Bleaching and dyeing; fluid treatment and chemical modification – Treatment of hides – skins – feathers and animal tissues – Tanning
Patent
1994-03-14
1995-04-25
Willis, Jr., Prince
Bleaching and dyeing; fluid treatment and chemical modification
Treatment of hides, skins, feathers and animal tissues
Tanning
8 9425, 8 9426, 252 857, C14C 304
Patent
active
054095018
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/EP92/01518 filed Jul. 6, 1992.
1. Field of the Invention
This invention relates to and describes a new highly concentrated form of aluminium triformate in supersaturated, but storable aqueous solution which is particularly suitable for use in the chrome-free or low-chrome mineral tanning of leather and/or skins. The highly concentrated aqueous solutions according to the invention are distinguished from commercially available aluminium-based mineral tanning agents hot only by the fact that, in their case, the active component--aluminium triformate--is already present in the form of an aqueous solution, but also by the fact that this formulation of the mineral tanning agent affords a number of improvements and simplifications in the tanning, finishing and dressing of leather and pelts.
2. Background of the Invention
Considerable significance is attributed to the use of aluminium-based mineral tanning agents and auxiliaries, such as fixing aids, in the production and finishing of leather and skins. The reason for this lies in the wide-scale ecological criticism of the chrome-based auxiliaries of this type which, hitherto, have mainly been used. In practice, aluminium-based mineral tanning agents are available in particular in two forms of which both are solid, namely solid basic aluminium chloride and finely crystalline solid aluminium triformate, which are used as starting materials in the leather and fur manufacturing industry. So far as the results obtained are concerned, the advantages arising out of the simultaneous use of aluminium and lower carboxylic acids, for example in the form of aluminium triformate, are well known. A disadvantage in this regard lies in the comparatively poor solubility of pure crystalline aluminium triformate in aqueous solutions which amounts to less than 5% by weight at typical tanning temperatures. This would also appear to be the key to the fact that, hitherto, aqueous formulations of aluminium triformate have not acquired any practical significance as a starting material for the leather and fur manufacturing industry.
The problem addressed by the present invention was to provide water-based concentrates which would contain aluminium triformate in concentrations far above its solubility in water, but which would nevertheless be stable in storage and could be adjusted to the particular aluminium concentration required simply by dilution at the leather factory. The solution to the problem addressed by the invention is based on the observation that highly concentrated, aqueous concentrates based on aluminium triformate, in which this useful material is present in supersaturated, but storable form, can be prepared under certain conditions which are described in detail in the following. It has also been found that the use of such formulations of the mineral tanning agents and auxiliaries can afford further advantages reflected, for example, in a hitherto unknown degree of liquor extraction.
BRIEF SUMMARY OF THE INVENTION
Accordingly, a first embodiment of the invention relates to the use of at least substantially storage-stable, oversaturated and acidified aqueous solutions of mixtures of aluminium triformate with alkali metal and/or alkaline earth metal formate (hereinafter also referred to as "formate salts") as a concentrated formulation of an aluminium-triformate-based mineral tanning agent in the form of an aqueous solution for the chrome-free or low-chrome tanning of leather and/or skins.
In one important embodiment of the invention, these supersaturated aqueous solutions of formate salts contain small quantities of selected acid-stable stabilizers. Particular significance is attributed in this regard to the addition of butane tetracarboxylic acid as a stabilizer for the supersaturated active-substance solutions, although selected organic polymer compounds are also suitable for the virtually indefinite stabilization in storage of these supersaturated formate salt solutions.
In another embodiment, therefore, the invention relates to storag
REFERENCES:
patent: 1421723 (1922-07-01), Rohm
patent: 2071567 (1937-02-01), Pensel
patent: 2301637 (1942-11-01), Niedercorn et al.
de Riese-Meyer Loert
Hieber Jochen
Schroeder Christine
Zauns-Huber Rudolf
Diamond Alan D.
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Ortiz Daniel S.
Szoke Ernest G.
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