WO1991018795A2

WO1991018795A2 - Easy-open containers

Info

Publication number: WO1991018795A2
Application number: PCT/US1991/003568
Authority: WO
Inventors: Christopher J. Farrell; Robert J. Mchenry
Original assignee: American National Can Company
Priority date: 1990-06-06
Filing date: 1991-05-20
Publication date: 1991-12-12
Also published as: WO1991018795A3

Abstract

An easy open feature is provided to containers by selectively scoring the outer and inner surfaces of sidewalls of the container, providing the sidewalls with internal weakness, and by providing means to effectuate opening at an area between scores on said outer surfaces. Disclosed are such easy-open containers and methods and apparatus for making them.

Description

EASY-OPEN CONTAINERS This invention relates to containers especially from multilayer materials, including at least one layer of a barrier material. Such containers, for instance can be generally cylindrical or bowl-shaped containers from blow-molding or injection blow molding. This invention further relates to means for opening such containers. In addition, this invention relates to methods of and apparatus for manufacturing easy-open containers.

BACKGROUND OF THE INVENTION

As background, reference is made to:

U.S. Patent No. Patentee

1,839,990 O'Neil 2,355,108 Reese

2,490,888 Sebell

2,998,158 Tupper

3,409,167 Blanchard

3,409,206 Slouka et al 3,502,257 Virros

3,557,998 Collie

3,572,579 Mueller

3,615,034 Lemelson

3,753,847 Gayner et al 3,997,677 Hirsch et al

4,037,748 Stubbs

4,125,632 Vosti

4,207,989 Ingemann 4,252,248 Obrist

4,265,367 Vogt

4,332,332 Ingemann

4,333,585 Del Bon

4,461,420 Horvath 4,474,304 Jacobs

4,556,152 Bogren

Aerosol Gaskets, Aerosol Age, Dec. 1982, p.26.

The U.S. Patents relate to containers or means for opening them. The Aerosol Gaskets reference relates to gaskets; but, this article employs gaskets for a different purpose than the gaskets employed herein such that this reference, while known of and disclosed herein, is considered non-analogous.

Of the above-listed U.S. Patents, Del Bon, U.S. Patent No. 4,333,585 relates to fibre containers and provides no teaching or suggestion of multilayer containers, the advantages of scored oriented polypropylene or the like, or of a "buried" weakness line between lamina of the sidewall of a container. Slouka et al, U.S. Patent No. 3,409,206 also relates to a fibre body, and fails to teach or suggest plastic laminates, ways to overcome problems concerning internal barrier materials, or solutions therefor employing an external or internal collar.

Virros, U.S. Patent No. 3,502,257 relates to opposite wall scores on a fibrous container which merely has a double thickness at the manufacturer's lap. There is no teaching or suggestion of multilayer containers, triple scores in a multilayer container, the problems of barrier materials, or the solutions herein therefor.

O'Neil, U.S. Patent No. 1,839,990, relates to the metal can art wherein deep skirts are provided and the multilayer metal sidewall is conventionally scored. U.S.

Patents Nos. 2,490,888 (Sebell) and 2,355,108 (Reese) are similar.

The Ingemann U.S. Patents Nos.4,332,332 and 4,207,989 relate to non-multilayer plastic containers.

Again, it is noted that documents such as these fail to teach or suggest multilayer containers, triple-scoring, or the problems of barrier materials and the solutions therefor provided herein. Horvath, U.S. Patent No. 4,461,420 relates to providing internal wall weakening only to permit manual tearing of a vent and fails to teach or suggest circumferential or continuous sidewall scoring and in-lamina weakness as provided herein. Prom this review of background documents, it is evident that the use of triple scores to provide a means for opening a multilayer container, preferably of polymeric materials, and the solutions to the problems of barrier materials, particularly of scoring and restoring the same, as disclosed and claimed herein, have not heretofore been c taught or suggested.

Providing a means for opening a container easily is highly desired because previous containers either failed to be easy-opening or provided a pull-off top; the latter being difficult to manufacture and difficult to use by

•J_^Q consumers. If the container failed to be easy-opening, the end user of the contents in the container had to resort to using a sharp instrument to open such a previous container, e.g., a can opener. If the previous container had a pull-open or pull-off top, consumers might spill contents of

-_jc the container in manipulating such a top off the container, or might cut themselves on a sharp edge of the top once it is removed.

It is therefore an object of this invention to provide an easy opening multilayer container, and to 2_Q overcome problems relating to barrier materials when easy open features are provided in a multilayer container.

SUMMARY OF THE INVENTION

It has now been surprisingly discovered that an easy open feature is provided to a container by selectively ₂₅ scoring outer and inner surfaces of sidewalls of the container and providing means to pull at an area between the scores.

The present invention provides an easy open container comprising a body having sidewalls, at least said sidewalls being comprised of a structure having an internal weakness, said sidewalls having an inner surface, an outer surface, an upper portion, and height, wherein, at said upper portion is an easy open feature, said easy open feature comprising: a first score on said outer surface of each sidewall and extending inwardly to the internal weakness, a second score positioned below said first score and on said outer surface of each sidewall and extending inwardly to the internal weakness, a third score positioned between said first and said second scores and on said inner surface and extending outwardly , and means on said outer surface at an area between said first and said second scores to effectuate opening of the container.

In an embodiment, the third score extends outwardly to the internal weakness. The "internal weakness" can be from the structure being a multilayer structure and an internal layer is capable of delamination. The internal weakness in a multilayer structure can be a variation in mechanical properties across width leading to lines of ^"weakness. The internal weakness can be a line of mechanical weakness in the structure. The structure can be a laminate, a multilayer structure, a composite, a metal laminate, a multilayer structure comprising polymeric material and having a metal layer, a multilayer structure comprising polymeric material wherein at least one internal layer is comprised of polymeric barrier material (in which case the internal layer can provide the weakness, e.g., by being capable of delamination and the roots of the scores are sufficiently near to and/or within this internal barrier layer) , or the like. The line of mechanical weakness or internal weakness can also be from creating sufficient orientation. The means to effectuate opening can be sufficient pull means which allows a fissure to be created among the roots of the scores in the area of internal weakness. The internal weakness is preferably between the first and second scores. The scores can be continuous or disconti- nuous, e. -, formed from a series of scores or cuts, or the like, or where the tearstrip remains on the closure.

If desired, reinforcement of barrier properties comprising an internal or an external collar and/or an internal or an external gasket, or combinations thereof is provided. It is also preferred that the container be generally cylindrical or bowl-shaped, although the shape of the container is not a limitation of the invention. The

sidewalls can be substantially parallel. The container can have generally vertical sidewalls. The container can also have generally vertical top and/or bottom walls. Note that terms such as "generally parallel", "generally vertical", and "generally horizontal" are further defined herein.

The present invention also provides methods of and apparatus for manufacturing such containers.

BRIEF DESCRIPTION OF DRAWINGS

Figs. 1A-1C shows a cross-section of a wall of a container of the invention with three scores.

Fig. 2 shows a cross-section of a wall of a container of the invention with the effect upon opening of the three scores illustrated.

Fig. 3 shows a cross-section of a wall of a container of the invention.

Fig. 4 shows a cross-section of a wall of the invention with an external collar or gasket.

Fig. 4A shows the cross-section as shown in Fig. 4, except that the collar is a multilayer material. Fig. 5 and Figs. 5B and 5C show a cross-section of a wall of the invention with an internal collar and with an internal collar and gasket, respectively.

Fig. 5A shows the cross-section as shown in Fig. 5 or 5B or 5C, except that the collar or gasket is a multilayer material.

Figs. 6A-6F show a container of the invention having applied thereto an external collar which is a tearstrip, and the tearstrip or collar.

Figs. 7A-7C show another container of the invention having applied thereto an external collar which is a tearstrip. 5 Fig. 8 shows an apparatus for applying a tab to a container of the invention.

Fig. 9 shows a collar or tearstrip for a container of the invention.

Figs. 10-11A show views of a container and 0 cup-like collar top of the invention.

Figs. 12 shows an embodiment of the scores of the invention and how these scores come about during manufacture.

DETAILED DESCRIPTION -_jc Containers from various materials, including from multilayer materials are known as are methods of producing them. For instance, a film of a suitable multilayer material can be blow molded, e.g., injection blow molded, into a multilayered injection blow molded container. The 20 resultant container can be rigid or semi-rigid, and generally of any desired shape, preferably generally cylindrical. Surprisingly, such a container can be provided with an easy-open feature by providing a plurality of score lines and internal weakness in the walls and by attaching 25 thereto means to effectuate opening such as sufficient pull between the scores. Containers of this invention can also be produced by thermoforming.

Suitable constituents for layers of multilayer materials for container of this invention include almost any materials conventionally used in the art, e.g., ethylene vinyl alcohol (EVOH) , vinylidene chloride copolymers, poly¬ ethylene (PE) , medium density polyethylene (MDPE) , high density polyethylene (HDPE) , low density polyethylene (LDPE) , linear low density polyethylene (LLDPE) , very low density polyethylene (VLDPE) , polypropylene (PP) , ultra low density polyethylene (ULDPE) , propylene ethylene copolymer (PPE) , nylon, high impact polystyrene (HIPS) , ethylene butene copolymers (EB) , polyethylene terephthalate (PET) , copolymers of PET or CoPET, polybutylene terephthalate (PBT) , copolymers of PBT or CoPBT, MXD6, or ethylene vinyl alcohol (EVA) (in which case, preferably a high VA content EVA, i.e., about 28-35% by weight by weight VA EVA) , or the like, or mixtures thereof.

In multilayer structures a tie or an adhesive may also be present between the layers. Suitable materials for such tie layers or adhesives are known to the ordinary skilled artisan and may include, by way of example, anhydride modified polyolefins (e.g., graft copolymer of aleic anhydride and propylene wherein maleic anhydride moieties are grafted on to polypropylene chains) , ethylene acrylic acid (EAA) copolymers, ethylene methyl acrylate copolymers, blends or copolymers of PP and EVA, or other synthetic resinous materials. The selected adhesive should be stable under the conditions the containers of the invention are prepared or used. For additional information on adhesives, reference is made to commonly owned U.S. Patent Application Serial No. 07/458,489, filed December 28, 1989, (incorporated herein by reference) . Commercially available products for layers in products for layers in products of the invention include nylon 6; 11; 12; 6, 12; and 6, 66; ULTRAMIDKR 4600 (BASF), NOVAMID 2030 (Mitsubishi Chem. Co.) DURATHANE (Farbenfabriken Bayer A.G.), "1030" (Unitika, Japan), ZYTEL SUPERTUFF 811 (Du Pont), "4018" (Huels, Germany), and ELY 1256 (Elmser, Switzerland) , Mylar, Dalar, Exxon 5610A-2 (blend of PP containing EVA) , Admer (Mitsui, No. AT469C) , Bynel (Du Pont E361 or 3036), Plexar 3342, and Surlyn (Du Pont) . Admer, Bynel and Plexar are believed to be maleic anhydride modified polyolefins.

Vinylidene chloride copolymers as mentioned herein include vinylidene chloride vinyl chloride copolymers (VC,

HB Sarans, Dow Chemical Co.), and vinylidene chloride methyl acrylate copolymers (MA Saran, Dow 119, Dow Chemical Co.; MA-PVdC copolymers containing essentially no EVA, U.S. application Serial No. 07/458,484, filed December 28, 1989 and incorporated herein by reference) . As to polyvinylidene chloride films and methods of making and using them. ι l

attention is further directed to commonly owned U.S. Patent applications Serial Nos. 07/458,485, 07/458,489, and 07/458,490, all filed on December 28, 1989, and each incorporated herein by reference. In vinylidene chloride methyl acrylate copolymers, the methyl acrylate is preferably present in an amount of about 3 to 8% by weight, more preferably from 6 to 8% by weight, based upon total weight. However, the methyl acrylate content can be up to 12% and even up to 15% in some instances. Vinylidene chloride copolymers and EVOH are useful for comprising the internal layer of a barrier material in the containers of this invention. The term "internal layer" as used herein means that the layer is between two or more layers and is not a surface layer. The nature and number of different layers in containers according to this invention are not critical since the advantages of this invention can be realized for containers made of other plastic materials, as well as those having three, five or more layers. A typical structure for a container is: (outer) PP, or blend of PP and HDPE/Adhesive/Barrier, e.g., EVOH, VC, HB Sarans,

MA Saran or MA-PVdC containing essentially no EVA/Adhesive/

PP, or blend of PP and HDPE (inner) . The PP or blend of PP in the outer, the inner or both the inner and outer layers can be oriented; and, in a preferred embodiment these layers are oriented to achieve lines of orientation weakness.

Layered structures, films or laminates which can be formed into containers can be formed by any suitable A process, including laminations, extrusions, coextrusion, blown extrusion, tubular water quench extrusion, extrusion coating, and the like, and combinations thereof. Likewise, the present invention is applicable to any process and apparatus for forming a container, so long as the scores, the internal weakness and means for effectuating opening (e.g., sufficient pulling) thereat can be applied to the container.

As to extrusion or co-extrusion methods and apparatus for making multiple layer sheet materials, reference is made to commonly owned U.S. Patent application Serial Nos. 07/458,486, 07/458,487 and 07/458,488, all filed on December 28, 1989, and each incorporated herein by reference. And, as to blended film structures, reference is made to commonly owned U.S. Patent application No.

07/458,489, filed December 28, 1989 and incorporated herein by reference. For further background on films, containers and methods and apparatus for producing them, reference is made to U.S. Patent Nos. 3,477,099, 4,755,402, 3,558,330, 4,714,638, 4,842,791, 4,667,454, 4,526,821, 4,745,013, 4,554,190, 4,379,117,and 4,804,510 each of which being incorporated herein by reference.

Furthermore, multilayer structures, laminates or films, or layers thereof, in this invention, may be oriented, if desired, e.g., for a particular end use or to create the internal weakness, by processes such as blown tubular orientation, stretch orientation, or molecular I2> orientation. For instance, to create the internal weakness, an internal layer can be highly oriented. In a preferred embodiment the neck of a container is oriented by injecting hot plastic into a thin cold mold. They may also be cross-linked by conventional processes such as by irradiation, heat, or the addition of cross-linking agents.

The containers in this invention are useful for packaging food, for instance prepared food which is ready for microwave-reheating by the consumer. However, the contents of the container are not to be considered a limitation of this invention. Note that if a container is to be used for food, drugs or cosmetics, its constituents should meet FDA approval.

Containers of this invention are also useful for retorting, although specific uses for the containers are not to be considered a limitation of this invention. Retorting is a process wherein a sealed container (usually filled with food, medical supplies, blood, etc.) is heated for a sufficient time and at a sufficient temperature to achieve commercial sterilization (see Title 21, C.F.R.,. Part 113, Definitions, §113.3), e.g., by heating with heated or boiling water, steam, heated steam or pressurized water or steam at a temperature of about 212-275°F for a sufficient time, typically from about _ hour up to an hour, usually less than an hour, at a sufficient pressure. And, the heating of contents of containers of this invention can also be achieved in microwave pasteurization. The contents and

the amounts thereof in the container can be factors in the times and temperatures of heating.

Furthermore, herein the terms "generally horizontal", "generally vertical", "generally cylindrical" and "generally parallel" are used. It is noted that the sidewalls of containers of this invention need not be perfectly or exactly vertical or parallel: they can slope outwardly or inwardly from bottom to top. It is noted that the top and bottom walls of containers of this invention need not be perfectly or exactly horizontal: they too can slope or have indentations extending inwardly or outwardly. It is further noted that the shape of the container is not to be considered a limitation of this invention. Containers of this invention can be of any desired shape, e.g., generally cylindrical, generally rectangular (with angled or curved edges) , generally box (with angled or curved edges) , bowl or tub shaped, or the like. If a container is described herein as "generally cylindrical," it is to be noted that such containers according to this invention need not be perfect or exact right cylinders: they can have a greater radius at an upper portion than the radius at a lower portion; they can have a greater radius at a lower portion than the radius at an upper portion; the bottom or top walls may not be perfectly flat, but may extend inwardly or outwardly; and, the sidewall, either inner or outer, may not be perfectly IS flat, but may have variations or, can have for instance, a collar or gasket or tab, attached thereto.

Referring now to the Figures, Figs. 1A-3 illustrate a cross-section of the sidewall of container 70 of this invention; and, more generally, illustrate a concept of this invention. Outer surface 10 is provided with a first score S₁ and a second score S₂. Score S_. is positioned higher than score S_. Inner surface 20 is provided with a third score S- which is positioned heightwise between scores S.. and S₂. To open the wall of container 70 and ergo container 70 a fissure preferably occurs between the root or deepest part of score S, and the root of score S_? in such a way that it connects with the root of S-.. When this occurs, there are three pieces, instead of one, and the wall (and ergo the container) is opened (Fig. 2) . Line A-A is a joining line of weakness in the wall of container 70. Line A-A permits the aforementioned fissure between S, and S₂ which connects with S,. Note that in certain instances stresses at such cracks are maximized away from the root tip.

Line A-A can be created during the manufacture of the container, for example, by either (a) creating enough orientation in the direction of A-A, or (b) employing buried or internal layers in the direction of A-A which have either (c) low cohesive strength or (d) poor adhesion with adjacent layers in the plane of A-A. If scores S^ , S₂ and S₃ and line A-A are accordingly provided, and a means on said outer surface to pull at the area between the first and second score so as to effectuate opening of the container is also provided, e.g., a pull tab or the like adhered or affixed to outer wall 10 between S, and S_? which causes a fissure to occur between the roots of S₁ and S₂ which connects with the root of S_ upon pulling, the container thus has what comprises an easy-open feature: The end user pulls at the tab which causes a fissure to occur between the roots of S- and S₂ which connects with the root of S_ and the container opens as piece 25 is removed circumferentially (or for the full 360°). Height 5 can be any suitable dimension, e.g., 0.05 to 0.5 inches, typically 0.1 to 0.5 inches. The depth of the scores can be from about 20% to about 80% of the thickness of the wall with S, approx. equal to S₂ and S, greater than or equal to S,. Note that line A-A need not be a straight line (See Figs. IB, 1C) .

In Fig. 3, layer 30 represents an internal barrier layer such as a layer of EVOH or polyvinylidene chloride copolymer situated between layers 12 and 15. Scores S, and S_ cut into layer 30. Score S_, in this illustrated embodiment does not cut into layer 30, and it is not preferred to have S- also cut into this layer, but, this invention includes containers in which score S_ also cuts into the barrier layer.

While penetration of the internal barrier layer can provide an easier opening, it also means that the integrity of the barrier has been violated. This means that oxygen and moisture can enter into the container and that if n the container is subjected to retorting, EVOH or adhesive may ooze out during the retorting; and, the adhesive layers (s) may be weakened.

From the Example and Table 1 below a double scored container can be twice as permeable prior to retorting than a single scored container. The single scored container prior to retorting can be about 50 times more permeable than the container with no scores. The double scored container can be about 100 times more permeable than the container with no scores. Retorting can increase the permeability of the double scored container, but not by very much. A protective collar allows some self-sealing to occur during retorting, halving the impact of scoring to a permeability after retorting which can be only a factor of 3 increase over the non-scored container.

Thus, to improve the barrier features of the layers of the container after scoring in accordance herewith, the present invention also provides for external or internal patch strips, collars or gaskets or a combination thereof to be applied to the container to improve or decrease permeability. A flexible collar may be referred to herein as a gasket.

Fig. 4 shows an external collar or gasket 40. Collar 40 can be from aluminum foil, sprayed epoxy, an olefin such as an olefin shrink band, a plastic shrink wrap such as a poly- vinylidene chloride copolymer, e.g., a I .

copolymer of polyvinyl chloride and polyvinylidene chloride, latex, saran latex, a nylon such as a solution of nylon, EVOH such as EVOH in water/propanol sprayed thereon, or the like or combinations thereof. In this instance it is desirable to attach a tab to collar 40 so that the necessary fissure for opening can be made upon pulling the tab.

Fig. 4A shows that patch strip or collar 40 can be from a multilayered material wherein layer 40A can be adhesive so that collar 40 adheres to outer surface 10, layer 40B can be from a barrier material, and layer 40C can be from any suitable materials for an outer surface of a film. Alternatively, each of layers 40A, 40B and 40C can themselves be multilayer structures.

Fig. 5 shows collar 50 against inner surface 20 of container 70. Collar 50 can be of any suitable material, e.g., metal such as aluminum, PP (such as thermoplastic PP) or a blend thereof, mineral filled nylon, or a multilayer structure (see Fig. 5A) ; and, collar 50 can have a gasket associated with it (See Fig. 5B) . A hot roller or R/F heating can be employed to assure contact between inner surface 20 and collar 50. Further, collar 50 can take the form of a shallow cup which is inserted into container 70; and if collar 50 is a rigid or semi-rigid cup, it can, in general, be of metal or plastic, e.g., a thermoplastic. Indeed, as depicted in Fig. 5 collar 50 is cup like. The internal collar of this invention can also take the form of a stand-alone flexible collar (gasket) adhered to the inside surface of the container (not shown) ; however, the stand-alone collar embodiment may not be commercially practicable and is therefore not presently preferred.

In Fig. 5, height 60 shows the depth of collar 50 5 from base 51 thereof to the uppermost portion of container 70. The neck of container 70 can be molded to be just slightly smaller in diameter than the profile of collar 50 so that collar 50 must be forced into the neck of container 70, against inner surface 20. This can be done in 10 a separate plugging machine situated in-line. Oxygen protection is afforded by collar 50 by the press-fit or close contact between collar 50 and surface 20. Further, because collar 50 fits deeply into container 70, the path for oxygen to reach the contents of the container is very --^■ great such that oxygen protection is also provided by path length. Container 70 can be provided with shelf 55.

Fig. 5B depicts an embodiment wherein gasket 52 is provided between surface 20 and collar 50. Gasket 52 can be of any suitable material, e.g., a barrier material such as a 20 polyvinylidene copolymer, EVOH, a rubber, or a structure containing rubber, or a multilayer structure. Likewise, with respect to Fig. 4, between collar 40 and surface 10, a gasket can be placed, e.g., if additional barrier properties are desired. Fig. 5C shows a preferred embodiment when 5■. gasket 52 is provided between surface 20 and collar 50. In this embodiment of Fig. 5C, gasket 52 extends downwards, to as near to base 51 as possible, i.e., for the distance of height 65, so as to afford good oxygen barrier protection by providing a long oxygen path length.

Returning to Fig. 5, because collar 50 fits so deeply down inside the neck of container 70, below scores S- S₂ and S₃ (the area between scores S- and S_, including score S^ being referred to as "tearstrip") , after the tearstrip is removed, container 70 is resealable using the collar 50, particularly if it is in the form of a cup. Height 65 illustrates the depth of collar 50, below the tearstrip. Height 65 represents the aforementioned oxygen path length and can be .15-.20 inches. If collar 50 is of metal, container 70 will not be efficiently microwaveable with collar 50 therein.

If container 70 has a plastic overcap and a metal collar, and is filled with food to be reheated in a microwave oven, the end user removes the overcap, pulls at a tab (not shown in Fig. 5) attached between scores S.. and S« to remove the tearstrip, removes metal collar 50, replaces the overcap if necessary for heating and microwave heats the contents accordingly. When the heating is completed, the overcap is removed if it was in place for heating and the contents used. If there are leftovers, container 70 is reclosed by replacing the overcap.

If reliance is on a press-fit of collar 50 against surface 20, it is essential to maintain close contact between surface 20 and collar 50. If collar 50 is of metal R/F heating can further promote close contact between surface 20 and collar 50. Note also that if collar 50 is made of metal, and reliance is placed solely on a press-fit, dents or deformation in the metal can cause oxygen paths to open between the tearstrip and the contents of the container.

Fig. 5A illustrates collar 50 as a multilayer structure. Gasket 52 (Fig. 5B) can also be a multilayer structure. Thus, Fig. 5A has reference numerals with respect to both collar 50 and gasket 52. Layer 50A (52A) can be from a barrier material such as EVOH, layer 50B (52B)can be an adhesive, and layer 50C (52C) can be a thermoplastic rubber or PP or a PP blend (e.g., with HDPE). However, with respect to collar 50 (and/or gasket 52 if it is present with or without collar 50) , it is preferred that at least one layer thereof be of rubber. Again, R/F heating can be employed to assure appropriate surface contact between collar 50 (if of metal) and surface 20. However, excessive adhesion between collar 50 and surface 20, e.g., which would prevent the opening of container 70 is undesired. For instance, R/F heating aluminum against EAA may result in undesired excessive adhesion whereas aluminum against PP does not result in undesired adhesion. The skilled artisan, without undue experimentation can determine which materials will have excessive adhesion to each other. If a plastic or non-metal cup-like collar 50 is provided within container 70, and container 70 is filled _'with food to be microwave heated, collar 50 can be the top * s-

for container 70 (See Figs. 10-11A) and the end user can pull at a tab attached between scores S_. and S to remove the tearstrip, and heat accordingly in the microwave oven. The microwave heating causes the top of container 70 and collar 50 to pop-up if the sidewalls of container 70 have an incline. After heating, the top of container 70 and collar 50 are removed; the contents used; and, if there are left¬ overs, container 70 is reclosed by replacing the top.

Jumping ahead for a moment to Fig. 10-11A, Fig. 10 shows container 70 with pull tab 310, and scores S, and S„ (Score S₃ is present but not visible because it is inside container 70) . Note that the bottom of container 70 has an indentation (dotted line. Fig. 10) . Fig. 10A shows an overview of container 70, looking down on it (A-A). Fig. 10B is a cross-section of container 70, along line C-C. Cap

350 (Fig. 11) fits within opening 340 of container 70 with surface 330 of cap 350 abutting against surface 320 of container 70. Cap 350 is a "cup-like form" for collar 50 shown in Fig. 5. Cap 350 is deep enough to fit within container 70, below scores S,, S₂ and S_~ . Surfaces 320 and

330 can be heat-sealed together, preferably at the outer perimeter. Cap 350 and container 70 are preferably both of plastic and can be manufactured by thermofor ing, or injection molding. Surfaces 320 and 330 can be suitable materials to adhere to each other by heat- sealing, but without undesired excessive adhesion. Fig. 11A shows an enlargement of the area A of Fig. 11. ^

If container 70 as shown in Figs. 10 to IOC is capped with cap 350 as shown in Figs. 11 and 11A, and filled with food to be microwave reheated, the end user only need open by pulling at pull tab 310; microwave heat; and, use the contents. If there are leftovers, cap 350 can be used to reseal container 70. The structure of container 70 and cap 350 as shown in Fig. 10 to 11A is presently preferred. Figs. 6A-6D show the application of an overstrip which can also be an external collar (as shown in Figs. 4 and 4A) . The overstrip provides a tab or means to pull at the area between scores S.. and S~ . Figs. 6E-6F show the overstrip.

Fig. 6A shows container 70 having scores S_. , S^ and S₃ (Score S₃ not shown as it is within container 70) . In Fig. 6B, imaginary vertical axis 75 is shown. Line 80 is the radius (r) of container 70 at the tearstrip area. Container 70 has been provided with vertical punch 85. Overstrip 90, as shown in Fig. 6E is formed so that portion 95 of it is as wide as area between scores S.. and S₂ so that that portion 95 can be placed over this area in proximity to punch 85 as shown in Fig. 6C. Arrow 93 indicates the rotation required to wrap overwrap 90 onto container 70. Note that in this embodiment portion 110 of overwrap 90 is preferably wider than the area between scores S, and S₂• Fig. 6D shows overwrap 90 applied to container 70 with tab - 105. Length 100 is the length of tab 105. If length 100 is "x"; the length of portion 95 is "d", then the sum of the length of portions 95 and 110 is (2(pi)r)+x+d. -~t

Fig. 6F shows a cross-section of overstrip 90. Layer 115 is preferably aluminum and/or a multilayer structure preferably having a layer of an oxygen barrier material. Additional layers can be over layer 115. Layer 115 represents the outer layer of overstrip 90. Layer 120 is a material with peelable adhesion to outer surface 10, e.g., if outer surface 10 is from PE or PP, then layer portion 120 can have peelable adhesion to PE or PP, such as peelable lidstock. Layer portion 121 must be of a material with strong adhesion to the outer surface 10.

With respect to adhesive materials for layers such as layer portion 120 and layer portion 121, in addition to the aforementioned adhesives, reference is made to commonly owned and pending U.S. application Serial No. 07/458,489, incorporated herein by reference, which relates to sealant blends, e.g., of: polyethylene-based polymers, ethylene- methyl acrylate copolymers and polybutylene, for peelable sealant blends; polyethylene-based polymers and polybutylene for peelable sealant blends when very low temperature sealing is not required; ethylene-methyl acrylate copolymer and polybutylene, for peelable sealant blends when having excellent hot tack is unimportant; and polyethylene-based polymers and methyl acrylate for non-peelable sealant blends which seal with good hot tack. Surlyn is an ionomer blend which is also employed as a sealant. To open container 70 as shown in Fig. 6D, the end user pulls at tab 105. In a first 360° rotation, overstrip 90 is removed. In a second 360° rotation, the tearstrip (or area between scores S, and S_?) is removed. Figs. 7A-7C provide an alternate embodiment.

Overstrip 190 is provided with hole 193 and is wrapped around container 70, over scores S, and S₂ (arrow 93 (Fig. 7A) indicating the rotation required to accordingly wrap overwrap 190 onto container 70) . Chevron 195 is punched across hole 193 (Fig. 7B) . Tab 200 is molded on top of

Chevron 195 so that tab 200 bonds with container 70 through hole 193. Overstrip 190 is preferably constructed like portion 110 of overstrip 90 as shown in Fig. 6F. Tab 200 must be molded with sufficient strength to container 70 so that when tab 200 is pulled, the area between scores S, and S„ (the tearstrip) comes away from container 70 and tab 200 does not separate therefrom.

In this embodiment, to open container 70, the end user need only place the container through one 360° turn because overstrip 190 comes off with the tearstrip.

Containers of this invention can be made by any suitable method. For instance, the container can be formed such as by blow or injection blow molding and then thereafter subjected to the edge(s) of a knife (or other sharp objects) to form the scores on the outer and inner ... surfaces; and after forming the scores the tab can be ^!ι applied by injection molding. Alternatively, prior to

applying the tab, an area of weakness such as a punch or chevron can be applied to the outer wall where the tab is to be applied. And, as shown above, after the scores have been applied, an internal collar can be installed, and then the tab applied (with or without the area of weakness, preferably with) . Or, after the scores have been applied, an overstrip, as shown above can be applied.

Molded-in scores can also be provided in the containers of the invention by any suitable means during the manufacture of the container, e.g., when the containers are blow molded, injection molded or injection blow molded or otherwise formed. For instance, during the blow molding a sidewall meander can be obtained by blowing prematurely and by compressing the overblown segment. This can provide the inner score. Molded-in outer scores in the meander are obtained by machining the neck blocks and blow mold of the apparatus to put in insert to form such scores. These inserts can be of metal; and, if the container is to be generally cylindrical or a tub or a bowl or the like, the inserts can be rings which, during the compression stage

(when the meander is formed) , bite into the meander and form the scores. The inserts can be designed, for example, to make a meander with a thickness of about 0.60" and a score depth of about 0.015", or, a meander with a thickness of ^m i

about 0.40" and a score depth of about 0.010". In this technique, care must be taken to avoid uneven compression which can be make the wall thickness in the upper part of the container greater than in the lower part. And, care 5 must also be taken to avoid over delamination of the container walls during manufacture. The meander and outer scores can also be formed by other methods.

Figs. 12 shows an embodiment of the scores made during manufacture and how the scores are formed. The

10 structure shown in Fig. 12 results from taking a molten parison, before it goes into the blow mold, and blowing in the direction of B. The scores S, and S₂ are then formed by compressing the over blown segment in the tooling.

Fig. 8 shows an apparatus for making a container,

■JE particularly for attaching a tab to a previously scored container. Injection molder 300 has hydraulic cylinder 240 for stamping and pumping . The previously scored container is inserted into mold 210. Knife 220 (by the stamping action of hydraulic cylinder 240) , stamps or punches an area ₀ of weakness at a place in the tearstrip (between S_. and S_?) . Extruder 260 provides thermoplastic material for the tab. The thermoplastic material flows through conduit 250 to area 230 which is the space for tab injection. After the knife has made the area of weakness, the tab is accordingly 5 injected onto the container which preferably has a feature around which the tab is formed and which provides a mechanical interlock between the container and the tab (so that after the end user pulls it, it can be so weak it comes off) . Knife 220 can have a contour such as a chevron. Alternatively, knife 220 can can be omitted from the apparatus and only a tab injected on the container. It is preferred to have knife 220 stamp an area of weakness prior to injecting a tab onto the container.

Furthermore, a tab can be heat-sealed or ultrasonically welded onto the wall of the container. One sort of tab can be a ultilayered structure. The ultra¬ sonically welded tab can be a ring pull tab or other shaped tab. For instance, a first layer is of a material which does not melt at the sealing temperature of the second, adhesive layer. Such a tab can have a first layer of PET, PBT or nylon bonded (laminated) to a second layer of a melt adhesive. Such a tab can also have additional layers, e.g., a layer of a barrier material such as EVOH or a pol vinylidene chloride copolymer.

Fig. 9 shows a design for a tab which can be heat- sealed onto the wall of a container. Portion 295 is a stress concentrator. It is preferably as wide as the area between the scores on the container. Portion 294 is the tab which extends off the container when tab 290 is affixed thereto. Length 293 is 2(pi)r where r equals the radius of the container if the container is generally cylindrical or a tub or bowl or the like. The width of tab 290 at portion 295 and the portion the length 293, can be as wide as the area between the scores on the container (e.g., 0.05 to .5"). Length 293 can be wider than the area between the scores on the container. Portion 294 is accordingly

₅ slightly wider so it can be grasped with and between the fingers of the end user. In this instance it takes two 360° rotations to remove the tab and the tearstrip. Note that this embodiment of the tab does not afford oxygen protection unless portion 293 is wider than the area between the scores 0 on the container.

If the container body is itself injection molded or injection blow molded a tab can be integrally formed with the container. A weakness to initiate the earlier mentioned fissure can be molded in or cut into the base of the tab by

•_jc a knife in a separate step.

Throughout this specification, reference has been made to multilayer structures, films or laminates. These structures, films or laminates are the same thickness as conventional multilayer structures, films, or laminates. 0 Typical thickness of films range from about 2.0 mils (0.051 mm) to 5 mils or more, with a normal range of about 0.5 to about 5.0 mils, preferably about 1.5 to about 3.0 mils (0.038 - 0.076 mm). Films thinner than about 1.5 mils (0.038 mm) may be too weak to perform their required 5 function (although individual layers of multilayer structures may be thinner than about 1.5 mils, e.g. about 0.25 to about 1 mil). Laminates can be up to 10 mils thick and multilayer structures can include films and laminates and can be up to 100 mils thick. A container from a multilayer structure can have an average thickness of about 30 mils. The following non-limiting example is given by way of illustration only and is not to be considered a limitation of this invention, many apparent variations of which are possible without departing from the spirit or scope thereof.

EXAMPLE

Three multilayer injection blow molded containers, each having a double seamed metal end, dimensions of 211x215 with sidewalls approximately 0.030 inches thick, and formed, from outer surface to inner surface of: PP/Adhesive/EVOH/ Adhesive/PP wherein the EVOH layer was about 2 mils thick, and the adhesive was a maleic anhydride modified polyolefin, were tested for oxygen permeability both before and after retorting. A first container had no scores. A second container had one continuous score on its outer surface. And, a third container had two continuous scores on its outer surface. The scores were about 0.022 inches deep and penetrated the EVOH layer. Prior to retorting, over the score of the second container was placed an olefin shrink band, Ray Chem TAT125. The shrink band was about 0.084 wide, 8 mil deep and had a radius of about 1.5". The permeation rate data is presented in Table 1, below. V

TABLE 1 Ox en Permeation Results

Retort*

No Score 0.093 One Score 0.27** Two Scores

1.6

* - units are cc/100 in day atm

** - score protected by olefin shrink band

It is noted that a coating of Saran latex (Dow) can also be applied to the scores of the containers of this invention to increase barrier protection. A coating of

Saran latex on a PP substrate (3 lb/3000 ft ) has a

2 permeation rate of 0.6 cc/100 in day atm. This will provide about the same protection as the aforementioned shrink band (approx. only a 2.6 fold increase in permeability after retorting) . Greater oxygen repair can be obtained by the internal collar of the present invention e.g. as shown in Figs. 5, 5B, 5C, where path length 65 can substantially restore the oxygen permeation resistance after retort; and even greater oxygen repair can be obtained by use of a combination of an external collar and/or gasket and an internal collar and/or gasket.

Having thus described in detail preferred embodiments of the easy-open container of the present invention, it is to be understood that the invention defined by the appended claims is not to be limited by particular details set forth in the above description as many apparent variations thereof are possible without departing from the spirit or scope of the present invention.

Claims

WHAT IS CLAIMED IS:

1. An easy open container comprising a body having sidewalls, at least said sidewalls being comprised of a structure having an internal weakness, said sidewalls having an inner surface, an outer surface, an upper portion and height, wherein, at said upper portion is an easy open feature, said easy open feature comprising: a first score on said outer surface of each sidewall and extending inwardly to the internal weakness, a second score positioned heightwise below said first score and on said outer surface of each sidewall and extending inwardly to the internal weakness, a third score positioned heightwise between said first and said second scores and on said inner surface and extending outwardly, and means at an area between said first and said second scores to effectuate opening of the container.

2. The container of claim 1 wherein said third score extends outwardly to the internal weakness.

3. The container of claim 1 wherein said internal weakness comprises said sidewalls being comprised of a multi¬ layer structure and at least one layer of said sidewalls being sufficiently oriented in a direction parallel to said scores, or at least one internal layer of said sidewalls has either low cohesive strength or poor adhesion with adjacent layers so that said weakness exists in said sidewalls.

4. The container of claim 1 wherein the scores are continuous.

5. The container of claim 1 wherein the scores are discontinuous.

6. The container of claim 1 wherein said sidewalls are comprised of a multilayer structure wherein at least one internal layer is comprised of a polymeric barrier material.

7. The container of claim 6 wherein the first and second scores extend inwardly through the internal layer of polymeric barrier material.

8. The container of claim 7 wherein the third score extends outwardly through the internal layer comprised of polymeric barrier material.

9. The container of claim 1 wherein said sidewalls are comprised of a multilayer structure and said internal weakness comprises an internal layer capable of delamination.

10. The container of claim 1 wherein the internal weakness comprises a line of mechanical weakness.

11. The container of claim 7 further comprising an internal or an external collar and/or gasket or a combination thereof, wherein said external collar and/or gasket is positioned over said first and second scores on said outer surface, and said internal collar and/or gasket is positioned on said inner surface at at least an area corresponding to the location of said first and second scores.

12. The container of claim 11 wherein the internal collar and/or gasket is a body of a shape corresponding to that of the upper portion of the container and said collar is slightly larger than the said upper portion so that said internal collar is positioned by a press-fit against said inner surface.

13. The container of claim 12 wherein the container has a generally cylindrical or generally bowl

_1Q shape and the internal collar has a shallow cup shape.

14. The container of claim 11 wherein the external collar and/or gasket is comprised of aluminum, or a multilayer structure having a layer of an oxygen barrier material, or of an olefin shrink band, or of a

, ₅ polyvinylidene chloride copolymer latex spray having dried, or of an epoxy spray having dried, or of a nylon spray having dried or of an ethylene vinyl alcohol/propanol/water spray having dried.

15. The container of claim 11 wherein the

_2Q internal collar and/or gasket is comprised of aluminum, or a multilayer structure, a multilayer structure having a layer of an oxygen barrier material, or a structure comprised of a thermoplastic rubber.

16. The container of claim 15 wherein the

₂₅ internal collar and/or gasket comprised of a multilayer structure having a layer of an oxygen barrier material 3b comprises a plurality of superimposed layers comprising a first outer layer comprising thermoplastic rubber, or polypropylene or a polypropylene blend, a second outer layer of a barrier material comprising ethylene vinyl alcohol or a polyvinyldene chloride copolymer, and a third layer disposed between said first and second layers comprising an adhesive, wherein said second outer layer of said multilayer structure is disposed against said inner surface of said container.

17. The container of claim 11 wherein the internal collar and/or gasket is comprised of polypropylene, or a blend of polypropylene, or nylon, or mica-filled nylon, or polyethylene terephthalate, or polybutylene terephthalate or MXD6, or thermoplastic rubber.

18. The container of claim 11 wherein the external collar comprises the opening means.

19. The container of claim 1 where the opening means comprises a tab molded or heat-sealed or welded to the outer surface over and/or between the first and second scores.

20. The container of claim 1 wherein the opening means comprises an area of weakness applied to a point on the outer surface between the first and second scores, and a pull tab molded or heat sealed thereover.

21. The container of claim 20 wherein a mechanical interlock is provided between the container and the tab.

22. The container of claim 20 wherein the area of

weakness is a notch, punch, stamp, cut or chevron.

23. The container of claim 1 wherein the opening means comprises an overstrip affixed to said outer surface over said first and second scores.

24. The container of claim 23 wherein said overstrip has a hole in it through which an area of weakness is stamped onto the outer surface of the container and a pull tab is molded or heat sealed thereover.

25. The container of claim 24 wherein the overstrip comprises a multilayered structure having a layer comprised of barrier material.

26. The container of claim 23 wherein the overstrip is comprised of a multilayer structure comprising a plurality of superimposed layers, said overstrip and has a first area corresponding in width to the area between the first and second scores, and a second area comprising the remainder of the overstrip and being wider than first area; the multilayer structure comprising a first outer layer of a barrier material and a second layer disposed beneath said first layer and in contact with the outer surface of said ² container, said second layer, at the first area comprising a material with strong adhesion to the outer surface of the container, and at the second area comprising a material with peelable adhesion to the outer surface of the container; and, the length of said first area being sufficient so that when said overstrip is pulled off of said container enough i

force is applied to a portion of the area between said first and second scores so that a fissure occurs thereat; and, the length of said second area being sufficiently greater than one complete wrap over said first and second scores so that a sufficient amount extends off of the container and forms a pull tab.

27. The container of claim 26 having an area of weakness applied to said outer surface at the portion where said first area of said overstrip is to be applied.

28. The container of claim 23 wherein the overstrip comprises a first portion which is a stress concentrator, a second portion which is a complete wrap over and/or between said first and second scores, and a third portion which is a pull tab, wherein the width of the first and second portions generally corresponds to the area between the first and second scores, and the third portion is wider than the first and second portions.

29. The container of claim 1 having a generally cylindrical or generally bowl shape.

30. The container of claim 11 wherein the container has a generally cylindrical or generally bowl shape, the internal collar has a shallow cup shape, and the internal collar is also a top for the container.

31. The container of any one of claims 6-8, or 11-18 wherein the internal layer of the container comprised of a barrier material is comprised of ethylene vinyl alcohol, or polyvinylidene chloride methyl acrylate copolymer, or polyvinylidene chloride polyvinyl chloride copolymer.

32. The container of claim 31 wherein said sidewalls are comprised of a multilayer structure comprising a plurality of superimposed layers comprising a first layer, a second layer, a third layer, a fourth layer, and a fifth layer wherein said first layer is an outer layer comprised of polypropylene or a polypropylene blend, said second layer is disposed between said first and third layers and is comprised of an adhesive, said third layer is disposed between said second and fourth layers and is the internal layer comprised of a barrier material, the fourth layer is disposed between said third and fifth layers and is comprised of an adhesive, and said fifth layer is an outer layer, disposed over said fourth layer and is comprised of polypropylene or a polypropylene blend.

33. A method for making a container having an easy open feature comprising: forming a body having sidewalls being comprised of a structure having an internal weakness and having an inner surface and an outer surface, scoring said inner and outer surfaces so that there are first and second scores on said outer surface, said second score heightwise below said first score, and a third score on said inner surface heightwise between said first and second scores, and applying between said first and second scores means to effectuate opening of the container.

34. The method of claim 33 wherein forming the structure having internal weakness comprises orienting at least one layer of said sidewalls in a direction parallel to said scores, or employing an internal layer of said sidewalls having either low cohesive strength or poor adhesion with adjacent layers so that a said weakness exists in said sidewalls, or forming said structure as a multilayer structure with an internal layer capable of delamination, or creating a line of mechanical weakness.

35. The method of claim 33 wherein the scoring is applied by a knife.

36. The method of claim 33 wherein the scoring occurs during forming the body.

37. The method of claim 36 wherein said forming comprises blow molding and the scoring comprises blowing a parison prior to said blow molding.

38. The method of claim 33 wherein the application of opening means comprises molding or heat-sealing or welding a tab.

39. The method of claim 33 wherein the application of opening means comprises applying an area of weakness and molding or heat-sealing or welding a tab thereover.

40. The method of claim 33 wherein the application of opening means comprises applying an overstrip.

41. The method of claim 33 wherein said opening means comprises a tab and the application thereof is performed during the forming step.

42. The method of claim 33 further comprising: reinforcing barrier properties of the said container comprising applying an internal or external collar and/or gasket or a combination thereof, wherein said external collar and/or gasket is positioned over said first and second scores on said outer surface, and said internal _Q collar and/or gasket is positioned on said inner surface at at least an area corresponding to the location of said first and second scores.

43. An apparatus for applying a tab to a body for forming a container having an easy open feature wherein said

-, ₅ body has sidewalls structure having an internal weakness and an inner surface and an outer surface and said inner and outer surfaces are scored so that there is a first score on said outer surface, a second score on said outer surface heightwise below said first score, and a third score on said

2o inner surface heightwise between said first and second scores, said apparatus comprising an injection molding unit comprising an extruder to plasticate polymeric material for said tab; ₂₅. pumping means for injection of thermoplastic material; * . ^•

means defining a space for tab injection; a conduit between said extruder and the said space for tab injection; and means adjacent to the space for tab injection defining a mold space to load said body with a portion of the area between said first and second scores aligned with said space for tab injection so that a tab can be injected onto said body at said portion by the pumping means pumping polymeric material from said extruder through said conduit, into the space for tab injection and onto said body.

44. The apparatus as claimed in claim 43, further comprising a movable knife adjacent to said mold space and in communication with said pumping means such that said pumping means also provide a stamping motion to said knife so that prior to tab injection and at said portion of said area between said first and second scores where said tab is to be injected, an area of weakness is stamped by said knife.

45. The apparatus of claim 43 wherein the pumping means comprises at least one hydraulic cylinder.

46. The apparatus of claim 43 wherein the pumping means comprises said extruder.