Process for the optical brightening of polyester fibres

摘要

Polyester fibres or fabrics are treated in an aqueous medium at a temperature not exceeding 75 DEG C. with a brightening agent which is free from water-solubilizing groups and contains at least one heterocyclic ring fused on to a benzene ring, and are then subjected to a dry heat treatment at a temperature above 100 DEG C. Specified brightening agents include the compound and a : b -di-[N-methyl-benzimidazolyl-(2)]-ethylene. The compounds may be dispersed with the aid of ethylene oxide addition products with alkyl phenols or alkyl-aryl sulphonates or other suitable agents, or may be dissolved in a watermiscible organic solvent and then added to water. The impregnation may be effected at room temperature and the fibres may then be dried at a moderate temperature (60-100 DEG C.) and heated to between 120 DEG and 225 DEG C., in a drying chamber, by ironing, or with dry superheated steam. In Example 2 the treatment bath also includes ammonia.