Manufacture of film having formed fastener means therein

Claim 1

In a method of manufacturing film, the steps of: a. continuously extruding a seamless tube of film while providing pressure internally to the tube, and then collapsing the moving tube at an area remote from the point of extrusion, b. integrally extruding with the tube, a first thickened profile defining a continuous gap the width of which is sensitive to hoop tension in the tube during a period of its manufacture, and at least a second thickened profile spaced circumferentially from the gap defining profile and adapted to be interlockingly receivable in said gap by means of cooperative sizing and configuration between the profiles, said profiles extending continuously in the direction of extrusion along the inner surface of the tube, c. clasping the tube between opposed racks of heat conductive roller means for a substantial extent of the area betweent the film frost line and the frost line of the profiles, said roller means rotatably engaging opposite sides of the moving tube, and externally contacting the area comprising the base of the gap defining profile at a time in the process when the ultimate gap width is sensitive to hoop tension, and d. cooperatively with step (c), cooling the rotating roller means to withdraw heat from said base area, said heat withdrawal step being practiced at a rate to control the width of the gap defining profile with respect to the size of the profile receivable therein, to thereby establish a proper interlocking relationship between said profiles.