WATER-SOLUBLE DYE FOR RECORDING FLUID

摘要

PURPOSE:To provide the title dye which does not cause precipitation of any contaminants on a heating head of an ink jet system utilizing thermal energy, by adjusting the content of iron. CONSTITUTION:Na2SO4 is added to an aq. soln. contg. a water-soluble dye (e.g., C.I. Direct Black 17) at a desired concn. and the precipitate formed by the salting-out is recovered by filtration, washed with a satd. pure water soln. of Na2SO4 and dried. The resulting dry solid is dissolved in a water-soluble org. solvent which is a poor solvent for Na2SO4, but a good solvent for the dye. The soln. is left to stand for a long period of time and filtered. The filtrate is subjected to a re-precipitation treatment with a poor solvent such as acetone and dried. The resulting dye is dissolved in a predetermined amount of pure water and filtered to remove insoluble matters. The soln. is passed through a cation exchange resin layer and the pH thereof is adjusted. The soln. is left to stand for a given period of time and filtered to obtain a water-soluble dye for recording fluid whose iron content is adjusted to not higher than 120ppm.