EP1527228A1

EP1527228A1 - Method for dyeing with sulphur and sulphur vat dyes

Info

Publication number: EP1527228A1
Application number: EP03766263A
Authority: EP
Inventors: Thomas Bechtold; Wolfgang Schrott; Thorsten HÜLS; Marc-Steffen Muche; Bertram Wendt
Original assignee: Dystar Textilfarben GmbH and Co Deutschland KG
Current assignee: Dystar Textilfarben GmbH and Co Deutschland KG
Priority date: 2002-07-31
Filing date: 2003-07-23
Publication date: 2005-05-04
Anticipated expiration: 2023-07-23
Also published as: DE10234825A1; JP2005534820A; KR20050026542A; BR0312606B1; MXPA05001097A; ATE430831T1; CN1665983A; ES2326315T3; AU2003250143A1; EP1527228B1; US20050257327A1; BR0312606A; CN100351459C; WO2004013406A1; ZA200409847B; TWI276722B; TW200407485A

Abstract

The present invention relates to a process for dyeing fiber materials with sulfur dyes by regenerating the dyebath redox potential, which comprises, during the dyeing process, the dyeing liquor being circulated between the dyeing apparatus and an attached electrolytic cell and the sulfur dye which has been unwantedly oxidized in the dyebath being cathodically reduced in the electrolytic cell.

Description

description

Process for dyeing with sulfur and sulfur vat dyes

The present invention relates to a method for dyeing fiber materials with sulfur and sulfur vat dyes

The group of sulfur or sulfur vat dyes (hereinafter only called sulfur dyes) comprises dyes of the same manufacturing principle and the same dyeing method. The sulfur dyes are formed by reacting suitable organic substances with sulfur, alkali sulfides or alkali polysulfides. The resulting products contain repetitive organic

Structural elements that are connected to one another via disulfide groups. In most cases, the chemical constitution is not known with certainty. For the purpose of dyeing, the sulfur dyes are reduced using different reduction processes, with some of the disulfide bridges being reductively cleaved (see equation 1). The resulting products have lower molar masses, are soluble in aqueous alkaline solution and can be used for the purpose of dyeing, since they also have an affinity for fibers, e.g. Have cellulose fibers. In the presence of atmospheric oxygen there is a more or less complete reoxidation of the dye according to equation 2.

(1) RSSR + 2e -> RS ^" + RS ^"

(2) RS ^" + RS- + 1 / 2O, + H ₂ O <-> RSSR + 2OH ^"

Since during the dyeing process the dye bath containing the reduced dye must be protected against undesired oxidation of the dye by air, either reducing chemicals are added to the dyebath or there is a further cathodic dye reduction during dye production or preparation of the dyeing liquor (see WO 99/1 1 71 6). In the procedure according to WO 99/1 1 71 6, the reduced dyes can be dispensed with in the production of the reduced dyes and when they are used in continuous dyeing processes, if the dye concentration used is sufficiently high, for example 50 g / l solid sulfur dye, so that the reduction equivalents introduced into the dye liquor with the reduced dye can compensate for the disruptive influence of air oxidation. Such a procedure is particularly suitable for the production of relatively concentrated products or dye liquors, which are only exposed to the oxidative action of atmospheric oxygen for a short time during continuous dyeing. With a content of 25 l in the dyeing chassis, the chassis volume can be exchanged within less than 3 minutes at a usual fabric speed of 60 m / min, a running meter weight of 200 g / m and a fleet absorption of 80%.

For the use of sulfur dyestuffs in pull-out dyeing, e.g. the state of the art does not provide a corresponding method of working on dyeing apparatus, jet dyeing equipment, etc., which also includes the continuously operating warp yarn dyeing equipment for denim production. The long dyeing time results in long dwell times of the dye in the dye bath, which is exposed to the oxidative action of atmospheric oxygen during this time. In addition, the dye concentrations used in the pull-out dyeing are already relatively low at the start of dyeing and continue to decrease due to the bath extract during the dyeing process. The instability of the dyebath against undesirable air oxidation therefore increases more and more with the duration of the staining. For clarification, the following calculation of a typical example is used for a dark color in the pull-out process:

With a liquor ratio of 1: 1 0 and a color depth of 5% (calculated as a solid sulfur dye), there is a liquor ratio per kg of fiber material. a total of 50 g of dye in 10 l of dyebath, so that an application concentration of 5 g / l is calculated as the initial concentration. If one bases the dyeing process on a bath extract of 70%, the concentration of dye has decreased to 1.5 g / l dye at the end of the dyeing process. In the dyeing processes which are known from the prior art, bath stabilization against oxidative influences can therefore only take place in the pull-out dyeing works by adding appropriate amounts of reduction chemicals such as glucose or hydroxyacetone. If these additives are not used, uncontrolled reoxidation of the sulfur dye takes place during the dyeing process. As a result, lack of reproducibility of color depth, irregularities and poor rub fastness are observed.

In warp dyeing systems, relatively high concentrations of dye are usually used (50 g / l solid dye) and relatively high liquor volumes are present in the dyeing system, so that a higher bath stability compared to

Air oxidation appears to exist. With these dyeing techniques, however, the baths are required to be used for a very long time, since the dye bath is usually used with wet goods and therefore only small amounts of dye liquor are discharged from the dye baths. With a bath volume of 4000 I and a production volume of 15000 kg warp yarn per day, with a squeezing effect of 70% when pre-wetting and 95% when dyeing, 1 5000x0.25 = 3750 I liquor consumption per day, so that the dyeing liquor has an average residence time is calculated in the system from 1 day. If the use of reducing agents is dispensed with here, there would be so-called end sequences, i.e. color variations within a dye section of e.g. 20000 m length unavoidable.

Ways of using indirect cathodic reduction methods have also been proposed in the literature. See, for example, Textilveredlung 32 (1 997) 204-209, Journal of Applied Electrochemistry 28 (1 998) 1 243-1 250, Recent Res. Devel. in electrochemistry. 1 (1 998) 245-264 and WO 90/1 51 82. In these processes, a regenerable redox system takes over the task of the soluble reducing agent, so that the required bath stability is guaranteed is. Examples of such systems are anthrachinoid bodies, with iron complexes

Amines or hydroxycarboxylic acids. Even with these processes, the use of chemicals cannot be avoided.

The present invention is based on the surprising finding that sulfur dyes can also act as mediators in the case of pull-out dyeings and that sufficient bath stability can be achieved if a continuous regeneration of the reduction state can be achieved. According to the present invention, this is achieved in that a sufficient circulation of the dye bath is made possible by a suitably coupled electrolysis cell during the dyeing process.

The present invention thus relates to a process for dyeing fiber materials with sulfur dyes with regeneration of the dye bath redox potential, which is characterized in that the dyeing liquor circulates between the dyeing system and a coupled electrolysis cell during the dyeing process and the sulfur dye which is undesirably oxidized in the dye bath is cathodically reduced in the dye bath.

The process according to the invention can be carried out, for example, as an exhaust process, but also according to the continuous process. Accordingly, dyeing machines such as yarn dyeing machines, reel runners, tree dyeing machines, jet or overflow dyeing systems are used as dyeing systems in the exhaust process. In contrast, the dyeing systems customary for this method are used for the continuous process.

The dye bath must be circulated between the dyeing machine and the electrolysis cell in accordance with the dye concentration and the oxidative load. With a high oxidative load and low dye concentration, the circulation has to achieve larger volume flows than with a high dye concentration and low oxygen pollution. The cathodically reduced dye reaches the electrolysis cell

Dyeing machine, the partially oxidized dye bath flows from the dyeing machine to

Electrolysis cell. The required fleet exchange in l / min between

The electrolysis cell and dyeing system depend on several framework conditions. These include, for example, dye concentration, more desired

Degree of reduction in the dyeing system, maximum degree of reduction which can be achieved for a sulfur dye by cathodic reduction, minimum degree of reduction of the sulfur dye required in terms of dyeing technology, current density which can be used in cell technology, and also the oxygen input into the dyeing system (oxidative load).

With the high concentrations of sulfur dye, as is common in warp yarn dyeing processes, batchwise regeneration of the sulfur dye and thus intermittent bath circulation can also be carried out. With knowledge of the present invention and the essentials mentioned

The required exchange of materials between the cell and

Dyeing apparatus can also be easily calculated by an average specialist.

If, for example, one assumes a current of 1 0A per kg of material to be compensated for the oxygen input and assumes that the amount of dye available in the dye bath circulation is 0.01 mol / l, then a dye bath circulation of 5 l / min is required in order to achieve this sales in the cell did not allow the dye concentration to rise above 10%. At a circulation rate of 101 / min kg, the dye solution changes in the reduced state by only 5%.

Depending on the general conditions, the liquor exchange ranges between 0.51 / min kg and 1001 / min kg, preferably between 1 and 50 l / min kg and very particularly preferably between 5 and 30 l / min kg, based on a kg of material to be dyed.

The dye concentration in the dyebath in the process according to the invention is preferably 0.5 to 100 g / l pure dye, particularly preferably 5 to 50 g / l pure dye. The process according to the invention is advantageously carried out at temperatures of 20 to 1 35 ° C, with 60 to 95 ° C being particularly preferred.

In a preferred embodiment of the method according to the invention, the dyeing process is influenced by controlling the redox potential. This is done by adjusting the cell current, as a result of which the redox potential in the dyebath can be changed or regulated within certain potential limits. The adjustable potential range is determined by the sulfur dye used, its concentration, as well as by pH and dyeing temperature.

The cell current is defined in particular by the oxygen input and ranges between 0.5 and 50 A / kg, preferably between 1 and 10 A / kg in conventional dyeing plants. By applying appropriate measures, such as

In an inert gas atmosphere made of nitrogen, for example, the values can be reduced.

The pH of the dyebath is, for example, between 9 and 1 4, preferably between 1 1 and 1 3. The redox potential in the dyebath is determined by the dye and the desired one

Color loss defines and is between - 300mV and - 900mV, preferably between - 400mV and - 700mV.

An electrolysis cell with a liquor circulation is coupled to the dyeing system. Conventional electrolysis cells available from cell manufacturers or commercially available can be used as electrolysis cells. Normal or multi-cathode cells can be used. In order to avoid anodic reoxidation of the sulfur dye, the electrolysis cell is preferably designed as a divided cell, a membrane electrolysis cell again being used particularly preferably. A cation exchange membrane very particularly preferably serves as a separator. Alkaline solutions, preferably alkaline solutions, are preferred as the conductive electrolyte

Solutions of alkali salts, in particular sodium hydroxide, potassium hydroxide,

Soda, table salt or Glauber's salt. The is particularly preferred for

Dye bath added lye, advantageously sodium hydroxide, potassium hydroxide or soda used. Also the salts added during dyeing, preferably table salt or

Glauber's salt can improve conductivity as electrolytes.

In a further preferred embodiment of the process according to the invention, this is carried out under an inert atmosphere. For this purpose, the dyebath is overlaid with nitrogen or an inert gas, particularly preferably argon, in the dyeing apparatus.

Since the basic oxidative load is reduced by reducing the partial pressure of atmospheric oxygen, the required electrolytic cells can be dimensioned with smaller cell currents and thus more economically.

The process according to the invention can be used without restriction for all sulfur dyes. Oxidized dyes, filter cakes from synthesis, as well as cathodically or chemically pre-reduced dyes and dye preparations can be used. Sulfur dyes produced by cathodic reduction, as described for example in DE-A 1 906 083 or WO 99/1 1716, are particularly preferably used.

According to the method according to the invention, all fiber materials can be dyed which are basically dyeable with sulfur dyes. These are in particular fiber materials made from cellulose and polyamide, as well as from cellulose / polyester and cellulose / polyamide mixtures. Fiber materials preferably mean textile fiber materials.

When dyeing with sulfur dyes, the dye is added to the dye bath

Atmospheric oxygen reduced by the existing reduced sulfur dye. In the method according to the invention, the redox behavior of the Sulfur dyes, which is characterized by several stages of reduction

(see, for example, Journal of Applied Electrochemistry 28 (1 998) 1 243-1 250 and Recent Res. Devel. in Electrochem. 1 (1 998) 245-264), by working with sufficient cell circulation and cathodic post-reduction of the oxidized sulfur dye , so that stable bath conditions can be realized.

In the process according to the invention, the sulfur dye takes on the task of reducing agents or cathodic regenerable mediators which were previously indispensable in the exhaust process. The use of chemicals, which cause costs for procurement and wastewater disposal, can therefore be dispensed with and an advantageous overall ecological balance is obtained. Unexpectedly, the low concentrations of sulfur dye, such as are used in exhaust processes, are sufficient to carry out the process according to the invention. The process according to the invention is very particularly advantageous when dyeing on a standing bath, where only the sulfur dye discharged with the goods has to be added to the dye bath.

The following application examples 1-5 show typical possibilities for the method according to the invention. In order to clearly demonstrate its effect, the sample colorations were started with oxidized sulfur dye, which is not suitable for dyeing and can only be applied to the material after cathodic reduction.

Application example 1 - dyeing in the exhaust process with Sulfur Black 1

A cell divided by a cation exchange membrane is used as the electrolysis cell.

Cathode: stainless steel cathodes, total area (surface) cathode 0.43 m ² area, total volume 2 I.

Anode: stainless steel plate with an area of 0.01 m ² . Volum en 0.3 I. 0.1 M NaOH is used as the anolyte. Cell current: 0.9 A, cell voltage between 2.7 V and 4.1 V

The dyebath (2 l total volume) is passed through the filter at 1 50 ml / min

Pumped cathode space, so that a continuous regeneration of the dye bath takes place by exchange with the catholyte.

Dyebath / catholyte composition:

1 0 g / l paste Cassulfon ^® Carbon CMR from DyStar Textilfarben GmbH & Co.

Germany KG

0.6 g / l wetting agent 3 g / l NaOH

There is a bleached cotton knit (pattern 1) with a in the dye bath

Mass of 6.9 g. The liquor circulation and heating is carried out by a

Magnetic stirrer.

The catholyte temperature is brought to 70 ° C. During an electrolysis time of 1 97 min, the redox potential drops by - 259 mV (vs. Ag / AgCI, 3 M KCI

Reference) to - 499 mV. The colored sample 1 is removed, rinsed with water and oxidized with peroxide / acetic acid in accordance with the usual methods.

Another sample (sample 2, mass 6.9 g) is introduced into the dyebath and dyed for 30 minutes while continuing the electrolysis process. The redox potential drops to - 545 mV. The sample 2 is removed after 30 minutes and finished as already described.

The pH value of the dyebath is approx. 1 2.2

The color depth can be described by measuring the color location.

Results:

As the L values show, pattern 2 is darker, although the dyeing time was shorter. This is due to the further development of the redox potential in the dye bath. Despite the low dye concentration, the successful dye reduction under the conditions of exhaust dyeing can be confirmed.

Example of use 2 - dyeing in the exhaust process with Sulfur Black 1

A cell divided by a cation exchange membrane is used as the electrolysis cell.

Cathode: stainless steel cathodes, total area (surface) cathode 0.43 m ² area, total volume 2 I. Anode: stainless steel plate with 0.01 m ² area. Volum en 0.3 I. 0.1 M NaOH is used as the anolyte. Cell current: 0.9 A, cell voltage between 3.0 V and 4.7 V

The dye bath (2 l total volume) is pumped through the cathode compartment at 150 ml / min so that the dye bath is continuously regenerated

Exchange with the catholyte takes place.

Dyebath / catholyte composition:

1 0.5 g / l Paste Cassulfon ^® Carbon CMR from DyStar Textilfarben GmbH &

Co. Deutschland KG 0.6 g / l wetting agent

3 g / l NaOH

There is a bleached cotton knit (pattern 3) with a in the dye bath

Mass of 6.8 g. The liquor circulation and heating is carried out by a

Magnetic stirrer. The catholyte temperature is brought to 62-64 ° C. During one

Electrolysis time of 1 75 min, the redox potential drops by - 309 mV (vs.

Ag / AgCI, 3 M KCI reference) to - 440 mV. The colored pattern 3 will removed, rinsed with water and used according to the usual procedures

Peroxide / acetic acid oxidized.

Another sample (sample 4, mass 7.0 g) is introduced into the dyebath

Colored for 80 min while continuing the electrolysis process. The redox potential is - 437 - -431 mV during this time. The sample 4 is removed after 80 minutes and finished as already described.

The pH of the dyebath is approx. 1 2, 1 - 1 2.2.

The color depth can be described by measuring the color location.

Results:

As the L values show, sample 4 is darker, although the dyeing time was shorter.

This is due to the further development of the redox potential in the dye bath. Despite the low dye concentration, the successful dye reduction under the conditions of pull-out dyeing can be confirmed.

Application example 3 - dyeing on a laboratory denim dyeing machine

Electrolysis cell:

The electrolysis cell is divided by a cation exchange membrane

Cell used.

Cathode: stainless steel cathodes, total area (surface) cathode 1 m ² , volume

Total catholyte 1 0 1. Anode: Ti electrode with mixed oxide coating, expanded metal with 0.04 m ² geometric area. Volume 1, 5 I.

1 M NaOH is used as the anolyte. Cell current: 1 0 A, cell voltage between 3.0 V and 4.7 V

A Looptex laboratory dyeing machine for denim dyeing is used as a dyeing machine

Cell coupled. After an electrolysis time of 1 7.5 hours at 1 0 A (75 Ah) to reach the staining potential, part of the catholyte (4 I) is removed from the cell into the

Staining system pumped and at a temperature of 50 ° C (-491 mV) is a sample

5 or at 80 ° C (-557 mV) pattern 6 colored (gamstrings with a length of

1 50 m, raw cotton yarn).

Dyeing program: pre-wetting (3 g / l wetting agent), squeezing, diving in the sulfur bucket, squeezing, air oxidation, then rinsing in cold water.

After dyeings 5 and 6, the dye bath is returned to the cell and reduced again by cathodic reduction.

After a reduction time of 3.7 hours at 10 A (3.7 Ah), part of the cell content is conveyed back into the dyeing system and samples 7 (57 ° C, -

538 mV) and 8 (83 ° C, -536 mV) colored according to the program already described.

Total volume of the dye bath: 1 2 I

Dye bath / catholyte composition: 80.25 g / l filter cake Sulfur Black 1 (50% water content)

2.0 g / l wetting agent

4 ml / l 50% sodium hydroxide solution

The regeneration of the bath contents can thus maintain the

Reduction state can be guaranteed. The pH value of the dyebath is approx. 1 2.5 - 1 2.7.

The color depth can be described by measuring the color location. Results:

Application example 4 - EC dyeing of EC-reduced sulfur black

A solution of 20 ml / l Cassulfon Carbon CMR from DyStar Textilfarben GmbH & Co. Deutschland KG (approx. 30-40% solution of Leuco Sulfur Black 1) becomes anhydrous at pH 12 in the presence of 20 g / l Na ₂ SO ₄ and room temperature electrolyzed in a system according to Application Example 1. Sodium hydroxide solution (40 g / l NaOH) is again used as the anolyte. The solution of the reduced sulfur dye has a content of reducing agent equivalents of 0.075 mol / l at the start of the electrolysis in iodometric titration. The cathodic reduction is carried out in accordance with the low sulfur dye content in the catholyte at a current density of 0.26 mA / cm ² . The electrolysis is terminated at an analytically determined content of 0.125 mol / l. The solution now has a reducing agent equivalent content of 335 Ah based on 1 kg of solid sulfur dye. The solution of the sulfur dye thus prepared can be used directly for dyeing, for example as described in Application Example 1. Application example 5 - dyeing in the exhaust process with Sulfur Black 1 on a jet dyeing machine under protective gas (nitrogen atmosphere)

The electrolysis cell is divided by a cation exchange membrane

Cell used.

Cathode: three-dimensional stainless steel cathodes, visible surface cathode 60x55 cm, 0.33 m ² surface, total volume and cathode space 100 I.

Anode: Titanium electrode with Pt mixed oxide coating with an area of 0.3 m ² . 0.1 M NaOH is used as the anolyte.

Cell current: 85 A, cell voltage between 5.3 V and 5.7 V

The dye bath (230 I total volume) is pumped through the cathode compartment so that the dye bath or the reduced dye is continuously regenerated by exchange with the catholyte. Dyebath / catholyte composition:

4.5 g / l paste Cassulfon ^® Carbon CMR from DyStar Textilfarben GmbH & Co. Germany KG (= electrochemically pre-reduced dye) 1.0 g / l wetting agent 7 g / l NaOH 38 ° B§

There is a pre-washed, bleached cotton knit with a mass of 8 kg in the dye bath. Fleet circulation and goods movement are carried out by the pump on the jet. Indirect steam heating is used for heating. The coloring is carried out under a protective gas atmosphere (nitrogen) in order to minimize air entry. For this purpose, a volume flow of 10 i / min nitrogen is continuously fed into the apparatus.

The goods speed is 50 m / min. The liquor circulation through the cell is 30 l / min. The catholyte temperature is brought to approx. 55 ° C, then the cell circulation is coupled and further heated to 76 ° C. During one

Electrolysis time of approx. 80 min is the redox potential measured in the cell between - 630 mV and - 720 mV and measured in the jet dyeing machine between - 460 mV and - 432 mV (vs. Ag / AgCI, 3 M KCI reference).

The pH value of the dyebath is approx. 12.1 - 12.2.

After rinsing in the overflow, the black colored ones are finished

Goods in the usual way, for example by oxidation with hydrogen peroxide /

Acetic acid, rinsing and exhaust.

Claims

claims

1 . Process for dyeing fiber materials with sulfur dyes with regeneration of the dye bath redox potential, characterized in that the dyeing liquor circulates between the dyeing system and a coupled electrolysis cell during the dyeing process and the sulfur dye which is undesirably oxidized in the dye bath is cathodically reduced in the electrolysis cell.

2. The method according to claim 1, characterized in that the dyebath redox potential is regulated by the cell current.

3. The method according to claim 1 and / or 2, characterized in that a divided electrolysis cell, particularly advantageously a membrane electrolysis cell, is used as the electrolysis cell.

4. The method according to one or more of claims 1 to 3, characterized in that alkaline solutions, particularly preferably alkaline solutions of alkali salts, in particular sodium hydroxide, potassium hydroxide, soda, common salt or Glauber's salt, are used as the lead electrolyte.

5. The method according to one or more of claims 1 to 4, characterized in that the dye concentration in the dyebath is 0.5 to 100 g / l of pure dye, particularly preferably 5 to 50 g / l of pure dye.

6. The method according to one or more of claims 1 to 5, characterized in that it is carried out at temperatures of 20 to 135 ° C, particularly preferably 60 to 95 ° C.

7. The method according to one or more of claims 1 to 6, characterized in that it is carried out under an inert atmosphere.

8. The method according to one or more of claims 1 to 7, characterized in that those made of cellulose or polyamide or of cellulose / polyester or cellulose / polyamide mixtures are used as fiber materials.