Gas-barrier thermoplastic film and substrate/film composite material

Abstract

A gas-barrier multilayer film comprising at least an outer heat-sealable polyolefin layer, a core gas-barrier layer comprising one or more of EVOH and/or polyamides, and an outer bonding layer comprising one or more styrene-based polymers, characterized in that a) at least 35 percent by weight, preferably at least 38 percent by weight and even more preferably at least 40 percent by weight of the overall film is of styrene-based polymers, b) at least part of these “styrene-based polymers” are in the form of modified styrene-based polymers, and c) said modified styrene-based polymers are present in a ratio, with respect to the weight of the gas-barrier resin of the core layer, of at least 0.1:1, preferably at least 0.3:1, and even more preferably at least 0.5:1. The use of the new gas-barrier film as liner in the manufacture of a polystyrene/film composite allows to reclaim the entire scrap obtained in the overall process in the polystyrene substrate still obtaining composites with mechanical properties and packaging performances comparable to those of the original composites.

What is claimed is:  
     
         1 . A multilayer film comprising an outer heat-sealable polyolefin layer, a core gas-barrier layer comprising at least one gas barrier resin selected from the group consisting of EVOH and polyamide, and an outer bonding layer comprising styrene-based polymer which makes up at least 35 weight percent of the film, based on total film weight, the styrene-based polymer comprising modified styrene-based polymer, with the modified styrene-based polymer being present in the outer bonding layer in a ratio, with respect to the weight of the gas-barrier resin, of at least 0.1:1.  
     
     
         2 . The multilayer film according to  claim 1 , wherein the styrene-based polymer makes up at least 38 weight percent of the film, based on total film weight, and the modified styrene-based polymer being present in the outer bonding layer in a ratio, with respect to the weight of the gas-barrier resin, of at least 0.3:1.  
     
     
         3 . The multilayer film according to  claim 1 , wherein the styrene-based polymer makes up at least 40 weight percent of the film, based on total film weight, and the modified styrene-based polymer being present in the outer bonding layer in a ratio, with respect to the weight of the gas-barrier resin, of at least 0.5:1.  
     
     
         4 . The multilayer film according to  claim 1 , wherein the modified styrene-based polymer comprises anhydride grafted styrene-based polymer.  
     
     
         5 . The multilayer film according to  claim 4 , wherein the modified styrene-based polymer are maleic anhydride modified styrene block copolymers.  4 . A substrate/film composite comprising a substrate comprising styrene-based polymers and a gas-barrier multilayer film of  claim 1 .  
     
     
         6 . A substrate/film composite comprising a foam substrate and a multilayer film comprising an outer heat-sealable polyolefin layer, a core gas-barrier layer comprising at least one gas barrier resin selected from the group consisting of EVOH and polyamide, and an outer bonding layer comprising styrene-based polymer which makes up at least 35 weight percent of the film, based on total film weight, the styrene-based polymer comprising modified styrene-based polymer, with the modified styrene-based polymer being present in the outer bonding layer in a ratio, with respect to the weight of the gas-barrier resin, of at least 0.1:1.  
     
     
         7 . The substrate/film composite according to  claim 6 , wherein the foam substrate comprises polystyrene.  
     
     
         8 . The substrate/film composite according to  claim 6 , wherein the foam substrate comprises substrate/film composite reclaim in an amount of from about 0.001 percent up to about 100 percent, based on foam substrate weight.  
     
     
         9 . The substrate/film composite according to  claim 7 , wherein the foam substrate comprises substrate/film composite reclaim in an amount of from about 0.001 percent up to about 100 percent, based on foam substrate weight.  
     
     
         10 . The substrate/film composite according to  claim 8 , wherein the foam substrate comprises substrate/film composite reclaim in an amount of at least 20 percent, based on weight of foam substrate.  
     
     
         11 . The substrate/film composite according to  claim 10 , wherein the foam substrate comprises substrate/film composite reclaim in an amount of at least 30 percent, based on weight of foam substrate.  
     
     
         12 . The substrate/film composite according to  claim 11 , wherein the foam substrate comprises substrate/film composite reclaim in an amount of at least 40 percent, based on weight of foam substrate.  
     
     
         13 . The substrate/film composite according to  claim 12 , wherein the foam substrate comprises substrate/film composite reclaim in an amount of at least 50 percent, based on weight of foam substrate.  
     
     
         14 . The substrate/film composite according to  claim 13 , wherein the foam substrate comprises substrate/film composite reclaim in an amount of at least 60 percent, based on weight of foam substrate.  
     
     
         15 . The substrate/film composite according to  claim 9 , wherein the foam substrate comprises substrate/film composite reclaim in an amount of at least 20 percent, based on weight of foam substrate.  
     
     
         16 . A tray comprising a substrate/film composite comprising a foam substrate and a liner which comprising a multilayer film having an outer heat-sealable polyolefin layer, a core gas-barrier layer comprising at least one gas barrier resin selected from the group consisting of EVOH and polyamide, and an outer bonding layer comprising styrene-based polymer which makes up at least 35 weight percent of the film, based on total film weight, the styrene-based polymer comprising modified styrene-based polymer, with the modified styrene-based polymer being present in the outer bonding layer in a ratio, with respect to the weight of the gas-barrier resin, of at least 0.1:1.  
     
     
         17 . The tray according to  claim 16 , further comprising a bottom portion and side walls integral with the bottom portion, and a flange extending outwardly from top edges of the side walls.  
     
     
         18 . The tray according to  claim 17 , wherein the flange extends outwardly in a plane parallel to the bottom portion.  
     
     
         19 . A food package comprising: 
 (A) a tray comprising a substrate/film composite comprising a foam substrate and a liner comprising a multilayer film having an outer heat-sealable polyolefin layer, a core gas-barrier layer comprising at least one gas barrier resin selected from the group consisting of EVOH and polyamide, and an outer bonding layer comprising styrene-based polymer which makes up at least 35 weight percent of the film, based on total film weight, the styrene-based polymer comprising modified styrene-based polymer, with the modified styrene-based polymer being present in the outer bonding layer in a ratio, with respect to the weight of the gas-barrier resin, of at least 0.1:1, the tray having a flange around a perimeter thereof;    (B) a food product on an upper surface of the tray; and    (C) a film over the food product, the film being sealed along the flange of the tray.