Anionic polyurethanes

Abstract

Anionic polyurethanes are produced by reacting an aliphatic dihydroxy compound, which has an aliphatic substituent with at least 10 carbon atoms, with a polyisocyanate to form a prepolymer with an NCO end group, and for the purpose of chain lengthening, by reacting the prepolymer with an aliphatic diol, which carries an acid group capable of salt formation, and by converting the said acid group totally or partially into a salt. In the production of the polyurethane, polyether compounds with at least one OH group, particularly polyalkylene glycols such as polyethylene glycol, are used additionally. The resulting anionic polyurethanes are particularly suitable as a sizing agent for paper and permit sizing in the acid pH region as well; the sizing agent is furthermore less sensitive to polyvalent cations such as calcium and aluminum ions.

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