Abstract: A container closure formed from a thermoplastic polyolefin, e.g. polypropylene, which has been molded and adheres simultaneously to a coated foil, e.g. an aluminum insert, to which a conventional plastisol gasketing compound may be adhered to provide a hermetic container seal under hot fill and retort conditions. In order to facilitate adhesion to both the polypropylene closure panel and the PVC plastisol gasketing compound, a dead soft aluminum foil web was first coated on one side with an organosol utilizing a gravure coater, after which the coated web was passed through an oven. The partially coated web was then coated with a primer dispersion again utilizing a gravure coater, after which the coated web was passed through a second oven. A layer of polypropylene homopolymer was applied to the primer and inserts were die cut from the resultant web. The inserts were incorporated in a closure injection molding apparatus and a plastic closure injection molded thereabout.

Abstract: Gaskets are formed in container closures fabricated from polyolefin resins exhibiting substantially no response to heat activation by radio frequency electrical energy by introducing a vinyl chloride plastisol containing a vinyl chloride polymer resin and a plasticizer having a loss factor in the range of 0.1-12 into the closure. The closure is preheated to 55.degree. to 100.degree. C. by conventional means and then the plastisol is fused in the closure by exposure to a field of radio frequency electrical energy.