SUBSTRATE MARKING SYSTEM

A marked substrate including a solid substrate surface such as, for example, a road surface having disposed thereon a first coating including a pigment and a first binder polymer, the first coating having a dry film thickness of from 10 microns to 5000 microns; the first coating having disposed thereon, a clear second coating including from 75% to 100%, by weight based on the weight of the clear coating, nanosilica and from 0% to 25%, by weight based on the weight of the clear coating, second binder polymer; the clear second coating having a dry film thickness of from 1 to 10 microns is provided. A method for providing the marked substrate is also provided.

Providing and Evaluating a Marked Substrate

Formation of First Aqueous Coating Composition

The following ingredients (in g) were added in order with moderate shear mixing:

The first binder polymer was an emulsion polymer having a DSC Tg of 45° C. The first aqueous coating composition had a volume solids of 58%, weight solids of 74%, an ICI viscosity of 3.4 poise, and a pH of 10.

Formation of Second Aqueous Coating Composition

The following ingredients (in g) were added in order with moderate shear mixing:

The first aqueous coating composition was drawndown to a wet film thickness of 300 microns and, when dried prior to applying the second coating composition, dried for 7 days at ambient temperature to a dry film thickness of 180-200 microns. The second aqueous coating composition was spray-applied to the first coating at a wet film thickness of 15 g/m2. Alternate aqueous unmodified silica dispersions were substituted at the same solids level.

TABLE 1.1Evaluation of appearance of marked substrates using unmodifiedsilica dispersions of varying particle size of the unmodified silicadispersion in the second coating compositionY reflectance valueParticle size9153055(nm)Application typeWet on wet79.980.98278.4Wet on dry82.382.281.980.1

TABLE 1.2Evaluation of black heel marking resistance of marked substratesusing various unmodified silica dispersions of varying particle size in thesecond coating compositionRating (0 the worst-10 the best)SilicaLEVASIL ™LEVASIL ™LEVASIL ™LEVASIL ™KLEBOSOL ™KLEBOSOL ™DispersionNone3002001005030R1230R50Application typeWet on dry1888666Wet on wet256245LEVASIL ™ is a product of Akzo Nobel N.V.

Marked substrates of the invention exhibit superior dirt resistance as measured by the black heel marking test relative to a comparative example on the same solid substrate having disposed thereon only the same first coating composition.

Providing a Marked Substrate

Formation of First Aqueous Coating Composition

The following ingredients (in g) were added in order with moderate shear mixing:

The first binder polymer was an emulsion polymer having a DSC Tg of 45° C. The first aqueous coating composition had a volume solids of 58%, weight solids of 74%, an ICI viscosity of 3.4 poise, and a pH of 10.

Formation of Second Aqueous Coating Composition

The following ingredients (in g) were added in order with moderate shear mixing:

The first aqueous coating composition was drawndown to a wet film thickness of 300 microns and, when dried prior to applying the second coating composition, dried for 7 days at ambient temperature to a dry film thickness of 180-200 microns. The second aqueous coating composition was spray-applied to the first coating.

TABLE 2.1Evaluation of black heel marking resistance and appearance ofmarked substrates using various unmodified silica dispersionsof varying particle size in the second coating compositionParticle size of unmodified colloidal silica(nm) in second coating compositionSupplier 1Supplier 2None91530551250Black heel markVisual ratingWet on wet—256245Wet on dry1888666White reflectanceWet on wet—79.980.98278.479.580.4Wet on dry7382.382.281.980.181.982.9

Marked substrates of the invention exhibit superior dirt resistance as measured by the black heel marking test and the dirt (red iron oxide) resistance test relative to a comparative example on the same solid substrate having disposed thereon only the same first coating composition.