HEAT-STABLE CRYSTAL MODIFICATION OF DYE, PROCESS FOR THE PREPARATION OF THE SAME, AND PROCESSES FOR DYEING HYDROPHOBIC FIBERS WITH THE SAME

摘要

Novel beta -crystal of the compound of chemical formula (1) useful as a dye, which is characterized by excellent dispersion stability at high temperature and by the presence of a sharp peak at a specific position in the X-ray diffraction pattern. A process for the preparation of the above beta -crystal, which comprises heating alpha -crystal of the above compound, which has already been known and is heat unstable, in water or a mixture of water with a water-soluble organic solvent or an anionic or nonionic surfactant at 15 DEG C or above, preferably 40 DEG C or above. The invention also relates to dye compositions comprising the above beta -crystal and processes for dyeing with the beta -crystal or the dye compositions.