METHOD OF LEATHER TANNING Russian patent published in 1995 - IPC

FIELD: leather industry. SUBSTANCE: leather tanning is carried out by vibration action, hide wetting is carried out at 20-25 C at concentration of surface-active substance 3-6 g/, liquid coefficient (K_l) 1.8-2.2 and vibration frequency (F_v) 2-4 Hz for 2-2.5 min. Liming is carried out at 20-22 C with a mixture of sodium sulfide and sulfite and calcium hydroxide at their concentration 80-100 g/l, 4-8 g/l, 10-12 g/l. at (F_v) 3-8 Hz and (K_l) 1.8-2.2 for 6-8 min. Decalcification is carried out with ammonium sulfate at (K_l) 3-6 g/l, (F_v) 3-8 Hz for 2-2.5 min. Washing is carried out at 18-25 C, at (F_v) 2-4 Hz for 1-3 min. Softening is carried out with protosubtilin at concentration 28-32 g/l, (K_l) 1.2-1.5, at 36-38 C, at (F_v) 3-8 Hz for 3-4 min. Pickling is carried out with sodium chloride and sulfuric acid at their concentration 15-30 g/l and 4-5 g/l, at (K_l) 0.7-0.8, at 20-22 C, (F_v) 5-10 Hz for 3-5 min. Tanning is carried out at concentration of chrome tanning agent 80-100 g/l, at (K_l) 0.7-0.8 mcm, at 20-22 C, at (F_v) 5-10 Hz for 8-10 min. Derma pH increase is carried out with sodium carbonate, at the same frequency and temperature for 4-5 min. Washing with the pure water is carried out at the same frequency for 2-3 min. Staining is carried out at dye concentration in solution 20-50 g/l, (K_l) 1-1.2 at 80-85 C, (F_v) 8-12 Hz for 4-5 min. Filling is carried out at water-soluble polymer 2-6 g/l, (K_l) 1-1.2 at 65-70 C, (F_v) 10-12 Hz for 2-5 min. EFFECT: improved method of leather tanning. 1 tbl