Multilayer heat-shrink plastics material film

Abstract

The invention provides a multilayer heat-shrink film, comprising a central first layer made up of a first composition comprising at least one polyolefin; intermediate second layers made up of a second composition and covering respective faces of the first layer, the second composition comprising a styrene-based resin; and outer third layers made up of a third composition and covering respective ones of the intermediate second layers, the third composition comprising at least one polyester.

What is claimed is: 
     
         1 . A multilayer heat-shrink film, characterized in that it comprises:
 a central first layer made up of a first composition comprising at least one polyolefin;   intermediate second layers made up of a second composition and covering respective faces of the first layer, the second composition comprising a styrene-based resin; and   outer third layers made up of a third composition and covering respective ones of the intermediate second layers, the third composition comprising at least one polyester.   
     
     
         2 . The film according to  claim 1 , wherein the resin of the second composition comprises at least one thermoplastic elastomer based on a styrene-block copolymer. 
     
     
         3 . The film according to  claim 2 , wherein the styrene-block copolymer is a polystyrene-polybutadiene-polystyrene block copolymer. 
     
     
         4 . The film according to  claim 3 , wherein the polystyrene-polybutadiene-polystyrene block copolymer comprises 70% by weight styrene units relative to the total weight of the block copolymer. 
     
     
         5 . The film according to  claim 4 , wherein the resin of the second composition comprises, in addition to the following compound:
 a) the polystyrene-polybutadiene-polystyrene block copolymer, as first block copolymer, having 70% by weight of styrene units relative to the total weight of the first block copolymer;   at least one of the compounds selected from:   b) a second polystyrene-polybutadiene-polystyrene block copolymer having less than 70% by weight of styrene units relative to the total weight of the second block copolymer; and   c) a polystyrene.   
     
     
         6 . The film according to  claim 5 , wherein the compounds a), b), c) are in the resin at respective weight proportions lying in the following respective ranges a): [30%, 80%]; b): [0%, 70%]; c): [0%, 30%]; the sum of the three proportions being equal to 100%. 
     
     
         7 . The film according to  claim 1 , wherein the first composition comprises one or more polyolefins selected from:
 d) a first linear low-density polyethylene;   e) a second linear low-density polyethylene;   f) a high-density polyethylene;   g) a metallocene-catalyzed linear low-density polyethylene; and   h) a propropylene.   
     
     
         8 . The film according to  claim 7 , wherein the polyolefins d), e), f), g), and h) are present in the first composition at respective weight proportions lying in the following respective ranges d): [20%, 40%]; e): [30%, 60%]; f): [20%, 40%]; g): [30%, 70%]; and h): [0%, 40%]; the sum of the weight proportions being equal to 100%. 
     
     
         9 . The film according to  claim 1 , wherein the third composition comprises one or more compounds selected from:
 i) a 1,4 cyclohexanedimethanol modified polyethylene terephthalate;   j) a polyester or a copolyester having a low glass transition temperature;   k) a neopentyl glycol modified polyethylene terephthalate; and   l) a crystallizable polyester.   
     
     
         10 . The film according to  claim 9 , wherein the compounds i), j), k), and l) are present in the third composition in respective weight proportions lying in the following respective ranges i): [0%, 99%]; j): [0%, 40%]; k): [0%, 99%]; and l): [0%, 20%]; the sum of the weight proportions being equal to 100%. 
     
     
         11 . The film according to  claim 9 , wherein the compound j) is a diethylene glycol modified polyethylene terephthalate. 
     
     
         12 . The film according to  claim 9 , wherein the compound l) is polyethylene terephthalate. 
     
     
         13 . The film according to  claim 9 , wherein the third composition further comprises at least one slip agent such as a silicate or a mixture of talc and a fatty acid amide or a mixture of a plurality of fatty acid amides. 
     
     
         14 . The film according to  claim 1 , wherein the central first layer has thickness lying in the range 55% to 70% of the total thickness of the film, the intermediate second layers together have thickness lying in the range 15% to 30% of the total thickness of the film, and the outer third layers together have thickness lying in the range 15% to 30% of the total thickness of the film. 
     
     
         15 . The film according to  claim 1 , wherein each of the outer third layers comprises a compound having an emission spectrum in the near infrared that is centered on a wavelength lying in the range 1400 to 1900 nanometers. 
     
     
         16 . The film according to  claim 15 , wherein the compound is a varnish covering the free surfaces of the two outer third layers. 
     
     
         17 . The film according to  claim 15 , wherein the compound is incorporated in the third composition in such a manner that the two outer third layers have an emission spectrum in the near infrared centered on a wavelength lying in the range 1400 to 1900 nanometers. 
     
     
         18 . The film according to  claim 17 , wherein the compound comprises polyethylene terephthalate. 
     
     
         19 . The film according to  claim 17 , wherein the compound comprises a glycol modified polyester or an acid modified polyester.