Chrome free organic tannages and molecular level understanding of the tanning process for the production of leather with high hydrothermal stability Samir DasGupta , New Zealand Leather and Shoe Research Association
It is rather strange that today I am talking about chrome-free tannages when I have devoted my whole life to improving the chrome-tanning system. When I was a student, I wondered why chrome tanned leather that stood the boil, did so only for about 1 to 2 minutes. My ambition was to find out how leather could be treated like textile, and we discovered and patented a product and process for improving the hydrothermal stability of chrome-tanned leather. This patent showed how chrome tanned leather could be boiled like textile for an hour without area loss. At LASRA we have also developed LASRA ThruBlu and modified ThruBlu processes to minimise the environmental impact of chrome tanning.
Combined organic tanning based on mimosa and oxazolidine: development of a semi-industrial scale process for high-quality bovine upper leather
In this study we present an industrial-scaled tanning process intended to replace chrome tanning in the production of high quality bovine shoe upper leathers using a combined tannage based on a mimosa and oxazolidine as cross-linking agent. This paper reports the best recipe developed and the properties of the leather obtained. The various test results and scanning electron microscopy (SEM) observations which were used as investigative methods to follow the tanning process steps and to better understand the cross-linking mechanisms, are detailed together with the characterisation of the effluents. The leather obtained is characterised by a good hydrothermal stability coupled with good physical and technical properties which allow it to easily comply with the standards required for high quality chromium-tanned bovine upper leather. The results obtained suggest that this tannage is a promising alternative to traditional chrome tanning.
Speciation of chromium (VI) and total chromium determination in welding dust samples by flow-injection analysis coupled to atomic absorption spectrometry.
We have studied the speciation of chromium (VI) in stainless-steel welding dusts. The approach used for the analysis of Cr(VI) and total Cr relies on a flow-injection analyzer (FIA) equipped with two different sequential detectors. The system measures Cr(VI). by colorimetry (with 1,5-diphenyl carbohydrazide) and total chromium content by flame atomic absorption spectroscopy (AAS). The extraction of the samples of welding-fume dusts is achieved in a buffer solution (acetic acid and sodium acetate at pH 4). This extraction procedure gives a 96% recovery of chromium (VI). The FIA-AAS system that has been described is also more sensitive, has a lower detection limit (0.005 mug ml(-1)) and gives a better precision (< 1%) than other equivalent systems that have been previously described.