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In this study, decolorization via a bleaching operation was carried out on chrome and dye spotted skins with several bleaches to valorize the defective leather materials. Sodium perborate, hydrogen peroxide, sodium thiosulfate, sodium percarbonate, and oxalic acid were applied as bleaching agents in production. Sodium perborate by itself was applied and combined with other bleaching agents. Combined processes were also supported with an emulsifier agent for uniform distribution and deeper penetration of bleaching agents into the fibers. Color changes and differences on leather products were determined by Konica Minolta CM-3600d test apparatus spectrophotometrically before and after the applications. Bleached leathers were processed again, re-dyed, and finished after the bleaching operations. Then, bleaching performances of the single and combination applications were also evaluated for the leather strength indicators by analyzing tensile and tear strength of the final products as well as chromium (VI) oxidation of basic chromium (III) salts used in tanning. Antibacterial properties of the final bleached products were also investigated. As a result, sodium perborate was found to provide the most effective and safe bleaching without any physical and chemical deformation by creating antibacterial activity on leather. [ABSTRACT FROM AUTHOR]

In this study, collagen hydrolyzate was obtained from bovine shaving wastes of leather production with the alkali hydrolysis reaction. Total amino acid, total carbon and total nitrogen amounts of liquid collagen hydrolyzate (CH) were determined. Fourier-transform infrared spectroscopy (FTIR) characterization of collagen hydrolyzate was performed. Obtained CH was emulsified with hydrogenated castor and amino functional silicone oils to prepare lubricating protein filler (LPF). Particle size and zeta potential of the LPF were analyzed. 10%, 15%, and 20% LPF was used in the retanning/fatliquoring process of chromium tanned bovine leathers. Performance characterizations of leathers treated with LPFs were carried out with tensile strength, tear strength, filling efficiency, light fastness, shrinkage, and denaturation temperature analyses. Moreover, bounded fat content in leather was also determined. Results showed the increased thermal stability, strength performance and good filling effect in leather by application of the prepared LPF. Consequently, LPF had a good potential as natural retanning/fatliquoring agent via achieving reuse of the solid leather wastes and providing satisfactory leather properties and cleaner production by one product itself. [ABSTRACT FROM AUTHOR]