N-vinyl-containing polymeric tanning materials

Details N-vinyl-containing polymeric tanning materials N-vinyl-containing polymeric tanning materials

2000-10-10

2003-11-25

Gupta, Yogendra N. (Department: 1751)

Bleaching and dyeing; fluid treatment and chemical modification

Treatment of hides, skins, feathers and animal tissues

Tanning

C008S09410R, C008S094210, C008S09410P

Reexamination Certificate

active

06652597

ABSTRACT:

The present invention relates to the use of N-vinyl-containing polymers of N-vinylamides and/or N-vinylamines and optionally monoethylenically unsaturated carboxylic acids or their derivatives, other N-vinyl and/or C-vinyl compounds and also other copolymerizable monomers in the form of aqueous solutions or dispersions as leather and fur tanning materials.
In the making of leather, the hide is customarily tanned with mineral tanning materials such as basic chromium, aluminum and/or zirconium salts alone or combined with synthetic tanning materials. A subsequent retanning with natural or synthetic tanning materials mainly has the purpose of improving leather properties such as hand, softness, grain constitution and fullness.
Examples of retanning materials used are syntans, i.e., water-soluble condensation products of, for example, naphthalenesulfonic acid and formaldehyde or of phenolsulfonic acid, formaldehyde and urea, also ligninsulfonic acids and polymers and copolymers based on acrylic acid and other unsaturated polymerizable carboxylic acids, generally combined with the aforementioned syntans.
For instance, U.S. Pat. Nos. 2,205,882 and 2,205,883 describe the use of polyacrylic acid, of copolymers of acrylic acid and methacrylic acid, of styrene-maleic anhydride copolymers, of polymethacrylic acid and of copolymers of methacrylic acid with styrene or methyl methacrylate for tanning leather. The disadvantage with these products is that they frequently fail to produce the desired fullness and grain fineness. In addition, the use of such compounds is frequently associated with tendencies toward a loose grain or double skin, especially in the relatively loosely structured parts of the hide. Moreover, these products generally tend to lighten the dyeing considerably, which necessitates increased consumption of dye and hence more costly formulation.
DE-A 32 45 541, DE-A 32 48 019 and DE-A 32 48 031 disclose copolymers of vinylphosphonic esters, unsaturated sulfonic esters, the total amount of these two monomers being not less than 10% by weight, acrylamide and optionally up to 30% by weight of further monomers such as N-vinylamides and/or unsaturated monocarboxylic acids. The copolymers are recommended for use as retanning materials, inter alia.
Copolymers of N-vinylcarboxamides and their monoethylenically unsaturated compounds such as acrylic acid, acrylic esters, vinyl acetate, N-vinylpyrrolidone or acrylonitrile are well-known products, as are the modified copolymers obtainable by the action of acids or bases, wherein the carboxamide groups can be wholly or partly eliminated from the cocondensed N-vinylcarboxamides and wherein the cocondensed comonomers may be hydrolyzed. Such partially or completely hydrolyzed copolymers of N-vinylformamide are used, for example, as paper dry and wet strength enhancers, as fixing agents and as diketene sizing promoters.
Existing polymeric retanning materials for leather are still in need of improvement with regard to the fullness, grain fineness and grain tightness they confer on the leather and also with regard to the dyeing characteristics.
It is an object of the present invention to provide such retanning materials having improved properties.
We have found that this object is achieved by the use of N-vinyl-containing polymers obtainable by free-radically initiated polymerization of a monomer or monomer mixture of
(A) from 5 to 100% by weight of an N-vinylamide of the general formula I
 and/or of an N-vinylamine of the general formula II
H
2
C═CH—NH—R
2
  (II)
where R
1
and R
2
are independently hydrogen or C
1
-C
6
-alkyl,
(B) from 0 to 95% by weight of monoethylenically unsaturated carboxylic acids having from 3 to 8 carbon atoms, their alkali metal, alkaline earth metal or ammonium salts, anhydrides, esters, amides and/or nitriles,
(C) from 0 to 95% by weight of other N-vinyl and/or C-vinyl compounds selected from the group consisting of N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylimidazole, N-vinyl-2-methylimidazole, N-vinyl-4-methylimidazole, N,N-diallylammonium chloride, vinyl acetate, vinyl propionate, styrene and methylstyrenes, and
(D) from 0 to less than 10% by weight of other copolymerizable monomers,
wherein the proportions of said monomers (A) to (D) add up to 100% by weight and the N-acyl groups derived from said N-vinylamides I are partially or completely removable from the resulting polymers by hydrolytic detachment using acids or bases, in the form of aqueous solutions or dispersions as tanning materials for self-tanning, pretanning and cotanning leather pelts and fur pelts and for retanning leather and fur.
Examples of useful monomers (A) of the formula I are N-vinylformamide, N-vinyl-N-methylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide, N-vinylpropionamide, N-vinyl-N-methylpropionamide and N-vinyl-butyramide. Of this group of monomers, N-vinylformamide is preferred.
Examples of useful monomers (A) of the formula II are the corresponding vinylamines (H instead of R
1
) having the same R
2
.
Useful monomers (B) are monoethylenically unsaturated carboxylic acids having from 3 to 8 carbon atoms, especially having from 3 to 6 carbon atoms, such as acrylic acid, methacrylic acid, dimethacrylic acid, ethacrylic acid, maleic acid, citraconic acid, methylenemalonic acid, allylacetic acid, vinylacetic acid, crotonic acid, fumaric acid, mesaconic acid and itaconic acid. The monoethylenically unsaturated carboxylic acids can be used in the copolymerization in the form of their free acid and the anhydride (if it exists) or in partially or completely neutralized form. To neutralize these monomers, preference is given to using alkali metal or alkaline earth metal bases, ammonia or amines, e.g., sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, magnesium oxide, calcium hydroxide, calcium oxide, gaseous or aqueous ammonia, triethylamine, ethanolamine, diethanolamine, triethanolamine, morpholine, diethylenetriamine or tetraethylenepentamine.
Examples of further useful monomers (B) are the esters, amides and nitriles of the above-specified carboxylic acids, e.g., methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyisobutyl acrylate, hydroxyisobutyl methacrylate, methyl hydrogen maleate, dimethyl maleate, ethyl hydrogen maleate, diethyl maleate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, acrylamide, methacrylamide, N-dimethylacrylamide, N-tert-butylacrylamide, acrylonitrile, methacrylonitrile, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate and also the salts of the last monomers with carboxylic acids or mineral acids and also the quaternized products.
In a preferred embodiment, monomers (B) are selected from acrylic acid, methacrylic acid, maleic acid, maleic anhydride or mixtures thereof.
With regard to monomers (C), preference is given to styrene and methylstyrenes, i.e., &agr;-methylstyrene, &bgr;-methylstyrene, o-methylstyrene, m-methylstyrene and p-methylstyrene.
Examples of other copolymerizable monomers (D) are acrylamidoglycolic acid, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, 3-sulfopropyl acrylate, 3-sulfopropyl methacrylate and acrylamidomethyl-propanesulfonic acid and also monomers containing phosphonic acid groups, such as vinylphosphonic acid, allylphosphonic acid and acrylamidomethanepropanephosphonic acid.
It will be appreciated that, for each of the four monomer varieties (A) to (D), it is also possible to use mixtures of the respective monomers.
Furthermore, the polymers set forth in the claims also encompass graft copolymers of the above-described N-vinyl-containing homo- or copolymers as grafting base with, for example, styrene and/or methylstyrenes, acrylonitrile, n-butyl acrylate, n-butyl methacrylate or other monomers already mentioned above. It will be readily appreci

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