CHEMICAL PROCESS FOR GRAFTING CATIONIC MOIETIES ONTO KRAFT LIGNIN, TO PRODUCE WATER SOLUBLE LIGNINS IN ALL PH RANGE, OBTAINED KRAFT LIGNINS AND THEIR USES

The invention relates to a chemical process for grafting cationic moieties onto kraft lignin to produce watersoluble lignins over the entire pH range. The process involves the extraction of lignin from a black liquor obtained during the industrial process of cooking a wood by the kraft process, its reaction with quaternary ammonium compounds in an aqueous alkaline medium and, finally, the neutralization of the reaction medium to obtain a solution of the cationic lignin. The process described in this invention allows the resulting product to be soluble in water over the entire pH scale, it takes place in an aqueous medium, with mild reaction conditions and through low-cost reagents, allowing kraft lignins to be given water-solubility properties comparable to those characteristics of lignosulfonates.The invention also concerns the lignins obtained and their uses, namely their use for antioxidant activity, for removing dyes, for modifying cellulosic pulp to produce paper products, for modifying the surface of paper products and for plasticizing formulations of concrete.