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A biaxially oriented oxygen and moisture barrier film and a method of producing such a film which comprises co-extruding at least one polyolefin polyolefin layer, at least one layer of an ethylene vinyl alcohol copolymer with a melt flow rate of at least about 8 grams per 10 minutes, and an adhesive

A biaxially oriented oxygen and moisture barrier film and a method of producing such a film which comprises co-extruding at least one polyolefin polyolefin layer, at least one layer of an ethylene vinyl alcohol copolymer with a melt flow rate of at least about 8 grams per 10 minutes, and an adhesive layer wherein the layers are combined into a composite sheet with the adhesive interposed between the polyolefin layer and ethylene vinyl alcohol copolymer layers. Next, the composite sheet is immediately cooled so that the crystallinity of the ethylene vinyl alcohol copolymer is no more than about 25 percent. Finally, the composite sheet is biaxially oriented in the longitudinal direction to a degree of about 2:1 to about 4:1 and in the transverse direction to a degree of about 3:1 to about 7:1.

대표청구항 ▼

1. A method of producing a biaxially oriented oxygen and moisture barrier film which comprises: (a) co-extruding (1) at least one layer of a polyolefin material selected from the group consisting of polyethylene, polypropylene, and copolymers of ethylene with other olefins, (2) at least one la

1. A method of producing a biaxially oriented oxygen and moisture barrier film which comprises: (a) co-extruding (1) at least one layer of a polyolefin material selected from the group consisting of polyethylene, polypropylene, and copolymers of ethylene with other olefins, (2) at least one layer of an ethylene vinyl alcohol copolymer with a melt flow rate of at least about 8 grams per 10 minutes, and (3) at least one adhesive layer and combining these layers into a composite sheet wherein the adhesive is interposed between the polyolefin layer and the ethylene vinyl alcohol copolymer layers, (b) immediately cooling the composite sheet so that the crystallinity of the ethylene vinyl alcohol copolymer is no more than about 25 percent, and (c) biaxially orienting the composite sheet in the longitudinal direction to a degree of about 2:1 to about 4:1 and in the transverse direction to a degree of about 3:1 to about 7:1. 2. The method of claim 1 wherein the ratio of the thickness of the adhesive to the thickness of the polyolefin layer is about 1:8 to about 1:15. 3. The method of claim 1 wherein the coposite sheet is cooled in a cooling medium at a temperature of 30° to 40° C. in step (b). 4. The method of claim 1 wherein the longitudinal orientation is carried out at a temperature of from about 130° to about 140° C. and the transverse orientation is carried out at a temperature of from about 150° to 160° C. and the polyolefin layer is comprised of polypropylene. 5. The method of claim 1 wherein the longitudinal orientation is carried out a temperature of from about 125° to about 130° C. and the transverse orientation is carried out at a temperature of from about 130° to 135° C. and the polyolefin layer is comprised of a copolymer of propylene and ethylene. 6. The method of claim 1 wherein the polyolefin layer is selected from the group consisting of polypropylene and copolymers of propylene and ethylene. 7. The method of claim 1 wherein a five layer film is produced comprising two outer polyolefin layers, an inner ethylene vinyl alcohol copolymer layer, and two adhesive layers disposed between the polyolefin layers and the ethylene vinyl alcohol copolymer layer. 8. A biaxially oriented oxygen and moisture barrier film formed by: (a) co-extruding (1) at least one layer of a polyolefin material selected from the group consisting of polyethylene, polypropylene, and copolymers of ethylene with other olefins, (2) at least one layer of an ethylene vinyl alcohol copolymer with a melt flow rate of at least about 8 grams per 10 minutes, and (3) an adhesive layer and combining these layers into a composite sheet wherein the adhesive is interposed between the polyolefin layer and the ethylene vinyl alcohol copolymer layers, (b) immediately cooling the composite sheet so that the crystallinity of the ethylene vinyl alcohol copolymer is no more than about 25 percent, and (c) biaxially orienting the composite sheet in the longitudinal direction to a degree of about 2:1 to about 4:1 and in the transverse direction to a degree of about 3:1 to about 7:1. 9. The film of claim 8 wherein the ratio of the thickness of the adhesive to the thickness of the polyolefin layer is about 1:8 to about 1:15. 10. The film of claim 8 wherein there are five layers which are comprised of two outer polyolefin layers, an inner ethylene vinyl alcohol copolymer layer, and two adhesive layers disposed between the polyolefin layers and the ethylene vinyl alcohol copolymer layer. 11. The film of claim 8 wherein the polyolefin layer is selected from the group consisting of polypropylene and copolymers of propylene and ethylene. 12. The film of claim 8 wherein the composite sheet is cooled in a cooling medium at a temperature of 30° to 40° C. in step (b). 13. The film of claim 8 wherein the longitudinal orientation is carried out at a temperature of from about 130° to about 14° C. and the transverse orientation is carried out at at temperature of from about 150° to 160° C. when polypropylene is the core layer. 14. The film of claim 8 wherein the longitudinal orientation is carred out at a temperature of from about 125° to about 130° C. and the transverse orientation is carried out at a temperature of from about 130° to about 135° C. when the core layer is a copolymer of propylene and ethylene.