Patent ID: 9005714
Filing Date: 2015-04-14
Classification: B05D

Abstract:
1. A process for the production of a dark-color multi-layer coating, comprising the successive steps: (1) applying an NIR-opaque coating layer A′ from a solventborne pigmented coating composition A to a substrate, (2) applying a coating layer B′ from a solventborne pigmented coating composition B onto the substrate provided with coating layer A′, (3) subjecting the coated substrate obtained in step (2) to a drying step, (4) applying a clear coat layer from a clear coat composition onto the coated substrate obtained in step (3), and (5) thermally curing the coating layers applied in steps (1), (2), and (4) simultaneously; wherein both coating compositions A and B comprise resin solids consisting of binder solids plus crosslinker solids comprising melamine-formaldehyde resin crosslinker, wherein coating composition A comprises at least one component selected from the group consisting of (i) (a) >5 to 20 wt. % of cellulose ester binder and up to 10 wt. % of NAD binder or (b) 10 to 100 wt. % of NAD binder and up to 5 wt. % of cellulose ester binder, the wt. % in each case being based on the weight of the binder solids of coating composition A, (ii) 0.2 to 1.5 wt. %, based on the weight of the resin solids of coating composition A, of sheet silicate, (iii) 0.5 to 2 wt. %, based on the weight of the resin solids of coating composition A, of fumed silica, (iv) 0.5 to 2.5 wt. %, based on the weight of the resin solids of coating composition A, of urea SCA and (v) 0.5 to 8 wt. %, based on the weight of the resin solids of coating composition A, of polyolefine wax, wherein coating composition B comprises at least one component selected from the group consisting of (i′) (a) >5 to 20 wt. % of cellulose ester binder and up to 10 wt.% of NAD binder or (b) 10 to 100 wt. % of NAD binder and up to 5 wt. % of cellulose ester binder, the wt. % in each case being based on the weight of the binder solids of coating composition B, (ii′) 0.2 to 1.5 wt. %, based on the weight of the resin solids of coating composition B, of sheet silicate, (iii′) 0.5 to 2 wt. %, based on the weight of the resin solids of coating composition B, of fumed silica, (iv′) 0.5 to 2.5 wt. %, based on the weight of the resin solids of coating composition B, of urea SCA and (v′) 0.5 to 8 wt. %, based on the weight of the resin solids of coating composition B, of polyolefine wax, wherein the pigment content of coating composition A consists 90 to 100 wt. % of at least one aluminum flake pigment and 0 to 10 wt. % of at least one further pigment, which is selected in such a way that NIR-opaque coating layer A′ exhibits an NIR reflection of at least 48% over the entire NIR wavelength range of 780 to 2100 nm, wherein the pigment content of coating composition B consists 50 to 100 wt. % of at least one black pigment with low MR absorption and 0 to 50 wt. % of at least one further pigment, which is selected in such a way that coating layer B′ exhibits an NIR reflection of at least 33% over the entire NIR wavelength range of 780 to 2100 nm, if it were applied and dried or cured on an NIR-opaque coating layer pigmented exclusively with 100 to 1000 nm thick aluminum flake pigment, and that the dark-color multi-layer coating exhibits a brightness L* (according to CIEL*a*b*, DIN 6174), measured at an illumination angle of 45 degrees to the perpendicular and an observation angle of 45 degrees to the specular, of at most 10 units.