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

摘要

This invention related to a novel beta -crystal of the compound represented by the following formula (1), which is useful as a dyestuff. The beta -crystal of this invention is characterized by being stable in high temperature and having sharp peaks in the powder X-ray diffractometory. This invention is related to a process for producing a said beta -crystal, said process comprising heating a known thermally unstable alpha -crystal at a temperature higher than 15 DEG C, prefarablly higher than 40 DEG C in water, a water-soluble organic solvent, or a solvent comprising water containing an anionic or nonionic surface active agent. Furthermore, this invention is related to a dyestuff composition cotaining of the said beta -crystal, and a process for dyeing comprising employing the said beta -crystal.