Method of preparing high activity sulfonated lignin dye dispersants, high activity sulfonated lignin dye dispersants produced thereby and dyestuff compositions containing the same

摘要

Improved dyestuff compositions comprising a dye cake and a dye dispersant are disclosed wherein the dye dispersant comprises sulfonated or sulfomethylated lignin of increased activity and improved heat stability properties and which dispersants are disclosed to be prepared by substantial removal of the low molecular weight component of the sulfonated and sulfomethylated lignin. Exclusion of the low molecular weight portion of the dispersant may be accomplished by fractionation of the sulfonated or sulfomethylated lignin to remove a substantial portion of the molecules having a molecular weight below 3,000. Alternatively, in the case of lignin recovered from sulfate or soda wood pulping processes, the lignin may be fractionated to remove a substantial portion of the molecules having a molecular weight below 3,000 prior to sulfonation or sulfomethylation.