AQUEOUS POLYURETHANE RESIN FOR COATING HAVING EXCELLENT WATER RESISTANCE, PREPARATION THEREOF AND PRODUCT THEREOF

PURPOSE: Provided is an environmental-friendly aqueous polyurethane resin for coating, which has excellent water resistance, bending resistance and water dispersion stability and shows excellent physical properties when forming a film. CONSTITUTION: The aqueous polyurethane resin for coating is prepared by the method comprising the steps of: reacting a polyol, diisocyanate, and diol having a hydrophilic group, diamine having a hydrophilic group or a mixture thereof, in the presence of a catalyst to provide a prepolymer; neutralizing the prepolymer with a neutralizer; adding thereto water as a dispersion medium to form water dispersion; adding a chain extender to the water dispersion to perform chain extension, thereby providing polyurethane water dispersion. In the method, the NCO/OH ratio, i.e., (mole numbers of diisocyanate)/(mole numbers of polyol+mole numbers of diol having a hydrophilic group) is 1.1-3.0, and the content of the diol having a hydrophilic group, diamine having a hydrophilic group or a mixture thereof is 1-10 wt% based on the solid content of the final aqueous polyurethane polymer.