METHOD OF PREPARING LIQUID COMPOSITION OF SULFUR DYES Russian patent published in 1995 - IPC

FIELD: chemical technology. SUBSTANCE: liquid composition of sulfur dyes is prepared by treatment of sulfur dye paste after thioning and isolation with reducing agent sugar. Glucose, sucrose, lactose or xylose (concentration is 1-25% of sulfur dyes paste mass) were used as reducing agent in aqueous alkaline medium at pH 9-14, at 60-100 C. Preferably, the washing sulfur dyes paste before treatment with water up to inorganic sulfate contents 6% of solid particle mass (not more). Treatment is carried out in nitrogen flow in the presence of nonionogenic hydrotropic substance. Method ensures to decrease sulfide content in the end product up to ≅ 3%. EFFECT: improved method of composition preparing. 5 cl