Stilbene Based Brighteners

In the preparation of white paper the FB A is added either at the pulping stage, prior to producing the paper sheet (one-third of the manufacture), or during a subsequent sizing procedure on the preformed sheet (two-thirds of the manufacture). The 

For many years one of the most important FB As for detergent has been the DAST based product (3.55). However, DAST brighteners are susceptible to both chlorine 

Other stilbenes of use in detergents are the DAST based (3.49), the triazolo compound (3.56), derived from DAST, and the bis-stilbene (3.57). The latter two are more stable to the newer bleaches but are also more expensive than the simpler DAST based FBAs. They are also used as premium brighteners for cotton and nylon/cotton blends. 

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Blancofor BBU Blankophor BBU C.l. Fluorescent Brightener 220 EINECS 240-521-2 Fluorescent Brightener 220 Fluorescent whitening agent (stilbene-based) Leucophor U. 

A Michaelis-Arbusov rearrangement followed by a Wittig-Horner reaction is involved in preparation of the distyrylbenzene derivative 11.37, as shown in Scheme 11.15. Precautions must be taken in the first stage to minimise formation of the carcinogenic by-product bis(chloromethyl) ether 11.16. The stilbene bis-ester 11.38 can be made by a similar procedure, or alternatively by the reaction of ethyl acrylate with 4,4 -dibromostilbene in the presence of a palladium-based catalyst (Scheme 11.16), a synthesis that yields the required trans form of the brightener. 

Compounds based on the styryl group were prepared to lengthen the conjugated system of stilbene. l,4-Di-(stryryl)-benzenes are obtained by the Homer modification of the Wittig reaction, for example, l,4-bis-(chloromethyl)benzene is treated with 2 moles of triethyl phosphate and the resulting phosphonate reacts with 2 mol of o-cyanobenzaldehyde to yield compound 36. A strong brightening effect with a reddish cast is obtained on polyester fibers and is mainly used in the textile industry. 

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