The present invention relates an aqueous dispersion (AD1) comprising water (A) and metal bisphosphonate particles (B) containing at least one metal selected from the group consisting of Ti, Zr and Hf, wherein (AD1) is obtainable by a process comprising at least steps (1 ) and (2), a freeze dried powder obtainable by submitting (AD1) to a freeze drying step, an aqueous dispersion (AD2) obtainable by adding at least water to the freeze dried inventive powder, a use of (AD1), the freeze dried powder or of (AD2) for producing a coating material composition, an aqueous coating material composition comprising at least one of (AD1), freeze dried powder, and (AD2), as well as at least one platelet-shaped pigment (EP), which generates a viewing-angle-dependent lightness effect, and at least one polymer (P) as binder, a substrate coated with such a coating material composition, and a method for producing a multicoat paint system onto a substrate involving application of said coating material composition as basecoat.

Background of the invention Particularly in the segment of the automobile industry there is a sustained demand for finishes which exhibit an optical effect dependent on viewing angle. In order to evoke such effects, basecoat materials comprising platelet-shaped effect pigments such as aluminum flakes and/or pearlescent pigments, are typically used. These pigments adopt a substantially plane-parallel alignment in the coating film. The lightness of the resulting coating, in other words the proportion of the light reflected, decreases with an increase in the viewing angle as measured to the normal of the coating film. For the lightness flop it is possible to report the index known as the flop index. This index is calculated from the lightness L* according to the CIELab system, measured at two different angles. To obtain a high flop index in the cured coating, aqueous coating materials are generally selected which have a comparably low solids content, in the region of 10 or 15 to 20 wt.-%, since the pigment orientation is customarily promoted by the contraction of the wet film. Particularly in the production of multicoat paint systems for production-line automobile finishing (OEM finishing), high importance is attached to inorganic sheet composites, such as, for example, clay minerals, such as, more particularly, naturally occurring smectites and/or hectorites or synthetically produced smectites and/or hectorites, such as Laponite® for example, for adjusting the rheology of the color- imparting aqueous basecoat materials. The aforesaid minerals have a negative surface charge and a positive edge charge which is able to exert a positive influence on the setting of the rheology of the basecoat materials. In particular, the presence of such inorganic sheet composites allows the aqueous basecoat materials to exhibit a shear thinning behavior in order to prevent sagging of applied wet films as well as provides sufficient fluidity for the spray application process. This rheological behavior achieved by interaction of the inorganic sheet composite platelets with each other in water due to their uneven charge distribution (negatively charged surfaces, positively charged rims). Such platelets or their colloidal clusters respectively may as well interact with other colloidal particles of a coatings formulation like polymer colloids and/or molecularly dissolved polymers. Typical state of the art hectorite platelets comprising waterborne basecoat paints are complex formulations that are tuned to provide dispersions with low non-volatile contents such as, e.g., about 20 wt.-% at most, high viscosities at low shear stress (such as, e.g., about 10,000 Pa s at 1/s) and low viscosities under high shear stress (such as, e.g., 100 Pa s at 1,000/s).

Where the aqueous basecoat materials include effect pigments which give rise in particular to a viewing-angle-dependent optical effect, such as aluminum flakes or pearlescent pigments, for example, the use of the above-recited minerals is typically critical, since the baked coating films often contain impairments in the metallic effect, particularly in terms of the flop characteristics and the unwanted clouding, in other words the formation of light/dark shading.

Further, aqueous paints comprising aforesaid minerals have a tendency to form gel, which may impact on the workability of the aqueous basecoat materials or, for a given workability, limits the amount of nonvolatile material in the aqueous basecoat material. In addition, as outlined above their use is mainly limited to coating formulation with comparably low solids content in the region of 10 or 15 to about 20 wt.-% at most. For the sake of sustainability it would be highly desirable to design novel waterborne basecoat paints with distinctly higher solids content, which can be spray applied like the current products and which provide coating layers with both comparable optical properties, in particular “flop indices”, and rheological properties. In WO 2010/130308 A1 waterborne basecoat materials are disclosed, which comprise effect pigments and which exhibit an excellent flop effect in an automotive OEM finishing system, especially when used as basecoat. Factors responsible for this achievement include the mandatory use of positively charged, hydrotalcite- based inorganic particles. A disadvantage of the modified hydrotalcites, however, is that they frequently lack sufficient compatibility with various binders at high solids. In particular, their use in combination with particulate binders is restricted to very limited particle sizes.

Thus, there is a demand for coating compositions, in particular aqueous basecoat materials, which comprise platelet-shaped pigments generating a viewing-angle- dependent lightness effect, having a comparably high solids contents - in particular a higher solids content than conventional coating compositions including Laponite® containing coating compositions, - but which are nonetheless sprayable and at the same time result in coatings, which exhibit at least comparable and preferably improved optical properties, in particular - despite the comparably high solids content of the coating composition used for preparing the coatings - a pronounced lightness flop. Further, at the same the coating compositions should allow the use of a multiplicity of organic polymers, especially of polymers in particulate form with different particle diameters with minimum or no occurrence of any incompatibilities.

Problem It has been therefore an object underlying the present invention to provide coating compositions, in particular aqueous basecoat materials, which comprise platelet shaped pigments generating a viewing-angle-dependent lightness effect, having a comparably high solids contents - in particular a higher solids content than conventional coating compositions including Laponite® containing coating compositions, - but which are nonetheless sprayable and at the same time result in coatings, which exhibit at least comparable and preferably improved optical properties and in particular - despite the comparably high solids content of the coating composition used for preparing the coatings - a pronounced lightness flop Further, at the same the coating compositions should allow the use of a multiplicity of organic polymers, especially of polymers in particulate form with different particle diameters with minimum or no occurrence of any incompatibilities.

Solution

This object has been solved by the subject-matter of the claims of the present application as well as by the preferred embodiments thereof disclosed in this specification, i.e. by the subject matter described herein. A first subject-matter of the present invention is an aqueous dispersion (AD1) comprising water as component (A) and metal bisphosphonate particles as component (B), wherein at least one metal selected from the group consisting of Ti, Zr and Hf is present as metal in the metal bisphosphonate particles (B), characterized in that the metal bisphosphonate particles (B) containing aqueous dispersion (AD1) is obtainable by a process comprising at least steps (1) and (2), namely by

(1) mixing an aqueous solution of at least one disphosphonic acid with at least one metal precursor salt under stirring, wherein said metal precursor salt contains at least one metal selected from the group consisting of Ti, Zr and Hf, wherein the molar ratio of the at least one disphosphonic acid present in the aqueous solution to the at least one metal precursor salt is >1 , and wherein the at least one disphosphonic acid present in the aqueous solution has at least been partially neutralized with at least one base prior to using the aqueous solution in the mixing step (1), and by

(2) diluting the product obtained after performance of step (1) with water and performing a membrane filtration in order to produce the aqueous dispersion (AD1).

A further subject-matter of the present invention is a powder obtainable by submitting the inventive aqueous dispersion (AD1) to a freeze drying step. A further subject-matter of the present invention is an aqueous dispersion (AD2) obtainable by adding at least water to the freeze dried inventive powder.

As it will be outlined hereinafter in more detail, it is preferred that the inventive dispersion (AD1) and/or the inventive dispersion (AD2), is further submitted to a an alkalization step (3), namely by

(3) adding at least one base, in particular at least one amine and/or ammonia to the aqueous dispersion (AD1) or (AD2), such that the resulting dispersion has a pH value >7 such as a pH value in the range of 7.0 to 8.5.

A further subject-matter of the present invention is a use of the inventive aqueous dispersion (AD1 ) or of the inventive freeze-dried powder or of the inventive aqueous dispersion (AD2) for producing a coating material composition, which preferably serves for producing a coating, which exhibits a viewing-angle-dependent lightness.

A further subject-matter of the present invention is an aqueous coating material composition comprising at least one of: the inventive aqueous dispersion (AD1), the inventive freeze- dried powder and the inventive aqueous dispersion (AD2), at least one platelet-shaped pigment (EP), which generates a viewing-angle- dependent lightness effect, and at least one polymer (P) as binder.

A further subject-matter of the present invention is a substrate coated with an inventive coating material composition, preferably wherein the coating material composition, after having been cured, is present as a basecoat in a multicoat paint system.

A further subject-matter of the present invention is a method for producing a multicoat paint system, by

(la) applying an aqueous coating material composition to a substrate, which is optionally pre-coated with at least one of an electrodeposition coating and a surfacer coating,

(2a) forming a coating film from the coating material composition applied in stage

(1a),

(lb) optionally applying a further aqueous coating material composition to the coating film thus formed,

(2b) optionally forming a coating film from the coating material composition applied in stage (1b),

(3) applying a clearcoat material to the resultant coating film(s), and subsequently

(4) jointly curing the coating film(s) together with the clearcoat film, wherein the inventive aqueous coating material composition is used in stage (1a) or - if the method further comprises stages (1 b) and (2b) - in stage (1a) and/or (1 b).

It has been surprisingly found that inventive coating material compositions comprising platelet-shaped pigments generating a viewing-angle-dependent lightness effect and having comparably high solids content can be prepared by making use of the inventive aqueous dispersions (AD1) and/or (AD2) and/or of the inventive freeze dried powder as precursor(s) for preparing the coating material compositions. In particular, it has been found that due to using the inventive aqueous dispersions (AD1) and/or (AD2) and/or of the inventive freeze dried powder, coating compositions such as aqueous basecoat compositions can be prepared, which are allowed to have higher solids contents than conventional aqueous basecoat compositions including Laponite® containing coating material compositions, but are nonetheless sprayable and have an excellent rheological profile. Being able to increase the solids content without negatively affecting other optical properties such as the flop has both economic and ecological benefits as both the amounts of water and of optionally present organic solvents and the volume of the shipped coating materials in total can be reduced. It has been further surprisingly found that coatings resulting from applying the inventive coating material compositions to a suitable substrate exhibit a pronounced lightness flop despite the comparably high solids content of the inventive coating material composition used for preparing the coatings. In addition, it has been further surprisingly found that coatings resulting from applying the inventive coating material compositions to a suitable substrate also display an excellent appearance, in particular an improved appearance in comparison to conventional coating material compositions including Laponite® containing coating compositions.

Moreover, it has been further surprisingly found that the inventive coating material compositions allow for the incorporation of a multiplicity of organic polymers, especially of polymers in particulate form with different particle diameters with minimum or no occurrence of any incompatibilities. Thus, the requirements imposed on the particle diameters of such polymers are to be undemanding. In other words, it is possible to use relatively large organic particles, for example in the region of average particle sizes of up to 250 nm or more, 500 nm for example, which in conventional systems disrupt the disposition of the effect pigments, and to do so without any inacceptable losses in terms of the lightness flop. In addition, it has been found that the specific method of preparing the aqueous dispersion (AD1) including at least steps (1) and (2) is important for being able to generate an aqueous dispersion comprising the metal bisphosphonate particles (B) that exhibit(s) the advantageous properties. This can be, e.g., derived from items 1.1 , 1.2 and 1.5 of the experimental part of this application as well as from Fig. 1.

Detailed description of the invention

The term "comprising" in the context of the present invention in connection with the aqueous dispersion (AD1), the aqueous dispersion (AD2) and the coating material composition according to the invention preferably has the meaning "consisting of". In this case, in addition to the components (A) and (B) in case of (AD1) one or more of the other components mentioned hereinafter may be contained therein. All components can be present in each case in their preferred embodiments mentioned herein. The same applies to (AD2) and the inventive coating material composition according to the invention. For instance, in the latter case, in addition to (AD1), (AD2) and/or the freeze dried powder, the pigment (EP) and the polymer (P) one or more of the other components mentioned hereinafter may be contained therein. Again, all components can be present in each case in their preferred embodiments mentioned herein.

The proportions and amounts in wt.-% (% by weight) of all components (A) and (B) and further optionally present components in (AD1) and (AD2) according to the invention add up to 100 wt.-%, based on the total weight of (AD1) or (AD2), respectively.

The proportions and amounts in wt.-% (% by weight) of all components (AD1), (AD2), inventive powder, water, pigment (EP) and polymer (P) and further optionally present components in the coating material composition according to the invention add up to 100 wt.-%, based on the total weight of the coating material composition.

Aqueous dispersion AD1

A first subject-matter of the present invention is an aqueous dispersion (AD1) comprising water as component (A) and metal bisphosphonate particles as component (B). At least one metal selected from the group consisting of Ti, Zr and Hf is present as metal in the metal bisphosphonate particles (B). The metal bisphosphonate particles (B) containing aqueous dispersion (AD1) is obtainable by a process comprising at least steps (1) and (2). The inventive aqueous dispersion (AD1) can be used for producing coating material compositions, which in turn serve in particular for production of coatings which exhibit a viewing-angle-dependent lightness.

Dispersion (AD1) is an aqueous dispersion as it necessarily contains water as component (A). In addition to water it may optionally contain one or more organic solvents. Typical organic solvents used in aqueous dispersions are selected from the group consisting of water-soluble and/or water-dispersible organic solvents Such water-soluble and/or water-dispersible organic solvents belong preferably to the group consisting of monoalcohols, glycols, ethers such as glycol ethers, for example, and ketones.

The amount of organic solvents is preferably in the range of from 0 to 10 wt.-%, more preferably of from 0 to 5 wt.-%, and in particular of from 0 to 2 wt.-%, in each case based on the total weight of the aqueous dispersion (AD1 ).

The water content, based on the total weight of the volatile constituents (30 min drying time at 130 °C; 1 g sample) of the aqueous dispersion (AD1), is preferably 90 to 100 wt.-%, more preferably 95 to 100 wt.-%, such as, for example, 98 wt.-% or 99 wt.-% or more.

Step (1)

Step (1) is directed at mixing an aqueous solution of at least one disphosphonic acid with at least one metal precursor salt under stirring, wherein said metal precursor salt contains at least one metal selected from the group consisting of Ti, Zr and Hf. Preferably, the metal precursor salt contains halogenide ions, in particular chloride ions. The molar ratio of the at least one disphosphonic acid present in the aqueous solution to the at least one metal precursor salt is >1. The at least one disphosphonic acid present in the aqueous solution has at least been partially neutralized with at least one base prior to using the aqueous solution in the mixing step (1). Preferably, the at least one base used for at least partially neutralizing the at least one disphosphonic acid is an inorganic base such as KOH and/or NaOH. Preferably, an aqueous solution of the at least one inorganic base is used. As far as the partial neutralization of the disphosponic acid by the at least one base is concerned, it is preferred that on average at least one, more preferably on average eat least 1.5 of the acidic protons of the disphosponic acid used are neutralized prior to using it in the mixing step (1). Preferably, not more than 2, and more preferably less than on average 2 of the acidic protons of the disphosponic acid used are neutralized prior to using it in the mixing step (1 ).

The metal precursor salt used in step (1) may be employed as such in step (1). Alternatively and preferably, an aqueous solution of the metal precursor salt is used in step (1 ), i.e. an aqueous solution of at least one disphosphonic acid is mixed with an aqueous solution of at least one metal precursor salt under stirring in step (1 ).

Preferably, the metal precursor salt contains at least one metal selected from the group consisting of Ti and Zr. In particular, the metal precursor salt contains Zr. A particularly preferred metal precursor salt is zirconium oxychloride octahydrate (Zr0CI ₂ -8H ₂ 0)

Any suitable disphosphonic acid can be used as long as the disphosphonic acid is soluble in water. Particularly preferred disphosphonic acids are etidronic acid (C ₂ H ₈ 0 ₇ P ₂ , 1 -hydroxyethane 1 ,1-diphosphonic acid, HEDP) and/or medronic acid (methanediylbis(phosphonic acid)).

Most preferred inventively used metal bisphosphonate particles (B) are obtained from the self-assembly of zirconium bisphosphonate in aqueous phase, in particular by making use of 1 -hydroxyethane 1 ,1-diphosphonic acid as disphosphonic acid.

The molar ratio of the at least one disphosphonic acid present in the aqueous solution to the at least one metal precursor salt is preferably >1.1:1, more preferably >1.5:1. Preferably, the molar ratio of the at least one disphosphonic acid present in the aqueous solution to the at least one metal precursor salt does not exceed a ratio of 10:1, more preferably of 5:1, even more preferably of 3:1, yet more preferably of 2.5:1 , still more preferably of 2:1.

Step (2)

Step (2) is diluting the product obtained after performance of step (1) with water and performing a membrane filtration, in particular a tangential flow filtration (TFF), in order to produce the aqueous dispersion (AD1).

Membrane filtration is a separation technique known to a person skilled in the art. Depending on membrane porosity, membrane filtration techniques comprise microfiltration and ultrafiltration techniques. In case of microfiltration membranes with pore sizes typically between 0.1 pm and 10 pm are used. Ultrafiltration membranes typically have smaller pore sizes between 0.001 and 0.1 pm. Ultrafiltration membranes are typically classified by molecular weight cutoff (MWCO) rather than pore size. In general, there are two main membrane filtration modes, which make use of either microfiltration or ultrafiltration membranes, namely Direct Flow Filtration (DFF), which typically applies the feed stream perpendicular to the membrane face and attempts to pass all of the fluid through the membrane, and Tangential Flow Filtration (TFF), also known as crossflow filtration, where the feed stream passes parallel to the membrane face as one portion passes through the membrane (permeate) while the remainder (retentate) is recirculated back to the feed reservoir. Preferably, the membrane filtration employed in step (2) is Tangential Flow Filtration (TFF). As membrane a polyethersulfone membrane can be used. A suitable polyethersulfone membrane is e.g. a Biomax® membrane having a pore size equivalent to 1,000 kDa) in combination with a Cogent mScale TFF system (Millipore, Burlington, MA, USA) and a Pellicon XL module.

Optional step (3)

Preferably, dispersion (AD1) is further submitted to an alkalization step (3), namely by

(3) adding at least one base, in particular at least one amine and/or ammonia, to the aqueous dispersion (AD1) such that the resulting dispersion has a pH value >7 such as a pH value in the range of 7.0 to 8.5. The aqueous dispersion (AD1) obtained after step (2) is preferably an acidic dispersion having a pH value in the range of from 1.5 to 3. In optional step (3) the acidic dispersions are neutralized and/or alkalized with at least one base such as at least one amine such as dimethyl ethanol amine (DMEA) and/or ammonia. Performing of step (3) has the advantage that the dispersion (AD1) is less hazy and in particular can be clear and exhibits an increased viscosity. The resulting dispersion shows birefringence using cross polarized light, which indicates the presence of ordered domains of the metal bisphosphonate particles (B). Preferably, metal bisphosphonate particles (B) are in the form of ribbons and/or wires. Thus, preferably the length of the particles (B) is larger than the thickness of the particles (B).

Preferably, the molar ratio of the at least one metal, in particular Zr, to phosphorous (P), in the metal bisphosphonate particles (B) is in the range of from 2.5:0.5, more preferably of from 2.2:0.8, even more preferably of from 2:1. In particular, the molar ratio is precisely 2:1.

Preferably, the metal bisphosphonate particles (B) present in aqueous dispersion (AD1 ) have a thickness in the range of from 1 to 50 nm, more preferably of from 2 to 45 nm, even more preferably of from 3 to 40 nm, yet more preferably of from 4 to 35 nm, still more preferably of from 5 to 30 nm, in particular of from 7.5 to 25 nm and most preferably of from 10 to 20 nm. The thickness is measured by TEM in combination with SAXS as outlined in “Methods” hereinafter.

Preferably, the metal bisphosphonate particles (B) present in aqueous dispersion (AD1) have a particle length in the range of from 200 to 5000 nm, more preferably of from >200 to 5000 nm, even more preferably of from 300 to 4500 nm, yet more preferably of from 400 to 4000 nm, still more preferably of from 500 to 3500 nm, in particular of from 750 to 3000 nm and most preferably of from 1000 to 2500 nm. The particle length is measured by TEM in combination with SAXS as outlined in “Methods” hereinafter. Preferably, the metal bisphosphonate particles (B) present in aqueous dispersion (AD1) have an aspect ratio in the range of from 4 to 5000, more preferably of from 5 to <5000, even more preferably of from 10 to 4000, yet more preferably of from 25 to 3000, still more preferably of from 50 to 2000, in particular of from 75 to 1000 and most preferably of from 100 to <1000 or of from 110 to 750 or of from 120 to 500. The aspect ratio is the quotient formed from the length of the particles (B) and its thickness, respectively. The particle length is measured by TEM in combination with SAXS and the thickness is measured by TEM in combination with SAXS as outlined in “Methods” hereinafter.

If the aspect ratio is too small, e.g., is <4, or, more preferably is <10, the isotropic to nematic phase transition will be shifted to larger volume fractions of the anisotropic particles (B). This would increase the necessary amount of the particles to be used in order to observe the desired effect in a coating material composition. This would in turn induce a barrier effect and hinder the evaporation of the water and, where appropriate, of the organic solvents, a hindrance which may lead to coating film defects. If the aspect ratio is too large, i.e. is >5000 or, more preferably >1000, the particles (B) might begin to entangle and hamper the alignment and formation of a lyotropic liquid crystalline phase. Furthermore, the entanglement may cause an increased viscosity which necessitates lower solid contents for the coating application.

Preferably, the metal bisphosphonate particles (B) present in aqueous dispersion (AD1) fulfil at least one, preferably at least two, and more preferably all three of the following criteria:

(i) the metal bisphosphonate particles (B) have a thickness in the range of from 1 to 50 nm or have a thickness being in any of the preferred ranges set out hereinbefore in connection with the particles (B) present in (AD1), (ii) the metal bisphosphonate particles (B) have a particle length in the range of from 200 to 5000 nm or have a length being in any of the preferred ranges set out hereinbefore in connection with the particles (B) present in (AD1), and/or (iii) the metal bisphosphonate particles (B) have an aspect ratio in the range of from 4 to 5000 or have an aspect ratio being in any of the preferred ranges set out hereinbefore in connection with the particles (B) present in (AD1). Preferably, the amount of metal bisphosphonate particles (B) in the aqueous dispersion (AD1) is in the range of from 0.01 to 10 wt.-%, more preferably in the range of from 0.05 to 7.5 wt.-%, even more preferably in the range of from 0.1 to 7.5 wt.-%, still more preferably in the range of from 0.2 to 5 wt.-%, yet more preferably in the range of from 0.3 to 3.5 wt.-%, in particular in the range of from 0.5 to 2.5 wt.-%, in each case based on the total weight of the respective aqueous dispersion (AD1 ).

Preferably, the metal bisphosphonate particles (B) are present in preferably lyotropic liquid crystalline phases. Freeze-dried powder

A further subject-matter of the present invention is a powder obtainable by submitting the inventive aqueous dispersion (AD1) to a freeze drying step. The inventive powder is thus a freeze-dried powder.

Preferably, the metal bisphosphonate particles (B) present in/of the freeze-dried powder have a thickness in the range of from 5 to 200 nm, more preferably of from 5 to <200 nm, even more preferably of from 25 to 190 nm, yet more preferably of from 35 to 180 nm, still more preferably of from 45 to 160 nm, in particular of from 50 to 150 nm and most preferably of from >50 to <150 nm. The thickness is measured by

TEM in combination with SAXS as outlined in “Methods” hereinafter.

Preferably, the metal bisphosphonate particles (B) present in/of the freeze dried powder have a particle length in the range of from 200 to 5000 nm, more preferably of from >200 to 5000 nm, even more preferably of from 300 to 4500 nm, yet more preferably of from 400 to 4000 nm, still more preferably of from 500 to 3500 nm, in particular of from 750 to 3000 nm and most preferably of from 1000 to 2500 nm. The particle length is measured by TEM in combination with SAXS as outlined in “Methods” hereinafter.

Preferably, the metal bisphosphonate particles (B) present in/of the freeze dried powder have an aspect ratio in the range of from 1 to 1000, more preferably of from

>1 to <1000, even more preferably of from 4 to 1000, yet more preferably of from 10 to 900, still more preferably of from 50 to 800, in particular of from 75 to 600 and most preferably of from 110 to 500 or of from 110 to 400 or of from 110 to 300. The aspect ratio is the quotient formed from the length of the particles (B) and its thickness, respectively. The particle length is measured by TEM in combination with SAXS and the thickness is measured by TEM in combination with SAXS as outlined in “Methods” hereinafter.

Preferably, the metal bisphosphonate particles (B) present in/of the freeze-dried powder fulfil at least one, preferably at least two, and more preferably all three of the following criteria:

(i) the metal bisphosphonate particles (B) have a thickness in the range of from 5 to

200 nm or have a thickness being in any of the preferred ranges set out hereinbefore in connection with the particles (B) present in/of the freeze-dried powder,

(ii) the metal bisphosphonate particles (B) have a particle length in the range of from 200 to 5000 nm or have a length being in any of the preferred ranges set out hereinbefore in connection with the particles (B) present in/of the freeze-dried powder and/or

(iii) the metal bisphosphonate particles (B) have an aspect ratio in the range of from 1 to 1000 or have an aspect ratio being in any of the preferred ranges set out hereinbefore in connection with the particles (B) present in/of the freeze-dried powder.

All further preferred embodiments described hereinabove in connection with the aqueous dispersion (AD1) of the invention and its constituents are also preferred embodiments in relation to the inventive freeze dried powder. Preferably, the inventive aqueous dispersion (AD1) obtained after step (1) is freeze dried at a temperature in the range of from -60°C to -100°C. Preferably, freezing is performed before evacuation. For example, a Christ Epsilon 2-4 LSC freeze drier (Christ GmbH, Osterode, Germany) can be used. Preferably, sublimation is performed under 50 Pa with shelf and ice-condenser temperatures of +20 °C and -20 °C respectively. For the final drying/desorption step the shelf temperature is preferably raised to 40 °C and the pressure lowered to 1-10 Pa, preferably for approximately 1 h. The obtained powder, i.e. freeze-dried powder can be used for incorporation into coating material compositions as such or can be dispersed into water. In the latter case, an aqueous dispersion (AD2) is formed.

Aqueous dispersion AD2 A further subject-matter of the present invention is an aqueous dispersion (AD2) obtainable by adding at least water to the freeze dried inventive powder.

Preferably, the metal bisphosphonate particles (B) present in the aqueous dispersion (AD2) have a thickness in the range of from 5 to 200 nm, more preferably of from 5 to <200 nm, even more preferably of from 25 to 190 nm, yet more preferably of from 35 to 180 nm, still more preferably of from 45 to 160 nm, in particular of from 50 to 150 nm and most preferably of from >50 to <150 nm. The thickness is measured by TEM in combination with SAXS as outlined in “Methods” hereinafter. Preferably, the metal bisphosphonate particles (B) present in aqueous dispersion (AD2) have a particle length in the range of from 200 to 5000 nm, more preferably of from >200 to 5000 nm, even more preferably of from 300 to 4500 nm, yet more preferably of from 400 to 4000 nm, still more preferably of from 500 to 3500 nm, in particular of from 750 to 3000 nm and most preferably of from 1000 to 2500 nm. The particle length is measured by TEM in combination with SAXS as outlined in “Methods” hereinafter. Preferably, the metal bisphosphonate particles (B) present in aqueous dispersion (AD2) have an aspect ratio in the range of from 1 to 1000, more preferably of from >1 to <1000, even more preferably of from 4 to 1000, yet more preferably of from 10 to 900, still more preferably of from 50 to 800, in particular of from 75 to 600 and most preferably of from 110 to 500 or of from 110 to 400 or of from 110 to 300. The aspect ratio is the quotient formed from the length of the particles (B) and its thickness, respectively. The particle length is measured by TEM in combination with SAXS and the thickness is measured by TEM in combination with SAXS as outlined in “Methods” hereinafter.

Preferably, the metal bisphosphonate particles (B) present in aqueous dispersion (AD2) fulfil at least one, preferably at least two, and more preferably all three of the following criteria: (i) the metal bisphosphonate particles (B) have a thickness in the range of from 5 to

200 nm or have a thickness being in any of the preferred ranges set out hereinbefore in connection with the particles (B) present in (AD2),

(ii) the metal bisphosphonate particles (B) have a particle length in the range of from 200 to 5000 nm or have a length being in any of the preferred ranges set out hereinbefore in connection with the particles (B) present in (AD2), and/or

(iii) the metal bisphosphonate particles (B) have an aspect ratio in the range of from 1 to 1000 or have an aspect ratio being in any of the preferred ranges set out hereinbefore in connection with the particles (B) present in (AD2). All further preferred embodiments described hereinabove in connection with the aqueous dispersion (AD1) of the invention and its constituents and the inventive freeze dried powder are also preferred embodiments in relation to the aqueous dispersion (AD2) of the invention. The inventive aqueous dispersion (AD2) can be used for producing coating material compositions, which in turn serve in particular for the production of coatings which exhibit a viewing-angle-dependent lightness. Preferably, dispersion (AD2) is further submitted to an alkalization step (3), which corresponds to step (3) optionally performed for inventive aqueous dispersion (AD1), namely by (3) adding at least one base, in particular at least one amine and/or ammonia, to the aqueous dispersion () such that the resulting dispersion has a pH value >7 such as a pH value in the range of 7.0 to 8.5.

In optional step (3) the acidic dispersion (AD2) is neutralized and/or alkalized with at least one base such as at least one amine such as dimethyl ethanol amine (DMEA) and/or ammonia.

Performing of step (3) has the advantage that the dispersion (AD2) is less hazy and in particular clear and exhibits an increased viscosity. The resulting dispersion shows birefringence using cross polarized light, which indicates the presence of ordered domains that are formed by the metal bisphosphonate particles (B). However, the birefringent domains are coarser than those observed with (AD1) and are in coexistence with isotropic liquid. Step (3) in connection with (AD2) is preferably carried out when (AD1) - used for preparing the inventive freeze dried powder - has not been subjected to optional step (3) prior to the freeze drying process.

Preferably, the amount of metal bisphosphonate particles (B) in the aqueous dispersion (AD2) is in the range of from 0.01 to 10 wt.-%, more preferably in the range of from 0.05 to 7.5 wt.-%, even more preferably in the range of from 0.1 to 7.5 wt.-%, still more preferably in the range of from 0.2 to 5 wt.-%, yet more preferably in the range of from 0.3 to 3.5 wt.-%, in particular in the range of from 0.5 to 2.5 wt.-%, in each case based on the total weight of the respective aqueous dispersion (AD2). Inventive use

A further subject-matter of the present invention is a use of the inventive aqueous dispersion (AD1 ) or of the inventive freeze-dried powder or of the inventive aqueous dispersion (AD2) for producing a coating material composition, which preferably serves for producing a coating, which exhibits a viewing-angle-dependent lightness.

All preferred embodiments described hereinabove in connection with the aqueous dispersion (AD1) of the invention and its constituents, the inventive freeze dried powder, and the aqueous dispersion (AD2) of the invention and its constituents are also preferred embodiments in relation to the inventive use.

Coating material composition, method and coated substrate

A further subject-matter of the present invention is an aqueous coating material composition comprising at least one of: the inventive aqueous dispersion (AD1), the inventive freeze- dried powder and the inventive aqueous dispersion (AD2), at least one platelet-shaped pigment (EP), which generates a viewing-angle- dependent lightness effect, and at least one polymer (P) as binder.

All preferred embodiments described hereinabove in connection with the aqueous dispersion (AD1) of the invention and its constituents, the inventive freeze dried powder, and the aqueous dispersion (AD2) of the invention and its constituents, as well as the inventive use are also preferred embodiments in relation to the inventive coating material compositions and its constituents. The inventive coating composition (also synonymously named “coating material composition” herein) is preferably a basecoat composition. More preferably, the inventive coating composition is an aqueous basecoat composition (in the following also referred to as waterborne basecoat composition). Even more preferably, the inventive coating composition is used as a 1K-waterborne basecoat composition.

The coating composition according to the invention is thus preferably suitable for producing a basecoat film. The term of the basecoat is known in the art and, for example, defined in Rompp Lexikon, paints and printing inks, Georg Thieme Verlag, 1998, 10th edition, page 57. A basecoat is therefore in particular used in automotive painting and general industrial paint coloring in order to give a coloring and/or an optical effect by using the basecoat as an intermediate coating composition. This is generally applied to a metal or plastic substrate, optionally pretreated with primer and/or filler, sometimes in the case of plastic substrates also directly on the plastic substrate, and in the case of metal substrates on an electrodeposition coating layer coated onto the metal substrate or on the metal substrate already bearing a primer and/or filler and/or electrodeposition coating, or to already existing coatings in case of refinish applications, which can also serve as substrates. In order to protect a basecoat film in particular against environmental influences, at least one additional clearcoat film is preferably applied onto it.

The coating material compositions of the invention are preferably aqueous basecoat compositions which are applied to a coated or uncoated substrate and are provided preferably with a clearcoat system.

Since the aqueous coating material compositions of the invention are obtained using one of the aqueous dispersions (AD1) or (AD2) of the invention, all constituents of (AD1) and/or (AD2) are also constituents of the coating material compositions of the invention. In addition to this, the coating material compositions of the invention necessarily comprise platelet-shaped pigments (EP) which generate a viewing- angle-dependent lightness effect (also referred to below for short as platelet-shaped effect pigments) as well as at least one polymer (P).

Platelet-shaped pigments (EP)

The platelet-shaped pigments (EP) used in the context of the present invention give the cured coating a viewing-angle-dependent lightness (lightness flop). The platelet shaped pigments are thus effect pigments. A skilled person is familiar with the concept of the effect pigments. A corresponding definition is found for example in Rompp Lexikon, Lacke und Druckfarben, Georg Thieme Verlag, 1998, 10th edition, pages 176 and 471. A definition of pigments in general, and further particularizations thereof, are governed in DIN 55943 (date: October 2001). Effect pigments are preferably pigments which impart optical effect or both color and optical effect, especially optical effect. The terms "optical effect and color pigment", "optical effect pigment" and "effect pigment" are therefore preferably interchangeable.

Preferably, the platelet-shaped pigment (EP) is selected from the group consisting of metallic effect pigments and pearlescent pigments. Examples of such effect pigments are metallic pigments such as, for example, aluminum, iron, or copper pigments, interference pigments such as, for example, titanium dioxide-coated mica, iron oxide-coated mica, mixed oxide-coated mica, metal oxide-coated mica, or liquid-crystal pigments. Preferred effect pigments in accordance with the invention are platelet-shaped metallic pigments, preferably aluminum pigments, such as, in particular, leafing or non-leafing pigments (in this regard, compare BASF Handbuch Lackiertechnik, pages 164 ff . , Vincentz-Verlag, Hannover, 2002), and/or mica pigments, interference pigments, and pearlescent pigments (in this regard, compare BASF Handbook on Basics of Coating Technology, pages 162 ff., Vincentz-Verlag, Hannover, 2002.

The amount of platelet-shaped effect pigments for inventive use in the coating material compositions may vary widely and is guided on the one hand by the opacity of the effect pigment and by the intensity of the optical effect it is desired to obtain. Typically the coating material composition of the invention comprises 2 to 15 wt.-% or 2 to 10 wt.-%, based on the total weight of the coating material composition, of platelet-shaped pigments which generate a viewing-angle-dependent lightness effect.

Polymer (P)

The term "polymer" is familiar to the skilled person and for the purposes of the present invention encompasses polyadducts, addition polymers such as chain- growth addition polymers, and polycondensates. The term "polymer" subsumes both homopolymers and copolymers. The polymers may be purely physically curing, self crosslinking and/or externally crosslinking. External crosslinking takes place with use of crosslinking agents. The amount of the at least one polymer (P) is preferably in the range of from 5 to 55 wt.-%, more preferably of from 10 to 50 wt.-%, and in particular of from 15 to 40 wt.-%, in each case based on the total weight of the coating material composition. Preferably, the at least one polymer (P) is selected from the group consisting of polyesters, polyurethanes, polyureas, polyepoxides, poly(meth)acrylates, polystyrenes and copolymers, hybrids, or microgels of the stated polymers such as polyurethane-poly(meth)acrylates and/or polyurethane-polyureas, as well as mixtures thereof.

Preferred polyurethanes are described for example in German patent application DE 19948004 A1, page 4, line 19 to page 11, line 29 (polyurethane prepolymer B1 ), in European patent application EP 0228003 A1 , page 3, line 24 to page 5, line 40, in European patent application EP 0634431 A1, page 3, line 38 to page 8, line

9, in European patent specification EP-B1-2430 120 in paragraphs [0022] and [0031], and in international patent application WO 92/15405, page 2, line 35 to page

10, line 32. Preferred polyesters are described for example in DE 4009858 A1 in column 6, line 53 to column 7, line 61 and column 10, line 24 to column 13, line 3 in European patent specification EP-B1-2430 120 in paragraphs [0007] to [0012] and [0030], or in WO 2014/033135 A2, page 2, line 24 to page 7, line 10 and also page 28, line 13 to page 29, line 13. Likewise preferred polyesters are polyesters with dendritic structure of the kind described for example in WO 2008/148555 A1.

Preferred polyurethane-poly(meth)acrylate copolymers ((meth)acrylated polyurethanes) and their preparation are described for example in WO 91/15528 A1, page 3, line 21 to page 20, line 33, and also in DE 4437535 A1, page 2, line 27 to page 6, line 22.

Preferred polyurethane-polyurea copolymers are polyurethane-polyurea particles, preferably those with an average particle size of 40 to 500 nm, where the polyurethane-polyurea particles, in each case in reacted form, comprise at least one polyurethane prepolymer containing isocyanate groups and containing anionic groups and/or groups which can be converted into anionic groups, and also at least one polyamine containing two primary amino groups and one or two secondary amino groups. Such copolymers are used preferably in the form of an aqueous dispersion. Polymers of these kinds are preparable in principle by conventional polyaddition of, for example, polyisocyanates with polyols and also polyamines.

Preferred poly(meth)acrylates are those which can be prepared by multistage radical emulsion polymerization of olefinically unsaturated monomers in water and/or organic solvents. Particularly preferred, for example, are seed-core-shell polymers (SCS polymers). Such polymers and aqueous dispersions comprising such polymers are known from WO 2016/116299 A1 , for example. Particularly preferred seed-core- shell polymers are polymers - preferably those having an average particle size of 100 to 500 nm - that are prepared by successive radical emulsion polymerization of preferably two or more different aqueous mixtures of monomers with olefinic unsaturation.

The at least one polymer (P) present in the inventive coating material composition can be an anionically and/or non-ionically stabilized organic polymer.

Anionically stabilized organic polymers are understood to be organic polymers, which contain groups that are capable of forming anions and that after their neutralization or salification ensure that the polymers can be stably dispersed or molecularly dissolved in water. Examples of suitable groups capable of forming anions are carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, sulfate groups, and phosphate groups, preferably carboxylic acid groups. For the neutralization or salification of the groups capable of forming anions, preference is given to using ammonia, amines and/or amino alcohols, such as, for example, di- and triethylamine, dimethylaminoethanolamine, diisopropanolamine, morpholines and/or N-alkyl morpholines.

Non-ionically stabilized polymers are in general organic polymers of the kind incorporating hydrophilic sections, as for example polyoxyalkylene sections, especially polyoxyethylene sections.

Some polymers are stabilized both an-ionically and non-ionically, in that they embody the different modes of stabilization in one kind of polymer. The anionically and/or non-ionically stabilized organic polymers used may be in molecularly dissolved form, meaning that they are water-soluble, or may be in the form of particles, meaning that they are water-dispersible. In general, the anionically and/or non-ionically stabilized organic polymers are at least water-dispersible.

The use of the aqueous dispersions (AD1) and (AD2) of the invention for preparing coating material compositions is especially advantageous, when the anionically and/or nonionically stabilized polymers are in the form of particles. The particles preferably have an average particle diameter < 500 nm, more preferably < 350 nm, such as typically from 10 to 350 nm, preferably 20 to 300 nm, more preferably 25 to 280 nm. The method for measurement of the average particle diameter is disclosed hereinafter in the section entitled “methods”. Preferably, the anionically and/or nonionically stabilized organic polymer is composed of polymer particles present in dispersed form as liquid or solid particles, which have an average particle diameter in the range of from 2 nm up to 300 nm.

Preferably, the inventive coating material composition has a non-volatile content of >20 wt.-%, preferably of >25 wt.-%. Preferably, the non-volatile content does not exceed 50 wt.-%, preferably does not exceed 45 wt.-%, in particular does not exceed 40 wt.-% or 35 wt.-%. The non-volatile content is preferably in the range of from >20 to 50 wt.-%, more preferably of from >25 to 45 wt.-%, more particularly of >25 to 40 wt.-%.

Preferably, the inventive coating material composition comprises, based on the total weight of the coating material composition,

0.05 to 5 wt.-%, more preferably 0.1 to 2.5 wt.-%, of the metal bisphosphonate particles (B),

2 to 15 wt.-%, more preferably 2 to 10 wt.-%,of the at least one platelet shaped pigment, which generates a viewing-angle-dependent lightness effect, and 5 to 50 wt.-%, more preferably 10 to 40 wt.-%, of the at least one polymer (P).

In addition, the inventive coating material composition preferably comprises water in an amount in the range of from 10 to 65 wt.-%, more preferably 15 to 50 wt.-%. Of course, the amounts of all constituents present in the inventive coating material composition add up to 100 wt.-%.

The coating material composition of the invention may further comprise at least one crosslinking agent. Where crosslinking agents are present, they are preferably selected from the group of crosslinking agents which bring about crosslinking only at relatively high temperatures, typically at or above 80°C, preferably at or above 100°C, and more preferably at or above 120°C. Aforesaid crosslinking agents are preferably selected from the group consisting of amino resins such as, for example, unetherified or wholly or partly etherified melamine-formaldehyde resins, blocked or free polyisocyanates, especially blocked polyisocyanates, phenolic resins, and trisalkoxycarbamatotriazines (TACT). The coating material compositions of the invention can be formulated as 1K- or as 2K-coating material formulation. In case they are formulated as 1K-coating material compositions the optionally present at least one crosslinking agent is preferably selected from the group consisting of amino resins such as, for example, unetherified or wholly or partly etherified melamine-formaldehyde resins, blocked polyisocyanates and trisalkoxycarbamatotriazines (TACT) as well as mixtures thereof. In case they are formulated as 2K-coating material compositions the optionally present at least one crosslinking agent is preferably selected from the group consisting of free polyisocyanates. Furthermore, the coating material composition of the invention may comprise customary coatings additives. Thus, for example, there may be coloring pigments, different from the aforesaid platelet-shaped effect pigments, and there may also be customary fillers, in known amounts in the coating material composition. The pigments and/or fillers may consist of organic or inorganic compounds and are recited by way of example in EP-A-1 192200. Preferably these further pigments and/or fillers have average particle sizes of less than 500 nm, more preferably less than 350 nm. With very particular preference the particle sizes of the further pigments and/or fillers are in the region of the particle sizes of the polymers (P) as present in the coating material composition. In case coloring pigments and/or fillers are present, it is likewise desirable to incorporate such pigments and fillers having thicknesses and lengths comparable with the particles (B) in order to not cause any notable losses in terms of the lightness flop.

A “filler” for the purposes of the present invention is preferably a component, which is substantially, preferably entirely, insoluble in the medium surrounding them, such as the coating material composition of the invention, for example, and which is used in particular for increasing the volume. “Fillers” in the sense of the present invention preferably differ from “pigments” in their refractive index, which for fillers is < 1.7, while the refractive index for pigments is > 1.7. Preferably, a “filler” for the purposes of the present invention is an inorganic filler. Examples are, e.g., barium sulfate or talcum. Further additives which can be employed are, for example UV absorbers, radical scavengers, slip additives, polymerization inhibitors, defoamers, emulsifiers, wetting agents, flow control agents, film-forming assistants, rheology control additives, and, preferably, crosslinking catalysts. Further examples of suitable coatings additives are described for example in the textbook "Lackadditive" by Johan Bieleman, Verlag Wiley-VCFI, Weinheim, New York, 1998.

Production of the coating material compositions of the invention may take place according to any methods customary and known in the paints field, in suitable mixing assemblies, such as stirred tanks or dissolvers.

Preferably, the inventive aqueous dispersion (AD1), the inventive freeze-dried powder and/or the inventive aqueous dispersion (AD2) is/are introduced initially, then the preferably pre-dispersed platelet-shaped effect pigment is added and then all remaining further constituents are added with stirring.

The coating material compositions of the invention are applied, preferably for the formation of basecoat films, preferably in a wet film thickness such that after the thermal treatment for removing the volatile constituents in the resulting films, the dry film thickness is between 5 and 50 pm, preferably between 6 and 40 pm, more preferably between 7 and 30 pm, more particularly between 8 and 25 pm. Dry film thicknesses are determined as described in the experimental section.

The coating material compositions of the invention may be applied by customary application methods, such as, for example, spraying, knife coating, spreading, pouring, dipping, or rolling. Where spray application methods are employed, preference is given to compressed-air spraying, airless spraying, high-speed rotary spraying, and electrostatic spray application (ESTA).

Application of the coating material compositions of the invention is carried out in general at temperatures of at most 70 to 80°C, so that suitable application viscosities can be achieved without, during the short period of exposure to thermal loading, any change or damage to the coating material and to its overspray, which may be intended for reprocessing. Application is accomplished preferably at a temperature of 15 to 30°C, more preferably at a temperature of 20 to 25°C such as, for example, room temperature (23°C). The preferred thermal treatment of the applied layer of the coating material composition of the invention takes place according to the known methods, such as, for example, by heating in a forced air oven or by irradiation with infrared lamps. Thermal curing is effected advantageously at temperatures between 80 and 180°C, preferably between 100 and 160°C, for a time of between 1 minute and 2 hours, preferably between 2 minutes and 1 hour, more preferably between 10 and 45 minutes. Where substrates are used, such as metals, for example, which are highly thermally robust, the thermal treatment may also be carried out at temperatures above 180°C. Generally speaking, however, it is advisable not to exceed temperatures of 160 to 180°C.

Where, on the other hand, substrates are used, such as plastics, for example, which can be exposed thermally only up to a maximum limit, the temperature and the required time for the curing operation must be brought into line with this maximum limit. Thermal curing may take place after a certain rest time of 30 seconds to 2 hours, preferably of 1 minute to 1 hour, more particularly of 2 to 30 minutes. The rest time in particular serves for the flow and the degassing of the applied film of coating material, or the evaporation of volatile constituents, such as water and any organic solvents present. The rest time may be supported and shortened through application of elevated temperatures of up to 80°C, provided this does not entail any damage or change to the applied films, such as premature complete crosslinking, for instance.

The coating material composition of the invention, particularly as a basecoat material, is suitable for numerous applications in the fields of automotive OEM finishing, automotive refinishing, and industrial coating, particularly the coating of strip metal (coil coating).

The coating material composition of the invention is used preferably as a basecoat in OEM coating systems on metallic substrates and/or plastic substrates. These systems in the case of metal substrates, considered from the substrate out, consist of an electrolytically deposited anticorrosion layer, preferably a cathodically deposited layer, optionally a surfacer layer applied thereto, and a topcoat layer, which is applied on the surfacer layer and is made up preferably of the coating material composition of the invention and of a concluding clearcoat. In this system, the electrocoat material, more particular the cathodic deposition material, is cured before the surfacer is applied. In a subsequent step, the surfacer is applied and the resulting surfacer film is preferably cured. After that, in two further stages, first the coating material composition of the invention and lastly a clearcoat are applied. In one preferred method, in a first step, the coating material composition of the invention is applied and is flashed off for a time of between 1 to 30 minutes, preferably between 2 and 25 minutes, at temperatures between 20 and 90°C, preferably between room temperature (23°C) and 80°C, and in a concluding step this film is coated in turn with a clearcoat, preferably a two-component clearcoat, with the coating material composition of the invention and the clearcoat being cured jointly.

In a further embodiment of the invention, the surfacer film, before the film of the coating material composition of the invention is applied, is flashed off for a time of between 1 to 30 minutes, preferably between 2 and 20 minutes, at temperatures between 40 and 90°C, preferably between 50 and 80°C. After that, surfacer film, basecoat film comprising the coating material composition of the invention, and clearcoat film are cured jointly. The OEM coat systems produced in such a way exhibit significantly increased viewing-angle-dependent reflection behavior (lightness flop) on the part of the basecoat film composed of the coating material composition of the invention, in comparison to OEM coat systems with noninventive basecoats. A further subject-matter of the present invention is a substrate coated with an inventive coating material composition, preferably wherein the coating material composition, after having been cured, is present as a basecoat in a multicoat paint system. With particular preference there is an electrocoat and/or a surfacer coat present between the substrate and the basecoat, and there is a clearcoat on the basecoat, with coats being present in cured form.

Preferably, between the substrate and the basecoat there is an electrocoat and/or a surfacer coat, and on the basecoat a clearcoat and all coats are cured. A further subject-matter of the present invention is a method for producing a multicoat paint system, by (la) applying an aqueous coating material composition to a substrate, which is optionally pre-coated with at least one of an electrodeposition coating and a surfacer coating, (2a) forming a coating film from the coating material composition applied in stage

(1a),

(lb) optionally applying a further aqueous coating material composition to the coating film thus formed,

(2b) optionally forming a coating film from the coating material composition applied in stage (1b),

(3) applying a clearcoat material to the resultant coating film(s), and subsequently

(4) jointly curing the coating film(s) together with the clearcoat film, wherein the inventive aqueous coating material composition is used in stage (1a) or - if the method further comprises stages (1 b) and (2b) - in stage (1a) and/or (1 b).

All preferred embodiments described hereinabove in connection with the aqueous dispersion (AD1) of the invention and its constituents, the inventive freeze dried powder, the aqueous dispersion (AD2) of the invention and its constituents, the inventive use, and the inventive coating material compositions and its constituents are also preferred embodiments in relation to the inventive coated substrate and to the inventive method. METHODS

1. Nonvolatile fraction (NVC fraction or NVC content)

The nonvolatile fraction (nonvolatile content, solids content) is determined according to DIN EN ISO 3251 (date: June 2008). 1 g of sample is weighed out into an aluminum dish which has been dried beforehand and the dish with sample is dried in a drying cabinet at 130°C for 60 minutes, cooled in a desiccator, and then reweighed. The residue relative to the total amount of sample used corresponds to the nonvolatile fraction.

2. Film thicknesses

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

3. Determination of number average and weight average molecular weight (M _n and M _w l

Number average and weight average molecular weights (M _n and M _w ) are determined by gel permeation chromatography according to standards DIN 55672-1 to -3 (date: March 2016) with PMMA standards.

4. Determination of thickness, length and aspect ratio of particles (B)

Thickness, length and aspect ratio are determined by TEM analysis, in particular high resolution TEM analysis (HRTEM), in combination with SAXS (Small-angle X- ray scattering). The length of the particles is to be understood herein as an estimated consistent, minimal value from TEM image evaluation and SAXS. (SAXS) can be carried out at any suitable measuring unit of a synchrotron X-ray source (https://liqhtsources.org) like the ID02 high brilliance beam-line of the European Synchrotron Radiation Facility (ESRF, Grenoble, France). For the purpose of the present invention monochromatic radiation (l = 0.1 nm) was used with a source- sample distance of 55 m and varying sample-detector distances (max range 1 to 10 m) in order to cover an overall g-range of 0.0025 - 11 nm ¹ . Intensities were corrected for water filled glass capillaries. In principle the g-range could be extended down to 0.001 nm ¹ (« 6,300 nm). Samples for TEM analysis were 1:50 diluted with deionized water and a 1.5 pi droplet was dried on the sample holder (porous carbon sheet). If necessary, the diluted sample can be centrifuged and a 1.5 pi droplet can be taken from the lower part of the liquid for TEM analysis. Low dose HRTEM was performed using HAADF with an overall dose per image of 50 pA. Equivalent results could be obtained with bright-field STEM using a dose of 0.7 pA.

5. ICP-OES

The content of certain elements of a sample to be tested, such as O, P and Zr, is determined by inductively coupled plasma atomic emission spectrometry (ICP-OES) in accordance with DIN EN ISO 11885 (date: September, 2009). This sample is thermally excited in an argon plasma generated by a high-frequency field and the light emitted due to electron transitions is visible as a spectral line of the corresponding wavelength and analyzed with an optical system. There is a linear relationship between the intensity of the emitted light and the concentration of the corresponding element such as O, P or Zr. Prior to the execution, calibration measurements are performed on the basis of known element standards (reference standards), which depend on the respective sample to be examined. 6. Flop index

The viewing-angle-dependent lightness of the applied coatings was evaluated (of. Fig. 4) using the MACi spectrophotometer from BYK Gardner (Germany). By illumination of a defined region with incident light of 45° to the normal and measurement of the reflected light intensity at three different angles from the specular reflection (15°/45 110°), a flop index (I) is calculated: f T * — 7* Y1.11

I 2.69 j 0. S 45°

The measurement area was 23 mm in diameter. On each panel, five regions without overlap were measured to give an average.

7. Appearance The homogeneity of the brightness across the painted area of a test panel investigated was evaluated by three individuals. The evaluation of the homogeneity of the brightness can be in principle described as a measurement of the cloudiness of the coating. The evaluation was performed by three individuals as the evaluation was performed with respect to rather small painted areas (15*15 cm), which due to their rather small size could not be measured with the cloud-runner instrument from BYK-Gardner GmbH, which needs larger coated areas for measuring. Nevertheless, the „mottling“ of the metallic shades observed on the test panels can best be understood as an evaluation of the ..cloudiness" in terms of small mottles with sizes in the order of one to few centimeters.

8. Membrane filtration

The membrane filtration employed in the experimental part according to inventively performed step (2) is Tangential Flow Filtration (TFF). As membrane a polyethersulfone membrane (Biomax® membrane; pore size equivalent to 1,000 kDa) is used in combination with a Cogent mScale TFF system (Millipore, Burlington, MA, USA) and a Pellicon XL module. Over time the retentate volume is kept constant by adding appropriate amounts of deionized water. Dialysis is continued until no silver chloride precipitation is visually detected by a haze in a sample of the filtrate in case the metal precursor salt used contains chloride. For such a test 50 pi of a 5 wt.-% AgN0 ₃ solution in dilute nitric acid (pH 1-2) are added to 3 ml of the sample. Typically, a volume of 4,500 ml is needed for the purification of 200 g of the raw mixture and the final retentate with a typical pH value of around 3 is then adjusted to 1 wt.-% NVC with deionized water.

EXAMPLES

The following examples further illustrate the invention but are not to be construed as limiting its scope.

1. Preparation of metal bisphosphonate particles

1.1 Zr-HEDP synthesis A typical deci-molar synthesis is carried out under ambient conditions in a beaker with magnetic stirring: An 18.1 wt.-% stock solution of zirconium oxychloride octahydrate (Zr0CI ₂ -8H ₂ 0) in deionized water is prepared. Separately, a 60 wt.-% stock solution of etidronic acid (C ₂ H ₈ 0 ₇ P ₂ , 1 -hydroxyethane 1 ,1-diphosphonic acid, HEDP) is partially neutralized by the addition of a 5 M NaOH solution in amounts to neutralize 1.74 of the 4 acidic protons in HEDP, which raises the pH value of the solution to around 7. Thus, 6.626 g HEDP solution are mixed with 7.956 g 5 M NaOH solution and subsequently 17.186 g of the aforementioned Zr-solution are added under stirring. The molar ratio of zirconium to HEDP is 0.5:1 and the concentration of HEDP is 0.1 mol/kg. The non-volatile content (NVC) of the reaction mixture is 3.5 wt.-% and the pH value is around 2. Stirring overnight yields a strong translucent gel

(Zr-HEDP gel). The reaction rate can be increased at elevated temperatures. For example, formation of the gel is observed within 2 h at 70 °C.

Fig. 1 shows the results of a small-/wide-angle X-ray scattering (SAXS-WAXS) performed of the Zr-HEDP gel (sample named RNT_95) in comparison to a reaction mixture, wherein no NaOH has been used (RNT_76). In the WAXS domain of RNT_95 three harmonic peaks (gi:g ₂ :g ₃ = 1:2:3) indicate a lamellar stacking with a repeat distance d = 2.14 nm (insert, d = 2 tt/q) whereas two linear regimes with slopes (/(g) ~ g ^* ) x=-2.4 (higher q-range) and x=-1.8 (lower q-range R ² > 0.9996) and a transition around 0.4 nm ¹ {d ~ 15 nm) indicate 2D and 1D objects respectively which have a rough surface. The 1 D objects extend into the micrometer scale since the intensity apparently levels off only very close to the limit of the covered g-range at around 0.0031 nm ¹ (d ~ 2027 nm). On the contrary, the scattering curve of RNT_76 is featureless.

1.2 Zr-HEDP purification 200 g of the obtained Zr-HEDP gel are diluted with deionized water in a weight ratio of 1:1 and the obtained fluid is dialyzed in tangential flow fraction over a polyethersulfone membrane using a Cogent mScale TFF system (Millipore, Burlington, MA, USA) and a Pellicon XL module with a Biomax® membrane (pore size equivalent to 1,000 kDa). Over time the retentate volume is kept constant by adding appropriate amounts of deionized water. Dialysis is continued until no silver chloride precipitation is visually detected by a haze in a sample of the filtrate. For the test 50 pi of a 5 wt.-% AgN0 ₃ solution in dilute nitric acid (pH 1-2) are added to 3 ml of the sample. Typically, a volume of 4,500 ml is needed and the final retentate with a typical pH value of around 3 is adjusted to 1 wt.-% NVC with deionized water. ICP- OES analysis reveals a P:Zr ratio of 2.1 (2,100 ppm Zr, 1,900 ppm P, 360 ppm Na, <10 ppm Cl). The yield is 86% with respect to zirconium and 57% with respect to phosphorous, whereas 17% of sodium are retained by the nanoribbons. The purification step has to be performed in order to remove excess HEDP and NaCI as by-product.

Fig. 2 shows TEM HAADF images of purified Zr-HEDP (b) in comparison to the Zr-HEDP gel without purification (a). As it is evident discrete nanoparticles (nanoribbons) are obtained in case of (b). The purified Zr-HEDP, i.e. the TFF retentate obtained, can be used as such for incorporation into coating compositions or can be submitted to freeze drying first in order to obtain a freeze-dried Zr-HEDP (Zr-HEDP FD) (of. item 1.3, vide infra) or can be neutralized as outlined hereinafter in item 1.4. 1.3 Freeze drying of purified Zr-HEDP

For the freeze-drying process 1-2 cm thick layers of purified Zr-HEDP in petri dishes are placed into a Christ Epsilon 2-4 LSC freeze drier (Christ GmbH, Osterode, Germany) and are frozen at -85 °C before evacuation. Sublimation is performed under 50 Pa with shelf and ice-condenser temperatures of +20 °C and -20 °C respectively. For the final drying/desorption step the shelf temperature is raised to 40 °C and the pressure lowered to 1-10 Pa for approximately 1 h. The obtained powder, i.e. freeze-dried Zr-HEDP (Zr-HEDP FD) can be used for incorporation into coating compositions.

TGA under nitrogen and a heat rate of 10 K/min of the obtained powder Zr-FIEDP FD shows a weight loss of 10 wt.-% below 200 °C, which is attributed to adsorbed water The amount is less than those found in Zr-FIEDP samples that were dried under ambient conditions and in an oven at 40 °C (and thus not under freeze drying conditions) with 14 and 12 wt.-% weight loss respectively.

Fig. 2A shows the results of a small-angle X-ray scattering (SAXS) performed of the diluted Zr-FIEDP gel (as obtained after step (1) as described in item 1.1), of purified Zr-FIEDP in form of an aqueous dispersion (AD1) obtained after step (2) as described in item 1.2 and of an aqueous dispersion of the freeze dried Zr-FIEDP (Zr- FIEDP FD), i.e. of an aqueous dispersion (AD2). 1.4 Amine neutralized purified Zr-HEDP or Zr-HEDP FD

Both Zr-FIEDP and Zr-FIEDP FD dispersions with 1 wt.-% NVC are neutralized with ammonia or amines such as DMEA. Phase behavior and birefringence of samples with pFH values in the range of 7 - 8 reveal liquid crystalline phases with domain sizes in the millimeter range. Contrary to Zr-FIEDP dispersions Zr-FIEDP FD causes some initial haze, which, however, vanishes upon shaking the vial.

1.5 Comparative modified production processes The Zr-FIEDP synthesis according to item 1.1 was varied with regard to the ZnHEDP ratio and the OPFPOH ratio (amount of acidic protons neutralized), respectively, while keeping the other parameters unchanged. With a molar ratio of ZnHEDP = 1:1 only a coarse precipitated material is recovered and no nanoparticles are formed. With excess zirconium (ZnHEDP = >1:1) also an immediate undesired precipitation has as well been observed.

An undesired precipitation also takes place with a OH:POH-ratio of 3:1 and 4:1, respectively. The pH values of the mixtures were measured to be around 5 and 9, respectively. On the other hand, without adding any NaOH, i.e. when not partially neutralizing the HEDP, a clear and low viscous solution is obtained, which, however, does not contain any nanoparticles, let alone nanoribbons as identified by SAXS measurement as illustrated in Fig. 1 (RNT-76, Fig. 1).

In summary, these experiments demonstrate, that aqueous dispersions (AD1) containing suitable nanoparticles (B) for preparing aqueous coating material compositions are only produced within a certain parameter space defined by ZnHEDP stoichiometry and pH value (i.e., OH:POH ratio). This includes the necessity to perform a purification step in order to separate the nanoparticles from the by-product NaCI and excess HEDP.

2. Preparation of pigment pastes Two different commercially available aluminum pigments a. and b. are used (both from Eckart GmbH; Altana), namely a. chromate passivated aluminum flakes STAPA Hydrolux VP 56450 (particle size distribution: D _v (50) = 17 pm; pigment content: 65 ± 2 wt.-%, volatile content: 35 ± 2 wt.-% (organic solvents: mineral spirit, naphtha, 2- butoxyethanol and water), and b. silane sol-gel coated aluminum flakes STAPA Hydrolan 2153 (particle size distribution: D _v (50) = 21-27 pm; pigment content: 65 ± 2 wt.-%, volatile content: 35 ± 2 wt.-% (organic solvents includes 2-propanol),

Pigments a. and b. are used to prepare pigment pastes 1 and 2, respectively, together with PES, deionized water and 2-butoxyethanol (2-BE). PES is a polyester dispersion. The dispersion is produced as described in example, column 16, lines 37-59 of DE 4009858 A1 with the exception that not butanol but 2- butoxyethanol has been used. PES has a NVC pf 60 wt.-%. The glass transition temperature (T _g ) of the polyester is <273 K (estimated). The polyester contained in PES has a M _n of 2 kDa and a M _w of 21 kDa. The polyester has an average particle size of 65 nm. The polyester has functionalities of carboxylate and hydroxyl (OH: meq = 1.25; COO : meq = 0.45), which are titration results and refer to 1 g NVC.

Pigment paste 1: 42.86 g Hydrolux VP 56450 are diluted with 42.86 g deionized water under stirring (600-800 rpm) and subsequently 14.28 g PES (the polyester dispersion described hereinbefore) are added. Stirring is continued for 30 minutes to ensure homogenous dispersion of aluminum flakes. Pigment paste 2:

33.33 g Hydrolan 2153 are diluted with 33.33 g 2-butoxyethanol (2-BE) under stirring (600-800 rpm) and subsequently 33.33 g PES (the polyester dispersion described hereinbefore) are added. Stirring is continued for 30 minutes to ensure homogenous dispersion of aluminum flakes.

The compositions of the pigment pastes are disclosed hereinafter in Table 1 :

Table 1: Pigment pastes 1 and 2

3. Preparation of coating compositions 3.1 Coating compositions are prepared on a 100 gram scale in a beaker under stirring using a four winged blade agitator of 4.5 cm diameter in such a way that a distinct vortex of the fluid is maintained over all addition steps. The starting “virtual” peripheral velocity is 0.83 m/s (350 rpm) and the maximum velocity realized was 2.83 m/s (1,200 rpm).

The coating compositions are prepared as follows: Zr-HEDP is prepared as described in item 1.2, i.e. an aqueous dispersion having a NVC of 1 wt.-% of Zr-HEDP is prepared. As further described in item 1.4 the Zr- HEDP contained in this aqueous dispersion is then neutralized by adding deionized water and together with an aqueous dispersion of DMEA (10 wt.-% in water) in the amounts indicted in the Tables hereinafter until a resulting pH value in the range of 7.5 to 8 is reached. PES (the polyester dispersion described hereinbefore) is added within 2-3 minutes to the aqueous dispersion of DMEA neutralized Zr-HEDP. After a visually homogeneous mixture is achieved the pigment paste is added within 2-3 minutes. After homogeneous appearance is achieved the polymer dispersion PUR or PAC-PUR is added within 2-3 minutes. The pH value of the coating composition is in the range of 7-8. After additional stirring for five minutes the resulting coating compositions are transferred into glass vials and stored for rheological measurement and application respectively. The compositions are stirred in closed vials until the rheological measurement and application, respectively, took place. Zr-HEDP FD is prepared as described in item 1.3, i.e. Zr-HEDP FD is prepared in form of a freeze-dried powder. Zr-HEDP FD is then dispersed in deionized water and an aqueous dispersion of DMEA (10 wt.-% in water) is added for neutralization in the amounts indicted in the Tables hereinafter until a resulting pH value in the range of 7.5 to 8 is reached. PES (the polyester dispersion described hereinbefore) is added within 2-3 minutes to the aqueous dispersion of DMEA neutralized Zr-HEDP FD. After a visually homogeneous mixture is achieved the pigment paste is added within 2-3 minutes. After homogeneous appearance is achieved the polymer dispersion PUR or PAC-PUR is added within 2-3 minutes. The pH value of the coating composition is in the range of 7-8. After additional stirring for five minutes the resulting coating compositions are transferred into glass vials and stored for rheological measurement and application respectively. The compositions are stirred in closed vials until the rheological measurement and application, respectively, took place.

PUR is a polyurethane dispersion. The dispersion is produced as described on page 14, line 13 to page 15, lines 13 of WO 92/15405 A1. PUR has a NVC pf 27 wt.-%. The glass transition temperature (T _g ) of the polyurethane is <273 K (estimated). The polyurethane contained in PUR has a M _n of 14 kDa and a M _w of 51 kDa. The polyurethane has an average particle size of 20 nm. The polyurethane has functionalities of carboxylate and hydroxyl (OH: meq = 0.23; COO : meq = 0.58), which are titration results and refer to 1 g NVC. PAC-PUR is a hybrid polyurethane-polyacrylate dispersion. The dispersion is produced as described in WO 91/15528 A1 (binder dispersion C in item 1.3 of the experimental part of this reference). PAC-PUR has a NVC pf 44 wt.-%. The glass transition temperature (T _g ) of the polyurethane is about 300 K (estimated). The polyurethane-polyacrylate contained in PAC-PUR has a M _n of 7 kDa and a M _w of 42 kDa. The polyurethane-polyacrylate has a particle diameter of 70 nm. The polyurethane-polyacrylate has functionalities of carboxylate and hydroxyl (OH: meq = 1.00; COO : meq = 0.55), which are titration results and refer to 1 g NVC.

In case of individualized comparative coating compositions C1 to C5 neither Zr- HEDP norZr-HEDP FD has been used. Instead, the commercially available product Laponite® RD (BYK, Germany), which is a hectorite, has been employed. For this a Laponite® RD mix has been prepared, which has been in turn used for preparing comparative coating compositions C1 to C5. The Laponite® RD mix is prepared as follows: The preparation in a beaker is performed under high shear rate using a dissolver disk with 5 cm diameter and 1 ,800 rpm (peripheral velocity v = 4.71 m/s). 3 g Laponite® RD are added to 44 g deionized water. Another 3 g of a polypropylene glycol ether (Pluriol® P900, BASF SE, Germany) are added. The dispersion is diluted with 50 g deionized water and stirred for additional 5 minutes before transferring into a vial in order to be used for preparing comparative coating compositions C1 to C5. The Laponite® RD mix thus is composed of 94 wt.-% water, 3 wt.-% Laponite® RD and 3 wt.-% Pluriol® P900 (NVC content of the Laponite® RD mix is 6 wt.-%).

In case of individualized comparative coating compositions CE1 to CE5 (control experiments) neither Zr-HEDP nor Zr-HEDP FD nor Laponite® RD has been used. Instead, simply only deionized water has been employed. 4.2 In the following Tables 2a, 3a, 4a. 5a and 6a a number of exemplary and comparative coating compositions are individualized:

Table 2a: Inventive examples 11 and I2, comparative example C1 as well as control experiment CE1

In case of comparative coating composition C1 a viscosity adjustment has been performed before applying said composition. In total 15.8 g water have been added resulting in a NVC of 26.9 wt.-%. Fig. 3 shows shear thinning rheology of aluminum pigmented basecoat formulations comprising purified Zr-HEDP (“TTF t.q.”), namely 11, or Zr-HEDP FD (“TTF f.d.”), namely 12, as well as hectorite platelets (Laponite® RD), namely C1, in comparison to a control without any additive, namely CE1. While the control behaves like a Newtonian liquid, the hectorite comprising basecoat is a shear thinning liquid with nearly lacking or little hysteresis respectively. On the contrary, both the Zr-HEDP and the Zr-HEDP FD comprising pigmented basecoat formulations 11 and I2 show a distinctly different rheology with basically two subsequent domains with increasing shear rate. The transition can be linked to the macroscopic alignment of domains of the liquid crystalline Zr-HEDP phase which leads to a more compilable flow. That macroscopic order persists under decreasing shear rates.

Table 3a: Inventive examples 13, 14 and 15, comparative example C2 as well as control experiment CE2

In case of coating compositions I4, I5 and CE2 a viscosity adjustment has been performed in each case before applying said composition. In case of 14 and CE2

10.0 g water have been added in each case resulting in a NVC of 29.1 wt.-%. In case of I5 5.0 g water have been added in each case resulting in a NVC of 30.6 wt.- %. Table 4a: Inventive examples 16, 17 and 18, comparative example C3 as well as control experiment CE3

In case of coating compositions I7, I8 and CE3 a viscosity adjustment has been performed in each case before applying said composition. In all cases 20.0 g water have been added resulting in a NVC of 26.7 wt.-% in each case.

Table 5a: Inventive examples 19, 110 and 111, comparative example C4 as well as control experiment CE4

Table 6a: Inventive examples 112, 113 and 114, comparative example C5 as well as control experiment CE5 In case of coating compositions 113, 114 and CE5 a viscosity adjustment has been performed before applying said composition. In cases of 113 and CE5 10.0 g water have been added resulting in a NVC of 29.2 wt.-% (113) and 29.1 wt.-% (CE5) respectively. In case of 1145.0 g water were added (resulting NVC: 30.5 wt.-%). As it has been outlined above in connection with some of the Tables, some coating compositions are diluted with weighed amounts deionized water directly in the spray boost in order to assure proper atomization of the liquid coating composition in a spray application process. 4.3 In the following Tables 2b, 3b, 4b. 5b and 6b a number of exemplary and comparative coating films obtained from the coating compositions individualized in Tables 2a, 3a, 4a, 5a and 6a are disclosed: Table 2b: Compositions of films obtained from 11, I2, C1 and CE1

Table 3b: Compositions of films obtained from I3, I4, I5, C2 and CE2

Table 4b: Compositions of films obtained from 16, 17, 18, C3 and CE3

Table 5b: Compositions of films obtained from 19, 110, 111, C4 and CE4

Table 6b: Compositions of films obtained from 112, 113, 114, C5 and CE5

These coating films result from applying one of the coating compositions displayed in Tables 2a, 3a, 4a, 5a and 6a as agueous basecoats on metallic substrates as part of a multilayer film: steel panels, which had been prior coated and cured with a commercial cathodic electrocoat (E-Coat CG800 from BASF Coatings GmbH), were first cleaned with ethyl acetate in order to remove contaminants. The inventive and non-inventive coating compositions displayed in Tables 2a, 3a, 4a, 5a and 6a were then applied by atomization using a pneumatic paint spray apparatus (SATA Minijet 4400, SATA Kornwestheim, nozzle diameter 1.4 mm) with an air pressure of 1.8 bar in a controlled-climate room as agueous basecoats (23°C; 65% relative humidity). The panels were positioned vertically. Spraying was carried out so as to give a dry film thickness of 15 ± 3 pm. The thickness here was verified by 21 magnetic induction measurements which took place uniformly over the coated area. After application of the basecoats by spraying, flash off takes place in the climatized room for 10 minutes before the coated panels are placed into a convection oven and dried at 80 °C for 10 minutes. 5. Investigation of properties of the inventive and non-inventive coating compositions and of coatings obtained therefrom 5.1 In order to determine and evaluate the viewing-angle-dependent lightness (flop) and the appearance a commercial automotive two-component clearcoat as topcoat has been applied onto some of the dried basecoats by pneumatic spray application. The solvent-based 2K clearcoat system consists of a hydroxyl-functional polyacrylate and a polyisocyanate in a hydrocarbon-dominated solvent mixture. The two components were premixed in a glass beaker by stirring, and the coating was atomized with 1.8 bar of air in the same spraying booth used for the application of the basecoat. Spray application was carried out so as to achieve a dry film thickness of 40 ± 4 pm, which was measured on the cured coatings, as described above for the cured basecoats. Immediately after spray application, the film was flashed off for 20 minutes and then placed into a convection oven at 140°C for 20 minutes for curing.

Both the viewing-angle-dependent lightness (flop) and the appearance have been measured by making use of the respective resulting multicoats including the clearcoat as topcoat as described above.

5.2 Properties of coatings prepared from pigment paste 1 (Hydrolux) and PUR Table 7 gives an overview of the measured flop values and of the evaluation of the appearance of coatings obtained from compositions I4, I5, C2 and CE2.

Table 7: Properties of films obtained from 14, 15, C2 and CE2 It is evident from Table 7 that both an excellent flop index and an excellent appearance at a high solids-content (in the range of from 29.0 to 30.4 wt.-%) is only achieved with exemplary inventive coating compositions I4 and I5 with example I5 giving the best results. An excellent flop index is also achieved by using Laponite® containing comparative example C2; however, at the expense of an only low solids content and poorer appearance.

5.3 Properties of coatings prepared from pigment paste 2 (Hydrolan) and PAC-PUR Table 8 gives an overview of the measured flop values and of the evaluation of the appearance of coatings obtained from compositions 112, 114, C5 and CE5.

Table 8: Properties of films obtained from 114, C5 and CE5

It is evident from Table 10 that both an excellent flop index and an excellent appearance at a high solids-content (30.4 wt.-%) is only achieved with exemplary inventive coating composition 114. An excellent flop index is also achieved by using Laponite® containing comparative example C5; however, at the expense of an only low solids content and poorer appearance.