Ciba-geigy Corporation

Peter E Eugster

Stefan Koller

Peter Liechti

Antoine Clement

Suresh C Agarwal

Hans-Jorg Angliker

Kurt Meyer

Helga Kaiser

Mixtures comprising 75 to 99% by weight of a dye of formula ##STR1## wherein X is hydrogen, chlorine, bromine or methyl, and

Dye mixtures

There is described a novel modification of the dye of the formula ##STR1## which is characterized by the data given in claim 1. This novel modification is suitable in particular for dyeing wound packages of polyester materials under HT conditions, materials dyed in a golden-yellow shade being obtained.

Dye stable to dyeing, processes for producing it, and its use for dyeing

By the slow stepwise heating up of an aqueous suspension of the crystallographically amorphous dye of the formula ##STR1## which dye is unstable to dyeing, to a temperature of 90.degree.-100.degree. C. with a halting point at 40.degree.-60.degree. C., this dye can be transformed completely into the crystalline .alpha.-modification. The novel dye modification can be easily converted, without increase of viscosity, into thinly liquid formulations which are readily pourable, which form no sediment, and which are excellently suitable for producing printing pastes, for example for printing polyester fabric.

Disperse dye stable to dyeing, and its use for dyeing and printing

By suspension of the melt of the known crystallographically amorphous dye of the formula ##STR1## which is unstable to dyeing, in water at a temperature of 90.degree. to 130.degree. C., this dye can be caused to crystallize. There is obtained a crystalline granulate in which the dye is completely in the novel .epsilon.-modification. The novel dye modification is stable in dispersion under dyeing conditions, and has no tendency to flocculate.

It is possible by heating at temperatures of between 65.degree. and 200.degree. C. to convert the known .alpha.-modification of the azo dye of the formula ##STR1## which is unstable to dyeing, completely into the .beta.-modification which is stable to dyeing. The modification transformation can be performed either with the solid dye or with a suspension thereof in an organic, preferably aromatic, solvent. The novel dye modification is stable in dispersion under dyeing conditions, and shows no tendency to flocculate.

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Aesch, Switzerland

Peter E Eugster