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.
The effect of polymeric phosphate chain length on shrinkage temperature and vegetable tannin penetration rates
The use of linear polyphosphates as pretannages for promoting quick vegetable tannin penetration rates has proceeded without much consideration of the theoretical aspects of polyphosphate chain length mediation of penetration. Polyphosphates are available in a range of chain lengths and empirical evidence suggests those of between 5 and 15 phosphate units as most beneficial. Polyphosphates are known to increase shrinkage temperature and this is shown to occur with increasing chain length. Consideration of spatial dimensions together with experimental evidence allows a theory to be proposed accounting for polyphosphate chain length mediation of vegetable tannin penetration. With small polyphosphates insufficient intermolecular crosslinking occurs to prevent acidic swelling of the fibres and a low degree of permeability results. With very large polyphosphates there is sufficient multipoint intermolecular binding to suppress swelling but the physical size of the bound polyphosphates block the access channels available for vegetable tannin penetration and hence result in slow rates of penetration. Medium chain length polyphosphates exhibit suffficient intermolecular crosslinking potential to inhibit swelling but are small enough to allow the quick passage of vegetable tannins into the interior of the hide.
Heat Recovery Systems
Geothermal energy is recovered from an underground zone of relatively hot strata via a borehole into which is inserted a heat pipe system containing a working fluid, the heat pipe system comprising an assembly of two tubes in concentric relation, the inner tube being constituted by a relatively small diameter capillary for the return of working fluid to the vicinity of the zone of the relatively hot strata. The working fluid is preferably assisted in its return under gravity by means of a pump. The system includes heat exchange means operable to recover thermal energy from the working fluid. A third and outermost tube may be used to reduce heat losses, this third tube enclosing the two tubes over all but that part of their length which is in the zone of relatively hot strata.