Whitening/brightening agents

Dye Intermedia.tes, Dye intermediates are defined as those precursors to colorants that are manufactured within the dyes industry, and they are neady always colodess. Colored precursors are conveniendy termed color bases. As distinct from primaries they are only rarely manufactured in single-product units because of the comparatively low tonnages requited. Fluorescent brightening agents (FBAs) are neither intermediates nor tme colorants. Basic manufacturing processes for FBAs are described in Reference 18 (see Fluorescent whitening agents). 

Descriptive terms such as fluorescent whitening agents , optical brighteners and optical bleaches have all been used for the products described in this chapter as FBAs. Many of these terms have validity and the term fluorescent brightening agents is preferred here only because it has been adopted in the indexes of Chemical Abstracts. 

Colourless molecules with blue fluorescence are optical brightening agents that are used as blue whiteners in paper production and washing powders (see Chapter 7). The two main classes are heterocylics such as pyrazolines and particularly stilbenes (1). 

Triazoles and their benzo derivatives have attracted considerable attention because of their theoretical interest, and synthetic value, as well as for their numerous applications in industry and agriculture due to their extensive biological activities and their successful application as fluorescent whiteners, light stabilizers and optical brightening agents. 

The saturation limit of an optical brightening agent, however, is also dependent on the method of application to the substrate. Usually exhaust application process gives higher whiteness value then it does when applied by padding technique for a given amount of whitener. 

In contrast to wool, in silk the acid nature of the proteinic substance (fibrion) predominates, which can permit whitening with acid and basic type of brightening agents. However, for silk direct brightening agents are preferred. 

Optical brighteners are also referred to as fluorescent whitening agent or fluorescent brightening agent. 

A collection of UV spectra of plasticisers, fluorescent whitening agents (optical brighteners), UV absorbers, as well as of phenolic and aminic antioxidants was published by Hummel and Scholl [21]. UV absorbance data for isolated chromophores are listed elsewhere [22]. A general UV atlas of organic compounds is available [23]. 

Fluorescent whitening agents (LD) Create a brightening effect Substantivity on fabrics Compatibility with other ingredients like bleaches Bistriazinyl derivatives of 4,4 -diamino-stilbene-2,2 -disulfonic acid 0.1-0.5%... 

Brightening - pLUORESCENT WHITENING AGENTS] (Volll) -of mechanical pulps pULP](Vol20)... 

Optical brighteners (fluorescent whitening agents, FWAs) are used primarily in the textile, detergent, and paper industries and are also added to plastics [118], The mode of application and performance requirements differ greatly from one substrate to another, but there are five common basic principles ... 

---