Vinylsulfone dyes

Scheme 8.2 Reaction of vinylsulfone dyes with cellulosic fibres...

The first industrially important reactive dye systems were developed for wool, and took advantage of the chloroacetylamino [6] and the chloroethanesulfonyl groups [7], Vinylsulfonyl- and 2-sulfooxyethanesulfonyl groups were found to be applicable to both wool and cellulose. Heyna and Schumacher patented some of the first dyes of this type in the 1940s [8,9], and vinylsulfone dyes continue to be of great importance. 

In the exhaustion dyeing process, highly or moderately substantive dyes are usually employed. The optimum dyeing conditions depend on the reactivity of the dyes. Cold dyers are dyed at 30-50°C and a pH of 10-11 hot dyers at 70-90°C and a pH of 11-12. For pH control normally mixtures of sodium carbonate and sodium hydroxide are used. To enhance substantivity of the dye sodium sulfate or sodium chloride is added. For less than 0.5 % dye based on textile weight, salt concentrations of 10-30 g/L are recommended. For deep shades (more than 4%), ca. 50 g/L is used with vinylsulfone dyes having low substantivity, up to 80 g/L. 

After dyeing, the liquor is usually drained off the material is rinsed and then washed off with addition of a surfactant. The washing intensity depends on the substantivity of the dye hydrolysate. With alkali-sensitive vinylsulfone dyes, soaping at the boil must be carried out in a neutral or weakly acidic liquor to prevent cleavage of the dye-fiber bond. 

In all heat-fixing processes, optimum fixing times must be adhered to. If the times are too short, loss of color strength occurs due to incomplete dye-fiber reactions. With too long a fixing time, cleavage of the dye-fiber bond is a risk, especially for vinylsulfone dyes. After fixation, the material is washed off and dried. 

Manufacture of alkylsulfones, important intermediates for metal-complex dyes and for reactive dyes, also depends on O-alkylation. An arylsulphinic acid in an aqueous alkaline medium is treated with an alkylating agent, eg, alkyl haUde or sulfate, by a procedure similar to that used for phenols. In the special case of P-hydroxyethylsulfones (precursors to vinylsulfone reactive dyes) the alkylating agent is ethylene oxide or ethylene chlorohydrin. 

SG sols were synthesized by hydrolysis of tetraethyloxysilane in the presence of polyelectrolyte and surfactant. Poly (vinylsulfonic acid) (PVSA) or poly (styrenesulfonic acid) (PSSA) were used as cation exchangers, Tween-20 or Triton X-100 were used as non- ionic surfactants. Obtained sol was dropped onto the surface of glass slide and dried over night. Template extraction from the composite film was performed in water- ethanol medium. The ion-exchange properties of the films were studied spectrophotometrically using adsorption of cationic dye Rhodamine 6G or Fe(Phen) and potentiometrically by sorption of protons. 

The most commonly employed routes for the preparation of the / -sulfatoethylsulfone group, which is the essential structural feature of vinylsulfone reactive dyes, are illustrated in Scheme 8.5. One method of synthesis involves, initially, the reduction of an aromatic sulfonyl chloride, for example with sodium sulfite, to the corresponding sulfinic acid. Subsequent condensation with either 2-chloroethanol or ethylene oxide gives the / -hydroxyethylsulfone, which is converted into its sulfate ester by treatment with concentrated sulfuric acid at 20 30 °C. An alternative route involves treatment of an aromatic thiol with 2-chloroethanol or ethylene oxide to give the /Miydroxyethylsulfonyl compound which may then be converted by oxidation into the /Miydroxyethylsulfone. 

Practically all the commercially important reactive dyes based on activated double bonds employ the vinyl sulfone reactive group (2.35), usually as the sulfatoethylsul-fone derivative (2.34), which converts into (2.35) in the dyebath under the influence of alkali at pH 11 to 12.5. They are usually applied onto the fibre by exhaustion from the dyebath at around 40-60 °C or by cold padding at 30 °C. The vinylsulfone group is most commonly attached to the dye chromophore via an aromatic ring, e.g. Cl Reactive Black 5 (2.2), but in a few cases a bridging aliphatic group is employed. ... 

An important step forward was achieved with the introduction of double- or multiple-anchor dyes. These can be homo- or heterofunctional (mixed-anchor systems). When dyes are provided with anchors of different reactivity, a wide range of dyeing properties can be realized. At the same time, process reliability and dyefastness are improved. Thus far, combination of the triazine and vinylsulfone anchors has had the best effect. 

Alkali dosing processes with controlled addition of alkali are of great importance for dyeing the CEL component, particularly when vinylsulfone-anchor dyes are used. The control program can also allow a progressive increase in pH. Thus, the rate of absorption, which is responsible for leveling, and the rate of fixation are optimized. Occasionally, the pH is controlled by cleavable alkali-releasing chemicals. 

Figure 6.8 Chlorotriazine and vinylsulfone reactive dyes for ink-jet printing of cotton...

The most important reactive dyes in commercial use for application to cellulosic fibres in which the fibre-reactive groups react by nucleophilic addition are the Remazol reactive dyes. These dyes, based on the vinylsulfone reactive group, were introduced by Hoechst soon after the launch of the Procion dyes based on the triazine system by The chemistry of the process in which vinylsulfone... 

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