US3920385A

US3920385A - Process for dyeing leather

Info

Publication number: US3920385A
Application number: US373836A
Authority: US
Inventors: Fritz Bohny; Willi Egli; Max Schwank
Original assignee: Ciba Geigy AG
Current assignee: Novartis AG
Priority date: 1970-03-04
Filing date: 1973-05-03
Publication date: 1975-11-18
Anticipated expiration: 1992-11-18

Abstract

A process for dyeing leather, which comprises treating the leather with either A. AN AQUEOUS DYESTUFF SOLUTION THAT OPTIONALLY CONTAINS A WATER-MISCIBLE ORGANIC SOLVENT AND/OR A WETTING AGENT AND DISPERSING AGENT, B. A SOLUTION OF A DYESTUFF IN AN ORGANIC SOLVENT OR A MIXTURE OF ORGANIC SOLVENTS, OR C. AN AQUEOUS OR ORGANIC DISPERSION OF A DYESTUFF, EXPRESSING THE DYEING LIQUOR FROM THE DYED LEATHER, AND SUBSEQUENTLY DRYING THE LEATHER OR SUBJECTING THE LEATHER TO A FIXING PROCESS AND THEN DRYING IT.

Description

United States Patent 1191 Bohny et a1.

n] 3,920,385 Nov. 18, 1975 PROCESS FOR DYEING LEATHER [75] Inventors: Fritz Bohny, Basel; Willi Egli,

Reinach; Max Schwank, Basel, all of Switzerland [73] Assignee: Ciba-Geigy AG, Basel, Switzerland [22] Filed:

[21] Appl. No.: 373,836

May 3, 1973 Related US. Application Data [63] Continuation of Ser. .No. 121,164, March 4, 1971, I

abandoned.

[30] Foreign Application Priority Data- Mar. 4, 1970 Switzerland 3133/70 Jan. 15, 1971 Switzerland 625/71 [52] US. Cl. 8/12; 8/l2.5; 8/13 [51] Int. CI. D06P 3/32; D06P 5/QO; D06P 3/12;

[58] Field of Search 8/12, 12.5, 13

[56] References Cited I UNITED STATES PATENTS 9/1956 Meyer et al 8/12 3,414,366 12/1968 Nordstrom et al 8/12 3,472,605 10/1969 Wicki et a1. 8/12 FOREIGN PATENTS OR APPLICATIONS 1,069,574 5/1967 United Kingdom 8/12 737,865 2/1970 Belgium 8/12 Primary Examiner-Benjamin R. Padgett Assistant Examiner-T. S. Gron Attorney, Agent, or F irmJoseph G. Kolodny; Edward McC. Roberts; Prabodh l. Almaula [57] ABSTRACT expressing the dyeing liquor from the dyed leather, and subsequently drying the leather or subjecting the leather to a fixing process and then drying it.

Compared to the known method of dyeing leather in the vat, that is to say in a closed rotating drum in which the leather material is exposed to severe mechanical stress for a prolonged period, for example for 1 hour, the process of the present invention offers considerable advantages. The process of the invention treats the materials very gently: because of the short dyeing time, the stage of washing or rinsing the dyed goods is dispensed with, and furthermore the process can be carried out continuously, so that the material throughput can be considerably increased and the auxiliaries and apparatus required for the process are less expensive.

Compared to the process described in German Pat. Nos. 1,226,529 and 1,287,556, the present process has the advantage of greater simplicity since, according to the present process, dyeing is no longer carried out in a complicated aqueous two-phase system, but in a singlephase solvent system which is simple to manufacture. The presence of one or more organic solvents in the dyeing solution renders the dyestuffs more soluble, leads to better, that is to say more rapid, wettability of the leather to be dyed and effects a rapid and deep penetration of the dyestuff into the leather. The shortening of the dyeing time thereby achieved at the same time permits dyeing at a higher temperature, which makes the dyeing process even more effective. In the method of dyeing in the vat, in particular, the use of high temperatures is not possible since, as a resultof the longer dyeing time and the mechanical stress, damage to the leather cannot be avoided at higher temperatures. For the processes described in the German specifications mentioned above, dyeing temperatures of 50 solutions containing organic solvents.

An aqueousdyestuff solution that contains an organic, water-miscible solvent is a preferred dyeing solution. Depending on the proportion of the organic solvent in the aqueous solution, the dyestuff or the solution penetrates more or less rapidly and deeply into the leather material. If the dyeing solution contains a sufficient amount of organic solvent, the speed of penetration is so great that very short dyeing times, for example 5 to seconds, suffice. If additionally the tempera- -ture of the dyeing solution is raised, dyeing times of up to 5 seconds may suffice to achieve a good colour intensity. As examples of water-miscible organic solvents that are suitable for use as an additive to the aqueous dyestuff solutions,there may be mentioned: methanol, ethanol, propanol, butanol, ethylglycol, methoxyethyl alcohol, glycerol, acetone, dimethylformamide, tetrahydrofurane, and especially isopropanol.

If a wetting agent and dispersing agent is added to the aqueous dyeing solution, the amount of the organic solventcan be reduced, or the organic solvent can be omitted entirely, without having to lengthen the dyeing times. Suitable wetting agents and dispersing agents are, for example, reaction products of higher-molecular fatty acids with hydroxyalkylamines and, optionally, ethylene oxide.

If a dyeing solution that only contains one or more organic solvents is used for the process according to the invention, it is of course necessary to use a solvent or solvent mixture that is capable of dissolving the dyestuff concerned, for example acetone for acetone-soluble dyestuffs. Depending on the nature of the dyestuffs used, entirely different solvents will thus be employed,

for example ethanol, ether, petrol, benzene, chloroform, carbon disulfide turpentine oil, carbon tetrachloride, trichloroethylene, ethyl acetate or butyl acetate. However, pigment dyestuffs that are used in a dispersed form in. suitable solvents, for example those mentioned above, or in liquid lacquers, that contain, for example,

linseed oil, turpentine oil, ethanol, benzene, butyl acetate, amyl acetate, ether, acetone or petrol as solvents,

can also be used for the process according to the invention.

Possible dyestuffs are all those that are suitable for dyeing leather,- for example, reactive dyestuffs, acid wool dyestuffs, liquid cationic dyestuffs and especially metal complex dyestuffs. As trade names of such dyestuffs, there may be mentioned Cibalene, Lanasol, Cibacron, Procion and Levafix dyestuffs.

It is important that the dyestuff should be used in a concentrated form which is as pure as possible, that is to say it should contain as little as possible in the way of diluents (cutting agents or extenders), for example inorganic salts, such as sodium sulphate, sodium chloride or dextrins, or 'wetting agents and dispersing agents, since the leather is no longer washed or rinsed after dyeing, and the cutting agents or extenders are hence no longer removed.

After removing the dyed leather from the bath, the excess dyeing liquor is expressed from it as thoroughly as possible. Thereafter, the dyed material is further processed in the usual manner by drying it, or fixing and drying it. The fixing can be carried out in a manner known per se, for example, by the cold padbatch method in the case of reactive dyestuffs. Drying is also carried out in a manner known per se, for example in an infra-red drying oven or vacuum drier. In some cases it is advantageous if the dyed material is stored for some time, for example for l to 24 hours, after expressing the dyeing solution and before further processing. Possible leathers that may be dyed are all varieties of leather, and especially chrome leather.

Because of the very short dyeing times that are possible, as already mentioned, the process according to the invention can also be carried out continuously, so that the processes of immersing the leather into the dyebath,,removing it, expressing it and treating it further are carried out in a continuous process with a constant feeding-in of material. A suitable dyeing device is a trough containing the dyeing solution, through which the leather material to be dyed is moved by means of a conveyor device, for example a conveyor belt. A suitable expression device is a roll-padder into which the leather material is fed by the conveyor belt immediately after leaving the dyebath, and in which the bulk of the dyeing liquor retained in the dyed leather is expressed. The subsequent drying, or fixing and drying, of the dyed material is effected with the aid of devices known in dyeing technology that can also run automatically. In this way, a piece of leather can pass within a few minutes through the entire processing sequence in the combined dyeing-padderdrying arrangement. If dyeing solutions are used that only contain organic solvents, it is advisable to carry out the process according to the invention in a closed device, in order to avoid objectionable odours or hazards from solvent vapours. Furthermore, it is highly advantageous that the solvent vapours produced when drying the dyed leather should be condensed, in order to recover the solvents.

In the following Examples the parts, unless otherwise stated, are parts by weight, and the percentages are percentages by weight.

EXAMPLE 1 A dyestuff solution is prepared by dissolving 10 parts of the mixed chromium complex dyestuff which contains one molecule of the dyestuff of the formula and one molecule of the dyestuff of the formula HO CH5 H on N=N O bonded as a complex to one atom of chromium, in 785 parts of water, 200 parts of isopropyl alcohol and 5 parts of 85 strength formic acid.

Buffed side leather which has been chrome and vegetable re-tanned is continuously impregnated in a trough containing the dyestuff solution described above, using a dwell time of seconds at a temperature of 60C, taken out of the trough and expressed between two squeeze rollers, to a dyestuff solution uptake of about 80 of its weight, and dried in a vacuum drier. Brown shades that are level in colour and uniform in colour shade are thus obtained.

EXAMPLE 2 Chrome-tanned suede leather can be dyed red in the 4 manner described in Example 1 if the following solution is used with a dwell time of 8 seconds, a temperature of C and 70 solution uptake: a dyestuff solution of l2.-parts of the 1:2 chromium complex of the dyestuff of the formula HQ 0 H OH 3 c rr N=N -c l l N 0 s 1 936 parts of water, 50 parts of isopropanol/ethylglycol (1:1) and 20 parts of the product obtained as follows:

420 g of technical oleic acid (1.5 mols), 345 g of diethanolamine (3.35 mols) and 1.5 g of p-toluene-sulphonic acid are kept under nitrogen at 160to 165C, in a 1 litre round-bottomed flask equipped with a stirrer, thermometer and descending condenser, until 27 to 28 ccs of water have collected in the ice-cooled receiver. 740 g of the reaction product are obtained.

After drying the dyed leather by hanging up in a drying chamber at 50C, a level red dyeing is obtained.

EXAMPLE 3 .As in Example 1, but observing the following conditions: chrome and vegetable re-tanned full grain side leather, dwell time 6 seconds at 65C and dyestuff solution uptake Dyestuff solution of 12 parts of the dyestuff of the formula 10 parts of 85% strength formic acid, 878 parts of water and parts of isopropanol/ethanol (1:1). Drying on a vacuum drier.

, EXAMPLE 4 As in Example 1, but observing the following conditions: chrome-tanned nubuk leather, dwell time 5 seconds at 70C and dyestuff solution uptake 80%. Dyestuff solution of 15 parts of the dyestuff of the formula obtained.

' and one molecule of the dyestuff of the formula 30 parts of the reaction product of'oleic acid and-diethanolamine describedin" Example 2,5755 parts of water and 200 parts of isopropanol; subsequent fixing in a padder at 50" c using a mixture of 30 parts of-a'dicyandiamide-fonnaldehyde condensation T product, 10 parts of 85% strength formic acid and 960 parts of water, and drying on a stretching fr'ameyRed dyeings are OH HO I HIl (JO-CH bonded as a complex to one atom of chromium is used and topping is carried out on a padder with 5 parts of a mixture of 20 parts of Methylene Blue, 34 parts of Bismarck Brown, and 46 parts of Meldolas Blue (Cl.

I Basic Blue 6), 20 parts of 80% strength acetic acid, 875 parts of water and 100 parts of ethanol. Black shades are obtained.

EXAMPLE 6 stuff from B-naphthylamine and diazotised 5-nitro-2- aminophenol, 200 parts of ethyl acetate, 500 parts of 6 ethylglycol, 240 parts of isopropyl alcohol, 40 parts of -vinyl copolymer and 10 parts of acrylate polymer. Subsequent drying. Black shades are thus obtained.

EXAMPLE 7 parts of the 1:2 cobalt mixed complex dyestuff which contains one molecule of the azo compound of the formula Cl NH and one molecule of the azo compound of the formula 0H HO bonded to one atom of cobalt, and 10 parts of a levelling agent, are dissolved in 970 parts of water.

Chrome-tanned and synthetics-vegetable retanned side leather is impregnated, for a dwell time of 12 seconds and at a temperature of 70C, in a trough which contains the dyeing solution described above, and is expressed to a 70 liquor uptake and dried in a vacuum drier. A level claret-coloured leather is obtained.

EXAMPLE 8 A dyestuff solution is prepared from 20 parts of the 1:1 cobalt complex dyestuff of the monoazo compound obtained by coupling diazotised 2-amino-4-nitrophenol with acetoacetanilide, 10 parts of a levelling agent, 100 parts of ethylglycol and 870 parts of water.

Chrome-synthetics-tanned side leather is dyed in this solution, as described in Example 1, using a dwell time of 10 seconds in a bath at C. The leather is then expressed to a liquor uptake and is dried in a vacuum drier at C. A yellow-coloured leather is obtained.

We claim:

1. In a process for dyeing leather by a single treatment of the leather with a dye liquor which is an organic-solvent solution of a dyestuff, expressing the liquor from the dyed leather immediately upon leaving the dye liquor, optionally fixing the dyestuff, and finally drying the dyed leather without prior washing, the improvement which consists essentially of continuously treating the leather, in the substantial absence of mechanical stress, at a temperature of 25 to 80C, for a period of up to 15 seconds, with a liquor of a dyestuff dissolved in a combination of water and a watermiscible organic solvent selected from the group consisting of lower alkanol having 1 to 4 carbon atoms, ethylglycol, methoxyethyl alcohol, glycerol, acetone and tetahydrofuran.

2. The process of claim 1, wherein the watermiscible organic solvent is isopropyl alcohol. 3. The process of claim 1, wherein the liquor further contains a surfactant selected from the group consist- 65 ing of a reaction product of a higher molecular fatty acid with hydroxyalkylamine and a reaction product of higher molecular fatty acid with hydroxyalkylamine and ethylene oxide.

4. The process of claim 1, wherein the dyestuff is a metal complex, reactive, or cationic dyestuff.

5. The process of claim 1, wherein the treatment is carried out for a period of to 10 seconds.

6. The process of claim 1, wherein the treatment is carried out at a temperature in the range of 60 to 80C.

7. The process of claim 1, wherein the dyed leather is stored for a period of l to 24 hours after the step of expressing the dye liquor, and before drying the leather.

8. The process of claim 1, wherein the leather is chrome-tanned leather.

9. In a process for dyeing leather by a single treatment of the leather with a dye liquor which is an organic-solvent solution of a dyestuff, expressing the liquor 10. The process of claim 9, wherein the treatment time is 5 to 10 seconds, and the treatment is carried out at a temperature in the range of to C.

Claims

1. IN A PROCESS FOR DYEING LEATHER BY A SINGLE TREATMENT OF THE LEATHER WITH A DYE LIQUOR WHICH IS AN ORGANIC-SOLVENT SOLUTION OF A DYESTUFF, EXPRESSING THE LIQUOR FROM THE DYED LEATHER IMMEDIATELY UPON LEAVING THE LIQUOR, OPTIONALLY FIXING THE DYESTUFF, AND FINALLY DRYING THE DYED LEATHER WITHOUT PRIOR WASHING, THE IMPROVEMENT WHICH CONSISTS ESSENTIALLY OF CONTINUOUSLY TREATING THE LEATHER, IN THE SUBSTANTIAL ABSENCE OF MECHANICAL STRESS, AT A TEMPERATURE OF 25* TO 80*C, FOR A PERIOD OF UP TO 15 SECONDS, WITH A LIQUOR OF A DYESTUFF DISSOLVED IN A COMBINATION OF WATER AND A WATER MISICIBLE ORGANIC SOLVENT SELECTED FROM THE GROUP CONSISTING OF LOWER ALKANOL HAVING 1 TO 4 CARBON ATOMS, ETHYLGLYCOL, METHOXYETHYL ALCOHOL, GLYCEROL, ACETONE AND TETRAHYDROFURAN.

2. The process of claim 1, wherein the watermiscible organic solvent is isopropyl alcohol.

3. The process of claim 1, wherein the liquor further contains a surfactant selected from the group consisting of a reaction product of a higher molecular fatty acid with hydroxyalkylamine and a reaction product of higher molecular fatty acid with hydroxyalkylamine and ethylene oxide.

5. The process of claim 1, wherein the treatment is carried out for a period of 5 to 10 seconds.

6. The process of claim 1, wherein the treatment is carried out at a temperature in the range of 60* to 80*C.

7. The process of claim 1, wherein the dyed leather is stored for a period of 1 to 24 hours after the step of expressing the dye liquor, and before drying the leather.

8. The process of claim 1, wherein the leather is chrome-tanned leather.

9. IN A PROCESS FOR DYEING LEATHER BY A SINGLE TREATMENT OF THE LEATHER WITH A DYE LIQUOR WHICH IS AN OARGNIC-SOLVENT SOLUTION OF A DYESTUFF, EXPRESSING THE LIQUOR FROM THE DYED LEATHER IMMEDIATELY UPON LEAVING THE DYE LIQUOR, OPTIONALLY FIXING THE DYESTUFF, AND FINALLY DRYING THE DYED LEATHER WITHOUT PRIOR WASHING, THE IMPROVEMENT WHICH CONSISTS ESSENTIALLY OF CONTINUOUSLY TREATING THE LEATHER, IN THE SUBSTANTIAL ABSENCE OF MECHANICAL STRESS, AT A TEMPERATURE OF 25* TO 80*C, FOR A PERIOD OF UP TO 15 SECONDS, WITH A LIQUOR OF DYESTUFF DISSOLVED O IN AN ORGANIC SOLVENT SELECTED FROM THE GROUP CONSISTING OF ACETONE, ETHANOL, ETHER, PETROL, BENZENE, CHLOROFORM, CARBON DISULPHIDE, TURPENTINE OIL, CARBON TETRACHLORIDE, TRICHLOROETHYLENE, ETHYL ACETATE AND BUTYL ACETATE.

10. The process of claim 9, wherein the treatment time is 5 to 10 seconds, and the treatment is carried out at a temperature in the range of 60* to 80*C.