Method of improving the appearance of coated articles having both vertical and horizontal surfaces, and coating compositions for use therein

#The invention relates to curable coating compositions containing rheology modifiers and methods of using the same. More particularly, the invention relates to methods of coating articles, including a preferred method for coating articles having both vertically and horizontally orientated surfaces using coating compositions containing a particular rheology control agent.

#Composite color-plus-clear coatings are widely utilized in the coatings art. They are particularly desirable where exceptional gloss, depth of color, distinctness of image, and/or special metallic effects are required.

#As used herein, the term “composite color-plus-clear” relates to composite coating systems requiring the application of a first coating, typically a colored basecoat coating, followed by the application of a second coating, generally a clearcoat, over the noncured or “wet” first coating. The applied first and second coatings are then cured. Thus, such systems are often described as “wet on wet” or “two-coat/one bake”. Drying processes that fall short of complete cure may be used between the application of the coatings.

#Carbamate functional acrylic/melamine based clearcoat compositions were generally prepared according to Example 2 of U.S. Pat. No. 5,726,246. Components (bi) and (bii) were added per Table 1. The levels of carbamate functional acrylic in all coatings were adjusted so as to be equivalent in view of any additional carbamate functional acrylic resin incorporated with the addition of component (bii).

#TABLE 1 Component % fixed Clearcoat Composition vehicle A B C D E (bi)1 2.39 0.00 2.39 0.00 3.58 (bii)2 0.00 2.00 0.57 3.00 0.00 1A 1:1 blend of Aerosil ® R805, (a fumed silicas commerically available from Degussa of Frankfurt, Germany) and Cabosilc ® TS610, (a fumed silica commercially available from Cabot Alpharetta, GA) 2Setalux ® 10-9701, the reaction product of benzylamine and hexamethylene diisocyanate prepared in the presence of carbamate functional acrylic of Preparation 1 of U.S. Pat. No. 5,726,246, and commercially available from Akzo Nobel Resins of Louisville, KY.

#Test panels for evaluation of sag resistance were prepared by phosphating a 4×18 inch steel panel having 17¼ inch holes arrayed down the center of the panel from top to bottom with a commerically available phosphate treatment. The panels were electrocoated with U32AD310 electrocoat, commercially available from BASF Corporation of Southfield, Mich. Clearcoats A-E were then spray applied in a wedge format such that the greatest film build was at the bottom of the panel with the film build diminishing to the minimum film at the top of the panel. During application of the coating, the panel were placed at an angle of approximately 90° relative to the surface of the earth. Immediately after application of the coatings, the coated panels were positioned on their sides. The panels were flashed for two minutes while in this position and then placed in the same position in a 285° F. oven for 23 minutes.