초록 ▼

The sealability of a thermoplastic, mono- or multi-layer film having an irradiated sealing layer comprising a polyethylene and/or an ethylene-x-olefin copolymer with a density ≥0.915 g/cm3is improved by corona treating said sealing layer. The integrity of the obtained sealed container is maintained

The sealability of a thermoplastic, mono- or multi-layer film having an irradiated sealing layer comprising a polyethylene and/or an ethylene-x-olefin copolymer with a density ≥0.915 g/cm3is improved by corona treating said sealing layer. The integrity of the obtained sealed container is maintained under pasteurizing or cook-in conditions.

대표청구항 ▼

1. A thermoplastic, mono- or multi-layer film comprising a sealing layer irradiated at a dosage of from about 50 kGy to about 180 kGy, wherein: the sealing layer comprises 80% or more by weight of the sealing layer of one or more polymers selected from polyethylene and ethylene-α-olefin copolymer

1. A thermoplastic, mono- or multi-layer film comprising a sealing layer irradiated at a dosage of from about 50 kGy to about 180 kGy, wherein: the sealing layer comprises 80% or more by weight of the sealing layer of one or more polymers selected from polyethylene and ethylene-α-olefin copolymer with a density ≥0.915 g/cm3,wherein the polyethylene and ethylene-α-olefin copolymer each have a density of less than 0.935 g/cm3; and the sealing layer is corana treated. 2. A film according to claim 1 which is heat-shrinkable. 3. A film according to claim 1 which is a multilayer film comprising in addition to the sealing layer a gas-barrier layer and an outer abuse layer. 4. A film according to claim 3 wherein the gas-barrier layer comprises at least one ethylene-vinyl alcohol copolymer. 5. A film according to claim 1 wherein the corona discharge energy level is such to provide the surface of the sealing layer with a wet tension strength of at least 30 dyne/cm (0.03 N/m). 6. A film according to claim 5 wherein the corona treatment energy level is from 150 to 500 mA. 7. A film according to claim I wherein the irradiation is carried out at a dosage of from about 60 to about 160 kGy. 8. A film according to claim 1 wherein the sealing layer comprises 80% or more by weight of the sealing layer of ethylene-α-olefin copolymer with a density ≥0.915 g/cm3. 9. A film according to claim 8 wherein the ethylene-α-olefin copolymer has a density between about 0.917 and about 0.930 g/cm3. 10. A film according to claim 8 wherein the ethylene-α-olefin copolymer has a melt flow index of from about 0.5 to about 2.5 g/10 min, measured according to ASTM D1238 Condition E. 11. A heat-sealed container comprising the a film of claim 9. 12. A film according to claim 1 wherein the sealing layer comprises at least 80% (by weight of the sealing layer) of polyethylene. 13. A heat-sealed container comprising the film of claim 12. 14. A heat-processable package comprising a container comprising the film of claim 1. 15. A method of packaging a heat-processable item comprising inserting said item into a container according to claim 14, closing it by clipping or sealing, and subjecting the package to a heat treatment. 16. A thermoplastic film having an irradiated and corona-treated sealing layer comprising at least 70% (by weight of the sealing layer) ethylene-α-olefin copolymer having a density 0.917 g/cm3and less than about 0.930 g/cm3. 17. The film of claim 16 wherein the sealing layer comprises at least 80%, by weight of the sealing layer, of ethylene-α-olefin copolymer having a density ≥0.917 g/cm3. 18. The film of claim 17 wherein the irradiation is carried out at a dosage of from about 50 KGy up to about 180 KGy. 19. A method of improving heat-sealability of a mono- or multi-layer film comprising a sealing layer irradiated at a dosage of from about 50 kGy to about 180 kGy, wherein the sealing layer comprises 80% or more by weight of the sealing layer of one or more polymers selected from a polyethylene and ethylene-α-olefin copolymer with a density ≥0.915 g/cm3,said method comprising submitting said sealing layer to a corona discharge treatment