These are also called cationic dyes, because in solution the basic dye molecule ionizes causing its coloured component to become a cation or positively charged radical. When the basic dyes were synthesized, the basic dyes were used on wool and silk, but they had very poor colour fastness properties.
When acrylic fibres began to establish, a new form of basic dye was evolved which is known as modified basic dyes. Used in dyeing and printing.
They tend to be extinguishable from the other classes of textile dyes by their brilliance in colour.
Suitability to textiles:
Basic dyes were formerly used on cellulosic and protein fibres, but because they produce fugitive colours (colours that fade quickly), their popularity for these fibres has been decreased.
The fibre most readily coloured with basic dyes are synthetic acrylics and modacrylic fibres.
Basic dyes are applied to acrylic fibres from slightly acidic dye liquor. Basic dyes have good substantivity for acrylic fibres and exhaust well within narrow limits of temperature. Because of their poor leveling properties, care must be exercised when applying basic dyes to acrylic fibres to avoid unlevel dyeing. This is achieved through the use of a retarder and carefully regulating the temperature during dyeing.
The colouring component of basic dyes is absorbed on the fibre surface, which is negatively charged.
Fastness properties:
Dyed and printed acrylic textiles using basic dyes have excellent light-fastness which is about 6-7. This excellent light-fastness is attributed partly to the hydrophobic nature of the fibres.
Wash fastness of acrylic textiles dyed with basic dyes is very good about 4-5. This may be attributed in part to the good substantivity of basic dyes for acrylic fibres and the hydrophobic nature of acrylic fibres.
These dyes are characterized by brilliance and intense hues. The bright colours achieved from this class do not occur with other dye classes.
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