Fluorescent brighteners

Although strictly falling outside the scope of this book on colour chemistry, fluorescent brightening agents (FBAs) are of such importance and interest that an exception will be made in their case. The global consumption of brighteners was 170 000 tonnes in 1997 and is predicted to reach 230 000 tonnes by 2003. 

FBAs can be classified according to their application, e.g. in detergents, by far the major use, on paper, the second largest, or on a variety of textiles and plastics. Alternatively, they can be grouped according to their chemical class. In this book the latter will be used, together with an indication of the main application areas of the various major products. 

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Stilbene dyes have generally been important as direct dyes and fluorescent brighteners for ceUulosic fibers (4). Most stilbene dyes are yeUow and orange, with some examples of reds and browns and even a few blues. Brown stilbene dyes have commercial value as leather dyes (4). 

Hydroxycoumarin [93-35-6] known as umbeUiferone, occurs naturally in gum resins of umbeUiferae and is an important coumatin metaboHte. It is readily manufactured from resorcinol and maleic or fumaric acid. UmbeUiferone and fymethylumbelliferone are used as fluorescent brighteners. 

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). 

Fluorescent brightening agents, 1, 338-341 Fluoride ions nucleophilicity crown ethers and, 7, 756 Fluorides synthesis... 

The initial objective of this series of books has been to establish a coherent body of explanatory information on the principles and application technology of relevance for students preparing to take the Associateship examinations of the Society. This particular book has been directed specifically to the subject areas covered by Section A of Paper B the organic chemistry and application of dyes and pigments and of the auxiliaries used with them in textile coloration processes. However, many qualified chemists and colourists interested in the properties of colorants and their auxiliaries have found the First Edition useful as a work of reference. For several reasons it has been convenient to divide the material into two separate volumes 1. Colorants, 2. Auxiliaries. Although fluorescent brighteners share some features in common with colorants, they have been treated as auxiliary products in this book. 

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. 

A detailed study of the photostability of the DAST-type agent Cl Fluorescent Brightener 85 on cellophane film was carried out recently. The initial fading reaction is a photo-sensitised trans-cis isomerisation of the stilbene grouping. The subsequent oxidative attack on the molecule is concentrated on the vulnerable ethene linkage at the centre of this moiety [39]. 

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