Size-controlled production of quinacridone nanocrystals using hot compressed water recrystallization method

Continuous production of quinacridone nanocrystals via a hot compressed water (HCW) recrystallization method was studied using a flow-through experimental apparatus at 24 MPa at temperatures from 523 K to 573 K. Quinacridone crystals were dissolved in HCW and precipitation was initiated by mixing with room temperature water (RTW), which gave the nanocrystalline product. Polyoxyethylene lauryl ether and sodium dodecyl sulfate were found to be useful for reducing aggregation of the nanocrystals. The effects of temperature and flow rate on the size of the crystals were examined; increasing the degree of supersaturation caused crystals to decrease in size. Nanocrystals that had an average diameter of ca. 36 nm could be obtained at 573.8 K and 24 MPa at a flow rate of 10 g/min for HCW and 100 g/min for RTW.