Polyurethanes which are dispersible or soluble in water and a process for their preparation

A water-dispersible or water-soluble polyurethane containing structural units in end positions or side chains of the formula

• --O--X--R
• wherein
• X represents a polyalkylene oxide chain having from 5 to 90 chain members, at least about 40% of which are ethylene oxide units of the formula --CH.sub.2 --CH.sub.2 --O--, and
• R represents a monovalent hydrocarbon group having from 3 to 18 carbon atoms and containing at least one sulfonate ion of the formula --SO.sub.3.sup..crclbar.
• in a sufficient quantity to contribute about 0.5 to 20% by weight of ethylene oxide units, based on the weight of the polyurethane, to the polyurethane and about 0.1 to 25 milliequivalents of sulphonate ions per 100 g of polyurethane to the polyurethane.

A process for the preparation of a water-dispersible or water-soluble polyurethane comprising reacting

• (a) an organic diisocyanate having a molecular weight between about 112 and 1000,
• (b) an organic compound having a molecular weight of between about 60 and 6000 and having at least two isocyanate-reactive end groups, and
• (c) a hydrophilic compound responsible for the dispersibility or solubility of the resulting polyurethane comprising a member selected from the group consisting of monoisocyanates, diisocyanates, compounds having at least one isocyanate-reactive group and compounds having at least two isocyanate-reactive groups, said hydrophilic compound having structural units of the formula
• --O--X--R
• wherein
• X represents a polyalkylene oxide chain having from 5 to 90 chain members, at least about 40% of which are ethylene oxide units, and
• R represents a monovalent hydrocarbon group having from 3 to 18 carbon atoms and containing at least one sulphonate --SO.sub.3.sup..crclbar. group
• which are present in a sufficient quantity to contribute to the resulting polyurethane about 0.5 to 20% by weight of ethylene oxide units, based on the weight of the resulting polyurethane, and about 0.1 to 25 milliequivalents of sulfonate ions per 100 g of resulting polyurethane, said hydrophilic groups being attached to the resulting polyurethane in end positions or side chains.