POSSIBILITIES OF IMPROVING QUALITY CHARACTERISTICS OF INACTIVE NEUTRAL LIGNOSULFONATES

Abstract

The article proposes a method of increasing the amount of OH-phenolic functional groups in the composition of a macromolecule lignosulphonate, a sulfo-derivative natural lignin polymer, tested under laboratory conditions by step-by-step chemical treatment of the lignosulphonate matrix with a solution of a bromine derivative, then with a solution of neutral sodium sulfite. This makes it possible to solve the problem characteristic of modern lignosulphonates of neutral sulfite production method, which have low values of tannidicity index: content of OH-phenolic groups, quantitative content of which forms inhibitory (tanning) capacity of lignosulphonates. The proposed procedure involves carrying out said demethylation reaction with cleavage of methyl group contained in phenylpropane unit of lignosulfonate. Pyrocatechin groups are formed and methanesulfonic acid molecule is cleaved off. The obtained product was analyzed by UV spectroscopy and the increase in optical density in the area of absorption of 280 nm characteristic of OH-phenolic functional groups was shown, which is the basis for the appearance of pyrocatechin structures in the phenylpropane unit of lignosulfonate. Proposed method allows increasing quantitative content of OH-phenolic groups in macromolecule composition from 1.7% of initial to 6.5%. The obtained results are correlated with the data on determination of tannidicity index - one of objective characteristics of inhibitory (tanning) capacity of lignosulfnates, which is 32%, compared to similar characteristic of undemethylated neutral lignosulfonate, where the value did not exceed 21%. The data show that demethylation of the lignosulphonate matrix is possible by converting modern inactive neutral lignosulphonates from the low-demand waste category of the pulp and paper industry to a promising raw material component.