Fornettet, biaksialt orientert, varmforseglbar flersjikts strekkfilm, hermetisk forseglet og evakuert næringsmiddelpakke samt fremgangsmåte for varmforsegling av flersjiktsstrekkfilmen

摘要

A crosslinked biaxially oriented heat shrinkable multilayer stretch film comprises (a) at least a first outer layer and a second outer layer comprising a blend of (1) 25-75 wt.% VLDPE having a density of 0.900-0.914 g/cm3 and (2) 25-75 wt.% LLDPE having a melt index below 3.5 g/10 mins. and a density of 0.917-0.925 g/cm3. the LLDPE comprising less than 35 wt.% of the total film wt.; and (b) a core layer comprising a blend of (1) 40-75 wt.% VLDPE having a density of 0.905-0.914 g/cm3, (2) 10-35 wt.% VLDPE having a density of 0.900-0.905 g/cm3, and (3) 15-35 wt.% ethylene/~a-olefin plastomer copolymer having a density below 0.900 g/cm3; when subjected to the Platen test on a plate heated to a contact surface temp. of 280-400 deg C for a contact time of 2-4 secs., the film heat seals and does not burn through. Also claimed are: (i) a hermetically sealed and evacuated food package comprising a tray with a bottom section surrounded by upwardly extending side and end walls, perishable food supported on the upper surface of the tray bottom section, and the above stretched heat shrink film extending over each of the food, the side and wall upper edges and at least part of the lower surface of the tray bottom section and heat sealed to itself in flattened relationship against the lower surface; and (ii) a process for platen heat sealing the overlying folded ends of multiple contiguous layers of the above stretched thermoplastic film covering a food-contg. tray comprising providing a flat metal plate as the platen surface, heating the upper surface of the plate to 300-400 deg F, contacting downwardly and inwardly pressed folded end portions of the stretched film cover with the heated metal plate for 2-4 secs. so as to bond the contiguous film layers of the folded end portion without burn through of the film, and immediately cooling heat bonded end portions of the film to below 200 deg F.