EP1266070B1 - Mediator systems based on mixed metal complexes, used for reducing dyes - Google Patents

Abstract

Mediator systems obtainable by mixing one or more salts of a metal capable of forming a plurality of valence states with at least one amino-containing complexing agent (K1) and at least one hydroxyl-containing but amino-devoid complexing agent (K2) in an alkaline aqueous medium, wherefor the complexing agents may be present as salts and the molar ratio of K1 to metal ion is from 0.1:1 to 10:1 and the molar ratio of K2 to metal ion is from 0.1:1 to 5:1 are useful for dyeing cellulosic textile material.

Description

The present invention relates to mediator systems obtainable by mixing one or more salts of a metal which can form a plurality of valence states, with at least one amino group-containing complexing agent (K1) and at least one hydroxyl-containing, but not containing amino groups complexing agent (K2) in an alkaline aqueous medium Complexing agents may be present as salts and the molar ratio of K1 to metal ion is 0.1: 1 to 10: 1 and the molar ratio of K2 to metal ion is 0.1: 1 to 5: 1.

In addition, the invention relates to a process for the reduction of dyes and a process for dyeing cellulosic textile material using these Mediatorsysteme.

Vat dyes and sulfur dyes are important classes of textile dyes.

Vat dyes are of great importance for the dyeing of cellulose fibers, in particular because of the high fastnesses of the dyeings. When using these dyes, the insoluble oxidized dye must be converted to its alkali-soluble leuco form by a reduction step. This reduced form shows high affinity for the cellulose fiber, absorbs it and is converted to its insoluble form by an oxidation step on the fiber.

The class of sulfur dyes is of particular importance for the production of lower cost dyes with average fastness requirements. In the application of sulfur dyes, the implementation of a reduction and oxidation step is also required in order to fix the dye on the goods can.

The literature describes various reducing agents which are also used industrially, for example sodium dithionite, organic sulfinic acids, organic hydroxy compounds such as glucose or hydroxyacetone. For the reduction of sulfur dyes are in Some countries also used sulfides and polysulfides.

A common feature of these reducing agents is the lack of a suitable way to regenerate their reducing action, so that these chemicals are released into the wastewater after use with the dyebath. In addition to the costs of the fresh chemicals to be used also creates additional effort in the treatment of wastewater.

Other important disadvantages of these reducing agents are the very limited possibilities for influencing their reduction effect or their redox potential under conditions of use in the dyebath and the lack of simple control-technical possibilities for controlling the dyebath potential.

Another group of reducing agents was found with the class of iron (II) complexes. Iron (II) complexes with triethanolamine ( WO 90/15182 . WO 94/23114 ), with bicin (N, N-bis (2-hydroxyethyl) glycine) ( WO-A-95/07374 ), with triisopropanolamine ( WO-A-96/32445 ) and with aliphatic hydroxy compounds which may contain a plurality of hydroxyl groups and may additionally be functionalized by aldehyde, keto or carboxyl groups, such as di- and polyalcohols, di- and Polyhydroxyaldehyden, di- and polyhydroxyketones, di- and polysaccharides, di- and Polyhydroxymono and dicarboxylic acids and hydroxytricarboxylic acids, wherein the compounds derived from sugars, in particular the acids and their salts, for example gluconic and heptagluconic acid, and citric acid are emphasized as being preferred ( DE-A-42 06 929 . DE-A-43 20 866 . DE-A-43 20 867 not pre-published DE-A-199 19 746 such as WO-A-92/09740 ).

These iron (II) complexes have a reduction effect sufficient for dye reduction, which is described by the (negative) redox potential which can be measured at a specific molar ratio of iron (II): iron (III) in alkaline solution. Many of these iron (II) complexes, e.g. the complexes with triethanolamine, bicine, gluconic acid and heptagluconic acid, moreover, have the advantage of being capable of being electrochemically regenerated and thus of being used as mediators in the electrochemical reduction of dyes and in electrochemical dyeing processes.

Nevertheless, these iron complexes have specific weaknesses. Thus, the cathodic reduction when using Triethanolamin or bicine as a complexing agent as a diffusion-controlled electrode reaction with high cathodic current density perform, however, the corresponding iron complexes do not have sufficient stability in the weaker basic range at pH ≤ 11.5, which severely limits the applicability of these complexes as electrochemically regenerable reducing agents in Indigofärbebädern in denim production. Although iron complexes with gluconate or heptagluconate have very good complex stability in the pH range of 10 to 12, the cathodic current densities achievable with these complexes leave something to be desired, so that correspondingly larger electrolysis cells must be used and / or the concentration of iron complex is increased what is detrimental to the user in terms of energy requirements, chemical consumption, costs and wastewater pollution.

From textile practice international, 47, pages 44 - 49 (1992 ) and Journal of the Society of Dyers and Colourists, 113, pp. 135-144 (1997 ) it is also known to use mixtures of these iron complexes as reducing agents. Thus, in the former article, a mixture of iron (II) sulfate, triethanolamine and citric acid in a molar ratio of 1: 12.4 _: 0.02 described as a reducing agent for the analytical determination of indigo. In the latter article, a mixture of iron (III) sulfate, triethanolamine and sodium gluconate in the molar ratio 1 (based on iron): 6.3: 0.04 is proposed as a mediator for electrochemical dyeing with indigo.

But even with these mixtures, the disadvantages occurring in the individual complexes, in particular the lack of stability at lower pH values, can be observed.

The invention therefore an object of the invention to remedy the disadvantages mentioned and to enable the reduction of dyes in an advantageous, economical manner.

Accordingly, the mediator systems defined above were found.

In addition, a process for the electrochemical reduction of dyes in an alkaline aqueous medium and a process for dyeing cellulosic textile material with vat dyes or sulfur dyes under electrochemical dye reduction in the presence of metal complexes have been found as mediators, which are characterized in that the above-defined Mediator systems uses.

It is essential in the mediator systems according to the invention that a combination of the metal ion with the complexing agents K1 and K2 is present, in which the molar ratio K1 to metal ion is 0.1: 1 to 10: 1, preferably 0.5: 1 to 6: 1, and Molar ratio K2 to metal ion is 0.1: 1 to 5: 1, preferably 0.5: 1 to 3: 1.

The mediator systems according to the invention are obtainable by mixing the individual components, which can be used in the form of their water-soluble salts, in an alkaline aqueous medium. In this case, the metal ion is complexed, wherein, depending on the present pH, which is generally about 10 to 14, the most favorable complex preferably forms.

The metal ion M1 can be used in both lower and higher valued form. For example, iron (II) - and iron (III) salts can be used in the particularly preferred metal iron, which are first reduced electrochemically without problems to iron (II).

According to the invention, aliphatic amines having at least two coordinating groups which contain at least one hydroxyl group, are soluble in water or aqueous / organic media or can be mixed with water or the aqueous / organic media are suitable as complexing agents K1 containing amino groups.

The complexing agents K1 may additionally contain carboxyl groups. Preferred complexing agents K1 are e.g. Alcohol amines, in particular mono-, di- and Trialkohol- (especially alkanol) amines, such as triethanolamine and triisopropanolamine, and mono-, di- and Polyhydroxyaminocarbonsäuren such as N, N-bis (2-hydroxyethyl) glycine. Particularly preferred complexing agents K1 are triisopropanolamine and especially triethanolamine.

Of course, mixtures of complexing agents K1 can be used.

• Di- und Polyalkohole wie Ethylenglykol, Diethylenglykol, Pentaerythrit, 2,5-Dihydroxy-1,4-dioxan, vor allem Zuckeralkohole wie Glycerin, Tetrite wie Erythrit, Pentite wie Xylit und Arabit, Hexite wie Mannit, Dulcit, Sorbit und Galactid;
• Di- und Polyhydroxyaldehyde wie Glycerinaldehyd, Trioseredukton, vor allem Zucker (Aldosen) wie Mannose, Galactose und Glucose;
• Di- und Polyhydroxyketone wie vor allem Zucker (Ketosen) wie Fructose;
• Di- und Polysaccharide wie Saccharose, Maltose, Lactose, Cellubiose und Melasse;
• Di- und Polyhydroxymonocarbonsäuren wie Glycerinsäure, vor allem von Zuckern abgeleitete Säuren wie Gluconsäure, Heptagluconsäure, Galactonsäure und Ascorbinsäure;
• Di- und Polyhydroxydicarbonsäuren wie Äpfelsäure, vor allem Zuckersäuren wie Glucarsäuren, Mannarsäuren und Galactarsäure;
• Hydroxytricarbonsäuren wie Citronensäure.

As hydroxyl group-containing, but no amino groups containing complexing agent K2 according to the invention, in particular aliphatic hydroxy compounds having at least two coordinating groups suitable, which are also soluble in water or aqueous / organic media or miscible with water or the aqueous / organic media and which may contain a plurality of hydroxyl groups and / or aldehyde, keto and / or carboxyl groups. Specific examples of preferred complexing agents K2 are:

• Di- and polyalcohols such as ethylene glycol, diethylene glycol, pentaerythritol, 2,5-dihydroxy-1,4-dioxane, especially sugar alcohols such as glycerol, tetrites such as erythritol, pentitols such as xylitol and arabitol, hexitols such as mannitol, dulcitol, sorbitol and galactide;
• Di- and polyhydroxy aldehydes such as glyceraldehyde, triosereductone, especially sugars (aldoses) such as mannose, galactose and glucose;
• Di- and polyhydroxy ketones, especially sugars (ketoses) such as fructose;
• Di- and polysaccharides such as sucrose, maltose, lactose, celluloses and molasses;
• Di- and polyhydroxymonocarboxylic acids such as glyceric acid, especially acids derived from sugars such as gluconic acid, heptagluconic acid, galactonic acid and ascorbic acid;
• Di- and polyhydroxydicarboxylic acids such as malic acid, especially sugar acids such as glucaric acids, mannaric acids and galactaric acid;
• Hydroxytricarboxylic acids such as citric acid.

Particularly preferred complexing agents K2 are citric acid and especially the monocarboxylic acids derived from sugars, especially gluconic acid and heptagluconic acid, and their salts, esters and lactones.

Of course, mixtures of complexing agents K2 can be used. A particularly suitable example of this is a mixture of gluconic acid and heptagluconic acid, preferably in a molar ratio of 0.1: 1 to 10: 1, which gives particularly stable iron complexes even at relatively high temperatures.

Particularly preferred mediator systems according to the invention contain iron (II / III) ions as the metal ion, and triethanolamine as complexing agent K1 and as complexing agent K2 gluconic acid and / or heptagluconic acid.

The particular advantages of the mediator according to the invention are that an electrochemical dye reduction at low concentration of low-valent metal ion and thus low concentration of active complex can be carried out at high cathodic current density and at the same time there is a complex system, even at lower pH values, in the Rule ≤ 10, is stable. Unexpectedly, the achievable current densities and complex stabilities clearly exceed those expected for a mixture of the two individual systems (metal ion / K1 and metal ion / K2).

For comparison, the cyclic voltammetry using a hanging mercury drop electrode at a voltage feed rate of 200 mV / s for a Mediatorsystem of iron ions, gluconate ions and triethanolamine at a NaOH concentration of 0.175 mol / l determined cathodic peak currents are shown. Measurement iron gluconate triethanolamine pH peak potential Kath. peak power No. minor minor minor mV mA 1 0,010 0,020 0,060 12.9 -1010 43.0 2 0,010 0,020 0,030 13.1 -1005 43.0 3 0,010 0,020 0,010 12.9 -1000 38.6 4 0,010 0,020 0,002 12.9 -1000 22.4 V1 0,010 - 0,060 12.9 -1010 42.8 V2 0,010 0,020 - 12.9 -1000 5.5

The mediator systems according to the invention are outstandingly suitable for the electrochemical reduction of dyes.

Particular importance of the process of the invention for the reduction of vat dyes and sulfur dyes, the classes of indigoid dyes, anthrachinoid dyes and dyes based on highly condensed, aromatic ring systems and the sulfur-cooking and sulfur baking dyes should be mentioned. Examples of vat dyes include indigo and its bromo derivatives, 5,5'-dibromoindigo and 5,5 ', 7,7'-tetrabromoindigo, and thioindigo, acylaminoanthraquinones, anthraquinonazoles, anthrimides, anthrimidecarbazoles, phthaloylacridones, benzanthrones and indanthrones, and pyrenchinones, anthanthrones, Pyranthrones, Acedianthrone and perylene derivatives. Examples of particularly important sulfur dyes are CI Sulfur Black 1 and CI Leuco Sulfur Black 1 and sulfur vat dyes such as CI Vat Blue 43.

In the process according to the invention for the reduction of the dye, the maximum amount used is usually approximately the amount of mediator required stoichiometrically for the dye reduction. Thus, per mol of an oxidized dye which absorbs two electrons per molecule in order to convert into the leuco form, 2 mol of a mediator system according to the invention are generally calculated, based on the redox-active, an electron-supplying metal ion. Of course, this mediator amount can be lowered by the electrochemical regeneration of the mediator (when dyeing with vat dyes, based on a liter of dyebath, usually up to about 0.1 to 1 mol reduced mediator per mole of dye). The greater the deficit in the mediator system, the higher the demands on the electrolysis cell.

The reduction process according to the invention can advantageously be part of the likewise inventive process for dyeing cellulose-containing textile material with vat and sulfur dyes. Preferably, the dye is added to the dyebath in prereduced form, e.g. an alkaline solution catalytically reduced indigo, and reduces the reoxidized during dyeing by air contact portion of the dye electrochemically using the mediator according to the invention.

The dyeing itself can be carried out as described in the literature mentioned above. In this case, by all known continuous and discontinuous dyeing methods, e.g. after the exhaust process and the padder process.

Depending on the particular dyeing process and the dyeing apparatus used, the access of air varies in size, and in some cases considerable amounts of mediator system are required to trap the atmospheric oxygen. Thus, e.g. in exhaust dyeing with vat dyes at medium color depths, an additional requirement of about 1 to 10 moles of reduced mediator per mole of dye and in continuous dyeing with indigo of about 2 to 10 moles of reduced mediator per mole of indigo.

The further process conditions, such as type of textile auxiliaries, amounts used, dyeing conditions, type of electrolysis cell, completion of the dyeings, can be selected as usual and described in the literature mentioned above.

According to the dyeing process according to the invention, all cellulose-containing textile materials can be dyed advantageously. Examples include: fibers of cotton, regenerated cellulose such as viscose and modal, and bast fibers such as flax, hemp and jute. Forms of presentation include eg flake, ribbon, yarn, twine, woven, knitted, knitted and made-up pieces. Mechanical forms can be packing systems, yarn skein, spool, warp beam and cloth beam as well as piece goods in strand and wide.

Examples yarn dyeing example 1

1.8 kg dye pretreated yarn of cellulose fibers (average fineness) were stained for two cross-wound bobbins in an input coupled to an electrolytic cell yarn dyeing apparatus with 18.2 g Indanthren Brilliant ^® Violet 3B (CI Vat Violet 9).

The electrolysis cell was a multi-cathode cell (10 electrodes, 0.18 m ² viewing area, total area 4.3 m ² ). The anolyte used was 2% strength by weight sodium hydroxide solution (corresponding to the amount of charge flowed, 50% strength by weight sodium hydroxide solution was added in order to keep the cell voltage constant). The separation of catholyte (dyebath) and anolyte was carried out by a cation exchange membrane. The cathode used was a stainless steel mesh and the anode used was a platinum mixed oxide coated titanium electrode.

Dyeing was done as follows: 180 l of a dyebath of the composition 0.015 mol / l Iron (III) chloride (40% strength by weight aqueous solution, 4.3 ml / l) 0.068 mol / l Triethanolamine (85% strength by weight aqueous solution, 12 g / l) 0.005 mol / l Sodium gluconate (99%, 1 g / l) 0.37 mol / l Sodium hydroxide solution (50% strength by weight aqueous solution, 14.8 g / l) 1 g / l a commercial wetting agent 1.2 g / l a commercial dispersant 0.7 g / l a commercial water correction agent circulated through the yarn packages (30 l / kg min) and the electrolysis cell (100 l / min) and were reduced prior to dyeing.

By cathodic reduction with a current of 45 A, the oxygen was first removed from the dyebath. After reaching a potential of -650 mV, the cell current was lowered to about 2 A in order to keep the dyebath potential below the leuco potential of the dye.

After reaching a dyeing bath temperature of 80 ° C, the dye was added. After a pigmentation time of 10 minutes at a redox potential of about -700 to -750 mV, the cell current was increased to 9 A in order to uniformly convert the dye into its reduced form by indirect electrolysis. The redox potential rose within 30 min to -920 mV and was then stabilized by regulating the cell current to a value between -930 and -940 mV. Under these conditions an additional 30 min was dyed. Meanwhile, the iron (II) was complex continuously regenerated electrochemically.

The completion of the dyeing was done in the usual way by oxidation, rinsing, soaps and neutralizing.

The dyeing result corresponded in color, color depth and levelness to the result obtained under the same conditions with a conventional reducing agent.

Example 2

3.6 kg of pretreated cellulose fiber (average fineness) yarn were dyed onto four cheeses in the yarn dyeing apparatus of Example 1 with 18.2 g Indanthren Brilliant Violet 3B (C.I. Vat Violet 9).

Dyeing was done as follows: 180 l of a dyebath of the composition 0.040 mol / l Iron (III) chloride (40% strength by weight aqueous solution, 11.5 ml / l) 0.068 mol / l Triethanolamine (85% strength by weight aqueous solution, 12 g / l) 0.031 mol / l Sodium gluconate (99%, 6.8 g / l) 0.5 mol / l Sodium hydroxide solution (50% strength by weight aqueous solution, 20 g / l) 1 g / l a commercial Egalisierhilfsmittels 1 g / l a commercial wetting agent 1 g / l a commercial dispersant 0.5 g / l a commercial water correction agent circulated through the yarn packages (30 l / kg min) and the electrolysis cell (100 l / min) and were reduced prior to dyeing.

By cathodic reduction with a current of 45 A, the oxygen was first removed from the dyebath. After reaching At a potential of -700 mV, the cell current was lowered to about 1 A to keep the dyeing bath potential below the leuco potential of the dye.

After reaching a dyeing bath temperature of 80 ° C, the dye was added. After a pigmentation time of 30 minutes at a redox potential of about -765 to -780 mV, the cell current was increased to 30 A in order to uniformly convert the dye into its reduced form by indirect electrolysis. The redox potential rose within 20 min to -920 mV and was then stabilized by controlling the cell current to a value between - 930 and -940 mV. Under these conditions an additional 40 minutes was dyed. Meanwhile, the iron (II) was complex continuously regenerated electrochemically.

The completion of the dyeing was done in the usual way by oxidation, rinsing, soaps and neutralizing.

The dyeing result corresponded in color, color depth and levelness to the result obtained under the same conditions with a conventional reducing agent.

Example 3

3.6 kg of pretreated yarn of cellulose fibers (average fineness) were applied to four cheeses in the yarn dyeing apparatus of Example 1 with a dye mixture of 247.1 g Indanthren direct black 5589, 85.3 g Indanthren Marine Blue G (CI Vat Blue 16), 64 , 9 g Indanthren Orange RRTS (CI Vat Orange 2) and 17.2 g Indanthren Olive Green B (CI Vat Green 3) stained.

Dyeing was done as follows: 180 l of a dyebath of the composition 0.024 mol / l Iron (III) chloride (40% strength by weight aqueous solution, 6.8 ml / l) 0.051 mol / l Triethanolamine (85% strength by weight aqueous solution, 9 g / l) 0.017 mol / l Sodium gluconate (99%, 3.7 g / l) 0.34 mol / l Sodium hydroxide solution (50% strength by weight aqueous solution, 13.7 g / l) 1 g / l a commercial Egalisierhilfsmittels 1 g / l a commercial wetting agent 1 g / l a commercial dispersant 0.5 g / l a commercial water correction agent circulated through the bobbins (30 l / kg min) and the electrolysis cell (100 l / min) and were reduced before dyeing.

By cathodic reduction with a current of 40 A, the oxygen was first removed from the dyebath. After reaching a potential of -670 mV, the cell current was lowered to about 1 A in order to keep the dyebath potential below the leuco potential of the dyes.

After reaching a dyeing bath temperature of 80 ° C, the dye mixture was added. After a pigmentation time of 30 min at a redox potential of about -765 to -780 mV, the cell current was increased to 40 A in order to uniformly convert the dye into its reduced form by indirect electrolysis. The redox potential rose within 60 min to -920 mV and was increased while keeping the cell current within 40 min to -950. Meanwhile, the iron (II) was complex continuously regenerated electrochemically.

The completion of the dyeing was done in the usual way by oxidation, rinsing, soaps and neutralizing.

The dyeing result corresponded in color, color depth and levelness to the result obtained under the same conditions with a conventional reducing agent.

Example 4

1.8 kg of pretreated yarn of cellulose fibers (average fineness) were dyed on two cheeses in the yarn dyeing apparatus of Example 1 with 49.7 g of Indanthrene Blue BC (C.I. Vat Blue 6).

Dyeing was done as follows: 180 l of a dyebath of the composition 0.010 mol / l Iron (III) chloride (40% strength by weight aqueous solution, 2.8 ml / l) 0.068 mol / l Triethanolamine (85% strength by weight aqueous solution, 12 g / l) 0.005 mol / l Sodium gluconate (99%, 1 g / l) 0.37 mol / l Sodium hydroxide solution (50% strength by weight aqueous solution, 14.8 g / l) 0.25 g / l a commercial dispersant circulated through the bobbins (30 l / kg min) and the electrolysis cell (100 l / min) and were reduced before dyeing.

By cathodic reduction with a current of 30 A, the oxygen was first removed from the dyebath. After reaching a dyeing bath temperature of 60 ° C and a potential of -910 mV, the dye was added within 10 min. The redox potential was kept between -910 and -920 mV. After complete dye addition, the redox potential was stabilized by controlling the cell current between -920 and -940 mV. Under these conditions an additional 35 minutes was stained. Meanwhile, the iron (II) was complex continuously regenerated electrochemically.

The completion of the dyeing was done in the usual way by oxidation, rinsing, soaps and neutralizing.

The dyeing result corresponded in color, color depth and levelness to the result obtained under the same conditions with a conventional reducing agent.

Claims (11)

1. Mediator systems obtainable by mixing one or more salts of a metal capable of forming a plurality of valence states with at least one amino-containing complexing agent (K1) and at least one hydroxyl-containing but amino-devoid complexing agent (K2) in an alkaline aqueous medium, wherefor the complexing agents may be present as salts and the molar ratio of K1 to metal ion is from 0.1 : 1 to 10 : 1 and the molar ratio of K2 to metal ion is from 0.1 : 1 to 5 : 1.
2. Mediator systems according to claim 1, containing iron(II) ions and/or iron(III) ions as the metal ion.
3. Mediator systems according to claim 1 or 2, wherein said complexing agent K1 is an aliphatic amino compound containing at least two coordination-capable groups containing at least one hydroxyl group.
4. Mediator systems according to any of claims 1 to 3, wherein said complexing agent K1 is an alcoholamine.
5. Mediator systems according to any of claims 1 to 4, wherein said complexing agent K2 is an aliphatic hydroxy compound containing at least two coordination-capable groups which may contain a plurality of hydroxyl groups and/or aldehyde, keto and/or carboxyl groups.
6. Mediator systems according to any of claims 1 to 5, wherein said complexing agent K2 is a hydroxyl-containing aliphatic carboxylic acid.
7. Mediator systems according to any of claims 1 to 6, wherein the metal ions are iron (II/III) ions, said complexing agent K1 is triethanolamine and said complexing agent K2 is gluconic acid and/or heptagluconic acid.
8. Process for electrochemical reduction of dyes in an alkaline aqueous medium using metal complexes as mediators, characterized in that it comprises using a mediator system according to any of claims 1 to 7.
9. Process according to claim 8 characterized in that it is used for reducing vat dyes and sulfur dyes.
10. Process for dyeing cellulosic textile material with vat dyes or sulfur dyes by electrochemical dye reduction in the presence of metal complexes as mediators, characterized in that it comprises using a mediator system according to any of claims 1 to 7.
11. Process according to claim 10, characterized in that the dye is added to the dyebath in prereduced form and the dye fraction reoxidized during dyeing by air contact is electrochemically reduced by means of the mediator system.