| 摘要 |
<p>A process for obtaining a solid or semi-solid material by drying a solution thereof which comprises expanding a spray of the solution, which has been supercooled, into a vacuum and collecting the frozen droplets of spray on a surface which is sufficiently cold to cause the frozen solvent to sublime from the frozen droplets at the vacuum pressure, thereby producing particles whose size can be controlled by choice of droplet size. Elevated temperatures or milling stages are not required, so the process is especially suitable for thermolabile materials. The process can be carried out using an apparatus comprising a vacuum chamber (11) having refrigerated walls, a vacuum pump (17) and a condenser (18). The solution is sprayed into the chamber via a nozzle (16) and the frozen droplets are collected on the walls of the chamber (11) and sublimation takes place therefrom.</p> |
