| abstract |
Novel optical brighteners for organic materials are 1,4-bisstyrylbenzene derivatives of the formula <IMAGE> where R and R1, which are identical or different, are each hydrogen, halogen, lower alkyl or lower alkoxy, A and A1, which are identical or different, are each optionally halogenhydroxyl- or lower alkyl-substituted lower alkylene, and X and X1, which are identical or different, are each a -COOM or -SO3M group, where M is hydrogen, an alkali metal or an alkali earth metal or the cation of an organic ammonium or guanidinium base, and are prepared by reacting a 1,4-xylylenephosphonic ester derivative of the formula <IMAGE> where R2 is lower alkyl or a phenyl group, with a benzaldehyde derivative of the formula <IMAGE> The optical brighteners of the formula I have excellent heat resistance, even in an alkaline medium. |