PROCESS FOR MANUFACTURING COLORED LEATHERS Russian patent published in 2000 - IPC

FIELD: leather industry. SUBSTANCE: process is based on precipitating basic chromium salts on derma fibers in the form of uncharged complexes, which don't prevent anionic dyes from penetration in the course of dyeing. Cattle offal is subjected to ashing, pickling, tannage with basic chromium salts, dubbing, neutralization, dyeing, greasing, and finishing. According to invention, pickling is preceded by treatment with aqueous solution of ammonium sulfate and phenol-formaldehyde resin. The latter is synthesized in alkaline medium from sodium carbonate, urotropin, urea, and water. Reaction mixture is heated to reflux, mixed with nonionic surfactant, and , prior to be used, is diluted with 10 parts of water. EFFECT: improved physico-chemical characteristics of finished skin, eliminated unpleasant odor, and reduced dye consumption. 2 cl, 2 tbl