CA2131676A1

CA2131676A1 - Laminated insulating packaging material with metallized film

Info

Publication number: CA2131676A1
Application number: CA002131676A
Authority: CA
Inventors: Robert T. Snodgrass; C. David Desjardins
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-09-08
Filing date: 1994-09-08
Publication date: 1996-03-09

Abstract

A laminated insulating panel for use in packaging perishable goods that require controlled temperatures during shipping has an inner honeycomb core made of water-resistant paper, with facing layers of metallized polymer film and paper. The panel is made into liners and drain trays for shipping cartons.

Description

21~67 B

LAMINATED INSULATING PACKAGING MATERIAL
WITH METALLIZED FILM

FIELD OF THE INVENTION
The invention is directed to a new packaging material for perishable goods that require controlled temperatures during shipping. In particular, it is directed to a panel formed by laminating a paper honeycomb structure with metallized polymer film, and to carton liners made from such panels.

BACKGROUND OF THE INVENTION
Over the last decade, there has been a dramatic increase in the worldwide shipment of perishable foodstuffs that must be maintained at low temperatures during shipping.
For example, fish caught one day in the eastern Atlantic Ocean can be found in a fish market in Tokyo 48 hours later.
In these circumstances, there has been an on-going and increased need for improved insulating packaging materials suitable for such goods. Also, there is an increasing demand that packaging materials be made from recycled materials, reusable and of reduced volume. Expanded polystyrene (EPS) has been used for many packaging applications; however it is relatively bulky and cannot readily be recycled. U.S. Patent 5,230,941 Hollander et al.
describes an insulating material comprising a honeycomb structure laminated to layers of aluminum foil; however, such structure suffers from the disadvantage that aluminum ~3167G

foil is susceptible to tearing and puncture by sharp objects and the structure cannot stand up to the rigors of high moisture conditions present in the shipment of refrigerated goods, especially in the presence of ice and ice melt. It is also difficult to recycle. There is accordingly a long-felt need in the packaging industry for an insulating packaging material for shipping refrigerated perishable goods, which is strong and lightweight, resists tearing and puncturing, withstands the presence of high moisture, can be fabricated from recycled materials and can be reused.

SUMMARY OF THE INVENTION
The invention provides a laminated insulating structure, referred to herein as a panel, for use in the packaging of refrigerated goods. The panel can be cut into desired sizes and scored and folded as required without puncturing, to make liners, sleeves, panels, drain trays and other interior packaging components of shipping cartons or boxes. The laminated insulating panel has a honeycomb core with a facing layer bonded to each side, forming sealed airspaces in the honeycomb. The facing layers comprise a polymer film with one metallized surface and a layer of paper or of polymer bonded to the metallized side of the film. Each facing layer may be bonded by either side thereof to the honeycomb, i.e. by the polymer film side or by the paper or polymer side. The paper that is used in the insulating panel is treated to impart strong water resistance thereto.

~131676 A drain tray fabricated from the laminated insulating panel is used in the bottom of a shipping carton.
A rectangular panel is punch scored along two opposite sides and folded along the scores to form a middle section and two downwardly-projecting support sections. The support sections rest on the bottom of the carton, providing an airspace, into which water can drain, between the middle section, on which the perishable goods are placed, and the bottom of the shipping carton.
BRIEF DESCRIPTION OF THE DRAWINGS
In drawings which illustrate embodiments of the invention, Fig. 1 is a plan view, partly cut away, of one embodiment of a panel in accordance with the invention;
Fig. 2 is a cross-section on the line 2-2 of Fig.1;
Fig. 3 is a perspective view of a shipping carton with a set of liners made in accordance with the invention;
and Fig. 4 is an end view of a drain tray for use in the bottom of a shipping carton.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in Figs. 1 and 2, the panel 2 has a honeycomb structure 4 laminated between an upper and a lower facing layer. The honeycomb structure 4 is formed of elongated strips of paper folded and glued to one another Z13~67G

along sections 6 to form a series of generally hexagonal cells 8 with walls 10. Cells 8 form sealed airspaces within the panel 2 when the upper and lower layers are laminated to the honeycomb structure. The honeycomb structure 4 is made of paper of a size and strength suitable for a given packaging application. The term "paper" as used in the specification includes a variety of paper materials, including cardboard and kraft paper.
The paper used for the honeycomb and in the facing layers of the panel is preferably treated to impart strong water resistance thereto, a treatment referred to as "hardsizing" in this specification. An example of a suitable hardsizing agent is alkylketene dimer (AKD).
Formulations including AKD are supplied by Hercules Incorporated of Wilmington, Delaware under the trademark HERCON. For the purposes of the invention, paper treated to give Cobb test values lower than 60g/m2in a 30-minute Cobb test done in accordance with TAPPI T441 is satisfactory.
The panel 2 has two facing layers 5, 7 laminated to the honeycomb structure 4. The upper and lower layers are preferably identical. Referring to Fig. 2, the upper facing layer 5 has a polymer film 12 having a metallized coating 16 on its inner surface. The film 12 is bonded by its metallized side to a paper or polymer layer 20.
Similarly, the lower facing layer 7 comprises polymer film 14 with metallized coating 18, bonded to paper or polymer layer 22. The paper or polymer layers 20, 22 are bonded to the walls 10 of the honeycomb structure 4 so the walls 10 are substantially perpendicular to the upper and lower facing layers.
The polymer films 12, 14 are made of any suitable polymer material, such as polyethylene or a polyester. A
film thickness of about .005 inches is suitable for most applications of the invention.
The metallic coating 16, 18 is preferably aluminum having a thickness between 75-300 Angstroms. The coating is typically applied to the polymer film by vacuum metallizing, a process well known in the coating art. Metallized films suitable for the invention are described in U.S. Patent 4,999,222 Jones et al. The metallized film should have low emissivity in order to be a good radiant barrier. Typical emissivities for metallized polymer films suitable for use in the invention are less than about 0.05. Polymer films of .0048 inches thickness having a utility grade aluminum coating 275 Angstroms thick with a basis weight of 12.2 lbs aluminum per 3000 sq. feet have been found suitable.
The paper/polymer layers 20, 22 impart strength to the facing layers and can be made of paper, hardsized for water resistance as described above, or a polymer, such as polyethylene or a polyester. The paper/polymer layers 20, 22 are bonded to the metallized side of the polymer films 12, 14 respectively. The facing layers 5, 7 are bonded by the paper/polymer layers to the top and bottom edges of the walls 10 of the honeycomb 4.
In the embodiment illustrated in Fig. 2, the paper/polymer layers 20, 22 are bonded to the honeycomb;

213~676 however, in another preferred embodiment in which layers 20, 22 are paper, the facing layers are bonded by their polymer films 12, 14 to the honeycomb so the paper layers 20, 22 face outwards. Alternatively, one paper layer may face outwards and the other may be bonded to the honeycomb, thus facing inwards.
The bonding together of the walls of the honeycomb structure and of the facing layers may be done by conventional means such as gluing or pressure sensitive masking. The adhesives used should meet the indirect food contact code 175.105 specified by the U.S. Food and Drug Administration. Preferably the honeycomb core adhesive is based on a mixture of more than two polymers from the family of polymers comprising polyvinyl acetate and its co-polymers, including polyvinyl acetate, ethylene vinyl acetate, vinyl acrylic and polyvinyl alcohol. The preferred adhesive for bonding the walls of the honeycomb structure together is a film-forming vinyl acetate acrylic co-polymer that has been compounded to increase water resistance and specific adhesion. A preferred adhesive for laminating the honeycomb structure to the facing layers is a film-forming acrylic polymer that has been compounded to increase water resistance and specific adhesion. Suitable adhesives and their preparation will be apparent to persons skilled in the art.
To fabricate insulation liners from the panel described above, the panel is cut into pieces of desired sizes for a given carton. To make folded liner components, 213~67~

the panel is scored for folding by pressing a round-edged blade against one side of the panel without cutting or puncturing the polymer films. The width and depth of the score required to permit satisfactory folding depend on the thickness and strength of the panel. A score made in accordance with this method is referred to herein as a "punch score".
As shown in Fig. 3, a preferred configuration of liners is a flat rectangular panel 40 for the bottom of the carton 42, a collar panel 44 having three parallel punch scores 46, 48, 50 for folding into a four-sided liner for lining the four side walls of the carton, and a flat top rectangular panel. The collar panel can be configured in various ways; for example, it can have four punch scores and be folded so the ends join along a side of the carton rather than at a corner; or it can be in two or more separate sections.
A drain tray is preferred instead of a flat bottom panel where ice is used in the carton for refrigeration, in order to permit water drainage. As shown in Fig. 4, the drain tray has two parallel punch scores 24, 26, one near each of two parallel sides of the panel. The edge sections 28 and 30 are folded downwards at right angles to the middle section 32, the drain tray rests on edges 34, 36 on the bottom of the carton, providing a space under the middle section 32 to permit ice melt to drain away from the refrigerated perishable goods.

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The panel thickness is selected to be appropriate for a particular packaging application. A thickness of about 1/2 inch is generally suitable for most applications, and can be used as an alternative for EPS liners of 1 inch thickness. This volume reduction in packaging material permits more goods to be loaded in a carton of the same dimensions. A panel thickness of 3/4 inch or 1 inch is preferred for some applications, such as packaging whole tuna. The diameter of the cells in the honeycomb core is selected to be suitable for the particular packaging application. Cells of 1/2 inch are suitable for many applications.
The liners of the invention can be folded flat for shipping to users, and after use can be stored flat for reuse. They can be made from 100% recycled materials, namely paper, polymer and aluminum.

Claims

1. A laminated insulating panel for use in packaging perishable goods, comprising:
a planar honeycomb structure comprising a plurality of water-resistant paper strips each attached to adjacent paper strips and forming the sidewalls of generally polygonal compartments;
a first facing layer bonded to one side of said honeycomb structure and a second facing layer bonded to the other side of said honeycomb structure, generally perpendicular to the sidewalls thereof, said first and second facing layers each comprising (i) a polymer film having a metallized surface and (ii) a layer of water-resistant paper or of polymer bonded to said metallized surface, each of said first and second facing layers being bonded to said honeycomb structure by either said polymer film or said paper or polymer layer.

2. An insulating panel according to claim 1 wherein the emissivity of the metallized polymer films is less than about 0.05.

3. An insulating panel in accordance with claim 1 wherein the thickness of the polymer films is about .005 inches.

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4. An insulating panel in accordance with claim 1 wherein one or both of the polymer films are made of polyester.

5. An insulating panel in accordance with claim 1 wherein one or both of the polymer films are made of polyethylene.

6. An insulating panel in accordance with claim 1 wherein said metal is aluminum.

7. An insulating panel in accordance with claim 1 wherein the thickness of the metal coating is between 75 and 300 Angstroms.

8. An insulating panel in accordance with claim 1 wherein the paper walls of said honeycomb structure are hardsized using alkylketene dimer.

9. An insulating panel in accordance with claim 8 wherein said paper walls have a Cobb test value less than 60 g/m for a 30 minute test.

10. A panel in accordance with claim 1 having at least one punch score therein to permit the panel to be folded along said punch score, said punch score being made by pressing a blade against a side of the panel without cutting or puncturing the metallized polymer films.

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11. A drain tray fabricated from the panel of claim 1 for use in the bottom of a shipping carton, said drain tray comprising a rectangular member having two or more punch scores therein parallel to two opposite edges thereof for folding said member along said punch scores to form a middle section and two downwardly-projecting support sections, whereby an airspace is provided between said middle section and said bottom of said shipping carton.

12. A laminated insulating panel for use in packaging perishable goods, comprising:
a planar honeycomb structure comprising a plurality of water-resistant paper strips each bonded to adjacent paper strips and forming the sidewalls of rounded hexagonal compartments:
a first facing layer bonded to one side of said honeycomb structure and a second facing layer bonded to the other side of said honeycomb structure, generally perpendicular to the sidewalls thereof, said first and second facing layers each comprising (i) a polymer film having a surface metallized with aluminum and (ii) a layer of water-resistant paper bonded to said metallized surface, each of said first and second facing layers being bonded to said honeycomb structure by said paper layers; said bonding of said paper strips and of said facing layers being by means of adhesives suitable for indirect contact with foodstuffs, said paper having Cobb test values lower than 60 g/m in a 30 minute Cobb test done in accordance with - Page 3 of Claims -TAPPI T441, said facing layers being sufficiently strong that said panel can be punch scored and folded along said score without puncturing or cutting said polymer films.

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