Continuous Production of Quinacridone Nanocrystals and Control of Crystal Form by High-Temperature Water Crystallization Method

A high-temperature water (HTW) crystallization method was applied to produce size- and form-controlled organic nanocrystals without the use of any organic solvents. HTW and room-temperature water (RTW) were used as the extraction and cooling solvents, respectively. Nanocrystals are precipitated by mixing a high-temperature quinacridone aqueous solution in a newly developed micromixing unit with RTW from another line. Quinacridone nanocrystals having an average diameter of ca. 9 nm as determined from transmission electron microscopy observations and ca. 83 nm from dynamic light scattering measurements were produced at 250.6?C and 24 MPa with a flow rate of 10 g/min for HTW and 20 g/min for RTW. In addition, it was found that nanocrystals having different crystal sizes and forms could be obtained by changing the temperature and flow rate of RTW. This new method promises an environmentally sustainable process for the continuous production of organic nanocrystals.