Through-air drying apparatus having decreasing wet flow resistance in the machine direction and process of drying a web therewith

摘要

A micropore drying apparatus (10) having a variable wet flow resistance. The flow resistance preferably decreases in the machine direction. The micropore drying apparatus (10) may comprise a single integral unit having a decreasing wet flow resistance from the beginning to the end of the unit. Alternatively, the micropore drying apparatus (10) may comprise a plurality of discrete units, each unit having a successively lesser flow resistance than that of the preceding unit. Alternatively, a hybrid arrangement may be used wherein each discrete unit has a successively decreasing flow resistance within that unit. The micropore drying apparatus may comprise one or more micropore drying media (15). The micropore drying media (15) have pores (40) which allow air flow therethrough. The pores (40) are disposed in a grid, to form a field of pores. The decreasing flow resistance may preferably be provided by adjusting one or more of said pores (40), which affect the flow resistance through a single pore or through the entire field of the pores.