Process for making a metal-polymer composite having an irradiated polymer coating

Abstract

A process for making a metal-polymer composites suitable for shaping into container end panels having improved resistance to feathering and angel hair formation. A polymer coating is applied to a metal sheet. The polymer coating includes at least one polymer selected from polyolefins, anhydride modified polyolefins, epoxies, and phenoxies. The polymer coating on the composite is then irradiated with an electron beam. The metal sheet preferably comprises an aluminum alloy and the polymer coating preferably comprises maleic anhydride modified polyropylene.

What is claimed is:  
     
         1 . A process for making a metal-polymer composite suitable for shaping into food and beverage container bodies and container end panels, comprising 
 a. applying to a metal sheet a polymer coating comprising a polymer selected from the group consisting of polyolefins, anhydride modified polyolefins, epoxies, and phenoxies, thereby to form a metal-polymer composite including a polymer coating, and    b. irradiating the polymer coating on said composite with an electron beam, thereby to improve resistance of said coating to feathering and angel hair formation.    
     
     
         2 . The process of  claim 1  wherein said metal sheet comprises a metal selected from the group consisting of aluminum alloys, steel, aluminum alloy-coated steel, and aluminum-coated steel.  
     
     
         3 . The process of  claim 1  wherein said metal sheet comprises an aluminum alloy of the AA3000 or AA5000 series.  
     
     
         4 . The process of  claim 1  wherein said polymer comprises a polyolefin selected from the group consisting of polypropylene, polyethylene, propylene-ethylene copolymers, propylene-1-hexene copolymers, and mixtures thereof.  
     
     
         5 . The process of  claim 1  wherein said polymer comprises a polyolefin selected from the group consisting of polypropylene and copolymers comprising propylene and up to about 50 mole percent of a co-monomer.  
     
     
         6 . The process of  claim 1  wherein said polymer comprises a polyolefin modified with an anhydride selected from the group consisting of maleic anhydride, citraconic anhydride, itaconic anhydride, glutaconic anhydride, 2,3-dimethylmaleic anhydride, and mixtures theeof.  
     
     
         7 . The process of  claim 1  wherein said polymer comprises a polyolefin modified with about 0.5-20 weight percent maleic anhydride, based on the weight of the polyolefin.  
     
     
         8 . The process of  claim 1  wherein the step of applying the polymer coating to the metal sheet comprises extrusion coating, roll coating, or laminating.  
     
     
         9 . The process of  claim 1  wherein the step of irradiating comprises irradiating at a dosage of about 2-20 megarads.  
     
     
         10 . The process of  claim 1  further comprising 
 c. shaping said composite into a container body or container end panel.  
 
     
     
         11 . The process of  claim 10  wherein step b. is performed before step c.  
     
     
         12 . The process of  claim 10  wherein step b. is peformed after step c.  
     
     
         13 . The process of  claim 1  further comprising 
 d. before step a., conversion coating a surface portion of said metal sheet.  
 
     
     
         14 . A process for making an aluminum-polymer composite suitable for shaping into container end panels having improved resistance to feathering and angel hair formation, comprising 
 a. applying to an aluminum alloy sheet a polymer coating comprising a maleic anhydride modified polyolefin, said polyolefin being selected from the group consisting of polypropylene and copolymers comprising propylene and up to about 50 mole percent of a co-monomer, thereby to form an aluminum-polymer composite, and    b. irradiating the polymer coating on said composite with an electron beam.    
     
     
         15 . An aluminum-polymer composite made by the process of  claim 14 .  
     
     
         16 . A container end panel shaped from the composite of  claim 15 .  
     
     
         17 . An aluminum-polymer composite comprising 
 a. an aluminum alloy sheet having a thickness of about 7-14 mils, and    b. a polymer coating adhered to said sheet, said polymer coating having a thickness of less than about 1 mil, said polymer coating comprising an anhydride modified polyolefin, said polyolefin being selected from the group consisting of polypropylene, polethylene, and copolymers comprising propylene and up to about 50 mole perecent of a co-monomer, said polymer coating being irradiated with an electron beam.    
     
     
         18 . A container end panel shaped from the composite of  claim 17.