistry and Technology of Synthetic Resins], Wissenschaftliche Verlagsge~ellschaft mb~, Stuttgart, 1943 s 3. Hans Wagner und Hans-Friedrich Sarx, Lackkunstharze tSynthetic Resin~ for Coatings], 4th edition, Karl-Hanser-Verlag, Mllnich~ 1959 0 4. Ullmanns Encyklopadie der Techni~-hen Chemie [Ullmann's Encyclopedia of Industrial Chemistry~, volume 14, pages ~0 to 106 (1963).

During the preparation of the polyester~ the water of reaction which is liberated or the Al~nols which are liberated are removed continuously. The esterification is virtually quantitative and can be monitored by deterr; ni ng the acid numbers and the O~ numbers. In this reaction the molecular weight and the degree of branching of the polyester can be regulated in a simple manner, familiar to the person skilled in the art, via the ratio in which the alcohol component~ (diol and polyol) and the di- and/or polycarboxylic acids are employed. For instance, the weight-average molecular weight Mw and the polydispersity Mw/Mn of the polyester is higher the closer the ratio of O~ to acid groups is to 1 and the higher the degree of branching. This is achieved by employing only a small excess of polyols and by continuing the conden~ation to a high conversion 21684~l of > 98~. The degree of branching is controlled by the proportion of compounds of relatively high functionality. The degree of branching, degree of con-densation and molar ratios of the polyols must be care-fully matched to one another to avoid gelation of thecondensation resin. The degree of branching of the polyester is higher the higher the proportion of struc-tural components having a functionality of 3 or more.
The smaller the degree of branching, the les6 the degree to which shifts in color occur if the coating compo~itions according to the invention are blended with basecoats based on other polyesters having different molecular weights and degrees of branching.
The degree of branching is preferably from 0.6 to 1.2 branches per 1000 g of polyester resin (solid).

In general the esterification conditions are selected such that the reaction is as complete as possible. In other words, reaction is continued until the desired acid number~ have been reached.

This reaction is conventionally carried out at tempera-tures of between 180 and 280C in the presence, if desired, of an appropriate esterification catalyst such as, for example, lithium octanoate, dibutyltin oxide, dibutyltin dilaurate, p-toluenesulfonic acid and the like.

Conventionally, the preparation of the polye~ters is 2~ ~4~1 carried out in the presence of small amounts of a suitable solvent as entraining agent. Examples of entraining agents employed are aromatic hydrocarbons such as, in particular, xylene, and cycloaliphatic hydrocarbons, for example cyclohexane.

If the reaction is carried out in the presence of an esterification catalyst, the latter is conventionally employed in a quantity of from 0.01 to 0.5% by weight, based on the solids content of polyester re6in solution and on the solids content of the cataly~t solution.

The coating composition~ according to the invention generally contain up to 20% by weight, preferably from

6 to 9% by weight, based in each case on the overall weight of the coating composition and on the solids content of the polyester re6in solution, of the hydroxyl group-containing polyester.

As further component, the coating composition6 accor-ding to the invention preferably contain at least one cellulo~e ester, preferably in quantities of 10-40~ by weight, particularly preferably from 15 to 30% by weight, ba~ed in each case on the content of film-forming solids and on the solid6 content of thecellulose eater solution. Example6 of 6uitable cellulose ester6 are cellulo6e nitrate, cellulose propionate, cellulo6e butyrate, cellulose aceto-butyrate, cellulose acetopropionate, mixture6 thereof ~. 6~ 15 ~

and the like. Cellulose acetobutyrate i8 preferably employed.
Especially if the coating compo~itions according to the invention are employed as metallic baQecoat, it is pre-ferred to employ a cellulose ester having a content of acetyl groups of 12-16% by weight, a content of buturyl ~sic] groups of 35-43% by weight and a content of hydroxyl groups of 1-2.5% by weight, and a weight-average molecular weight of 100,000-250,000 (number-average molecular weight 35,000-65,000). In the following text this cellulose acetobutyrate is called CABl for short.

If desired, another cellulo~e acetobutyrate - called CAB2 for short below - can al~o be employed for the preparation of metallic basecoat~. Thi~ CAB2 has a con-tent of acetyl groups of 1-5% by weight, a content of buturyl [8iC] group~ of 4~-52% by weight, a content of hydroxyl groups of 1-2.5~ by weight and a weight-average molecular weight of 100,000 to 250,000. For the preparation of the metallic basecoats it is pos~ible to employ mixtures of CAB1 and CAB2 in which the content of CAB1 is preferably at least 60% by weight based on the overall content of CABs. For the preparation of pigmented solid-color basecoats it is likewise pre-ferred to employ the CAB1 type or a mixture of CABl and CAB2 as cellulose esters. However, besides this it is al80 possible to use CAB2 alone.
Moreover, the coating compositions according to the 4~ ~

invention conventionally contain 60-90~ by weight, preferably 70-85~ by weight, based in each case on the overall weight of the coating composition, of at least one solvent.
Examples of ~uitable solvent~ are the solvents already mentioned for the preparation of the polyesters, and also ketones ~uch as acetone, methyl isobutyl ketone and the like.

The solvents preferably employed are esters, for example butyl acetate, l-methoxypropyl acetate, ethylene glycol diacetate, 2-ethoxyethyl acetate, butylglycol acetate, ethyldiglycol acetate and the like. Also suitable are aromatic compounds with relatively high degrees of substitution, for example Solvent Naphtha~, heavy benzole, various Solvesso~
grades, variou~ Shellsol~ grades and Dea~ol~, and higher-boiling aliphatic and cycloaliphatic hydrocarbons, for example various white spirits, mineral turpentine oil, tetralin, decalin, Depanol and the like.

The criteria for the selection of the solvent are, among other desired properties, that it should not react with the film-forming material and that it can be easily removed in the application and curing procedure.

The quantity of ~olvent i~ controlled such that the coating composition i~ rendered able to close the coating, or to let it flow, to give a smooth ~urface, 8 ~ ~ ~

thus en~uring an acceptable application. In spray application methods involving viscosity, the consistency of the coatings is controlled by the addition of a sufficient quantity of solvent such that the composition can be handled and can be applied to form an appropriate coating without the deficiencies which are known to occur in the spray method.

If desired, the coating compositions may also contain a crosslinking agent which is reactive toward the hydroxyl groups of the polyester. However, the formula-tion of physically drying coating compositions, i.e.
coating compositions free from crosslin~inq agent, is also possible. Should the coating compositions contain a crosslinking agent, it is conventionally employed in quantities of from 5 to 20% by weight based on the overall weight of the coating composition.

Examples of crosslinking agent~ which can be employed are polyisocyanates, for example aromatic isocyanates such as 2,4- and 2,6-tolylene diisocynate and mixtures thereof, 4,4'-diphenylmethane diisocyanate, m-phenylene, p-phenylene, 4,4-diphenyl, 1,5-naph-thalene, 1,4-naphthalene, 4,4-toluidine and xylylene dii~ocyanate and substituted aromatic systems such as dianisidine diisocyanates, 4,4 diphenyl ether diisocyanates or chlorodiphenylene diisocyanates and aromatic isocyanates of higher functionality, for exsmple 1, 3, 5-trii~ocyanatobenzene [~ic], ~ :~ 6 ~

4,4',4''-triisocyanatotriphenylmethane, 2,4,6-tri-isocyanatotoluene and 4,4'-diphenyldimethylmethane 2,2',5,5'-tetraisocyanate; cycloaliphatic isocyanates such as 1,3-cyclopentane, 1,4-cyclohexane, 1,2-cyclo-hexane and isophorone diisocyanate; and aliphaticisocyanates such as trimethylene, tetramethylene, pentamethylene, hexamethylene and trimethylhexa-methylene 1,6-diisocyanate, and tris-hexamethylene triisocyanate.

Furthermore, however, the polyisocyanates may also be linked to give prepolymers of higher molecular mass.
Compounds which can be mentioned in this context are adducts of tolylene dii~ocyanate and trimethylol-propane, a biuret formed from 3 molecules of hexa-methylene diisocyanate, and the trimer~ of hexamethy-lene diisocyanate and 3,5,5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane.

However, it is also possible to employ the isocyanates described above which have been reacted with conven-tional capping agent~, for example phenols, alcohols, acetoacetic esters, ketoxime- and ~-caprolactam. These combinations are stable at room temperature and in general cure only at temperature~ above 100C. In particular cases, for example when acetoacetic esters are used for capping, it i6 al~o pofifiible for crosslinking to occur below 100.

~ 5~tl~

The quantity of crosslinking agent employed iB
generally selected such that the ratio of the isocyanate groups of the crosslinking agent to the hydroxyl groups of the polyester is within the range from 1:3 to 3:1.

Combinations with polyisocyanates and/or resin~ bearing isocyanate group~ crosslink rapidly even at room tem-perature.

Amino resins can also be employed as crosslinking agents, examples being melamine/formaldehyde condensa-tion product~, benzoguanamine/formaldehyde condensation products, urea resins and the like. Examples of appro-priate ~m; no resins are, for example, the commerciallyavailable melamine resins Maprenal MF 600, MF650, MF 800 from Hoechst AG.
The quantity to be employed of these optionally employed amino resins is conventionally between 3 and 8% by weight, based on the weight of the coating compo-sition.

Furthermore, the coating compositions according to the invention may also, if desired, contain other resins such as polyurethane resins. Appropriate polyurethane resin~ generally have number-average molecular weight~
of from 3000 to 7000.

It is po~si~le, for example, to employ the polyurethane re~ins described in EP-A-355 433, DE-A-35 45 618 and DE-A 38 13 866. In addition to this, however, the employment of other polyurethane resins conventionally employed in basecoats is possible. The quantity to be employed of these polyurethane resins which are added if desired is conventionally between 15 and 40% by weight, based on the weight of the coating composition and on solid polyurethane resin.

Furthermore, the coating compositions according to the invention may also contain epoxy-ester resins, for example reaction products of epoxy resins and carboxylic acids, epoxide-modified acrylates and epoxide-modified polyesters. For example, the commercial epoxide-modified fatty acid polyester Uralac AB733X-90 from DSM Kunstharze GmbH can be employed.

The quantities to be employed of the~e optionally added, epoxide-modified resins is conventionally between 0 and 4% by weight, based on the weight of the coating composition.

If the coating compositions according to the invention are employed as basecoats, then they contain as further component pigments which are conventional in coating technology. Such pigments may have particle sizes in the range of 1-50 ~m and may be of inorganic nature, for example titanium dioxide, iron oxide, chromium oxide, lead chromate or carbon black, or of organic nature, for example phthalocyanine blue, phthalocyanine - ~16~l~5~

green, carbazol violet, anthrapyrimidine yellow, vlavanthrone tsic] yellow, isoindoline yellow, indanthrone blue, quinagrindone [sic] violet and pherylene [ 8iC ~ red. Of particular interest in this connection are metal pigments con~isting of flat flakes of aluminum, copper, tin, nickel or stainles~ steel, specifically because these can be used to obtain so-called metallic effects by means of which a differentiation is at~Ai n~ in the reflection of light in dependence on the angle of viewing. The quantity of these pigments employed i8 conventionally between 1 and 40% by weight, based on the overall weight of the coating composition.

In addition, the coating compositions may also contain conventionally employed fillers, for example silicic acid, talc, ~aolin, metallic oxides, silicates, ~ulfides and the like. These filler~ are conventionally employed in a quantity of between 0 and 10% by weight, based on the weight of the coating compo~ition. The coating compositions according to the invention may also contain conventional auxiliaries and additives in conventional quantitie~, preferably 0.01-10% by weight based on the overall weight of the coating composition.
Examples of suitable auxiliaries and additives are leveling agents such as silicone oils, plasticizers such as phosphates and phthalate6, viscosity-con-trolling additives, flatting agent~, W ab~orbers, light stabilizer~ and the like.

- 2~6~

The coating compositions preferably al~o contain, in addition, a crosslinking catalyst, conventionally in a quantity of up to 10% by weight based on the weight of the coating composition.

It is generally possible to dispense with the use of a crosslin~ing catalyst if the polyester already contain~
tertiary amino groups.

Examples of suitable cross1i~king catalysts are, for example, phosphoric acid, p-toluenesulfonic acid, tin dibutyl dilaurate, tin dioctyl dilaurate, amines, for example aliphatic diamines such as ethylenediamine and hexanediamine, and aliphatic polyamines such as diethylenetriamine, triethylenetetraamine and tetraethylenepentamine, and alicyclic amines such as piperidine, piperazine, aromatic amines, ethanolamine, triethylamine, diazabicyclooctane, amidines such as diazabicyclononene, diazabicycloundecene and low molecular weight basic siloxanes. Advantageously, from l to lO parts by weight of catalyst (solid) are used per lO0 parts by weight of polye~ter.

The coating compositions are prepared in a known manner by mixing and, if appropriate, di~persing the individual components. The coating compositions accord-ing to the invention can be applied to a sub~trate in the form of a film by spraying, flow coating, dipping, rolling, knife coating or brushing, the films ~ S~.J I

subsequently beinq cured to give a firmly adhering coating.

These coating compositions are cured conventionally at room temperature or slightly elevated temperature, advantageously at temperatures below 100C and pre-ferably at t~r~ratures below 80C. However, it is also possible for the coating composition6 to be cured under baking conditions, i.e. at temperatures of at least 100C.
Particularly suitable sub6trate~ are metals and al~o wood, plastic, glass and the like.
Because of the short curing time and low curing tem-perature6, the coating compositions according to the invention are preferably employed for automotive refinishing. However, depending on the crosslinking agent employed, they may al60 be employed for the pro-duction-line finishing of motor vehicles.

The coating composition~ according to the invention are also suitable a~ the ~ase color of a mixer sy6tem, in particular a mixer sy~tem in the area of refinishing.
It is particularly preferred for the coating composi-tions according to the invention to be employed in a 2S mixer system for the production of conventional coating compositions. Such mixer systems are de~cribed in, for example, the as yet unpublished German Application P 42 32 721Ø These mixer systems described therein are characterized in that they contain ~6~43 ~

A) various base color~ A which contain less than 5%
by weight of water, at least one pigment which provides color and/or effect, organic solvent, at least one water-dilutable or water-di~persible binder, and - if desired - auxiliaries and additives, B) at least one solvent-contAin;ng, binder-con-t~;ning, pigment-free component B which may con-tain up to 5% by weight of water, and if de~ired C) a component C contAini~g at least one crosslinking agent, and D) a component D which contains organic solvent, water if desired and, if desired, additives and catalysts.

The coating compositions according to the invention based on hydroxyl group-contAining polyesters and cellulose acetobutyrate are in this context employed for the preparation of component B. A particular advan-tage in thi~ ca~e is the good color uniformity of the resulting coating compo~ition~, especially if polyesters according to the in~ention and contAi~i ng hydroxyl groups, having a degree of branching of from 0.6 to 1.2 branches per 1000 g of polyester resin ~olid), are employed.

The crosslinking agents (C) employed are, for example, the crosslinking agents already mentioned. However, it i8 also possible to prepare physically drying coating composition~ using this mixer system, in which case component (C) can then be omitted.

The coating compositions according to the invention are preferably employed as basecoat for a multicoat finish of the basecoat/clearcoat type.

This mixer system has the special advantage, in particular from an economic viewpoint, that the base colors A contA; n; ng water-dilutsble or water-dis-persible binders provide the possibility of using only one series of base pastes both for aqueous systems and for tho~e dissolved in organic solvents. The use, in accordance with the invention, of essentially water-free and preferably completely water-free base colors offers the additional advantage that the containers which can be u~ed for the ~torage of these base colors do not have to be protected (for example by an appro-priate internal coating) against corrosion by water.
Furthermore, it is also possible, with certain pre-conditions, to employ water-sensitive pigments for the formulation of the base colors, resulting in a con-siderable increase in the selection of pigment~
available.

The individual components of the mixer sy~tem according 216~

to the invention will now be described below in more detail.

Component A of the mixer system may contain any pigments conventional for paint~, with the proviso that they do not react with wster within a short period (the period between combining components A and B and the application of the coatings) and that they are insoluble in water. In this context component A may contain effect pigments and/or color-providing pigments based on inorganic or organic compounds. In order to ensure a scope for application which i6 as near universal as possible and to maximize the number of colors which can be produced, it is preferred to con-struct a mixer system on the basis of components Awhich contain only color-providing pigments and com-ponents A which contain only effect pigments.

For the preparation of component A, it is possible to employ all effect pigments which are conventionally employed in the formulation of aqueous coating composi-tions. Examples of appropriate effect pigments are com-mercially available aluminum bronzes, the chromatized aluminum bronze~ according to DE-A 3636183, commer-cially available stainless-steel bronzes, and other conventional metal flakes and metal flake pigments.

Other pigments suitable for the preparation of com-ponent A are nonmetallic effect pigments, for example pearlescent and interference pigments. Examples of - '~ 1 6 ~

suitable color-providing pigments based on inorganics are titanium dioxide, iron oxides, carbon black and the like. Examples of suitable color-providing pigments based on organic co~rolln~ are indanthrene blue, cromophthal red, Irgazin orange, Sicotrans yellow, Heliogen green and the like.

Suitable binders for use in component A are all water-dilutable or water-dispersible binders which are con-ventionally employed in aqueous coating compositionsand which can be prepared in the form of organic solutions. The water-dilutability or water-dispersi-bility of the resins can also be adju~ted by the use of corresponding solubilizers as cosolvent or solvent.
Critical factors for the selection of the binders are, on the one hand, the good storage stability in organic solution, and in particular the ability to avoid settling of the pigments, and on the other hand the ability to incorporate the ba~e color into component B
without problems or to incorporate component s into the base color without problems.

The binders employed for component A are in particular water-dilutable and water-dispersible polyurethane resins, polyacrylate resins, polyester resins and amino resins, and mixture~ thereof, which can be prepared in organic solution.

The polyurethane resin~ employed as binders in the base - 2~

colors are known in principle. Suitable examples are the polyurethane resins described in the literature for use in water-based coatings, provided these polyurethane re6ins can be prepared - in modification of the preparation described in the respective literature - in the form of organic solutions.

Examples of suitable polyurethane resins are the resins described in the following documents: EP-A-355433, DE-A 3545618, DE-A 3813866 and DE-A 4005961.

Examples of suitable polyacrylate resins are, for example, the resins described in DE-A 38 32 826. Other suitable binders for component A are the polyester resins and amino resins which are dilutable or dis-persible in water and can be prepared in the form of organic solutions.

The present invention therefore also relates to a pro-cess for the production of a multicoat protectiveand/or decorative coating on a substrate surface, in which 1. a basecoat is applied, 2. a polymer film is formed on the surface from the composition applied in step (lJ, 3. a transparent topcoat is applied to the resulting - 2163~

basecoat, and 4. the topcoat is cured together with the basecoat, which i8 characterized in that the basecoat employed in step (1) is a coating composition according to the invention.

In this process, therefore, a transparent topcoat com-position i9 applied directly after the application ofthe basecoat composition, preferably after a short flush-off time without a baking step. Subsequently, the basecoat is baked together with the topcoat (wet-on-wet method). This curing of the basecoat and the topcoat is conventionally carried out at a temperature below 100C, preferably below 80C in the case of automotive refinishing. Otherwise, curing is carried out conven-tionally at a temperature of between 100 and 150~C and for a time between 15 and 30 minutes. The dry film thicknesses of the resulting basecoat are in general between 8 and 20 ~m, with those of the topcoat conven-tionally being between 20 and 60 ~m.

Examples of a suitable clearcoat for this process are the clearcoats described in EP-A-379 598 and based on hydroxyl-cont~; n; ng components, cellulose esters and isocyanates. Also suitable as clearcoat are the clearcoats described in DE-A-39 42 803 and based on polymers containing silyl groups, and the clearcoats 2~g4S~

described in DE-A-40 24 204 and based on hydroxyl group-cont~in;~g products of condensation and addition polymerization.

The invention i8 illu~trated in more detail in the following examples. All part~ and percentages are by weight, unless expre~sly stated otherwise.

1.1 Preparation of a hydroxyl group-cont~; n i ng polyester 1 The following raw materials are weighed into a 4 1 stainless steel vessel fitted with stirrer, steam-heated column with head temperature detector, and water ~eparator:

Neopentylglycol1,038.0 part~
Trimethylolpropane611.2 parts Phthalic anhydride1,264.6 parts 20 Adipic acid 831.7 parts Xylene 145.8 part~

The mixture is heated over the course of 1 hour to a temperature of 135C, at which the beginning of distil-lation can be observed. While maintA; n; ng a column headtemperature of below 100C, heating is continued slowly to a maximum product temperature of 210C. The water formed i8 removed continuously by azeotropic distilla-tion. After an acid number of from 12 to 14 mg of KO~/g 8~

and a vi~cosity from 18 to 19 dPa. 8 ( 60% in xylene, plate/cone viscometer at 23C) has been reached, the mixture is cooled and diluted with butyl acetate to a solids content of 80%. The resulting polyester resin 1 has a viscosity (measured using a plate/cone viscometer at 23C, 60% in xylene) of 14.2 dPa.s and a number-average molecular weight of 3000, as well as a weight-average molecular weight of 105,000 (determined by gel permeation chromatography against polystyrene as st~n~Ard). The polydispersity Mw/Mn is 35 and the 0 number is 96.5 mg of KOH/g.

1.2 Preparation of a hydroxyl group-cont~ining polyester 2 Example 2 corresponds to a re~in of the compo~ition of Example 1 with the exception that 0.05% of dibutyltin oxide is employed as catalyst (based on solid starting materials). The preparation process is identical. After an acid number of from 12 to 14 mg of RO~/g and a viscosity of from 13 to 15 dPa.~ (60% in xylene, plate/cone viscometer at 23C) have been reached, the mixture is cooled, diluted with 6% of xylene and, after a temperature of below 120C has been reached, is dis-solved further using butyl acetate to a solid6 contentof 65%. The resulting polyester resin 2 has a viscosity (measured with a platetcone viscometer at 23C, 60% in butyl acetate) of 13.5 dPa.s and a number-average molecular weight of 3100, and al~o a weight-average - ~16845~

molecular weight of 155,000 (determined by gel permeation chromatography against poly~tyrene as stAn~rd). The polydispersity Mw/Mn is 52 and the OH
number is 96 mg of ROH/g.

1.3 Preparation of a hydroxyl group-cont~i~ing polyester 3 The following raw materials are weighed into a 4 l stainless steel vessel fitted with stirrer, steam-heated column with head temperature detector, and water separator:

198 parts of trimethylolpropane 892 part~ of neopentylglycol 437 parts of phthalic anhydride 490 parts of isophthalic acid 1.15 parts of dibutyltin oxide The components are mixed and ~lowly melted under inert gas. Distillation commences at 140C. Samples are then taken hourly and a visual check iB made as to whether a clear melt is obtained. At an acid number of about 45 mg of KOH/g the melt became clear. Then the following further components are added to the melt:

575 parts of adipic acid 24 parts of xylene.

2 ~ 6 8 ~ ~ ~

Thereafter, heating i8 continued for 8-12 hourQ to 220C, while maintA; ni ng a column head temperature of not more than 100C. Condensation is effected up to an acid number of below 15 mg of KOH/g, at which point the viscosity i8 about 9.8 dPa.s (measured 60~ in xylene).
After the acid number has been reached, the resin is diluted with xylene to a theoretical solids content of 90% and with butyl acetate to a solids content of theoretically 65~. The polyester resin solution, in a 60% dilution with butyl acetate, has a viscosity of 9.8 dPa.s tICI plate/cone viscometer at 23C) and an acid number of 11.6 mg of ROH/g (based on solid~). The resulting polyester has a number-average molecular weight of 4500 g/mol, a weight-average molecular weight of 65,500 g/mol (measured by GPC against polystyrene a~
stAn~Ard), an OH number of 57 mg of KOH/g and a poly-dispersity Mw/Mn of 15.

1.4 Preparation of a hydroxyl group-containing polyester Cl The following raw materials are weighed into a 4 l stainless steel vessel fitted with stirrer, steam-heated column with head temperature detector, and water separator:

Neopentylglycol 730.3 parts Trimethylolpropane 537.4 parts Phthalic anhydride 890.0 parts 2 1 6 ~ Ll ~ ~

Adipic acid 585.0 parts Xylene 114.3 parts The mixture is heated over the course of 1 hour to a temperature of 135C, at which the beginning of distil-lation can be observed. While maintAi~ing a column head temperature of below 100C, heating is continued slowly to a maximum product t~mrerature of 210C. The water formed is removed continuously by azeotropic distilla-tion. After an acid number of from 12 to 14 mg of KOH/gand a viscosity of 6.1 dPa.s (60~ in 1-methoxypropyl acetate, plate/cone viscometer at 23C) have been reached, the mixture is cooled and diluted with butyl acetate to a solids content of 60%. The resulting polyester resin C1 has a viscosity (measured using a plate/cone viscometer at 23C) of 2.6 dPa.s and a number-average molecular weight of 2050, and also a weight-average molecular weight of 9100 (determined by gel permeation chromatography against polystyrene as standard). The polydispersity Mw/Mn is 5, the OH number is 146 mg of KOH/g.

1.5 Preparation of a hydroxyl group-cont~i n ing polyester C2 The following raw materials are weighed into a 4 1 stainless ~teel vessel fitted with stirrer, steam-heated column with head temperature detector, and water separator:

- ~ 6~15~

Trimethylolpropane 992.8 parts Isononanoic acid 365.8 parts Benzoic acid 282.9 parts Hexahydrophthalic anhydride 528.1 parts 5 Cyclohexanedicarboxylic acid 589.8 parts Xylene 115 parts The components are mixed and slowly melted under inert gas. Distillation commences at 140C. Thereafter, heating is continued to 220C over the course of from 5 to 7 hours, while maint~i n; ng a column head temperature of not more than 100C. Condensation i~ effected up to an acid number of less than lS mg of ROH/g, at which point the viscosity is 8.5 dPa. B (mea~ured 55% in butyl acetate, plate/cone viscometer at 23~C). After the acid number has been reached, the resin is run off as a melt. Processible solutions of the resin can be pre-pared by melting and dilution with the desired solvent.
The viscosity in xylene at a solids content of 55% is 9.1 dPa.s (plate/cone viscometer at 23C). The resul-ting polyester C2 has a number-average molecular weight of 2250 and a weight-average molecular weight of 247,000 (measured by gel permeation chromatography against polystyrene as st~n~rd). The polydispersity Mw/Mn is 110, the OH number is 111 mg of KOH/g.

- 2~6~

1.6 Preparation of a hydroxyl group-contA i n ing polye6ter C3 The following raw material6 are weighed into a 4 1 stainless steel vessel fitted with stirrer, steam-heated column with head temperature detector, and water separator:

Neopentylglycol 1006.1 parts 10 Trimethylolpropane 356.3 parts Adipic acid 1763.4 parts Dibutyltin oxide 0.675 part Xylene 112.5 parts The component~ are mixed and slowly melted. Distilla-tion commences at 135C. Thereafter heating is con-tinued to 220 over the cour~e of from 5 to 7 hour~, while maintA;n;ng a column head temperature of not more than 100C. Condensation is effected up to an acid number of 16 mg of ROH/g, at which point the viscosity is 8.5 dPa. 8 (measured 60% in xylene, plate/cone Vi9-cometer at 23C). After the de~ired values have been reached the mixture is cooled, diluted with xylene to a ~olids content of 90~ and diluted further with butyl acetate to a ~olids content of 65%. The vi~c06ity of the resin solution is 17.8 dPa.s (plate/cone viscometer at 23C), the acid num~er i~ 15.5 mg of RO~/g. The resulting polyester C3 ha~ a number-average molecular weight of 3294 and a weight-average molecular weight of '~ 68 1~ ~

260,000 (measured by gel permeation chromatography against polystyrene as ~tAnAArd). The polydispersity Mw/Mn is 79, the OH number i6 75 mg of KOH/g.

1.7 Preparation of a hydroxyl group-contA;n;ng polyester C4 The following raw materials are weighed into a 4 1 stainless steel ve~sel fitted with stirrer, steam-heated column with head temperature detector, and waterseparator:

188.0 parts of trimethylolpropane 829.0 parts of neopentylglycol 151443.0 parts of hexahydrophthalic anhydride 96.0 parts of xylene.

Also added to the mixture iB 0.05%, based on solid 6tarting materials, of a tin catalyst (hydrogenated monbutyltin ~sic] oxide, trade name Fascat 4100 from Atochem Nederland).

The components are mixed and melted slowly under inert gas. Distillation commence~ at 140C. Thereafter heating i8 continued to 220C over the course of 5-7 hours, while maintA; n; ng a column head temperature of not more than 100C. Condensation is effected up to an acid number of below 10 mg of KO~/g, at which point the visco~ity is about 14.5 dPa.s (measured 60% in xylene).

~ ~ 6 ~

After the acid number has been reached the resin i6 diluted with xylene to a theoretical solids content of 90% and with butyl acetate to a solids content of theoretically 65%. In a 60% dilution with butyl acetate, the polyester resin solution has a viscosity of 8.8 dPa.s (ICI plate/cone viscometer at 23C) and an acid number of 8.0 mg of KOH/g (based on solids).
The resulting polyester has a number-average molecular weight of 3250 g/mol, a weight-average molecular weight of 61,000 g/mol. (measured by GPC again~t polystyrene as stAn~Ard), a polydispersity MM[sic3/Mn of 19 and an OH number of 46 mg of KOH/g.

2.1 Cellulose acetobutyrate solution 1 A cellulose acetobutyrate solution contA;ning 15% CAB
and 85% butyl acetate was employed. The cellulose acetobutyrate used has a content of acetyl groups of from 13 to 16%, a content of butyryl groups of from 36 to 42%, a content of hydroxyl groups of from 1 to 2%
and a weight-average molecular weight of approximately 40,000.

2.2 Cellulose acetobutyrate solution 2 The cellulose acetobutyrate solution 2 used has a cellulose acetobutyrate content of 15% and a butyl acetate content of 85%. The cellulose acetobutyrate has a content of from 2.5 to 4% of acetyl groups, a content 216~

of butyryl groups of from 36 to 42~ and a content of hydroxyl groups of from 1 to 2%. The weight-average molecular weight of the cellulose acetobutyrate is approximately 40,000.

3. Preparation of basecoats 1 to 4 and Cl to C5 The preparation of the coating compositions according to the invention is carried out by the conventional methods by first pre-stirring the wax precipitation until the wax precipitation is free from inhomo-geneities. The cellulose acetobutyrate solution is then added with rapid stirring. After this the remaining components, except for the aluminum pigment and the solvent, are added. The aluminum pigment is first made into a paste with 5 parts of butyl acetate and this paste is added to the other components while stirring.
Then the remaining quantities of solvent are also added. The composition of basecoats 1 to 4 and Cl to C5 is indicated in Table 1. The ba6ecoats are applied to sheet metal panels 40 x 60 cm in size. The primer used was a commercially available, conventional filler (commercial product Glasurit Grundfuller [primer ~urfacer] EP AC 01-1492 from Glasurit GmbH, Munster, with an epoxy-functional binder and an amino-functional curing agent). The filler was applied by spraying and, after a flash-off time of 10 min, was then dried at 80C for 20 min. The dry film thickness of the filler is from 50 to 80 ~m. After this the respective basecoat - 21G~

was applied by spray application, applying 1 spray pass first and, after a flash-off time of 5 min, a 2nd spray pass. After a flash-off time of 20 min, likewise at room temperature, the clearcoat was applied.

The clearcoat used for o~ercoating was the commercially available clearcoat Gla~urit AF 23-0185 from Glasurit GmbH based on a polyacrylate (similar to Macrynal~
SM 513 from Hoechst AG), mixed in a ratio of 2:1 with the curing agent SC 29-0173 from Glasurit Gmb~ based on isocyanate (mixture of a trimerized isocyanate which contains isocyanurate groups and i~ based on hexamethy-lene dii~ocyanate and isophorone diisocyanate). The clearcoat was applied by spraying, carrying out one 6pray pas~ and, after a flash-off time of 2 min, a second spray pass. After a flash-off time of 10 min at ambient temperature the panel is then dried at 60C for 30 min. The film thickness of the basecoat is 20-25 ~m, while that of the clearcoat is 60-80 ~m.

The test results of the coating~ are compiled in Table 2.

o o oo o o o o a~ ~ o ..... . .

o o o o o o o o a~ ~ o .................. ... -U~ ~ --I N

O O O O O O O ~ ~lO
. . . . .

U~ O O O O O O O O CO ~ O
O O~ ~ --I
_l o o o o o o o o a~ ~ o O O O O O O O O C~ ~ O
o . . .....

C: O O O O O O O O 00 N O
o o O O O O O O IS~ O

rl O O O O O O O O CO ~ O
O ~ t`~ N
o C O
O Q~ ~rl O
O ~O C
O r~l r~l r~ r~l r~1 ^ 11 r~l ~rl ~
O O~ --.rl Ll ~ ~ I U r~
- ---- u a~
rl O~ Il) ~ O
rl ~ r~l r~
m ~ x ,~
O ~ r~
E~ U ~ X m m u~ ~

- ~63 151 1) Cellulose acetobutyrate solution 1 (see above) 2) Cellulose acetobutyrate solution 2 (see above) 3~ Wax precipitation 1 The wax precipitation was prepared by heating an initial charge of 44 parts of xylene to 80-100C.
Then 6 part~ were added of a commercially available ethyl-vinyl acetate copolymer (commercial product EVA l-Wachs BASF~ from BASF
AG, Ludwigshafen; polyethylene wax based on an ethlyene tsic]/vinyl acetate copolymer having a melting point of 87-92C, a Hoppler hardness at 23C of 110-140 bar and a molar mas~ of approximately 6500 g/mol) and the resulting solu-tion was stirred until a clear solution formed.
Then 50 parts of butyl acetate 98 were added and the solution wa~ left to cool.

0 4) Commercially available melamine resin having a solids content of 55%, dissolved in isobutanol, and a viscosity DIN 4 of from 90 to 130 8, and isobutanol as etherification alcohol (commercial product Maprenal MF 650 from ~oechst AG) 5) Commercially available aluminum pigment (non-leafing type) with a content of white ~pirit of 18% and of aromatic solvents of 20% and with an average particle size of 9 microns (commercial ~ ~ 6 ~

product Sparkle Silver 7005 AR from Silberline Ltd., Scotland).

6) A commercially available paint diluent was employed consisting of 20% xylene, 5% butylglycol acetate, 60% butyl acetate 98 and 15%
l-methoxypropyl 2-acetate.

7) Solution of 1 part of a commercially available silicone oil (commercial product Baysilone OL44 from Bayer AG) in 99 parts of xylene

8) Solution of 10 parts of diazabicyclooctane (DABCO) in 45 parts of butyl acetate and 45 parts of butanol ~6~51 O ~ ~ ~ W

Cl . L
r O~ O
~ ~ O1` ~ 0 ~1~ 0 ~ ~ ~ Ll C~ ~ ~ o o ~ O
Ll ~ ~ ~-- ~ Ll U ~ ,1 0 C ~ o ~ _ 0 U --~ ~ I I I I
m '~ e" O U~ O O

Ei o U ~ O O . ~
c O ~ O O r~ _ .c o~
o o ~ --' o m O
U~ tO
~r _ r~
u ~r u~
Z ,~ d' L ~ L
r ~ ~ _ _ 0 ~ ~ N
_ o o o u~ u~ o a a L ~ ~ U U ~p - 216~15~

1) Adhe~ion test The adhesion te~t is carried out using a high-pressure cleaner at 80 bar pressure and a flow rate of 800 l/h at a cold temperature. The distance of the nozzle from the test panel was 5 cm. For te~ting the adhesion the coated steel panels (~ee above) were stored at room temperature for 7 day~ and thus dried. A knife is then used to cut a triangle with side~ 10 cm long through the coating film~. The cut must extend down to the substrate. Subsequently the ~ide~ of the triangle are exposed to the high-pre~sure cleaner jet for 10 sec each.

Evaluation:
A metal lattice cut into squares with a mesh size of 1/2" and a total edge length of 6" ~144 squares) is laid over the triangle. Each square in which there is a loss of adhesion between the clearcoat and basecoat is counted.

2) The colors are measured by DIN 6174, stAn~Ard lighting D, using the three-angle mea~urement in~trument MMX 111 from Datacolor, Weichenheim, Germany. Each color was measured on a mixture of 80 parts by weight of coating compo~itions 1 to 3 and C2 to C5 with 20 parts by weight of coating composition Cl. The mixture was adjusted to spray visco~ity, from 18 to 20 s efflux time in the - 21G~

DIN 4 cup, with the paint diluent indicated above.
The parameter measured in each case was the DC*
value in compari60n to coating compo6ition Cl (C1 = stAn~Ard). Measurement was carried out in each case at an angle to the vertical of 25, 45 and 70.

DC* po6itive: sample is more colored in comparison with stA~rd Cl (in this case more blue) DC* negative: sample is les~ colored in comparison with ~tAn~Ard C1 (in this case more metallic) 3) StAn~Ard: coating composition C1 (see above) 4) Visual as6e6sment wa6 carried out at angles of 25, 45 and 70 to the vertical under an O~ram~ white-univer6al neon tube.

Claims (14)

claims 1. Coating composition, especially basecoat, com-prising at least one polyester which contains hydroxyl groups, which is characterized in that

1. the hydroxyl group-containing polyester has a weight-average molecular weight Mw of 40,000-200,000 and a polydispersity Mw/Mn > 8, and 2. at least 50% by weight of aromatic dicarboxylic acids or their esterifiable derivatives have been employed for the preparation of the polyester, but with the maximum content of phthalic anhydride being 80% by weight and the percentages by weight being based in each case on the overall weight of the acid components employed for the preparation of the polyester.

2. Coating composition according to claim 1, charac-terized in that the hydroxyl group-containing polyester has a weight-average molecular weight Mw of from 50,000 to 120,000 and/or a polydispersity Mw/Mn of > 8 to 200.

3. Coating composition according to claim 1 or 2, characterized in that the hydroxyl group-con-taining polyester contains less than 20% by weight, based on the overall weight of the acid components employed for the preparation of the polyester, of cycloaliphatic dicarboxylic acids.

4. Coating composition according to one of claims 1 to 3, characterized in that the hydroxyl group-containing polyester has a degree of branching of from 0.6 to 1.2 branches per 1000 g of polyester resin (solid).

5. Coating composition according to one of claims 1 to 4, characterized in that the hydroxyl group-containing polyester has an OH number of from 20 to 150 mg of KOH/g, preferably from 60 to 110 mg of KOH/g.

6. Coating composition according to one of Claims 1 to 5, characterized in that the hydroxyl group-containing polyester has an acid number of from 5 to 20 mg of KOH/g, preferably from 10 to 15 mg of KOH/g, and/or an amine number of from 0 to 40 mg of KOH/g.

7. Coating composition according to one of claims 1 to 6, characterized in that it contains at least one cellulose ester.

8. Coating composition according to claim 7, charac-terized in that the coating composition contains cellulose acetobutyrate having a weight-average molecular weight of from 100,000 to 250,000 and a content of acetyl groups of from 12 to 16% by weight, a content of butyryl groups of from 35 to 43% by weight and a content of hydroxyl groups of from 1 to 2.5% by weight, based in each case on the overall weight of the cellulose acetobutyrate, and/or contain cellulose acetobutyrate having a weight-average molecular weight of from 100,000 to 250,000 and a content of acetyl groups of from 1 to 5% by weight, a content of butyryl groups of from 48 to 52% by weight and a content of hydroxyl groups of from 1 to 2.5% by weight, based in each case on the weight of the cellulose acetobutyrate.

Process for the preparation of the coating com-positions according to one of claims 1 to 8, characterized in that the hydroxyl group-con-taining polyester, if desired cellulose ester, solvent and, if desired, crosslinking agents, if desired pigments, if desired fillers and, if desired, other auxiliaries and additives are pro-cessed by mixing and, if desired, dispersing to give a coating composition, in particular to give a basecoat.

10. Process for the production of a multicoat protec-tive and/or decorative coating on a substrate surface, in which 1. a basecoat is applied, 2. from the composition applied in step (1) a polymer film is formed on the surface, 3. a transparent topcoat is applied to the resul-ting basecoat, and 4. the topcoat is cured together with the basecoat, characterized in that the basecoat employed in step (1) is a coating composition according to one of claims 1 to 8.

11. Process according to claim 10, characterized in that the topcoat is cured together with the basecoat at temperatures of below 100°C, preferably below 80°C.

12. Article coated with a single-coat or multicoat coating, characterized in that at least one of the coats comprises a coating composition according to one of claims 1 to 8.

13. Use of the coating compositions according to one of claims 1 to 8 as basecoat.

14. Use of the coating compositions according to one of claims 1 to 8 for refinishing, especially for the refinishing of motor vehicle bodies.