METHOD OF MAKING CHROMIUM TANNING LEATHERS Russian patent published in 1999 - IPC

FIELD: making of various types of leathers, footwear top, linings and fancy goods. SUBSTANCE: method comprises leather pickling with sulfuric acid consumption of 1.0- 1.3% based on weight of depilated hide. Tanning is then carried out in the presence of monocarboxylic acid at its consumption of 0.1-0.5% based on weight of depilated hide with chromium tanning agent. Tanning agent is prepared by using chromichromates dissolved in sulfuric acid to complete deolification of chromium (III) compounds, and chromium VI is reduced by alternately adding to reaction mixture inorganic and organic reducing agents to correct interfacently basicity of tanning agent is 1.3-1.5% based on weight of depilated hide calculated for chromium (III) oxide. Semiproduct is then neutralized with mixture of neutralizing agents. Neutralizing agents are added in three steps by alternating mixture and individual agents. Method makes it possible to reduce consumption of tanning chromium compounds, decrease content of chromium compounds in spent solutions and make leathers corresponding to GOST standards. EFFECT: more efficient making method. 2 cl, 5 ex, 1 tbl