METHOD OF PREPARING MICROCAPSULES WITH ORGANIC PHOTOCHROMIC COMPOUND FOR PRINTING INK Russian patent published in 1999 - IPC

FIELD: microcapsulation technology. SUBSTANCE: photochromic compound is dissolved in solution of polymer in organic solvent, resulting solution is emulsified in medium based on melamine-formaldehyde resin, solvent is evaporated at 20-25 C and residual pressure 40-50 kPa; and microcapsules are isolated from dispersion medium. According to invention, photochromic compound (0.8-1.0 wt parts) is dissolved in 8-10% solution of acrylic polymer (8.0-10.0 wt parts) in methylene dichloride (80.0-82.0) and hexane (8.0-10.0 wt parts); emulsion medium is 2.3-2.5% hydrogel of melamine-formaldehyde resin with pH 7.0-7.3; solution-to-emulsion medium weight ratio is 1:4. Microcapsules are compatible with various film-forming substances, which enables their utilization in ink manufacture. EFFECT: achieved quality allowing protection of securities against forgery.