Pull-tab sealing member with improved heat distribution for a container
A seal and method of manufacture is provided for sealing containers such as bottles, jars and the like. The seal (i.e., closure) is formed with a lower sheet-like structure having a non-foam, heat-distributing layer thereon. The lower structure includes a foil support layer and has a polymer layer, such as a PET layer disposed on its bottom surface. A heat-activated sealant layer is provided under the bottom surface of the PET layer to bond the seal to a container opening. The non-foam, heat-distributing layer is preferably a polyolefin film. Seals in accordance with preferred embodiments of the invention also include a top portion, which is only partially bonded (directly or indirectly) to the bottom portion, so as to leave a tab portion extending from the seal. The top portion is advantageously bonded from periphery to periphery of the bottom portion and at or slightly offset from the diameter (middle) of the bottom portion. The top portion is advantageously formed with polymer material, such as an ethylene vinyl acetate (EVA) layer, having a layer of PET bonded on the top thereof. A release strip, which can have a release layer coated on the bottom thereof, is adhered to the top or bottom structures and used to prevent the tab from adhering to the lower structure.
1. A pull-tab sealing member, having a top side and a bottom side constructed to be secured to a lip around an opening of a container, to close the container, the pull-tab sealing member comprising:
a bottom member comprising a metal foil layer having a bottom surface for facing a container and a top surface on an opposite side thereof, a separate non-foam, heat-distributing polyolefin film layer having a top surface and a bottom surface, the bottom surface adhered to the top surface of the metal foil layer by an adhesive selected from the group consisting of ethylene acrylic acid copolymers, curable two part urethane adhesives, epoxy resins, and mixtures thereof, a lower polymer layer disposed on the bottom surface of the metal foil layer including a heat-activated sealant or adhesive coating for securing the bottom member to the container;
the non-foam, heat-distributing polyolefin film layer includes a blend of a first and a second polyolefin component, a density of the second polyolefin component greater than a density of the first polyolefin component, and a density of the non-foam, heat-distributing polyolefin layer from about 0.96 to about 0.99 g/cc; and
a top member comprising a top surface and bottom surface, a portion of the top member comprising a tab portion having a top and a bottom surface, the bottom surface of the tab portion not secured to the top surface of the non-foam, heat-distributing polyolefin film layer of the bottom member, and a portion of the bottom surface of the top member secured to the top surface of the non-foam, heat-distributing polyolefin film layer of the bottom member, the top member is secured to the bottom member in a sufficiently strong manner and the non-foam heat distributing polyolefin film layer is of a sufficient thickness so that when the heat-activated sealant or adhesive coating at the bottom surface of the bottom member is secured to a container, the bottom member can be removed by pulling on the tab portion without separating the tab portion from the top member or rupturing the non-foam heat-distributing polyolefin film layer.
2. The pull-tab sealing member of claim 1 , wherein the polyolefin is selected from the group consisting of polyethylene, polypropylene, ethylene-propylene copolymers and blends thereof.
3. The pull-tab sealing member of claim 1 , wherein the polyolefin film layer is at least about 2.5 mil thick.
4. The pull-tab sealing member of claim 1 , wherein a release strip is disposed at the bottom surface of the tab portion, positioned to face a portion of the top surface of the non-foam, heat-distributing polyolefin film layer of the bottom member and constructed to help prevent the tab portion from becoming affixed to the bottom member.
5. The pull-tab sealing member of claim 4 , wherein the release strip comprises PET.
6. The pull-tab sealing member of claim 5 , wherein the release strip has a layer of release material disposed on the bottom surface thereof facing the non-foam heat-distributing polyolefin film layer, the release material having less of a characteristic to adhere to the non-foam, heat-distributing polyolefin film layer than the PET layer.
7. The pull-tab sealing member of claim 1 , wherein the top member comprises a layer of PET and a layer of EVA under the PET layer.
8. The pull-tab sealing member of claim 4 , wherein there is written matter on the release strip.
9. The pull-tab sealing member of claim 1 , wherein the polyolefin film layer has a density of at least 0.97 g/cm 3 .
10. A pull-tab sealing member, having a top side and a bottom side constructed to be secured to a lip around an opening of a container, to close the container, the pull-tab sealing member comprising:
a bottom member comprising a metal foil layer having a bottom surface for facing a container and a top surface on an opposite side thereof, a non-foam, heat-distributing polyolefin layer having a top surface and a bottom surface, the bottom surface adhered to the top surface of the metal foil layer by an adhesive selected from the group consisting of ethylene acrylic acid copolymers, curable two part urethane adhesives, epoxy resins, and mixtures thereof, a lower polymer layer disposed on the bottom surface of the metal foil layer including a heat-activated sealant or adhesive coating so that the non-foam, heat-distributing polyolefin layer is disposed on the opposite side of the metal foil layer from the heat-activated sealant or adhesive coating;
the non-foam, heat-distributing polyolefin layer has a thickness of about 2.5 to about 10 mils and includes a blend of a first and a second polyolefin component, a density of the second polyolefin component greater than a density of the first polyolefin component, where the blend is about 50 to about 70 percent of the second polyolefin component to form a density of the non-form, heat-distributing layer from about 0.96 to about 0.99 g/cm 3 so that the non-foam, heat-distributing polyolefin layer is effective to redirect heat towards the lower polymer layer for securing the heat activated sealant or adhesive coating to the container; and
a top member comprising a top surface and bottom surface, a portion of the top member comprising a tab portion having a top and a bottom surface, the bottom surface of the tab portion not secured to the top surface of the non-foam, heat-distributing polyolefin layer of the bottom member, and a portion of the bottom surface of the top member secured to the top surface of the non-foam, heat-distributing polyolefin layer of the bottom member, the top member is secured to the bottom member in a sufficiently strong manner, so that when the heat-activated sealant or adhesive coating at the bottom surface of the bottom member is secured to a container, the bottom member can be removed by pulling on the tab portion.
11. The pull-tab sealing member of claim 10 , wherein the first polyolefin component is a medium density polyethylene and the second polyolefin component is a high density polyethylene.
12. The pull-tab sealing member of claim 1 , wherein the density of the non-foam, heat-distributing polyolefin layer is from about 0.97 to about 0.99 g/cc.
13. The pull-tab sealing member of claim 10 , wherein the density of the non-foam, heat-distributing polyolefin layer is from about 0.97 to about 0.99 g/cc.