Use Of Chrome Residue To The Development Of Leather Complex Tanning Agents And Finishing Agents

As the center of leather industry in the world, China produced over 700.000 metric tons of chromium-containing leather wastes every year, which not only heavily polluted the environment, but also wasted large amount of useful collagen protein and chromium resources because of the wastes not being properly utilized.The thesis focused on recycling of chrome leather wastes and transforming them into value-added products. Based on applying three steps hydrolysis and proper modification methods, an innovative process has been designed to extract respective hydrolysates. and thus used them at their most value. The typical characteristics of this process were fully utilization of leather wastes and avoiding reproducing any other waste during the treatment.The reason that the residue protein was difficult to be completely hydrolyzed was demonstrated for the first time by comparation of the amino acid compositions between hydrolysates and residue protein. Based on that three steps hydrolysis processes, namely, alkali-alkali-acid hydrolysis, were designed to treat the wastes, in which the first extracted gelatin was used to prepare protein finishing agents, and the collagen polypeptide extracted in the second steps was use for chrome-free protein retanning agents, then the final acid hydrolyzed residues were utilized for chromium-containing protein retanning agents. The molecular weight dispersion of the hydrolysates was also studied with GPC, SDS-PAGE and HPLC/ESI-MS.By study of the mechanism of paraffin oxidized and MAH grafted on paraffin, a noval method, that is, the combination of both oxidizing and grafting on paraffin. was used to modify paraffin, and the mechanism of which was discussed. These results are also of momentous significance in the field of chemical modification of paraffin. Moreover, as an intermediate used in the modification of hydrolysates. the modified paraffin can greatly improve the properties of the end leather chemicals.Various methods, such as grafting polymerization, seeding polymerization and latex interpenetrating polymer network, were applied in physical and chemical modification of the hydrolysates to produce good leather chemicals. Application tests indicateded that chrome-free protein retanning agents showed very good fatliqouring and filling properties, chromium-containing protein retanning agents can greath' increase leather Ts. and protein finishing agents show excellent properties of leather finishing.