Fixing agent is one of the important auxiliaries in printing and dyeing industry, which can improve the color fastness to wet treatment of dyes on fabrics. Insoluble colors can be formed with dyes on fabrics to improve the color fastness to washing and sweating, and sometimes improve the color fastness to lighting.
Commonly used dye fixing agents are cationic quaternary ammonium salts, such as cetylpyridine chloride, cetylpyridine bromide, propylene bis (hexadecyl dimethyl ammonium chloride); amine formaldehyde resin type dicyandiamide formaldehyde primary condensate (fixing agent Y, M); polyamine condensate (silk fixing agent LA); phenolic condensate (cross-linking fixing agent DE); cross-linking fixing agent (IndosCR); reactive dye fixing agent, and Phenolic sulfonic acid formaldehyde condensate used as fixing agent instead of tannin on nylon (polyamide) fabrics, etc.
Third, fixing mechanism
Fixing mechanism: A polyaminedyeing fixing agentself-condensation form film, which is impregnated in solution, and the fixing agent molecules adhere to the fabric. When the fabric is treated at about 100 degrees, the fixing agent molecules condense to each other, forming a larger molecular weight network structure attached to the fabric surface and a layer of film, covering the dye in the film, thereby improving the fastness of the dyeing; B fixing agent binds to dyes and fibers. The end of fixing agent molecule has - NH2 group, while cotton fiber macromolecule also has active group, such as - OH, which is condensated during baking, so that fixing agent molecule and fibre macromolecule are covalently linked. At the same time, there are active groups in dye molecule, such as OH or - NH2. Biocovalent binding; C ion bonding. polyamine type dye fixing agents is generally anionic dyes, so they can be positive and negative charge absorption, in the form of ionic bonds.
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