WO2004037646A2

WO2004037646A2 - Multi-layer metallized packaging material and method of making same

Info

Publication number: WO2004037646A2
Application number: PCT/US2003/033989
Authority: WO
Inventors: John E. Cahill
Original assignee: Graphic Packaging International, Inc.
Priority date: 2002-10-23
Filing date: 2003-10-23
Publication date: 2004-05-06
Also published as: AU2003284168B2; AU2003284168A1; EP1585668A2; CA2503202A1; WO2004037646A3; JP2006503734A

Abstract

A metallized packaging material (100) is prepared by laminating a metallized release film (32) to paperboard (22) utilizing an extruded polymer layer (42) between the metallized release film (32) and the paperboard (22) and passing the layered structure between a nip roll and a chilling roll (36). The metallized release film (32) comprises a release film (32a) having a metal deposit (32b) applied to a first surface. After lamination, the release film (32a) is removed from the multi-layered structure, leaving the metal deposit. A top layer (72), such as extruded polymer or an aqueous coating is then applied to the metal deposit (32b) to form the metallized packaging material (100).

Description

Multi-layer metallized packaging material and method of making same

INVENTOR

John E. Cahill of Hampton, New Hampshire

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. provisional patent application no.

60/420,727 entitled "Multi-Layer Metallized Packaging Material and Method of Making

Same," filed 23 October 2002, which is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention

[0003] The present invention relates to a multi-layer metallized packaging material and a method of producing a multi-layer metallized packaging material. [0004] 2. Description of the Related Art

[0005] In the packaging industry, packaging materials may comprise a plurality of layers of different materials combined together in order to exploit the different, advantageous properties of each material. The use of different materials provides an optimum combination for the particular kind of package or the particular product that is to be packaged. It is generally desirable for packaging materials to be able to withstand rough, abusive treatment and endure prolonged exposure to corrosive substances. The packaging further preferably provides an impervious barrier to isolate substances within containers, reduce or prevent absorption and/or transmission of liquid components, contain fragrances and flavors within the packaging interior, and prevent oxygen and other ambient gases from passing through the packaging material. It is preferable for packaging material to be heat sealable. It is also desirable for the packaging material to be economical to manufacture. [0006] Paperboard is widely used to form containers for packaging products. It is typical to use resin coatings, films, and foils in one or more layers to provide a barrier between the contents of the container and the paperboard. Foils may also be used to add a decorative effect to the packaging. However, they typically require complicated and expensive equipment and procedures, utilize expensive resins, foils, and films, and may be incompatible with existing carton manufacturing systems. Furthermore, many packaging materials are subject to warping caused by distortion of one or more of the layers. [0007] A typical packaging material in the prior art incorporating a metal foil layer is composed of a base of paperboard laminated to the metal foil, which is supported on a paper layer. The metal layer is generally placed on the paper layer by vacuum deposition. An adhesive is dispensed between the paperboard and the paper layer and the two are laminated together. In this design the metal foil is exposed as the outer surface of the packaging material. This design is problematic, however, as the metal foil layer is unprotected and is easily scuffed or scraped off the packaging material, limiting its function as a barrier layer or as a decorative feature. Additionally, it is difficult to print on the metal foil layer as most commercial inks do not bond well to metal. Therefore, expensive printing processes must be invoked, for example, using buried ink processes. Another alternative is to print the paper layer before depositing the metal layer at a low optical density such that the ink can be seen through the metal layer. Such a multi-step process adds significantly to the manufacturing cost because the printing step must be planned well in advance and cannot be performed inline with the rest of the package manufacturing process. There is no ability to alter the print design on the package to produce alternate designs in-line.

[0008] Another known packaging material process incorporating metal foil involves laminating a metal layer supported on a plastic web, for example, polyethylene, to a paperboard substrate. As before, the metal layer is generally placed on the plastic layer by vacuum deposition. In this process, an adhesive is dispensed between the paperboard and the metal layer and the two are laminated together. The metal layer is thereby sandwiched between the paperboard and the plastic. As a result, the plastic layer provides a protective coating over the metal and provides a surface that can generally be printed on.. There are, however, drawbacks to this process and packaging material design as well. First, special adhesives must be used in order to adhere the metal layer to the paperboard. This can add significant cost to the manufacturing process. Second, in order to assemble a finished package, a hot melt adhesive must be used in order to adequately adhere two plastic layers together. This requirement compromises efficiencies in gluing rates and slows the manufacturing process.

BRIEF SUMMARY OF THE INVENTION

[0009] The present invention provides a system and method for manufacturing a multilayer packaging material comprising a substrate, such as paperboard, and a metallic layer adhered to the substrate. One or more extruded polymer layers are included in the packaging to add strength and barrier to the final structure. The extruded layer also serves to adhere the metallic layer to the substrate layer. The packaging material further includes one or more top layers over the metal deposit to provide heat sealability, to add an additional barrier, to protect the metal surface, and/or to provide a printable surface. The top layer or layers of the packaging material may comprise an extruded polymer, an aqueous emulsion, and mixtures thereof.

[0010] The packaging material is formed by laminating a metallized release film to the substrate using one or more laminating layers of extruded polymer. The metallized release film comprises a release film having a metal deposit applied to a first surface of the release film. The release film is then removed from the metal deposit and one or more top layers of extruded polymer or an aqueous emulsion are applied to the metal deposit to form the packaging material. The removed release film can be discarded or re-used for a subsequent application.

[0011] According to one aspect of the invention, a method of manufacturing a metallized packaging material is provided. The method comprises the steps of providing a web of paperboard, providing a release film with a metal deposit applied to a first surface thereof, laminating the metal deposit to a first surface of the paperboard, removing the release film from the metal deposit, and applying one or more top layers to the metal deposit. The step of laminating involves using one or more extruded polymer layers to form an intermediate layered structure.

[0012] According to another aspect of the invention, a method of producing a packaging material is provided, comprising the steps of: providing a web of paperboard, providing a release film with a metal deposit applied to a first surface thereof, and applying one or more extruded top layers to the metal deposit. The method further comprises applying the metallized release film to the paperboard such that the metal deposit adheres to the paperboard, removing the release film from the metal deposit, and applying one or more top layers to the metal deposit.

[0013] According to another aspect of the invention, a system for manufacturing a metallized packaging material is provided. The system comprises a lamination station, a stripping station, and a finalizing station. The lamination station laminates a metallized release film to a paperboard substrate. The metallized release film comprises a release film having a metal deposit on a first surface thereof. The stripping station removes the release film from the metal deposit after the metallized release film is laminated to the paperboard. The finalizing station applies a top layer to the metal deposit after the release film is removed. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic view of the manufacturing process according to a preferred method of the present invention.

[0015] Figure 2 is a schematic cross-sectional view of the packaging material produced by the first lamination station.

[0016] Figure 3 is a schematic cross-sectional view of the packaging material after the release film is removed.

[0017] Figure 4 is a schematic cross-sectional view of the final packaging material product.

[0018] Figure 5 is a schematic view of a system for manufacturing the packaging material according to an alternate embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention provides an improved system and method for producing a metallized packaging material. The system and method produces a metallized packaging material efficiently and economically while reducing warping in the final packaging product. The present invention will be described below with reference to an illustrative embodiment. One skilled in the art will recognize that the invention is not limited to the illustrative embodiment and that variations may be made in accordance with the teachings and scope of the invention.

[0020] Referring to Figure 1, a schematic representation of the process of manufacturing the metallized packaging material of an illustrative embodiment of the invention is shown. The system 10 for manufacturing the packaging material includes a paperboard supply roll 20 for supplying a web of paperboard 22. The system 10 further includes a first lamination station 30 for laminating a metallized release film 32 to the paperboard 22 using at least one extruded polymer layer 42. The first lamination station 30 includes a cooling roll 36 and a nip roll 38 cooperating with the cooling roll 36. A release film supply roll 34 supplies the metallized release film 32 to the first lamination station 30. The metallized release film 32 comprises any suitable release film having a metal deposit applied to a surface of the release film. An extrusion die 40 for extruding one or more polymer layers 42 onto the paperboard 22 also forms a part of the first lamination station 30. The extruded polymer layers add strength and barrier to the final structure and also serve to adhere the metallic layer on the release film 32 to the paperboard layer 22. [0021] One skilled in the art will recognize that the extruded polymer layer 42 may comprise a plurality of extruded or co-extruded polymer layers. The polymer resin may be melted in any conventional extrusion device and discharged through the die 40 to form a descending sheet of molten resin which deposits into the nip between the advancing web of paperboard 22 and the metallized release film 32. The layer or layers 42 of molten polymer may be formed by extruding conventional polymeric materials, including for example, but not limited to, low, medium, or high density polyethylene, polypropylene, polyester, polyurethane, polyamide, and polyvinyl chloride as well as blends and copolymers thereof. [0022] The paperboard web 22 is paid out from the paperboard supply roll 20 and led over the nip roll 38 in contact with the cooling roll 36. The metallized release film 32 is simultaneously paid out from the release film supply roll 34 and led over the cooling roll 36, which synchronously rotates with the nip roll 38. At the same time, a continuous layer or layers of molten or semi-molten polymer material, for example polyethylene, is melted in a conventional extruder and extruded through the die 40 in the form of a sheet of molten resin 42. The molten polymer layer or layers are directed into the nip, i.e., the point of contact between the nip roll 38 and the cooling roll 36, between the metallized release film 32 and the paperboard 22. The molten polymer is extruded at a relatively high temperature so that good adhesion is obtained on the paperboard 22.

[0023] The molten polymer layer 42 pressed from the die 40 constitutes the lamination or binder layer between the metal deposit and the paperboard 22 and further provides an additional barrier layer for the final packaging material. The extruded polymer 42, not yet solidified, is compressed between the paperboard 22 and one side of the metal deposit, such that a mechanical bond ensues between the polymer layer 42 and the paperboard 22 and between the polymer layer 42 and the metal deposit. In this manner, the metal deposit on the release film 32 will be effectively bonded to the paperboard layer 22. [0024] At the same time, the polymer layer 42 cools down and becomes stabilized. The polymer layer 42 contacts the metal deposit on the release film 32, which contacts the cooling roll 36. The extruded polymer layer 42 will be cooled down via the cooling roll 36 and the heat discharged from the polymer layer 42 will pass at the same time through the metal deposit of the release film 32. The metal deposit becomes heated and by heat conduction transfers thermal energy to the cooling roll 36. As a result, the polymer layer 42 is cooled to such an extent that the polymer solidifies at the same time that the polymer layer 42 adheres to the metal deposit of the release film 32. [0025] The web of paperboard 22, having the layer of extruded polymer 42 thereon, and the metallized release film 32 are pressed together between the nip roll 38 and the cooling roll 36, and are thereby laminated. The resulting multi-layer intermediate laminate 50 produced by the first lamination station 30 is shown in Figure 2. The schematic cross section through the intermediate laminate 50 shown in Figure 2 illustrates how the intermediate laminate 50 produced in the first operation comprises a paperboard layer 22, an extruded polymer layer 42, a metallic layer 32b comprising the metal deposit, and a release film layer 32a. [0026] The thus formed intermediate structure 50 is further cooled by abutment against the surface of the cooling roll 36 for a portion of its circumference. A first guide roll 60 subsequently guides the intermediate multi-layer laminate 50 through the manufacturing system 10.

[0027] The release film may be metallized using any suitable means known in the art. According to one embodiment, a metallizer, comprising a high vacuum chamber through which a moving web of plastic release film is passed, is utilized to apply the metal deposit 32b to the release film 32a. In the vacuum chamber, a thin, uniform layer of a coating metal is deposited on the top surface of the moving release film 32a. Suitable materials for the metal deposit 32b include aluminum, lead, copper, silver, gold, or any other suitable metal for forming a barrier against penetration of gas or liquids through the final multi-layer packaging material and/or for providing decorative design to the final multi-layer packaging material. The metal is vaporized in the high vacuum chamber and the metal vapor is caused to condense on a moving web of the release film 32a. The metal is typically deposited on the web in a thin, uniform layer. Such layers may be between 50 angstroms and 7 microns or more in thickness. The metal deposit 32b may also be patterned by, for example, chemically etching a pattern in the metal layer 32b after its deposition onto the release film 32a. One skilled in the art will recognize that the metal deposit 32b may be applied to the release film 32a through any suitable means known in the art.

[0028] The release film 32a may comprise any suitable material, including, but not limited to, polyester, polypropylene, polyamide, fluoropolymer, trimethylpentane, polymer- coated paper, or any material having suitable release properties, smoothness, heat resistance and tensile strength.

[0029] The cooling roll 36 may comprise a metal roll that is cooled by any conventional technique, for example, by passing a cooling medium, i.e., water, therethrough. The temperature of the cooling roll 36 is generally maintained at about 60° F during operation. However, one skilled in the art will recognize that the cooling roll may be maintained at any temperature suitable for cooling and solidifying the polymer layers of the packaging material. The nip roll 38 may have a size and hardness suitable for applying pressure to a web of material.

[0030] The first intermediate laminate 50 next passes to a stripping roll 78 which removes the release film 32a, while leaving the metal deposit 32b on the top surface of the extruded polymer laminate layer 42. The resulting multi-layer metallized material 70 is illustrated in Figure 3. As shown, the metallized material 70 comprises the paperboard substrate 22, one or more layers of extruded polymer 42, and a top metallic layer 32b. [0031] The removed release film 32a may be collected on a release film collection roll 76 for further handling. The release film 32a may then be recycled and reused for manufacturing another web of packaging material. According to the illustrative embodiment, the release film 32a may be reused, thus realizing significant savings in cost, increased manufacture time and a reduction in waste. The removed release film may also be discarded or used for another application.

[0032] According to one embodiment, the release film 32a may include an additional coating, such as an acrylic coating, between the release film 32a and the metal surface 32b. When the release film 32a is removed from the first intermediate laminate 50, the release film 32a leaves the coating on the metal surface 32b. The additional coating can serve as a printing surface or a primer for subsequent layers of the packaging material. [0033] The metallized material 70 then passes through a second guide roll 74 to a finalizing station 80 to finalize the packaging material. The final component of the manufactured packaging material comprises one or more top layers 72 deposited on the metal layer 32b. The top layer 72 comprises a heat sealable layer for sealing the packaging material. The top layer further serves as an additional barrier layer and protective surface. The top layer may be a printable surface for the packaging to provide attractive graphics. [0034] According to an illustrative embodiment, as shown in Figure 1 , the top layer may comprise an extruded polymer material. The finalizing station 80 may therefore include an extrusion station, as shown in Figure 1 , for extruding the polymer material onto the metal layer. As shown, the extrusion station comprises a second cooling roll 86 and a second nip roll 88 cooperating with the second cooling roll 86. The extrusion station also includes a second die 84 for extruding molten or semi -molten polymer onto the metal layer 32b to form the top layer, according to one embodiment.

[0035] According to the first embodiment, the molten polymer forming the top layer 72 is directed to the nip formed between the second nip roll 88 and the second cooling roll 86. The metallized material 70 advances over the nip roll and the extruded polymer deposits onto the metal deposit layer 32b across the width of the metallized material 70. The metallized material 70, having the layer of molten extruded polymer thereon is pressed through the nip, and such that the molten polymer layer 72 adheres to the metal deposit layer 32b. The extruded polymer top layer 72 is then cooled to hardness.

[0036] The final multi-layer packaging material 100 formed by the final extrusion operation is shown in Figure 4. As shown, the multi-layer packaging material produced according to the teachings of the present invention comprises a paperboard layer 22, a polymer laminant layer 42, a metal layer 32b and a top layer 72. The polymer laminant layer 42 and the top layer 72 may comprise a plurality of layers of extruded or co-extruded polymer. Alternatively, the top layer 72 may comprise an aqueous material to enhance the clarity of the packaging material or other suitable material. After production, the resulting multi-layered packaging material 100 can be rolled up onto magazine reels 102 and be employed in the production of packaging.

[0037] According to another embodiment, as shown in Figure 5, the top layer 72 alternately be composed of an aqueous emulsion applied to the metal layer 32b. The finalizing station 80 may comprise a coating station 81 having a drying section 82 for coating and drying the aqueous emulsion on the metal layer 32b. The use of an aqueous material to form the top layer enhances the clarity of the multi-layer packaging material 100 and provides additional heat sealability. For example, the top layer 72 may be comprised of one or a mixture of styrenated acrylic polymers formed from an aqueous emulsion. The acrylic copolymer preferably is a latex formulation which may be formed from monomers including acrylic acid, methylacrylic acid, esters of these acids, and acrylonitrile. The coating station 81 may apply the aqueous emulsion through any suitable process known in the art, including for example, but not limited to, gravure coating, reverse gravure coating, and rod coating. The drying section 82 dries the aqueous emulsion on the metal layer to form the top coat through any suitable means known in the art, including for example, but not limited to, hot air and infrared energy. One skilled in the art will recognize that any suitable material and means may be used to form the top layer 72 of the multi-layer packaging material 100. [0038] According to one embodiment, the paperboard 22 may also have an aqueous or polymer coating on the side opposite to the extruded polymer layers 42 to provide an additional barrier. Alternatively, the additional aqueous or polymer coatings may comprise a printable surface, a heat sealable surface, and/or a protective surface. [0039] By using the processes of the present invention disclosed herein, a cost effective solution is achieved to provide a metal layer 32b in a multi-layer packaging material 100. The metal layer 32b is more resilient because of the top layer 72 of protective coating. The top layer 72 of encapsulating coating may also provide a greater gloss or sheen to the metal layer 32b resulting in more attractive packaging. The multi-layer packaging material 100 provides additional efficiencies by being both printable on-line and amenable to standard packaging adhesives, rather than requiring a hot melt adhesive to seal finished package products.

[0040] The present invention provides significant advantages over prior methods of manufacturing metallized packaging materials. The removal of the release film from the packaging material, while leaving the metal deposit in the packaging material, prevents or reduces warping of the final packaging product during the manufacturing process or during carton finishing of a carton made from the packaging material. The invention further results in an economical, efficient and simplified manufacturing process that reduces waste and cost. [0041] Since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. It is also to be understood that the following claims are to cover all generic and specific features of the invention described herein, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Claims

CLAIMSWhat is claimed is:

1. A method of producing a packaging material, comprising the steps of: providing a web of paperboard; providing a release film with a metal deposit applied to a first surface thereof; laminating the metal deposit to a first surface of the paperboard using one or more extruded polymer layers to form an intermediate layered structure; removing the release film from the metal deposit; and applying one or more top layers to the metal deposit.

2. The method of claim 1, further comprising the step of cooling the extruded polymer layers to hardness.

3. The method of claim 2, wherein the step of cooling comprises passing the intermediate layered structure over a cooling roll.

4. The method of claim 1, further comprising the step of recycling the release film after the step of removing the release film.

5. The method of claim 1, further comprising the step of re-using the removed release film to produce a packaging material.

6. The method of claim 1, wherein the release film further includes an acrylic coating between the release film and the metal deposit.

7. The method of claim 1 further comprising the step of coating a second surface of the paperboard with one of an aqueous material and a polymer material.

8. The method of claim 7, wherein the coating on the second surface of the paperboard is a printable surface.

9. The method of claim 7, wherein the coating on the second surface of the paperboard is heat sealable.

10. The method of claim 1, wherein the top layer is heat sealable.

11. The method of claim 1 , wherein the top layer comprises one of an extruded polymer, an aqueous material, and mixtures thereof.

12. The method of claim 1, wherein the top layer comprises a printable surface.

13. A method of producing a packaging material, comprising the steps of: providing a web of paperboard; providing a release film with a metal deposit applied to a first surface thereof; extruding one or more polymer layers onto the metal deposit; applying the metallized release film to the paperboard, such that the metal deposit adheres to the paperboard via the one or more extruded polymer layers; removing the release film from the metal deposit; and applying one or more top layers to the metal deposit.

14. The method of claim 13, wherein said one or more top layers comprises an extruded polymer, an aqueous material and mixtures thereof.

15. A system for manufacturing a metallized packaging material, comprising: a lamination station for laminating a metallized release film to a paperboard substrate, wherein the metallized release film comprises a release film having a metal deposit on a first surface thereof; a stripping station for removing the release film from the metal deposit after the metallized release film is laminated to the paperboard; and a finalizing station for applying a top layer to the metal deposit after the release film is removed.

16. The system of claim 15, wherein the top layer comprises an extruded polymer material and the finalizing station comprises an extrusion die for extruding a polymer material onto the metal deposit to form the top layer.

17. The system of claim 15, wherein the top layer comprises an aqueous material and the finalizing station comprises a coating station for applying the aqueous material to the metal deposit and a drying station for drying the aqueous material.