System adds barrier, easily, to single-layer sheet

ExtrusionProviding gas and moisture barrier to sheet that can be thermoformed into packaging generally is done using multiple extruders to create a separate coextrusion film bonded to a single-layer sheet. This equipment manufacturer says it has come up with an easy way to give single-layer extruded sheet the needed barrier properties with such a barrier film laminated to one side of the sheet. Film lamination on sheet extrusion lines has been carried out for some time by introducing a separate film at the first nip near the die, says the company. However, this has the disadvantage of sometimes destroying the film if a bank arises at this point, which can destroy the barrier effect. The new patent-pending system from this producer applies the film by means of a cooled pressure roll after the sheet has passed through the first nip. At this point, the sheet is formed and flat so there is no longer the danger of a bank forming. It permits production of barrier polypropylene and PET sheet with heat-sealing layers for lidding. The sheet surface remains hot enough for film adhesion since it has only had a momentary contact with the upper roll of the 3-roll stack. Welex Inc., Blue Bell, PA, U.S.A.; +1 215-542-8000; www.welex.com