DE3001301A1 - Mfg. anionically tanned leather for anionic dyeing - by treating with ammonium salt and aldehyde - Google Patents

Abstract

Treatment of anionically tanned or retanned leather prior to dyeing with anionic dyes in aq. soln. is carried out by treating the leather with a NH4 salt (I) and an aldehyde or dialdehyde (II) at a pH of 3-8 (pref. 4.5-6). (I) is suitably (NH4)2SO4, NH4Cl or NH4 formate or acetate. (II) is pref. glutaraldehyde. The treatment is pref. effected at 20-70 (esp. 40-50) deg.C for 10-120 (esp. 20-50) min using 50-200%, based on leather wt., of an aq. soln. contg. (I) and (II) in a (I):(II) equiv. ratio of 1-2:1. The amt. of (I) used is pref. equiv. to 1.5-3 wt.% (NH4)2SO4, based on leather wt. The treatment improves the depth of colour achievable with anionic dyes, giving intense even shades with good fastness.

Description

Process for preparing anionically tanned or

retanned leather The invention relates to a method of preparation of anionically tanned or also retanned leather with anionic dyes in the aqueous phase. The leather is simultaneously with an aldehyde and a Treated ammonium salt. The depth of color that can be achieved during subsequent dyeing becomes thereby significantly improved.

When dyeing anionically tanned or anionically retanned leather with cationic dyes it is known that problems arise with regard to levelness, the color penetration and the lightfastness. When dyeing the same leather with anionic As is well known, dyes are obtained in relatively pale shades. This is where the effort creates cationic aid remedy. Amines, amides and quaternaries, among others, come as such Ammonium salts into consideration. These can also be in the form of surfactants or water-soluble ones Resins are used. It is generally disadvantageous that these products due to their high affinity for the anionically charged leather on the leather surface are bound and not penetrate into its deeper layers.

During dyeing, the dye then becomes cationic at the same time charged surface deposited. The result is, among other things, unequal and insufficient Rubbing fastness of the dye. The latter leads to difficulties in subsequent adjustments regarding their liability. This can be remedied to a certain extent, by using the cationic dyeing aid in surfactant form, but have such Leather has the disadvantage of a high water resistance.

The invention was therefore based on the object of the described To remedy deficiencies, i.e. to develop a process that allows anionic tanned or retanned leather with anionic dyes in deep shades and to dye with high rub fastness with good levelness.

The solution to this problem consists in the method according to the claims.

Chrome tanning has long played the leading role in the tannery. In more recent times, most of the chrome-tanned leather is made from fashionable and For quality reasons, anionically retanned, with the intensity of this retanning is constantly increasing. On the other hand, leather is dyed for reasons of authenticity practically only anionic dyes are considered. Due to the low bond between anionically charged leather surface and anionic dye result from Dyeing this anionically retanned chrome leather faces the same problems the achievable depth of color, as is the case with purely vegetable-tanned leather were known for a long time.

All egetabilic and most synthetic tannins are anionic.

With an anionically tanned or retanned leather is a leather meant that with vegetable or anionic synthetic tanning agents was tanned or retanned and more than 6%, based on the dry weight the skin, vegetable and / or anionic synthetic tanning agents.

Vegetable tanning agents are the oldest tanning agents of all and therefore do not really need a definition here. The most important ones are: Extracts from the bark 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). You are in the Ullmann, band 11, pages 585-595.

The anionic synthetic tanning agents consist essentially from the so-called syntans, i.e. condensates of phenolic and / or sulfonated ones Aromatics with formaldehyde, the sulfonation before or after the condensation can be carried out. They are described in Ullmann, Volume II, pages 595-600. The lignosulfonates described on page 777 are also included. They have in common that they have a more or less pronounced anionic character, which they tanned or retanned with it (if the amount of tanning agent used for retanning sufficient for this, i.e. more than about 6 percent by weight, based on the dry weight, convey leather.

The ammonium salts are practically all sufficiently water-soluble inorganic and organic ammonium salts into consideration, provided that their anion denotes Dyeing process does not interfere and is inert towards aldehydes. For example, it would be unsuitable Ammonium salts of oxidizing and reducing acids or of hydrocyanic acid. For economic reasons, ammonium salts are preferred, which are easily accessible inorganic acids, for example ammonium sulfate and ammonium chloride, as well as the lower carboxylic acids such as formic and acetic acid.

All sufficiently water-soluble mono- and dialdehydes can be used as aldehydes into consideration, for example formaldehyde, acetaldehyde, propionaldehyde and glyoxal. Is preferred because of its particularly pronounced effectiveness with regard to the deepening of color, glutaraldehyde.

Having sufficient water solubility is one for practical purposes for the purposes of the invention to understand sufficient solubility. Based on the folded weight the amount of ammonium sulfate used is 0.5 to 5, preferably 1.5 to 3 percent by weight, for other ammonium salts stoichiometrically corresponding amounts. Ammonium salt and Aldehydes are expediently used in an equivalent ratio of 1: 1 to 2: 1. Like example 4 shows, a deepening of the color is obtained even with smaller amounts of ammonium salt, however no optimal effects. Larger amounts of ammonium salt can be used without damage but the excess does not increase the effect.

The addition of ammonium salt and aldehyde can be mixed at the same time or preferably carried out separately, but you can also use the ammonium salt first and use the aldehyde later. The reverse order is also possible, but should the two components then be added at short intervals, so that not too large a proportion of the aldehyde before the addition of the ammonium salt is bound by the leather.

The treatment of the leather according to the invention before dyeing with ammonium salt and aldehyde occurs for about 10 to 120, preferably 20 to 50 minutes customary dyeing temperatures, ie 20 to 70, preferably 40 to 500C. The fleet length likewise corresponds to that which is customary in dyeing, i.e. 10 to 300, preferably 50 to 200%, based on the shaved weight. When using dry leather (crust leather) correspondingly longer liquor lengths are used.

The pH should be at the end of the treatment, i.e. before use of the dye, from 3 to 8, preferably from 4.5 to 6. At lower pH values If the reaction takes too long, if the time is higher it can decrease the quality of the Leather occur The pH drops during treatment, apparently because of ammonia consumed and the corresponding amount of acid is released. At the beginning of treatment the pH value can also be higher than 8 for a short time. It becomes useful by adding of weakly basic salts (buffer salts), e.g. sodium acetate, sodium formate, Sodium bicarbonate set. You can also adjust it with ammonia. In this In this case, the amount of ammonium salt can be reduced accordingly. In the extreme case of relatively ' The entire amount of ammonium salt can only be added to strongly acidic leather formed by ammonia in the solution.

The actual coloring can then be carried out in the same liquor The dye and optionally dyeing auxiliaries can be added but also dye in a separate liquor by customary methods in a drum or dyeing machine. The duration of the dyeing process can be about 15 minutes to 12 hours.

The percentages given in the examples relate to the shaved weight.

Example 1 Chrome-tanned cowhide of 1.7 mm fold thickness is like treated as follows: washing with 300% water at 500C for 10 minutes, draining the liquor Neutralize in 100% water at 500C + 1% sodium formate 30 minutes retanning: + 4% one Commercial tanning agent based on a phenol sulfonic acid / urea / formaldehyde condensation product 20 minutes + 6% mimosa extract 90 minutes, pH 3.8, drain the liquor, wash with 300 % Water, 500C 10 minutes drain the liquor Treatment according to the invention: 100% water, 500C + 0.8% sodium formate + 0.8% sodium bicarbonate simultaneously 20 minutes, pH 7.3 + 1% glutaraldehyde, dissolved in three times the amount of water + 2% ammonium formate undissolved pH 5.6 dyeing: + 1% of the brown dye C.I. No. 34 905 20% water 30 minutes + 4.5% of a commercially available leather oiling agent with a fat number of 80, dispersed in 20% water 45 minutes + 0.6% formic acid, diluted 10 times Amount of water for 20 minutes, pH 3.5. J The leather thus obtained is after does not matter when it dries and is colored much more intensely than a comparison sample which was dispensed with the treatment according to the invention. Even the handle of the invention treated leather is fuller and softer. Differentiate in the other properties the two leather samples are not recognizable.

Example 2 Leather, neutralization, retanning and washing as in Example 1.

Treatment according to the invention: 100% water, 500C + 1.5% ammonium chloride + 0.8% sodium formate + 0.4 fi sodium bicarbonate 10 minutes, pH 6.9 + 1.5% glutaraldehyde, dissolved in three times the amount of water, 40 minutes, pH 5.0.

Color as in example 1.

The result corresponds to that of example 1.

Example 3 Chrome-tanned calf leather with a fold thickness of 1.4 mm Washing: $ 300 water, 450C 10 minutes drain the liquor Retanning: 50% Water, 4OOC + 1% sodium formate + 2% of a commercially available neutral tanning agent based on naphthalenesulfonic acid / formaldehyde condensation products 30 minutes + 6% of a commercially available tanning agent based on phenol / phenol sulfonic acid / urea / formaldehyde condensation products 2 hours, pH 3.7, drain off the liquor, wash 300% water, 45 ° C. for 10 minutes, drain off the liquor Treatment according to the invention: 100% water, 60 ° C. + 1% sodium bicarbonate 20 minutes + 3% of a 30% aqueous formaldehyde solution + 3% ammonium sulfate, undissolved 20 minutes, pH 4.5 staining: + 1% of the red dye C.I. No. 15 620 20 minutes + 3.5% of a commercially available fatliquor with a fat number of 70 40 minutes + 0.5 % Formic acid 15 minutes pH 3.5.

The deepening of color compared to a comparison sample without the one according to the invention Treatment is clear, but not as severe as in Examples 1 and 2. The The handle is a little softer than that of the comparison sample.

Example ii Leather, neutralization, retanning and washing as in Example 1.

Treatment according to the invention: 100% water, 400C + 2 8 glutaraldehyde, dissolved in three times the amount of water + 1% 25% aqueous ammonia solution for 20 minutes, pH 4; 9.

Coloring and greasing as in Example 1.

The color deepening does not reach that of Examples 1 and 2, but is compared to a comparative sample without treatment according to the invention, it is clear. The handle is softer and fuller than that of the comparison sample.

When using twice the amount of ammonia, the color deepening is considerable stronger, the pH rises to 6.1. If 3% 25% aqueous ammonia solution is used a further increase in color intensification is achieved, the pH value rises to 7.7 and thus approaches a critical level, as can be seen from the slight solidification of the leather handle. shows. The grip can easily be avoided by instead of the 3% ammonia solution, its 2% is used together with 1% ammonium sulphate. /

Claims (2)

gatentansprche 1. Method for preparing anionically tanned or retanned leather for dyeing with anionic dyes in the aqueous phase, characterized in that the leather is treated with a) an ammonium salt before the dyeing process and b) treating an aldehyde or dialdehyde at pH 3 to 8. 2. The method according to claim 1, characterized in that as Aldehyde used glutaraldehyde.