Process for preparing concentrated aqueous formulations of anionic dyes

摘要

Storage-stable concentrated aqueous formulations of water-soluble dyes are obtained when an aqueous solution or suspension of at least one crude anionic dye is passed over a semipermeable membrane that contains ionic groups and has a pore diameter from 0.1 to 50 nm in order that salts and synthesis by-products having molecular weights below 500 and some of the water be separated off, and optionally admixed with further additives before and/or after passage through the semipermeable membrane. The liquid dye formulations obtained are suitable for dyeing and printing paper and also for preparing padding liquors, dyebaths and print pastes for dyeing and printing textile materials in particular those made from cellulose, synthetic polyamide and wool.