Taking color-fixing agent Y as an example: A measured amount of dicyandiamide is added to a normal-pressure reactor and heated to dissolve. Then, a measured amount of formaldehyde solution is slowly added dropwise to the reactor while continuously stirring. Finally, ammonium chloride is used for neutralization, resulting in a transparent, viscous liquid with a certain solid content, which is the finished product. This method produces a formaldehyde-containing color-fixing agent, which has a good color-fixing effect but suffers from free formaldehyde pollution, and its use is prohibited in many products.
Example of a formaldehyde-free color-fixing agent: An aqueous solution of diethylenetriamine or triethylenetetramine is added to a reactor and heated and stirred. A measured amount of epichlorohydrin is added dropwise, and the mixture is kept at the same temperature under reflux and stirred until the product is a pale yellow, transparent, viscous liquid, which is the final product.
