Lignin
Lignin is a natural aromatic, a heterogeneous biomacromolecule that exists as the second most abundant polymer, next to cellulose. Lignin is contained in the cell walls of plants and obtained as a byproduct of the paper and lignocellulosic industries.
lignosulphonate is used as dispersants, binders, complexing agents, and emulsifying agents.
It can also be used as high purity Kraft lignin with good reactivity in chemical formulations. In this case, it is usually sold as a free-flowing brown powder. It can also be used as a coal-water slurry additive, a tanning auxiliary in the leather industry, or for electroplating and electrolysis. It can be used for water plugging purposes in geology, oilfields and consolidated well walls and oil exploitation solutions.
The chemical structure of lignin, like that of many other natural polymers, is very complex. As lignin is normally insoluble in non-polar and organic solvents, a frequent method used to separate cellulose from lignin is to treat wood chips with a chemical solution at high temperatures. As a result, the basic component of the polymer, phenyl propane, is sulfonated and certain bonds between lignin and carbohydrates are broken down. The lignosulphonate obtained in this manner comprises polymers of varying weight, based on hydrolysis, the main components of which are calcium lignosulphonate and a number of polysaccharides.
Lignosulphonates can be polymerized, hydrolyzed, halogenated, nitrated, oxidized, dehydrogenated, or desulfonated. They can enter into mixed dimeric reactions with other functional groups for which they are excellent extenders. The polysaccharide groups can be oxidized, inverted, or eliminated by using molecular separation processes.