AQUEOUS DISPERSIONS CONTAINING POLYMERIZATES PRODUCED IN MULTIPLE STAGES AND COATING AGENT COMPOSITIONS CONTAINING SAME

Abstract

Described herein are aqueous dispersions including multistage-prepared polymers of olefinically unsaturated compounds and to the preparation and use thereof, in particular in the field of automobile coating.

Claims

1. An aqueous dispersion comprising at least one polymer, preparable by: i. polymerizing a mixture of olefinically unsaturated monomers A by emulsion polymerization in water, using at least one emulsifier and at least one water-soluble initiator, wherein a polymer prepared from the monomers A has a glass transition temperature of 10 to 55 C., ii. polymerizing a mixture of olefinically unsaturated monomers B by emulsion polymerization in water, using at least one emulsifier and at least one water-soluble initiator, in the presence of the polymer obtained under i., wherein a monomers concentration of 6.0 wt % in the reaction solution is not exceeded throughout the reaction period, and the mixture of olefinically unsaturated monomers B comprises at least one polyolefinically unsaturated monomer, iii. polymerizing a mixture of olefinically unsaturated monomers C by emulsion polymerization in water, using at least one emulsifier and at least one water-soluble initiator, in the presence of the polymer obtained under ii., wherein a monomers concentration of 6.0 wt % in the reaction solution is not exceeded throughout the reaction period, and iv. adjusting the pH of the reaction solution to a pH of 6.5 to 9.0, wherein a. the mixture of olefinically unsaturated monomers A comprises from 0 wt % to less than 50.0 wt % of one or more monomers having a solubility in water of <0.5 g/l at 25 C., a monomers A concentration of 6.0 wt % in the reaction solution from stage i. is not exceeded, and the resulting polymer after stage i. has a particle size of 20 to 110 nm, b. a polymer prepared from the monomers B has a glass transition temperature of 35 to 12 C., and the resulting polymer after stage ii. has a particle size of 130 to 200 nm, c. a polymer prepared from the monomers C has a glass transition temperature of 50 to 15 C., and the resulting polymer after stage iii. has a particle size of 150 to 280 nm.

2. The aqueous dispersion of claim 1, wherein the mass of the monomer mixture A, based on the total mass of the monomer mixtures A, B and C, is 1 to 10%, the mass of the monomer mixture B, based on the total mass of the monomer mixtures A, B and C, is 60 to 80%, and the mass of the monomer mixture C, based on the total mass of the monomer mixtures A, B and C, is 10 to 30%.

3. The aqueous dispersion of claim 1, wherein the emulsifiers used under i., ii., and iii. are selected, independently of one another, from the group consisting of ethoxylated and propoxylated alkanols having 10 to 40 carbon atoms.

4. The aqueous dispersion of claim 1, wherein the monomer mixture A comprises at least one monounsaturated ester of (meth)acrylic acid having an unsubstituted alkyl radical and/or at least one vinylically monounsaturated monomer having an aromatic radical on the vinyl group.

5. The aqueous dispersion of claim 1, wherein the monomer mixture B comprises at least one polyolefinically unsaturated monomer and at least one monounsaturated ester of (meth)acrylic acid having an unsubstituted alkyl radical.

6. The aqueous dispersion of claim 1, wherein the monomer mixture C comprises at least one alpha-beta unsaturated carboxylic acid, at least one monounsaturated ester of (meth)acrylic acid having an alkyl radical substituted by one or more hydroxyl groups and at least one monounsaturated ester of (meth)acrylic acid having an unsubstituted alkyl radical.

7. A pigmented aqueous basecoat material which comprises at least one aqueous dispersion of claim 1.

8. The pigmented aqueous basecoat material of claim 7, wherein the weight percentage fraction, based on the total weight of the pigmented aqueous basecoat material, of the at least one polymer comprised in the aqueous dispersion of any of claims 1 to 6 is 1.0 to 24.0 wt %.

9. The pigmented aqueous basecoat material of claim 7, which comprises as a binder at least one polyurethane resin.

10. The pigmented aqueous basecoat material of claim 7, which comprises a polyurethane resin, said resin being grafted by means of olefinically unsaturated monomers and also containing hydroxyl groups, and also a melamine resin.

11. A method of using an aqueous dispersion of claim 1, said method comprising using the aqueous dispersion in pigmented aqueous basecoat materials for improving adhesion.

12. A process for producing a multicoat paint system, in which (1) a pigmented aqueous basecoat material is applied to a substrate, (2) a polymer film is formed from the coating material applied in stage (1), (3) a clearcoat material is applied to the resulting basecoat film, and subsequently (4) the basecoat film is cured together with the clearcoat film, wherein a pigmented aqueous basecoat material of claim 7 is used in stage (1).

13. The process of claim 12, wherein the substrate from stage (1) is a multicoat paint system which possesses defect sites.

14. A multicoat paint system producible by the process of claim 12.

15. The process of claim 13, wherein the multicoat paint system employed as substrate and exhibiting defect sites is a system of claim 14.

Description

INVENTIVE AND COMPARATIVE EXAMPLES

[0250] Unless otherwise indicated, the amounts in parts are parts by weight and amounts in percent are in each case percentages by weight.

1. Components Employed

[0251] The definitions of the components identified below and used in preparing the dispersions of the invention and also the waterborne basecoat materials of the invention comprising the dispersions of the invention as binders, and the corresponding comparative examples, are as follows:

[0252] Aerosol EF-800 is a commercially available emulsifier from Cytec.

[0253] APS is used as an abbreviation of the chemical compound ammonium peroxodisulfate.

[0254] 1,6-HDDA is used as an abbreviation of the chemical compound. 1,6-nexanediol diacrylate.

[0255] VEOVA10 is a commercially available monomer from Momentive. The monomer is the vinyl ester of VersaticAcid 10.

[0256] 2-HEA is used as as abbreviation of the chemical compound 2-hydroxyethyl acrylate.

[0257] MMA is used as as abbreviation of the chemical compound methyl methacrylate.

[0258] Sipomer PAM 200 is a commercially available phosphate ester of polypropylene glycol moan ethyl acrylate from Solvay.

[0259] DMEA is used as an abbreviation of the chemical compound dimethylethanolamine.

[0260] Rhodapex CO 436 is a commercially available emulsifier from Solvay, Rhodia.

[0261] Cymel 303 is a commercially available melamine-formaldehyde resin from Allnex.

[0262] Rheovis AS 1130 is a commercially available rheology additive for aqueous coating materials, from BASF SE.

[0263] Pluriol E300 is a commercially available polyethylene glycol from BASE SE.

2. Examples of Syntheses of the Aqueous Dispersions Comprising at Least One Multistage Polymer

2.1 Preparation of Aqueous Dispersions BM1, BM2, and BM3, Comprising a Seed-Core-Shell Acrylate SCS1, SCS2, and SCS3 (Inventive)

[0264] 80 wt % of items 1 and 2 in table 2.1 are placed into a steel reactor (5 11, volume) with reflux condenser, and heated to 80 C., The remaining fractions of the components listed under initial charge in table 2.1 are premixed in a separate vessel. This mixture and the initiator solution are added dropwise to the reactor over 20 minutes, where a monomers concentration of 6.0 wt % in the reaction solution is not exceeded throughout the reaction period. This is followed by stirring for 30 minutes. (Corresponds to stage i).)

[0265] The components indicated under mono 1 in table 2.1 are premixed in a separate vessel. This mixture is added dropwise to the reactor over 2 hours, where a monomers concentration or 6.0 wt % in the reaction solution is not exceeded throughout the reaction period. This is followed by 1 hour of stirring. (Corresponds to stage ii).)

[0266] The components indicated under mono 2 in table 2.1 are premixed in a separate vessel. This mixture is added dropwise to the reactor over 1 hour, where a monomers concentration or in the reaction period. This followed by 2 hours or stirring. (Corresponds to stage iii).)

[0267] The reaction mixture is thereafter cooled to 60 C. and the neutralizing mixture is premixed in a separate vessel. The neutralizing mixture is added dropwise to the reactor over 40 minutes, wherein the pH of the reaction solution is adjusted to a pH of 6.5 to 9.0. The reaction product is subsequently stirred for 30 minutes more, cooled to 25 C. and filtered. (Corresponds to stage iv).)

TABLE-US-00001 TABLE 2.1 Aqueous dispersions BM1 to BM3 comprising seed-core-shell acrylates SCS1 to SCS3 (according to the invention) BM1 BM2 BM3 Initial charge 1 DI water 43.54 43.54 41.81 2 EF 800 0.18 0.19 0.18 3 Styrene 0.5 0.5 0.48 4 n-Butyl acrylate 0.68 5 Ethyl acrylate 0.55 0.55 Initiator solution 6 DI water 0.55 0.53 0.53 7 APS 0.02 0.02 0.02 Mono 1 8 DI water 13.31 13.31 12.78 9 EF 800 0.15 0.15 0.15 10 APS 0.02 0.02 0.02 11 Styrene 5.84 5.84 5.61 12 n-Butyl acrylate 13.6 13 Ethyl acrylate 11.05 9.47 14 1,6-HDDA 0.35 0.35 0.34 15 VEOVA10 1.58 Mono 2 16 DI water 5.97 5.97 5.73 17 EF 800 0.07 0.07 0.07 18 APS 0.02 0.02 0.02 19 Methacrylic acid 0.74 0.74 0.71 20 2-HEA 0.31 0.99 0.85 21 n-Butyl acrylate 1.87 22 Ethyl acrylate 3.04 3.04 23 MMA 0.6 0.58 24 Sipomer PAM 0.68 25 VEOVA10 1.87 Neutralizing 26 DI water 6.75 6.75 6.48 27 Butyl glycol 4.96 4.96 4.76 28 DMEA 0.79 0.79 0.76 pH 7.2 8.5 8.2

[0268] The solids content was determined for the purpose of reaction monitoring. The results are reported in table 2.2:

TABLE-US-00002 TABLE 2.2 Solids content of the aqueous dispersions BM1 to BM3 BM1 BM2 BM3 Solids content 23.7 21.5 25.4

[0269] After each stage i) to iv), the particle size of the polymers was determined by means of dynamic light scattering in accordance with DIN ISO 13321. The results are reproduced in table 2.3.

TABLE-US-00003 TABLE 2.3 Particle sizes in nm of the seed-core-shell acrylates SCS1 to SCS3 after each stage i) to iv) SCS1 SCS2 SCS3 i After initial charge 60 70 70 ii After Mono 1 140 130 153 iii After Mono 2 210 212 194 iv After neutralizing 236 225 236

[0270] Each of the stated monomer mixtures was polymerized individually and thereafter the glass transition temperature was determined by means of DSC in accordance with DIN standard 53765. Also determined was the glass transition temperature for the overall polymer, after neutralization, by means of DSC in accordance with DIN standard 53765.

[0271] The results are reported in table 2.4.

TABLE-US-00004 TABLE 2.4 Glass transition temperatures in C. of individual stages of the seed-core-shell acrylates SCS1 to SCS3 SCS1 SCS2 SCS3 i Initial charge 33 36 32 ii Mono 1 12 15 11 iii Mono 2 9 1 5 Overall polymer 8 10 11
2.2 Preparation of an Aqueous Dispersion BM5 Comprising a Three-Stage Acrylate SCS5 (as per Korea Polym. J., vol. 7, no. 4, pp. 213-222; not Inventive)

[0272] Components 1 to 4 from table 2.5 are placed into a steel reactor (5 L volume) with reflux condenser, and heated to 80 C. The initiator solution (table 2.5, items 5 and 6) is added dropwise to the reactor over 5 minutes. This is followed by stirring for 30 minutes.

[0273] The components indicated under mono 1 in table 2.5 are premixed in a separate vessel. This mixture is added dropwise to the reactor over 2 hours. This is followed by 1 hour of stirring.

[0274] The components indicated under mono 2 in table 2.5 are premixed in a separate vessel. This mixture is added dropwise to the reactor over 1 hour. This is followed by 1 hour of stirring.

[0275] The reaction mixture is thereafter cooled to 60 C. and the neutralizing mixture (table 2.5, items 20 to 22) is premixed in a separate vessel. The neutralizing mixture is added dropwise to the reactor over 40 minutes. The reaction product is subsequently stirred for 30 minutes more and cooled to 25 C.

TABLE-US-00005 TABLE 2.5 Multistage acrylate BM5 BM5 Initial charge 1 DI water 43.54 2 Rhodapex CO 436 0.16 3 Styrene 0.5 4 Ethyl acrylate 0.55 Initiator solution 5 DI water 0.55 6 APS 0.02 Mono 1 7 DI water 13.31 8 Rhodapex CO 436 0.13 9 APS 0.02 10 Styrene 5.84 11 Ethyl acrylate 11.05 12 1,6-HDDA 0.35 Mono 2 13 DI water 5.97 14 Rhodapex CO 436 0.06 15 APS 0.02 16 Methacrylic acid 0.74 17 2-HEA 0.99 18 Ethyl acrylate 3.04 19 MMA 0.6 Neutralizing 20 DI water 6.75 21 Butyl glycol 4.96 22 DMEA 0.79 pH 8.1

[0276] The solids content was 23.4%.

[0277] After each stage i) to iv), the particle size of the polymer was determined by means of dynamic light scattering in accordance with DIN ISO 13321. The results are reproduced in table 2.6.

TABLE-US-00006 TABLE 2.6 Particle sizes in nm of the acrylate SCS5 after each stage i) to iv) SCS5 i After initial charge 110 ii After Mono 1 196 iii After Mono 2 223 iv After neutralizing 310

[0278] Each of the stated monomer mixtures was polymerized individually and thereafter the glass transition temperature was determined by means of DSC in accordance with DIN standard 53765. Also determined was the glass transition temperature for the overall polymer, after neutralization, by means of DSC in accordance with DIN standard 53765.

[0279] The results are reported in table 2.7.

TABLE-US-00007 TABLE 2.7 Glass transition temperatures in C. of the individual stages of the multistage acrylate SCS5 SCS5 i Initial charge 32 ii Mono 1 26 iii Mono 2 35 Overall polymer 26

3. Examples of Paint Formulations

[0280] 3.1 Preparation of the Noninventive Waterborne Basecoat Materials A1 and A2 Based on the Aqueous Dispersion BM5 (as per Korea Polym. J., vol. 7, no. 4, pp. 213-222)

[0281] The components listed under aqueous phase in table 3.1 are stirred together 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. The organic mixture is added to the aqueous mixture. This is followed by stirring for 10 minutes, and then a pH of 8 and a spray viscosity of 90-95 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. are set using deionized water and dimethylethanolamine.

TABLE-US-00008 TABLE 3.1 Waterborne basecoat materials A1 and A2 (not inventive) A1 A2 Aqueous phase 3% strength NaMg phyllosilicate 10.00 solution Aqueous dispersion BM5 (as per 28.40 28.40 Korea. Polym. J., vol. 7, no. 4, pp. 213-222) Deionized water 30.30 39.30 Polyester prepared as per 2.70 2.70 example D, column 16, lines 37-59 of DE 40 09 858 A1 n-Butoxypropanol 3.20 3.20 Melamine-formaldehyde resin 3.20 3.20 (Cymel 303 from Allnex) 10% strength 2.30 2.30 dimethylethanolamine in water Polyurethane-modified 3.60 3.60 polyacrylate, prepared as per page 7, line 55 to page 8, line 23 of DE 4437535 A1 Rheovis AS 1130 (available from 1.50 2.50 BASF SE) Organic phase Butyl glycol 7.00 7.00 Pluriol E300 from BASF SE 2.80 2.80 Aluminum pigment available from 5.00 5.00 Altana-Eckart (Alu Stapa Hydrolux 8154)

3.2 Preparation of the Inventive Waterborne Basecoat Materials A3 and A4 Based on the Aqueous Dispersion BM1

[0282] The components listed under aqueous phase is table 3.2 are stirred together 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. The organic mixture is added to the aqueous mixture. This is followed by stirring for 10 minutes, and a pH of 8 and a spray viscosity of 1005 mPa.Math.s (A3) or 1405 mPa.Math.s (AA) under a shearing load of 1000 s.sup.1, measured using a rotary viscometer (Rheolab QC instrument with C-LTD80/QC heating system, from Anton Paar) at 23 C., are set using deionized water and dimethylethanolamine.

TABLE-US-00009 TABLE 3.2 Inventive aqueous basecoat materials A3 and A4 A3 A4 Aqueous phase 3% strength NaMg 10.00 phyllosilicate solution Aqueous dispersion BM1 30.05 30.05 Deionized water 29.15 20.35 Polyester prepared as per 2.70 2.70 example D, column 16, lines 37-59 of DE 40 09 858 A1 n-Butoxypropanol 3.20 3.20 Melamine-formaldehyde resin 3.20 3.20 (Cymel 303 from Allnex) Deionized water 10.00 10.00 Polyurethane-modified 3.60 3.60 polyacrylate; prepared as per page 7, line 55 to page 8, line 23 of DE 4437535 A1 Rheovis AS 1130 (available 1.50 1.30 from BASF SE) 10% strength dimethyl- 1.80 0.80 ethanolamine in water Organic phase Butyl glycol 7.00 7.00 Pluriol E300 from BASF SE 2.80 2.80 Aluminum pigment available 5.00 5.00 from Altana-Eckart (Alu Stapa Hydrolux 8154)

3.3 Preparation of the Inventive Waterborne Basecoat Materials A6 and A7 Based on the Inventive Aqueous Dispersions BM2 and BM3

[0283] The components listed under aqueous phase in table 3.3 are stirred together 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. The organic mixture is added to the aqueous mixture. This is followed by stirring for 10 minutes, and then a pH of 8 and a spray viscosity of 1205 mPa.Math.s (A6 and A7) under a shearing load of 1000 s.sup.1, as measured using a rotary viscometer (Rheolab QC instrument with C-2TD80/QC heating system, from. Anton Pant) at 23 C. are set using deionized water and dimethylethanolamine.

TABLE-US-00010 TABLE 3.3 Inventive waterborne basecoat materials A6 and A7 A6 A7 Aqueous phase 3% strength NaMg 10.00 10.00 phyllosilicate solution Aqueous dispersion BM2 30.45 Aqueous dispersion BM3 26.15 Deionized water 19.50 23.80 Polyester prepared as per 2.70 2.70 example D, column 16, lines 37-59 of DE 40 09 858 A1 n-Butoxypropanol 3.20 3.20 Melamine-formaldehyde resin 3.20 3.20 (Cymel 303 from Allnex) Deionized water 10.00 10.00 Polyurethane-modified 3.60 3.60 polyacrylate; prepared as per page 7, line 55 to page 8, line 23 of DE 4437535 A1 Rheovis AS 1130 (available 1.75 1.75 from BASF SE) 10% strength dimethyl- 0.80 0.80 ethanolamine in water Organic phase Butyl glycol 7.00 7.00 Pluriol E300 from BASF SE 2.80 2.80 Aluminum pigment available 5.00 5.00 from Altana-Eckart (Alu Stapa Hydrolux 8154)

Results

4.1 Descriptions of Methods

4.1.1 Determination of Lightness and Flop Index

[0284] For determining the lightness or the flop index, an inventive coating composition (or a comparative coating composition) is applied by means of dual application as waterborne basecoat material to a steel panel coated with a primer-surfacer coating and having dimensions of 360 cm, where, in the first step, application takes place electrostatically with a dry film thickness of 8-9 m, and in the second step, application takes place after a 2-minute flashing time at room temperature (18 to 23 C.), pneumatically with a dry film thickness of 4-5 m. The resulting waterborne basecoat film is subsequently dried, after a further flashing time of 5 minutes at room temperature, in a forced air oven at 80 C. for 5 minutes. Applied over the dried waterborne basecoat film is a commercial two-component clearcoat material (ProGloss from BASF Coatings GmbH), with a dry film thickness of 40-45 m. The resulting clearcoat film is flashed at room temperature (18 to 23 C.) for a period of 10 minutes, followed by curing in a forced air oven at 140 C. for 20 minutes more. The substrate coated accordingly is subjected to measurement using an X-Rite spectrophotometer (X-Rite MA68 multi-angle spectrophotometer). In this case, the surface is illuminated using a light source. Spectral detection in the visible range is carried out from different angles. From the resulting spectral measurements it is possible, with incorporation of the standard spectral values and also of the reflection spectrum of the light source used, to calculate color values in the CIEL*a*b* color space, where L* characterizes the lightness, a* the red-green value, and b* the yellow-blue value. This method is described in ASTM E2194-12, for example, particularly for coatings comprising at least one effect pigment as pigment. The derived value which is often employed to quantify the metallic effect is the so-called flop index, which describes the relationship between lightness and observation angle (cf. A. B. J. Rodriguez, JOCCA, 1992 (4), pp. 150-153). The flop index (FL) can be calculated from the lightness values found for the viewing angles of 15, 45, and 110, in accordance with the formula

FL=2.69(L*.sub.15L*.sub.110).sup.1.11/(L*.sub.45).sup.0.86

where L* is the lightness value measured at the respective measurement angle (1545, and 110).

4.1.2 Assessment of Appearance Before and After Condensation Exposure

[0285] The leveling or waviness of the coated substrates is assessed using a Wave scan instrument from Byk/Gardner. The coated substrates are produced by dual application as described in section 4.1.1 (Determining the lightness and the flop index).

[0286] For this purpose, a laser beam is directed at an angle of 60 onto the surface under investigation, and the instrument records the fluctuations in the reflected light over a distance of 10 cm in the shortwave region (0.3 to 1.2 mm) and in the longwave region (1.2 to 12 mm) (longwave=LW; shortwave=SW; the lower the values, the better the appearance). Furthermore, as a measure of the sharpness of an image reflected in the surface of the multilayer system, the instrument determines the parameter of distinctness of image (DOI) (the higher the value, the better the appearance).

[0287] These measurements are carried out before and after condensation exposure. For this purpose, the coated substrates are stored over a period of 10 days is a climate chamber under CH test conditions according to DIN EN ISO 6270-2:2005-09 (date: September 2005). The coated substrates are subsequently inspected for swelling and blistering, 24 hours after removal from the climate chamber and the profile and waviness are assessed.

[0288] The incidence of blisters is in this case assessed as follows by a combination of two values: [0289] The number of blisters is evaluated by a quantity figure from 1 to 5, with ml denoting very few and m5 very many blisters. [0290] The size of the blisters is evaluated by a size report, likewise from 1 to 5, with g1 denoting very small and g5 very large blisters.

[0291] The designation m0g0, accordingly, denotes a blister-free finish after condensation water storage, and represents satisfactory result in terms of blistering.

4.1.3 Determination of the Adhesion Properties

[0292] For determining the adhesion properties of the inventive coating compositions (or of comparative compositions), multicoat paint systems are produced in accordance with the following general protocol:

Original Finish

[0293] Atop a metallic substrate coated with a cured electrocoat system (CathoGuard 500 from BASF Coatings GmbH) with dimensions of 1020 cm, the waterborne basecoat material is applied by means of dual appication; in the first step, application takes place electrostatically with a target film thickness of 8-9 m, and is the second step, after a 2-minute flashing time at room temperature, pneumatically with a target film thickness of 4-5 m. The resulting waterborne basecoat film is subsequently dried, after a further flashing time of 5 minutes at room temperature, in a forced air oven at 80 C. for 5 minutes. Applied over 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 m. The resulting clearcoat film is flashed at room temperature for 10 minutes, followed by curing in a forced air oven at 140 C. for 20 minutes more. The system obtainable in this way is referred to below as original finish (system a).

[0294] Alternatively, curing of the basecoat and clearcoat films is carried out at 60 minutes/140 C. (referred to hereinafter as overbaked original finish; system c).

Refinishes

[0295] Over the original finish or alternatively over the overbaked original finishes, the waterborne basecoat material is again applied by dual application, with application in the first step taking place electrostatically (target film thickness of 8-9 m) and in the second step, after a 2-minute flashing time at room temperature, pneumatically (target film thickness of 4-5 m). The resulting waterborne basecoat film, after a further 5-minute flashing time at room temperature, is subsequently dried in a forced air oven at 80 C. for 10 minutes. Over this dried waterborne basecoat film, a commercial two-component clearcoat material (ProGloss from BASF Coatings GmbH) is applied, with a target film thickness of 40-45 m.

[0296] The resulting clearcoat film is flashed at room temperature for 10 minutes; this is followed by curing in a forced air oven at 140 C. for 20 minutes more. The system obtainable accordingly is referred to below as refinish; depending on drying conditions of the original two different multicoat systems result: system A is a refinish on system a; system C is a refinish on system c.

[0297] The technological properties of the multicoat systems were assessed by implementing cross-cuts according to DIN EN ISO 2409 (rating GT 0 to GT 5; 0 best score; 5=worst score). The corresponding investigations were performed on unexposed samples and also following expo sure to condensation water. The condensation exposure, including subsequent assessment of the exposed samples for swelling and blistering, takes place as described in section 4.1.2 (Assessment of appearance before and after condensation exposure).

4.1.4 Determining the Initial Viscosity

[0298] The initial viscosity is determined after the basecoat material components have been weighed out in accordance with the preparation protocols described below, but before the adjustment of the materials in question to a pH of 8 using dimethanolamine and also to a specified spray viscosity, by measuring the viscosity under a shear load of 1000 s.sup.1 with a rotational viscometer (Rheolab QC instrument with C-LTD80/QC temperature control system from Anton Paar) at 23 C.

4.1.6 Determining the Solids Content

[0299] The solids content of the basecoat materials is determined according to DIN EN ISO 3251, table A.1 (date: Jun. 1, 2008). Here, 1 g of sample are weighed out into an aluminum dish which has been dried before-hand, and the sample is dried in a drying cabinet at 130 C. for 60 minutes, cooled in a desiccator, and then weighed again. The residue, based on the total amount of the sample used, corresponds to the solids content.

4.2 Comparison Between the Inventive Waterborne Basecoat Material A3 and the Noninventive Waterborne Basecoat Material A2 in Terms of Shade and Adhesion

[0300] Investigations on the waterborne basecoat materials A2 and also A3 take place in accordance with the methods described above. Tables 4.1 and 4.2 summarize the results.

4.2.1 Comparison Between the Inventive Waterborne Basecoat Material A3 and the Noninventive Waterborne Basecoat Material A2 in Terms of Shade

[0301]

TABLE-US-00011 TABLE 4.1 Results in terms of shade A2 A3 L*.sub.15 118.2 124.3 L*.sub.25 99.0 103.0 L*.sub.45 66.1 66.6 L*.sub.75 44.2 42.8 L*.sub.110 36.8 35.4 Flop index 9.7 10.6

[0302] Using the inventive aqueous dispersion BM1 comprising the seed-core-shell acrylate SCS1 in the waterborne basecoat material A3 leads, in comparison to the reference, the noninventive dispersion EM5 comprising the multistage acrylate SCS5 in the waterborne basecoat material A2, to an increase in the flop index, in other words to an improvement in the aluminum flake orientation.

4.2.2 Comparison Between the Inventive Waterborne Basecoat Material A3 and the Noninventive Waterborne Basecoat Material A2 in Terms of Adhesion Before and After Condensation Exposure

[0303]

TABLE-US-00012 TABLE 4.2 Results for adhesion before and after condensation exposure Clearcoat baking conditions in original system A2 A3 Adhesion of original finish before/after condensation exposure System a before condensation GT0 GT0 exposure System a after condensation GT0 GT0 exposure Refinish adhesion before condensation exposure A: standard (140 C./20 minutes) GT0 GT0 C: overbaked GT3 GT0 (140 C./60 minutes) Refinish adhesion after condensation exposure A: standard (140 C./20 minutes) GT0 GT0 C: overbaked GT1 GT0 (140 C./60 minutes)

[0304] The inventive waterborne basecoat material A3 based on the aqueous dispersion BM1 comprising the seed-core-shell acrylate SCS1 exhibits no adhesion problems in any of the multicoat systems. Conversely, the noninventive waterborne basecoat material A2 based on the noninventive aqueous dispersion BMS comprising the multistage acrylate SCS5 exhibits poorer adhesion, especially before condensation exposure, when the clearcoat of the original finish is overbaked at 140 C. for 60 minutes (system C) (plane of separation: refinish system on orginal system).

4.3 Comparison of Inventive Waterborne Basecoat Materials A4, A6 and A7 with Noninventive Waterborne Basecoat Material A1

[0305] 4.3.1 Comparison of Inventive Waterborne Basecoat Materials A4, A6 and A7 with Noninventive Waterborne Basecoat Material Al in Terms of Shade

TABLE-US-00013 A1 A4 A6 A7 L*.sub.15 125.5 134.7 127.1 128.6 L*.sub.25 102.27 105.1 103.8 104.2 L*.sub.45 64.0 60.6 64.5 63.8 L*.sub.75 41.1 38.1 40.8 40.3 L*.sub.110 34.2 32.5 34.0 33.9 Flop index 11.3 13.4 11.5 11.8

[0306] Using the inventive aqueous dispersions BM1, EM2, and BM3 in the inventive waterborne basecoat materials A4, A6, and A7 leads in all cases to improvement, in some cases significant, in the flop index in comparison to the noninventive waterborne basecoat material A1 containing the noninventive aqueous dispersion BM5.

4.3.2 Comparison of Inventive Waterborne Basecoat Materials A4, A6 and A7 with Noninventive Waterborne Basecoat Material A1in Terms of Appearance After Condensation Exposure

TABLE-US-00014 After condensation exposure A1 A4 A6 A7 LW: 2.3 2.8 1.8 2.6 SW: 18.5 9.3 9.9 13.9 DOI: 82.2 85.5 87.3 85.1 Swelling: cOK OK OK OK Blistering m1/g1 m0/g0 m0/g0 m0/g0 OK = satisfactory cOK = conditionally satisfactory m = number of blisters g = size of blisters

[0307] In terms of swelling and blistering after condensation exposure, the noninventive waterborne basecoat material A1 containing the noninventive dispersion BM5 exhibits weaknesses, whereas the waterborne basecoat materials comprising the aqueous dispersions of the invention are all classified as satisfactory.

[0308] Relative to the reference (waterborne basecoat material A1 based on BM5), the waterborne basecoat materials A4, A6 and A7 based on BM1, BM2 and BM3 exhibit advantages in terms of shortwave (SW) and also DOI after condensation exposure.