Plastic bag with venting perforations, closed plastic bag with venting perforations containing filler material and a plastic foil for forming such a bag

摘要

A plastic bag of polyolefin material such as polyethylene, for packaging materials, comprising particles of less than 50 mu m, and a closed bag containing such materials and a foil material for such a bag. The foil wall of the bag is provided with venting apertures with smooth edges, obtained by laser radiation, having a maximum size of 50-100 mu m; the distance between the venting perforations is such that the tensile strength of the foil is substantially the same as the tensile strength of the similar non-perforated foil. In a low density polyethylene foil of a thickness of 130-190 mu m distance between the perforations of 80 mu m is more than 20 mm, in a linear low density polyethylene foil of about 50-110 mu m the perforation distance is at least 5 mm. The bag may consist of two perforated foil layers, the perforations being staggered with respect to each other.