Convective-conductive Drying of a Thin Shrinkable Fibrous Layer Wetted with Latex as a Binder

Abstract

Convective-conductive drying was examined in a thin dewaxed cotton layer wetted with latex and set on a polymer film base. Heated air was supplied over both the layer top and film bottom, and drying rates were measured for two modes of air supply: high-temperature, high-velocity air to the top and low-temperature, low-velocity air to the bottom (TL supply) and the reverse mode (LT supply). The wetted cotton layer shrinks on drying and may be a model system of coated layer in which small particles are dispersed. The drying rate was found to decrease with decrease in the initial water concentration of latex. For a high initial water concentration of latex, as in the case of water, the overall drying time was shorter with TL supply, which gave a high drying rate during the initial drying period; and for a low initial water concentration, the overall drying time was shorter with LT supply. The thickness of the dried layer was independent of the initial water concentration of latex. The above results were consistent with those obtained previously with aqueous polyvinyl alcohol solution. However, compared with polyvinyl alcohol solution, the drying rate of latex was higher, the intersection on the initial water concentration of the overall drying time corves obtained from the two air supply modes was lower, and the mechanical strength of the dried layer was lower.