Leather wet blue and method of doffing chromium in normal temperature and at original position from its leftovers

Abstract

This invention relates to an in-situ dechroming approach on a wet-blue leather and the leftovers. The process comprises that organic acids and organic acid salt dechromize step by step in the water solution at room temperature; firstly use the 1 per cent to 40 per cent organic acids to treat the leather, and then use the 1 per cent to 40 per cent organic acid salt to remove chromium. The invention is characterized in that the invention keeps the original structure of the collagen fibers with the dechroming rate as high as 99.6 per cent. The operation is easy and doesn't produce toxic hexavalent chromium. The material can be selected according to the goal products need. Suitable organic acids and organic acid salt can be applied for various post-process. In this way, the approach can obtain different forms of collagen products, especially the high value-added filamentous leather fibers. The approach also can be used for the tanning retire on the surface of the chrome leather with modest process condition, clean wet-blue leather grains and fine grain surfaces.

Description

technical field [0001] The invention belongs to the field of leather chemistry and engineering, and in particular relates to an in-situ dechrome method for wet blue leather and leftovers thereof. Background technique [0002] Chromium salts have been used in leather tanning for more than 100 years. At present, more than 90% of the tanneries mainly use chrome tanning. After chrome tanning, mechanical processing such as edge trimming, smoothing, and leather grinding produces a large amount of chromium-containing waste. There are more than 80% collagen and 3-6% chromium trioxide in these wastes. A lot of research has been done on the treatment of chromium-containing wastes at home and abroad. The key is to remove the chromium in order to recycle them separately. Chromium and Collagen. [0003] According to the different uses of the target products of collagen and chromium, the treatment methods of chromium-containing wastes are different, and the reported methods include oxid...

AI Technical Summary

Problems solved by technology

Using sulfuric acid and sodium hydroxide alternately, the dechroming efficiency is higher than that of acid treatment alone, the stability and quality of the obtained collagen product are higher than those of alkali treatment, and the chromium content of leather can be reduced to 0.13% to 0.15% ( Wang Hongru et al. The method of extracting collagen products from chrome leather shavings. Leather Chemical Industry, 2001, 18(3): 6-9), but strong acid and strong alkali have a greater effect on the destruction of collagen structure

[0006] In addition, leather chrome tanning often has surface over-tanning. The common method is to use oxalic acid to treat it. However, oxalic acid is highly acidic. Although it can be untanned, improper control can easily cause the grain surface of the leather to be damaged due to excessive hydrolysis.