Peelable closure for container
View Patent ↗A steam-ventable package includes a container formed to include an interior region and a mouth opening into the interior region and a closure coupled to the container to close the mouth. The closure is made from a peelable film coupled to a brim included in the container and configured to be removed from the brim in response to application of shear force applied to the peelable film.
1. A cold-durable, heat-resistant, peelable film for packaging a food product, comprising
(a) a sealant layer and
(b) a protective layer, wherein
i) the sealant layer is a polypropylene-based monolayer polyolefin layer comprising polypropylene blended with at least one polyethylene polymer resin selected from the group consisting of an ethylene/octene copolymer, linear low density polyethylene, low density polyethylene, high density polyethylene, ethylene vinyl acetate, and ethylene methyl acrylate, or a polypropylene-based multilayer polyolefin film comprising an inner heat sealable sub-layer comprising polypropylene blended with at least two different polyethylene polymer resins each selected from the group consisting of an ethylene/octene copolymer, linear low density polyethylene, low density polyethylene, high density polyethylene, ethylene vinyl acetate, and ethylene methyl acrylate,
ii) the sealant layer does not fracture when exposed to a temperature in a range of about −20° C. to about 0° C.,
iii) the sealant layer does not melt or burst when exposed to a temperature of up to about 105° C.,
iv) the sealant layer is adapted to be peeled from a polypropylene substrate either before or after heating with a peel force in a range of about 1 lbf/in to about 5 lbf/in,
v) the protective layer is included as part of the sealant layer when the sealant layer is the polypropylene-based multilayer polyolefin film, and
wherein the sealant layer is adapted to form a closure with the polypropylene substrate and to peel away easily so that the closure remains in one piece upon separation from the polypropylene substrate and wherein the inner heat sealable sub-layer is in contact with the polypropylene substrate when the sealant layer is the polypropylene-based multilayer film.
2. The cold-durable, heat-resistant, peelable film of claim 1 , wherein the sealant layer is a polypropylene-based multilayer polyolefin layer comprising
(a) the inner heat sealable sub-layer, wherein the inner heat sealable sub-layer is formed from at least one polypropylene/alpha-olefin copolymer, the polypropylene/alpha-olefin copolymer having a melt flow rate in a range of about 0.5 g/10 min. to about 45 g/10 min, and at least two different polyethylene polymer resins one of which has a melt index in a range of about 0.50 g/10 min. to about 20 g/10 min,
(b) a core sub-layer adjacent to the inner heat sealable sub-layer, the core sub-layer being formed from a polymeric material having a melting point of at least 71° C., and
(c) an outer skin sub-layer formed from at least one polyethylene polymer resin, the at least one polyethylene polymer resin having a melt index in a range of about 0.50 g/10 min. to about 20 g/10 min,
wherein the protective layer is laminated to the outer skin sub-layer, the protective layer being formed from a polymer material that is temperature resistant at a temperature of up to about 105° C.
3. The cold-durable, heat-resistant, peelable film of claim 2 , wherein the polypropylene/alpha-olefin copolymer comprises a propylene/ethylene copolymer containing ethylene comonomer in an amount in a range of about 1% to about 8% by weight of the copolymer.
4. The cold-durable, heat-resistant, peelable film of claim 2 , wherein the inner heat sealable sub-layer comprises a blend of polypropylene/alpha-olefin copolymers.
5. The cold-durable, heat-resistant, peelable film of claim 4 , wherein the blend of polypropylene/alpha-olefin copolymers comprises a propylene/ethylene copolymer containing ethylene comonomer in an amount in a range of about 1% to about 8% by weight.
6. The cold-durable, heat-resistant, peelable film of claim 2 , wherein the polypropylene/alpha-olefin copolymer has a melting temperature greater than 71° C.
7. The cold-durable, heat-resistant, peelable film of claim 2 , wherein the core sub-layer comprises a homopolymer polypropylene and a polyethylene polymer resin.
8. The cold-durable, heat-resistant, peelable film of claim 7 , wherein the homopolymer polypropylene has a melt flow rate in a range of about 0.5 g/10 min. to about 25 g/10 min.
9. The cold-durable, heat-resistant, peelable film of claim 7 , wherein the polyethylene polymer resin has a melt index in a range of about 0.50 g/10 min. to about 20 g/10 min.
10. The cold-durable, heat-resistant, peelable film of claim 2 , wherein the outer skin sub-layer includes a homopolymer polypropylene having a melt flow rate in a range of about 0.5 g/10 min. to about 25 g/10 min.
11. The cold-durable, heat-resistant, peelable film of claim 2 , wherein the protective layer is formed from a material selected from the group consisting of a polyethylene terephthalate film, a nylon film, a biaxially oriented polypropylene film, and a biaxially oriented propylene/ethylene copolymer film.
12. The cold-durable, heat-resistant, peelable film of claim 2 , wherein an adhesive layer is used to laminate the protective layer to the outer skin sub-layer.
13. The cold-durable, heat-resistant, peelable film of claim 12 , wherein the adhesive layer comprises a polyurethane adhesive.
14. The cold-durable, heat-resistant, peelable film of claim 12 , wherein the adhesive layer is formed from a material selected from the group consisting of a polyurethane adhesive, polyester-polyurethane adhesive, a hot-melt of ethylene vinyl acetate, a hot-melt of polyamide, and a hot-melt of polyester.
15. The cold-durable, heat-resistant, peelable film of claim 2 , wherein the multilayer polyolefin layer is either a coextruded blown film, a coextruded cast film, or a laminated film.
16. The cold-durable, heat-resistant, peelable film of claim 1 , wherein the sealant layer is a polypropylene-based multilayer polyolefin layer comprising
(a) the inner heat sealable sub-layer, wherein the inner heat sealable layer is formed from at least one polypropylene/alpha-olefin copolymer, the polypropylene/alpha-olefin copolymer having a melt flow rate in a range of about 0.5 g/10 min. to about 45 g/10 min, and at least two different polyethylene polymer resins one of which has a melt index in a range of about 0.50 g/10 min. to about 20 g/10 min,
(b) a core sub-layer adjacent to the heat sealable sub-layer, the core sub-layer being formed from a polymeric material having a melting point of at least 71° C., and
(c) an outer skin sub-layer formed from a homopolymer polypropylene resin, the homopolymer polypropylene resin having a melt flow rate in a range of about 0.50 g/10 min. to about 25 g/10 min,
wherein the protective layer is the outer skin sub-layer.
17. The cold-durable, heat-resistant, peelable film of claim 16 , wherein the inner heat sealable sub-layer comprises a blend of polypropylene/alpha-olefin copolymers.
18. The cold-durable, heat-resistant, peelable film of claim 17 , wherein the blend of polypropylene/alpha-olefin copolymers comprises a propylene/ethylene copolymer containing ethylene comonomer in an amount in a range of about 1% to about 8% by weight.
19. The cold-durable, heat-resistant, peelable film of claim 16 , wherein the polypropylene/alpha-olefin copolymer has a melting temperature greater than 71° C.
20. The cold-durable, heat-resistant, peelable film of claim 16 , wherein the core sub-layer comprises at least one homopolymer polypropylene and at least one polyethylene polymer resin.
21. The cold-durable, heat-resistant, peelable film of claim 16 , wherein the polypropylene-based multilayer polyolefin film is either a coextruded blown film, a coextruded cast film, or a laminated film.
22. The cold-durable, heat-resistant, peelable film of claim 1 , further comprising a venting system.
23. The cold-durable, heat-resistant, peelable film of claim 1 , wherein the sealant layer may be peeled from the polypropylene substrate either before or after heating with a peel force in a range of about 1 lbf/in to about 3 lbf/in.
24. A cold-durable, heat-resistant, peelable film for packaging a food product, comprising
(a) a sealant layer and
(b) a protective layer, wherein
i) the sealant layer is a polypropylene-based monolayer polyolefin layer comprising polypropylene blended with at least one polyethylene polymer resin, or a polypropylene-based multilayer polyolefin film comprising polypropylene blended with at least two different polyethylene polymer resins,
ii) the sealant layer does not fracture when exposed to a temperature in a range of about −20° C. to about 0° C.,
iii) the sealant layer does not melt or burst when exposed to a temperature of up to about 105° C.,
iv) the sealant layer is adapted to be peeled from a polypropylene substrate either before or after heating with a peel force in a range of about 1 lbf/in to about 5 lbf/in,
v) the protective layer is included as part of the sealant layer when the sealant layer is the polypropylene-based multilayer polyolefin film, and
wherein the sealant layer is adapted to form a closure with the polypropylene substrate and to peel away easily so that the closure remains in one piece upon separation from the polypropylene substrate.