Reactive dyes - Alnus arborescens

Also known as reactive dyes. Dyes that dye by forming covalent bonds with fibers. Therefore, the dye molecules must have active groups that react with functional groups in the fibers to form covalent bonds. It is thought that the functional groups of the fibers, such as hydroxyl groups (cellulose), amino groups, carboxylic acid amide groups, or mercapto groups (wool, silk, nylon, etc.), undergo a nucleophilic substitution or addition reaction with these active groups as follows (D is the dye base):

Furthermore, a method has been developed that extends this principle and uses a crosslinking agent that reacts with both the dye and the fiber (Basazol dye). Azo dyes, anthraquinone dyes and phthalocyanine dyes are commonly used as dye bases. Reactive dyes are characterized by their excellent fastness properties, particularly in terms of wetting, sublimation and friction, as a result of the covalent bond with the fiber, and by their rich and vivid hues. Furthermore, the dyeing method is simple and no other type of dye can match their continuous dyeing properties when used for printing, etc., and it is expected that their importance will continue to increase in the future. An example is illustrated below.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

反応性染料ともいう．繊維と共有結合を形成して染着する染料．したがって，染料分子は繊維中の官能基と反応して共有結合を生成する活性基をもつことが必要である．それら活性基に対して繊維の官能基，たとえば，ヒドロキシ基(セルロース)，アミノ基，カルボン酸アミド基，あるいはメルカプト基(羊毛，絹，ナイロンなど)が次のように親核的に置換あるいは付加反応して染着するものと考えられる(Dは染料の母体)．

なお，この原理を拡張して染料と繊維の両方と反応する架橋剤を用いる方法も開発されている(Basazol染料)．染料母体はアゾ染料，アントラキノン染料およびフタロシアニン染料が多く用いられている．反応染料の特色は，繊維との共有結合の結果として諸堅ろう度中，とくに湿潤，昇華，摩擦などにすぐれ，また色相が豊富で鮮明なことである．さらに染色法が簡易でなせんなどによる連続染色性において他種染料の追随を許さず，今後，その重要性はますます増大するものと思われる．例を図示する．

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