Membrane closure structure

A membrane closure for a container, said membrane closure being heat sealable to said container, said membrane closure being capable of removal from said container by peeling under hand pressure and said membrane closure being capable of withstanding retort sterlization, said membrane closure comprising a first adhesive layer, an intermediate metallic foil or paper layer having one side thereof bonded to said first adhesive layer, a second adhesive layer having one side thereof bonded to the other side of said intermediate layer and a barrier metallic foil or paper layer having one side thereof bonded to the other side of said second adhesive layer, said intermediate layer having a tear strength less than the bond strengths of said first adhesive layer and said second adhesive layer, said second adhesive layer having a bond strength less than the bond strength of said first adhesive layer and said barrier layer having a tear strength greater than the tear strength of said intermediate layer and greater than the bond strengths of said first adhesive layer and said second adhesive layer, whereby upon peeling of said membrane closure from said container initial failure occurs within said intermediate layer and secondary failure occurs between said second adhesive layer and said intermediate layer, along a heat seal between said membrane closure and said container.