Nigrosine dyes and process for preparing same

A nigrosine dye represented by the formula D--R).sub.n wherein D is a nigrosine dye moiety of the water insoluble nigrosine base C.I. 50415:1 (C.I. Solvent Black 7), n is a number from 1 to 4, and each R is a hydrocarbon radical individually selected from the group consisting of alkyl of 3 to 8 carbon atoms, alkenyl of 3 to 18 carbon atoms, aralkyl which is optionally ring substituted with an alkyl substituent of 1 to 8 carbon atoms, and aralkenyl which is optionally ring substituted with an alkyl substituent of 1 to 8 carbon atoms, and which constitutes the reaction product prepared by reacting a precursor nigrosine dye constituted by the water insoluble nigrosine base C.I. 50415:1 (C.I. Solvent Black 7) and containing at least one active hydrogen atom correspondingly attached to at least one nitrogen atom in the precursor dye and represented by the formula D--H).sub.n wherein D and n are the same as defined above, and each H is a replaceable hydrogen atom correspondingly attached to a nitrogen atom in the precursor dye, with at least one corresponding hydrocarbon halide represented by the formula RX wherein R is the same as defined above and X is a halogen atom, in an organic solvent in the presence of an acid binding agent selected from the group consisting of alkali metal compounds and alkaline earth metal compounds, said reaction product dye being recoverable in the form of crushable solid particles of high purity and having storage stability, solubility in organic solvents and compatibility with organic solvents and toner resins, said storage stability constituting stability against precipitation separation of said reaction product dye from an organic solvent solution thereof with the lapse of time.

A process for preparing a nigrosine dye represented by the formula D--R).sub.n wherein D is a nigrosine dye moiety of the water insoluble nigrosine base C.I. 50415:1 (C.I. Solvent Black 7), n is a number from 1 to 4, and each R is a hydrocarbon radical individually selected from the group consisting of alkyl of 3 to 18 carbon atoms, alkenyl of 3 to 18 carbon atoms, aralkyl which is optionally ring substituted with an alkyl substituent of 1 to 8 carbon atoms, and aralkenyl which is optionally ring substituted with an alkyl substituent of 1 to 8 carbon atoms, which comprises reaction a precursor nigrosine dye constituted by the water insoluble nigrosine base C.I. 50415:1 (C.I. Solvent Black 7) and containing at least one active hydrogen atom correspondingly attached to at least one nitrogen atom in the precursor dye and represented by the formula D--H).sub.n wherein D and n are the same as defined above, and each H is a replaceable hydrogen atom correspondingly attached to a nitrogen atom in the precursor dye, with at least one corresponding hydrocarbon halide represented by the formula RX wherein R is the same as defined above and X is a halogen atom, in an organic solvent in the presence of an acid-binding agent selected from the group consisting of alkali metal compounds and alkaline earth metal compounds, and recovering as produced product the corresponding dye represented by said formula D--R).sub.n from the resulting reaction mixture, in the form of crushable solid particles of high purity and having storage stability, solubility in organic solvents and compatibility with organic solvents and toner resins, said storage stability constituting stability against precipitation separation of said produced product dye from an organic solvent solution thereof with the lapse of time.