Retortable/peelable film
A material suitable for sealing plastic containers and used as a lid on a container for food is disclosed. The material comprises a substrate joined to a film comprising a mixture of a butene-1 polymer, polypropylene, an organic filler, and, optionally, high density polyethylene. The material is heat sealable, peelable and retains high burst strength both during and after retorting at elevated temperatures.
1 . A peelable and heat sealable material for bonding to a polypropylene and polypropylene coated substrates, comprising a solid substrate joined to a film, the film comprising:
a sealing layer, the sealing layer including about 20-30 weight % of a particulate inorganic filler; about 5-20 weight % of a butene-1 polymer; and about 35-65 weight % of polypropylene; and
a carrier layer, the carrier layer including polypropylene.
2 . The material of claim 1 wherein the sealing layer further comprises about 20-30 weight % of a high density ethylene polymer.
3 . The material of claim 1 wherein the substrate material is a lidstock material and comprises at least one material selected from metal, foil, and paper.
4 . The material of claim 1 wherein the inorganic material comprises talc, silica, or alumina.
5 . The material of claim 1 wherein the substrate material is a lidstock material and comprises aluminum foil.
6 . The material of claim 1 wherein said sealing layer comprises about 15 weight % of a butene-1 polymer.
7 . The material of claim 1 wherein said sealing layer comprises about 60 weight % of polypropylene.
8 . The material of claim 1 wherein said sealing layer comprises about 25 weight percent of inorganic filler.
9 . The material of claim 8 wherein said inorganic filler comprises talc.
10 . The material of claim 2 wherein said sealing layer comprises about 10 weight % of a butene-1 polymer.
11 . The material of claim 2 wherein said sealing layer comprises about 40 weight % of polypropylene.
12 . The material of claim 2 wherein said sealing layer comprises about 25 weight percent of inorganic filler.
13 . The material of claim 12 wherein said inorganic filler comprises talc.
14 . The material of claim 2 wherein said sealing layer comprises about 25 weight % of high density polypropyelene.
15 . The material of claim 1 wherein said material is peelable and heat sealable.
16 . The material of claim 1 wherein said material has a burst strength of about between 38-48 pounds per square inch at 250° F.
17 . The material of claim 1 wherein said material has a burst strength of about between 30-40 pounds per square inch at about 270° F.
18 . A lid for a plastic container comprising a peelable and heat sealable material having a solid substrate joined to a film, the film comprising:
a sealing layer, the sealing layer including about 20-30 weight % of a particulate inorganic filler; about 5-20 weight % of a butene-1 polymer; and about 35-65 weight % of polypropylene; and
a carrier layer, the carrier layer including polypropylene.
19 . The lid of claim 18 wherein the sealing layer further comprises about 20-30 weight % of a high density ethylene polymer.
20 . A container comprising a body having an edge defining an opening and a flange extending radially outwardly of said opening, and a lid comprising the lidstock a peelable and heat sealable material having a solid substrate joined to a film, the lid heat sealed to the flange, the film comprising:
a sealing layer, the sealing layer including about 20-30 weight % of a particulate inorganic filler; about 5-20 weight % of a butene-1 polymer; and about 35-65 weight % of polypropylene; and
a carrier layer, the carrier layer including polypropylene.
21 . The lid of claim 20 wherein the sealing layer further comprises about 20-30 weight % of a high density ethylene polymer.