| 摘要 |
The present invention relates to a novel process for the preparation of aqueous dispersions or solutions of polyurethanes in which oligourethanes which contain terminal isocyanate groups and have been modified by incorporated ionic groups and/or incorporated nonionic-hydrophilic groups and/or containing external emulsifiers, are dispersed and/or dissolved in water, simultaneously or subsequently converted into an oligourethane containing terminal amino groups by means of hydrazine or polyamines having a molecular weight in the range from 60 to 500, and the resultant oligourethane containing terminal amino groups which is dispersed or dissolved in water is chain-extended in the aqueous phase by means of difunctional or polyfunctional chain extenders which react with amino groups by an addition reaction, and to the use of the dispersions or solutions obtained in this way for the production of coatings on any desired flexible or nonflexible substrates.
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