Process for preparing a ball-point pen ink

Claim 1

Improved process for preparing a stable liquid dye solution which is of low inorganic salt content and which is directly useful as a ball-point pen ink, said process comprising admixing and reacting at 20°-80° C. approximately stoichiometric amounts of a water-soluble cationic dye and a water-soluble anionic dye in a liquid medium, which comprises a solvent for said water-soluble ionic dyes, to form a cationic-anionic dye salt which is substantially insoluble in water; without isolating the dye salt, dissolving said salt in the lower phase of a two-phase liquid medium comprising an upper aqueous phase and a lower ball-point pen ink solvent phase, said ball-point pen ink solvent being substantially insoluble in water, the two-phase liquid medium either being present during said admixing and reacting or being added subsequent to said admixing and reacting; and thereafter separating the aqueous and solvent phases which provides a stable liquid dye solution which is useful as a ball-point pen ink.