Bleaching and dyeing; fluid treatment and chemical modification – Treatment of hides – skins – feathers and animal tissues – Tanning
Patent
1998-06-10
2000-03-07
Merriam, Andrew E. C.
Bleaching and dyeing; fluid treatment and chemical modification
Treatment of hides, skins, feathers and animal tissues
Tanning
8 9421, 524548, 524558, 526266, C14C 322, C14C 328, C08F21638, C08F22200
Patent
active
060334428
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the use of aqueous solutions or dispersions of copolymers composed of carboxyl-containing monomers, ethylenically unsaturated cyclic or hemicyclic acetals, ketals or orthocarboxylic esters, with or without further copolymerizable monomers, as tanning agents for leather. Since some of these copolymers are novel substances, the invention relates to them as well.
In the production of leather, the main tanning is usually carried out using mineral tanning agents, such as basic chromium, aluminum and/or zirconium salts, alone or in combination with synthetic tanning agents. Subsequent retanning using natural or synthetic tanning agents serves to improve properties of the leather such as handle, softness, grain characteristics and body.
Examples of tanning agents in retanning are syntans, ie. water-soluble condensates of, for example, naphthalenesulfonic acid and formaldehyde or of phenolsulfonic acid, formaldehyde and urea, furthermore lignosulfonic acids, and also polymers and copolymers based on acrylic acid and other unsaturated polymerizable carboxylic acids, generally in combination with the abovementioned syntans.
For example, U.S. Pat. No. 2,205,882 (1) and U.S. Pat. No. 2,205,883 (2) describe the use of polyacrylic acid, of acrylic acid-methacrylic acid copolymers, of styrene-maleic anhydride copolymers, of polymethacrylic acid, and of copolymers of methacrylic acid with styrene and/or methyl methacrylate for the tanning of leather. A disadvantage of these products is that in many cases the desired softness and body cannot be achieved. Furthermore, these products generally have a strong lightening effect on the coloring. It should also be noted that products of this kind can be employed only in a limited concentration when retanning leather, since at higher levels hardening of the leather may occur and may lead to cracking of the grain.
The known polymeric retanning agents for leather are still in need of improvement in respect of the body and softness they impart to the leather and in their coloring properties.
It is an object of the present invention, therefore to provide such retanning agents with corresponding, improved properties.
We have found that this object is achieved by the use of aqueous solutions or dispersions of copolymers composed of acids having 3 to 10 carbons, their anhydrides, their alkali metal, alkaline earth metal or ammonium salts, or mixtures thereof, orthocarboxylic esters of the formula I ##STR2## where R.sup.1 and R.sup.2 independently are hydrogen, C.sub.1 -C.sub.10 -alkyl, C.sub.1 -C.sub.10 -alkoxy, amino, C.sub.1 -C.sub.4 -alkylamino or di-C.sub.1 -C.sub.4 -alkylamino, independently are hydrogen, C.sub.1 -C.sub.10 -alkoxy, amino, C.sub.1 -C.sub.4 -alkylamino, di-C.sub.1 -C.sub.4 -alkylamino, C.sub.6 -C.sub.14 -aryl, C.sub.7 -C.sub.18 -aralkyl, carboxyl, C.sub.1 -C.sub.20 -alkoxycarbonyl, C.sub.2 -C.sub.18 -alkyl interrupted by 1-5 nonadjacent oxygens, or are sulfo or phosphono, C.sub.7 -C.sub.18 -aralkyl or C.sub.1 -C.sub.10 -acyl, hydroxyl or C.sub.1 -C.sub.10 -acyloxy and carbons and for carbons, and tanning agents for the self-tanning, pretanning and assist tanning of leather pelts and skin pelts and for the retanning of leather and skins.
Particularly suitable carboxyl-containing monomers from group A are monoethylenically unsaturated mono- or dicarboxylic acids or their corresponding anhydrides of 3 to 6 carbons, for example acrylic, methacrylic, ethylacrylic, allylacetic, crotonic, vinylacetic, maleic, itaconic, mesaconic, fumaric, citraconic, and methylenemalonic acids, monoalkyl maleate, and the alkali, alkaline earth metal and ammonium salts of these acids, or mixtures thereof. In the case of monoalkyl esters of dicarboxylic acids, the given number of carbons relates to the dicarboxylic acid structure, while the alkyl ester group can independently have from 1 to 20, especially 1 to 8, carbons. Suitable, corresponding, monoethylenically unsaturated dicarboxylic anhydrides are maleic anhydride, itaconic anhydride, citraconic anhydride
REFERENCES:
patent: 2205882 (1940-06-01), Graves
patent: 2205883 (1940-06-01), Graves
Synthesis and Characterization of Poly [(3,4-Dihydro-2H-Pyran)-alt (Maleic Anhydride)] and Its Derivatives: Biologically Active Polymers, Man Jung Han, et al, Journal of Polymer Science, vol. 28, 2719-2728 (1990).
Denzinger Walter
Greif Norbert
Kistenmacher Axel
Kneip Michael
Oppenlander Knut
BASF - Aktiengesellschaft
Merriam Andrew E. C.
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