Aqueous dispersions of polyurethanes from oligo urethanes having unsaturated terminal groups

Claim 1

A process for producing stable aqueous dispersions of polyurethanes containing in the macromolecule hydrophile ionic groups, as "internal" surfactants, both of anionic and cationic nature, which are present in quantities equal to 10-60 meq/100 g of dry polyurethane, said process consisting of the following operating steps: (a) a mixture consisting of a diol containing ionizable groups, i.e. groups which can be turned into hydrophile anionic or cationic groups, and of an essentially linear macroglycol, having a molecular weight ranging between 500 and 5000, of at least one of the polyolpolyether and polyol-polyester types, is reacted at a temperature not higher than 100° C., with an excess of a diisocyanate (--NCO/--OH ratio in equivalents between 1.2 and 2), thereby obtaining a prepolymer containing free isocyanic groups; (b) the polyisocyanic prepolymer is then converted to an oligourethane containing vinylic unsaturated terminal groups, by reaction with a compound containing hydroxyl radicals, which are reactive towards the isocyanic group, and having the general formula: ##STR2## where R is H or CH 2 , X is a hydroxyalkyl radical; (c) the obtained oligourethane is subjected to salification treatments in order to convert the ionizable groups into hydrophile cations or anions, respectively of quaternary ammonium kind or of carboxylic, sulphonic, phosphonic group kind; (d) the oligourethane containing the hydrophile cationic and anionic groups, is subjected to polymerization treatment of the terminal unsaturated groups, in an aqueous dispersion, in the presence of radicalic catalysts at a temperature not higher than 100° C., so as to obtain an aqueous dispersion of polyurethane having a pre-established reticulation degree, that can be regulated by means of a possible addition of comonomers in the polymerization step.