Process and apparatus for producing laminated oriented thermoplastic film

Claim 1

A PROCESS FOR PRODUCING A CONTINUOUS STRIP OF REINFORCED THERMOPLASTIC POLYMERIC FILM WHICH COMPRISES: EXTRUDING A TUBE OF THERMOPLASTIC POLYMERIC MATERIAL IN ITS FORMATIVE STATE FROM A ROTATING ANNULAR DIE; ROTATING SAID TUBE AS IT IS ADVANCED FROM SAID DIE; PASSING THE ROTATING TUBE OVER A COOLED INTERNAL MANDREL TO COOL SAID TUBE TO A TEMPERATURE WHICH IS BELOW THE TEMPERATURE OF SAID MATERIAL IN ITS FORMATIVE STATE; MAINTAINING SUFFICIENT PRESSURE WITHIN SAID ROTATING TUBE TO AT LEAST PREVENT COLLAPSE OF SAID TUBE; ADVANCING SAID ROTATING TUBE AT A PREDETERMINED INITIAL RATE, HEATING SAID ROTATING TUBE TO THE ORIENTATION TEMPERATURE RANGE BY PASSING SAID TUBE OVER A HEATED INTERNAL MANDREL; PULLING SAID ROTATING TUBE AT A RATE OF FROM 2 TO 5 1/2 TIMES THE INITIAL RATE TO LONGITUDINALLY MONAXIALLY ORIENT SAID TUBE; COOLING SAID ROTATING TUBE SO ORIENTED TO A TEMPERATURE WHICH IS BELOW THE TEMPERATURE OF SAID MATERIAL IN THE FORMATIVE STATE BY PASSING SAID TUBE ABOUT A COOLED INTERNAL MANDREL; SLITTING SAID ROTATING ORIENTED TUBE INTO TWO STRIPS ALONG HELICAL LINES SUBSTANTIALLY AT 45* TO THE AXIS OF SAID TUBE; BRINGING SAID STRIPS INTO FACE-TO-FACE ENGAGEMENT IN SUCH A WAY THAT THE DIRECTION OF THE LINES OF ORIENTATION OF ONE OF SAID STRIPS IS SUBSTANTIALLY AT RIGHT ANGLES TO THE DIRECTION OF THE LINES OF ORIENTATION OF THE OTHER OF SAID STRIPS AND LAMINATING SAID STRIPS TOGETHER.