Bleaching and dyeing; fluid treatment and chemical modification – Treatment of hides – skins – feathers and animal tissues – Tanning
Patent
1993-07-29
1994-12-13
Willis, Jr., Prince
Bleaching and dyeing; fluid treatment and chemical modification
Treatment of hides, skins, feathers and animal tissues
Tanning
8 9418, 8 9421, 252 89, C14C 316
Patent
active
053726090
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/EP92/00116 filed Jan. 21, 1992.
The present invention relates to an improved process for self-tanning, pretanning and assist tanning pelts and skin pelts and for retanning leather and skin.
Aldehydes and in particular dialdehydes such as glutardialdehyde are frequently described in the literature and used in practice as tanning agents for leather. For instance, DE-A-17 69 059 describes a process for making leather by treating tannable material with zinc salts, water-soluble sulfates and aldehydes or aldehyde-eliminating substances and aftertreating with basifying agents.
However, these processes and the leather and skin obtained by these processes frequently have a number of disadvantages. The leather obtained, especially by tanning with glutardialdehyde, is frequently yellowed; particularly noticeable problems can arise when glutardialdehyde is used as a tanning agent for fur, since fur thus tanned can be strongly yellowed not only on the flesh side but also on the hair side. Furthermore, because the aldehydes used are highly volatile and frequently very toxic or otherwise potentially injurious to health, safety measures need to be taken and a relatively large amount of the aldehyde tanning agent needs to be used.
It is an object of the present invention to provide novel tanning agents for self-, pre-, assist- and re-tanning which are free of the disadvantages of the prior art.
We have found that this object is achieved by an improved process for self-tanning, pretanning and assist tanning pelts and skin pelts and for retanning leather and skin, which comprises using for this purpose the compound of the formula I ##STR1## or an acetal thereof.
Besides -3-oxoglulardialdehyde compound I itself it is also possible to use the corresponding acetals The acetal radicals used are customarily the radicals customary for this purpose, for example C.sub.1 -C.sub.8 -alkyl groups, preferably C.sub.1 -C.sub.4 -alkyl groups, such as methyl, ethyl, n-propyl, n-butyl or 2-ethylhexyl. The two acetal radicals can be different or preferably identical. Furthermore, these two radicals can be linked to one another to form a five- or six-membered ring, for example a 1,3-dioxolane, 1,3-dioxane, 5,5-dimethyl-1,3-dioxane or 5-n-butyl-5-ethyl-1,3-dioxane ring.
The compounds I and the acetals or ketals thereof are known in principle; they are preparable by literature methods.
The tanning process of the present invention is highly suitable for self-tanning and pretanning pelts and skin pelts in aqueous liquor. This is advantageously done by treating the pickled pelts, for example cattle pelts having a split thickness of from 1.5 to 4 mm, or skin pelts, for example sheepskin pelts, with an aqueous solution or dispersion of carbonyl compounds I at a pH of from 2 to 7, in particular from 2.5 to 4, and at from 15.degree. to 50.degree. C., in particular at from 25 to 45.degree. C., for a period of from 3 to 20 hours. The treatment takes the form for example of milling in a drum. The amount of carbonyl compound I required is normally, based on the pelt weight, from 2 to 30% by weight, in particular from 5 to 20% by weight. The liquor length, i.e. the percentage weight ratio of treatment liquor to goods, is customarily from 30 to 200% in the case of pelts or from 100 to 2000% in the case of skin pelts, in either case based on the pelt weight.
On completion of the treatment the leather or skin is customarily brought to a pH of from 4 to 8, in particular 5 to 7, using for example magnesium oxide, sodium carbonate or sodium bicarbonate, optionally treated with further tanning agents and, on completion of the tanning process, optionally dyed and fatliquored.
The tanning process of the present invention is likewise highly suitable for assist tanning pelts and skin pelts together with the tanning agents of the main tannage, which can be for example a chrome or aluminum tannage. In this case the working conditions concerning pH, temperature and duration of treatment are adjusted to the requirements of the main compon
REFERENCES:
patent: 2351338 (1944-06-01), Howard
patent: 2516283 (1950-07-01), Winheim et al.
patent: 3080281 (1963-03-01), Fischer et al.
English abstracts of Gustavson, Svensk Kem. Tid., 61, 114 (1949).
Birkhofer Hermann
Reuther Wolfgang
Schaffer Ortwin
Stork Karl
Weiser Juergen
BASF - Aktiengesellschaft
Diamond Alan D.
Willis Jr. Prince
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