Fluorescent whitener

The principle of fluorescent whitening was described in 1929 (1), but the industrial use of FWAs began about 10 years later. Since that time FWAs have found increasing use in the most diverse fields (2—5). The toxicological properties of fluorescent whiteners have been summarized (6). Commercial products investigated thus fat have been found to be completely harmless. Mote than 2000 patents for FWAs exist, there ate several hundred commercial products, and approximately one hundred producers and distributors. 

Table 1. Symmetrical Stilbene Derivatives used as Fluorescent Whitening Agents...

Other Heterocyclic Systems. Naphthalimides (15), where R = —NHCOR, are derivatives of 4-anTinonaphthalimide (69) and are used in plastics. The alkoxynaphthalimides (15, R = OCH ) (70,71) are of particular interest as fluorescent whitening agents. 

Initially, fluorescent whitening agents (FWAs) were used exclusively in textile finishing the detergent and paper industries followed thereafter. These products are also used in fiber spinning masses, plastics, and paints. 

During the drying and, if required, the heat treatment that foUows, the fluorescent whitener is fixed on the substrate. FWAs and dyes used in padding procedures must have low substantivity during the padding operation. This is an important prerequisite for level whitening with no tailing. 

In contrast to dyes, fluorescent whiteners are not appHed exclusively in special processes, but often in combination with bleaching and finishing steps. Fluorescent whiteners used in such processes must be stable and should not interfere with the operation. 

Detergent Applications. The primary function of FWAs in the laundry process is to whiten fabric load and maintain the original appearance of the white, laundered articles. Laundering is characterized by repeated appHcation to the same item. Fluorescent whiteners used in this repetitive process have to compensate for the reduction in whiteness and contribute toward prolongation of the usefiil life of the textile material. 

Table 5. Fluorescent Whitening Agents in the Detergent Industry...

Table 6. Fluorescent Whitening Agents Used in the Synthetic Fibers and Plastics Industries...

Fluorescent Whitening Agents," in F. Coulston and F. Korte, eds.. Environmental Quality and Safety Suppl. Vol. 4, Georg Thieme Vedag, Stuttgart, and Academic Press, Inc., New York, 1975. 

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