NUEVAS MODIFICACIONES CRISTALINAS DE UN COLORANTE DIAZO AMARILLO Y PROCEDIMIENTO PARA SU PRODUCCION

Procedimiento para la producción de modificaciones cristalinas de un agente colorante disazo, caracterizado porque un compuesto de un tautómero o un isómero cis/trans o un isómero tautómero cis/trans del compuesto se somete a la acción de uno o varios disolventes del grupo dimetilformamida, N-metilpirrolidona, dimetilsulfóxido, alcohol C4-C20,1,2-diclorobenceno, piridina, nitrobenceno o una combinación de estos disolventes con agua, siendo el contenido acuoso del 0 al 90% en peso, a una temperatura de 100ºC como mínimo. Crystal modifications of a known disazo pigment are obtained by treatment at ≥ 100 degrees C of the dye or a tautomer, cis/trans isomer or tautomeric cis/trans isomer with dimethylformamide, N-methyl-pyrrolidone, dimethyl sulfoxide, 4-20C alcohols, 1,2-dichlorobenzene, pyridine and/or nitrobenzene, optionally in combination with up to 90 wt.% water. Crystal modifications of a known disazo pigment of formula (I) are obtained by treatment at ≥ 100 degrees C of (I) or a tautomer, cis/trans isomer or tautomeric cis/trans isomer with dimethylformamide, N-Me-pyrrolidone, dimethyl sulfoxide, 4-20C alcohols, 1,2-dichlorobenzene, pyridine and/or nitrobenzene optionally in combination with up to 90 wt.% water. Independent claims are also included for: (i) the yellow disazo pigment (I) whose Cu-K alpha X-ray powder diagram shows specified values for alpha , beta , gamma , delta , zeta and eta modifications; and (ii) mixtures of (I) containing ≥ 10 (especially ≥ 90) % of each of these individual modifications or of 2-6 of the modifications.