Abstract

Dyes based on synthetic formulations are widely used in the leather industry, however, many aryl amine dyes are restricted due to their carcinogenic nature. Environmental concern leads one to look for the dye products based on natural resources, which may have advantages of biodegradability and lower toxicity. We aimed to create an eco-friendly dyeing process by forming in-situ complexes between vegetable tannins and the Cr-Fe tanning salt, where the use of iron salts results in various colours on reaction with various vegetable tannins. Sheepskins were tanned using the Cr-Fe tanning salt and treated with various vegetable tanning materials, brown, black and grey shades were developed. The shades obtained have been quantified by reflectance measurements and compared by visual assessment.

Strength characteristics of the leathers treated with 5% vegetable tannins are higher than those treated with 1% tannins, bulk properties not being affected with the increase in concentration from 1 to 5%. The light, wet and dry rub fastness of the naturally coloured leathers are good with no change on ageing. Colour reproduction at bulk level production is acceptable with minor batch variations.