| 摘要 |
Preparing a blocked polyurethane prepolymer dispersion comprises reacting at least a polyisocyanate (100 equivalent.%) with thermally cleaved blocking agent (50-90 equivalent.%), a hydrophilizing agent such as monohydroxycarbonic acid (5-45 equivalent.%) and polyhydroxycarbonic acid (0-25 equivalent.%) and di- or polyfunctional chain extension component (0-15 equivalent.%) to give blocked polyurethane prepolymer; dispersing the polyurethane prepolymer solution in water; and distillatively removing the organic solvent completely during the dispersion. Preparation of a dispersion of blocked polyurethane prepolymer comprises preparing the blocked polyurethane prepolymer by reacting at least a polyisocyanate (100 equivalent.%) (a) with thermally cleaved blocking agent (b) (50-90 equivalent.%, based on the isocyanate reactive group), monohydroxycarbonic acid (c) (5-45 equivalent.%, based on the isocyanate reactive group) as a hydrophilizing agent, polyhydroxycarbonic acid (d) (0-25 equivalent.%, based on the isocyanate reactive group) as a hydrophilizing agent and di- or polyfunctional chain extension component (e) (0-15 equivalent.%, based on the isocyanate reactive group) with a molecular weight of 32-350 g/mol, where when partially water miscible, oppositely inert isocyanate group is used an organic solvent with a boiling point of less than 120[deg]C (1013 mbar) is formed and the quantity of isocyanate group is selected such that the reaction solution contains 70-98 wt.% of polyurethane prepolymer after the complete reaction; dispersing the polyurethane prepolymer solution in water, where the carbonic acid group is deprotonated with a base before, during or after the dispersion; and distillatively removing the organic solvent completely during the dispersion. Independent claims are included for: (1) a dispersion of blocked polyurethane prepolymer obtained from the process; and (2) a substrate that is coated with the dispersion. |
