IL41478A

IL41478A - Container wall structure with integral opening device and its manufacture

Info

Publication number: IL41478A
Application number: IL41478A
Authority: IL
Original assignee: Aluminum Co Of America
Priority date: 1973-02-06
Filing date: 1973-02-06
Publication date: 1976-05-31
Also published as: IL41478A0

Claims

41 78/2 What we claim is:

1. A method of fabricating a container wall adapted to be provided with an integral opening device, which comprises providing a metal sheet having an adhesive material secured to one surface thereof serving to secure to said metal sheet a continuous protective layer of a partially crystalline poly-olefin, a partially crystalline copolymer of polyolefin and ethylene, a polyethylene acrylate ionomer or an ionomer, scoring said metal sheet to define a removable sector therein while preventing fracture of said adhesively secured protective material, and subsequently heating said composite sheet to a temperature of 275 to 375°F. for a period of 0.2 second to 4 minutes to stress relieve the protective layer and substantially completely eliminate microvoids established in said protective, layer during said scoring operation.

2. A method according to claim 1, wherein said adhesive material comprises an epoxy resin, polyester or polyurethane , an upwardly directed hollow integral rivet being formed in said composite metal sheet withih said score line defined removable sector while preventing fracture of said protective layer, and wherein the heating is effected to a temperature of about 300 to 350°F. for about 0.5 to 3 minutes.

3. A method according to claim 2, wherein said protective layer is provided as a film having a crystallinity of about 50 to 60%, said protective Ifilm being stress relieved by said heating to substantially reduce the number of said microyoids established in said protective film during said scoring and rivet forming operations while resisting any substantial permanent change in crystallinity of said protective layer. 41478/2

4. A method according to claim 2 or 3, wherein said protective layer comprises polypropylene or a copolymer of polypropylene and ethylene with an ethylene content of from 2 to 10% by weight.

5. A method according to any one of claims 2 to 4, wherein subsequent to scoring said composite metal sheet, said composite sheet is reformed to establish a can end structure, a pull tab member being placed over said integral rivet and staking said rivet to secure said pull tab to said composite metal sheet.

6. A container wall structure made by the method according to claim 1, which comprises a metal sheet having a score line defined removable sector, an adhesive layer secured to one surface of said metal sheet, said adhesive being an epoxy resin, polyester or polyurethane, and a stress relieved thermally treated continuous protective layer secured to said metal sheet undersurface by means of said adhesive layer, said continuous protective layer being a partially crystalline polyolefin, partially crystalline copolymer of polyolefin and ethylene, a copolymer of ethylene and acrylate or an ionomer, said protective layer having a crystallinity in excess of 50%, and said adhesive bond between said protective layer and said metal sheet removable sector being of greater strength than the strength of said protective layer in regions underlying said score line*.

7. A container wall structure according to claim 6, wherein said protective layer has a thickness of 2.5 to 3.5 mils in regions not underlying said score line, and said protective film being polypropylene or a copolymer of polypropylene and ethylene having an ethy lene content of 2 to 10% by weight.

8. A container wall structure according to claim 6 or 7, wherein said protective layer is substantially free of microvoids, and said protective layer has been stress relieved by effecting the thermal treatment at 275 to 375°F. for 0.2 second to 4 minutes and - 41 478/2

9. A container wall structure according to any one of claims 6 to 8, wherein said protective layer has stress relieved properties resulting from thermal treatment at 300 to 350°F. for 0.5 to 3 minutes, said bond between said protective layer and said metal sheet being substantially continuous, and said protective film being a polypropylene-ethylene copolymer having an ethylene constituent of about 2 to 5% by weight.

10. A method of fabricating a container wall having an integral opening device, substantially as hereinbefore described with reference to the accompanying drawings.

11. A container wall structure made by the method according to claim 1, substantially as hereinbefore described with reference to the accomapnying drawings . For the Applicants OR. REjNHOLD COHN AND PARTNERS