| 摘要 |
Aqueous polymer dispersion containing a water-dispersed polyurethane polymer and a vinyl (preferably acrylic) polymer in a weight ratio of from 30/70 to 5/95, wherein said polyurethane polymer is the reaction product of:A) an isocyanate-terminated polyurethane prepolymer having an acid value of >=44 mg KOH/g of prepolymer (solids) and formed from reactants comprising an organic polyisocyanate component and an organic poly(isocyanate-reactive) group) component in which the isocyanate-reactive groups are selected from -OH and optionally one or more of -NH2, -NH-, and -SH (usually a polyol), whereini) at least 70 weight % of said polyisocyanate component is constituted by at least one aliphatic polyisocyanate,ii) said poly(isocyanate-reactive group) component includes at least one acid-bearing poly(isocyanate-reactive group) compound for providing anionic groups which provide or contribute to water-dispersibility,iii) the reactants are used in amounts corresponding to a ratio of isocyanate groups to isocyanate-reactive groups (usually hydroxyl) within the range of 1.4/1 to 2.9/1; andB) an active hydrogen chain-extending compound(s).
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