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

FIELD: leather industry. SUBSTANCE: synthetic tanner is prepared by condensation of synthetic phenol, formalin, and lignosulfonate followed by dispersing of thus obtained resin in the same lignosulfonate. Condensation is first carried out in presence of 15% sulfuric acid at stirring and 40-45 C for 30 min, after which formalin is added with velocity 4-5 l/min at 40-45 C, reaction mixture is then stirred at 95-100 C until free formaldehyde is no more available. Resulting phenol- formaldehyde resin is dispersed in lignosulfonate reheated to 50-60 C and mixture is stirred at 95-100 C for 3-4 h until final product with pH 3.5- 4.5 is obtained. EFFECT: extended choice of tanners and reduced expenses on starting materials.