METHOD OF PRODUCING DEMETHYLATED LIGNOSULPHONATES Russian patent published in 2020 - IPC C08L97/00 C07G1/00 

FIELD: chemistry.

SUBSTANCE: present invention relates to a method of producing demethylated lignosulphonates by carrying out a demethylation reaction. This method involves preliminary treatment of aqueous solution of neutral lignosulphonate with bromine derivative HBr to pH 4–4.5 while stirring for 25–30 minutes and heating to 30–40 °C. Further, the solution is filtered and dry reactive sodium sulphite Na₂SO₃ is added to the filtrate to pH 6–6.5 while stirring and heating to 75–80 °C for 1–1.5 hours. One part of lignosulphonate is taken with 0.2–0.4 parts of HBr and 2.5–3.5 parts of Na₂SO₃, and the degree of demethylation is determined from the quantitative formation of methanol.

EFFECT: high content of OH-phenol groups in the lignosulphonate macromolecule due to the demethylation reaction.

1 cl, 2 tbl, 3 ex