Basic dyes synthetic mordants

Many brilliantly coloured and tinctorially strong basic dyes for silk and tannin-mordanted cotton were developed in the early decades of the synthetic dye industry. Most of these belonged to the acridine, azine, oxazine, triarylmethane, xanthene and related chemical classes their molecules are usually characterised by one delocalised positive charge. Thus in crystal violet (1.29) the cationic charge is shared between the three equivalent methylated p-amino nitrogen atoms. A few of these traditional basic dyes are still of some interest in the dyeing of acrylic fibres, notably as components of cheap mixture navies and blacks, but many modified basic dyes were introduced from the 1950s onwards for acrylic and modacrylic fibres, as well as for basic-dyeable variants of nylon and polyester [44] ... 

Basic dyes of the azo class were among the earliest known synthetic dyes. They were used originally for dyeing cotton mordanted with tannin and potassium antimonyl tartrate and wool from neutral solution. They continue to have minor importance for dyeing leather, paper, plastics, and waxes, and as constituents of graphic arts colors. 

In certain cases, identifying the specific garment or textile product and the allergen it contains will be an important undertaking. The fiber content of the fabric will narrow the possible dyes, as certain dyes are used to color certain fibers. Cotton, rayon, and linen fabrics are dyed with direct, fiber-reactive, mordant, azoic, sulfur, and vat dyes. Wool fabrics are dyed with acid, mordant, and fiber-reactive dyes. Polyester fabrics are dyed with disperse dyes unless the polyester is modified to accept basic dyes. Nylon fabrics are colored with acid and disperse dyes unless modified to accept basic dyes. Acrylic fabrics are dyed with basic and disperse dyes. Acetate fabrics are dyed with disperse dyes. Other synthetic fibers are dyed with disperse dyes. 

The fiber is first treated with metal salts (mordanted). Highly adhesive, basic metal compounds are formed on the fiber. These compounds are capable of producing insoluble colored complexes (lakes) with certain azo and anthraquinone derivatives. Alizarin is the best-known anthraquinone derivative for this process (see Section 2.3). It used to be isolated from the root of the madder plant but has now been replaced by the synthetic product. Suitable azo dyes contain, e.g., hydroxyl or carboxyl groups in the position ortho to the azo group on one or both of the aromatic nuclei. The shade of the dyeing depends on the type of metallic mordant used. Alizarin with aluminum or calcium salts produces the well-known Turkey red. 

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