Abstract: A method of preparation of valves for a flat, flexible, sterilizable container capable of sterilely containing a liquid to be removed under absolutely sterile conditions which comprises the steps of:forming a two-layer laminate including a first layer of a copolymer of ethylene with a minor proportion of butylene and a second layer of an amide polymer; forming a pocket in the two-layer laminate wherein the first layer forms the inner surface of the pocket; providing an elastomeric core element having spaced major faces; inserting the core element into the pocket in the two-layer laminate; providing a three-layer laminate including a first outer layer of a major portion of a propylene polymer, a second outer layer of a copolymer of ethylene with a minor proportion of butylene, and an intermediate layer of an amide polymer; orienting the three-layer laminate so that the second outer layer thereof is apposed to the first layer of the two-layer laminate; expelling air surrounding the core element in the pocket; w

Abstract: A flat, flexible, sterilizable container for a liquid to be maintained and extracted under sterile conditions, said container comprising: a body having walls formed by a three-layer laminate including an outermost layer of a propylene polymer, an innermost layer of a copolymer of ethylene with a small amount of butylene, and an intermediate layer of an amide polymer; and a valve carried by said body comprising an elastomeric core whose spaced major faces are covered, one, by a three-layer laminate similar to said body wall forming laminate and, the other, by a two-layer laminate including a first layer of a copolymer of ethylene with little butylene and a second layer of an amide polymer.