Organic dyes containing silane groups and process for preparing same

Composite pigments, consisting of s-triazinyl-bis-anthraquinone dyes, containing silane groups grafted on a support selected from the group consisting of TiO.sub.2 gel, semicrystalline, rutile, anatas TiO.sub.2, associated with Al.sub.2 O.sub.3, SiO.sub.2, aluminum silicates, mica, talc and/or mixtures thereof having a value of the specific surface ranging between 5 and 500 m.sup.2 /g, said dyes having the formula:

• ##STR10## wherein R.sub.1 and R.sub.2, equal to each other or different from each other, are selected from the group consisting of a hydrogen atom, a primary amine group (NH.sub.2), a secondary amine group of the --NH--R type, wherein R is an alkyl group containing from 1 to 4 carbon atoms or a phenyl group, an --NH--CO--CH.sub.3 acetylamino group, an ##STR11## benzoylamino group, an --NO.sub.2 nitro group, a halogen preferably bromine or chlorine, a hydroxyl radical, a phenol group and a thiophenol group;
• n is a whole number comprised between 3 and 5
• W indicates an alkyl group containing from 1 to 4 carbon atoms or a phenyl group;
• Y indicates an alkoxy group containing from 1 to 4 carbon atoms
• q is a whole number selected from 0-1
• x and m are whole numbers such that, when q=0, x=3 and m=0, 1, 2, 3 and when q=1, x=2 and m=0, 1, 2.