Method of preparing a composite structure

Claim 1

A method according to claim 1 where the flexible sheet and strip comprises rubbery material individually selected from the group consisting of natural rubber, rubbery 1,4 addition polymers of 1,3-butadiene, rubbery 1,4 addition polymers of isoprene, rubbery copolymers of butadiene and styrene, rubbery copolymers of butadiene and acrylonitrile, butyl rubber, rubbery copolymers of ethylene and propylene, terpolymers of ethylene, propylene and a minor proportion of a nonconjugated diene, and polymers formed by the open ring polymerization of unsaturated alicyclic compounds having from one through three carbon-to-carbon double bonds in the alicyclic ring.

Claim 3

A method of preparing a pinched seam container suitable for containing liquid hydrocarbons comprised of shaped cured polymeric flexible sheets with flexible hydrocarbon barrier layers adhered together through a cured flexible strip around their periphery which comprises a. releasably attaching first and second curabLe polymeric flexible sheets over the apertures of first and second concave molds, correspondingly, the dimensions of the mold apertures being substantially the same, to form enclosed cavities between the curable polymeric flexible sheets and respective molds, wherein the said polymeric flexible sheets each comprise a curable rubber adhered to a layer of a flexible polymeric hydrocarbon barrier material with the said layer of hydrocarbon barrier material of the sheets facing outwardly from their said respective concave molds, where the said barrier layers have a thickness of from about 0.25 to about 10 mils and are selected from at least one of the group consisting of nylon, polyvinylidene chloride, copolymers of vinylidene chloride, vinyl chloride and acrylonitrile, and linear polyesters of the structure derived from straight chain glycols having from two to ten carbon atoms and at least one dicarboxylic acid selected from terephthalic acid and isophthalic acid, b. applying reduced fluid pressure to one of the said cavities to actuate and shape the first of the said flexible sheets against its respective concave mold, c. providing at least one vent to outside air through the wall of said shaped flexible sheet extending through the corresponding mold wall, d. adhesively adhering the first and second flexible sheets through a strip of curable rubber interposed between the said sheets at about their peripheries and adhered with adhesive to the said layers of hydrocarbon barrier material to define an enclosed cavity therebetween vented with the said vent, and to provide a pinched seam around the periphery of the sheets, e. shaping any of the said flexible sheets remaining unshaped against its respective concave mold by applying reduced fluid pressure to its corresponding enclosed cavity, f. curing, in this position while maintaining said reduced pressure, the said curable polymeric material of the said flexible sheets and the said strip of curable polymeric material to form a composite structure, said vent being operable to maintain a pressure differential across said shaped sheets while curing, and g. removing the said composite structure from the first and second molds.