초록 ▼

A multi-layer, thermoplastic film bi-axially oriented at a stretching ratio ≧ to about 3.0:1 in the machine direction and at a stretching ratio ≧ about 6.0:1 in the transverse direction, which film comprises a layer a) comprising at least 50 wt. % of a crystalline or partially crystallin

A multi-layer, thermoplastic film bi-axially oriented at a stretching ratio ≧ to about 3.0:1 in the machine direction and at a stretching ratio ≧ about 6.0:1 in the transverse direction, which film comprises a layer a) comprising at least 50 wt. % of a crystalline or partially crystalline co-polyamide characterized by a Tg≦100째 C. and at least one outer heat-sealing layer b) comprising a polyolefin, said film being further characterized in that it has a % free shrink at 100째 C. ≦3 in each direction.

대표청구항 ▼

The invention claimed is: 1. A multi-layer, thermoplastic film, bi-axially oriented at a stretching ratio greater than or equal to 3.0:1 in the machine direction and at a stretching ratio greater than or equal to 6.0:1 in the transverse direction, which film comprises a) a layer comprising at least

The invention claimed is: 1. A multi-layer, thermoplastic film, bi-axially oriented at a stretching ratio greater than or equal to 3.0:1 in the machine direction and at a stretching ratio greater than or equal to 6.0:1 in the transverse direction, which film comprises a) a layer comprising at least 50 wt.% of a crystalline or partially crystalline co-polyamide characterized by a Tg less than or equal to 100째 C., and b) an outer heat-sealing layer comprising a polyolefin in, said film being further characterized in that it has a % free shrink at 100째 C. less than or equal to 3 in each of the machine and transverse directions. 2. The film of claim 1 wherein the film is bi-axially oriented at a stretching ratio greater than or equal to 3.5:1 in the machine direction and at a stretch-ing ratio greater than or equal to 6. 2:1 in the transverse direction. 3. The film of claim 1 wherein the crystalline or partially crys-talline co-polyamide characterized by a Tg less than or equal to 100째 C. of layer a) is selected from the group consisting of a) aliphatic co-polymer obtained by co-polymerization of ε-caprolactam and ω-laurolactam, b) aliphatic co-polymer obtained by co-polymerization of ε-caprolactam, hexamethylenediamine and azelaic acid, c) polyamide co-polymer obtained from meta-xylylendiamine, adipic acid and isophthalic acid and d) polyamide co-polymer obtained from hexamethylenediamine, metaxylylendiamine, adipic acid, and sebacic acid. 4. The film of claim 1 wherein the co-polyamide of layer a) is used alone or in admixture with less than about 50 wt.% of another resin selected from the group consisting of a) crystalline or partially crystalline polyamide having a Tg greater than 100째 C., b) amorphous polyamide, c) ethylene-vinyl alcohol copolymer, d) polyester and e) co-polyester. 5. The film of claim 1 wherein the polyolefin in of the outer heat-sealing layer b) has a melting point less than 150 C. 6. The film of claim 5 wherein the polyolefin in of the outer heat-sealing layer b) has a melting point of from 80째 C. to 135째 C. 7. The film of claim 1 wherein the outer heat-sealing layer b) comprises one or more polymers selected from the group consisting of a) heterogeneous or homogeneous ethylene-(C4-C 8)-α-olefin copolymer having a density less than or equal to 0. 925 g/cm3; b) a blend of i) a heterogeneous or homogeneous ethylene-(C4-C 8)-α-olefin co-polymer having a density less than or equal to 0.925 g/cm3 with ii) a minor amount of polyethylene homopolymer or heterogeneous or homogeneous ethylene-(C4-C8)-α-olefin copolymer having a density greater than 0.925 g/cm3; c) ethylene-vinyl acetate copolymer; d) ethylene-acrylic or methacrylic acid copolymer; e) ionomer resin; f) a blend of i) heterogeneous or homogeneous ethylene-(C4-C 8)-α-olefin co-polymer having a density from 0.915 g/cm3 to 0.935 g/cm3 with ii) ethylene-vinyl acetate copolymer or ethylene-alkyl (meth) acrylate copolymer; g) ethylene-propylene-co-polymer; h) ethylene-propylene-butene ter-polymer; and i) ethylene-alkyl acrylate-maleic anhydride ter-polymer. 8. The film of claim 1 wherein a tie layer c) is positioned be-tween the layer a) comprising the co-polyamide and the outer heat-sealing polyolefin layer b) wherein said tie layer comprises a material selected from the group consisting of i) an ethylene-α-olefin co-polymer having an acid functionality grafted thereon; ii) an ethylene-α-olefin co-polymer having an acid functionality co-polymerized therewith; iii) an ethylene-α-olefin co-polymer having an acid functionality blended therewith; iv an ethylene-α-olefin co-polymer having an anhydride functionality grafted thereon; an ethvlene-α-olefin co-polymer having an anhydride functionality co-polymerized therewith; vi) an ethylene-α-olefin co-polymer having an anhydride functionality blended therewith; vii) co-polymer of ethylene and an ethylenically unsaturated es-ter having an acid functionality grafted thereon; viii) a co-polymer of ethylene and an ethylenically unsaturated ester having an acid functionality co-polymerized therewith; ix) a co-polymer of ethylene and an ethylenically unsaturated ester having an acid functionality blended therewith; x a co-polymer of ethylene and an ethylenically unsaturated ester having an anhydride functionality grafted thereon; xi) a co-polymer of ethylene and an ethylenically unsaturated ester having an anhydride functionality co-polymerized therewith; and xii) a co-polymer of ethylene and an ethylenically unsaturated ester having an anhydride functionality blended therewith. 9. The film of claim 1 wherein i) the co-polyamide layer a) is an internal layer; and ii) the film further comprises a second outer layer d), the second outer layer d) comprising a material selected from the group consisting of (a) polyolefin in; (b) polyamide; and (c) polyester. 10. The film of claim 9 wherein the outer layer d) comprises one or more polyolefins. 11. The film of claim 1 wherein the film comprises five layers wherein tie layers c) and c') are positioned between the internal co-polyamide layer a) and the outer layers b) and d) respectively. 12. The film of claim 1 wherein the film is coextruded. 13. The film of claim 1 wherein the film is irradiated. 14. A process of manufacture of a film comprising: a) stretching an extruded tape comprising i) a layer comprising at least 50 wt.% of a crystalline or partially crystalline co-polyamide characterized by a Tg less than or equal to 100째 C., and ii) at least one outer heat-sealing layer comprising a polyolefin in, in the machine direction with a stretching ratio of greater than or equal to 3.0:1 and in the transverse direction with a stretching ratio of greater than or equal to 6.0:1, either sequentially or simultaneously, at a suitably se-lected orientation temperature, to produce an oriented film, and then b) heat-setting the film; such that the heat set film is characterized by a % free shrink at 100째 C. less than or equal to 3 in each of the machine and transverse directions. 15. The process of claim 14 further comprising the step of ir-radiating the extruded tape before stretching the extruded tape.