METHOD OF MAKING AN EASY-OPEN LAMINATED CONTAINER

Abstract: An easy-open container having top and bottom end panels and a body portion, all of laminate construction comprised of an outer layer of stiff material, an intermediate layer of substantially gas-impermeable material, and a continuously sealed thermo­ plastic inner layer. The container's top end panel has a line of weakness in its outer stiff layer defining a tear-out section with opening means such as a tape tab non-critically bonded thereto. In a particularly preferred embodiment, the container is opened by pulling the opening means such that the tear-out section separates from the outer stiff layer along with the substantially coinciding portions of the intermediate layer and the inner layer that are attached thereto, thereby defining a dispensing aperture in the container's top end panel. In a particularly preferred embodiment, the container is provided with easy-open/reclosing means such as a rigid, plug-type member that is used to open and reclose the container. A high-speed manufacturing method for making the present invention is also disclosed.

Description: TECHNICAL FIELD The present invention relates to a method of making laminated containers, and more particularly to a method of forming an easy-open or an easy-open/reclosable laminated container having a substantially rigid outer layer with an aperture or removable section formed therein, a substantially gas-permeable intermediate layer, and a continuously-sealed thermoplastic inner layer. BACKGROUND OF THE INVENTION Easy-open containers are used today to package virtually thousands of products, most notably beverages. An example of a particularly popular easy-opening system, which is commonly referred to as a "tape tab", utilizes a heat sealable strip of tape to seal a pre-cut dispensing aperture in the container's top end panel or lid. Early embodiments of this general concept are disclosed in U.S. Patent 2,870,935 issued to Houghtelling, U.S. Patent 3,186,581 issued to Schneider et al., and U.S. Patent 3,251,515 issued to Henchert et al. Easy-open containers employing the above-described tape tab have thus far met only limited success in the marketplace. A major problem associated with such a system is providing a gas and liquid impermeable seal between the tape and the outer surface of the container's lid. Another serious problem associated with such a system is the exposure of the aperture's raw edges to the product inside the container. One proposed solution to these problems is to cover the dispensing aperture with another discrete tape from the inner surface of the container's lid. An example of this "two-tape" system is disclosed in U.S. Patent 3,339,788 issued to Lipske. While this two-tape system does appear to insulate the aperture's raw edges from the product, the gas and liquid impermeable seal problem is still present, i.e., this critical seal between the tape and the lid is merely moved from the lid's outer surface to the lid's inner surface. Furthermore, the cost of using two discrete tapes is undoubtedly much more expensive than using one. Other examples of this two-tape system are found in U.S. Patent No. 3,355,059 issued to Balocca et al. and U.S. Patent No. 3,990,603 issued to Brochman. Returning to the single tape system, an improved means to obtain the critical seal between the tape and the container's lid has been suggested in U.S. Patent No. 4,116,359 issued to Josephy. According to Josephy, a localized portion of a laminated tape having a bottom plastic layer is first extruded through the lid's aperture. Then, the plastic layer is radially outwardly squeezed around the aperture on the inner surface of the end panel, thereby providing the necessary critical seal. However, in a high-speed manufacturing setting, such a process would be incredibly expensive and slow. In addition, a laminated tape of the type found in Josephy is much more expensive to make than a single layer tape. Another similar proposal to overcome the difficulties associated with utilizing a single tape tab to seal a dispensing aperture is disclosed in U.S. Patent No. 3,338,462 issued to Reynolds et al. The proposal essentially consists of applying a laminated tape tab having a top layer of aluminum and a bottom layer of plastic in overlying relation to the pre-cut aperture, followed by applying heat and an anvil from the bottom surface of the lid to form what is call a "molded-in-situ" plug. When molded, this plastic plug seals the dispensing aperture and also acts as a protective coating around the aperture's exposed metal edges. Although Reynolds' system appears to be capable of sealing the aperture, it is also too complicated and difficult to practice on a high-speed manufacturing level because of the precise registration required between aperture, tape, plastic plug, and anvil. In addition, the laminate tape as described is also relatively expensive to make. A still further improvement to the single tape system for forming a dispensing aperture without the critical seal problem mentioned above is disclosed in Buchner et al, U.S. patent 4,533,063 (corresponding to EP-A-104548, Bosch). This improvement employs a lid which is formed from a laminate comprising a thick carrier layer of thermoplastic material, a middle layer of metal foil and an inner layer of heat sealable plastic. An opening device in the lid has a removable tear-open part surrounded by a weakened line formed solely in the outer carrier layer by a heated indenting tool impressed into the carrier layer. A heat sealable gripping tab is optionally welded to the tear-open part so that the part and the attached portions of the middle and inner layers can be torn out of the lid. Since the weakened line is impressed in the stamp of laminate, this requires precise and exacting equipment and control of the laminate, making it difficult and expensive to perform at high machine rates. Another shortcoming of virtually all of today's easy-open containers is the inability to reclose the container after the initial opening thereof to preserve the container's contents and also to prevent foreign matter from entering the container during storage. In addition, if the container's contents includes suspended solids such as fruit pulp, most easy-open containers cannot be reclosed and shaken to redistribute such solids. An example of an easy-open container that does provide reclosing means is found in U.S. Patent Nos. 4,164,303 and 4,232,797, both issued to Waterbury. These patents disclose several embodiments of an articulated closure element that is hingedly mounted on the container's lid adjacent to a pre-cut dispensing aperture. The closure element has a depending plug or bead on its undersurface that is shaped complementary to the aperture. After the closure element is lifted to initially open the container, the container may be reclosed by returning the closure element back to its original position such that the depending plug or bead engages the dispensing aperture. Although Waterbury's articulated closure element system does allow an easy-open container to be reclosed after initial opening, the system requires a critical seal between the closure element and the container's lid very similar to that associated with tape tab systems as described earlier. Waterbury suggests that this critical seal can be achieved by thermoformation, i.e. applying heat to the lower edge of the thermoplastic closure element to cause the material to flow outwardly underneath the lid surface. Alternatively, Waterbury suggests that the depending plug or bead may be eliminated altogether and a plastic coating applied across the aperture from the lid's inner surface. However, eliminating the plug or bead and using this "inner patch" seal would presumably destroy the ability to reclose the container. In any event, a fair reading of Waterbury suggests that obtaining a critical seal between the closure element and the dispensing aperture is difficult to achieve, particularly if an aseptic seal is initially required. Another problem associated with easy-open containers, particularly those having an upstanding rim about the periphery of the container's top lid, is that a residual amount of product is inevitably trapped between the dispensing aperture and the container's upstanding rim when the container is tipped to dispense the container's contents. When the container is returned to its upright position, this residual tends to spread out over the lid's surface and, during storage, begins to collect dirt and dust. Furthermore if the beverage is sweet such as a fruit juice, the residual attracts insects. Another problem found in most easy-open containers is the failure to use suitable materials that simultaneously provide strength, oxygen impermeability, and protection against flavor loss of the container's contents. In light of the above, it is a principal object of the present invention to facilitate the manufacture of a laminated easy-open container from materials that provide strength, oxygen impermeability, and protection against flavor loss. Another principal object of the present invention is to provide a method of manufacturing and easy-open container with reclosing means. It is another principal object of the present invention to provide a method of manufacturing and easy-open container with a lid configuration that substantially reduces the tendency of the container's contents to spread out over the lid's entire outer surface after a portion of the container's contents have been dispensed. SUMMARY OF THE INVENTION As used in the following summary and detailed description of the present invention, the term "critical seal" or variations thereof is intended to mean a gas and liquid impermeable, hermetic seal. When the term "reseal" or "reclose" is used in describing the container after the initial opening thereof, it is intended to mean only a liquid leak-resistant seal. In addition, the following summary and detailed description are generally directed to a beverage container. However, as will be readily apparent to those skilled in the art, the present invention can be practiced with equal facility in packaging a wide variety of products such as soaps, chemicals, motor oils, powders, granules, foods, and the like. In a particularly preferred embodiment of a container made in accordance with the present invention, the container's top end panel, bottom end panel, and body portion are of laminate construction comprised of an outer layer of stiff or rigid material, an intermediate layer of substantially gas-impermeable material, and an inner sealing layer of thermoplastic material. These layers may be secured either directly to one another, or indirectly to one another by means of one or more additional layers. The container's top and bottom end panels and body portion are preferably made by a high-speed manufacturing process wherein the three above-described layers of material are initially continuous webs that are subsequently laminated together, followed by cutting or stamping individual components from the resultant laminate web. Thereafter, the container's top and bottom end panels are placed on the respective edges of the container's body portion, followed by a sealing operation wherein the points of contact between the three components' inner layer of thermoplastic material are fused together to define a continuously sealed, product-contacting inner surface. For the container's top end panel, it is of particular significance that, in one particularly preferred embodiment, a line of weakness defining a tear-out section is first cut in the web of rigid material before it is laminated to the intermediate and inner webs. Thereafter, easy-opening/reclosing means such as a pull-member having a plug portion is non-critically attached to the outer surface of the tear-out section. "Non-critical" in this sense means that there need not be provided an air-tight or liquid-tight seal between the easy-open means and the tear-out section. "Non-critical" also means that the bond between the two can be achieved by using a common glue or hot melt adhesive, or by using a bonding method that directly fuses the materials together (e.g. induction, high frequency, ultrasonic), none of which require special characteristics such as gas-impermeability. The container is opened by pulling the opening means such that the tear-out section separates along the line of weakness from the outer stiff layer along with substantially coinciding portions of the intermediate layer and the inner layer that are attached thereto, thereby defining a dispensing aperture in the container's top end panel. In another particularly preferred embodiment of the present invention, a discrete aperture is cut in the top end panel's outer web of rigid material before the intermediate and inner webs are laminated thereto. The discrete dispensing aperture exposes a coinciding portion of the intermediate web to which opening means such as a tape tab is attached, again involving a non-critical bond. The container is then assembled as described earlier. The container is opened by pulling the opening means which ruptures and tears the exposed coinciding portion of the intermediate layer along with a coinciding portion of the inner layer that is attached thereto, thereby defining a dispensing aperture in the container's top end panel. In either of the above-described particularly preferred embodiments, an easy-open/reclosing means can be the opening means. An example of an easy-open/reclosing means is a rigid plug comprised of an easily-graspable upper flange having a lower cup formation depending therefrom. The lower cup formation, which is shaped complementary to the dispensing aperture ultimately created when the easy-open/reclosing means is removed from the container's top end panel, is again non-critically bonded to the tear-out section's upper surface or the exposed portion of the intermediate layer, whichever is the case. In the case of the line of weakness defining a tear-out section in the top end panel's outer stiff layer, the container is opened by pulling up on the plug's upper flange which tears the tear-out section from the outer stiff layer and ruptures and tears away substantially corresponding portions of the intermediate and inner layers that are attached thereto, thereby defining a dispensing aperture in the container's top end panel. The container can be reclosed by pressing the plug's lower cup formation back into the dispensing aperture. In another particularly preferred embodiment of the present invention the method is particularly well suited for forming a container having a peripheral rim around the container's top end panel, the container's dispensing aperture is nestled within either a depressed area in the top end panel or surrounded by an upwardly-projecting rib. When the container is tipped to dispense the product therein and returned to its upright position, any residual product trapped between the container's rim and the dispensing aperture is contained within either the depressed area or upwardly-projecting rib and channeled back into the container via the dispensing aperture rather than being allowed to spread out over the container's top end panel. BRIEF DESCRIPTION OF THE DRAWINGS While the specification concludes with claims that particularly point out and distinctly claim the present invention, it is believed that the present invention will be better understood by reading the following description with references made to the following drawings in which: Figure 1 is a perspective view of the top portion of another preferred easy-open container. Figure 2 is an enlarged cross-sectional view of the container shown in Figure 1 taken at a point corresponding to section line 2-2. Figure 3 is an enlarged cross-sectional view of the container shown in Figure 1 taken at a point corresponding to section line 2-2, but shown with the container's tape tab being removed. Figure 4 is a cross-sectional view of a particularly preferred embodiment of the present invention that can be reclosed after the initial opening thereof. Figure 5 is a cross-sectional view of the container shown in Figure 4, but shown showing the container's easy-open/reclosure device removed from the container's top end panel. Figure 6 is a cross-sectional view of the container shown in Figure 4, but shown with the container's easy-open/reclosing device pressed back into the container's dispensing aperture. Figure 7 is a cross-sectional view of another particularly preferred embodiment of the present invention that can also be reclosed after the initial opening thereof. Figure 8 is a cross-sectional view of the container shown in Figure 7, but shown with the container's easy-open/reclose element removed from the container's top end panel. Figure 9 a cross-sectional view of the container shown in Figure 7, but shown with the container's easy-open reclosure device pressed back into the container's dispensing aperture. Figure 10 is a perspective view of the top portion of a particularly preferred top end panel configuration. Figure 11 is an enlarged cross-sectional view of the top end panel shown in Figure 10, taken along section line 11-11. Figure 12 is a perspective view of the top portion of a particularly referred top end panel configuration. Figure 13 is an enlarged cross-sectional view of the top end panel shown in Figure 12, taken along section line 13-13. DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows and easy-open container formed as the result of the present invention and generally indicated as 50 in its initial or unopened condition. In the exemplary embodiment shown, container 50 has a square cross-section with rounded corners. However, as with all other embodiments of the present invention later described and illustrated, container 50 may take on other cross-sectional configurations such as circular, oval, rectangular, or polygonal. Container 50 generally comprises a top end panel 12, a body portion 14, and a bottom end panel 18, all of which are of laminated construction. In Figure 2, top end panel 12 comprises an outer layer of rigid or stiff material 18, an intermediate layer of substantially gas-impermeable material 20 and an inner sealing layer of thermoplastic material 22. The bottom end panel, which is not shown to avoid redundancy, is of the same laminate construction. Rigid layer 18 is preferably made of a material that is sufficiently stiff or rigid to provide strength, such as polyvinylchloride (PVC), polyester (PETP), polystyrene (PS), polypropylene (PP), methacrylate-butadiene-styrene copolymer (MBS) polycarbonate (PC), or paperboard. For intermediate layer 20, examples of materials that meet the definition of "substantially gas-impermeable" are aluminum or other metal foil, metalized substrates (e.g. metalized polypropylene, metalized polyester), or high gas barrier plastics such as ethylene vinyl alcohol (EVAL), polyvinylidenechloride (PVDC), copolymer of acrylonitrile (PAN), polyester (PET), or polyamide (PA). For thermoplastic inner sealing layer 22, which provides protection against flavor loss or contamination, suitable materials include polyethylene (PE), linear low density polyethylene (LLDPE), polypropylene (PP), or polyvinylchloride (PVC). Top end panel 12 and the bottom end panel are preferably made in a high-speed production process wherein an outer web of stiff material, an intermediate web of substantially gas-impermeable material, and an inner web of thermoplastic material are secured together, for example, by a suitable glue or heat sealable thermoplastic, to form the laminate. It will of course be recognized that one or more additional layers could also be secured intermediate the aforementioned three layers without deviating from the scope of the present invention. In making top end panel 12 the web of outer stiff material is first provided with a pre-formed aperture 52 before the intermediate and inner webs are laminated to the outer web. After the laminate web has been made, individual end panels 12 are stamped or cut from their appropriate laminated webs. Preferably, panels 12 are stamped with a die that cuts a series of small notches 26 along the panel's outer periphery, the purpose of which to be described later. Body portion 14 is also of laminate construction and comprises an outer layer of stiff material 28, an intermediate layer of substantially gas-impermeable material 30, and an inner sealing layer of thermoplastic material 32. Body portion 14 is also preferably made in a high-speed process wherein the three layers are initially in web form and secured together by a suitable glue or heat sealable thermoplastic. Outer stiff layer 28 is preferably made of a polyethylene-coated fiber board. Intermediate layer 30 and inner layer 32 can be made of the same materials described for panels 12 and 16. After the three webs of material have been secured together, the resultant laminate is folded into a long tube having a longitudinal seam or butt joint. A laminated seal strip preferably comprised of polyethylene, PET, and polyethylene is then sealed to both the inside and outside surface of the butt joint before individual body portions are cut from the tube. Alternatively, body portion 14 can be made by a high-speed co-extrusion process wherein materials such as PVC, ethylene vinyl alcohol (EVAL), and polyethylene (PE) are co-extruded into a long hollow tube followed by cutting individual body portions from the extruded tube. In the final step in making individual containers containing product, top end panel 12 and the bottom end panel are placed on the ends of body portion 14. Before either the top or bottom end panel is applied and sealed to one end of the body portion, the open-ended container may be sterilized to provide an aseptic environment, followed by filling the container with product from its open end. Thereafter, the remaining end panel is applied to the open end and sealed. The peripheral edges 13 on end panel 12 are folded over the respective edges of body portion 14 such that notches 26 meet and appear to be closed or continuous as illustrated in Figure 1. When panel 12 is properly attached to the end of body portion 14, the joint or interface 34 between inner sealing layer 22 of top panel 12 and the bottom panel, and inner sealing layer 32 of body portion 14 are subjected to localized heating. When sufficiently heated, layers 22 and 32 melt together and, when cooled, bond together such that the filled container 50 now has a continuous, product-contacting inner layer of thermoplastic material. This inner layer not only makes the container liquid tight, but also provides excellent protection against flavor loss of the container's contents. In the case where intermediate layer 20 is a metallic foil, an ultrasonic sealing process can be used to heat and melt interface 34 between layers 22 and 32. Alternatively, the continuously sealed inner layer can be achieved by using an induction sealing process. Preferably aperture 52 is first cut in the web of outer stiff material before the laminate web corresponding to layers 18, 20, and 22 is formed, thereby exposing a portion 54 of intermediate layer 20. Either before or after discrete top end panels are stamped from the laminate web, tape tab 42 is secured directly to the exposed portion 54 of intermediate layer 20, again by using a non-critical layer of glue or hotmelt adhesive 46, or by using a bonding method that directly fuses the materials together (e.g. induction, high frequency, ultrasonic), all of which involve a non-critical bonding operation. As shown in Figure 3, container 50 is opened by pulling easily-graspable section 43 of tab 42 such that exposed portion 54 of layer 20 and a substantially corresponding portion 22' of layer 22 rupture and separate from their respective layers, thereby creating tearout section 49 and defining a dispensing aperture 56 in top end panel 12. Container 50 can then be tipped to dispense the contents therein. Figures 4-6 illustrate the top portion of a particularly preferred easy-open top end panel that can also be reclosed. The laminated container 60, which is also constructed according to the earlier-described web laminating process, has a laminated end panel 12 that is similar to that shown in Figures 1-3. In this embodiment, however, a rigid plug 62 comprised of an easily-graspable upper flange 64 having a lower cup formation 66 depending therefrom is secured by a non-critical layer of glue or hotmelt adhesive 46 (or by a direct bonding method as previously described) to the outer surface of removable section 45 defined by a line of weakness 44 in outer stiff layer 12. Lower cup formation 66 is shaped complementary to the dispensing aperture that will be created when container 60 is opened as will be described later. If desired, plug 62 can be secured to the top of the container to prevent its becoming lost after opening, e.g., as by a hinge or strap (not shown). Since plug 62 is not initially responsible for sealing container 60, it can be made from common materials not having special properties such as gas impermeability. For example, plug 62 can simply be made from thermoformed or injection molded polyethylene or polystyrene. As shown in Figure 5, container 60 is initially opened by grasping and pulling up on the plug's upper flange 64 such that removable section 45 separates from stiff layer 12 along line of weakness 44. In the process, substantially corresponding portions 20' and 22' rupture and separate from their respective layers 20 and 22, thereby forming a tearout section 49' and defining a dispensing aperture 68 in top end panel 12. As shown in Figure 6, container 60 may be reclosed after a portion of the container's contents have been dispensed by pressing lower cup formation 66 of plug 62 with attached layer portions 45, 20', and 22' back into dispensing aperture 68. Since lower cup formation 66 is shaped complementary to aperture 52, the interference or friction fit therebetween provides a liquid tight seal that prevents foreign matter from entering the container during storage and also allows container 60 to be shaken if desired. Referring now to Figures 7·9, Figure 7 illustrates the top portion of another particularly preferred laminate container generally indicated as 70. Container 70 is also an easy-open/reclosable container that uses a plug 62 as a means to initially open and subsequently reclose the container. As shown in Figure 7, aperture 72 is first cut in the web of outer stiff material before the laminate web comprised of layers 18, 20, and 22 is formed, thereby exposing a portion 54 of intermediate layer 20. Either before or after discrete top end panels are stamped from the laminate web, lower cup formation 66 of plug 62 is attached to exposed portion 54 of intermediate layer 20, again by a non-critical layer of glue or hotmelt adhesive 46, or by using a direct bonding method as earlier described, all of which involve a non-critical bonding operation. As shown in Figure 8, container 70 is initially opened by grasping and pulling up on upper flange 64 such that exposed portion 54 of intermediate layer 20 and substantially corresponding portion 22' of inner layer 20 rupture and separate from their respective layers, thereby creating and defining a dispensing aperture 74 in top end panel 12 by removal of tearout section 49''. As shown in Figure 9, container 70 may be reclosed after a portion of the container's contents have been dispensed by pressing lower cup formation 66 of plug 62 with attached layer portions 54' and 22' back into dispensing aperture 68. Again, since lower cup formation is shaped complementary to dispensing aperture 74 in top end panel 12, the interference fit therebetween provides a liquid tight seal that prevents foreign matter from entering the container during storage and also allows container 70 to be shaken if desired. As with the embodiment of Figures 4-6, plug 62 can be secured to the top of the container to prevent its becoming lost after opening, e.g., as by a hinge or strap (not shown). Figures 10 and 12 with their respective cross-sectional views 11 and 13 show particularly preferred embodiments of two exemplary lid constructions that can be used in preparing any of the earlier described embodiments of containers made in accordance with the present invention. The added feature found in the top end panels illustrated in Figures 10 and 12 is particularly well suited for a container having an upstanding rim running about the periphery of the container's top end panel. In Figures 10 and 11, the die that is used to stamp top end panel 82 from the earlier-described laminated web forms a depressed area 84 that surrounds the pre-cut aperture (or line of weakness, whichever is the case) found in top end panel 82. Since the lid stamping takes place after the lamination process, depressed area 84 extends through all layers of the laminate, as can be seen in Figure 11. When container 80 is tipped to dispense the product therein, any residual product trapped between rim 86 and dispensing aperture 88 is channeled back into the container via aperture 88 when the container is returned to its upright position rather than spreading out over the outer surface of the top panel 82. In Figures 12 and 13, the die that is used to stamp top end panel 92 from the earlier-described laminated web forms an upwardly-projecting rib 94 that substantially surrounds the pre-cut aperture (or line of weakness, whichever is the case) found in top end panel 92. When container 90 is tipped to dispense the product therein, any residual product trapped between the container's upstanding rim 96 and dispensing aperture 98 is contained within the confines of rib 94 when container 90 is returned to its upright position rather than spreading out over the outer surface of top panel 92.

Claims: The method of forming a substantially gas-impermeable easy-open container (50) having a continuously sealed thermoplastic product-contacting inner surface prior to opening, said container (50) having a laminated top end panel (12), having a substantially rigid outer layer (18), a substantially gas-impermeable intermediate layer (20) bonded to said outer layer (18) and a thermoplastic inner layer (22) bonded to said intermediate layer (20), said container also having easy-opening means provided on said laminated top end panel (12) which employs a pull member adapted to remove a tear-out section (49,49') from said top end panel (12) to form a dispensing aperture (56), said method being characterized by the step of forming an opening (52) or, optionally, defining a removable section (45) by an endless line of weakening (44), in the rigid outer layer (18) of the top end panel (12) prior to bonding the outer layer (18) to the intermediate layer (20). The method according to Claim 1 characterized by the step of fastening said pull member to an exposed portion (54) of intermediate layer (20) underlying the opening (52) in the rigid outer layer (18). The method according to Claim 1 characterized by the step of fastening said pull member to the outer surface of the removable section (45) defined in the rigid outer layer (18). The method according to any one of Claims 1-3 characterized by the step of forming, in the laminated top end panel (12), a depressed area (84) or, optionally, an embossed upwardly projecting rib (94) surrounding the region of top end panel (12) through which the dispensing aperture (56) will extend. The method according to any one of the Claims 1-4 characterized in that the pull member is a tape tab (42). The method according to any one of the Claims 1-4 characterized in that the pull member comprises a plug portion (62) which is sized and configured to reclose said dispensing aperture (56).

Inventors: DEFLANDER, JOSEPH FERNAND
Applicants: THE PROCTER & GAMBLE COMPANY
Application year: 1986
Main classification: B65D17
IPC codes: B65D17