Coumarin derivatives, their preparation and their use as optical

Abstract

Coumarin of the formula: ##SPC1## In which R.sub.1 represents an alkyl group having 1 to 5 carbon atoms, and either unsubstituted or substituted by a non-ionic and non-chromophoric group, R.sub.2 represents a benzene, styryl or heterocyclic residue such residue being unsubstituted or substituted by one or two non-ionic and non-chromophoric groups; process for the preparation of a coumarin of the above formula which comprises reacting an orthohydroxy-benzaldehyde of formula (II) upon an acid of formula (III) or one of its functional derivatives: ##SPC2## Wherein R.sub.1 and R.sub.2 have the same definitions as in claim 1; process for the fluorescent brightening of fibrous material of synthetic origin which comprises treating the material with a coumarin of the above formula; fluorescent brightening composition containing a coumarin of the above formula and a dispersing agent resulting from the condensation of naphthalene-sulphonic acids with formaldehyde in the presence of or absence of phenol compounds, said dispersing agent comprising 30% to 50% monosulphonated condensates, 30% to 50% disulphonated condensates and 10% to 40% trisulphonated or higher polysulphonated condensates; fibres of synthetic origin treated with a coumarin of the above formula or with a brightening composition as set out above.