Importance

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Abstract

Flat-rolled steel strip, free of surface iron oxide, is provided with a corrosion-protection metallic coating on both surfaces, followed by continuous-line polymeric coating operations in which a single surface is pre-treated so as to activate that surface for adhesion of molten extruded thin-film polymeric material for in-line travel. Polymeric materials are formulated to provide maleic-anhydride modified polypropylene, which is melted and pressurized for extrusion as a molten thin-film tie-layer for first contacting that activated surface; and, thin-film intermediate and finish layers are each formulated to contain a selected percentage of polybutylene; which are extruded as molten films in overlaying relationship to said first contacting tie-layer. Polymeric finish-processing re-melts the polymeric materials; and, following a selected interval of in-line travel in that re-melted condition, rapidly cools those polymeric materials through glass-transition temperature so as to establish amorphous characteristics throughout said materials. End-usage product comprise flat-rolled mild steel can stock for fabricating one-piece drawn, and drawn and ironed, can bodies with interior polymeric coating and an exterior corrosive-protection metal coating, such as matte-finish electrolytic tin plate.

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First Claim