Patent ID: 7498054

Claim:
An automated method for producing dyed polymer microparticles comprising: (a) providing a microparticle master-batch suspension comprising microparticles characterized by a first dye concentration in the microparticles, said microparticles suspended in a dye solution comprising at least one dye and a solvent system comprising: (i) at least one first solvent in which the dye and the microparticle polymer are soluble; (ii) at least one second solvent in which the dye and the polymer are not or only weakly soluble, said first and second solvents being immiscible or at most partially miscible; (iii) at least one third solvent in which the dye and the polymer are not or only weakly soluble, said third solvent being miscible with the first and second solvents; (b) creating two or more microparticle suspension aliquots from said master-batch suspension, each such suspension aliquot characterized by microparticles of said first dye concentration suspended in said dye solution; (c) executing, at least once for each created aliquot, the following sequence of steps to transform the microparticle dye state in each aliquot from said first dye concentration to a selected second dye concentration in the microparticles: (i) computing, for the selected second dye concentration: (1) the amount of dye dissolved in said first solvent, and (2) the amount of second solvent, required to be added to said aliquot to attain said selected second microparticle dye concentration; and (ii) dispensing to said aliquot the amount of dye dissolved in said first solvent and the amount of second solvent required to attain said selected second microparticle dye concentration.