Acid and Metal-Complex Dyes on Polyamide

Since the 1 2 dye complexes are formed in a weakly acidic medium, they can be applied to wool at a higher pH. This enables a gentle mode of dyeing. 

In the dyeing process, the pH is set at 4.5-5.5 (acetic acid, ammonium sulfate, or ammonium acetate), and the dyeing auxiliaries are added to the liquor. The dyes are added at 30-50°C the system is heated and dyed at boiling temperature. After rinsing, formic acid is used for acidification to improve the feel and wetfastness. 

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For printing with acid and metal-complex dyes on polyamide material see Section 4.10.2. 

Uses Reserving agent for polyamide fibers and wool against many acid and metal complex dyes in wet-on-wet printing... 

Practically all synthetic fibers can be printed with disperse dyes. Cationic dyes are used preferentially for acrylic fibers, and acid dyes and metal-complex dyes can be used for prints on polyamide fibers. The importance of printing with disperse dyes and the relative amount of different man-made fibers used for prints varies according to fashion and local requirements. Polyester fabrics alone or in combination with cotton are the most important. After precleaning, fabrics made from synthetic fibers must be heat-set to achieve dimensional stability and crease resistance. The usual setting conditions are 20-30 s at 190-210°C, and for texturized articles about 30°C lower. 

Note on polyamide (PA) and wool dyes. PA fibres can be dyed with a wide range of dyes, but disperse azoic, acid 1 2 metal complex acid and reactive dyes are mainly used. 

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