seen framstella a film whose one side by thermal forsegling against sjelv or against another plastforemal form a cold condition iserdragbar proof closure

摘要

1326859 Peelable seals for packages TOWER PRODUCTS Inc 26 May 1972 [27 May 1971] 24838/72 Heading B8C [Also in Division B5] A process for forming a peelable seal between plastics articles comprises selectively treating one surface of a film containing a proportion of polyethylene with heat at a temperature of from 515‹ F. to 575‹ F. while subjecting said surface to an oxidizing atmosphere containing at least 19% oxygen, cooling the film and then thermally bonding the treated film to the surface of another article containing a major portion of polyethylene. As shown in Fig. 1 a blowextrusion apparatus comprises a hot-melt feed unit 10 for introducing molten polyethylene mixture 12 into the orifice of an annular die 14 which is maintained at a temperature between 515‹ and 575‹ F. and wherefrom a cylinder of material issues upwardly through a ring-shaped lip 16 in the die 14. Simultaneously a gaseous inflating medium, containing at least 19% oxygen, for instance air (19 to 22% by volume oxygen) is introduced through a line 18 and into a funnel-shaped outlet 20 disposed centrally within the ring-shaped lip 16 to inflate the hot melt into an elongated cylindrical form. A higher, or lower, temperature of the ambient atmosphere is effective to require a correspondingly smaller, or greater, increment of die temperature. The oxidized inner surface of the film forms peelable seals when bonded in conventional heat-sealing equipment at a temperature between 250-400‹ F. and preferably at 370‹ F. for a duration of two seconds to another sheet containing a proportion of polyethylene such as polyethylene-ethylene vinyl acetate copolymers. Figs. 2, 3 show a pair of opposed plies 30, 32 according to the present invention and with at least one of their facing surfaces oxidized, the plies being sealed along lines 34, 36, 40. Figs. 4, 5 show a container wherein the oxidized surface of a film 50 is heat-bonded to an upper flange 52 of a filled container 54.