Multilayer heat-shrinkable films with improved mechanical properties

摘要

A multilayer heat-shrinkable film comprisesPPa heat- sealable layer (a);PPan inner layer (b) comprising a polymer selected from the group consisting of ethylene-vinyl acetate copolymers containing from 4 to 28% by weight of vinyl acetate units and with a fractional Melt Index, and ethylene-alkyl acrylate copolymers containing from 9 to 28% by weight of alkyl acrylate units and with a fractional Melt Index; PPan inner layer (c), face-to-face in contact with layer (b), comprising a polymer selected from the group consisting of ethylene- acrylic acid copolymers, ethylene-methacrylic acid copolymers, ethylene- vinyl acetate copolymers, ethylene-alkyl acrylate copolymers, heterogeneous ethylene--olefin copolymers, and homogeneous ethylene--olefin copolymers; andPP an additional layer (d) comprising a polymer selected from the group consisting of ethylene- vinyl acetate copolymers containing from 4 to 28% by weight of vinyl acetate units and with a fractional Melt Index, and ethylene-alkyl acrylate copolymers containing from 9 to 28% by weight of alkyl acrylate units and with a fractional Melt Index; face-to-face in contact with the side of layer (c) which is not in contact with layer (b); PPwherein the composition of layer (c) is different from that of layer (b) and (d), and the ratios by weight between layer (b) and layer (c), and between layer (d) and layer (c) are comprised between 0. 125 to 1 and 8 to 1.P PThe heat-shrinkable films according to the invention have very good mechanical properties such as puncture resistance, high shrink and good optical properties which render them particularly suitable for e.g. packaging of frozen foods.