NZ203578A - Heat-shrinkable plastics hang bag:hanging loop of non-heat shrinkable,heat sealable material - Google Patents

Description

203578 Priority Date^-: .. I ?r Complete Specification Fifed: .IP.7.3-RS Ctess: . .£&?>.) JP>...

I ■ ■ • ■ » • • t i r • i i • ■ , t , [ Publication DcrtG: J. J$86 I P.O. Journal, No: ,, ,133^? N.Z. PATENT OFFICE 2 9 JUL 1983 No.: Date: NEW ZEALAND PATENTS ACT, 1953 COMPLETE SPECIFICATION "HANG BAGS" X/We, W. R. GRACE & CO., a corporation organized and existing under the laws of the State of Connecticut, United states of America, of 1114 Avenue of Americas, New York, N.Y. 10036, United States of America, hereby declare the invention for which £ / we pray that a patent may be granted to box/us, and the method by which it is to be performed, to be particularly described in and by the following statement:- 203578 FIELD OF THE INVENTION This invention relates to thremoplastic bags which may be filled and hung from a peg board display in a supermarket. More particularly, the invention relates to side-seal thermoplastic bags which are heat shrinkable and are used to package processed meat and cheeses which are displayed for retail sale.

BACKGROUND OF THE INVENTION In retail grocery stores and supermarkets many of the processed meat and cheese packages are hung on peg boards for better display for the customer. In order to provide a hang up feature there are a number of alternatives to consider. Straps or hooks could be used which could be fixed to the finished package in a retail stores, e.g., a strip of semi-rigid plastic with a hook on one end; or, cutouts ofp aper which can be shaped into a cone or a strap to hold a filled bag may be used. Another type of hang up feature consists of punching holes at either end of the bag and reinforcing the hole with metal or plastic eyelets in order to provide a sufficiently strong hanging means. Still another, type of feature is a loop or strap sealed to a bag at the time the bag is made. It is this last feature with which this invention is concerned.

In United States Patent No. 3,207,300 which issued on September 21, 1965 to H. L. Farmer, a labelled package is shown which 1 N.Z. PATENT OFFiCE 2 9JUL 1983 . 20357% jjS^ contains semi-rigid articles with a wrapper of heat-sealable and shrinkable plastics film is disposed within the wrapper and extends transversely of the articles with the opposite ends of the strip respectively secured within heat seals. However, the strip shrinks with the wrapping and a loop is not left so that a hang strap is formed. Accordingly, it is one object of the present invention to provide a package with a shrinkable wrapper and a non-shrunk strip or strap which can be used as a hanging feature.

For packaging many food products, especially fresh meats or processed meats it is quite desirable to use a wrapping material which has low oxygen permeability. One such material is described in United States Patent No. 3,741,253 which issued to H. J. Brax et al on June 26, 1973. In the Brax et al patent a packaging film having a first layer of a cross linked ethylene vinyl acetate copolymer is described which is extrusion coated with a layer of a vinylidene chloride copolymer which in turn is extrusion coated with another layer of ethylene vinyl acetate copolymer. In using a bag which is made from film according to the Brax et al patent if the strap is sealed to the non-crosslinked vinyl acetate polymer layer, it was found that grease would attack the strap seals and the seal would fail at either instantly or either a short time after a filled bag was hung by the strap. Accordingly, it is another object of the present invention to provide a hang bag which is useable with a grease containing product and which will hang at retail display for an extended period of time.

N.Z. PATENT OFFICE 2 9 JUL 1983 203S7S The foregoing and other objects will be better understood with reference to the summary of the invention, the drawings, and the detailed description which follows.

SUMMARY OF THE INVENTION In one aspect, the present invention is a hang bag which comprises a bag portion which includes front and back panels of multilayer, heat shrinkable, thermoplastic sheet material wherein at least two layers of the multi-layer material have been coextruded, said panels comprising a single sheet folded so that the fold comprises the bottom of the bag, the edges on each side of said panels being sealed to the respective opposite side edge in parallel side seals leaving an unsealed side defining the top of the bag with an opening for loading the product into the bag; and, a strap of non-heat shrinkable, heat-sealable material, one end of said strap being sealed to one side.seal and the other end to the other side seal whereby when the bag is heated and shrunken it shrinks away from the strap forming the strap into a loop for hanging the bag.

In another aspect, the invention is a hang bag wherein it is not necessary that two layers of the mult-layer film be coextruded but it is necessary that the strap comprise superimposed strips of heat-shrinkable and non-shrinkable material, the shrinkable strip being next to or in contact with the bag.

N.Z. PATENT OFFICE 2 9 JUL 1983 RECEIVED 203Sit In still another aspect, the present invention is a package for hanging display comprising a product, a multi-layer, side-seal, thermoplastic bag shrunken about the product, the material from which said bag is constructed comprising a multi-layer film in which at least two layers of the film have been coextruded, and a hang loop comprising a non-heat-shrinkable strap of heat-sealable thermoplastic material, one end of said strap being sealed at one of the side seals to the outer surface of one layer of said coextruded material and the other end of the strap being sealed at the other side seal to the outer surface of one of the coextruded layers.

In still another aspect, the present invention is a method of making hang bag which comprises providing a flattened, heat-shrinkable thermoplastic tubingwvherein the material for which the tubing is made is multi-layer and the layer comprising the outside surface of the tubing has been coextruded with its adjacent layer, slitting the flattened tubing at or adjacent to one longitudinal edge, superimposing a strip of non-shrinkable material over said tubing, passing said tubing and said superimposed strip through sealing and perforating means which are arranged to make two successive transverse seals with perforations there-between at spaced apart intervals along the length of said tubing parallel to each other; sealing said flattened tubing to itself and to said strip with the sealing means to form a side seal bag with the strip sealed in the respective side seals with perforations between the seals; and, separating the bags from each other along the perforations to form side seal bags.

N.Z. PATENT 0:T!CE 2 9 JUL 1983 RECEtVrb 20ZS7Z DESCRIPTION OF THE DRAWINGS The invention may be better understood with reference to the accompanying drawings in which: Figure 1 is a schematic representation of the process of tubing and strap material being made into a side-seal hang bag; Figure 2 is a perspective representation of unfilled, unshrunk hang bag according to the present invention; Figure 3 is a representation of a filled and shrunken bag according to the present invention showing the unshrunk hang loop; and, Figure 4 is a representation of packages according to the present invention being displayed on a peg board at a retail supermarket.

DETAILED DESCRIPTION Turning now to Figure 1, roll 1 of flattened tubing 2 is shown being guided over guide roll 3 and through sealing and perforating means 4. The flattened tubing is preferably made from multilayer, thermoplastic film having low oxygen permeability and such film is described in the above mentioned Brax et al patent. Another preferred film is one in which a substrate layer of ethylene vinyl acetate copolymer containing approximately % vinyl acetate is extruded and crosslinked by irradiation and is subsequently extrusion coated with two coextruded layers. The two coextruded layers being molten N.Z. PATENT OFFICE 2 9 JUL 1983 RECEIVED 20557* and being extruded onto the substrate at the same time is, in effect, very much the same as extrusion coating with one layer. The two coextruded layers that make up the extrusion coating are a vinylidene chloride copolymer layer of the type disclosed in the Brax et al patent and a layer of ethylene vinyl acetate copolymer having approximately 9% vinyl acetate. The vinylidene chloride copolymer layer contacts the substrate and the ethylene vinyl acetate copolymer layer is on the outside. Thus, again considering Figure 1, the outside surface of the flattened tubing 2 comprise uncrosslinked ethylene vinyl acetate copolymer and the inner surfaces of the tubing which are in contact with each other comprise crosslinked ethylene vinyl acetate copolymer. This tubing is preferably slit at the side edge opposite that where strip 8 is being applied from roll 7 and the slit edge, of course, will provide the mouth or opening to the completed bag. Slitting apparatus are well known in the art and are not shown.

As the slit tubing enters the sealing apparatus the strip of strap material 8 has been laid on top of the tubing. This strap material 8 is preferably made from low density polyethylene or from ethylene vinyl acetate copolymer and has not been oriented or stretched to render it heat-shrinkable to any appreciable extent. It must, of course, be a thermoplastic material which is heat-sealable and can be sealed with the tubing material in the sealing means 4. A typical width of this strap material is 25mm. or about one inch.

The width of the flattened tubing will vary according to the product to be packaged in the finished side seal bag but a typical 203S7S- - .8 - width of the flattened tubing is 10 to 12 inches or 25 to 30 centimeters.

The sealing means 4 can be any commercial seal and sever apparatus. These are well known in the art and typically would comprise an electrically resistant wire which when given a pulse of electric current will be heated to a sealing temperature as the opposed members of sealing means 4 press together upon the tubing through strap 7. The sealing means 4 actually has two sealing wires to form spaced apart seals 5 and, in addition, the sealing means has perforation means to punch perforations 6 into the flattened tubing 2 and strap 8. The perforations are typically 21/? to'3" apart and the dwell time when the sealing members close to form the side seals will be in the order of 1/4 to 1/2 second. In Figure 1 after the sealing and perforating has been accomplished a flattened side seal bag 9 results which is still attached to the trailing bags which are being made by the sealing means 4. A side seal bag is generally considered to be one in which at least one side is closed by a seal and the bottom is formed by a fold.

Turning to Figure 2, bag 9 has now been separated from the tubing and is ready to be filled. Filling can be manual or can be accomplished by any number of means, and a great variety of products, particularly food products such as meat and cheese can be inserted in the mouth of the bag which is at the end opposite strap 8. In the typical example being described herein, a 500 gram chub of process meat such as sausage is placed in the bag the bag evacuated by any 2 9 JUL1983 received m 203 S78 number of means well known in the art such as vacuum chamber means or vacuum nozzle means and the mouth of the bag is heat sealed. One suitable machine is the model 8300 rotary vacuum machine sold by the Cryovac Divisior of W R Grace & Co. of Duncan, South Carolina, U.S.A. A heat seal similar to that applied by the impulse sealing means 4 can be used or a metal clip can be applied. After the final closure seal has been applied, the filled bag is placed briefly in water heated in the range of 185 to 205°F to shrink the unsealed bag 9 tightly around the meat chub so that the package has the appearance shown in Figure 3 where the bag 9 has shrunk and the strap material 8 has not thereby leaving loop 8 for hanging purposes.

In Figure 4 a display pegboard 10 common to many supermarkets is shown having a peg 11 from which filled bags or packages 9 are hung by loop 8.

It was discovered that when a single layer strap was applied to multi-layer bag material which had not been coextruded that grease from the packaged product would attack the strap seals at elevated temperatures, such as the heat shrink temperature, and would cause the outer ply of the bag to delaminate.

It was surprisingly discovered that the delamination problem could be solved by coextruding at least two other layers of the multilayer film form which the bag is made, one of these layers being the layer to which the ends of the strap 8 are heat sealed.

In a test to determine the reliability of the hang loop of this invention, peanut oil was applied to the inside of bags before TENT OFFICE 2 9 JUL 1983 T-ccsived packaging meat and then the bag was hung by the loop at 32°C. The non coextruded bag structures were found to fail either instantly or only after a very short time when subjected to this test with a 500 gram product. On the other hand, bags with the coextruded structure containing 500 grams of meat chub therein were hung from the strap both at chiller temperatures (8°C) and at room temperature. No failures were discovered in hanging trials lasting up to 30 days.

In addition to discovering that the coextruded structure surprisingly solved the strap failure problem it was found that if a relatively wide band, approximately 2" wide, of heat shrinkable film such as heat shrinkable polyethylene was applied to one side of the tubing and then the unshrinkable strap was sealed on top of the shrinkable film that a successful hang bag would result. It was theorized that the wide band of shrinkable film which shrinks with the tubing from which the bag is made distributes the forces in the strap over a longer length of the outer ply of the bag material. This type of construction can be made as shown in Figure 1 by applying a two layer strip of strap material 8 from a roll 7 wherein the first layer is a thermoplastic heat shrinkable material and the second layer superimposed over the first is a non-shrinkable material which will be the hang loop. As described herein above the two layer strap material 8 would be applied in the same fashion as the single layer but when shrunk the shrinkable ply or layer shrinks with the bag material and the non shrinkable material does not thus forming the hang loop as before. The width of the hang loop will be about 25mm. as before and the width of the shrinkable film will be about 2 inches or about 5 cm. m 203578 -11 As mentioned above, one of the principal objects of the present invention is to provide a hang bag in which the material is both heat shrinkable and is one which has low gas permeability. Hydrolyzed ethylene-vinyl acetate copolymer when used as a layer in a multi-layer film provides excellent resistance to gas transmission, and, in the Brax et al patent it is stated that vinylidene chloride copolymers provide excellent resistance to the transmission of oxygen and other gases but that monolayer films of vinylidene chloride copolymers do not have the abuse resistance necessary to stand up to commercial distribution practices. Thus, the Brax et al patent discloses the discovery of a multi-layer film which includes a layer of vinylidene chloride copolymer in a unique combination of heat shrinkable, abuse resistant materials; and, in the present invention, it is desirable to use such a multi-layer film as disclosed in Brax et al, but the application of strap material to such a multi-layer film in a high speed bagmaking process resulted in an unacceptable failure rate when products containing grease were packaged in the bags and shrunk at elevated temperatures. The solution to this problem, which can be expected to occur in other multi-layer films used to package grease containing foods, e.g., fresh meat, smoked, cured and process meats and cheese, has been described above and is summarized in the claims below in which:

Claims (16)

- 12 - 203578 WHAT HE CLAIM IS:

1. A heat-shrinkable hang bag having low oxygen permeability comprising: (a) a bag portion comprising: (i) front and back panels of multi-layer, heat shrinkable thermoplastics sheet material havin9 at least two layers which have been co-extruded: (ii) said panels comprising a single sheet folded so that the fold comprises the bottom of the bag and, (iii) each side of each of said front and back panels being sealed to the corresponding side of the other panel along their side edges in parallel side seals leaving a side unsealed thereby defining the mouth of the bag for loading a product into the bag and, (b) a strap of non-heat shrinkable, heat sealable material, one end of said strap being sealed to one side seal and the other end to the other side seal, the bag being heated so that it shrinks away from the strap, the strap thus being formed into a loop for hanging the bag. - 13 - 203578

2. The hang bag of claim 1 wherein the multi-layer film of the bag comprises three layers, the layer forming the inside surface of the bag being a crosslinked ethylene vinyl acetate copolymer, the middle layer being a vinylidene chloride copolymer, and the outside layer being an ethylene vinyl acetate copolymer, said middle and outside layers having been coextruded onto said inside layer.

3. The hang bag of claim 1 wherein said strap is positioned adjacent the bottom of the bag.

4. A heat-shrinkable hang bag having low oxygen permeability comprising: (a) a bag portion comprising: (i) front and back panels of multi-layer heat shrinkable thermoplastics sheet material having at least two layers which have been co-extruded (ii) said panels comprising a single sheet folded so that the fold comprises the bottom of the bag and (iii) each side of each of said panels being sealed to the other side panel along its opposed respective side edges in parallel side seals leaving an unsealed side defining the mouth of the bag for loading the product into the bag; and, x4 APR 1966 - 14 - 203578 (b) two superimposed straps, one strap being heat shrinkable and the other strap being of non-heat shrinkable heat sealable material, the heat shrinkable strap being in contact with the surface of the bag whereby the bag is heat shrunk so that the shrinkable strap shrinks with the bag and away from the unshrinkable strap thereby forming the non-heat shrinkable strap into a loop for hanging the bag said straps being sealed at one end to one side seal and at the other end to the other side seal.

5. The hang bag of claim 4 wherein said straps are positioned adjacent the bottom of the bag.

6. A package for a hanging display comprising: (a) a product; and (b) a heat shrinkable hang bag as defined in Claim 1 at least partially filled with said product and wherein the side defining the mouth of the bag is sealed.

7. The package of claim 6 wherein the material from which said side seal bag is made comprises at least three layers, at least two of 20,3578 - 15 - which have been coextruded, and at least one of which is selected from the group consisting of vinylidene chloride copolymers and hydrolyzed ethylene vinyl acetate copolymers.

8. The Package of claim 6 wherein the product is selected from the group of foods consisting of fresh meat, smoked, cured and processed meats, and cheese.

9. The package of claim 6 wherein the loop is located adjacent the bottom of the bag.

10. A package for a hanging display comprising: (a) a product; and (b) a heat shrinkable hang bag as defined in Claim 4 at least partially filled with said product and wherein the side defining the mouth of the bag is sealed.

11. The package of claim 10 wherein the shrinkable and non-shrinkable straps are located adjacent the bottom of the bag.

12. The package of claim 10 wherein the product is selected from the food group consisting of fresh meat, smoked, cured, and processed meat, and cheese.

13. A method of making a hang bag comprising the steps of: (a) providing flattened, heat shrinkable, thermoplastics tubing, said tubing comprising a multi-layer ther- ;f ~4APR?9863 ... 7?.;f - 16 - 203578 neoplastics film having at least two layers which have been co-extruded; (b) slitting said flattened tubing along one of its edges; . (c) superimposing a strap of non-heat shrinkable heat sealable material said tubing; (d) passing said tubing and superimposed strap through sealing and perforating means to make successive seals transverse across the width of said tubing, said seals being parallel to each other; (e) applying said sealing means to form a side seal bag with the ends of the strap sealed in;the side seals and, (f) filling, closing, and heat shrinking the bag whereupon the strap becomes a hang loop as the bag shrinks away from the strap.

14. The method of claim 13 including locating the strap adjacent the end of the bag away from the mouth.

15. A heat-shrinkable hang bag having low oxygen permeability substantially as hereinbefore described with reference to the accompanying drawings.

16. A method of making a hang bag substantially as hereinbefore described with reference to the accompanying drawings. DATED THIs3fo( DAY 0F P*Pf ( ^ A' J^PAPJS & S0N