Application of water soluble anionic dyes to solvent-treated polyester

Solvent-treated polyester is easily penetrated by nonionic fluorescent dye from an aqueous bath. Direct dyes exhaust onto the treated fiber from an aqueous solution containing salt, and the dried, dyed fiber is fast to aqueous washing. Low molecular weight dyes containing a single sulfonic acid substituent exhaust well onto solvent- treated polyester but not onto cellulose. Low molecular weight dyes containing un symmetrically placed sulfonic acid substituents fail to dye either solvent-treated poly ester or cellulose. Dyeing is attributed principally to the sharing of hydrophobic surfaces of dye and fiber.