Easy-open container and container coating
The present application provides a container, such as a metal or plastic can, that has a rim with an integral heat seal zone ( 26 ) and a heat sealable powder or hot melt coating ( 42 ) applied to the heat seal zone ( 26 ) of the upper rim. In another embodiment, the container includes: a sidewall having an upper rim, wherein the upper rim includes an upwardly inclined and integrally formed heat seal zone ( 26 ); a heat sealable coating ( 42 ) applied to the heat seal zone ( 26 ) of the upper rim; and a peelable foil lid ( 30 ) removably attached to the heat seal zone ( 26 ) of the upper rim.
1. A container, comprising:
a metal sidewall having an upper rim and a welded seam extending to the upper rim, wherein the upper rim includes an integrally formed heat seal zone having an upwardly inclined portion with an incline that is steeper than a maximum angle of a foil lid when the foil lid is fully expanded under pressure;
a food-contact polymer coating applied on the upper rim and the sidewall except at the welded seam, such that the food-contact polymer coating has edges adjacent to the welded seam; and
a coating system formed from a heat sealable thermoplastic powder comprising particles having a mean particle size ranging between 20 and 150 microns, which compositionally include an acid-modified polypropylene or a blend of an acid-modified polypropylene with (i) one or more polyester polymers, (ii) one or more epoxy or phenoxy resins, or (iii) blends of (i) and (ii), the coating system including:
a first coating applied to the heat seal zone of the upper rim after the upper rim has been formed, such that the applied first coating covers the food-contact polymer coating at the upper rim;
a second coating applied to the sidewall along the welded seam, such that the applied second coating covers the welded seam and the edges of the food-contact polymer coating.
2. The container of claim 1 , wherein the heat sealable thermoplastic powder comprises, compositionally, the blend of the acid-modified polypropylene with the one or more polyester polymers, and the one or more epoxy or phenoxy resins.
3. The container of claim 1 , wherein the second coating has a thickness of at least 50 microns at the weld seam.
4. The container of claim 1 , wherein the foil lid is a peelable foil lid removably attached to the heat seal zone of the upper rim.
5. The container of claim 4 , wherein the peelable foil lid comprises a layer of polypropylene or modified polypropylene.
6. The container of claim 1 , wherein the food-contact polymer coating comprises an epoxy material.
7. The container of claim 1 , wherein the container is a three-piece can having a bottom end that is attached to the sidewall.
8. The container of claim 1 , wherein the metal sidewall is between about 100 and 200 microns thick and the second coating is applied at a sufficient thickness to bridge the step gap where the metal sidewall overlaps at the welded seam, thereby providing a gentle transition across the step gap.
9. The container of claim 1 , wherein the container further comprises a bottom portion and wherein the bottom of a first container stacks against the top of a second container without damaging the foil lid of the second container.
10. The container of claim 1 , wherein the bottom portion of the upper container of a two-container stacked pair does not rest against the peelable foil lid when the two containers are stacked.
11. The container of claim 1 , wherein the heat seal zone is at least 3 millimeters wide.
12. A method, comprising the steps of:
providing a container body having a sidewall having an upper rim and a welded seam extending to the upper rim, wherein the upper rim includes an integrally formed heat seal zone;
applying an food-contact coating on the upper rim and the sidewall except at the welded seam, such that the food-contact polymer coating has edges adjacent to the welded seam;
applying a heat sealable thermoplastic powder comprising particles having a mean particle size ranging between 20 and 150 microns, which compositionally include an acid-modified polypropylene or a blend of an acid-modified polypropylene with (i) one or more polyester polymers, (ii) one or more epoxy or phenoxy resins, or (iii) blends of (i) and (ii) to at least a portion of the heat seal zone of the upper rim to form a first coating that covers the food-contact coating at the upper rim; and
applying the heat sealable thermoplastic powder to the sidewall along the welded seam to form a second coating that covers the welded seam and the edges of the food-contact polymer coating;
heat sealing a peelable foil lid to the heat seal zone of the upper rim;
deforming the upper rim so as to create an upwardly inclined and integrally formed heat seal zone; and
fully expanding the sealed peelable foil lid, wherein the upwardly inclined and integrally formed heat seal zone is steeper than a maximum angle of the expanded sealed foil lid.
13. The method of claim 12 , wherein the step of applying the heat sealable thermoplastic powder to the sidewall along the welded seam forms the second coating at a sufficient thickness to bridge the step gap where the metal sidewall overlaps at the welded seam, thereby providing a gentle transition across the step gap.
14. The method of claim 12 , wherein the food-contact polymer coating comprises an epoxy material.
15. The method of claim 12 , wherein the heat sealable thermoplastic powder comprises the blend of the acid-modified polypropylene with the one or more polyester polymers, and the one or more epoxy or phenoxy resins.