Easy open pouch with energy activation

Abstract

The present invention includes a sheet of flexible packaging material that includes one or more films having an inner side and an outer side. On the outer side of at least one film is a pattern of activation particles, preferably metal flakes or the like. The pattern of particles is energy activated causing the pattern to heat and penetrate or weaken at least a portion of the film, creating a tear line in the wall of a package formed from the sheet. A method for creating a tear line in a sheet of flexible packaging material and the formation of the material into a package with a tear line in the side wall or the like is also defined.

Description

TECHNICAL FIELD

The present invention relates to the field of flexible packaging. Particularly, the invention relates to flexible packaging material with an easy-open tear line therein and methods for making a flexible packaging material with a tear line.

BACKGROUND OF THE INVENTION

There are a variety of methods used to perforate, score, notch or otherwise create a line of weakness in a flexible packaging material for opening a sealed package. Many of these methods include using caustic or acidic solutions to remove a portion of the material, using mechanical means to cause a line of weakness in the material, and/or re-orienting the substrate material to improve tear efficiency. These methods often produce a packaging material that includes one or more of the following deficiencies: lack of non-linear tear lines in the material, lack of cross directional tear lines in the material, or high cost.

SUMMARY OF THE INVENTION

One embodiment of the present invention is a sheet of flexible packaging material that includes one or more films having an inner side and an outer side. On the outer side of at least one film is a pattern of particles. The particles are exposed to or receive a dose of energy causing them to create heat and penetrate or weaken the film, thereby creating a tear line.

In another embodiment of the present invention, the sheet of flexible packaging material with a tear line formed by energy exposed particles is provided within a package.

In a further embodiment of the present invention a method is provided for creating a tear line in a sheet of flexible packaging material. The method includes providing a sheet that comprises one or more films. A pattern of metal or similar particles is applied on the one side of the sheet or films. The pattern of particles is dosed with an energy source causing the particles to create heat and penetrate into the sheet or film material; thus, creating a weakened area and a tear line along the particle pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, there is shown in the drawings various forms which are presently disclosed; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities particularly shown.

FIG. 1 is an exaggerated cross sectional view depicting a sheet of flexible packaging material including a film layer and a line of particles according to a method of the present invention.

FIG. 2 is an exaggerated cross sectional view depicting a sheet of flexible packaging material including two film layers, with a line of particles there-between according to a method of the present invention.

FIG. 3 is a plan view of one form of a flexible package made according to the present invention.

FIG. 4 is a perspective view of an alternate flexible package form made according to the present invention.

FIG. 5 is a perspective view of a further alternate form of a package made according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the drawings, where like numerals identify like elements, there is shown in FIG. 1 a sheet of flexible packaging material, which is generally designated by the numeral 10. As used herein, the term “sheet of flexible packaging material” includes materials used in the manufacture of flexible packages (e.g., candy wrappers) and materials used in covering and/or sealing rigid or semi-rigid containers (e.g., microwavable dinner containers).

As shown in FIG. 1, the sheet 10 includes a first film layer 14 having an outer side 16 and an inner side 18. The sheet 10 further includes a pattern of particles 12 on the outer side 16 of the film 14. The particles 12 are dosed with or exposed to an energy source so as to create heat and to penetrate into the surface of the outer side 16 of the film 14. The heated penetration of the particles 12 into the film 14 weakens the film 14, creating a “tear line”. This weakened area of the film is defined herein as a “tear line” regardless of whether the weakened area is in fact linear. The depth at which the energy reactive particles penetrate the film after exposure, as shown in FIG. 1, is merely illustrative and should not be construed to limit the present invention.

The sheet 10 can be manufactured using a method of providing the film 14, applying a pattern of particles 12 onto the outer side 16 of the film 14, and then exposing the pattern to an energy source, thus heating the pattern of particles 12 such that the particles 12 weaken the adjacent portions of the film 14 to create a tear line.

The film 14 may include any number of layers or plys and may be made of one or more of ethylene vinyl alcohol, polyvinyl alcohol, polyethylene terepthalate, nylon, or a polyolefin. Preferably, one or more polyolefins are used. Polyolefins are preferred because of their strength and because of their normally good tear resistance. The polyolefins include, for example, one or more of polypropylene, polyethylene, linear low density polyethylene, and low density polyethylene.

The energy reactive particles 12 can be in a variety of forms such as metal flakes, metallic powders, metal oxides, or derivatives thereof. The particles 12 can have sharp edges to allow for greater and/or easier penetration into the film wall. The particles 12 may also be substantially flat or three-dimensional, such as an ellipse, cube or sphere, or be some non-geometric shape.

The size of the particles 12 preferably ranges from about 5 microns to about 30 microns. More preferably, the particle size is from about 10 microns to about 20 microns. When applied to the film, the particles 12 are preferably non-uniform in size. Non-uniformity allows for greater density of the particles, because the smaller particles can fill the interstitial void spaces created by the larger particles.

Preferably, the particles 12 are in the form of metal flakes. Metal flakes have a high aspect ratio such that they are platelet-shaped or saucer shaped. Different metals can be used for the particles 12. For example, the metal particles 12 can be aluminum, nickel, chromium, gold, germanium, copper, silver, titanium, tungsten, platinum, tantalum, and metal alloys. Preferably, the particles 12 retain or create heat when exposed to an energy source, such as radio frequency (“RF”), microwaves or the like. Preferably, the particles 12 are aluminum.

To make the particles 12 easier to apply, they can be dispersed in a resin or treated with a solvent to make an ink. The resin serves as an adhesion promoter, allowing the particles to adhere to the film. The solvent lowers the viscosity of the ink, making it easier to print onto the film using conventional printing techniques, such as rotogravure or flexographic. Flexographic and rotogravure printing are well known in the art and, in the interest of conciseness, will not be described here. The ink containing the metal particles can be front printed or reverse printed onto the film or a layer or ply within the sheet.

Preferably, the density of the particles 12 in an ink is from about 1% to about 30% loading based on solids, and more preferably from about 5% to about 20% loading based on solids.

The pattern of particles is energy dosed in order for them to create heat and to create the weakness line in the sheet that defines the tear line. Energy dosing can be performed using electron beam (“EB”) radiation, ultraviolet (“UV”) radiation, ultrasonic energy, microwaves or, preferably, radio frequency (“RF”) energy. The energy dose can be applied to the sheet of flexible packaging as a whole or to only a portion of the sheet or packaging. Preferably, the energy is applied to only the particles to heat the area of the sheet immediately adjacent the particles.

When radio frequency is used, the curing energy preferably has a frequency from about 30 gigahertz (“GHz”) to about 300 GHz. More preferably, the curing energy has a frequency from about 100 GHz to about 200 GHz.

Preferably, when the metal particles are exposed to the energy source, they absorb or react to the energy, creating heat. The heat from the particles then melts or penetrates the film in the area directly adjacent the particle pattern, weakening the film in that area. The depth at which the particles penetrate or otherwise weaken the film will vary depending on several factors. These factors include the type of film, the thickness of the film, the number of film layers, the number of co-extruded films, the frequency of the energy at which the particles are dosed, the type of particles, and the end use of the packaging material (e.g., a package, a cover, or a seal). For example, for a sheet of packaging material including a film of 2 mil thick polyethylene with a pattern of aluminum metal flakes, RF energy can be applied such that the depth of penetration is about one thousandth of an inch. This amount of penetration is sufficient to achieve the desired concentrated weakening of the polyethylene film and the desired tearline.

Generally, the energy curing is substantially instantaneous. For example, when RF energy is used to cure the metal particles, only a brief exposure (i.e., less than a few seconds) of the energy is necessary to create the desired tear line. Longer exposure may be necessary for certain metal particles or films, if deeper penetration is desired.

The energy exposure preferably occurs before the packaging material is formulated into an end product such as a flexible package or a cover/seal for a rigid container (See FIG. 5). For sheets of flexible packaging material that are stored in a roll, the energy curing preferably occurs after the flexible material is rolled. For a sheet of flexible packaging material where the particles are between two or more joined (e.g., laminated or co-extruded) films or layers, the energy dosing preferably occurs after the films are joined, but before the flexible material is formed into a package or other similar end product.

Preferably, the particles are positioned such that they will not contact any food product or similar materials that are placed inside the package created from a sheet of flexible packaging material of the present invention (e.g., one or more film layers between the metal particles and the food products or the like). Preventing the food products from contacting the metal particles prevents potential contamination.

The sheet 110, as shown in FIG. 2, includes two film layers. An inner side 22 of a second film 20 is joined with the outer side 18 of the first film 14. The first film 14 and the second film 20 can be manufactured such that both of the films include a polyolefin, only one of the films includes a polyolefin, or neither of the films include a polyolefin. The two films can be joined to create the sheet by co-extrusion, co-polymerization, adhesion or other similar methods.

Although FIG. 2 shows a sheet with two films, it is within the scope of the present invention to have a sheet with more than two film layers or plys. When more than two layers or plys are provided, two or more of the films can be joined by co-extrusion, co-polymerization, adhesion or other similar methods.

As shown in FIG. 2, the particles 12 are positioned between the outer side 16 of the first film 14 and the inner side 22 of the second film 20. The metal particles as shown in FIG. 2 are applied to the outer side 16 of the first film 14 such that when the metal particles are dosed with energy, they penetrate the outer side 16. Alternatively, the metal particles are applied to the inner side 22 of the second film 20, such that when the metal particles are energy dosed, they penetrate the inner side 22. In a further alternative, the application of energy to the particles causes the metal particles to penetrate both the outer side 16 and the inner side 22.

The sheet of packaging material can include graphics. Preferably, the graphics are printed in a flexographic or rotogravure printing process that is synchronized with the printing of the particles. The graphics can be reverse printed on an outside film layer that is joined to the surface of an underlying film. For example, graphics can be reverse printed on the inner side 22 of the second film 20.

As an alternative, graphics can be printed on the outside 24 of the second film 20 with a coating being applied over the graphics. Such coatings include, for example, UV, RF, MW or EB reactive materials, or over lacquers known in the industry. Preferably, the coating is cured using the same energy source that activates the pattern of particles to create the tear line.

As shown in FIGS. 3 and 4, the sheet of packaging material is made into a package. In FIG. 3, two sheets of flexible packaging material, a first sheet 10 and a second sheet (not identified), are made into a package 26 with a tear line of metal particles 12. The package has sealed seams 28 that enclose and seal the contents of the package 26. The package has an optional tear notch 30. As illustrated, the tear notch 30 is positioned adjacent the tear line created by the particles 12, such that a user starts the tearing process at notch 30 and continues it along the tear line.

Also as illustrated, the pattern of particles 12 is applied in a contoured shape. Because the particles can be printed on the film in the same manner as ink is printed, the tear line is not limited to a machine direction tear of the film. In fact, the tear line can be in any shape that can be printed onto the film. As shown in FIG. 3, the tear line is in a circular shape to accommodate easy removal of a pull-off coupon 32 and the like. The circular tear line allows for a portion of the film (i.e., the pull-off coupon 32) to be removed from the package when tab 34, which sits above the film, is pulled.

The package 26 includes an inner side of a first sheet 10 contacting an inner side of a second sheet (not shown). The two sheets are sealed around all four sides at seams 28 by heated sealing jaws, adhesives or other similar devices.

Alternatively, the package may include only a sheet of packaging material and be configured so as to include a lap seal or a fin seal. A lap seal is formed, for example, when the sheet is slit to an appropriate width, formed into a tubular structure with opposed edges overlapped and sealed. Thus, the inside surface of one edge is sealed to the outside surface of the opposed edge with the seal extending substantially parallel with the adjacent portion of the tubular structure. A fin seal, on the other hand, is formed when the inside surface of each opposed edge of the tubular structure are brought into contact with one another and sealed. Such a seal can extend in a direction independent of the adjacent portion of the tubular structure, and absent folding or other influence, tends to extend perpendicular thereto.

The flexible packaging material can also be formed into a pillow pouch. The sheet is again formed into a tubular structure. The top of the tubular structure and the bottom of the tubular structure are collapsed between sealing jaws to form a top end seal and a bottom end seal, respectively. The pillow pouch also includes a longitudinal lap seal, which is formed as described above.

The pillow pouch can be formed, filled and sealed on a vertical or horizontal form-fill-seal machine. When the pouch is formed on a vertical form-fill-seal machine, the laminate is first slit to the appropriate width. The laminate is then fed to the vertical form-filled machine, which forms the tubular structure, the bottom end seal and longitudinal lap seal. The pouch is filled with a product prior to forming the top end seal.

Preferably, the adhesive used to seal the packages of the present invention is a cold seal cohesive. A cohesive material is defined as a material that adheres strongly to another surface of the same material and only weakly to other materials.

Where two sheets are joined to form the package, the cold seal cohesive is applied to an inside surface of the first sheet and an inside surface of the second sheet. The cold seal cohesive can be a continuous layer, but preferably is pattern-applied at only those places where a seal is to be formed (e.g., around the edges of the first and second sheets). Once the cold seal cohesive is in place, the inside surface of the first sheet and the inside surface of the second sheet are contacted. The two sheets are then sealed together using sealing jaws or other similar devices.

Alternatively, where the package comprises only a single sheet of packaging material, two separate patterns, a first pattern and a second pattern, of the cold seal cohesive are applied to the single sheet. In such an embodiment, the step of forming the package involves sealing the first pattern of the cold seal cohesive on the sheet with a second pattern of a cold seal cohesive on the sheet. As described above, the seal can be an end seal, a lap seal, a fin seal or the like, and may include, if desired, a notch at the edge of the package for starting the tearing of the film.

The advantages of pattern-applying the cold seal cohesive include the fact that far less cold seal cohesive is necessary and that the cold seal cohesive does not contact the contents of the package, or does so only along very narrow areas at the seams. Pattern-applying the cold seal will be necessary for some uses, especially food uses, where more than minimal contact between the contents of the package and the cold seal cohesive will not be acceptable.

Preferably, the machine for applying the cold seal cohesive is a flexographic or rotogravure printing machine forming part of the same production line as, and is mechanically synchronized with, the machine used for the printing of the particles. Such synchronization provides for an efficient packaging process.

The cold seal cohesive can be based on rubber latex, but is preferably based on uncured isoprene or styrene butadiene rubber. These synthetic rubbers are more stable than natural rubber, allowing a material with a longer life, are more consistent, and do not present the risk of allergic reactions, and even anaphylactic shock, experienced by some people with natural latex products.

Alternatively, the seams of the package can be sealed with a hot melt adhesive. A package with seams sealed with a hot melt adhesive can be manufactured as described above. For example, the sheet of packaging material 10 can be wrapped into a tubular structure with overlapping opposed edges. The overlap can be formed by contacting the inner side 16 and the outer side 18. A bead, in the form of a line or one or more drops, of hotmelt adhesive can be applied to one of the edges in order to join the overlapping edges. The joined edges are then sealed with sealing jaws or other similar devices to create a heat sealed seam.

Flexible packaging made from the sheet of flexible packaging material 10 can be in various forms. As shown in FIG. 4, the sheet of flexible packaging material is formed into a flexible, air-tight package 36. The package 36 includes sheets of packaging material with one or more joined films sealed along one or more seams. The package 36 includes a sheet 10 with metal particles 12, which, when cured, create a tear line. The package 36 also includes an optional tear notch 30 that is adjacent the tear line. The tear line provides for an easy opening package. The optional tear notch 30 aids in the ease of opening the package by providing a starting point for tearing.

The package 36 can be used to hold various air-perishable products such as meats, cheeses, coffee, chips, nuts, and other foodstuffs. After the products are inserted into the package, the package can be exposed to a vacuum so that the contents of the package are not exposed to the degradation effects of air. Consequently, the packaged products can have a shelf life comparable to rigid packages (e.g., jars or cans).

With the flexible airtight package 36, the tear line serves as a weakened area, allowing a user to open the package more easily. To maintain the airtight nature of the package 36, the depth to which the particles penetrate is such that the tear line does not adversely affect the barrier properties of the package.

The flexible packaging of the present invention is not limited to air-tight packages. Rather, the flexible packaging can be formed into a non air-tight pouch or wrapper, for example, a pouch or wrapper for food articles such as fruits and vegetables.

In a non air-tight package, the tear line not only allows a user to open the package more easily, but it also can provide a “breathable” area in the package. As used herein “breathable” means allowing oxygen and/or water vapor transmission through the packaging material. The rate at which oxygen passes through the material is termed the oxygen transmission rate, and can be measured by standard means known in the industry. The rate at which the water vapor passes through the material is termed the water vapor transmission rate, and it also can be measured by standard means known in the industry.

To create a breathable area in the package, the particles must penetrate the film to such depths that oxygen and/or water vapor can be transmitted through the tear line. To create a breathable area, it is preferred that the packaging material include a thermoplastic material that will soften more than other materials when exposed to the energy dose and the heat of the particles.

Flexible packaging, whether it is an air-tight package or another type, provides numerous advantages over rigid packages. For example, flexible packages can be manufactured at a lower cost than rigid packages and are generally substantially lighter in weight than rigid packages. Further, flexible packages can be stored flat, reducing the amount of storage space required for unfilled packages.

As shown in FIG. 5, a sheet of flexible packaging material 210 forms a cover for a substantially rigid container 214, such as a microwavable dinner package 208. A pattern of particles 212 to be energy dosed to create a tear line in the wall 210 covering the top of the container 215. The pattern of particles 212 is applied such that a user can easily remove a portion of the cover sheet 210 to expose a food product A (e.g., apple sauce) that is to be cooked uncovered. This allows food products B, C and D (e.g., stuffing, peas, turkey) to be covered by sheet 210 during cooking.

It will be appreciated by those skilled in the art, that the present invention may be practiced in various alternate forms and configurations. The previously detailed description of the disclosed embodiments is presented for purposes of clarity of understanding only, and no unnecessary limitations should be implied there from.

Claims

1. A sheet of flexible packaging material comprising:

a first film layer, the film comprising an inner side and an outer side; and

a tear line on the outer side of the film, the tear line comprising an energy dosed pattern of particles penetrated into the outer side of the film.

2. A sheet of flexible packaging material according to claim 1 wherein the sheet further comprises an inner side of a second film joined to the outer side of the first film.

3. A sheet of flexible packaging material according to claim 2 wherein the second film and the first film are co-extruded.

4. A sheet of flexible packaging material according to claim 1, wherein the film comprises a polyolefin.

5. A sheet of flexible packaging material according to claim 4 wherein the film is selected from the group consisting of polypropylene, polyethylene, linear low density polyethylene, and low density polyethylene.

6. A sheet of flexible packaging material according to claim 1 wherein the particles are made of a metal material.

7. A sheet of flexible packaging material according to claim 6 wherein the metal particles are from about 5 microns to about 30 microns in size.

8. A sheet of flexible packaging material according to claim 6 wherein the metal particles comprise aluminum flakes.

9. A sheet of flexible packaging material according to claim 1 wherein the particles are formed in a non-linear pattern.

10. A sheet of flexible packaging material according to claim 1 wherein the particles of the tear line are dispersed in an ink.

11. A sheet of flexible packaging material according to claim 1 wherein the particles are activated by radio frequency energy.

12. A sheet of flexible packaging material according to claim 11 wherein the radio frequency is from about 30 gigahertz to about 300 gigahertz.

13. A sheet of flexible packaging material according to claim 1 wherein the particles are exposed to an ultrasound energy source.

14. A flexible package comprising:

a sheet of flexible packaging material according to claim 1 formed into a tubular structure with a bottom end and a top end;

a seam formed along the bottom end, a seam along the top end, and a longitudinal seam along a length of the package, wherein the seams enclose the package.

15. A method for making a sheet of flexible packaging material with a tear line, the method comprising:

providing a first film, the film comprising an inner side and an outer side;

applying a pattern of activation particles on the outer side of the film; and

exposing the pattern of activation particles to an energy source, causing the particles to heat and weaken the film adjacent the particle pattern and to create the tear line.

16. A method according to claim 15 wherein the particles are exposed to radio frequency energy.

17. A method according to claim 16 wherein the radio frequency is from about 30 gigahertz to about 300 gigahertz.

18. A method according to claim 15 wherein the particles comprise metal flakes.

19. A method according to claim 15 wherein the particles comprise aluminum.

20. A method for forming a package with a tear line, the method comprising:

providing at least one sheet of flexible packaging material produced according to the method of claim 15;

forming the sheet into a tubular structure with a bottom end and a top end;

sealing a seam along the bottom end and sealing a longitudinal seam along a length of the tubular structure;

filling the package with a product from the top end, the product contacting the inner side of the sheet; and

sealing the top end to enclose the product.

21. A method according to claim 20 wherein the seams are sealed by a cold seal cohesive.

22. A method according to claim 20 wherein the seams are sealed with a hot melt adhesive.