Carbon Dioxide → Butyl prop-2-enoate;styrene

Beteiligte Stoffe

Reaktionsschritte

A process of microencapsulation using a CO2/water emulsification is described hereinbelow. About 4 wt % of a dye such as, for example, Acid Red 94, is incorporated into about 75 wt % of a latex, such as, for example, a styrenelbutylacrylate formed by either emulsion or dispersion polymerization. First, styrene/butyl acrylate monomers are polymerized via emulsion polymerization to form about 100 nm to about 200 nm particles. These particles are then placed on a freeze drier for about 48 hours. The latex particles are dispersed in de-ionized (DI) water using an ultrasonic bath. This solution is then transferred to a variable volume cell where the desired dye and about 1 wt % of a surfactant, such as, for example, polyethylene oxide/polypropylene oxide block copolymer (PLURONIC F108), are added to the latex dispersion. The cell is sealed and about 350 grams of supercritical CO2 is added. Once the supercritical CO2 is added, the cell is pressurized and a magnetic stirrer is used to emulsify the supercritical CO2 and water. The mixture is allowed to stir for approximately 10 hours. After the dye is incorporated into the latex, i.e. after about 12 hours, the CO2 is vented off slowly to minimize foaming. To remove any excess unreacted dye, the latex dye mixture is washed with absolute ethanol until the wash solution is colorless. These dyed latex particles are then re-dispersed in DI water and added to a reactor, such as a 4 liter glass bottom reactor, commercially available from Chemglass Life Sciences. Additionally, a wax may be added to the latex dye mixture. The mixture is then homogenized at high shear with a coagulating agent, such as for example, a polyaluminum chloride for about 20 minutes. The mixture is then aggregated for a predetermined time period until the particle size is sufficient for latex shell addition (such as from about 3.0 to about 7.0 μm).

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