METHOD OF FORMING MULTI-LAYER COATING FILMS ON AUTOMOBILE BODIES WITHOUT A PRIMER BAKE

摘要

This invention relates to a method for forming a multi-layer coating, comprising sequentially applying a primer surfacer, a basecoat, and a clear coat composition on an automotive substrate in a wet-on-wet-on-wet manner, and simultaneously curing the applied three layers together in a single baking step, wherein the primer surfacer comprises: a film forming binder, a volatile organic liquid carrier, and pigment(s); and the binder contains about: (a) about 30 to 80% by weight, based on the weight of the binder, of a hydroxyl functional polyester resin; (b) about 10 to 30% by weight, based on the weight of the binder, of a crosslinking agent selected from the group consisting of a melamine resin, a blocked polyisocyanate resin, or a mixture thereof; (c) about 10 to 40% by weight, based on the weight of the binder, of a dispersed graft polymer comprising a non-crosslinked core of acrylic polymer which is substantially non-soluble in non-polar organic solvent and, grafted to the core, one end of an acrylic stabilizer in the form of a macromonomer, said acrylic stabilizer being soluble in a non-polar organic solvent; wherein the composition is, preferably, essentially free of crosslinked nonaqueous dispersion resin particles or crosslinked microgel resin particles or both, and the composition also contains at least one non-polar organic solvent at the time of application. The resulting multi-layered coating film has excellent aesthetic appearance, chipping resistance, sag resistance, and film build even when formed in a three wet layered application method.