METHOD OF PREPARING SYNTHETIC TANNER Russian patent published in 2001 - IPC

FIELD: leather industry. SUBSTANCE: invention relates to production of synthetic tanner used in leather industry when manufacturing sole leather and when performing retannage after greasing operation. Beta-naphthol is sulfonated at 115-120 C at continuous stirring to give beta-naphtholsulfonic acid, which is brought into reaction with dihydroxydiphenyl sulfone employed in the form of aqueous suspension prepared by mixing crushed dihydroxydiphenyl sulfone with water at 50-60 C to homogeneous state. Condensation is carried out in presence of formalin which is added for 1-1.25 h, total reaction time being 4-5 h. Condensation mixture is neutralized by ammonia solution to pH 2.5-3.0. Neutralized polycondensation product is dispersed in preheated to 50 C lignosulfonate at 80-90 C for 1.5-3 h. Thus obtained tanner is concentrated by evaporation. EFFECT: increased yield of product and reduced consumption of expensive raw material owing to use of lignosulfonate being a paper-and-pulp industry waste.