Process For Producing Multi-Layer Coatings In Light Metallic Color Shades

A method for reducing UV transmission through a multi-layer light metallic color shade coating system wherein the multi-layer coating system consists essentially of:

• (i) an electrocoat primer layer adhered directly to a substrate;
• (ii) a first basecoat layer, comprising a blend of an unmodified water-borne metallic basecoat with an admixture component, adhered to the electrocoat primer;
• (iii) a second basecoat layer, comprising the unmodified water-borne metallic basecoat, adhered to the first basecoat layer, wherein the total thickness of said first basecoat layer plus said second base coat layer is from 10 μm to 30 μm, and
• (iv) a clear topcoat layer adhered to the second basecoat layer, wherein the method comprises incorporating into said second metallic basecoat layer a ratio by weight of pigment content to resin solids content of 0.3:1 to 0.45:1, wherein the pigment content consists essentially of (a) from 90% to 100% by weight of at least one non-leafing aluminum pigment with a platelet thickness of over 100 nm to 500 nm, and wherein at least 50% by weight of said non-leafing aluminum pigment(s) are selected from the group consisting of non-leafing aluminum pigments passivated by chromating, non-leafing aluminum pigments coated with a silicon-oxygen network, and combinations thereof, and (b) from 0% to 10% by weight of at least one other pigment that is different from aluminum pigments, and the pigment(s) different from aluminum pigments are selected to yield a brightness L* of the multi-layer light metallic color shade coating system (according to CIEL*a*b*, DIN 6174), of at least 80 units measured at an illumination angle of 45 degrees to the perpendicular and an observation angle of 15 degrees to the specular, whereby the UV transmission through the multi-layer coating system from the clear topcoat layer to the electrocoat primer layer is less than 0.1% in the wavelength range from 290 to 380 nm and less than 0.5% in the wavelength range from 380 to 400 nm.

An improved multi-layer light metallic color shade coating system for a substrate wherein the multi-layer coating system consists essentially of:

• (i) an electrocoat primer layer adhered directly to the substrate;
• (ii) a first basecoat layer comprising a blend of an unmodified water-borne metallic basecoat with an admixture component, adhered to the electrocoat primer;
• (iii) a second basecoat layer comprising the unmodified water-borne metallic basecoat adhered to the first basecoat layer, wherein the total thickness of said first basecoat layer plus said second base coat layer is from 10 μm to 30 μm, and
• (iv) a clear topcoat layer adhered to the second unmodified basecoat layer,
• wherein the improvement comprises incorporating into the second metallic basecoat layer a ratio by weight of pigment content to resin solids content of 0.3:1 to 0.45:1, wherein the pigment content consists essentially of (a) from 90% to 100% by weight of at least one non-leafing aluminum pigment with a platelet thickness of over 100 nm to 500 nm, and wherein at least 50% by weight of said non-leafing aluminum pigment(s) are selected from the group consisting of non-leafing aluminum pigments passivated by chromating, non-leafing aluminum pigments coated with a silicon-oxygen network and combinations thereof, and (b) from 0% to 10% by weight of at least one other pigment that is different from aluminum pigments, and the pigment(s) different from aluminum pigments are selected to yield a brightness L* of the multi-layer light metallic color shade coating system (according to CIEL*a*b*, DIN 6174), of at least 80 units measured at an illumination angle of 45 degrees to the perpendicular and an observation angle of 15 degrees to the specular, whereby UV transmission through the multi-layer coating system from the clear topcoat layer to the electrocoat primer layer is less than 0.1% in the wavelength range from 290 to 380 nm and less than 0.5% in the wavelength range from 380 to 400 nm.