Thermoplastic film making

Claim 1

THE PROCESS OF PRODUCING THERMOPLASTIC FILM, COMPRISING THE STEPS OF SPREADING A PLASTISOL OF THE FILM-FORMING MATERIAL INTO THE FORM OF A THIN LAYER HAVING THE DESIRED THICKNESS OF THE ULTIMATE FILM ONTO A ROTATING DRUM CONSTITUTED BY AN INNER HIGH THERMAL CONDUTIVITY METALLIC BASE AND AN OUTER INSULATING COATING OF LOW THERMAL CONDUCTIVITY MATERIAL OF PREDETERMINED THICKNESS, AND SUBJECTING THE MOVING COMPOSITE LAMINATED STRUCTURE CONSTITUTED BY SAID LAYER, SAID COATING AND SAID BASE TO A TEMPERATURE DIFFERENTIAL TO ESTABLISH IN SAID LAYER A TEMPERATURE GRADIENT RANGING FROM A TEMPERATURE SUBSTANTIALLY ABOVE THE FUSION TEMPERATURE OF SAID FILM-FORMING MATERIAL BUT BELOW THE DTERIORATION TEMPERATURE THEREOF AT THE OUTERMOST SURFACE OF SAID LAYER REMOTE FROM SAID COATING TO A TEMPERATURE JUST ABOVE SAID FUSION TEMPERATURE AT THE INNERMOST SURFACE OF SAID LAYER ADJACENT SAID COATING, BY IMPINGING ON THE EXPOSED SURFACE OF SAID LAYER A STREAM OF HOT GASIOUS FLUID AT AN ANGLE INCLINED LESS THAN APPROXIMATELY 60* TO A PLANE NORMAL TO SAID LAYER AND AT A LINEAR VELOCITY BETWEEN APPROXIMATELY 4,000 AND 10,000 FEET PER MINUTE AND BY EXTRACTING HEAT FROM THE OPPOSITE SURFACE OF SAID LAYER, SAID STEP OF EXTRACTING HEAT FROM SAID LAYER BEING CONTINUED IN A REGION OF SAID COATING AND SAID BASE SUBSTANTIALLY DISPLACED FROM THE REGION OF IMPINGEMENT OF SAID HOT GASEOUS FLUID TO SOLIDIFY SAID LAYER WHILE SAID LAYER IS ON SAID SUPPORTING SURFACE.