EP0121227B1 - Process for reoxidizing dyeings with sulphur dyes - Google Patents

Description

The present invention relates to a method for reoxidation in the alkaline medium of sulfur dyes which have previously been applied in a reduced form to a textile material containing cellulose fibers and fixed there.

The dyeing of cellulose-containing textiles with sulfur dyes, be it continuous or discontinuous, is well known. Regardless of whether this is based on the actual sulfur dyes (CI Sulfur Dyes) or the soluble sulfur dyes (CI Leuco Sulfur Dyes, CI Solubilized Sulfur Dyes) or on vat sulfur dyes (CI Vat Dyes), the reduced form of a substantive leuco compound must be applied / drawn up dye after application to the dye in any case to be reoxidized for dye development.

• Am gebräuchlichsten ist die Reoxidation der Leukofarbstoffe mittels Alkalibichromat und Essigsäure. Diese Oxidationsartim sauren Medium verläuft rasch und vollständig; sie ist auch nur wenig pH-abhängig. Nachteile bei einer solchen Arbeitsweise, die aufgrund von schärfer werdenden Auflagen der Abwassergesetzgebung bezüglich Reinerhaltung der Umwelt immer stärker ins Gewichtfallen, sind hingegen, dass das Abwasser mit giftigen Schwermetallsalzen belastet wird und durch diese saure Oxidation die maschinellen Einrichtungen der Korrosion ausgesetzt werden. Letzteres trifft übrigens für alle Oxidationsverfahren im sauren Medium zu. Obendrein wird durch die Oxidation mit Kaliumbichromat/Essigsäure die Wiederbenetzbarkeit des Färbegutes verschlechtert.

Various methods have already been proposed for this reoxidatoin required for converting the soluble leuco form into the insoluble sulfur dye, but these are subject to the difficulties mentioned below under practical conditions:

• The most common is the reoxidation of the leuco dyes using alkali bichromate and acetic acid. This type of oxidation in the acidic medium is rapid and complete; it is also only slightly pH-dependent. Disadvantages of such a method of operation, which are becoming increasingly important due to the increasingly stringent requirements of wastewater legislation with regard to keeping the environment clean, are that the wastewater is contaminated with toxic heavy metal salts and the acidic oxidation exposes the mechanical equipment to corrosion. Incidentally, the latter applies to all oxidation processes in an acid medium. In addition, the rewettability of the material to be stained is impaired by the oxidation with potassium bichromate / acetic acid.

The oxidation of the leuco dyes with the aid of hydrogen peroxide in the alkaline medium does not have the shortcomings just discussed, but a strong pH dependency can be observed with such a procedure. The latter has an adverse effect on the dyeing result in undesirable color deviations within oxidation areas or from lot to lot.

In addition, in the case of continuous process control, the addition of oxidizing agents and acids is problematic in the case of acidic oxidation. Likewise, the addition of catalysts during oxidation by means of hydrogen peroxide in an alkaline environment does not bring about any significant improvement in the color yields.

The oxidative aftertreatment of cellulose fiber material dyed or printed with sulfur dyes with the oxygen in the air using a quinoid reoxidation catalyst is known from DE-A-2 434 095. This technique has remained practically meaningless.

DE-A-2 652 779 again describes a reoxidation process according to which the goods treated with pre-reduced sulfur dyes are oxidized by the action of an iodate or bromate and with the aid of a vanadate as catalyst. A nitrate is expediently added to the oxidation bath as a corrosion inhibitor. In addition to the relatively high price of the oxidizing agents, the question of color consistency and the risk of corrosion has not been addressed.

The continuous method for reoxidation of dyeings with sulfur dyes in an alkaline medium using hypochlorites, which was explained in DE-B-2 641 777, was ultimately unsuccessful because of the great problems with the dosage of the oxidants and the great prejudices against oxidation of sulfur dyes with hypochlorite push through. In addition, this known method has great difficulties with regard to the reproduction of the measures for the oxidation of the dyes.

The object of the present invention was therefore to develop a novel, environmentally friendly oxidation process for sulfur dyes which is not affected by the disadvantages of the conventional working methods described at the outset. It should also allow both continuous and discontinuous feasibility and ensure the necessary security with regard to the constancy of the color tone obtained.

worin R einen Arylrest, vorzugsweise Phenyl, oder einen niederen Alkyl-arylrest, vorzugsweise Mono-oder Dialkyl-(C₁-C₄)-phenyl bedeutet, Hai für ein Halogenatom, vor allem Chlor aber auch Brom steht, und X ein Wasserstoffatom oder Alkalimetallatom, vorzugsweise Natrium darstellt, bei einer Temperatur zwischen 15°C und 98°C und bei pH-Werten im Bereich von 8 bis 12 aussetzt. Bevorzugt wird die Reoxidation im pH-Bereich zwischen 8 und 10 durchgeführt.This object is achieved according to the invention by treating the fiber material treated with the dyes for the oxidation effect of an aqueous solution of N-halogenated organic sulfonamides of the general formula

wherein R is an aryl radical, preferably phenyl, or a lower alkyl aryl radical, preferably mono- or dialkyl- (C ₁ -C ₄ ) phenyl, shark represents a halogen atom, especially chlorine but also bromine, and X represents a hydrogen atom or Alkali metal atom, preferably sodium, exposed at a temperature between 15 ° C and 98 ° C and at pH values in the range of 8 to 12. The reoxidation is preferably carried out in the pH range between 8 and 10.

Suitable representatives according to the invention of such N-halo-aryl- or -alkylaryl-sulfonamides, which are able to give off positively charged halogen during the oxidation process, are in particular the sodium salts of benzenesulfonic acid-N-chloramide (chloramine B) and of p-toluenesulfonic acid To name -N - chloramide (chloramine T), which give equivalent coloring results. Such connections include described in Ullmann's Encyclopedia of Technical Chemistry, 4th edition, volume 9, pages 384-392 (especially pages 388 to 389) and in Kirk-Othmer, Encyclopedia of Chemical Technology, Third Edition, Volume 5, pp. 565-580 (especially pp. 574-575).

About the oxidation effect of chloramine B or T is probably already in connection with the development of indigo dyes on cotton in Chemical Abstracts, volume 48 (1954), column 9066 f have been reported without being able to derive specific statements about the oxidation conditions to be observed. However, as a person skilled in the art knows, indigosols must first be cleaved using strong acids before they are available for reoxidation. Under such acidic conditions, however, the chemicals used, which release hypochlorite in the heat, have a stronger oxidation potential than would be beneficial for the sulfur dyes which have a different oxidation behavior than the vat dyes on which they are based. It was therefore in no way obvious to design the oxidation process of N-chlorinated sulfonamides under alkaline conditions and then, reversing the order of the treatment steps compared to this literature reference, to transfer them to dyeing with sulfur dyes.

Because of the mild oxidation effect of benzene or p-toluenesulfonchloramide sodium which arises according to the present invention under the stated alkaline pH conditions, rapid and complete oxidation of the leuco compounds on the fiber material is achieved without the dye development corresponding to that of the prior art Technology is subject to common impairments. In the case of sulfur black dyeings, it is also important that the reoxidation in the alkaline pH range significantly reduces the risk of fiber damage when storing the finished dyeings.

Since the time factor is of no great importance in the oxidation mode according to the invention, the claimed process can be carried out either continuously or batchwise. In the case of continuous working technology, residence times of the material to be dyed between 5 and 120 seconds are sufficient.

It is completely irrelevant in which form the sulfur dyes have been applied to the textile materials to be dyed, whether as linked sulfur dyes, leuco sulfur dyes or as sulfur dyes solubilized by thiosulfato groups. Regardless of the application, they are present in reduced form on the fiber after fixation and must therefore be reoxidized to the insoluble dye.

stehen der Färbereipraxis preiswerte, physiologisch unbedenkliche und mit ihren Endprodukten abwassertechnisch einwandfreie Oxidationsmittel für die Entwicklung von Schwefelfarbstoffen zur Verfügung. Ihre Dosierung ist problemlos und bezüglich Einhaltung der Farbkonstanz treten keine Schwierigkeiten auf. Selbst schwierige oxidierbare Schwefelfarbstoffe werden rasch und vollständig rebxidiert. Die Korrosionsgefahr ist verfahrensgemäss gebannt. Die Mitverwendung von Reoxidationskatalysatoren ist im Zuge der beanspruchten Oxidationsmethode überflüssig.With benzenesulfonchloramide sodium (N-chloro-benzenesulfonic acid amide-Na) or p-toluenesulfonchloramide sodium (N-chloro-4-toluenesulfonic acid amide-Na) of the formulas

Dyeing practice offers inexpensive, physiologically safe and, with their end products, wastewater-free oxidizing agents for the development of sulfur dyes. Your dosage is easy and there are no difficulties in maintaining the color consistency. Even difficult oxidizable sulfur dyes are re-oxidized quickly and completely. The risk of corrosion is eliminated according to the process. The use of reoxidation catalysts is superfluous in the course of the oxidation method claimed.

wirkt, war das oben bereits genannte, tiefsitzende Vorurteil gegen jede Einwirkung von Hypochloriten auf Färbungen mit Schwefelfarbstoffen zu überwinden gewesen. Analoges Verhalten gilt für Benzolsulfonchloramid-Natrium.Since p-toluenesulfonchloramide sodium is released via the elimination of sodium hypochlorite in accordance with the equilibrium reaction (chemism given in the free acid form)

was effective, the deep-seated prejudice against any effect of hypochlorites on staining with sulfur dyes had to be overcome. The same behavior applies to benzenesulfonchloramide sodium.

To carry out the process according to the invention in practice, it is possible to use powdered sodium benzene or p-toluenesulfonchloramide with a dispersant, e.g. of the naphthalenesulfonic acid-formaldehyde condensate type to mix into an easy-to-use product. Of course, according to the present invention, the use of color-like liquid preparations of the oxidizing agent is not excluded, even advantageous. The latter allow good dosing and save the need to loosen the products.

The quantities of oxidizing agent used are expediently 0.3 to 5 g / l of benzene or p-toluenesulfonchloramide sodium in a continuous process, and 0.3 to 3% benzene or p-toluenesulfonchloramide sodium in a batch process (based on the weight of the goods) .

The following examples serve to illustrate the invention, without wishing to restrict it thereto.

example 1

enthält.150 kg of cotton yarn on packages are treated in the yarn dyeing machine with a liquor ratio of 1:10 and with changing circulation directions with an aqueous liquor which - based on the weight of the dry goods -

contains.

To carry out the pull-out dyeing, the bobbin dyeing machine is loaded with the dry goods, the bath is now set at 30 ° C. with the aids (I-IV) and the circulation liquor is left Run 10 minutes and then add the dye. Then increase the bath temperature to 90 ° C and add the sodium sulfate 10 minutes after reaching the set dyeing temperature. After a further 35 minutes of dyeing at 90 ° C, the bath and the goods are cooled to 70 ° C, after which the material to be dyed is rinsed clear with water in the overflow. Then you drain the bathroom.

frisch zubereitet und die Färbeanlage mit dieser Flotte beschickt. Unter in-Gang-setzen der Zirkulation oxidiert man nun den auf der Ware als Leukoverbindung fixierten Farbstoff während 10 Minuten bei 40°C,spütt die Färbung mit Wasser und stellt dieselbe wie üblich fertig.For the dye development, an aqueous oxidation bath with the addition of

freshly prepared and the dyeing machine is loaded with this fleet. With the circulation set in motion, the dye fixed on the goods as a leuco compound is then oxidized for 10 minutes at 40 ° C., the dye is washed with water and the same is completed as usual.

In this way, a uniform, well-oxidized color is obtained even with the dye which is known to be difficult to oxidize. However, if the oxidation of the same dye is carried out in a known manner at pH 9-10 using hydrogen peroxide, so-called blanket formation is easily caused on the dyed goods, in which the outer layers of the packages are colored darker than the inner layers.

In the present case, dye development by oxidation can also be brought about at a temperature of 15 ° C. under otherwise identical conditions.

Example 2

enthält und auf eine Temperatur von 25° C gebracht.A batch of 1200 m of cotton twill is to be dyed continuously. For this, an aqueous block bath is used, which

contains and brought to a temperature of 25 ° C.

With the liquor prepared in this way, block the goods with a liquor absorption of 80% (based on the weight of the dry goods), then dampen the dye continuously for 1 minute in saturated steam at 102 ° C and then rinse the goods with cold water in 4 washing compartments a wide washer.

• 2 g/I Benzolsulfonchloramid-Natrium oder p-Toluolsulfonchloramid-Natrium, und
• 1 g/I Soda kalz. (pH 6-10)

enthält und auf 40°C erwärmt ist, wobei für den Durchlauf der Ware eine Verweilzeit von 20 Sekunden eingehalten wird. Dieses Oxidationsbad wird laufend mit einer wässrigen Lösung von

und Soda zur Erhaltung von pH 9 nachgeschärft. Abschliessend wird die Färbung mit Wasser wiederum warm (40°C) und kalt gespült (3-4 Waschkasten) und wie üblich fertiggestellt.The dye development by oxidation also takes place in a compartment of the wide-washing machine that contains an aqueous bath

• 2 g / l benzenesulfonchloramide sodium or p-toluenesulfonchloramide sodium, and
• 1 g / l soda ash. (pH 6-10)

contains and is heated to 40 ° C, with a dwell time of 20 seconds being observed for the passage of the goods. This oxidation bath is continuously mixed with an aqueous solution of

and sharpened soda to maintain pH 9. Finally, the dyeing is rinsed with water again warm (40 ° C) and cold (3-4 wash boxes) and finished as usual.

Despite the fact that the dye used is difficult to oxidize, the dyeing thus produced is perfectly oxidized, as comparisons with samples which have been carefully oxidized in a known manner have shown.

Claims (7)

1. A process for the reoxidation, from an alkaline medium, of sulfur dyestuffs which have previously been applied, in a reduced form, to a textile material containing cellulose fibers and have been fixed thereto, which comprises exposing the fiber material which has been treated with the dyestuffs to the oxidative action of an aqueous solution of N-halogenated organic sulfonamides of the general formula

in which R denotes an aryl radical, preferably phenyl, or a lower alkylaryl radical, preferably mono-(C_i-C₄)--alkylphenyl or di-(C₁-C₄)-alkylphenyl, Hal represents a halogen atom, in particular chloride, or also bromide, and X represents a hydrogen atom or an alkali metal atom, preferably sodium, at a temperature between 15°C and 98°C and at pH values within the range from 8 to 12.

2. The process as claimed in claim 1, wherein the reoxidation is carried out within the pH range between 8 and 10.

3. The process as claimed in claim 1 or 2, wherein the reoxidation is carried out continuously.

4. The process as claimed in claim 1 or 2, wherein the reoxidation is carried out discontinuously.

5. The process as claimed in claims 1 to 3, wherein, in the case of continuous reoxidation, a dwell time of 5 to 120 seconds is maintained for the material to be dyed.

6. The process as claimed in claims 1, 2 and 3, wherein as the oxidizing agent 0.3 to 5 g/I of sodium benzenesulfochloroamide or p-toluenesulfochloroamide are used.

7. The process as claimed in claims 1, 2 and 4, wherein as the oxidizing agent 0.3 to 3% (calculated on the weight of the goods) of sodium benzenesulfochloroamide or p-toluenesulfochloroamide are used.