PLASTIC CLOSING TOOL AND MANUFACTURE THEREOF

摘要

PURPOSE: To form a hermetic seal under a high temp. filling and retorting condition by forming one of outer layers by a plastic material thermally bondable to a closure and forming the other one of them by internally providing a multilayered plastic barrier insert formed from a plastic material to which a plastisol gasket is fused. CONSTITUTION: A barrier layer 12 composed of a vinylidene chloride/vinyl chloride copolymer is interposed between two layers 14, 16 composed of a propylene homopolymer or a propylene copolymer and a multilayered web 18 is formed by a simultaneous extrusion process using an extruder 20. Next, a multilayered plastic barrier insert 30 is formed from the multilayered web 18 by using a mold punching apparatus 28. Next, a high temp. polypropylene extrusion material is injected into a mold 32 by using an extrusion nozzle 42 to be molded. During this period, the barrier insert 30 remains at a constant position and the surface layer 14 exposed when a closure member 44 is formed is thermally bonded to the high temp. extrusion material at the same time. Finally, a plastisol gasket 52 is welded to the layer 16 by using a dielectric heater 54.