EP0024014B1 - Method of retanning mineral tanned leather with aromatic sulfonic acids - Google Patents

Description

worin

• R für die Reste
  
• R₁ für Wasserstoff oder Methyl,
• X für Wasserstoff, ein Alkali-, insbesondere Natrium- oder Kalium-lon, oder für ein Ammonium-lon und
• n für 1-4 stehen, und worin
• S0₃X an Phenyl gebunden ist.

The invention relates to a process for retanning mineral leather, in particular tanned with chrome tanning agents, using sulfonic acids and their salts of the general formula

wherein

• R for the leftovers
  
• R _{1 represents} hydrogen or methyl,
• X for hydrogen, an alkali ion, in particular sodium or potassium ion, or for an ammonium ion and
• n stands for 1-4, and where
• S0 ₃ X is bound to phenyl.

The isomeric mono- and disulfonic acids of diphenyl, terphenyl, diphenyl ether and ditolyl ether and their alkali and ammonium salts are preferably used.

The use of sulfonic acids of other non-crosslinked aromatic hydrocarbons in various leather manufacturing processes, for example naphthalene and toluene as an aid for the decalcification of pelt material (GB-A 8096) or in the form of their chromium III salts for tanning (DE-C 627 110 and 643088) is already known. The alkali metal salts of the mono- and disulfonic acids of benzene and naphthalene have also already been proposed for the preservation and improvement of the storage stability of mineral-soft, undyed leather in a moist or dry state (DE-C 578 785). Furthermore, the use of aromatic sulfonic acids as non-swelling acids to acidify the skin material prior to tanning is state of the art (see Ullmanns Enzyklopadie der Technische Chemie, 4th edition, volume 16, page 120).

Formaldehyde condensation products of β-naphthalenesulfonic acid (DE-C 290 965), diphenyl and ditolyl ether sulfonic acids (US-A 2315951) and terphenylsulfonic acids (US) are, for example, common as retanning agents and as auxiliaries for leveling chemical and / or physical irregularities in the leather surface -A 3906037) and their ammonium or alkali salts. So-called exchange tanning agents, which are predominantly present as phenol-containing formaldehyde condensation products of aromatic sulfonic acids or their salts, are common practice as retanning and / or leveling agents for chrome leather (GB-A 1 291 784 and DT-A 611 671).

The disadvantage of these higher molecular weight anionic retanning and leveling agents is that, in interaction with anionic dyes, they preferentially attach to the leather surface and block binding possibilities for anionic dyes here. This inevitably leads to the dyes predominantly setting deeper in the leather.

In this way, very uniform surface colorations are obtained, but in comparison to the dyeing without anionic leveling agents, they are highly lightened. The range of dyes is only partially used for surface coloring. If a high level of coloration is required, losses in color strength caused by the use of anionic retanning agents and leveling agents have to be accepted.

There are gradual differences in the lightening effect on dyeings between the different types of tanning agents and leveling agents, which may depend, among other things, on the ratio of leveling agents or retanning agents to dye and dye-specific, but they consistently cause high color loss on leather, that can reach 50-80% compared to leathers that are dyed under comparable conditions but without retanning or leveling agent treatment.

If the leather surface is reloaded cationically by means of cationic auxiliaries or mineral tanning agents to produce deep dyeings on heavily retanned leathers, similarity deficiencies often arise as are observed in the dyeing of the pure leather not treated with anionic tanning agents, retanning agents or leveling aids .

It has surprisingly been found that the sulfonic acids or their salts of the formula (I), which have not been condensed to form larger molecules with formaldehyde like anionic synthetic tanning agents and leveling agents, are particularly suitable as retanning agents. They offer the advantage that the leather retanned with it or the leather treated before or during dyeing results in deep and brilliant surface dyeings with anionic dyes, with evenness of levelness. The color depth results similar to pure chrome leather that has not been treated with retanning agents and / or leveling agents.

Suitable retanning agents of the formula (I), which allow a deep and brilliant coloration of the leather with optimal use of the dye, are preferably partially or completely with sodium hydroxide or - because of their better solubility - preferably mixtures of terphenyl-mono- and - neutralized with ammonia disulfonic acids. They can e.g. produce; by allowing 2 moles of sulfuric acid monohydrate to act for 2 hours at 145-150 ° C. for 2 hours for sulfonation in accordance with US Pat Final pH neutralized and converted into powder by spray drying.

The technical isomer mixtures of terphenyl, which are inevitably obtained as by-products in the diphenyl synthesis from benzene, are suitable and particularly economical as the starting product for the production of such terphenylsulfonic acid mixtures.

The sulfonic acids and their salts of the formal (I) are optimally effective for levelness, brilliance and depth of the coloring of the leather if they are obtained before or during the coloring with anionic dyes in amounts of 2-10%, preferably 3-6% ( can act on the so-called fold weight of the leather) on the leather and pull it up. They are particularly good at leveling the color and compensating for the different dyeability of damaged and undamaged areas within individual skins or skins if they are applied to the leather before the dye is added and the dye can then be evenly applied to the leveled leather.

• 40-80 Gewichtsteilen eines 33 % basischen Chromsulfat,
• 40-20 Gewichtsteilen des Natriumsalzes eines Terphenyl-mono- und -disulfonsäure-Gemisches aus einem technischen Terphenyl-Isomerengemisch
• 20-0 Gewichtsteile Natriumsulfit.

The compounds of formula (I) can also be used in combination with other tanning agents and auxiliaries on leather. For example, they can be combined with chrome tanning agents, which in practice are often used together with synthetic tanning agents for retanning to increase the fullness and shape the leather character. Expediently, additions of base agents and / or neutralizing agents, such as sodium sulfite, soda or alkali or alkaline earth metal salts of organic carboxylic acids such as formic acid, acetic acid or technical dicarboxylic acid mixtures, are also added to the combination to the chromium tannin portion. If, for example, improvement in leather fullness and softness and at the same time good dyeability is required, the following combination has proven itself

• 40-80 parts by weight of a 33% basic chromium sulfate,
• 40-20 parts by weight of the sodium salt of a terphenyl mono- and disulfonic acid mixture from a technical terphenyl isomer mixture
• 20-0 parts by weight of sodium sulfite.

• 70-40 Gewichtsteilen Natriumsalze eines technischen Dicarbonsäuregemisches, wie es bei der Adipinsäure-Herstellung zwangsweise als Nebenprodukt anfällt.
• 30-60 Gewichtsteile Natrium- und/oder Ammoniumsalze von Mono- und Disulfonsäure-Gemischen eines technischen Terphenyl-Isomerengemisches.

Mixtures of sodium or ammonium salts of the described aromatic sulfonic acids according to formula I, preferably the mono- and disulfonic acids of a terphenyl isomer mixture from diphenyl synthesis with alkali or alkaline earth metal salts with mono- or polybasic salts, have also proven to be particularly suitable for simultaneous neutralization and leveling retanning organic acid, for example

• 70-40 parts by weight of sodium salts of a technical dicarboxylic acid mixture, as is necessarily obtained as a by-product in the production of adipic acid.
• 30-60 parts by weight of sodium and / or ammonium salts of mono- and disulfonic acid mixtures of a technical terphenyl isomer mixture.

In the following examples, the percentages relate to the fold weight of the chrome leather, unless stated otherwise.

example 1

Chromium leather made from cowhide or calfskin, which is manufactured in the usual manner, folded to 1.6-1.8 mm and neutralized to pH 3.8-4.2, is 40 in a rotating tanning drum with 6% of an acid number (mg KOH / g) 40 adjusted mixture of terphenyl mono- and di-sulfonic acid ammonium salts, which is formed when 2.4 mol of sulfuric acid monohydrate is allowed to act on a technical terphenyl isomer mixture from the diphenyl synthesis at 150 ° C. in the course of 3 hours and then after cooling and diluting to acid number 40 neutralized with ammonia and spray dried.

After this pretreatment of the leather, dyeing is carried out in the usual manner with 1% of the copper complex of a monoazo dye from DE-PS 670 935, Example 1.

Following the dyeing, greasing is carried out in the dye bath in a customary manner and then treated with 1.5% formic acid in order to achieve the best possible absorption of the dye and the greasing.

After drying and tensioning the leather, the result is a full, soft leather with exceptionally bllanter and deep surface coloring.

In terms of color depth, this leather corresponds to leather dyed with the same amount of dye without pretreatment, but this results in significantly lower levelness.

A chrome leather, which was treated under the same conditions with the Na salt of the terphenylsulfonic acid-formaldehyde condensate, which was prepared according to US Pat. No. 3,906,037, Example 3, instead of the terphenylsulfonic acid salts, has a strongly lightened, pale coloration.

Example 2

In normal operation, 1.6-1.8 mm thick and pH 3.6-3.8 neutralized chrome cowhides are treated with 4% of a diphenyl ether disulfonic acid sodium salt for 10 minutes to initiate retanning in a 100% warm liquor. To prepare the sodium diphenyl ether disulfonate, 2.4 mol of sulfuric acid monohydrate per 1 mol of diphenyl ether at 120 ° C. are expediently allowed to act for 2 hours with vigorous stirring, the mixture is cooled, diluted, neutralized with sodium hydroxide solution and converted into powder form by spray drying.

After the treatment mentioned above, intensive retanning follows in the same bath, each with 2% of a phenolic tanning agent, a resin tanning agent based on dicyandiamide and a vegetable tanning agent, preferably Mimosa extract. After 45 minutes the tannins are completely absorbed and the liquor can be drained. Then, as usual, dyeing is continued in a fresh liquor with 2% of the anionic metal complex dye Acid Brown 85 (C.I. 34 900). Greasing and further completion are also customary in the company. The finished leather results in full brilliant and equally level coloring in the cattle box character.

Improvements in the dyeability, particularly the depth of color, the brilliance and the levelness, are particularly evident when a comparative experiment is carried out in which the condensation product obtained from diphenyl ether sulfonic acid and formaldehyde obtained according to US Pat. No. 2,315,951, Example 1, is used instead of the diphenyl ether sulfonic acid sodium salt.

Example 3

To produce nubuck leather, chrome leather, which is folded and neutralized to pH 6.0 (cut color with bromotymol blue yellow to yellow-green), is first washed with 300% water at 40 ° C in a customary manner. After draining the wash liquor, pre-greased for 15 minutes with 2.5% of a sulfite-based leather greasing agent based on trans in 100% of a liquor at 40 ° C. and then treated in the same liquor for 10 minutes with 1% of an ammonia solution containing 2.5% by weight of NH ₃ contains. Then 2.5% of the anionic metal complex dye Acid Brown 85 (CI 34 900) together with 2% of the potassium salt of o-terphenyl-4,4 ', 4 "-trisulfonic acid and 2% of a sweetened chestnut extract are added and 90 minutes simultaneously After this treatment, 100% water at 70 ° C. is added and the mixture is left to act for 10 minutes before being acidified in the same liquor with 1.5% of a formic acid solution (up to pH 3.8) for 40 minutes 8.5% by weight of pure formic acid after draining the liquor, in a new bath in 100% liquor at 55 ° C. with another 1.5% of the same dye as in the pretreatment and then with a fat mixture based on wool fat and chloroparaffin sulfonate Finally, after-treatment is carried out with 2.5% sweetened chestnut wood extract and acidified again with 0.5% of a formic acid solution which contains 8.5% by weight of pure formic acid, with a final pH of 3.8 Leather b rinsed as usual and stored on trestle overnight. After wilting, vacuum drying for 1/2 minute at 80 ° C and 50% counter pressure, hanging drying, conditioning, tunnels and another vacuum drying for 1/2 minute at 80-90 ° C. After that, with a residual moisture content of 18-20%, the grain side is sanded in 3-4 passages with 220-230 sandpaper, depending on the texture of the grain.

This way of working results in full and soft nubuck leather, which is characterized by high brilliance and levelness of coloration and very fine, even sanding.

o-Terphenyl-4,4 ', 4 "-trisulfonic acid is prepared by reacting 230 g each of o-terphenyl (approx. 95%) with 1,500 g of sulfuric acid monohydrate at 110 ° C. for 90 minutes and adding potassium chloride to it Potassium salt transferred (see Journal of Organic Chemistry 14, 163 (1949)).

Claims (4)

1. Process for re-tanning mineral-tanned leathers, characterised in that sulphonic acids, and salts thereof, of the general formula

wherein

R represents the radical

R₁ represents hydrogen or methyl,

X represents hydrogen, an alkali metal ion, in particular a sodium or potassium ion, or an ammonium ion and

n represents a number from 1-4, and wherein

S0₃X is bonded to phenyl, are used as the re-tanning agents.

2. Process according to Claim 1, characterised in that salts of mono- and di-sulphonic acid mixtures of diphenyl, terphenyl, diphenyl ether or ditolyl ether which have been completely or partly neutralised with alkali or ammonia are used as the re-tanning agents.

3. Process according to Claim 2, characterised in that mono- and di-sulphonic acid mixtures of the isomers of terphenyl which have been completely or partly neutralised with alkali or ammonia are used as the re-tanning agents.

4. Process according to Claim 3, characterised in that sulphonic acid mixtures of technical grade isomer mixtures of terphenyl, from the synthesis of diphenyl, which have been completely or partly neutralised with alkali or ammonia and are obtained by the action of 2-2,5 mols of sulphuric acid monohydrate on 1 mol of terphenyl at 110-180 °C, preferably 140-175 °C, over a period of, in particular, 3 hours, are used as the re-tanning agents.