20110082019 | Method of Manufacturing a Polypropylene Pinch Bag - A method of manufacturing a gusseted pinch bag from polypropylene. A sheet or seamless tube of polypropylene is provided. The sheet is preferably comprised of one or more layers of axially and/or biaxially oriented polypropylene. Perforation lines in a pinch pattern are formed in the sheet or tube. Preferably a laser forms a series of small, closely spaced holes in the sheet along the perforation line. The laser heats the plastic surrounding the holes, causing the polypropylene molecules between the holes to lose their orientation. Thus, the polypropylene in the perforation line between the holes is substantially weakened. If a sheet is used, it is folded into a gusseted tube and the edges are sealed together to make a tube. If a seamless tube is used, the tube is gusseted. In either case, a lateral force is then applied to the terminal tube, breaking the perforation line and separating the terminal tube from the sheet. The bottom end of the tube is then sealed, thereby forming a bag. | 04-07-2011 |