EP1266069A1

EP1266069A1 - Mediator systems based on mixed metal complexes, used for reducing dyes

Info

Publication number: EP1266069A1
Application number: EP01909807A
Authority: EP
Inventors: Thomas Bechtold; Eduard Burtscher; Norbert Grund; Wolfgang Schrott; Peter Maier; Georg Schnitzer; Franz SÜTSCH
Original assignee: Dystar Textilfarben GmbH and Co Deutschland KG
Current assignee: Dystar Textilfarben GmbH and Co Deutschland KG
Priority date: 2000-03-02
Filing date: 2001-03-01
Publication date: 2002-12-18
Anticipated expiration: 2021-03-01
Also published as: US20030088926A1; MXPA02008540A; HK1053156A1; HK1053156B; KR100683309B1; DE50115088D1; US6790241B2; ATE441756T1; ES2330505T3; JP2003525362A; DE10010060A1; CN1406300A; CN1296553C; BR0108852A; EP1266069B1; KR20020087064A; WO2001064999A1; PT1266069E

Abstract

Mediator systems obtainable by mixing a salt of an electrochemically active complexing metal (M1) capable of forming a plurality of valence states with a hydroxyl-containing complexing agent, which may likewise be present as salt, and with a salt of an electrochemically inactive complexing metal (M2) in an alkaline aqueous medium, wherefor the molar ratio of metal ion M2 to metal ion M1 is from 0.8:1 to 2:1 are useful for reducing dyes and dyeing cellulosic textile material.

Description

Mediator systems based on mixed metal complexes for the reduction of dyes

description

The present invention relates to mediator systems obtainable by mixing a salt of an electrochemically active, complex-forming metal (Ml), which can form several valence levels, with a hydroxyl-containing complexing agent, which can also be in the form of a salt, and a salt of an electrochemically inactive, likewise complex-forming metal ( M2) m alkaline aqueous

Medium, the molar ratio of metal ion M2 to metal ion Ml is 0.8: 1 to 2: 1.

In addition, the invention relates to a process for reducing dyes and a process for dyeing textile material containing cellulose using these mediator systems, and textile materials containing cellulose dyed by these processes.

Vat and sulfur dyes are important classes of textile dyes.

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

The class of sulfur dyes is of particular importance for the production of inexpensive dyeings with average fastness requirements. When using the sulfur dyes, a reduction and oxidation step is also necessary in order to be able to fix the dye on the goods.

A wide variety of reducing agents are described in the literature which are also used industrially, for example sodium dithionite, organic sulfonic acids, organic hydroxy compounds such as glucose or hydroxyacetone. In some countries, sulfides and polysulfides are also used to reduce sulfur dyes. A common feature of these reducing agents is the lack of a suitable way to regenerate their reducing effect, so that these chemicals are released after use with the dye bath ms waste water. In addition to the costs for the freshly used chemicals, there is also additional effort involved in treating the waste water

Other important disadvantages of these reducing agents are the very limited options for influencing their reducing effect or their redox potential

Conditions of use in the color bath and the lack of simple control options for regulating the color bath potential

Another group of reducing agents was found with the class of iron (II) complexes. Known s nd iron (II) complexes with tr ethanolamm (WO-A-90/15182, WO-A-94/23114), with Bicm (N, N-Bιs (2-hydroxyethyl) glycm) (WO-A-95 / 07374), with Trnsopropanolamm (WO-A-96/32445) as well as with aliphatic Hydroxyverbmdungen, which can contain several hydroxyl groups and additionally by aldehyde,

Keto or carboxyl groups can be functionalized, such as di- and polyalcohols, di- and polyhydroxyaldehydes, di- and polyhydroxyketones, di- and polysaccharides, di- and polyhydroxymono- and -dicarboxylic acids as well as hydroxytπcarboxylic acids, whereby the compounds derived from sugars, especially the acids and their salts, e.g. Gluconic and heptagluconic acid, and citric acid are emphasized as preferred (DE-A-42 06 929, DE-A-43 20 866, DE-A-43 20 867, the unpublished DE-A-199 19 746 and WO-A -92/09740).

These iron (II) complexes have a reducing action sufficient for dye reduction, which is described by the (negative) redox potential which can be measured at a certain molar ratio of iron (III): iron (III) in alkaline solution. Numerous of these iron (II) complexes, e.g. the complexes with triethanolamm, bicm, gluconic acid and heptagluconic acid also have the advantage that they can be regenerated electrochemically and thus can be used as mediators in the electrochemical reduction of dyes and in electrochemical color processes.

It is also known to use mixtures of these iron complexes as reducing agents. So m textil praxis international, 47, pages 44 - 49 (1992) and Journal of the Society of Dyers and Colouπsts, 113, pages 135 - 144 (1997) are mixtures of Iron salts, triethanolamine and citric acid or gluconic acid are described. In the last-mentioned article, mixtures of iron salts, calcium salts and gluconic acid and / or heptagluconic acid are also used as mediators, in which the molar ratio of calcium to iron is from 0.5 to 0.75.

However, the known mediator systems have certain weaknesses. The iron complexes based on triethanolamine or bicin show a sufficient negative redox potential for dye reduction, but are not sufficiently stable in the weakly basic range at pH <11.5, which severely limits their electrochemical regenerability in indigo dye baths when producing denim. The mediator systems based on gluconate or heptagluconate have very good complex stability in the pH range from 10 - 12, but in the known systems a relatively high proportion of iron (II) must be complex in order to achieve a redox potential of <-700 mV ( Ag / AgCl, 3 m KC1 reference electrode), as it is e.g. is required to maintain the required bath stability when dyeing with indigo. However, the required high proportion of iron (II) complex is particularly disadvantageous when dyeing with indigo in the denim production, since the textile material is dyed in layers by multiple dips in the dyebath and subsequent air oxidation of the dye, so that the mediator contained in the dyebath is complete with each air passage is oxidized and only has to be reduced again for the next dyeing step, which results in high power consumption, which in turn requires high mediator concentrations or correspondingly large electrolysis cells to compensate.

The object of the invention was therefore to remedy the disadvantages mentioned and to enable the reduction of dyes in an advantageous, economical manner. In particular, stable mediator systems with good reducing power should be provided.

Accordingly, the mediator systems defined at the outset were found.

In addition, a process for the electrochemical reduction of dyes in an alkaline aqueous medium and a process for dyeing cellulose-containing textile material with vat dyes or sulfur dyes with electrochemical dye reduction in the presence of metal complexes as mediators were found, which are characterized in that the initially defined Uses mediator systems.

Last but not least, cellulose-containing textile materials were found, which were dyed using this method.

It is essential in the mediator systems according to the invention that there is a combination of the electrochemically active metal ion Ml with an electrochemically inactive metal ion M2, which is also capable of com formation, and a complexing agent which contains hydroxyl groups but does not contain any amino groups and which has the molar ratio of metal ion Ml to metal ion M2 0. 8: 1 to 2: 1, preferably 0.9: 1 to 1.1: 1 and particularly preferably about 1: 1.

The mediator systems according to the invention can be obtained by mixing the individual components, which can be used in the form of their water-soluble salts, in an alkaline aqueous medium which generally has a pH of about 10 to 14. The metal ions M1 and M2 are at least partially complexed, an approximately aquimolar complex preferably being formed.

The amount of complexing agent is not critical and is only of minor importance given a predetermined ratio of reduced to oxidized form of the metal ion Ml. Usually at least as much complexing agent is used as would be theoretically required for complete complexation of Ml, that is at least 0.5 mol, preferably 1 mol, per mol of Ml. There is in principle no upper limit for this molar ratio, but for reasons of cost one will generally not use more than 5 mol, in particular 3 mol, especially 1.5 mol, of complexing agents per mol of ml.

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

Aliphatic hydroxy compounds with at least two groups capable of coordination, which are likewise soluble in water or aqueous / organic media or are miscible with water or the aqueous / organic media and which have several hydroxyl groups and / or aldehyde, keto and / or may contain carboxyl groups. Examples are preferred complexing agents in detail:

Di- and polyalcohols such as ethylene glycol, diethylene glycol, pentaerythritol, 2, 5-dihydroxy-l, 4-dioxane, especially sugar alcohols such as glycerol, tetrites such as erythπt, pentites such as xylitol and arabitol, hexites such as mannitol, dulcitol, sorbitol and galactide;

Di- and polyhydroxy aldehydes such as glyceraldehyde, triose reductone, especially sugars (aldoses) such as mannose, galactose and glucose;

Di- and polyhydroxy ketones such as especially sugar (ketoses) such as fructose;

Di- and polysaccharides such as sucrose, maltose, lactose, cellubiose 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 are the monocarboxylic acids derived from sugars, in particular gluconic acid and heptagluconic acid, and their salts, esters and lactones.

Mixtures of the complexing agents can of course also 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 higher temperatures.

Metal ions which preferably also form stable complexes with the complexing agent according to the invention are used as metal ions M2. Divalent metal ions are particularly preferred, calcium ions being very particularly preferred.

Particularly preferred mediator systems according to the invention contain iron (II / III) ions as metal ion Ml, calcium ions and as metal ion M2 as a complexing agent gluconic acid and / or heptagluconic acid.

The particular advantages of the mediator systems according to the invention are that they are not only in the pH range customary for dye reduction (about 12.5 to 13.5), but also at a low concentration of low-valent metal ion Ml and thus a low concentration of active complex Redox potential <-700 mV, but also at lower pH values, ie at about 11 to 12, form a stable complex system, that is to say, overall, they are outstandingly suitable as mediators for electrochemical dyeing, in particular with indigo.

It was not to be expected that the redox potential of the electrochemically active complex would shift so clearly to more negative values due to the presence of the electrochemically inactive metal ion. To illustrate this effect, the redox potentials determined using electrochemical conversion tests for a mediator system consisting of iron, calcium and gluconate ions are shown below. The respective iron (II) / iron (III) ratio was determined photometrically with 1, 10-phenanthroline.

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

The process according to the invention for reducing vat dyes and sulfur dyes is of particular importance, the classes of indigoid dyes, anthraquinone dyes and dyes based on more condensed aromatic ring systems and sulfur-boiling and baking-sulfur dyes being mentioned. Examples of vat dyes are indigo and its bromine derivatives, 5, 5 '-dibromoindigo and 5, 5', 7, 7 'tetrabromoindigo, and thioindigo, acylaminoanthraquinones, anthraquinonazoles, anthrimides, anthrimidecarbazoles, phthaloylacridones, benzanthrones and indanthrone, pyranthrones, and indanthrone, indanthrone and indanthrones, To name pyranthrones, acedianthrones 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 reducing the dye, the stoichiometric amount of mediator required for the dye reduction is usually used as the maximum amount. Per mole of an oxidized dye which takes up two electrons per molecule in order to convert m to the leuco form, 2 moles of a mediator system according to the invention are generally calculated, based on the redox-active metal ion providing an electron. Of course, this amount of mediator can be reduced by the electrochemical regeneration of the mediator (in the case of dyeing with vat dyes, based on one liter of dye bath, generally reduced to about 0.1 to 1 mol of mediator per mol of dye). The greater the deficit in the mediator system, the higher the demands on the electrolytic cell.

The reduction process according to the invention can advantageously be part of the process according to the invention for dyeing cellulose-containing textile material with vat and sulfur dyes. The dye is preferably added to the dye bath in a pre-reduced form, e.g. an alkaline solution of catalytically reduced indigo, and reduces the proportion of the dye reoxidized by air contact during dyeing electrochemically with the aid of the mediator systems according to the invention.

The coloring itself can be carried out as described in the literature mentioned at the beginning. All known continuous and discontinuous dyeing methods, e.g. after the pull-out procedure and the foulard procedure.

Depending on the respective dyeing process and the dyeing apparatus used, the amount of air admitted varies, and in some cases considerable amounts of mediator system are required to capture the atmospheric oxygen. For example, an additional when dyeing with vat dyes at medium depths

Requires about 1 to 10 moles of reduced mediator per mole of dye and for contour dyeing with indigo of about 2 to 10 moles of reduced mediator per mole of indigo.

The other process conditions, such as the 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 at the outset. All cellulose-containing textile materials can be advantageously dyed using the dyeing method according to the invention. Examples include: fibers from cotton, regenerated cellulose such as viscose and modal, and bast fibers such as flax, hemp and jute. Forms of presentation include, for example, flake, ribbon, yarn, twine, woven fabric, knitted fabrics, knitted fabrics and made-up pieces. Mechanical forms can be packing systems, yarn strand, bobbin, warp beam and fabric beam as well as piece goods in the strand and wide.

example

Colors with indigo from the production of denim

"250 ends" of cotton yarn (Nm 11.4, Ne 6.75 / 1) was used on a laboratory dyeing machine (Looptex, Lugano, Switzerland) coupled to an electrolysis cell, which is used for dyeing cotton yarn after sheet dyeing and rope -dye g method is suitable, dyed with indigo.

The electrolytic cell was a multi-cathode cell (10 electrodes, 400 cm ² viewing area, total area 1.9 m ² ). 5% by weight sulfuric acid was used as the anolyte. The catholyte (dye bath) and anolyte were separated by a cation exchange membrane. A stainless steel screen mesh was used as the cathode, and a titanium electrode coated with platinum mixed oxide was used as the anode.

The dyeing procedure was as follows:

The cotton yarn was first pre-wetted in a cold wetting agent liquor (3 g / 1 of a commercial wetting agent) and, after squeezing to 75% liquor absorption, the dyebath described below (11.25 l, room temperature) was immersed. After a dipping time of approx. 25 seconds and squeezing to 75% liquor absorption, the yarn was oxidized in air at room temperature for 120 seconds. This process ("train"), i.e. Dipping ms dye bath, squeezing and air oxidation was repeated several times. The dyed yarn was then rinsed with deionized water and dried.

The dye bath adjusted to pH 11.3 had the following composition:

0.24 mol / 1 iron (III) chlorine (40% by weight aqueous solution; 68.5 ml / 1) 0.30 mol / 1 sodium gluconate (99% ιg; 65.4 g / 1)

0.12 mol / 1 sodium heptagluconate (22.5% by weight aqueous solution;

115 ml / 1) 0.24 mol / 1 calcium chloride (78.5% by weight aqueous solution; 29.6 g / 1)

1.15 mol / 1 sodium hydroxide solution (50% by weight, about 63 ml / 1)

The dye bath was reduced before the start of dyeing. After 5 mm of electrolysis at 5 A, a potential of -700 mV was reached, the cell voltage was 6.6 V. Subsequently, a 20% by weight, alkaline-aqueous leuco digigo solution (BASF) was added to the reduced dye bath, which was then used for dyeing was used.

The following 3 series with 4, 6 and 8 draws (3 colorations each) were colored:

1st series:

45 ml of the leukoma digigo solution (corresponding to 1 g indigo / 1 dye bath), pH in the dye bath 11.35.

2nd series:

90 ml of the leukoma digigo solution (corresponding to 2 g indigo / 1 dye bath), pH in the dye bath 11.4.

3rd series:

180 ml of the leukoma digigo solution (corresponding to 4 g indigo / 1 dye bath), pH value in the dye bath 12.5.

Colorings of excellent quality were obtained which corresponded to standard colorations with hydrosulfite as reducing agent in the color depth and through-coloring.

Claims

claims

1. Mediator systems, obtainable by mixing a salt of an electrochemically active, complex-forming metal (Ml), which can form several valence levels, with a hydroxyl-containing complexing agent, which can also be in the form of a salt, and a salt of an electrochemically inactive, also complex-forming metal (M2) in an alkaline aqueous medium, the molar ratio of metal ion M2 to metal ion Ml being 0.8: 1 to 2: 1.

2. Mediator systems according to claim 1, which contain iron (II) ions and / or iron (III) ions as metal ion Ml.

3. Mediator systems according to claim 1 or 2, which contain divalent metal ions as metal ion M2.

4. mediator systems according to claims 1 to 3, which contain calcium ions as metal ion M2.

5. Mediator systems according to claims 1 to 4, which contain hydroxyl-containing aliphatic carboxylic acids as complexing agents.

6. Mediator systems according to claims 1 to 5, which contain iron (II / III) ions as metal ion, calcium ions as metal ion and gluconic acid and / or heptagluconic acid as complexing agent.

7. A process for the electrochemical reduction of dyes in an alkaline aqueous medium using metal complexes as mediators, characterized in that a mediator system according to claims 1 to 6 is used.

8. The method according to claim 7, characterized in that it is used for the reduction of vat dyes and sulfur dyes.

9. A process for dyeing cellulose-containing textile material with vat dyes or sulfur dyes with electrochemical dye reduction in the presence of metal complexes as mediators, characterized in that a mediator system according to claims 1 to 6 is used.

10. The method according to claim 9, characterized in that the dye is added to the dye bath in a pre-reduced form and the portion of the dye reoxidized by air contact during the dyeing is reduced electrochemically with the aid of the mediator system.

11. Cellulose-containing textile materials, dyed by the process according to claim 9 or 10.