Cationic Resin Type
Cationic resin-type formaldehyde-free fixing agents can be produced by reacting dicyandiamide, diethylenetriamine, and hydroxymethyl urea to form imidazoline, which is cationic. This is the fixing agent DFRF-1 (produced by Shanghai Textile Auxiliaries Factory). Strictly speaking, DFRF-1 cannot be called a formaldehyde-free fixing agent because it still uses 2D resin or hydroxymethyl urea as a crosslinking agent; it can only be called a low-formaldehyde fixing agent. Condensation, deamination, and cyclization of diethylenetriamine with dicyandiamide yields the imidazoline-structured fixing agent SH-96, which is also a resin-type fixing agent. Its disadvantage is color change. Fixing agents using dicyandiamide as a raw material all exhibit color change, so the amount used must be controlled to reduce the degree of color change. Condensation of dicyandiamide with glyoxal can form a cyclic condensate, which, under normal circumstances, does not release aldehydes and also has a fixing effect. Resin-type fixing agents made using dicyandiamide as a raw material tend to have a darker color, often appearing as a brownish-red or light brown solution.
Reactive Formaldehyde-Free Fixing Agents
Reactive formaldehyde-free fixing agents are prepared by reacting epichlorohydrin with amines, ethers, carboxylic acids, amides, etc., using epichlorohydrin as the reactive group. Most are polymers with cationic and reactive groups, capable of forming salts with anionic dyes (reactive, acid, and direct dyes) and crosslinking with hydroxyl and amino groups in fibers and dyes, thereby improving their wet fastness.
