Film bead heating for simultaneous stretching

摘要

An improved process for simultaneous biaxial stretching of a thermoplastic polymer film having beaded edges in a tenter frame consisting of gripping the beaded edges of the film with tenter clips and increasing the temperature of the beaded edges to within the film orientation temperature range prior to or during simultaneous stretching, and in subsequent stretching or heat-setting steps, by focusing heat on the beaded edges of the film. Thermoplastic films, such as polyethylene terephthalate and polyethylene naphthalate, having a final thickness of from 0.2 to 350 microns after simultaneous stretching can be prepared./!