extruder such that the adhesion of pet to the cellulosic substrate can be greatly increased this is accomplished by improvement of the chemical bond between the polymer film and substrate primer application_number US 83515201 A description with reference first to the figure there is illustrated an advantageous environment for use of the concepts of this invention in particular extrusion coater 2 is illustrated coater 2 includes in part unwind roll 4 primer coating unit 6 primer drying section 8 conventional extruder 10 and rewind roll 12 paperboard unwound roll 4 is produced from a cellulosic substrate such as a 0 018 inch thick bleached sulfate sheet definitely the term paperboard describes paper within a thickness range of 0 012 0 024 inches the invention is relative to the full scope of such a range as applied to packaging and beyond in use for food carton stock paperboard is usually clay coated on at least one side surface and frequently on both sides the paperboard trade characterizes a paperboard web or sheet that has been clay coated on one side as c1s and as c2s for a sheet coated on both sides compositionally this paperboard coating is a fluidized blend of minerals such as coating clay calcium carbonate and or titanium dioxide with starch which is smoothly applied to the traveling web surface successive densification and polishing by calendering finishes the mineral coated.