METHODS OF MAKING METAL CAN ENDS WITH PLASTICS CLOSURES

摘要

METHODS OF MAKING METAL CAN ENDS WITH PLASTICS CLOSURES A method of making a metal can end with a tear-open plastics closure, for a can intended to be resistant to leakage when subject to internal pressures, such as arise from carbonation of a beverage or thermal processing, wherein the undersurface of the can end is provided with a plastics coating, and the can end is pierced to form an aperture with a peripheral downturned flange at an angle of 80.degree. to 120.degree. to the plane of the can end and having a flat end. A one-piece ring pull closure is injection moulded on to the can end from a plastics material resistant to softening at up to at least 65.degree.C, without additional heating of the metal, so as to fill the aperture, bond with the coating, and enclose the flange, with a residual thickness below the flange of 0.08 to 0.5 mm. The thickness of the plastics material of the closure is such that it can be sheared against the flange when the ring pull is pulled manually. The residual thickness of the plastics material may be varied around the aperture to increase resistance of the closure to creep, and the aperture may be pear-shaped or may be circular with a separate vent hole.