Vinyl sulfone reactive dyes

In 1958, Hoechst introduced the vinyl sulfone reactive dyes, offered as the sulfatoester from which the reactive vinyl sulfone group was generated in the alkaline dye bath. 

Recent developments show how vinyl sulfone reactive dyes can be applied on cotton by transfer printing [43],... 

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. ... 

The reactive dyes approved by the FDA are either dichloro-j -tria2ines or sulfatoethyl sulfones, termed vinyl sulfones. Both groups react with pendent hydroxyl groups on the polymer matrix. 

Fiber-Reactive Dyes. These dyes can enter iato chemical reaction with the fiber and form a covalent bond to become an iategral part of the fiber polymer. They therefore have exceptional wetfastness. Thein main use is on ceUulosic fibers where they are appHed neutral and then chemical reaction is initiated by the addition of alkaH. Reaction with the ceUulose can be by either nucleophilic substitution, using, for example, dyes containing activated halogen substituents, or by addition to the double bond in, for example, vinyl sulfone, —S02CH=CH2, groups. 

These constraints cause different reactive groups to be developed for dyeing wool. They fall into two groups novel reactive groups with more than one type of group in each molecule in order to increase the amount of dye fixed and minimise the wash-off problem, eg, Lanasol Dyes by CIBA-GEIGY, and those based on ceUulosic reactive dyes, but where the dye is appHed to the wool in a nonreactive form. On boiling, this form slowly converts to the reactive form that fixes rapidly in situ eg, the Hostalan Dyes by Hoechst, introduced in 1971 were precursors of vinyl sulfone dyes. 

Tria2inyl reactive dyes show less tendency toward hydrolysis during washing than do the vinyl sulfone type. 

Scheme 4.3 Synthesis of vinyl sulfones. The vinyl sulfone is highly electrophilic (reactive) and frequently used in fiber-reactive dyes.

Although the most commonly used reactive systems involve the halotriazine and sulfa-toethyl sulfone (vinyl sulfone) groups, halo-genated pyrimidines, phthalazines, and quinoxalines are also available (Fig. 13.14). For all of these systems, alkali is used to facilitate dye-fiber fixation, and fixation occurs either by nucleophilic substitution or addition (Figs. 13.15-13.16). 

Another important type of reactive dye is the sulfatoethyl sulfone ( vinyl sulfone ), which involves an activated vinyl sulfone grouping that can react with a cellulose hydroxy in the presence of a base, as follows ... 

The newest development in reactive dye chemistry involves the combination of different reactive types such as a monochlorotriazine and a vinyl sulfone ... 

In analogy to vinyl sulfone fiber-reactive dyes, water repellents with the vinyl sulfone function have been patented [42]. The /3-hydroxyethylsulfate group, which, in the presence of alkali forms the reactive vinyl sulfone intermediate, functions as a water-solubilizing group and gives the water repellent an amphiphilic character until reacted with alkali. 

Water repellents with a chlorotriazine or vinyl sulfone functional group react with cellulose in the presence of alkali. Therefore, they are not compatible with cross-linking reactants requiring acid catalysis for the reaction with cellulose. This limitation, in addition to the cost, is one of several reasons why fiber-reactive chemistry developed for dyes has not been successfully adaptable to repellent finishing. 

Another class of reactive dyes is vinyl sulfones such as 24.31. Why do these react readily with alkoxide anions ... 

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