| abstract |
Aqueous ink for ink jet printing comprising dispersed pigments and a carboxylated polyurethane having blocked isocyanate groups obtained by a process comprising the following steps: a. reacting i) at least one aliphatic or cycloaliphatic diisocyanate, ii) at least one diol having a molecular weight of 500 to 5000 daltons selected from the group consisting of polyether diols, polyester diols, polycarbonate diols, polyesteramide diols, polythioether diols, polyacetal diols, polyvinyl diols and polysiloxane diols, iii) at least one diol having a carboxylic acid group, the molar ratio between the -NCO groups of the diisocyanate and the OH groups of the diols is between 1, 2 and 2, to form an -NCO-terminated intermediate; b. reacting the -NCO-terminated intermediate with one or more -NCO blocking agents selected from the group consisting of triazoles, pyrazoles, oximes, and lactams, and optionally with a monofunctional alcohol or with a primary or secondary monoamine or one of their mixtures, to obtain a carboxylated polyurethane having blocked isocyanate groups; c. optionally disperse the carboxylated polyurethane having blocked isocyanate groups in water at a concentration between 15 and 60% by weight, |