| 摘要 |
A hydrazine-free aqueous polyurethane dispersion, a method for preparing the polyurethane dispersion, a coating composition containing the polyurethane dispersion, and a substrate coated with the composition are provided to increase the fraction of hard segment, to improve storage stability and to enhance the chemical resistance and water fastness of the coating. A polyurethane dispersion comprises (a) at least one polyisocyanate; (b) at least one polyol having an average molecular weight Mn of 500-6,000 g/mol; (c) at least one polyol having an average molecular weight Mn of 62-500 g/mol; (d) at least one compound containing an ionic group or a group capable of forming an ionic group; (e) at least one polyamine an average molecular weight Mn less than 500 g/mol; (f) optionally at least one monoalcohol having an average molecular weight Mn of 32-145 g/mol; and (g) optionally at least one monoamine having an average molecular weight Mn less than 147 g/mol. The ratio of (f) and/or (g) is 0.4-1.26 wt%, the ratio of (c) is 5.5-22 wt%, and the hard segment fraction of the polyurethane dispersion is 55-85 wt% based on the weight of the resin of a polyurethane dispersion.
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