Internally pressurized package with heat-sealable closure member

A pressure-tight packaging made of tubular flexible plastic material having sealed ends, with an initially heated gas contained therein and means to enable pressurizing and maintaining a gas pressure in said pressure-tight packaging without disturbing said sealed ends, said means comprising an opening in one packaging wall remote from the sealed ends of said pressure-tight packaging and a means for sealing said opening, said means comprising an elongated closure member for said opening said closure member comprising an imperforate material which is heat sealable at the temperature of the initially heated gas used to pressurize said container, said closure member being of planar configuration and being first attached by its opposed ends to the inner surface of said wall adjacent said opening to overlie said opening but defining a passage between said closure member and the wall immediately adjacent to the opening so as to permit gas entering said opening to enter said closed container, the positioning of the closure member in relation to the inner surface of the wall being such that when said container is internally pressurized with the gas at a temperature sufficient to activate said heat-sealable material and a pressure sufficient to urge said closure member against said opening, a permanent seal is formed.