FILM ESTENSIBILE A PERMEABILITA' AI GAS CONTROLLATA, PARTICOLARMENTE PER L'IMBALLAGGIO DI PRODOTTI ALIMENTARI E RELATIVO METODO DI FABBRICAZ

摘要

A stretch film presenting controlled permeability to gases, manufactured by process of balloon co-extrusion and consisting of outer layers (S 2 ) of stretchable polmeric material and by one or two inner barrier layers (S 3 ) of a EVOH based polymeric matrix, which is made stretchable by the addition of a suitable plasticizer in such a percentage as to conciliate the stretchablity with the desired barrier effect, said layers of different material being reciprocally secured by means of layers (S 4 ) of adhesive material. The polymeric matrix which forms the barrier material and the plasticizer are intimately mixed inside a double-screw corotating extruder, immediately before the phase of co-extrusion, through a premelting of the polymeric matrix and the subsequent injection of the plasticizer in liquid phase.