Keyes Fibre Company

Clifford Stowers

Peter D Foster

A deliddable ovenable container, such as a molded pulp tray with a liner obtained from a thin film of polyester, useful for packaging food to be frozen for sale and storage and subsequently heated by the consumer in either a microwave or a conventional oven, with means to insure that a transparent and flexible lid of polyester film sealed thereto by heat and pressure subsequently can be peeled away from the polyester liner of the tray without any undesirable delamination of the liner from the molded pulp base of the tray, either at freezing temperatures before heating or at high temperatures after heating, to expose the food for consumption. Such means includes a coating of release material having adhesive properties, such as methyl cellulose, on the liner outside the area where the lid is to be sealed to prevent strong adherence between the lid and the liner at the extreme edges of the tray, the release material ideally having fiber adhesive properties as well and being applied to the cut edge which strengthens the mechanically trimmed fibrous material around the edge of the molded pulp base, plus increased density of the fibrous material only around the zone of the release material and the lid seal so that the fibrous material additionally resists being pulled apart in that area while still providing a thicker thus stronger tray elsewhere which resists bending forces.

Deliddable ovenable container

An inexpensive, disposable, three-dimensionally contoured container, suitable for many purposes including holding food during exposure to high temperatures for long times in either a microwave or a conventional oven without any detrimental effect to the container or the food. The container consists of an essentially impervious liner of polyethylene terephthalate directly bonded by its own substance to a pre-formed contoured base obtained by molding to final shape nonbrowning substantially 100% bleached kraft wood pulp from an aqueous slurry thereof against an open-face suction mold, and drying the same under pressure imposed by a mating pair of heated dies. The liner is formed by bonding to the pulp base a 0.5-2.0 mil thick film of thermoformable, substantially amorphous, substantially unoriented polyethylene terephthalate having a molecular weight which is understood to be in excess of 15,000. The film is bonded to the base by pre-heating the base, rapidly pre-heating the film and then quickly pressing the film into contact with the base at a temperature in the range of 300.degree.-375.degree. F., the pressing being done by vacuum in the range of about 20 inches of mercury applied through the base for no longer than about 1 second, and finally cooling so that the liner thereafter will not shrink-separate away from the contoured base as a result of subsequently exposing the container to a temperature of up to 400.degree. F.

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Fairfield, ME, United States of America

Clifford Stowers