Dyeing-stable monoazo dyestuff, a process for its preparation, and its use

Abstract

A dyeing-stable modification (.beta.-modification) of the dyestuff of the formula (I) ##STR1## which has the X-ray diffraction diagram shown in FIG. 1 and having the characteristic reflections at the following glancing angles and relative intensities: ______________________________________ [.theta.] 2.74 4.27 4.70 5.50 8.74 11.24 12.44 relative 100 72 40 23 27 32 26 intensity ______________________________________ a process for its preparation by heating the dyestuff of said formula (I) of the dyeing-unstable .alpha.-modification, characterized by an X-ray diffraction diagram having the characteristic reflections at the following glancing angles and relative intensities ______________________________________ [.theta.] 3.55 4.15 5.35 9.45 10.41 12.71 13.89 relative 42 100 35 24 34 94 48 intensity ______________________________________ at temperatures of 60.degree. to 120.degree. C. in an organic solvent, and its use for dyeing fiber materials made of cellulose esters or synthetic linear polyesters.

Dependencies are inferred from the claim text.