COLUMNAR CRYSTALS OF 6-HYDROXY-2-NAPHTHOIC ACID AND PROCESS FOR THE PRODUCTION THEREOF

摘要

A process for the production of columnar crystals of 6-hydroxy-2-naphthoic acid, which comprises dissolving crude 6-hydroxy-2-naphthoic acid in an aqueous medium, adding seed crystals of 3-hydroxy-2,7-naphthoic acid or seed columnar crystals to the solution, and cooling the resulting mixture to conduct crystallization; and columnar crystals of 6-hydroxy-2-naphthoic acid produced by the process, which exhibit in the X-ray diffraction a peak 2$g ( u) ranging from 16.8 to 17.8 and/or from 21.3 to 22.3 and have a high apparent specific gravity and excellent fluidity.