Multilayer heat-shrinkable asymmetrical film

Abstract

It is illustrated a multilayer heat-shrinkable asymmetrical film comprising at least the following layers: an outer sealing layer; an inner barrier layer; and an outer skin layer comprising a blend of at least one polyamide and at least one polyester wherein the percentage of polyamide in the blend is at least 60%.

1 . A multilayer heat-shrinkable asymmetrical film comprising an outer sealing layer; an inner barrier layer; and an outer skin layer comprising a blend of at least one polyamide and at least one polyester, wherein the percentage of polyamide in the blend is at least 60% by weight. 
     
     
         2 . The film according to  claim 1  wherein the sealing layer comprises a single polyolefin or a blend of two or more polyolefins. 
     
     
         3 . The film according to  claim 1  wherein the barrier layer is made of a thermoplastic resin selected from saponified or hydrolyzed products of ethylene-vinyl acetate copolymers, amorphous polyamides, and vinyl-vinylidene chloride copolymers. 
     
     
         4 . The film according to  claim 1  wherein the skin layer comprises a blend of between 90% to 60% by weight polyamide and between 10% to 40% by weight polyester. 
     
     
         5 . The film according to  claim 4  wherein the skin layer comprises at least 50% of the blend. 
     
     
         6 . The film according to  claim 1  wherein the blend of the skin layer comprises a polyamide with a melting temperature higher than 170° C. 
     
     
         7 . The film according to  claim 1  wherein the skin layer comprises a polyamide selected from the group consisting of copolyamides 6/12, copolyamides of polyamide 6 and a partially aromatic polyamide and ternary copolyamides based on polyamide 6, polyamide 11, polyamide 66 or blends thereof. 
     
     
         8 . The film according to  claim 1  wherein the blend of the skin layer comprises a polyester selected form the group consisting of PET, PETG or blends thereof. 
     
     
         9 . The film according to  claim 1  wherein the skin layer comprises a blend of 80% by weight of polyamide 6 and 20% by weight of PET. 
     
     
         10 . The film according to  claim 1  further comprising a tie layer comprising an adhesive polymer selected from ethylene copolymers or terionomers modified with maleic anhydride, and EVA/ethylene methacrylic acid copolymer. 
     
     
         11 . The film according to  claim 1  manufactured according to a triple bubble process. 
     
     
         12 . The film according to  claim 11  wherein the triple bubble process comprises at least one additional heating treatment, between the second bubble and the third bubble, wherein the heating temperature is between 35° C. and 65° C. 
     
     
         13 . The film according to  claim 12  wherein said additional heating treatment is carried out for a period of time between 0.1 second and 7.5 seconds. 
     
     
         14 . A product packaged with a film according to  claim 1  wherein the outer sealing layer is in contact with the packaged product. 
     
     
         15 . The multilayer heat-shrinkable asymmetrical film according to  claim 1  for use in tray lidding applications. 
     
     
         16 . The film according to  claim 3 , the thermoplastic resin comprises EVOH, and the skin layer comprises a blend of between 85% to 75% by weight polyamide and between 15% to 25% by weight polyester, and the blend is present in the skin layer in an amount of at least 80 weight %, the polyamide is selected from the group consisting of polyamide 6, polyamide 6 copolymers comprising less than 5% of an aromatic co-monomer, polyamide 66, polyamides 6/66, polyamides 6/12 or blends thereof, and the polyamide has a melting temperature higher than 200° C. 
     
     
         17 . The film according to  claim 16  wherein the seal layer comprises at least one member selected from the group consisting of polyethylene and polypropylene, and the blend is present in the skin layer in an amount of at least 90 weight %, and the polyamide has a melting temperature between 210° C. and 250° C., and the polyamide is selected from the group consisting of polyamide 6, modified polyamide 6, polyamide 66, and blends thereof. 
     
     
         18 . The film according to  claim 17  wherein the blend in the skin layer comprises 80% by weight of polyamide and 20% by weight of polyester, and the skin layer comprises at least at least 95 weight % of the blend. 
     
     
         19 . The film according to  claim 12  wherein the heating temperature is between 40° C. and 60° C., and the additional heating treatment is carried out for a period of time of between 0.1 second and 7.5 seconds. 
     
     
         20 . The film according to  claim 19  wherein the heating temperature is about 50° C. and the additional heating treatment is carried out for a period of time of between 0.5 second and 5 seconds. 
     
     
         21 . The film according to  claim 19  wherein the additional heating treatment is carried out for a period of time of between 0.5 second and 3 seconds.