Sandwich foil for fluid, e.g.milk, packaging - with plane foil bonded to recessed foil closed by third plane foil

摘要

Material consists of a first plastic (polyethylene) foil to which a second plastics (polypropylene)layer is applied between rolls from a slotted extrusion nozzle. One of the rolls has slight projections so that the second foil solidifies with a patter of recesses on its surface. A third foil is applied between another pair of rolls, this foil is made of the same material as the first and closes the recesses on the surface of the second foil. The second foil can be softened by heating to make it suitable for hot sealing, without affecting the strength of the first foil. The recesses save material but they do not turn the foil into an absorbent like paper or cardboard.