A multilayer packaging medium or sack has a filler opening, an impermeable outer layer, a porous inner layer, and an overlap region or fold having a perforated film between the inner and outer layers, with an open passage over a portion of the length of the folded area communicating with the perforated portion. The packaging medium is especially useful for the packaging of pulverulent materials, in particular water sensitive or water soluble powders.

 
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