Calendar rollers - with spiral cutting edge to disperse pockets in hard pvc film during degassing

摘要

During degassing at 180-210 degrees C. the action of the spiral cutting edge alloys any air or gas pockets developed between the under side of the roller blanket and the penultimate roller in the vertical roller array to disperse. By the time the material reaches the last gap in the roller chain, the material will have reasserted itself and the cuts closed giving a homogeneous hard PVC film without pockets or surface damage. The purpose is to provide a calendar process for hard PVC film or sheet of thicknesses in excess of 0.5 mm.