Fibers, such as natural fibers wool and silk and synthetic fibers, for example, polyesters, such as dacron, and polyamides such as nylon are coated with a reaction product of polyhalogenated acids having a cyclic nucleus such as chlorendic acid with thiourea to render the fibers fire-resistant and self-extinguishing after removal of the initiating flame.
Flame-resistant polyamide filaments are made by treating drawn polyamide filaments with an aqueous composition of a halogenated compound selected from the class consisting of chlorendic, tetrabromophthalic and tetrachlorophthalic acids and the anhydrides thereof.
