Plastic bag for vacuum sealing

Abstract

A plastic bag for vacuum packaging comprises an inner layer of heat sealable thermoplastic material which incorporates interconected air channels on its inner surface and an outer layer of gas impermeable material. Optionally, one or more intermediate layers may be included between the inner layer and the outer layer. The inner layer and the outer layer, and any intermediate layers, are joined together such that no air pockets exist between the inner layer and the outer layer.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No. 009,110 filed Jan. FIG. 6 is an enlarged perspective view illustrating the inner structure of a bag panel that has an intermediate layer in accordance with the present invention.

FIG. 7 is a cross-sectional view illustrating the structure of a plastic bag with an intermediate layer in accordance with the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 shows a plastic bag 10 with a nozzle 12 from a vacuum pump inserted into its open end. The nozzle 12 is of a flat, tapered design so that the bag 10 can be held air-tight around the nozzle by means of hard foam rubber clamps 14 which are held tightly together for this purpose.

The has been made to carry a design created by thickness variations in such a way that channels 20 are formed in the areas of reduced thickness 28 17 while the islands 30 form the contact area with the opposite bag side. The outer layer 18 is flat and joined over its entire surface with the outer flat surface of inner layer 16. The opposite side of the bag 10 is, in this case, a flat compound film made of corresponding layers 16' and 18'.

As stated above, the inner layer 16 is, preferably, polyethylene, which is food safe but does not constitute an oxygen barrier. It also is not by itself boilable nor has it sufficient mechanical strength. In contrast, the outer layer 18, which preferably is made of polyester or polyamide (nylon), has good mechanical properties, is an excellent oxygen barrier, but need not be either food safe or heat sealable.

The plasticity temperature of the outer layer 18 typically is above 200°C, while that of the inner layer 16 is below 130°. When heat sealing clamps 22 heat the outer layer 18, heat is also transported to the inner layer 16 which is then heat sealed. Because of the substantially higher plasticity and melting temperatures of the outer layer 18, there is no danger of melting or puncturing the outer layer 18 during the heat sealing cycle which is designed for the inner layer 16.

In practical application, the wall thickness of the compound film is between 2.5 and 4.5 mils. The thickness of the gas impermeable outer layer 18 is approximately 0.5-1.0 mils (50-100 gauge), with the heat sealable inner layer 16 comprising the remainder of the thickness.

Referring to FIG. 3, according to a preferred embodiment of the invention, the outer layer 18' of the flat side of the bag 10 comprises polyester or nylon of a thickness of 0.5-1.0 mils. The inner layer 16' comprises polyethylene or polypropylene at a thickness of 1.5-3.0 mils. These films are laminated, coextruded or extrusion-coated to form a single transparent film such that the outer layer 18' and the inner layer 16' are joined together over their entire adjacent surfaces. For the channeled side of the bag 10, the materials and the joining of the outer layer 18 and the inner layer 16 are as described with respect to the flat side; however, the thickness of the channel side layers may be different and one or both layers may be opaque white.

The regular or irregular pattern of interconnecting air channels can be created during the co-extrusion or extrusion-coating processing of the multi-layer film, or it may be post-embossed, forming a corresponding pattern of ridges on the nylon/polyester side. The depth of these channels is typically not less than three times the film thickness. The embossing may be done on steel to steel or rubber to steel roller machines, the first being faster, but requiring very tight adjustment tolerances in order not to damage the firm film. The latter is slower, but more forgiving.

During post-embossing, the different plasticity and melting temperatures of the two adjacent layers 16 and 18 must be taken into consideration. Temperatures have to be high enough to allow the outer layer 18 of nylon or polyester to accept the pattern without tearing or damage, but not high enough to melt the inner layer 16. The available temperature range is extremely small and must be accurately monitored. Heat may be introduced through the rollers by hot air or infrared radiation. The later is quicker to react to adjustments and, thus, particularly suited for steel to steel roller machines.

The embossing process can be done with state of the art equipment provided special care is taken and the requirements of the multi-layer film are met.

The two films, i.e. the flat side consisting of outer layer 18' and inner layer 16' and the embossed side consisting of outer layer 18 and inner layer 16, are joined by means of heat seals along the edges of 8" or 11" wide strips with the heat sealable polyethylene layers facing each other, thus forming an open tube or an endless open bag. These endless bags are then cut and sealed across to any desired bag length or cut and rolled into 20" continuous bag rolls.

As stated above, the bag 10 may be constructed to include layers intermediate the heat sealable inner layer and the gas-impermeable outer layer so long as the layers are joined together over their entire adjacent surfaces such that no air pockets exist between the inner layer and the outer layer. In one such embodiment of the invention, the inner layer is low density, heat sealable polyethylene about 0.5-1.0 mils thick. An intermediate layer comprises high density polyethylene about 1.5 mils thick to impart stiffness to the bag structure. The outer, gas-impermeable layer is nylon about 0.5 mils thick. Thus, the multi-layer film which forms the bag, and which may be formed by co-extrusion of the three above-mentioned materials, is about 3.0-3.5 mils total thickness.

FIGS. 6 and 7 illustrate a bag with an intermediate layer 32 sandwiched between the inner layer 16 and the outer layer 18. FIG. 6 is a perspective view showing one panel formed from a three-layer film, with air channels 20 between and among the protuberances. FIG. 7 is a cross-sectional view of an assembled bag, where one panel is formed from a three-layer film.

It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the invention and that structures within the scope of these claims and their equivalents be covered thereby.

Claims

1. A tubular receptacle adapted to be formed into an evacuated and sealed bag comprising

first and second superimposed plastic panels, each having a uniform thickness and defining inner and outer surfaces thereon, joined together at opposite lateral sides thereof to define a chamber adapted to have a product disposed therein,

each of said first and second panels comprising an uniform inner layer, defining one of said inner surfaces thereon, composed of a heat sealable material, and an uniform outer layer composed of a gas impermeable material, and

a plurality of raised protuberances having said uniform thickness and formed in a generally regular and waffle-like pattern on the inner surface of at least one of said first and second panels to project outwardly therefrom towards the inner surface of the other panel to define a plurality of intercommunicating channels entirely around and between said protuberances.

2. The receptacle of claim 1 wherein said inner layer is composed of polyethylene or polypropylene.

3. The receptacle of claim 1 wherein said outer layer is composed of polyester or nylon.

4. The receptacle of claim 1 wherein said protuberances are solely formed on the inner surface of said first panel and the inner surface of said second panel is flat and uninterrupted.

5. The receptacle of claim 1 wherein distral distal ends of said protuberances and bottom surfaces defining said channels and which face the inner surface of said other panel each define at least generally flat and exposed surface areas thereon that are coplanar relative to each other.

6. The receptacle of claim 5 wherein each said exposed surface area is rectangular and each said protuberance and each said channel is trapezoidal, when viewed in cross-section.

7. The receptacle of claim 6 wherein each said exposed surface area is square.

8. The receptacle of claim 4 wherein said protuberances are further formed in said first panel to form a plurality of interconnected and raised ridges on the outer surface of said first panel that project outwardly therefrom to define said channels thereon and that further define a plurality of non-intercommunicating closed cavities between said ridges so that when the outer surface of said first panel is placed on a flat platen said cavities will not communicate with each other when air is evacuated through said channels.

9. The receptacle of claim 8 wherein outer surface areas of said ridges are at least generally flat and co-planar relative to each other.

10. The receptacle of claim 1 wherein the width and length of each of said protuberances are each at least approximately twice the width of each adjacent and surrounding

channel. 11. The receptacle of claim 1 further comprising an intermediate layer bonded between the inner and outer layers of said at least one of said first and second panels having said protuberances formed thereon, said intermediate layer composed of a material exhibiting a

stiffness greater than each of said inner and outer layers. 12. The receptacle of claim 11 wherein said inner layer is composed of low density polyethylene or polypropylene, said outer layer is composed of polyester or Nylon and said intermediate layer is composed of high density

polyethytlene. 13. The receptacle of claim 12 wherein said inner, intermediate and outer and intermediate layers have thicknesses of about 0.5 to 1.0 mil, 1.5 mil, and 0.5 mil, respectively.

. A tubular receptacle adapted to be formed into an evacuated and sealed bag comprising

first and second superimposed panels, each having inner and outer surfaces, joined together at opposite lateral sides thereof to define a chamber adapted to have a product disposed therein,

each of said first and second panels comprising an inner layer composed of a heat sealable material defining each said inner surface, and an outer layer composed of a gas impermeable material,

an intermediate layer bonded between the inner and outer layers of at least one of said first and second panels and composed of a material exhibiting a stiffness greater than each of said inner and outer layers, and

a plurality of protuberances formed in a generally regular and waffle-like pattern on the inner surface the one or more of said first and second panels, that includes said intermediate layer, to project outwardly from such inner surface towards the other panel to define a plurality of interconnecting channels entirely around and between said protuberances.

. The receptacle of claim 14 wherein said inner layer is composed of low density polyethylene or polypropylene, said outer layer is composed of Nylon or polyester and said intermediate layer is composed of high density

polyethylene. 16. The receptacle of claim 15 wherein said inner, intermediate and outer and intermediate layers have thicknesses of about 0.5 to 1.0 mil, 1.5 mil, and 0.5 mil, respectively.

. The receptacle of claim 14 wherein said protuberances are solely formed on the inner surface of said first panel and the inner surface of

said second panel is flat and uninterrupted. 18. The receptacle of claim 14 wherein distal ends of said protuberances and bottom surfaces defining such channels and which face the inner surface of said other panel each define at least generally flat and exposed surface areas thereon that are coplanar relative to each other.

19. The receptacle of claim 17 wherein said protuberances are further formed in said first panel to form a plurality of interconnected and raised ridges on the outer surface of said first panel that project outwardly therefrom to define said channels therein and that further define a plurality of non-intercommunicating closed cavities between said ridges so that when the outer surface of said first panel is placed on a flat platen said cavities will not communicate

with each other when air is evacuated through said channels. 20. A tubular receptacle adapted to be formed into an evacuated and sealed bag comprising

first and second superimposed plastic panels, each having inner and outer surfaces, joined together at opposite lateral sides thereof to define a chamber adapted to have a product disposed therein,

each of said first and second panels comprising an inner layer, defining one of said inner surfaces thereon, composed of a heat sealable material, and an outer layer composed of a gas impermeable material, and

a plurality of raised protuberances formed in a generally regular and waffle-like pattern on the inner surface of at least one of said first and second panels to project outwardly therefrom towards the inner surface of the other panel to define a plurality of interconnecting channels entirely around and between said protuberances, said protuberances having a width and length substantially greater than the width of each channel portion disposed between each adjacent pair of protuberances and each protuberance having an exposed surface area on a distal end thereof, directly facing the inner surface of the other panel, that is substantially larger than said channel portion when said protuberances and channels are viewed in plan view.