Drying of Coated Slurry in Vapor of Drying Solvent

Abstract

Various thin films are produced by coating and drying of slurries. Cracks and fractures in the film, which frequently are encountered under a large drying rate condition, can be avoided by a reduction in drying rate. In this work, we propose a novel drying technique (pressure controlled drying), where the coated slurry is dried in a container filled with vapor of the drying solvent. If the inner pressure of the container is held reasonably higher than the saturation vapor pressure of the solvent, the drying rate can be successfully depressed. It was also turned out that the residual amount of the solvent in the coated slurry before and after holding the pressure has to be carefully controlled in order to work this drying technique effectively. The residual solvent is affected mainly not only by the time of holding the pressure but also by the container volume, decompressing capacity, and co-drying solvent. When the drying rate could be suppressed till the end of the constant drying rate period, the resultant film had a tightly packed cellular pattern and a smooth surface. This is probably due to the enhancement of particle arrangement with sufficient amount of the solvent and long drying time.