Patents

Nippon Paint patents clearcoat for automobiles

August 15, 2012

U.S. 8,138,258 B2
Nippon Paint Co., Ltd. has been granted a patent for a clear coating composition for an automobile comprised of a hydroxyl group-containing acrylic resin and a polyfunctional isocyanate compound, wherein: the hydroxyl group-containing acrylic resin is a hydroxyl group-containing acrylic resin obtained by using hydroxyalkyl (meth) acrylate having a hydroxyalkyl group with 4 to 9 carbon atoms as a monomer; at least 60% mass of the total amount of the polyfunctional isocyanate compound is an isocyanate compound having an isocyanurate structure; and the clear coating composition is prepared such that the clear coating composition includes 25% to 50% mass  of a soft segment part with respect to a total solid content of the hydroxyl group-containing acrylic resin and the polyfunctional isocyanate compound, a ratio of a soft segment part derived from a lactone-containing monomer with respect to the total solid content of the hydroxyl group-containing acrylic resin and the polyfunctional isocyanate compound is not more than 4.5% mass, a content ratio of the soft segment part in the hydroxyl-group containing acrylic resin is 7% to 30% mass  with respect to the solid content of the hydroxyl group-containing acrylic resin, a content ratio of the soft segment part in the polyfunctional isocyanate compound is not greater than 60% mass with respect to the solid content of the polyfunctional isocyanate compound, and that a dynamic glass transition temperature of a cured coating film obtained from the clear coating composition is within a range of 30˚ to 60° C, the soft segment part being represented by the formula  —(CH2)n—  (1) wherein n represents an integer of 4 or more, and the soft segment part being present in a main chain or in a cross-linking chain in the clear coating composition.