FR1451814A - Tanning process - Google Patents

Abstract

In a process for tanning and re-tanning hides, pelts, e.g pickled pelts having a pH between 2.0 and 3.5, wool-skins, fur-skins and leathers, they are treated with a tanning agent comprising zirconium, aluminium and chromium salts, the proportion of these salts, computed as the proportion of the oxides ZrO2:Al2O3:Cr2O3, bein 100: 5-50: 2-30, preferably 100: 10-20: 3-8, by weight. The tanning agent may be a mixed complex of Zr, Al and Cr salts obtained by heating and/or dehydrating, e.g. evaporating, spray-drying or roller-drying, an aqueous solution containing them. According to Example 1, a powdered Al-Cr mixed complex is prepared and mixed with aqueous, technical zirconium sulphate, the mixture is heated to 80 DEG C., then cooled and spray-dried to yield a powdered tanning agent, in which the proportion of the oxides ZrO2:Al2O3: Cr2O3 is 100: 14: 7. Tanning may be effected first with a zirconium salt, and then with aluminium and chromium salts, e.g. in the form of a mixed Al-Cr complex described in French Specification 1,244,477. The tanning agent may be in the form of an aqueous paste, a highly concentrated aqueous solution, or a powder. Specified zirconium salts are: zirconium sulphate, e.g. containing finely divided silica gel, and zirconium oxychloride containing sodium sulphate. Specified aluminium salts are the sulphate, chloride and acetate. Specified chromium salts are the sulphate, nitrate, chloride, acetate and formate, and chrome alum. The tanning agent may also comprise one or more of the following acids and their sodium salts: sulphuric, phthalic, sulphophthalic, sulphosuccinic, tartaric, formic, acetic, lactic, glycollic and citric. Resulting leathers may be re-tanned or after-treated with a mineral, vegetable, synthetic or resinous tanning agent, then dyed, fatliquored, filled and dried. A suitable synthetic re-tanning agent is described in U.K. Specification 443,967. The following types of leather may be prepared using the process according to the invention: full grain leather, suede leather, nubuk, white or dyed glove leather, white splits, white belt leather, sole leather, aniline dyed kid leather and shrunk leather.