At present, the fixing agent can be roughly divided into cationic polymer type fixing agent, resin type fixing agent (containing formaldehyde resin type fixing agent, containing polyamine resin type fixing agent), crosslinking reaction type fixing agent. The mechanism of color fixing agent is that color fixing agent can improve the dyeing fastness of aqueous solution dyes on fibers by (1) quaternary ammonium salt or tertiary amine salt in the molecules of color fixing agent, in the acidic medium, with a certain strength of positive charge and anionic groups in the structure of anionic dye ionic bond, forming insoluble color lake deposition in the fiber; (2) The reactive covalent bonding groups on the fixative molecules are covalently bonded with the active groups on the fibers and dyes; (3) In the drying process of dyed fabrics treated with fixative, the reactive cotyledo groups on the fixative molecules are self-crosslinked into macromolecules, forming a protective film with a certain strength on the fabric and fiber surface, so as to cover the dye on the fiber, so that the dye is not easy to fall off; (4) dyephilic structural groups on the fixative molecules, so that the formation of hydrogen bonds between the fixative and dye and van der Waals force combination; (5) The groups contained in the fixing agent molecules, such as imines, form coordination bonds with O, N and other atoms on the dye molecules to form chelates.

According to the fixing mechanism of the color fixing agent, the fixing agent should have positive charge in the chemical structure, have reactive cosex linking groups, can crosslink themselves and the molecular weight is large enough to form a protective film in the drying process, and contains structural groups with dye affinity, but also has the precipitation and complexation of metal ions. In addition, for formaldehyde-free color fixing agent, it is required that raw materials containing formaldehyde are not used in the production process, and formaldehyde can not be produced in the production process and color fixing process, and the dyed fabric after color fixing treatment will not release formaldehyde.