VERFAHREN ZUR REGELUNG DER FOLIENDICKE VON IM BLASVERFAHREN HERGESTELLTEN UND AXIAL, VORZUGSWEISE BIAXIAL VERSTRECKTEN SCHLAUCHFOLIEN

• Main Authors: FEISTKORN, WERNER. DR., 4401 SAERBECK, DE, VOSS, KLAUS-PETER., 4540 LENGERICH, DE
• Format: Patent
• Language: German
• Published: 20.06.1991
• Subjects: AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING; INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULARARTICLES; PERFORMING OPERATIONS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDEDFOR; SHAPING OR JOINING OF PLASTICS; TRANSPORTING; WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL

For the axial, preferably biaxial stretching of tubular films laid flat after their production on a blown film extruder line, the said films are inflated again to form a tubular film bubble (4) or are expanded to form a film tube. In the inflated or expanded state, these then run through an oven (11), from which they are drawn off, with renewed flattening (12), at a rate which is increased with respect to the running-in rate by an amount corresponding to the desired stretching ratio. In order to ensure that the stretched tubular films have a substantially equal thickness distribution over their circumference, the film thickness of the stretched tubular film emerging from the oven (11) is measured over its circumference before or after its flattening (12) and the thickness distribution over the circumferential profile of the tubular film produced on the blown film extruder line is set according to the measured thicknesses of the circumferential profile in such a way as to compensate substantially for deviations from the average film thickness brought about in the oven during stretching on account of uneven heating and possibly other disturbing influences.