Abstract: Dye dispersant was synthesized using kraft lignin as raw material.Kraft lignin was sulfonated or sulfomethylated with sodium sulfite or sodium sulfite-formaldehyde mixture, then reacted with epichlorohydrin to block a portion of the free-phenolic hydroxyl group and at the same time to cross-link lignin molecules to increase the molecular weight, the end product as dye dispersant was obtained at last.Effects of reaction time, reaction temperature and sodium sulfite amount on the lignin sulfonation, heat stability and dispersibility of dispersing dyestuff were examined.The (suitable) sulfonating conditions were:Na₂SO₃ 1.3 mmol(based on per gram of lignin, same as in the following), (reaction) time 3 h, temperature 160℃;and sulfomethylation conditions were:Na₂SO₃ 1.3 mmol, formaldehyde/sodium sulfite molar ratio 0.8:1, sulfomethylation time 3 h, sulfomethylation temperature 140℃.

Key words: kraft lignin, sulfonation, sulfomethylation, dye dispersant