Patent ID: 7765774

Claim:
A method for treating a package, the method comprising the steps of: providing a product of a powder form, the product including a plurality of particles, wherein a major fraction of the particles have sizes between lower and upper size limits and a minor fraction of the particles have sizes below the lower size limit, the minor fraction of the particles comprising 1 mass percent of the particles; providing a first plastic film sack having a flexible wall comprising a plastic film, the wall having an outer surface and a roughened surface part comprising antislip protrusions fixed to at least a part of the outer surface of the first plastic film sack, at least some of the antislip protrusions each having at least one undercut and including a projection to the outer surface that is bigger than its intersection with the outer surface, and at least some of the antislip protrusions with the at least one undercut including at least one area immediately above the undercut, the at least some of the antislip protrusions with the at least one undercut being so dimensioned as to form a separation between the at least one area and the outer surface which is greater in size than the lower size limit; packing the product of the powder form in the first plastic film sack; and at least partly placing the first plastic film sack upon a second plastic film sack.