| 摘要 |
A process is disclosed for cutting or perforating a plastic film sheet material with a knife of improved durability which comprises a metal substrate coated on one side only with a hard material such as tungsten carbide. A preferred embodiment comprises a process for making a continuous strip of interconnected and separable plastic film bags of low pressure - low density polyethylene from a tube of same including the steps of sealing the tube across its width at longitudinally-spaced intervals and perforating the tube at similar intervals, to provide tear-off lines, with a perforating blade provided with a coating on one side only of a hard material such as tungsten carbide. Such a perforating blade has a significantly improved service life, as compared to uncoated similar blades or similar blades coated on both sides, in processes for making bags from low pressure-low density polyethylene. |
