Abstract: Monoazo dyestuffs of the formula ##STR1## wherein R.sub.1 = hydrogen, alkyl, cycloalkyl, aralkyl or aryl, R.sub.2 = sulphoalkyl, sulfoaryl, sulphoalkylaryl or sulphatoalkyl, R.sub.3 = alkyl, aryl, carboxy, carbonamide or carboxylic acid ester, R.sub.4 = hydrogen, alkyl, cycloalkyl, aryl, aralkyl, or the radical of a heterocyclic compound, X = hydrogen, halogen, nitrile, alkyl, alkoxy, trifluoromethyl, nitro, carbonamide or carboxylic ester and Y = hydrogen, halogen, alkoxy or acylamino. The dyestuffs are useful for dyeing natural and synthetic fiber materials.

Abstract: A process for dyeing polyurethane plastics is disclosed in which an azo dyestuff derived from an indole or 5-aminopyrazole coupling component and containing at least one group having an active hydrogen atom, e.g. hydroxyl aor amino, is introduced during the reaction forming the polyurethane whereby the dyestuff is bonded to the polyurethane by a covalent bond resulting from reaction of the active hydrogen on the dyestuff with a polyurethane reaction component, e.g. polyisocyanate. The dyed polyurethanes produced by this process having a very high level of fastness, e.g. fastness to bleeding upon overcoating.