Bleaching and dyeing; fluid treatment and chemical modification – Treatment of hides – skins – feathers and animal tissues – Tanning
Patent
1993-10-07
1996-03-26
Willis, Jr., Prince
Bleaching and dyeing; fluid treatment and chemical modification
Treatment of hides, skins, feathers and animal tissues
Tanning
8 9427, 8 9429, 8 9433, 252 857, C14C 306, C14C 308
Patent
active
055017088
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/au92/00154 filed Apr. 9, 1992.
The present invention relates to a process for the preparation of tanned leather which utilises metals other than chromium, and to compounds for use in such a process.
Leather is a material which is sensitive to heat when in a wetted state and may be subject to marked shrinkage which may occur abruptly over a relatively narrow temperature range. The temperature which marks the onset of such shrinkage is known as the shrinkage temperature. The shrinkage temperature differs according to the type of tanning material used and is thus used to characterise a particular type of leather. In general terms, the highest degree of hydrothermal stability is customarily obtained with chrome tanning agents. However, chrome tanning agents generate pollution problems due to the effluent generated. Concerns as to the carcinogenic nature, of chromium (VI) compounds have lead to the introduction of chrome content restrictions for industrial effluent.
Significant research has been initiated in the prior art to develop a non-chrome tanning system which will produce leather characteristics at least comparable with chrome leathers. Aluminium tanning systems have been tried, however such systems suffer from three disadvantages. Firstly, aluminium binds to collagen over a very narrow pH range which is close to the precipitation point of the tanning salt. Secondly, the maximum shrinkage temperature obtainable with aluminium alone in the prior art has been approximately 80.degree. C. This may be compared with chrome tanned leathers having shrinkage temperatures of between approximately 100.degree. C. and 125.degree. C. Thirdly, aluminium tanned products deteriorate due to the fact that the aluminium may migrate out of the leather and is thus generally unstable over time. During wool skin dyeing for example, aluminium removal is a particular problem.
Attempts have been made in the prior art to overcome these difficulties. For example, in GB Patent Application 2,153,844, it has been proposed to tan hides and skins using a basic aluminium salt and a polycarboxylic acid of, benzene containing three or more carboxylic acid groups. Whilst such additives have improved hydrothermal stability somewhat, leathers produced by such techniques are still substantially inferior to chrome leathers and still suffer from significant deterioration over time due to aluminium depletion.
Accordingly, it is an object of the present invention to overcome, or at least alleviate, one or more of the difficulties related to the prior art.
Accordingly, in a first aspect of the present invention, there is provided a process for the preparation of tanned leather, which process includes chromium, aluminium, titanium or zirconium; and acid or derivative thereof; sufficient to complex therewith.
The leathers produced according to the process of the present invention may be characterised by improved hydrothermal stability as measured by an increase in shrinkage temperature. The leather produced according to the process of the present invention may further be characterised by an excellent light fastness of the leather.
The skin or hide to be treated may be of any suitable type. The skin or hide may be obtained from an ovine, porcine, bovine or caprine animal, An ovine skin such as a wool skin is preferred. The skin or hide may be pre-treated in any manner known per se, to prepare the hide for the tanning process. A green hide may be used. The hide may be pickled hide. A pickled woolskin is preferred.
However the process of the present invention may also be applied to a delimed hide, for example a delimed sheepskin pelt. It is accordingly unnecessary to submit the hide to a pickling and salt treatment step. This may reduce effluent and corrosion problems.
The metallic salt utilised to treat the skin or hide, as stated above, may be a chromium, aluminium, titanium or zirconium salt. Preferably an aluminium, titanium or zirconium salt is used. An aluminium salt is preferred. Basic aluminium basic chloride, alu
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Huynh Chi P.
Milligan Brian
Montgomery Kenneth C.
Pojer Peter
Commonwealth Scientific and Industrial Research Organisation
Diamond Alan D.
Willis Jr. Prince
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