BigPatents India

An aqueous polyurethane resin composition capable of forming a film excellent in corrosion resistance, alkali resistance, paint adhesion and lubricity on a zinciferous metal-plated steel strip comprises (a) a polyurethane resin comprising a polyester skeleton moiety and a polyether skeleton moiety and having a tensile strength at break of 3.92 kN/cm2 or more, and a tensile elongation at break of 50% or less, determined in accordance with JIS K 7113 and a glass transition temperature (Tg) of 80 to 150°C, determined in accordance with JIS K 7121, (b) polyolefin resin fine particles having a melting point of 70 to 160°C and a particle size of 0.5 to 5 µm, and (c) a colloidal silica having a particle size of 5 to 50 nm, wherein, based on the total solid mass of these components a, b and c, the solid content ratio of the component (a) is from 50 to 93 mass%, the solid content of the component (b) is from 2 to 20 mass%, and the solid content of the component (c) is from 5 to 40 mass%.