Abstract
Liquid fluorescent whitening agents (FWAs) for polyester whitening are currently produced by a top-down grinding process, which is both time- and energy-intensive and often yields products with poor storage stability. In response to this issue, this paper presents a bottom–up strategy for preparing nanoscale FWA suspensions through anti-solvent precipitation. The influence of process parameters—including stabilizer type and dosage, anti-solvent-to-solvent ratio, injection speed, stirring speed, and temperature—on particle size and stability was systematically investigated. Compared with the traditional grinding method, the developed method exhibited higher production efficiency and a considerable reduction in energy consumption. The formed nanocrystals showed a slender rod-like structure. By introducing a hyperdispersant, stable liquid FWA products with a small particle size and satisfactory whitening performance on polyester fabrics could be obtained. All the 1,4-bis-styrylbenzene (ER) FWA series, including ER-I to ER-III, could be successfully subjected to the anti-solvent precipitation method. This study demonstrates for the first time that a hyperdispersant-enabled anti-solvent precipitation strategy can produce liquid FWAs with superior stability, rod-like nanocrystal morphology, and significantly reduced energy consumption compared to the conventional grinding method.