Sulphuric acid hemi-esters of dyes prepn. - in improved yields with reduced acidic waste

摘要

Sulphuric and hemi-esters of dyes are of formula F(SO2CH2CH2OSO3H)n (where F = residue of org. colourant and n = 1-4) are prepd. by esterifying cpds. of formula F(SO2CH2CH2OH)n or their salts. Reaction is effected at 80-120 degrees C with 1-5 times (pref. 1.3-2.5) the stoichiometric amt. (calcd. in SO3) of 92-100% H2SO4 or H2SO4 contg. sulphuric anhydride (pref. 15-65% by wt.) or sulphuric anhydride in a kneading machine (for 2min-2h). Method overcomes prior art acid waste problems. In addn., the yields of esterified cpds. are higher, they have higher aq. solubility and give purer colourations on cellulosic materials.