EP0013369B1 - Process for dyeing grain leather - Google Patents

Description

Process for dyeing grain leather with anionic dyes under the conditions customary for exhaust processes in the presence of two specific surfactants. The combined use of the two surfactants improves the levelness and coloration of leather tanned cationically (essentially minerally), and deepens the color of leather tanned or retanned by anionic (synthetic or vegetable) tanning.

• Bei ausschliesslich oder überwiegend kationisch gegerbtem Leder hat man mit Schwierigkeiten hinsichtlich Egalität und Durchfärbung von der Narbenseite her zu kämpfen. Zur Verbesserung werden allgemein die verschiedensten Egalisierhilfsmittel und Tenside eingesetzt. Bei anionisch gegerbtem oder nachgegerbtem Leder liegt die Problematik in der erreichbaren Farbtiefe, weil die kationischen Zentren des Leders bereits mit anionischen Gerbstoffen besetzt sind und daher keine grosse Affinität zum ebenfalls anionischen Farbstoff mehr besteht. Hier schafft der Einsatz kationischer Hilfsmittel Abhilfe. Ein Färbehilfsmittel bzw. Färbeverfahren, das beide Probleme gleichzeitig optimal löst, ist bisher nicht bekannt.

The general problem when dyeing leather with the usual anionic dyes is as follows:

• In the case of exclusively or predominantly cationically tanned leather, one has to struggle with levelness and coloration from the grain side. Various leveling aids and surfactants are generally used for improvement. With anionically tanned or retanned leather, the problem lies in the depth of color that can be achieved, because the cationic centers of the leather are already occupied with anionic tanning agents and therefore there is no longer a great affinity for the likewise anionic dye. The use of cationic aids helps here. A dyeing aid or dyeing process that optimally solves both problems at the same time is not yet known.

The dyeing of leather with acid dyes in the presence of any surfactants is known for example from GB-PS 769174. According to the German patent application B 15087 IVd / 8m published on November 13, 1952, suitable surfactants for this purpose include oxyethylated alcohols or amines, among many others. There is no mention of any mixture of the two.

According to DE-PS 667744, GB-PS 705335 and US-PS 2893811, oxyethylated amines are used, inter alia, as leather dyeing aids. Without any special measures, for example intensive milling in a short liquor, the dye penetrates the leather only a little from the grain side in this process. Later scratches on the leather dyed in this way are therefore very annoying.

According to US Pat. No. 3,334,960, combinations of oxyethylated amines and oxyethylated alcohols can also be used as auxiliaries for dyeing nitrogenous fibrous materials by the padding process. An example of this is not given. The dyebath must contain 4 to 30% carboxylic acid, and the dyed goods must be stored in a moist state for 10 minutes to 24 hours after impregnation. The process therefore requires several work steps and is therefore labor-intensive and time-consuming.

From FR-PS 783008 and DE-PS 724494 the use of combinations of oxyethylated alcohols and weakly oxyethylated amines in dyeing fiber material, mainly wool, is already known. However, the use in the dyeing of grain leather does not result in a full color.

The invention was based on the object of developing a simple dyeing process and a dyeing aid for grain leather that solves all of the problems mentioned at the same time, that is to say, with completely or predominantly cationically tanned grain leather to high levelness and good coloration and with anionically tanned or retanned leather at the same time, i.e. . d. in addition to levelness and coloring, also leads to deep shades.

The solution to this problem was found in a method according to claim 1 and its special embodiments according to claims 2 and 3.

According to the invention, one and the same surfactant solution is used for every leather dyeing with anionic dyes, regardless of how the leather was tanned, regardless of and also deeply penetrated dyeings from the grain side, even in rich shades. Previously, different aids had to be used depending on the type of leather.

In the case of cationically tanned leather, the surfactant mixture can be used before the dye or simultaneously with it. Simultaneous addition is preferred. In the case of anionically tanned or retanned leather, the dye is advantageously allowed to run for 5 to 90, preferably 15 to 30 minutes, and the surfactant mixture is then added.

Grain leather has the natural grain, which is known to be more difficult to color and color than the flesh side and as leather with a polished surface.

“Dyeing leather” here means leather dyeing in the narrower sense, that is to say with dyes that attach to the leather fiber, not the finishing of leather with body colors and the varnishing.

Anionic dyes are those with one or more acid residues, mostly sulfonic acid residues. According to Ullmann, Encyclopedia of Technical Chemistry, Volume 11, page 573, these include the following classes of dyes, which are described in more detail on pages 574 and 575 and in particular on the pages mentioned in Volume 4: Acidic Dyes, Native Dyes, Development and Pickling - and metal complex dyes. Thanks to their good fastness properties, they are the most common dyes in leather dyeing.

Cationically tanned leather is essentially leather tanned with mineral tannins. Mineral tannins mainly consist of salts of trivalent chromium, as well as aluminum and tetravalent zircon.

Other salts, e.g. B. of iron, titanium, cerium and tin are indeed useful in principle, but do not play a significant role in practice for technical or economic reasons. The mineral tanning agents are described in more detail in Ullmann, volume 11, pages 604-608. There are also cationic synthetic tanning agents that cited above page 598, and cationic resin tanning agents based on dicyandiamide, which are described above cited page 602. However, their importance takes a back seat to mineral, especially chrome, tannins. The terms “cationic” and “mineral” tannins can therefore largely be considered synonymous for practical purposes.

An anionically tanned or retanned leather means a leather that has been tanned or retanned with vegetable or with anionic synthetic tannins and contains more than 6%, based on the dry weight of the skin, of vegetable and / or anionic synthetic tannins.

Vegetable tanning agents are the oldest tanning agents at all and therefore do not really need to be defined here. The most important are: extracts from the bark of various tree species (especially oak, spruce, mimosa, mangrove), but also from the heartwood (quebracho, chestnut, oak) as well as from leaves and / or petioles (sumac, gambir) or from Fruits (Algarobilla, Bablah, Divi-divi, Myrobalane, Valonea). They are described in more detail in Ullmann, volume 11, pages 585-595.

The anionic synthetic tanning agents consist essentially of the so-called syntans, ie condensates of phenolic and / or sulfonated aromatics with formaldehyde, it being possible for the sulfonation to be carried out before or after the condensation. They are described in Ullmann, volume 11, pages 595-600. The lignin sulfonates described on page 777 are also included. They have in common that they have a more or less pronounced anionic character, which they impart to tanned or retanned leather (if the amount of tanning agent used for retanning is sufficient, i.e. more than about 6% by weight, based on the dry weight) of leather.

Examples of 3- to 120-, preferably 60- to 100-fold, ethoxylated aliphatic alcohols with 9 to 24, preferably 10 to 18 carbon atoms (group a) which can be used according to the invention as surfactant are: the corresponding oxyethylation products of natural tallow fatty alcohol, synthetic tallow fatty alcohol, Cg / C _n oxo alcohol, C ₁₃ / C ₁₅ oxo alcohol.

• Die erfindungsgemässe Tensidmischung kommt zweckmässig in Form einer 10- bis 90-, vorzugsweise 40- bis 80gewichtsprozentigen wässrigen Lösung in den Handel.

The following may be mentioned as examples of the 6- to 80-, preferably 9- to 30-fold, oxyethylated aliphatic primary or secondary amines having 8 to 20, preferably 12 to 18 carbon atoms per alkyl group which can be used according to the invention as a surfactant of group b: the corresponding oxyethylation products of octylamine, nonylamine , Tridecylamine, oleylamine, stearylamine, 2-ethylhexylamine, di-tridecylamine. The dyeing conditions are the usual for extraction processes, ie dyeing in a barrel or dyeing machine for 30 to 180, preferably 60 to 120 minutes at 5 to 60, preferably 20 to 50 ° C., a liquor length of 50 to 500, preferably 100 to 200% and a total amount of surfactant (a + b) of 0.3 to 3, preferably 0.5 to 2%, based on the shaved weight. The weight ratio of oxyethylated alcohol (component a) to oxyethylated amine (component b) is 1: 4 to 4: 1, preferably 2: 1:

• The surfactant mixture according to the invention expediently comes on the market in the form of a 10 to 90, preferably 40 to 80% by weight aqueous solution.

The parts and percentages given in the following examples relate to the weight.

example 1

Two pieces of 100 parts by weight, cut from adjacent parts of a skin, of a 1.5 mm thick cowhide leather, which was chrome-tanned in the usual way, were drummed for 60 minutes at 30 ° C. in 2-part sodium formate and 0.5 part sodium bicarbonate, filled with 100 parts water. The deacidifying liquor then had a pH of 4.8. Now the leather was rinsed with fresh water for 5 minutes. Leather A was then washed in a liquor of 150% length at 50 ° C. with 2 parts of a 70 percent aqueous surfactant mixture and 1 part of the dye 4-chloroaniline, 1,8,3,6-aminonaphthalene disulfonic acid ← 4,4'-diaminodiphenylamine-2 -sulfonic acid → 3-hydroxydiphenylamine treated. The surfactant mixture consisted of 30 parts of a tallow fatty alcohol reacted with 80 mol of ethylene oxide, 40 parts of an oleylamine reacted with 12 mol of ethylene oxide and 30 parts of water. Then 4 parts of a commercial fat oil based sperm oil were added, drummed again for 60 minutes and acidified with 0.5 parts of formic acid. After the leather had been tumbled for another 20 minutes, it was removed from the fleet and finished in the customary manner.

Leather B was treated in the same way, but no surfactant mixture was added to the dyeing liquor.

After the leathers were dried, shaved and pounded, they were assessed. Leather A was dyed through better than leather B.

Example 2

gefärbt. Anschliessend wurde in die Färbeflotte des Leders A 1 Teil der in Beispiel 1 erwähnten Tensidmischung gegeben, während die Färbeflotte des Leders B nicht mit dieser Mischung versetzt wurde.Two pieces of 100 parts by weight, cut from adjacent parts of a skin, of a chrome-tanned cowhide with a folding thickness of 1.5 mm, were filled with 200 parts of water in Wacker kegs with 0.2 parts of 6 ° Be acetic acid and 0.3 parts of the tetrasodium salt of ethylenediaminetetraacetic acid 15 Tumbled at 40 ° C for minutes. The leathers were then deacidified in 100 parts of water with 2 parts of sodium sulfite and 1 part of sodium formate for 60 minutes at 40 ° C. by drumming in a barrel (final pH: 4.9). The leather was then dissolved in 30 parts of water with 6 parts of mimosa extract, 6 parts of sumac extract, 6 parts of a synthetic tanning agent based on phenolsulfonic acid, 1 part of sodium formate, 0.3 part of the tetrasodium salt of ethylenediaminetetraacetic acid and 3 parts of a commercial fatliquor on sperm. oiled for 90 minutes at 40 ° C. The retanned leather was then washed for 10 minutes with 300 parts of 50 ° C warm water. Finally, the leather in 100 parts of water at 50 ° C with 2 parts of the dye consisting of the 1: 1 copper complex of

colored. Subsequently, part of the surfactant mixture mentioned in Example 1 was added to the dyeing liquor of leather A 1, while this mixture was not added to the dyeing liquor of leather B.

The leathers were then drummed for a further 15 minutes and then greased and finished as described in Example 1.

Leather A was dyed significantly deeper than leather B, and the levelness of the dyeing of leather A was also excellent.

In Examples 3 to 6, the procedure was as in Example 1, in Examples 7 to 9 as in Example 2. The results were comparable. See the table below for details.

Claims (3)

1. A process for dyeing grain leather with anionic dyes in the presence of surfactants by dyeing in a drum or dyeing apparatus under the conventional conditions for exhaustion methods, without subsequent moist storage, wherein the surfactant employed is a combination of

a) an aliphatic alcohol of 9 to 24 carbon atoms oxyethylated with from 3 to 120 ethylene oxide units and

b) an aliphatic primary or secondary amine of 8 to 20 carbon atoms per alkyl group oxyethylated with from 6 to 80 ethylene oxide units,

in a weight ratio of a to b of from 1:4 to 4:1, and in a total amount of from 0.3 to 3%, based on the shaved weight.

2. A process for dyeing grain leather as claimed in claim 1, wherein cationically tanned leather is dyed which may contain, in addition to the cationic tanning agent, up to 6%, based on dry weight, of an anionic tanning agent, and the leather is treated with the surfactant combination for from 0 to 30 minutes before being treated with the dye.

3. A process for dyeing grain leather as claimed in claim 1, wherein anionically tanned or retanned leather is dyed, and the leather is treated with the surfactant combination for from 5 to 90 minutes after being treated with the dye.