The polyamide has an amino group at the end of the molecular chain, and can react with an active group in a reactive dye molecule to form a covalent bond. Therefore, the reactive dye can be used for the dyeing of a nylon knitted fabric.
Dyeing characteristics
Nylon dyed with reactive dyes has a bright color, good fastness to washing and fast rubbing, and a simple dyeing method. However, due to the small amount of amino groups in the nylon molecule, the level dyeing is poor, and it is only used for medium and light color varieties.
Principle of dyeing
Reactive dye molecules all have a certain amount of sulfonic acid groups, which can bind with the ionized amino groups at the end of the nylon molecular chains in acidic conditions, so the reactive dye-up dyed nylon usually uses a weak acid bath. The dye uptake at this time is similar to that of acid dyes and mainly depends on ionic bonding. However, the affinity of amino groups is stronger than that of cellulose hydroxyls, so even under weakly acidic conditions, X- and K-type reactive dyes can be covalently bonded to the polyamide-generating moiety. KN-type reactive dyes cannot generate vinyl sulfone groups in acid baths, so they cannot be covalently bonded to nylon under acidic conditions.
Reactive dyes, like acid dyes, have high dye uptake when dyed nylon under acidic conditions, and have a dark color, but poor level dyeing. Reactive dyes with poor levelness should be dyed with nylon in a neutral bath. Low, but good levelness, only limited to light-colored varieties; dye bath can not be alkaline, otherwise it will cause the dye hydrolysis caused by reduced color, the speed is poor, but the dye even after dyeing can make dye pH Raise for fixing. During the fixing process, it is possible to free the ionically bound dye and covalently bond the active group to the fiber.
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