GB2251419A

GB2251419A - "Substantially leakproof package and method of forming same"

Info

Publication number: GB2251419A
Application number: GB9024762A
Authority: GB
Inventors: William Herr
Original assignee: ENVIRODYNE Ltd
Current assignee: ENVIRODYNE Ltd
Priority date: 1990-11-14
Filing date: 1990-11-14
Publication date: 1992-07-08
Also published as: GB9024762D0

Abstract

A package for products which contain a liquid includes a tray for the product, a film wrapped around the tray and product, and a heat-activated adhesive on at least selected areas of the tray bottom, whereby the film will seal to itself and to the tray bottom and the package will be substantially leakproof. The heat-activated adhesive may be applied to substantially the whole of the tray bottom or in strips in the form of tapes bearing the heat-activated adhesive and secured to the tray by pressure-sensitive adhesive. The invention also includes a method for forming such a substantially leakproof package. <IMAGE>

Description

"Substantially leakproof package and method of forming same" The invention relates to packages of the type in which a product in a tray is wrapped with a film Mbre specifically, it is a substantially leakproof package and a method of forming such a package.

In a typical prior art package and packaging technique the product is placed in a tray and covered with a plastics film such that the film totally encloses the tray and the product. Heat is applied to the bottom of the package.

Portions of the film which overlap such that contact is established therebetween adhere to fonti a seal.

Such packaging techniques are widely used in the food industry to package food products which include moisture.

Since the plastics film adheres to itself, a relatively leakproof seal is formed in areas where the film overlaps without wrinkles or excessive overlapping layers. Wrinkles and excessive overlapping layers adversely affect the sealing characteristics of the film, resulting in an increase in the number of packages which develop leaks.

Areas forming a good seal are usually concentrated in the central portion of the package. Areas near or adjacent the ends usually include excessive overlapping layers and wrinkles. Wrinkles and excessive overlapping layers change the sealing characteristics as a result of the formation of regions where no contact is established between overlapping layers of the film. Passages are formed along the wrinkles and between excessive overlapping layers which may extend from the interior of the package to the exterior of the package.

The inside surface of the film is typically treated to prevent the formation of water droplets. Condensation forming on the inside surface of the film tends to flow along this surface and through the passageways discussed above. As a result, the package leaks and must be removed fran the shelf before it is sold. Such leaks are particularly troublesome when food products such as fresh meats, poultry and seafood are to be packaged, due to the high moisture content of these products.

It is an object of the invention to provide an improved package in which sane at least of the disadvantages of prior such packages are reduced or eliminated. A further object is to provide a method of forming such an improved package.

The substantially leakproof package according to the invention, for a product containing a liquid, comprises:- (a) a tray for holding said product to be packaged, said tray including a substantially flat bottom portion surrounded by a perimetrical side wall to contain said product within the tray; (b) a layer of heat-activated adhesive applied to the exterior face of said substantially flat bottom portion in at least selected areas thereof within the regions of opposed edges thereof; and (c) a film of such a size as to extend over said product and underneath the tray and to contact at least said selected areas thereof; whereby, upon selective application of heat to said package, the heat-activated adhesive will be activated to seal said film to said selected areas and portions of said film will seal to each other, to form said substantially leakproof package.

The invention also includes a method for packaging a product containing a liquid, which method comprises the steps of: (a) placing the product in a tray having a substantially flat bottom portion and an upwardly extending perimetrical side wall surrounding said product; (b) applying a layer of heat-activated adhesive to the exterior face of said substantially flat bottom portion in at least selected areas thereof within the regions of opposed edges thereof; (c) placing over the product a film of such a size that the film extends beneath the tray, overlaps and contacts at least a part of said layer of heat-activated adhesive; and (d) selectively applying heat to the bottom of the resulting package to seal the film to itself and to the layer of heat-activated adhesive, whereby said package is made substantially leakproof.

The tray which is a feature of the novel package and method according to the invention may conveniently be formed of a moulded plastics material. It is preferably of polyvinyl chloride.

The heat activated adhesive may be applied to the tray in the form of strips of tape having a layer of the heatactivated adhesive on it. For example, the strips may be secured to the tray by a pressure-activated adhesive. As an alternative, the heat-activated adhesive may be applied to substantially the whole of the exterior face of the substantially flat bottom portion of the tray.

Thus in one erbodiment of the present invention, a strip of double-sided adhesive tape is affixed to the bottan surface of the tray adjacent the edges thereof using a conventional pressure-sensitive adhesive. The exposed surface of the tape includes a layer of a heatactivated adhesive. The product to be packaged is placed in the tray and the film is folded around the sides, around the ends and underneath the tray to totally enclose the tray.

Folding the film underneath the tray in this manner tends to form areas of multiple layer film and wrinkles. These multiple layers of film and wrinkles tend to be concentrated in regions of the bottom adjacent to or near the ends of the tray.

After the sides and ends of the film have been folded underneath the package, heat is applied to its under surface causing the film to adhere to itself where it overlaps and to the tape as the adhesive is activated. Along the central portion of the bottom of the package the film seals to itself and forms a relatively leak proof seal in a conventional fashion. Other portions of the film are sealed to the tray by the heat-activated adhesive. Areas where the film overlies the heat-activated adhesive and areas where the film overlaps are collectively referred to as the sealing zone.

In a second emkDdiment of the invention, the product to be packaged is placed in a tray and the entire bottom surface of the tray is coated with a heat-activated adhesive. A film is placed over the product and folded underneath the tray to totally enclose the tray. Wrinkles and excessive overlapping layers are formed, as discussed above. Heat is applied, causing the film to seal to the package along substantially the entire sealing zone as the adhesive is activated, thereby forming an essentially leakproof package.

In all embodiments of the invention, the film tends to be attracted by the adhesive when in the activated state.

Additionally, the adhesive tends to flows changing the contour of the adhesive layer to fill at least a portion of any space between the film and the tray. This stgnificantly reduces the number of passageways and forms a highly leakresistant package.

In practising the invention, the product may be placed in the tray, wrapped with film and heated to produce the seal using currently available equipment and materials. The adhesive tape and the adhesive layer may be applied to the bottom of the tray using any convenient technique.

It is a feature of the invention that it provides an improved leakproof package, which may readily be formed using currently available materials. By means of the use of a heat-activated adhesive, it becomes possible to reduce the number of passages along wrinkles and between excessive layers of the film.

The invention will now be further described with reference to the accanpanying drawings, which illustrate, by way of example only, two preferred embodiments of the improved package according to the present invention and wherein: - Fig. 1 is a perspective view, partly in cross-section, of the first embodiment; Fig. 2 is a perspective view fran below of the package of Fig. 1; Fig. 3 is a partially cross-sectional view of a portion of the package of Fig. 1; Fig. 4 illustrates the adhesive tape which is a feature of the package of Figs. 1 to 3; and Fig. 5 is a perspective view, partly in cross- section, of the second embodiment.

Referring firstly to Figs. 1 to 3, a conventional plastics tray 10 of the type frequently used to package fresh meats, poultry and seafood is used to support a product 12. Two strips of heat-activated adhesive tape 14 and 16 are affixed to the bottom surface of the tray 10 in areas adjacent opposed ends of the tray 10. A thin transparent plastics film 18 extends over the top surface of the product 12 and around the edges of the tray 10. The film is folded underneath to totally enclose the product 12 and the tray 10.

As the film 18 is folded underneath the tray 10, it extends over the bottom of the tray 12 and overlaps, making relatively wrinkle-free contact with itself and the bottom of the tray in the central portion of the tray, identified by the letter "A" in Figure 2. This region also tends to be relatively free of excessive overlapping regions, i.e.

regions of more than two overlapping layers. However, as the ends of the film 18 are folded underneath the tray 10, Tmiltiirlayers, wrinkles and excessive overlapping regions develop, which are typically concentrated near the opposed ends of the tray 10 as generally indicated at reference numerals 22 and 24 of Figure 2.

After the film 18 has been folded underneath the tray along both its sides and ends, heat is applied to the bottom of the package, causing the film 18 to adhere to itself, forming a relatively leak-proof seal along the central portion A of the package. Adjacent the ends of the package, portions of the film 18 in contact with itself seal together.

Additionally, portions of the film 18 in contact with the heat-activated adhesive on the outer surface of the adhesive tape strips 14 and 16 are sealed to the tapeforming a relatively leak'proof package. The surface of the adhesive tends to change contour to conform to the space between the film 18 and the surface of the adhesive tape, reducing the number of passageways between the interior and the exterior of the package, further improving the seal. In summary, a highly leak-resistant seal is formed over the entire sealing zone.

In Figs. 2 and 3, the wrinkling of the film along the end portions is clearly illustrated. Additionally, the heat-activated adhesive tends to change in contour and fill in the irregular spaces between the film and the tape 14, as previously described and generally illustrated at reference numeral 26. The thermally-activated adhesive may be BOSTIC TEERMDGPIP No. 6370, for example.

The heat-activated adhesive tape 14 is illustrated in Figure 4. Heat-activated adhesive tape strip 14 is also representative of the second strip of heat-activated adhesive tape 16. The tape 14 includes a suitable base member 30, which may be of paper or suitable plastic. The upper surface of the base 30 is coated with a layer of pressure-sensitive adhesive 32. A temporary peel-off protective layer of paper or other suitable material 34 is attached to the upper surface. A suitable heat-activated adhesive layer 36 is formed on the lower surface of the tape stock 30. A suitable tape can be made using currently available materials.

In practising the invention, the product 12 is placed in the tray 10 using conventional packaging techniques. The upper protective layer 34 is removed from two pieces of heat-activated adhesive tape to expose the pressure-sensitive adhesive. The two strips of heat-activated adhesive tape 14 and 16 are then positioned in the proper relationship on the package 10 and suitable pressure is applied between the tapes 14 and 16, causing them to adhere to package 10.

The plastic film 18 is then positioned around the product and sealed as previously described.

A second erixxlbaent of the invention is illustrated in Fig. 5. In this ieent, the product 40 to be packaged is placed in a tray 42. The bottom surface of the tray 42 is coated with a heat-activated adhesive. A suitable plastic film 44 is positioned over the product 40 and folded underneath the package as previously discussed with respect to the embodiment illustrated in Fig. 1. Heat is applied to the bottom surface of the package, causing the heat-activated adhesive to seal the film 44 to substantially all of the bottom surface of the tray 42, thereby forming a leak-resistant package. Sealing is further improved as the contour of the adhesive layer changes and tends to conform to the space between the film 44 and the tray 10. This results in a highly leak-resistant seal being formed across the entire sealing zone.

The package and packaging technique which is the subject of this invention may be implemented using a variety of commercially available components. If food products are to be packaged, it is obvious that all of the materials must be approved for use in food packaging and storage. Additionally, the heat-activated adhesive must have an activation temperature compatible with the film and the tray. Mbre specifically, the activation temperature of the heat-activated adhesive must be so selected that the film and tray are not damaged in the sealing process.

Claims

1. A substantially leakproof package for a product containing a liquid, which package comprises: (a) a tray for holding said product to be packaged, said tray including a substantially flat bottan portion surrounded by a perimetrical side wall to contain said product within the tray; (b) a layer of heat-activated adhesive applied to the exterior face of said substantially flat bottom portion in at least selected areas thereof within the regions of opposed-edges thereof; and (c) a film of such a size as to extend over said product and underneath the tray and to contact at least said selected areas thereof; whereby, upon selective application of heat to said package, the heat-activated adhesive will be activated to seal said film to said selected areas and portions of said film will seal to each other, to form said substantially leakproof package.

2. A substantially leakproof package as claimed in claim 1, wherein said tray is formed of a moulded plastics material.

3. A substantially leakproof package as claimed in claim 2, wherein said plastics material is polyvinyl chloride.

4. A substantially leakproof package as claimed in any of the preceding claims, wherein the heat-activated adhesive is applied to the tray in the form of strips of tape having a layer of said heat-activated adhesive thereon.

5. A substantially leakproof package as claimed in claim 4, wherein the strips of tape are secured to the tray by a pressure-activated adhesive.

6. A substantially leakproof package as claimed in any of claims 1 to 3, wherein the heat-activated adhesive is applied to substantially the whole of said exterior face of said substantially flat bottom portion of said tray.

7. A method for packaging a product containing a liquid, which method comprises the steps of: (a) placing the product in a tray having a substantially flat bottom portion and an upwardly extending perimetrical side wall surrounding said product; (b) applying a layer of heat-activated adhesive to the exterior face of said substantially flat bottom portion in at least selected areas thereof within the regions of opposed edges thereof; (c) placing over the product a film of such a size that the film extends beneath the tray, overlaps and contacts at least a part of said layer of heat-activated adhesive; and (d) selectively applying heat to the bottom of the resulting package to seal the film to itself and to the layer of heat-activated adhesive, whereby said package is made substantially leakproof.

8. A method as claimed in claim 7, wherein the tray is formed of a moulded plastics material.

9. A method as claimed in claim 8, wherein the plastics material is polyvinyl chloride.

10. A method as claimed in any of claim 7 to 9, wherein the heat-activated adhesive is applied to the tray in the form of strips of tape having a layer of said heat-activated adhesive thereon.

11. A method as claimed in claim 10, wherein the strips of tape are secured to the tray by a pressure-sensitive adhesive.

12. A method as claimed in any of claims 7 to 9, wherein the heat-activated adhesive is applied to substantially the whole of said exterior face of the substantially flat bottom portion of the tray.

13. A substantially leakproof package for a product containing a liquid, which package is substantially as hereinbefore described with reference to, and as illustrated in, Figs. 1 to 4 or Fig. 5 of the accompanying drawings.

14. A method for packaging a product containing a liquid, which method is substantially as hereinbefore described with reference to Figs. 1 to 4 or Fig. 5 of the accompanying drawings.