Process for the simultaneous tanning and dyeing of collagen containing fibrous material

Abstract

A process for the simultaneous tanning and dyeing of collagen containing fibrous material, wherein the said material is treated with a liquor containing at least one reactive dyestuff selected from the group of formula (1) and (2) ##STR00001## wherein A.sub.1, A.sub.2 and A.sub.3 are each independently of the others the radical of a monoazo, polyazo, metal-complexed azo, anthraquinone, phthalocyanine, formazan or dioxazine chromophore having at least one sulfo group, B is an organic bridge member, Q.sub.1, Q.sub.2, Q.sub.3 and Q.sub.4 are each independently of the others hydrogen or unsubstituted or substituted C.sub.1-C.sub.4alkyl, G.sub.1 and G.sub.2 are halogen, 3-carboxypyridin-1-yl or 3-carbamoylpyridin-1-yl, (Z.sub.1).sub.2-3 is 2 to 3 identical or different fiber reactive radicals, Z.sub.2 and Z.sub.3 are each independently of the other identical or different fiber reactive radicals, and b is the number 0 or 1, by combining two steps of leather production, tanning and dyeing, into a single step, thus, preserving resources and reducing the environmental impact.

Claims

1. A process for the simultaneous tanning and dyeing of collagen containing fibrous material, the process comprising treating a collagen containing fibrous material with an aqueous liquor comprising at least one reactive dyestuff, wherein the aqueous liquor has a pH less than a pH required to fix the at least one reactive dyestuff, and wherein treating comprises distributing the at least one reactive dyestuff throughout a thickness of the material; and increasing the pH of the aqueous liquor to simultaneously tan the fibrous material by crosslinking the fibrous material and fix the dye to the fibrous material, wherein the at least one reactive dyestuff is selected from the group of formula (1) and (2) ##STR00031## wherein A.sub.1, A.sub.2 and A.sub.3 are each independently of the others the radical of a monoazo, polyazo, metal-complexed azo, anthraquinone, phthalocyanine, formazan or dioxazine chromophore having at least one sulfo group, B is an organic bridge member, Q.sub.1, Q.sub.2, Q.sub.3 and Q.sub.4 are each independently of the others hydrogen or unsubstituted or substituted C.sub.1-C.sub.4 alkyl, G.sub.1 und G.sub.2 are halogen, 3-carboxypyridin-1-yl or 3-carbamoylpyridin-1-yl, (Z.sub.1).sub.2-3 is 2 to 3 identical or different fiber reactive radicals, Z.sub.2 and Z.sub.3 are each independently of the other identical or different fiber reactive radicals, and b is the number 0 or 1 wherein the process does not include chrome, vegetable and aldehyde tanning agents.

2. A process according to claim 1, wherein Z.sub.1, Z.sub.2 and Z.sub.3 are each independently of the others a radical of the formula ##STR00032## in which Hal is chlorine or bromine; X.sub.1 is halogen, 3-carboxypyridin-1-yl or 3-carbamoylpyridin-1-yl; T.sub.1 independently has the meaning of X.sub.1, or is a substituent which is not fiber reactive, or is a fiber reactive radical of the formula ##STR00033## in which R.sub.1, R.sub.1a and R.sub.1b independently of one another are each hydrogen or C.sub.1-C.sub.4 alkyl, R.sub.2 is hydrogen, C.sub.1-C.sub.4 alkyl which is unsubstituted or substituted by hydroxyl, sulfo, sulfato, carboxyl or cyano or a radical ##STR00034## R.sub.3 is hydrogen, hydroxyl, sulfo, sulfato, carboxyl, cyano, halogen, C.sub.1-C.sub.4 alkoxycarbonyl, C.sub.1-C.sub.4 alkanoyloxy, carbamoyl or the group SO.sub.2Y, alk and alk.sub.1 independently of one another are linear or branched C.sub.1-C.sub.6 alkylene, arylene is a phenylene or naphthylene radical which is unsubstituted or substituted by sulfo, carboxyl, C.sub.1-C.sub.4alkyl, C.sub.1-C.sub.4alkoxy or halogen, Q is a radical O or NR.sub.1, in which R.sub.1 is as defined above, W is a group SO.sub.2NR.sub.2, CONR.sub.2 or NR.sub.2CO, in which R.sub.2 is as defined above, Y is vinyl or a radical CH.sub.2CH.sub.2U and U is a group which can be split off under alkaline conditions, Y.sub.1 is a group CH(Hal)-CH.sub.2-Hal or C(Hal)CH.sub.2 and Hal is chlorine or bromine and l and m independently of one another are an integer from 1 to 6 and n is the number 0 or 1; and X.sub.2 is halogen or C.sub.1-C.sub.4 alkylsulfonyl; X.sub.3 is halogen or C.sub.1-C.sub.4 alkyl; and T.sub.2 is hydrogen, cyano or halogen.

3. A process according to either claim 1 or claim 2, wherein Z.sub.1, Z.sub.2 and Z.sub.3 are each independently of the others a radical of the formula (3a), (3b) or (3f) according to claim 2, in which Y is vinyl, -chloroethyl or -sulfatoethyl, R.sub.1a is hydrogen, I is the number 2 or 3, X.sub.1 is halogen, T.sub.1 is C.sub.1-C.sub.4 alkoxy, C.sub.1-C.sub.4 alkylthio, hydroxyl, amino, N-mono- or N,N-di-C.sub.1-C.sub.4 alkylamino which are unsubstituted or substituted in the alkyl moiety by hydroxy, sulfato or sulfo, morpholino, phenylamino or NC.sub.1-C.sub.4 alkyl-N-phenylamino which are unsubstituted or substituted in the phenyl ring by sulfo, carboxy, acetylamino, chlorine, methyl or methoxy and in which the alkyl is unsubstituted or substituted by hydroxy, sulfo or sulfato, or naphthylamino which is unsubstituted or substituted by 1 to 3 sulfo groups, or T.sub.1 is a fiber reactive radical of the formula ##STR00035## in which Y is as defined above and Y.sub.1 is a group CH(Br)CH.sub.2Br or C(Br)CH.sub.2.

4. A process according to claim 1 wherein B is a C.sub.2-C.sub.6 alkylene radical, which may be interrupted by 1, 2 or 3 O members and is unsubstituted or substituted by hydroxyl, or phenylene substituted by one or two sulfo groups, and G.sub.1 and G.sub.2 are each independently of the other chlorine or fluorine.

5. A process according to claim 1 wherein A.sub.1 A.sub.2 and A.sub.3 are each independently of the others a monoazo or polyazo chromophore.

6. A process according to claim 1 wherein A.sub.1, A.sub.2 and A.sub.3 are each independently of the others a radical of the formula ##STR00036## wherein (R.sub.4).sub.0-3 denotes from 0 to 3 identical or different substituents from the group C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, C.sub.2-C.sub.4 alkanoylamino, ureido, sulfamoyl, carbamoyl, sulfomethyl, halogen, amino, hydroxy, carboxy and sulfo, (R.sub.5).sub.0-2 denotes from 0 to 2 identical or different substituents from the group hydroxy, amino, N-mono-C.sub.1-C.sub.4 alkylamino, N,N-di-C.sub.1-C.sub.4alkylamino, C.sub.2-C.sub.4 alkanoylamino and benzoylamino, and q in formula (5) is the number 2 or 3, that is q depicts 2 or 3 bonds attached to the chromophore; ##STR00037## wherein (R.sub.5).sub.0-2 is as defined above, and q in formula (6) is the number 2 or 3, that is q depicts 2 or 3 bonds attached to the chromophore; ##STR00038## wherein (R.sub.6).sub.0-3 and (R.sub.7).sub.0-3 independently of the other denotes from 0 to 3 identical or different substituents from the group C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, halogen, carboxy and sulfo, and q in formula (7) is the number 2 or 3, that is q depicts 2 or 3 bonds attached to the chromophore; ##STR00039## wherein R.sub.8 and R.sub.10 are each independently of the other hydrogen, C.sub.1-C.sub.4 alkyl or phenyl, R.sub.9 hydrogen, cyano, carbamoyl or sulfomethyl, and q in formula (8) is the number 2 or 3, that is q depicts 2 or 3 bonds attached to the chromophore; ##STR00040## wherein (R.sub.11).sub.0-3 is as defined for (R.sub.4).sub.0-3, (R.sub.12).sub.0-3 denotes from 0 to 3 identical or different substituents from the group C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, halogen, amino, carboxy and sulfo, (R.sub.13).sub.0-3 is as defined for (R.sub.4).sub.0-3, or R.sub.13 is a radical NN-Ph, wherein Ph is phenyl that is unsubstituted or substituted by C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, halogen, carboxy or sulfo, s is the number 0 or 1, and q in formula (9) is the number 2 or 3, that is q depicts 2 or 3 bonds attached to the chromophore; ##STR00041## wherein (R.sub.11).sub.0-3 and (R.sub.13).sub.0-3 independently of the other are as defined above, (R.sub.14).sub.0-2 denotes from 0 to 2 identical or different substituents from the group C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, halogen, carboxy, sulfo, hydroxyl, amino, N-mono-C.sub.1-C.sub.4 alkylamino, N,N-di-C.sub.1-C.sub.4 alkylamino, C.sub.2-C.sub.4 alkanoylamino and benzoylamino, and q in formula (10) is the number 2 or 3, that is q depicts 2 or 3 bonds attached to the chromophore; ##STR00042## wherein the benzene nuclei do not contain any further substituents or are further substituted by C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, C.sub.1-C.sub.4 alkylsulfonyl, halogen or by carboxy, and q is the number 2 or 3, that is q depicts 2 or 3 bonds attached to the chromophore; ##STR00043## wherein Pc is the radical of a metal phthalocyanine, W is OH and/or NR.sub.16R.sub.16 and R.sub.16 and R.sub.16 are each independently of the other hydrogen or C.sub.1-C.sub.4 alkyl that is unsubstituted or substituted by hydroxyl or by sulfo, R.sub.15 is hydrogen or C.sub.1-C.sub.4 alkyl, A is a phenylene radical that is unsubstituted or substituted by C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, halogen, carboxy or by sulfo, or is a C.sub.2-C.sub.6 alkylene radical, k is from 1 to 3, and q is the number 2 or 3, that is q depicts 2 or 3 bonds attached to the chromophore; or ##STR00044## wherein A is a phenylene radical that is unsubstituted or substituted by C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, halogen, carboxy or by sulfo, or is a C.sub.2-C.sub.6 alkylene radical, r independently is the number 0, 1 or 2, and v and v are each independently of the other the number 0 or 1.

7. A process according to claim 6, wherein A.sub.1, A.sub.2 and A.sub.3 are each independently of the others a radical of formula (5), (6), (9) or (10).

8. A process according to claim 1 wherein the collagen containing fibrous material is treated with a liquor containing at least one reactive dyestuff of formula (1).

9. A process according to claim 8, wherein the collagen containing fibrous material is treated with a liquor containing at least one reactive dyestuff of formula
A.sub.1a-(Z.sub.1).sub.2-3 (1a) together with at least one reactive dyestuff of formula
A.sub.1b-(Z.sub.1).sub.2 (1b), wherein A.sub.1a is a radical of formula ##STR00045## A.sub.1b is a radical of the formula ##STR00046## wherein (R.sub.11).sub.0-3 denotes from 0 to 3 identical or different substituents from the group C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, C.sub.2-C.sub.4 alkanoylamino, ureido, sulfamoyl, carbamoyl, sulfomethyl, halogen, amino, hydroxy, carboxy and sulfo, (R.sub.12).sub.0-3 denotes from 0 to 3 identical or different substituents from the group C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, halogen, amino, carboxy and sulfo, (R.sub.13).sub.0-3 is as defined for (R.sub.11).sub.0-3, or R.sub.13 is a radical NN-Ph, wherein Ph is phenyl that is unsubstituted or substituted by C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, halogen, carboxy or sulfo, (R.sub.14).sub.0-2 denotes from 0 to 2 identical or different substituents from the group C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4alkoxy, halogen, carboxy, sulfo, hydroxyl, amino, N-mono-C.sub.1-C.sub.4 alkylamino, N,N-di-C.sub.1C.sub.4 alkylamino, C.sub.2-C.sub.4alkanoylamino and benzoylamino, s is the number 0 or 1, q is the number 2 or 3, that is q depicts 2 or 3 bonds attached to the chromophore, and Z.sub.1 independently denotes 2 or 3 identical or different fiber reactive radicals of formula
SO.sub.2Y (3a)
or
NHCO(CH.sub.2).sub.lSO.sub.2Y (3b), wherein Y is vinyl, -chloroethyl or -sulfatoethyl, and I is the number 2, 3 or 4.

10. A process according to claim 1 wherein the amount of the at least one reactive dyestuff is in the range of from 1.0% to 10% based on the pickle weight of the collagen containing fibrous material.

11. A process according to claim 1 wherein fixing further comprises increasing the temperature of the aqueous liquor to not more than 50 C.

12. A process according to claim 1 wherein fixing is conducted in the presence of at least one inorganic salt.

13. A process according to claim 1 wherein fixing is conducted in the presence of at least one salt of a carboxylic acid.

14. The leather or the leather imitation obtained by the process according to claim 1.

15. The process according to claim 6, wherein Pc is the radical of a copper or nickel phthalocyanine and r is independently 0 or 1.

16. The process according to claim 12, wherein the inorganic salt is sodium sulphate (Glauber salt) or potassium sulphate.

17. The process according to claim 13, wherein the carboxylic acid is sodium formate or tetrasodium ethylenediaminetetraacetic acid (EDTA).

18. The process according to claim 1, wherein the aqueous liquor has a pH below 7.

19. The process according to claim 1, wherein the aqueous liquor has a pH of 8.5 or less.

20. The process according to claim 1, wherein the aqueous liquor has a pH below 7, and fixing comprises increasing the pH of the aqueous liquor to at least 10.

Description

EXAMPLE 1

(1) Tanning and Dyeing:

(2) Though it would not be typical to start from the pickle for conducting the process of the present invention, the pickled product is used, as pelt can be held in a preserved state at this point. The pickled goatskin is neutralized with 150% of a NaCl solution (8%) in water containing 0.15% of Eusapon OC (degreasing agent of BASF) and 1.5% of sodium bicarbonate and run overnight. The pH of the liquor is in the range of 5.0 to 5.4. The pickled goatskin thus treated is drained, washed two times with 100% of water at pH 5.0 to remove sodium chloride used for depickling the skin and the loosened natural grease, other salts and proteinous debris which is loose in the structure. The washed goatskin is introduced into a drum containing 30% of water at a temperature of 30 C., the pH is adjusted to pH 5.0 and 3% of a dye mixture are added containing 81 parts of the dye of formulae (10 g) and 19 parts of the dye of formula (9b). The drum is operated for 90 minutes to achieve dye penetration. Subsequently, 8% of sodium sulphate are added and the drum is operated for another 30 minutes. Afterwards, aqueous solutions of sodium carbonate (soda ash) and sodium bicarbonate are added stepwise as follows: (i) 0.5% of sodium bicarbonate in 5% of water, run drum for 10 minutes; (ii) 0.5% of sodium bicarbonate in 5% of water, run drum for 10 minutes; (iii) 0.25% of sodium carbonate in 5% of water, run drum for 10 minutes; (iv) 0.25% of sodium carbonate in 5% of water, run drum for 10 minutes; (v) 0.25% of sodium carbonate in 20% of water, run drum for 10 minutes. Then, the temperature of the liquor is increased to 40 C. The pH is maintained at 8.8 to 9.0 by periodically checking and adjusting with sodium carbonate. The drum is operated for another 6 hours. The goatskin thus treated is drained, washed with 100% of water at 35 C. for 20 minutes with two additions of 1% of formic acid (10% solution) to drop the pH to 7.5. The treated and washed goatskin is then subjected to a wash step with an aqueous bath containing ERIOPON WFE for 20 minutes, drained, and washed with fresh water for 10 minutes. The goatskin thus treated is allowed to age for 24 hours. A black dyed and tanned leather is obtained which exhibits a hydrothermal stability of 84 C. and a fastness to water and fastness to perspiration of 5.

(3) Retanning:

(4) The dyed and tanned leather is immersed in 150% of water at 45 C. and three portions of formic acid are added to adjust a pH of 5.2 to 5.5. The leather thus treated is drained and washed, and then immersed in 75% of water at 40 C. 8% of a commercially available sulphone based syntan are added, and the immersed leather is treated for 30 minutes, followed by the addition of 10% of commercially available anionic fatliquors and further treatment for 60 minutes. Formic acid is successively added over a period of 55 minutes to yield a pH of 3.0 to 3.3. Treatment is continued at this pH for further 30 minutes. The product is drained and washed in a clean liquor, then drained and stored for 24 hours prior to drying.

EXAMPLES 2 to 14

(5) The procedure of Example 1 is repeated except that the amount of a dyestuff or a dye mixture as given in Examples 2 to 14 is used instead of 3% of the dye mixture given in Example 1.

(6) Example 2: 3% of a dye mixture containing 67 parts of the dye of formulae (10f), 17 parts of the dye of formula (9m) and 16 parts of a mixture of the dyes of formulae (10a), (10b), (10c) and (10d). A black dyed and tanned leather is obtained which has a hydrothermal stability of 83 C.

(7) Example 3: 3% of a dye mixture containing 74 parts of the dye of formulae (10f), 15 parts of the dye of formula (9a) and 11 parts of the dye of formula (10e). A black dyed and tanned leather is obtained which has a hydrothermal stability of 82 C.

(8) Example 4: 3% of a dye mixture containing 78 parts of the dye of formulae (10f) and 22 parts of the dye of formula (9a). A black dyed and tanned leather is obtained which has a hydrothermal stability of 85 C.

(9) Example 5: 3% of a dye of the formula (9b). An orange to orange-brown dyed and tanned leather is obtained which has a hydrothermal stability of 85 C.

(10) Example 6: 3% of a dye of the formula (10x). A scarlet dyed and tanned leather is obtained which has a hydrothermal stability of 86 C.

(11) Example 7: 3% of a dye of the formula (6a). A red dyed and tanned leather is obtained which has a hydrothermal stability of 84 C.

(12) Example 8: 3% of a dye of the formula (202). A yellow dyed and tanned leather is obtained which has a hydrothermal stability of 86 C.

(13) Example 9: 3% of a dye of the formula (10e). A red dyed and tanned leather is obtained which has a hydrothermal stability of 79 C.

(14) Example 10: 3% of a dye of the formula (9m). An orange dyed and tanned leather is obtained which has a hydrothermal stability of 80 C.

(15) Example 11: 3% of a dye of the formula (9a). An orange to orange-brown dyed and tanned leather is obtained which has a hydrothermal stability of 80 C.

(16) Example 12: 3% of a dye of formula (10f). A navy-black dyed and tanned leather is obtained which has a hydrothermal stability of 82 C.

(17) Example 13: 3% of a dye of formula (10g). A navy dyed and tanned leather is obtained which has a hydrothermal stability of 83 C.

(18) Example 14: 3% of a dye of formula (10o). A navy dyed and tanned leather is obtained which has a hydrothermal stability of 81 C.

EXAMPLE 15

(19) Tanning and Dyeing:

(20) Pickled goatskin is neutralized with 150% of a NaCl solution (8%) in water containing 1.5% of sodium bicarbonate and run overnight. The pH of the liquor is in the range of 5.4 to 5.6. The pickled goatskin thus treated is drained, washed two times with 100% of water at pH 5.5 to remove sodium chloride used for depickling the skin and the loosened natural grease, other salts and proteinous debris which is loose in the structure. The washed goatskin is introduced into a drum containing 30% of water at a temperature of 30 C., the pH is adjusted to pH 5.5, and 3.5% of a dye mixture are added containing 81 parts of the dye of formulae (10g) and 19 parts of the dye of formula (9b). The drum is operated for 90 minutes to achieve dye penetration. Subsequently, 8% of tetrasodium ethylenediaminetetraacetic acid (EDTA) are added and the drum is operated for another 30 minutes. Afterwards, aqueous solutions of sodium carbonate (soda ash) and sodium bicarbonate are added stepwise as follows: (i) 3% of sodium bicarbonate in 15% of water are added in multiple additions over 30 minutes, and (ii) 2% of sodium carbonate in 15% of water are added in multiple additions over 30 minutes. Then, the temperature of the liquor is increased to 35 C. The pH is maintained at 8.9 to 9.1 by periodically checking and adjusting with sodium carbonate. The drum is operated for another 8 hours. The goatskin thus treated is drained, washed with 150% of water at 40 C. for 20 minutes, and drained, washed again with 100% of water with an addition of 1.5% of citric acid and 1.0% trisodium citrate for 30 minutes to drop the pH to approximately 6.0. The treated and washed goatskin is then subjected to a final drain, wash step with 100% of water for 15 minutes. The goatskin thus treated is allowed to age for 24 hours. A black dyed and tanned leather is obtained which exhibits a hydrothermal stability of 84 C.

(21) Retanning:

(22) The dyed and tanned leather is immersed in 75% of water at 50 C. and 8% of a commercially available sulphone based syntan are added. The immersed leather is treated for 30 minutes, followed by the addition of 1% of a commercially available filling agent and 10% of commercially available anionic fatliquors suitable for highly anionic leather. Treatment is continued for 45 minutes. Fixation of these agents is accomplished by adding portions of formic acid over a period of 120 minutes to adjust a pH of 3.0 to 3.3. Treatment is continued for another 30 minutes. The leather thus treated is drained and washed for 15 minutes with 100% of water at 50 C. Afterwards, the leather is drained and treated for 30 minutes at 30 C. by adding 75% of water and 1% of ALBAFIX ECO of Huntsman. The product is drained and stored for 24 hours prior to drying.

EXAMPLE 16

(23) Tanning and Dyeing:

(24) Pickled bovine hide is neutralized with 150% of a NaCl solution (8%) in water containing 3% of sodium bicarbonate and run overnight. The pH of the liquor is in the range of 6.8 to 7.0. The pickled bovine hide thus treated is drained, washed two times with 100% of water at pH 5.5 to remove sodium chloride used for depickling the hide and the loosened natural grease, other salts and proteinous debris which is loose in the structure. The washed bovine hide is then further treated in a fresh float of 100% water and 2% sodium bicarbonate and run for a period of 3 hours in order to gain a pH of 7.8 to 8.0 through the cross-section of the hide. The treated bovine hide is then drained and washed once with 100% water to remove the alkaline sodium bicarbonate, but still leave the bovine hide at pH8.0. The bovine hide is then introduced into a drum containing 15% of water at a temperature of 35 C., and 4.75% of a dye mixture are added containing 75 parts of the dye of formulae (10g) and 25 parts of the dye of formula (9b). The drum is operated for 90 minutes to achieve dye penetration. Subsequently, 5% of sodium sulfate and 2.5% of sodium formate are added and the drum is operated for another 30 minutes. Afterwards, aqueous solutions of sodium carbonate (soda ash) and sodium bicarbonate are added stepwise as follows: (i) 2% of sodium bicarbonate in 15% of water are added in multiple additions over 30 minutes, and (ii) 1% of sodium carbonate in 15% of water are added in multiple additions over 30 minutes. The pH is maintained at 8.9 to 9.1 by periodically checking and adjusting with sodium carbonate. The drum is operated for another 8 hours. The bovine hide thus treated is drained, washed with 150% of water and 3% sulfuric acid at 40 C. for 20 minutes to reduce the pH to 7.0 to 7.2, and drained, washed again with 100% of water with an addition of 0.5% sulfuric acid for 30 minutes to drop the pH to approximately 6.0. The treated and washed hide is then subjected to a final drain, wash step with 100% of water for 15 minutes. The hide thus treated is allowed to age for 24 hours. A black dyed and tanned leather is obtained which exhibits a hydrothermal stability of 80 C.

EXAMPLE 17

(25) Tanning and Dyeing:

(26) This example 17 demonstrates the processing as if the hide or skin were beginning the process after the bating stage, wherein the hide or skin already has a cross-sectional pH of 8.0 and is free of any divalent cations or other species that could interfere in the tanning process. The bovine hide is introduced into a drum containing 15% of water at a temperature of 35 C., and 4.5% of a dye mixture are added containing 78 parts of the dye of formulae (10g) and 22 parts of the dye of formula (9b). The drum is operated for 90 minutes to achieve dye penetration. Subsequently, 5% of sodium sulfate and 2.5% of sodium formate are added and the drum is operated for another 30 minutes. Afterwards, aqueous solutions of sodium carbonate (soda ash) and sodium bicarbonate are added stepwise as follows: (i) 1.5% of sodium bicarbonate in 15% of water are added in multiple additions over 30 minutes, and (ii) 1% of sodium carbonate in 15% of water are added in multiple additions over 30 minutes. The pH is maintained at 8.9 to 9.1 by periodically checking and adjusting with sodium carbonate. The drum is operated for another 8 hours. The bovine hide thus treated is drained, washed with 150% of water and 3% sulfuric acid at 40 C. for 20 minutes to reduce the pH to 7.0 to 7.2, and drained, washed again with 100% of water with an addition of 0.5% of a commercial soaping or afterclearing agent, for example, ERIOPON WFE of Huntsman, for 30 minutes. The treated and washed hide is then subjected to a final drain, wash step with 100% of water for 15 minutes. The hide thus treated is allowed to age for 24 hours. A black dyed and tanned leather is obtained which exhibits a hydrothermal stability of 80 C.

(27) Retanning for Methods 16 and 17:

(28) The dyed and tanned leather is immersed in 50% of water at 30 C. and 4% of a commercially available sulphone or diphenyl based syntan are added and 4% of commercially available vegetable tanning material, e.g. Tara. The immersed leather is treated for 30 minutes, followed by the addition of 3% of a commercially available filling agent and 15% of commercially available anionic fatliquors suitable for highly anionic leather with a further offer of 50% water at 50 C. Treatment is continued for 45 minutes. Fixation of these agents is accomplished by adding portions of formic acid over a period of 60 minutes to adjust a pH of 3.0 to 3.3. Treatment is continued for another 30 minutes. The leather thus treated is drained and washed for 15 minutes with 100% of water at 50 C. The product is drained and stored for 24 hours prior to drying.