Reinforced thermoplastic film sheet

Claim 1

A bag capable of withstanding stresses over a period of at least about 4 months encountered in being stacked five pallets high with a height of five bags per pallet when each said bag contains 50 pounds of granular material, the walls of said bag being composed of a sandwich construction comprising: (a) inner and outer layers of a polyethylene film each said film having an elongation of at least about 200%; (b) a substantially flat plastic net-like structure intermediate said inner and outer walls, said structure; (i) having been formed by extruding a first set of space parallel longitudinal strands interconnected by a second set of spaced, parallel transverse strands extruded integral with said longitudinal strands, the first and second sets of strands meeting at substantially right angles; (ii) the extruded structure having been biaxially oriented by heating it and stretching it; (iii) weighing from about 1/2 pound per thousand square feet to about 3 pounds per thousand square feet; (iv) having an elongation of less than about 50%; (v) being of substantially uniform cross-section throughout both the strands and the joints thereof; (c) portions of said inner and outer layers being bonded to each other along selected strips by heat sealing, one of said selected strips being an end seam; (d) one said set of strands being aligned substantially parallel with said end seam and the other said set of strands being aligned substantially perpendicular thereto; (e) other portions of said inner and outer layers being unbonded to each other over a continuous area of a plurality of strands of each said set of strands; whereby said structure is free to move with respect to said inner and outer layers in the unbonded area.