Patent ID: 7863459

Claim:
A process for preparing an onium salt of an anionic dye, which comprises mixing an aqueous solution of a salt of the dye with a solution of a water-insoluble salt of formula (I) in a water-immiscible organic solvent, and separating a solution of the onium salt of the anionic dye in the organic solvent from the residual aqueous solution, the water-insoluble salt of formula (I) being: X + (R) n Y âˆ’ (I) where: X represents a nitrogen, sulphur or phosphorus atom; R represents: a C 1 -C 50 alkyl group which is unsubstituted or is substituted by at least one cycloalkyl, aryl, acyloxy or heterocyclic group, or whose carbon chain is interrupted by at least one unsaturated carbon-carbon bond or by at least one cycloalkyl, aryl or heterocyclic group; an aryl group; or a heterocyclic group; and the groups R may be the same as or different from each other; or, when X represents a nitrogen atom, two or three groups R, together with the nitrogen atom to which they are attached may represent a nitrogen-containing heterocyclic group; or one or two of the groups R may represent a polymeric group; n represents the number of available valences of the atom X; or said group of formula (I) represents a repeating unit in a polymer; and Y âˆ’ represents an anion, wherein the onium salt is a quaternary ammonium, phosphonium, sulfonium or imidazolinium salt, and wherein the dye is an azo dye, a nitrophenol dye, a phthalein dye, a sulphonephthalein dye, a triphenylmethane dye, or an indophenol dye.