METHOD FOR PRODUCING A MULTI-LAYERED COATING

Abstract

A method is disclosed for producing a multicoat paint system on a metallic substrate by producing a basecoat or a plurality of directly successive basecoats directly on a metallic substrate coated with a cured electrocoat system, producing a clearcoat directly on the one or the topmost of the plurality of basecoats, and subsequently jointly curing the one or the plurality of basecoats and the clearcoat. At least one basecoat material used for producing the basecoats includes at least one predispersed mixture including at least one polyamide having an acid number of less than 20 mg KOH/g, at least one polymeric resin different from the polyamide, and also water and at least one organic solvent.

Claims

1. A method for producing a multicoat paint system on a metallic substrate, comprising: (1) producing a cured electrocoat on the metallic substrate by electrophoretic application of an electrocoat material to the substrate and subsequent curing of the electrocoat material, (2) producing a basecoat or two or more directly successive basecoats directly on the cured electrocoat by application of an aqueous basecoat material directly to the cured electrocoat or directly successive application of two or more basecoat materials to the cured electrocoat, (3) producing a clearcoat directly on the basecoat or on a topmost basecoat by application of a clearcoat material directly to the basecoat or to the topmost basecoat, (4) jointly curing the basecoat and the clearcoat or the basecoats and the clearcoat, wherein the aqueous basecoat material or at least one of the basecoat materials comprises at least one predispersed mixture, the at least one predispersed mixture comprising at least one polyamide having an acid number of less than 20 mg KOH/g, at least one polymeric resin different from the at least one polyamide, and also water and at least one organic solvent.

2. The method as claimed in claim 1, wherein the at least one polyamide has an acid number of less than 15 mg KOH per g.

3. The method as claimed in claim 1, wherein the at least one polyamide has an acid number of 0.1 to less than 15.0 mg KOH per g.

4. The method as claimed in claim 1, wherein a relative weight ratio of the at least one polymeric resin to the at least one polyamide in the at least one predispersed mixture is in a range from 15:1 to 2.0:1.

5. The method as claimed in claim 1, wherein a fraction of the at least one predispersed mixture based on a total amount of the aqueous basecoat material or of the at least one basecoat material, is 5 to 30 wt %, the at least one polyamide being present in a fraction of 0.15 to 3.0 wt %, based on the total amount of the aqueous basecoat material or of the at least one basecoat material.

6. The method as claimed in claim 1, wherein the at least one polymeric resin in the at least one predispersed mixture comprises at least one polyester, the polyester having an acid number of 20 to 50 mg KOH per g and an OH number of 20 to 300 mg KOH per g.

7. The method as claimed in claim 1, wherein the aqueous basecoat material or at least one of the basecoat materials, comprises at least one polymer as binder, different from the at least one polymeric resin and selected from the group consisting of hydroxy-functional polyurethanes, polyesters, polyacrylates, and copolymers of these polymers.

8. The method as claimed in claim 1, wherein the aqueous basecoat material or at least one of the basecoat materials, comprises at least one melamine resin as crosslinking agent.

9. The method as claimed in claim 1, wherein the aqueous basecoat material or at least one of the basecoat materials, are one-component coating compositions.

10. The method as claimed in claim 1, wherein the jointly curing (4) is carried out at temperatures of 100 to 250° C. for a time of 5 to 60 min.

11. The method as claimed in claim 1, wherein a percentage sum of a solids content and a fraction of water of the aqueous basecoat material or of at least one of the basecoat materials is at least 70 wt %.

12. The method as claimed in claim 1, wherein the at least one predispersed mixture comprises at least one emulsifier selected from the group consisting of lecithinens and C.sub.12-C.sub.24 fatty alcohol polyglycol ethers.

13. The method as claimed in claim 1, wherein the at least one polyamide has a number-average molecular weight in a range from 250 g/mol to 3000 g/mol.

14. The method as claimed in claim 1, wherein an automobile body is used as the metallic substrate.

15. A multicoat paint system produced by the method as claimed in claim 1.

16. The method as claimed in claim 1, wherein the aqueous basecoat material or all of the basecoat materials comprise at least one polymer as binder, different from the at least one polymeric resin and selected from the group consisting of hydroxy-functional polyurethanes, polyesters, polyacrylates, and copolymers of these polymers.

17. The method as claimed in claim 1, wherein the aqueous basecoat material or all of the basecoat materials comprise at least one melamine resin as crosslinking agent.

18. The method as claimed in claim 1, wherein the aqueous basecoat material or all of the basecoat materials are one-component coating compositions.

19. The method as claimed in claim 11, wherein the percentage sum of the solids content and the fraction of water of the aqueous basecoat material or of at least one of the basecoat materials is 80 to 90 wt %.

20. The method as claimed in claim 11, wherein the percentage sum of the solids content and the fraction of water of the aqueous basecoat material or of all of the basecoat materials is 80 to 90 wt %.

Description

EXAMPLES

Solids Content (Nonvolatile Fraction)

[0196] The nonvolatile fraction is determined according to DIN EN ISO 3251 (date: June 2008). It involves weighing out 1 g of sample into an aluminum dish which has been dried beforehand, drying it in a drying oven at 125° C. for 60 minutes, cooling it in a desiccator and then reweighing it. The residue relative to the total amount of sample used corresponds to the nonvolatile fraction. The volume of the nonvolatile fraction may optionally be determined if necessary according to DIN 53219 (date: August 2009).

[0197] Film Thicknesses

[0198] The film thicknesses are determined according to DIN EN ISO 2808 (date: May 2007), method 12A, using the MiniTest® 3100-4100 instrument from ElektroPhysik.

[0199] Acid Number

[0200] The acid number is determined in accordance with DIN EN ISO 2114 (date: June 2002), proceeding fundamentally according to “method A”. The acid number corresponds to the mass of potassium hydride in mg that is needed to neutralize 1 g of sample under the conditions specified in DIN EN ISO 2114. The acid number of a carboxy-functional component in an otherwise carboxyl-free sample, as for example of a polyamide in a dilution of the polyamide obtainable as a commercial product, can be obtained by corresponding conversion (taking account of the solids content, in other words the actual active substance of the sample or the amount of polyamide in the dilution). It is also possible for the component, such as the polyamide, to be isolated beforehand and then for the acid number to be determined on the polyamide itself, in other words, ultimately, on the solids portion of the dilution available for example as a commercial product.

[0201] The indication selected above that the procedure adopted was in principle (in other words, in general) that according to “method A” from the stated standard, should be understood as follows: where a sample or a component isolated beforehand does not dissolve fully in the solvent mixture indicated in the standard, an alternative solvent mixture was used in order to dissolve the sample or component completely. Where appropriate, operation also took place at slightly elevated temperatures, 30° C. for example, in order to ensure complete dissolution prior to titration. Typically for example, complete dissolution of various commercial polyamide products such as Disparlon AQ600, can be achieved in 2:1 v/v xylene:propanol.

[0202] Although it is of course possible in principle to determine the acid number with the solvent mixture specified in the standard, in which case possibly not all of the carboxy functions present are detected, a reproducible and representative result is nevertheless obtained by always measuring a completely dissolved sample or component in the context of the present invention.

[0203] OH Number

[0204] The OH number is determined in accordance with DIN 53240-2 (date: November 2007). The OH groups are reacted by acetylation with an excess of acetic anhydride. The excess acetic anhydride is then split by addition of water to form the acetic acid, and the entire acetic acid is back-titrated with ethanolic KOH. The OH number indicates the amount of KOH in mg which is equivalent to the amount of acetic acid bound in the acetylation of 1 g of sample.

[0205] Determination of the Number-Average and Weight-Average Molecular Weights

[0206] The number-average molecular weight (M.sub.n) is determined by gel permeation chromatography (GPC). This method of determination is based on DIN 55672-1 (date: August 2007). As well as the number-average molecular weight, the weight-average molecular weight (M.sub.w) and also the polydispersity (ratio of weight-average molecular weight (M.sub.w) to number-average molecular weight (M.sub.n)) can also be determined by this method. The eluent used is tetrahydrofuran. The determination takes place against polystyrene standards. The column material consists of styrene-divinylbenzene copolymers.

[0207] Determination of the Storage Stability

[0208] For determining the storage stability of basecoat materials, they are investigated before and after storage at 40° C. for 2 weeks with a rotational viscometer that is in accordance with DIN 53019-1 (date: September 2008) and is calibrated according to DIN 53019-2 (date: February 2001), under temperature-controlled conditions (23.0° C.±2.0° C.). In this analysis, the samples are first sheared for 5 minutes at a rate of 1000 s.sup.−1 (loading phase) and then for 8 minutes at a rate of 1 s.sup.−1 (unloading phase). The average viscosity level during the loading phase (high-shear viscosity) and also the level after 8 minutes of unloading phase (low-shear viscosity) are determined from the measurement data, and the values before and after storage are compared with one another, by calculating the respective percentage changes.

[0209] Painting of Waterborne Basecoat Material Wedge Constructions

[0210] To assess the incidence of pinholes and also the flow as a function of film thickness, wedge-format multicoat paint systems are produced in accordance with the following general protocols:

[0211] Variant A: First Waterborne Basecoat Material as Wedge, Second Waterborne Basecoat Material as Constant Coat

[0212] A steel panel with dimensions of 30×50 cm, coated with a cured standard CEC (CathoGuard® 800 from BASF Coatings), is provided with two adhesive strips (Tesaband adhesive tape, 19 mm) at one longitudinal edge, to allow determination of film thickness differences after coating.

[0213] The first waterborne basecoat material is applied electrostatically as a wedge with a target film thickness (film thickness of the dried material) of 0-30 μm. After flashing at room temperature for 3 minutes, one of the two adhesive strips is removed and then the second waterborne basecoat material is applied likewise electrostatically in a single application. The target film thickness (film thickness of the dried material) is 13-16 μm. After a further flashing time of 4 minutes at room temperature, the system is interim-dried in a forced air oven at 60° C. for 10 minutes. Following removal of the second adhesive strip, a commercial two-component clearcoat material (ProGloss® from BASF Coatings GmbH) is applied by gravity-fed spray gun manually to the interim-dried system, with a target film thickness (film thickness of the dried material) of 40-45 μm. The resulting clearcoat film is flashed at room temperature (18 to 23° C.) for 10 minutes; subsequently, curing takes place in a forced air oven at 140° C. for a further 20 minutes.

[0214] Variant B: First Waterborne Basecoat Material as Constant Coat, Second Waterborne Basecoat Material as Wedge

[0215] A steel panel with dimensions of 30×50 cm, coated with a cured standard CEC (CathoGuard® 800 from BASF Coatings), is provided with two adhesive strips (Tesaband adhesive tape, 19 mm) at one longitudinal edge, to allow determination of film thickness differences after coating.

[0216] The first waterborne basecoat material is applied electrostatically with a target film thickness (film thickness of the dried material) of 18-22 μm. After flashing at room temperature for 3 minutes, one of the two adhesive strips is removed and then the second waterborne basecoat material is applied likewise electrostatically in a single application as a wedge. The target film thickness (film thickness of the dried material) is 0-30 μm. After a further flashing time of 4 minutes at room temperature, the system is interim-dried in a forced air oven at 60° C. for 10 minutes. Following removal of the second adhesive strip, a commercial two-component clearcoat material (ProGloss® from BASF Coatings GmbH) is applied by gravity-fed spray gun manually to the interim-dried system, with a target film thickness (film thickness of the dried material) of 40-45 μm. The resulting clearcoat film is flashed at room temperature (18 to 23° C.) for 10 minutes; subsequently, curing takes place in a forced air oven at 140° C. for a further 20 minutes.

[0217] Assessment of the Incidence of Pinholes

[0218] To assess the incidence of pinholes, multicoat paint systems are produced as per the methods for the painting of waterborne basecoat material wedge systems (variant A and B, respectively), and are then evaluated visually according to the following general protocol:

[0219] The dry film thickness of the overall waterborne basecoat material system, consisting of the first and second waterborne basecoat materials, is checked and, for the basecoat film thickness wedge, the 0-20 μm region and the region from 20 μm to the end of the wedge are marked on the steel panel.

[0220] The pinholes are evaluated visually in the two separate regions of the waterborne basecoat material wedge. The number of pinholes per region is counted. All results are standardized to an area of 200 cm.sup.2. In addition, optionally, a record is made of that dry film thickness of the waterborne basecoat material wedge from which pinholes no longer occur.

[0221] Assessment of the Film Thickness-Dependent Leveling

[0222] To assess the film thickness-dependent leveling, multicoat paint systems are produced as per the methods for the painting of waterborne basecoat material wedge systems (variant A or B, respectively), and are then evaluated according to the following general protocol:

[0223] The dry film thickness of the overall waterborne basecoat material system, consisting of the waterborne basecoat material or of the first and second waterborne basecoat materials, is checked and, for the basecoat film thickness wedge, the 15-20 μm and also 20-25 μm regions, or 10-15 μm, 15-20 μm, 20-25 μm, 25-30 μm, and, optionally, 30-35 μm regions are marked on the steel panel.

[0224] The determination or assessment of the film thickness-dependent leveling takes place by means of the Wave scan instrument from Byk/Gardner within the four basecoat film thickness regions determined beforehand. For this purpose, a laser beam is directed at an angle of 60° onto the surface under investigation, and the fluctuations in the reflected light in the so-called short wave range (0.3 to 1.2 mm) and in the so-called long wave range (1.2 to 12 mm) are recorded by the instrument over a measuring distance of 10 cm (long wave=LW; short wave=SW; the lower the values, the better the appearance). Moreover, as a measure of the sharpness of an image reflected in the surface of the multicoat system, the instrument determines the characteristic variable “distinctness of image” (DOI) (the higher the value, the better the appearance).

[0225] Assessment of the Incidence of Gel Specks

[0226] To assess the incidence of gel specks, the basecoat materials are investigated according to the following general protocols:

[0227] a) Coating of a Glass Panel

[0228] The waterborne basecoat material in question is applied using a 150 μm four-way bar applicator to a glass panel with dimensions 9×15 cm. In the wet state and also after a 60-minute flashoff time at room temperature, the film is inspected for gel specks, by holding it against a light source, so that any air inclusions are not misinterpreted as gel specks. A rating of 1-5 is awarded (1=no specks/5=very many specks), or a judgment is made relative to a reference (reference=0; ++=much better; +=better; −=poorer; −−=much poorer).

[0229] b) Coating of a Steel Panel

[0230] The waterborne basecoat material is applied by dual application to a steel panel with dimensions of 32×60 cm, coated with a cured standard CEC (CathoGuard® 800 from BASF Coatings); application in a first step is electrostatic, with a target film thickness of 8-9 μm, and in the second step, after a 2-minute flashoff time at room temperature, application is pneumatic, with a target film thickness of 4-5 μm. Subsequently, after a further flashoff time at room temperature of 5 minutes, the resulting waterborne basecoat film is dried in a forced air oven at 80° C. for 5 minutes. Applied to the dried waterborne basecoat film is a commercial two-component clearcoat material (ProGloss from BASF Coatings GmbH), with a target film thickness of 40-45 μm. The resulting clearcoat film is flashed off at room temperature for 10 minutes; it is then cured in a forced air oven at 140° C. for a further 20 minutes. Specks are evaluated visually; a rating of 1-5 is awarded (1=no specks/5=very many specks).

[0231] Visual Evaluation of Separation

[0232] The basecoat materials are evaluated visually for stability, by storing them in each case in a closed glass vessel at room temperature and/or at 40° C. over a period of at least four weeks. This is followed by inspection to determine whether separation has taken place or whether the material has changed in its homogeneity. A rating of 1-5 is awarded (1=very stable; no separation and/or no formation of multiple phases/5=very unstable; severe separation or very distinct formation of multiple phases).

[0233] 1. Preparation of Mixtures Comprising Polyamides and Preparation of Aqueous Basecoat Materials

[0234] The following should be taken into account regarding the formulation constituents and amounts thereof that are indicated in the tables which follow. When reference is made to a commercial product or to a preparation protocol described elsewhere, the reference, independently of the principal designation selected for the constituent in question, is to precisely this commercial product or precisely the product prepared with the referenced protocol.

[0235] Accordingly, where a formulation constituent possesses the principal designation “melamine-formaldehyde resin” and where a commercial product is indicated for this constituent, the melamine-formaldehyde resin is used in the form of precisely this commercial product. Any further constituents present in the commercial product, such as solvents, must therefore be taken into account if conclusions are to be drawn about the amount of the active substance (of the melamine-formaldehyde resin).

[0236] If, therefore, reference is made to a preparation protocol for a formulation constituent, and if such preparation results, for example, in a polymer dispersion having a defined solids content, then precisely this dispersion is used. The overriding factor is not whether the principal designation that has been selected is the term “polymer dispersion” or merely the active substance, for example, “polymer”, “polyester”, or “polyurethane-modified polyacrylate”. This must be taken into account if conclusions are to be drawn concerning the amount of the active substance (of the polymer).

[0237] All proportions indicated in the tables are parts by weight.

[0238] 1.1 Preparation of Predispersed Mixtures (vdM) and Other Mixtures Comprising Polyamides

[0239] The components listed in tables 1.1 and 1.2 are stirred together in the order stated, with stirring at a temperature of 15-25° C., to give mixtures (vdM) 1 to 6 for inventive use. This mixture is then homogenized with stirring for a further 10 minutes. Stirring was carried out using the “Dispermat® LC30” device from VWA-Getzmann, Germany at a peripheral speed of the stirring disk used of 15 to 20 m/s.

TABLE-US-00001 TABLE 1.1 Preparation of mixtures (vdM) 1 to 4 (vdM) (vdM) (vdM) (vdM) 1 2 3 4 Melamine-formaldehyde resin 23.9 26.7 (Cymel ® 303 from Allnex) Melamine-formaldehyde resin 26.7 (Resimene ® 755 from Ineos) Melamine-formaldehyde resin 23.5 (Resimene ® HM 2608 from Ineos) Dimethylethanolamine 0.8 0.5 0.5 0.4 Disparlon ® A670-20M, available 13.7 16.2 16.2 14.3 from Kusomoto Chemicals, Ltd. Butyl glycol 32.9 32.5 32.5 28.7 2,4,7,9-tetramethyl-5-decynediol, 3.6 4.9 4.9 4.3 52% in BG (available from BASF SE) Polyester; prepared as for 25.1 19.2 19.2 28.7 example D, column 16, lines 37-59 of DE 40 09 858 A1

TABLE-US-00002 TABLE 1.2 Preparation of mixtures (vdM) 5 and (vdM) 6 (vdM) (vdM) 5 6 Polyester; prepared as for 22.50 22.50 example D, column 16, lines 37-59 of DE 40 09 858 A1 Dimethylethanolamino 0.45 0.45 2,4,7,9-tetramethyl-5-decynediol, 3.00 3.00 52% in BG (available from BASF SE) LIPOTIN ® A, available from Evonik 3.00 3.00 Industries AG Deionized water 56.05 56.05 Disparlon ® 6900-20X, available from 15.00 Kusomoto Chemicals, Ltd. Disparlon ® A670-20M, available from 15.00 Kusomoto Chemicals, Ltd.

[0240] The components listed in table 1.3 are stirred together in the order stated with stirring to give the polyamide-containing mixtures PM 1 and 2, to be used for comparison. This mixture is subsequently stirred intensely for 10 minutes.

TABLE-US-00003 TABLE 1.3 Preparation of the polyamide-containing mixtures PM 1 and 2 PM 1 PM 2 Disparlon ® AQ630, available from 20 Kusomoto Chemicals, Ltd. Disparlon ® AQ600, available from 50 Kusomoto Chemicals, Ltd. Isobutanol 18.5 Deionized water 78.5 31.5 2,4,7,9-Tetramethyl-5-decynediol, 1 52% in BG (available from BASF SE) Agitan ® 282 from Münzing Chemie 0.5 GmbH

[0241] The polyamide in the commercial product Disparlon® AQ600 from Kusumoto Chemicals, Ltd (nonvolatile fraction of the commercial product: 20 wt %) possesses an acid number of 66 mg KOH/g. The polyamide in the commercial product Disparlon® AQ630 from Kusumoto Chemicals, Ltd (nonvolatile fraction of the commercial product: 18 wt %) possesses an acid number of 75 mg KOH/g. The polyamide in the commercial product Disparlon® A670-20M from Kusumoto Chemicals, Ltd (nonvolatile fraction of the commercial product: 20 wt %) possesses an acid number of 9 mg KOH/g. The polyamide in the commercial product Disparlon® 6900-20X from Kusumoto Chemicals, Ltd (nonvolatile fraction of the commercial product: 20 wt %) possesses an acid number of 0.9 mg KOH/g.

[0242] 1.2 Preparation of Aqueous Basecoat Materials

[0243] 1.2A Preparation of aqueous basecoat materials WBM A1 (comparative) and WBM A2 (comparative)

[0244] The components listed under “Aqueous phase” in table A are combined with stirring in the order stated to form an aqueous mixture. This mixture is then stirred for 10 minutes and adjusted using deionized water and dimethylethanolamine to a pH of 8 and to a spray viscosity of 90 mPa.Math.s under a shearing load of 1291 s.sup.−1, as measured using a rotary viscometer (Rheolab QC instrument with C-LTD80/QC heating system from Anton Paar) at 23° C.

TABLE-US-00004 TABLE A Preparation of waterborne basecoat materials WBM A1 and WBM A2 WBM A1 WBM A2 Aqueous phase: 3% strength Na Mg phyllosilicate 15.23 15.23 solution Deionized water 5.68 1-Propoxy-2-propanol 1.41 1.41 2-Ethylhexanol 0.87 0.87 Polyurethane-based graft copolymer; 26.51 prepared as per page 35, line 33 to page 36, line 22 (example D-B2) of WO 2015/007427 A1 Aqueous dispersion of a 31.23 poly(meth)acrylate emulsion polymer having a nonvolatile fraction of 26-28% Polyester; prepared as per 3.66 page 28, lines 13 to 33 (example BE1) of WO 2014/033135 A2 Polyester; prepared as per 4.85 example D, column 16, lines 37-59 of DE 40 09 858 A1 Melamine-formaldehyde resin 5.44 5.44 (Cymel ® 203 from Allnex) 10% strength dimethylethanolamine in 0.55 0.30 water 2,4,7,9-Tetramethyl-5-decynediol, 1.09 1.09 52% in BG (available from BASF SE) Triisobutyl phosphate 1.63 1.63 Polyurethane-modified polyacrylate; 2.91 2.91 prepared as per page 7, line 55 to page 8, line 23 of DE 4437535 A1 Butyl glycol 4.35 4.35 Isopar ® L, available from Exxon Mobil 1.84 1.84 Pluriol ® P900, available from BASF SE 0.54 0.54 Hydrosol A170, available from DHC 0.54 0.54 Solvent Chemie GmbH White paste 25.68 25.68 Black paste 1.53 1.52 Yellow paste 0.54 0.54

[0245] Preparation of the White Paste

[0246] The white paste is prepared from 50 parts by weight of titanium rutile 2310, 6 parts by weight of a polyester prepared as for example D, column 16, lines 37-59 of DE 40 09 858 A1, 24.7 parts by weight of a binder dispersion prepared as per patent application EP 022 8003 B2, page 8, lines 6 to 18, 10.5 parts by weight of deionized water, 4 parts by weight of 2,4,7,9-tetramethyl-5-decynediol, 52% in BG (available from BASF SE), 4.1 parts by weight of butyl glycol, 0.4 part by weight of 10% strength dimethylethanolamine in water, and 0.3 part by weight of Acrysol RM-8 (available from The Dow Chemical Company).

[0247] Preparation of the Black Paste

[0248] The black paste is prepared from 57 parts by weight of a polyurethane dispersion prepared as per WO 92/15405, page 13, line 13 to page 15, line 13, 10 parts by weight of carbon black (Monarch® 1400 carbon black from Cabot Corporation), 5 parts by weight of a polyester prepared as per example D, column 16, lines 37-59 of DE 40 09 858 A1, 6.5 parts by weight of a 10% strength aqueous dimethylethanolamine solution, 2.5 parts by weight of a commercial polyether (Pluriol® P900, available from BASF SE), 7 parts by weight of butyl diglycol, and 12 parts by weight of deionized water.

[0249] Preparation of the Yellow Paste

[0250] The yellow paste is prepared from 37 parts by weight of Bayferrox 3910 (available from Lanxess), 49.5 parts by weight of an aqueous binder dispersion prepared as per WO 91/15528, page 23, line 26 to page 25, line 24, 7.5 parts by weight of Disperbyk®-184 (available from BYK-Chemie GmbH), and 6 parts by weight of deionized water.

[0251] 1.2B Preparation of Aqueous Basecoat Materials WBM B1 (Comparative), WBM B2 (Inventive) and WBM B3-6 (Comparative)

[0252] The components listed under “Aqueous phase” in table B are combined with stirring in the order stated to form an aqueous mixture. This mixture is then stirred for 10 minutes and adjusted using deionized water and dimethylethanolamine to a pH of 8 and to a spray viscosity of 110±10 mPa.Math.s under a shearing load of 1000 s.sup.−1, as measured using a rotary viscometer (Rheolab QC instrument with C-LTD80/QC heating system from Anton Paar) at 23° C.

TABLE-US-00005 TABLE B Preparation of waterborne basecoat materials WBM B1 to WBM B6 WBM WBM WBM WBM WBM WBM B1 B2 B3 B4 B5 B6 Aqueous phase: 3% Na—Mg phyllosilicate 13.54 solution (vdM) 1 17.52 PM 1 12.06 18.09 PM 2 3.95 5.60 Deionized water 8.03 18.81 2-Ethylhexanol 1.54 1.54 1.54 1.54 1.54 1.54 Aqueous dispersion of 44.04 44.04 44.04 44.04 44.04 44.04 poly(meth)acrylate emulsion polymer having a nonvolatile fraction of 26-28% Polyester; prepared as per 4.40 4.40 4.40 4.40 4.40 example D, column 16, line 37-59 of DE 40 09 858 A1 Melamine-formaldehyde resin 3.96 3.96 3.96 3.96 3.96 (Cymel ® 303 from Allnex) 10% dimethylethanolamine in 1.21 1.21 1.21 1.21 1.21 water 2,4,7,9-Tetramethyl-5-decynediol, 0.63 0.63 0.63 0.63 0.63 0.63 52% in BG (available from BASF SE) Pluriol ® P900, available from BASF SE 1.26 1.26 1.26 1.26 1.26 1.26 Triisobutyl phosphate 0.55 0.55 0.55 0.55 0.55 0.55 NACURE 2500, available from 0.72 0.72 0.72 0.72 0.72 0.72 King Industries, Inc Butyl glycol 5.18 5.18 5.18 5.18 5.18 50 wt % solution of Rheovis ® PU1250 0.63 0.63 0.63 0.63 0.63 0.63 in butyl glycol (Rheovis ® PU1250 available from BASF SE) Black paste 14.31 14.31 14.31 14.31 14.31 14.31 Fraction of polyamide 0.00% 0.48% 0.48% 0.48% 0.67% 0.67% in basecoat:

[0253] Preparation of Black Paste

[0254] The black paste is prepared from 57 parts by weight of a polyurethane dispersion prepared as per WO 92/15405, page 13, line 13 to page 15, line 13, 10 parts by weight of carbon black (Monarch® 1400 carbon black from Cabot Corporation), 5 parts by weight of a polyester prepared as per example D, column 16, lines 37-59 of DE 40 09 858 A1, 6.5 parts by weight of a 10% strength aqueous dimethylethanolamine solution, 2.5 parts by weight of a commercial polyether (Pluriol® P900, available from BASF SE), 7 parts by weight of butyl diglycol, and 12 parts by weight of deionized water.

[0255] 1.2C Preparation of Aqueous Basecoat Materials WBM B7 and B9 (Comparative) and Also WBM B8 and WBM 10 (Inventive)

[0256] The components listed under “Aqueous phase” in table C are combined with stirring in the order stated to form an aqueous mixture. This mixture is then stirred for 10 minutes and adjusted using deionized water and dimethylethanolamine to a pH of 8 and to a spray viscosity of 60±5 mPa.Math.s (WBM B7, WBM B9) or 80±5 mPa.Math.s (WBM B8, WBM B10) under a shearing load of 1000 s.sup.−1, as measured using a rotary viscometer (Rheolab QC instrument with C-LTD80/QC heating system from Anton Paar) at 23° C.

TABLE-US-00006 TABLE C Preparation of waterborne basecoat materials WBM B7 to WBM B10 WBM B7 WBM B8 WBM B9 WBM B10 Aqueous phase: 3% Na—Mg phyllosilicate 12.29 12.29 solution (vdM) 2 14.45 (vdM) 3 14.44 Deionized water 8.74 13.50 8.73 13.50 n-propanol 0.82 0.82 0.82 0.82 n-butoxypropanol 1.29 1.29 1.29 1.29 2-ethylhexanol 2.60 2.60 2.60 2.60 Aqueous dispersion of 42.73 42.73 42.74 42.74 poly(meth)acrylate emulsion polymer having a nonvolatile fraction of 26-28% Polyester; prepared as per 2.77 2.77 example D, column 16, line 37-59 of DE 40 09 858 A1 Melamine-formaldehyde resin 3.86 (Cymel ® 303 from Allnex) Melamine-formaldehyde resin 3.86 (Resimene ® 755 from Ineos) 10% dimethylethanolamine in water 0.28 0.28 2,4,7,9-Tetramethyl-5-decynediol, 1.30 1.30 1.30 1.30 52% in BG (available from BASF SE) BYK-346, available from 0.43 0.43 0.43 0.43 Altana/BYK-Chemie GmbH Isopropanol 1.54 1.54 1.54 1.54 Butyl glycol 0.94 0.94 0.94 0.94 Isopar ® L, available from 0.82 0.82 0.82 0.82 Exxon Mobil NACURE 2500, available from 0.40 0.40 0.40 0.39 King Industries, Inc Black paste 13.13 13.13 13.13 13.13 Barium sulfate paste 3.00 3.00 3.00 3.00 Steatite paste 3.05 3.05 3.05 3.05

[0257] Preparation of Black Paste

[0258] The black paste is prepared from 57 parts by weight of a polyurethane dispersion prepared as per WO 92/15405, page 13, line 13 to page 15, line 13, 10 parts by weight of carbon black (Monarch® 1400 carbon black from Cabot Corporation), 5 parts by weight of a polyester prepared as per example D, column 16, lines 37-59 of DE 40 09 858 A1, 6.5 parts by weight of a 10% strength aqueous dimethylethanolamine solution, 2.5 parts by weight of a commercial polyether (Pluriol® P900, available from BASF SE), 7 parts by weight of butyl diglycol, and 12 parts by weight of deionized water.

[0259] Preparation of Barium Sulfate Paste

[0260] The barium sulfate paste is prepared from 39 parts by weight of a polyurethane dispersion prepared as per EP 0228003 B2, page 8, lines 6 to 18, 54 parts by weight of barium sulfate (Blanc fixe micro from Sachtleben Chemie GmbH), 3.7 parts by weight of butyl glycol, and 0.3 part by weight of Agitan 282 (available from Münzing Chemie GmbH), and 3 parts by weight of deionized water.

[0261] Preparation of Steatite Paste

[0262] The steatite paste is prepared from 49.7 parts by weight of an aqueous binder dispersion prepared as per WO 91/15528, page 23, line 26 to page 25, line 24, 28.9 parts by weight of steatite (Microtalc IT extra from Mondo Minerals B.V.), 0.4 part by weight of Agitan 282 (available from Münzing Chemie GmbH), 1.45 parts by weight of Disperbyk®-184 (available from BYK-Chemie GmbH), 3.1 parts by weight of a commercial polyether (Pluriol® P900, available from BASF SE) and 16.45 parts by weight of deionized water.

[0263] 1.2D Preparation of Aqueous Basecoat Materials WBM B11 (Comparative) and WBM B12(Inventive)

[0264] The components listed under “Aqueous phase” in table D are combined with stirring in the order stated to form an aqueous mixture. This mixture is then stirred for 10 minutes and adjusted using deionized water and dimethylethanolamine to a pH of 8 and to a spray viscosity of 90±5 mPa.Math.s under a shearing load of 1000 s.sup.−1, as measured using a rotary viscometer (Rheolab QC instrument with C-LTD80/QC heating system from Anton Paar) at 23° C.

TABLE-US-00007 TABLE D Preparation of waterborne basecoat materials WBM B11 and WBM B12 WBM B11 WBM B12 Aqueous phase: 3% Na—Mg phyllosilicate 4.20 solution (vdM) 5 8.20 Deionized water 6.36 4.57 Butyl glycol 4.00 4.00 2-Ethylhexanol 3.55 3.55 Aqueous dispersion of 13.96 13.96 poly(meth)acrylate emulsion polymer having a nonvolatile fraction of 26-28% Polyester; prepared as per 4.85 3.01 example D, column 16, line 37-59 of DE 40 09 858 A1 Deionized water 4.20 30 wt % aqueous Rheovis ® AS 1130 0.42 solution, available from BASF SE Melamine-formaldehyde resin 7.70 7.70 (Cymel ® 203 from Allnex) 2,4,7,9-Tetramethyl-5-decynediol, 1.80 1.65 52% in BG (available from BASF SE) 10% dimethylethanolamine in water 1.08 0.88 Pluriol ® P900, available from BASF SE 0.10 0.10 Triisobutyl phosphate 2.50 2.50 White paste 51.90 51.90 Yellow paste 0.12 0.12 Black paste 0.11 0.11 Steatite paste 2.40 2.40

[0265] Preparation of White Paste

[0266] The white paste is prepared from 34 parts by weight of titanium rutile R 2310, 43.3 parts by weight of an aqueous dispersion of a poly(meth)acrylate emulsion polymer having a nonvolatile fraction of 26-28%, 3.9 percent by weight of butylglycol, 16.7 parts by weight of deionized water and 2.1 parts by weight of Disperbyk®-184 (available from BYK-Chemie GmbH).

[0267] Preparation of Yellow Paste

[0268] The yellow paste is prepared from 47 parts by weight of Sicotan Yellow L 1912, 45 parts by weight of an aqueous binder dispersion prepared as per WO 91/15528, page 23, line 26 to page 25, line 24, 2.7 percent by weight of 1-propoxy-2-propanol, 2.8 parts by weight of deionized water, 1.5 parts by weight of Disperbyk®-184 (available from BYK-Chemie GmbH), and 1 part by weight of Aerosil R 972 (available from Evonik Industries).

[0269] Preparation of Black Paste

[0270] The black paste is prepared from 40 parts by weight of Bayferrox 318 M (available from Lanxess), 39 parts by weight of an aqueous binder dispersion prepared as per WO 91/15528, page 23, line 26 to page 25, line 24, 2.0 percent by weight of 1-propoxy-2-propanol, 11.1 parts by weight of deionized water, 0.5 part by weight of Agitan 282 (available from Münzing Chemie GmbH), 4.4 parts by weight of Pluriol® P900 (available from BASF SE) and 3 parts by weight of 10% dimethylethanolamine in water.

[0271] Preparation of Steatite Paste

[0272] The steatite paste is prepared from 49.7 parts by weight of an aqueous binder dispersion prepared as per WO 91/15528, page 23, line 26 to page 25, line 24, 28.9 parts by weight of steatite (Microtalc IT extra from Mondo Minerals B.V.), 0.4 part by weight of Agitan 282 (available from Münzing Chemie GmbH), 1.45 parts by weight of Disperbyk®-184 (available from BYK-Chemie GmbH), 3.1 parts by weight of a commercial polyether (Pluriol® P900, available from BASF SE) and 16.45 parts by weight of deionized water.

[0273] 1.2E Preparation of Aqueous Basecoat Materials WBM B13 (Comparative) and WBM B14 (Inventive)

[0274] The components listed under “Aqueous phase” in table E are combined with stirring in the order stated to form an aqueous mixture. This mixture is then stirred for 10 minutes and adjusted using deionized water and dimethylethanolamine to a pH of 8 and to a spray viscosity of 85±5 mPa.Math.s under a shearing load of 1000 s.sup.−1, as measured using a rotary viscometer (Rheolab QC instrument with C-LTD80/QC heating system from Anton Paar) at 23° C.

TABLE-US-00008 TABLE E Preparation of waterborne basecoat materials WBM B13 and WBM B14 WBM WBM B13 B14 Aqueous phase: 3% Na—Mg phyllosilicate 15.23 solution (vdM) 5 20.00 1-Propoxy-2-propanol 1.41 1.41 2-Ethylhexanol 0.87 0.87 Aqueous dispersion of 18.13 18.13 poly(meth)acrylate emulsion polymer having a nonvolatile fraction of 26-28% Polyester; prepared as per 6.00 2.50 example D, column 16, line 37-59 of DE 40 09 858 A1 Melamine-formaldehyde resin 5.44 5.44 (Resimene ® HM 2608 from Ineos) 10% Dimethylethanolamine in 0.60 0.30 water 2,4,7,9-Tetramethyl-5-decynediol, 1.09 1.09 52% in BG (available from BASF SE) Butyl glycol 4.35 4.35 Isopar ® L, available from Exxon Mobil 1.84 1.84 Hydrosol A170, available from DHC 0.54 0.54 Solvent Chemie GmbH Pluriol ® P900, available from BASF SE 1.63 1.63 Triisobutyl phosphate 0.80 0.80 Tinuvin ® 384-2, available from BASF SE 0.40 0.40 Tinuvin ® 123, available from BASF SE 54.31 54.31 White paste 0.12 0.12 Yellow paste 0.11 0.11 Black paste 2.23 2.23 Steatite paste

[0275] Preparation of White Paste

[0276] The white paste is prepared from 34 parts by weight of titanium rutile R 2310, 43.3 parts by weight of an aqueous dispersion of a poly(meth)acrylate emulsion polymer having a nonvolatile fraction of 26-28%, 3.9 percent by weight of butylglycol, 16.7 parts by weight of deionized water and 2.1 parts by weight of Disperbyk®-184 (available from BYK-Chemie GmbH).

[0277] Preparation of Yellow Paste

[0278] The yellow paste is prepared from 47 parts by weight of Sicotan Yellow L 1912, 45 parts by weight of an aqueous binder dispersion prepared as per WO 91/15528, page 23, line 26 to page 25, line 24, 2.7 percent by weight of 1-propoxy-2-propanol, 2.8 parts by weight of deionized water, 1.5 parts by weight of Disperbyk®-184 (available from BYK-Chemie GmbH), and 1 part by weight of Aerosil R 972 (available from Evonik Industries).

[0279] Preparation of Black Paste

[0280] The black paste is prepared from 57 parts by weight of a polyurethane dispersion prepared as per WO 92/15405, page 13, line 13 to page 15, line 13, 10 parts by weight of carbon black (Monarch® 1400 carbon black from Cabot Corporation), 5 parts by weight of a polyester prepared as per example D, column 16, lines 37-59 of DE 40 09 858 A1, 6.5 parts by weight of a 10% strength aqueous dimethylethanolamine solution, 2.5 parts by weight of a commercial polyether (Pluriol® P900, available from BASF SE), 7 parts by weight of butyl diglycol, and 12 parts by weight of deionized water.

[0281] Preparation of Steatite Paste

[0282] The steatite paste is prepared from 49.7 parts by weight of an aqueous binder dispersion prepared as per WO 91/15528, page 23, line 26 to page 25, line 24, 28.9 parts by weight of steatite (Microtalc IT extra from Mondo Minerals B.V.), 0.4 part by weight of Agitan 282 (available from Münzing Chemie GmbH), 1.45 parts by weight of Disperbyk®-184 (available from BYK-Chemie GmbH), 3.1 parts by weight of a commercial polyether (Pluriol® P900, available from BASF SE) and 16.45 parts by weight of deionized water.

[0283] 1.2F Preparation of Aqueous Basecoat Materials WBM B15 (Comparative) and WBM B16 (Inventive)

[0284] The components listed under “Aqueous phase” in table F are combined with stirring in the order stated to form an aqueous mixture. This mixture is then stirred for 10 minutes and adjusted using deionized water and dimethylethanolamine to a pH of 8 and to a spray viscosity of 110±10 mPa.Math.s (WBM 15) or 140±10 mPa.Math.s (WBM B16) under a shearing load of 1000 s.sup.−1, as measured using a rotary viscometer (Rheolab QC instrument with C-LTD80/QC heating system from Anton Paar) at 23° C.

TABLE-US-00009 TABLE F Preparation of waterborne basecoat materials WBM B15 and WBM B16 WBM WBM B15 B16 Aqueous phase: 3% Na—Mg phyllosilicate 13.10 solution (vdM) 4 14.65 Deionized water 10.53 16.33 n-Propanol 0.87 0.87 n-butoxypropano1 1.38 1.38 2-Ethylhexanol 2.77 2.77 Aqueous dispersion of 35.24 35.24 poly(meth)acrylate emulsion polymer having a nonvolatile fraction of 26-28% Polyester; prepared as per 2.95 example D, column 16, line 37-59 of DE 40 09 858 A1 Melamine-formaldehyde resin 4.10 (Resimene ® HM 2608 from Ineos) 10% Dimethylethanolamine in 0.30 Water 2,4,7,9-Tetramethyl-5-decynediol, 1.38 1.38 52% in BG (available from BASF SE) BYK-346, available from 0.46 0.46 Altana/BYK-Chemie GmbH Polyurethane-modified polyacrylate; 2.77 2.77 prepared as per page 7, line 55 to page 8, line 23 of DE 4437535 A1 Isopropanol 1.64 1.64 Butyl glycol 1.00 1.00 Isopar ® L, available from Exxon Mobil 0.87 0.87 NACURE 2500, available from 0.42 0.42 King Industries, Inc Black paste 12.99 12.99 Blue paste 0.78 0.78 Barium sulfate paste 3.21 3.21 Steatite paste 3.25 3.25

[0285] Preparation of Black Paste

[0286] The black paste is prepared from 57 parts by weight of a polyurethane dispersion prepared as per WO 92/15405, page 13, line 13 to page 15, line 13, 10 parts by weight of carbon black (Monarch® 1400 carbon black from Cabot Corporation), 5 parts by weight of a polyester prepared as per example D, column 16, lines 37-59 of DE 40 09 858 A1, 6.5 parts by weight of a 10% strength aqueous dimethylethanolamine solution, 2.5 parts by weight of a commercial polyether (Pluriol® P900, available from BASF SE), 7 parts by weight of butyl diglycol, and 12 parts by weight of deionized water.

[0287] Preparation of Blue Paste

[0288] The blue paste was prepared from 69.8 parts by weight of a polyurethane dispersion prepared as per WO 92/15405, page 13, line 13 to page 15, line 13, 12.5 parts by weight of Paliogen® Blue L 6482 (available from BASF SE), 1.5 parts by weight of 10% strength aqueous dimethylethanolamine solution, 1.2 parts by weight of a commercial polyether (Pluriol® P900, available from BASF SE), and 15 parts by weight of deionized water.

[0289] Preparation of Barium Sulfate Paste

[0290] The barium sulfate paste is prepared from 39 parts by weight of a polyurethane dispersion prepared as per EP 0228003 B2, page 8, lines 6 to 18, 54 parts by weight of barium sulfate (Blanc fixe micro from Sachtleben Chemie GmbH), 3.7 parts by weight of butyl glycol, and 0.3 part by weight of Agitan 282 (available from Münzing Chemie GmbH), and 3 parts by weight of deionized water.

[0291] Preparation of Steatite Paste

[0292] The steatite paste is prepared from 49.7 parts by weight of an aqueous binder dispersion prepared as per WO 91/15528, page 23, line 26 to page 25, line 24, 28.9 parts by weight of steatite (Microtalc IT extra from Mondo Minerals B.V.), 0.4 part by weight of Agitan 282 (available from Münzing Chemie GmbH), 1.45 parts by weight of Disperbyk®-184 (available from BYK-Chemie GmbH), 3.1 parts by weight of a commercial polyether (Pluriol® P900, available from BASF SE) and 16.45 parts by weight of deionized water.

[0293] 1.2G Preparation of Aqueous Basecoat Materials WBM B17 (Comparative) and WBM B18 (Inventive)

[0294] The components listed under “Aqueous phase” in table G are combined with stirring in the order stated to form an aqueous mixture. In the next step, an organic mixture is prepared from the components listed under “Organic phase” in table G, and a mixing varnish is prepared from the components listed under “Mixing varnish”. The organic mixture and the mixing varnish are mixed for 10 minutes, and this mixture is then added to the aqueous mixture. The resulting mixture is then stirred for 10 minutes and adjusted using deionized water and dimethylethanolamine to a pH of 8 and to a spray viscosity of 85±5 mPa.Math.s under a shearing load of 1000 s.sup.−1, as measured using a rotary viscosimeter (Rheolab QC instrument with C-LTD80/QC heating system from Anton Paar) at 23° C.

TABLE-US-00010 TABLE G Preparation of waterborne basecoat materials WBM B17 and WBM B18 WBM WBM B17 B18 Aqueous phase: Deionized water 16.48 29.34 Butyl glycol 5.78 (vdM) 6 22.96 Disparlon ® A670-20M (direction 3.44 addition) Aqueous dispersion of a 32.26 poly(meth)acrylate emulsion polymer having a nonvolatile fraction of 26-28% Polyester; prepared as for 5.17 example D, column 16, lines 37-59 of DE 40 09 858 A1 Dimethylethanolamine in water 0.80 0.91 (10 wt %) Rheovis ® AS 1130 0.75 2,4,7,9-Tetramethyl-5-decynediol 0.69 in butyl glycol (52 wt %) Resimene ® HM 2608 4.36 Pluriol ® P900 1.15 Organic phase: Butyl glycol 6.89 6.89 Alu Stapa Hydrolux ® VP56450 5.74 5.74 Mixing varnish: Aqueous dispersion of a 1.89 1.89 poly(meth)acrylate emulsion polymer having a nonvolatile fraction of 26-28% Deionized water 1.17 1.17 2,4,7,9-Tetramethyl-5-decynediol 0.24 0.24 in butyl glycol (52 wt %) Dispex ® Ultra FA 4437 0.10 0.10 Dimethylethanolamine in water 0.01 0.01 (10 wt %) Butyl glycol 0.60 0.60

[0295] 2. Investigation of Basecoat Materials and Multicoat Paint Systems Produced Using Basecoat Materials

[0296] Comparison Between Waterborne Basecoat Material WBM B2 and Waterborne Basecoat Materials WBM B1 and Also WBM B3 to WBM B6

[0297] Investigation took place into the incidence of gel specks, the tendency toward separation, and the film thickness-dependent leveling. The results are summarized in tables 2.1 and 2.2.

TABLE-US-00011 TABLE 2.1 Results of the investigations into stability (separation) and gel specks WBM WBM WBM WBM WBM WBM B1 B2 B3 B4 B5 B6 Stability (visual 1 1 4 3 5 4 assessment of separation) Gel specks 1 1 3 4 5 4 (coating on glass panel) Gel specks 1 1 3 4 5 4 (coating on steel substrate) WBM B1 (containing phyllosilicate) and WBM B2 (for inventive use) have no gel specks and also show no tendency toward phase or other separation. The basecoat materials with polyamides having a high acid number (WBM B3 to WBM B6) surprisingly display significant weaknesses in gel specks and stability; increasing the amount of the polyamide does not produce any improvement. These polyamides are therefore much poorer for use as rheological assistants in waterborne basecoat materials. The reference used for the further investigations was therefore the system containing phyllosilicate.

TABLE-US-00012 TABLE 2.2 Results of the investigations into leveling (here: SW, LW, and DOI) Paint system 1st Waterborne basecoat as wedge WBM WBM A2 A2 Paint system 2nd Waterborne basecoat constant Appearance Film thickness range 2nd WBM WBM characteristic basecoat B1 B2 SW  5 μm-10 μm 20.2 16.3 10 μm-15 μm 19.2 17.6 15 μm-20 μm 20.6 20.3 20 μm-25 μm 21.9 21.0 25 μm-30 μm 22.6 22.6 LW  5 μm-10 μm 8.7 8.9 10 μm-15 μm 9.6 9.3 15 μm-20 μm 10.5 8.6 20 μm-25 μm 11.2 10.0 25 μm-30 μm 11.6 10.7 DOI  5 μm-10 μm 90.9 93.7 10 μm-15 μm 91.6 92.6 15 μm-20 μm 91.6 90.6 20 μm-25 μm 89.5 90.2 25 μm-30 μm 90.0 88.4

[0298] The results demonstrate that by using a basecoat material for inventive use it is possible to exert a positive influence on leveling, especially at relatively low to moderate film thicknesses.

[0299] Comparison Between Waterborne Basecoat Materials WBM B7 and WBM B9 and Also Waterborne Basecoat Materials WBM B8 and WBM B10

[0300] Investigation took place into the incidence of pinholes and the film thickness-dependent leveling. The results are summarized in tables 2.3 to 2.5.

TABLE-US-00013 TABLE 2.3 Results of the investigations into pinholes Number of pinholes (standardized to 200 cm.sup.2): Paint system 1st waterborne basecoat as wedge WBM WBM WBM WBM A2 A2 A2 A2 Film thickness range basecoat Paint system 2nd waterborne total film (waterborne basecoat constant basecoat 1 + waterborne WBM WBM WBM WBM basecoat 2) B7= B8 B9 B10 0-20 μm 0 0 0 0 20 μm-end of wedge 0 0 0 0 Total 0 0 0 0 Number of pinholes (standardized to 200 cm.sup.2): Paint system 1st Waterborne basecoat constant WBM WBM WBM WBM A2 A2 A2 A2 Film thickness range basecoat Paint system 2nd Waterborne total film (waterborne basecoat as wedge basecoat 1 + waterborne WBM WBM WBM WBM basecoat 2) B7= B8 B9 B10 0-20 μm 0 0 0 0 20 μm-end of wedge 0 0 1 0 Total 0 0 1 0

[0301] Waterborne basecoat materials WBM B7 to WBM B10 consistently show very good pinhole robustness.

TABLE-US-00014 TABLE 2.4 Results of the investigations into leveling (here: SW, LW and DOI of waterborne basecoat materials WBM B7 and WBM B8) Paint system 1st Waterborne basecoat as wedge WBM WBM A2 A2 Paint system 2nd Waterborne basecoat constant Appearance Film thickness range 2nd WBM WBM characteristic basecoat B7 B8 SW  5 μm-10 μm 22.0 16.0 10 μm-15 μm 20.3 16.2 15 μm-20 μm 20.0 17.1 20 μm-25 μm 21.9 19.2 25 μm-30 μm 22.4 20.4 LW  5 μm-10 μm 8.2 8.4 10 μm-15 μm 7.2 7.5 15 μm-20 μm 7.6 6.8 20 μm-25 μm 8.7 7.8 25 μm-30 μm 9.5 8.9 DOI  5 μm-10 μm 91.6 91.4 10 μm-15 μm 91.2 92.3 15 μm-20 μm 90.8 92.0 20 μm-25 μm 89.8 91.3 25 μm-30 μm 88.9 91.5

TABLE-US-00015 TABLE 2.5 Results of the investigations into leveling (here: LW of waterborne basecoat materials WBM B9 and WBM B10) Paint system 1st Waterborne basecoat as wedge WBM WBM A1 A1 Paint system 2nd Waterborne basecoat constant Appearance Film thickness range 2nd WBM WBM characteristic basecoat B9 B10 LW  5 μm-10 μm 9.2 7.6 10 μm-15 μm 9.6 7.4 15 μm-20 μm 9.1 7.7 20 μm-25 μm 10.2 8.1 25 μm-30 μm 11.5 8.9

[0302] The results demonstrate that by using the inventive waterborne basecoat materials WBM B8 and WBM B10 it is possible to optimize the leveling.

[0303] Comparison Between Waterborne Basecoat Materials WBM B11 and WBM B12

[0304] Investigation took place into the storage stability and the film thickness-dependent leveling. The results are summarized in tables 2.6 and 2.7.

TABLE-US-00016 TABLE 2.6 Results of the investigations into storage stability Waterborne basecoat material WBM WBM B11 B12 Low-shear Fresh after 2-week 3398.5 2456.7 viscosity storage at 40° C. 2811.2 2300 (1 s.sup.−1) change [%] −17% −6% in mPa .Math. s High-shear Fresh after 2-week 95.43 92.7 viscosity storage at 40° C. 85.59 81.97 (1000 s.sup.−1) change [%] −10% −12% in mPa .Math. s

[0305] As far as the change in the high-shear viscosity is concerned, the behavior exhibited by both basecoat materials is comparable. When a basecoat for inventive use is used that comprises a mixture (vdM) comprising a polyamide with low acid number (WBM B12), a significant advantage is evident over the reference (WBM B11) in terms of the change in low-shear viscosity.

TABLE-US-00017 TABLE 2.5 Results of the investigations into film thickness- dependent leveling (here: LW/DOI) Paint system 1st Waterborne basecoat as wedge WBM WBM A2 A2 Paint system 2nd Waterborne basecoat constant Appearance Film thickness range 2nd WBM WBM characteristic basecoat B11 B12 LW 10 μm-15 μm 13.5 12.3 15 μm-20 μm 13.0 11.8 20 μm-25 μm 12.9 11.3 25 μm-30 μm 13.1 12.4 DOI 10 μm-15 μm 77.7 80.7 15 μm-20 μm 74.3 79.7 20 μm-25 μm 71.3 77.0 25 μm-30 μm 71.7 73.0

[0306] The results emphasize that when using a polyamide of the invention with a low acid number it is possible in all film thickness ranges to achieve better leveling (determined in this case were only LW and DOI).

[0307] Comparison Between Waterborne Basecoat Materials WBM B13 and WBM B14

[0308] Investigation took place into the film thickness-dependent leveling. The results are summarized in table 2.8.

TABLE-US-00018 TABLE 2.8 Results of the investigations into film thickness- dependent leveling (here: SW/LW/DOI) Paint system 1.sup.st Waterborne basecoat as wedge WBM WBM A2 A2 Paint system 2nd Waterborne basecoat constant Appearance Film thickness range 2.sup.nd WBM WBM characteristic basecoat B13 B14 SW 10 μm-15 μm 31.1 22.2 15 μm-20 μm 32.8 25.1 20 μm-25 μm 34.0 28.5 25 μm-30 μm 35.6 30.5 LW 10 μm-15 μm 11.1 10.0 15 μm-20 μm 11.5 10.2 20 μm-25 μm 12.6 9.6 25 μm-30 μm 15.1 10.3 DOI 10 μm-15 μm 70.6 82.4 15 μm-20 μm 68.3 79.0 20 μm-25 μm 63.7 76.2 25 μm-30 μm 60.3 73.4

[0309] The use of a basecoat for inventive use, comprising a predispersed mixture comprising a polyamide with low acid number (WBM B14), in comparison to the phyllosilicate-containing reference (WBM B13), leads to a significant improvement in the leveling, particularly the short wave, and also the DOI.

[0310] Comparison Between Waterborne Basecoat Materials WBM B15 and WBM B16

[0311] Investigation took place into the pinhole robustness and the film thickness-dependent leveling. The results are summarized in tables 2.9 to 2.11.

TABLE-US-00019 TABLE 2.9 Results of the investigations into pinholes Number of pinholes (standardized to 200 cm.sup.2): Paint system 1st waterborne basecoat as wedge WBM WBM A1 A1 Film thickness range basecoat Paint system 2nd waterborne total film (waterborne basecoat constant basecoat 1 + waterborne WBM WBM basecoat 2) 15 16 0-20 μm 10 1 20 μm-end of wedge 24 1 Total 34 2 Number of pinholes (standardized to 200 cm.sup.2): Paint system 1st waterborne basecoat constant WBM WBM A1 A1 Film thickness range basecoat Paint system 2nd waterborne total film (waterborne basecoat as wedge basecoat 1 + waterborne WBM WBM basecoat 2) 15 16 0-20 μm 63 0 20 μm-end of wedge 21 0 Total 84 0

[0312] The waterborne basecoat material WBM B16 for inventive use has a significantly better pinhole robustness than the phyllosilicate-based waterborne basecoat material WBM B15.

TABLE-US-00020 TABLE 2.10 Results of the investigations into pinholes Number of pinholes (standardized to 200 cm.sup.2): Paint system 1st waterborne basecoat as wedge WBM WBM A2 A2 Film thickness range basecoat Paint system 2nd waterborne total film (waterborne basecoat constant basecoat 1 + waterborne WBM WBM basecoat 2) 15 16 0-20 μm 7 0 20 μm-end of wedge 2 0 Total 9 0 Number of pinholes (standardized to 200 cm.sup.2): Paint system 1st waterborne basecoat constant WBM WBM A2 A2 Film thickness range basecoat Paint system 2nd waterborne total film (waterborne basecoat as wedge basecoat 1 + waterborne WBM WBM basecoat 2) 15 16 0-20 μm 7 0 20 μm-end of wedge 0 0 Total 7 0

[0313] When using WBM A2 as first waterborne basecoat material, a significantly lower pinhole level is found for the phyllosilicate-containing reference (WBM B15); slight advantages are nevertheless still apparent when using the basecoat material for inventive use WBM B16.

TABLE-US-00021 TABLE 2.11 Results of the investigations into leveling (here: SW, LW and DOI) Paint system 1.sup.st Waterborne basecoat as wedge WBM WBM A1 A1 Paint system 2nd Waterborne basecoat constant Appearance Film thickness range 2.sup.nd WBM WBM characteristic basecoat B15 B16 SW 10 μm-20 μm 23.4 23.8 20 μm-30 μm 27.5 26.4 30 μm-40 μm 34.6 28.6 LW 10 μm-20 μm 5.5 4.9 20 μm-30 μm 6.6 5.6 30 μm-40 μm 8.2 6.2 DOI 10 μm-20 μm 87.3 88.0 20 μm-30 μm 82.5 86.2 30 μm-40 μm 74.8 85.7

[0314] The results emphasize that advantages are achieved for the systems of the invention in terms of leveling as well, particularly over high film thicknesses.

[0315] Comparison Between Waterborne Basecoat Materials WBM B17 and WBM B18

[0316] Investigation took place into the incidence of gel specks and the storage stability. The results are summarized in tables 2.12 and 2.13.

TABLE-US-00022 TABLE 2.12 Results of the investigations into gel specks WBM WBM B17 B18 Gel specks 1 5 (coating on glass panel) Gel specks 1 5 (coating on steel substrate)

TABLE-US-00023 TABLE 2.13 Results of the investigations into storage stability Waterborne basecoat material WBM WBM B17 B18 Low-shear Fresh after 2-week 3053 n.m. viscosity storage at 40° C. 3177 n.m. (1 s.sup.−1) change [%] 4% n.m. in mPa .Math. s High-shear Fresh after 2-week 79 n.m. viscosity storage at 40° C. 85 n.m. (1000 s.sup.−1) change [%] 6% n.m. in mPa .Math. s

[0317] The results show that the basecoat material for inventive use WBM B17 has excellent quality in the area of storage stability and formation of gel specks. In particular it is apparent that the use of a basecoat material WBM B18, which contains the same polyamide with low acid number as WBM B17, but in which the polyamide has been introduced directly and not in the form of the predispersed mixture (vdM), gives much poorer properties.

[0318] All in all, results show that the use of a polyamide of low acid number in waterborne basecoat materials leads, surprisingly, to much better properties than does the use of polyamides of higher acid number which are actually intended for aqueous coating systems. These advantages, however, are obtained only when the polyamide of low acid number is introduced in the form of predispersed mixture (vdM) into the aqueous basecoat material.

BRIEF DESCRIPTION OF THE FIGURES

[0319] FIG. 1:

[0320] Schematic construction of a multicoat paint system of the invention (M), disposed on a metallic substrate (S), and comprising a cured electrocoat (E.1) and also a basecoat (B.2.1) and a clearcoat (K) which have been jointly cured.

[0321] FIG. 2:

[0322] Schematic construction of a multicoat paint system of the invention (M), disposed on a metallic substrate (S), and comprising a cured electrocoat (E.1), two basecoats (B.2.2.x), namely a first basecoat (B.2.2.a) and a topmost basecoat (B.2.2.z) arranged over it, and also a clearcoat (K), which have been jointly cured.

[0323] FIG. 3:

[0324] Schematic construction of a multicoat paint system of the invention (M), disposed on a metallic substrate (S), and comprising a cured electrocoat (E.1), three basecoats (B.2.2.x), namely a first basecoat (B.2.2.a), a basecoat (B.2.2.b), and a topmost basecoat (B.2.2.z), arranged over it, and also a clearcoat (K), which have been jointly cured.