Package Closure

Abstract

A tape comprising two layers of flexible sheet material bonded together by pressure-sensitive adhesive. The outer surfaces of the sheet material are coated with a permanent-type adhesive such as a heat seal material. The tape is heat sealed between facing members of a package closure. Access to the package is gained by separating the sheet members and the package can be reclosed by means of the pressure-sensitive adhesive.

Parent Case Text

This is a continuation-in-part of my earlier U.S. Pat. application Ser. No. 795,586, filed Jan. 31, 1969, now abandoned.

Description

The present invention relates to a reclosable package and more particularly to a package having a pressure-sensitive adhesive closure. The invention is particularly useful for flexible bag packages and cardboard boxes, especially for food.

Many packages contain larger quantities of food than will be served at one time and it is necessary to store part of the food in the package after the package has been opened. For this purpose, many households are equipped with a variety of storage containers, made of glass, plastic and the like. However, enterprising food producers have found that consumers would prefer to buy food in packages which themselves may serve as storage containers. Therefore, a variety of packages have been produced which can serve as permanent receptacles, i.e., which are not rendered useless when the package is opened.

Such packages are more expensive and therefore increase the cost of the food they contain, which has reduced their use. In part this increase in cost results from the need to construct the package so that it can be opened and closed repeatedly. In part, reclosing of ordinary packages is made difficult because they are initially closed by means of a heat seal adhesive which is quite easy to apply in automatic packaging machinery. Unfortunately, the heat seal adhesive loses its adhesive properties once the package is opened, and therefore is not useful for reclosing the package.

It has been recognized that pressure-sensitive adhesives do not suffer this difficulty. However, they are difficult to use in automatic packaging machinery. A package to which such adhesive is applied will stick at least temporarily to almost any surface it contacts, because this kind of adhesive is permanently tacky, unlike heat seal adhesives which only become tacky when heated.

An approach to the problem is described in my earlier U.S. Pat. No. 3,272,422. In that patent, a closure was described having a coating of pressure sensitive adhesive, covered with a peelable film, the latter being heat sealed to a receptacle. The arrangement was such that, after heat sealing the closure to the receptacle, the closure could be opened by separating the pressure-sensitive adhesive from the peelable film. When the closure was replaced, the pressure-sensitive adhesive stuck to the peelable film, from which it could be separated again and to which it could be readhered repeatedly. This permitted reclosing the package numerous times.

I have now discovered a way to utilize the principles of the foregoing invention in certain types of conventional packages for which it was not originally well suited, and also for improving the ease of manufacturing packages having a pressure-sensitive adhesive reclosable seal. Briefly, this is accomplished by use of a tape comprised of two sheets of material, one side of each sheet being laminated to the other sheet by a pressure-sensitive adhesive with each sheet coated with a heat seal adhesive on its other side. The heat seal adhesive is selected to form a stronger bond with the package than the bond produced by the pressure-sensitive adhesive. The tape is applied between facing members of the closure of a conventional package which ordinarily are heat sealed to each other. The tape is useful in connection with a closure for flexible bags, cardboard boxes and the like. In one embodiment, the tape also is useful for facilitating opening of an adhesively closed package and for reinforcing the closure so that the package can be made of weaker stock.

The invention now will be described in detail in connection with preferred embodiments, reference being made to the drawings, in which:

FIG. 1 is a cross section of the tape;

FIG. 2 is a schematic view showing use of the invention with flexible pouches;

FIG. 3 is a cross section along lines 3--3 of FIG. 2;

FIGS. 4 and 5 are schematic views showing use of the invention with end-closed cartons;

FIG. 6 is a cross section of another embodiment of the tape;

FIG. 7 is a perspective view of a carton utilizing the tape of FIG. 6; and

FIG. 8 is a side elevation of the upper portion of the carton of FIG. 7.

As seen in FIG. 1, the tape utilized in this invention comprises two pieces of sheet material 1 and 2, adhered together with their outer surfaces 3 and 4 coated with layers of heat seal adhesive 5 and 6. The sheet 1 is coated with a pressure-sensitive adhesive layer 7 on the inner surface 8, which faces the sheet 2. The other sheet 2, in the embodiment shown, is coated with a release coating 9 on the inner surface 10, which faces the sheet 1. The pressure-sensitive adhesive layer 7 is adhered to the release layer 9, so that the two sheets form an integral article. It also is possible to apply pressure-sensitive adhesive to surface 10, so that the package is opened by prying apart two layers of pressure-sensitive adhesive. This gives a firmer bond, but is harder to open. Also, the same effect can be obtained by replacing the release coating 9 with a primer, described below, to which the pressure-sensitive adhesive bonds strongly.

The pressure sensitive adhesive may be any available pressure-sensitive adhesive mass, its composition not being an element of the present invention. It is well known to those skilled in the art that pressure-sensitive adhesive coatings possess a fourfold balance of tackiness, cohesion, elasticity and stretchiness. This balance is achieved for example in a blend of rubber and a resin, the rubber providing cohesion and elasticity and the resin providing tackiness and modification of stretchiness and elasticity. It also is known to use certain acrylate polymers in the mass, which inherently possess the necessary fourfold balance of properties. Materials of this type are readily available commercially, and manufacturers will provide information on materials to be used, taking into account the composition of the sheet 1 and the heat seal adhesive layers 5 and 6, as explained below. Where necessary, a primer coating may be used on the sheet 1, under the pressure-sensitive adhesive, to assure a firm bond. It also will be understood that, when food products are to be packaged, it may be necessary to take into account the toxicity of materials used.

Similarly the release layer 9 is a conventional material, which provides a surface to which the pressure-sensitive adhesive will adhere but from which it may be separated without delamination. Such materials commonly are applied to the back of pressure-sensitive adhesive tape which is sold in roll form, and to disposable release papers which sometimes are laminated to articles such as decorative wall coverings to temporarily cover a pressure-sensitive adhesive coating prior to use of the article.

The heat seal adhesive layers 5 and 6 are also composed of conventional materials. These include both thermoplastic and thermosetting types. The former are materials which reversably soften on heating and become firm again on cooling. "Thermosetting" refers to materials which tend to soften initially on heating but become irreversably hardened as heating continues. A wide variety of suitable materials are described in catalogs and elsewhere, for example, in Modern Packaging Encyclopedia. This adhesive forms stronger bonds with the package than the pressure-sensitive adhesive forms between the sheet material layers 1 and 2. Consequently, they remain sealed to the package but are separated from each other when the package is opened.

The tape can be used in several ways in packages. In one embodiment of the present invention the tape is used to close a plastic pouch. In this embodiment, the package may be a tube made by folding a flat film and sealing along a longitudinal seam 15 and at the ends, 16 and 17.

The formation of the package is illustrated schematically in the drawing. A flexible plastic film 18 is folded over a hollow die into a tube 19 which moves downwardly. The lower end is flattened and heated to form the seal 16, while at the same time forming the upper seal 17 of the preceding package. The seal along the seam 15 is formed by passing the seam along a heated member as the film and packages move downwardly. The top package shown in the drawing which is sealed only at the bottom, is filled through the hollow die around which the tube is formed. Then the tube moves down, and the just filled package is sealed at its top while the bottom seal 16 of the next package is formed. As seen at the top of FIG. 2, a tape 20 according to the present invention has previously been adhered to the flexible plastic film. That is, one of the layers of heat seal adhesive has previously been bonded to the film. The tape 20 is about one-half the width of the film and is adhered to the central portion of the film, the outer portions being sealed to the other layer of heat seal adhesive when the package is closed.

As seen near the bottom of FIG. 2, the lowermost package 21 is severed from those above, usually after the package immediately above has been sealed at its top. In this regard, it will be noted that a narrow band 22 of the tube 19 is left unsealed between the seals 16 and 17. The tube is slit at the top of this band, to sever the package 21. As seen at the bottom of FIG. 3, this provides tabs 23 and 24 which are easily gripped to facilitate opening the package.

The package thus produced is known as a pillow-type pouch, one web-vertical seam, top and bottom seams. However, the invention also may be used with other types of pouches, some of which are described in Modern Packaging Encyclopedia, 1968 issue, at page 211.

Another use of the invention is illustrated in FIGS. 4 and 5, in which a "Seal End" carton is closed. The carton comprises sidewalls forming a rectangular tube 50 closed at the bottom and is provided at the top with two side flaps 51 and 52 and two end flaps 53 and 54 which are all folded down to close the package. After the package is filled, say with popcorn, the end flaps (53 and 54) and one of the side flaps (52) are closed as the package is advanced by a conveyor (not shown). Then the tape 55 is pressed down against the folded flap 52. The tape is sealed to flap 52 by a heated roller 56 pressing against the upper surface of the tape. To prevent the tape from sticking to the roller, it may be coated with polytetrafluoroethylene (Teflon). Finally, the other side flap 51 is folded down and the tape is sealed to it by means of heated roll 57, as the package moves by. Knives indicated generally at 58 sever the portion of the tape between cartons.

Another embodiment of tape is shown in FIG. 6. This is a laminate of two sheet members 101 and 102 coated on their outer surfaces 103 and 104 with heat seal adhesive layers 105 and 106 respectively. About one-half of the width of the inner surface 107 of sheet 101 is coated with pressure sensitive adhesive and the corresponding portion of the inner surface 109 of sheet 102 is coated with a release layer 110. The other half of the sheet 101 is uncoated and the other half of sheet 102 also may be uncoated or it may be coated with release material. Thus, only half of the widths of the sheets 101 and 102 are adhered together.

This tape can be adhered between facing members of a closure, adjacent the edge of a facing member, but it is easy for the consumer to pry the facing members apart by inserting fingers between the sheet members in the unadhered area. Thus, a package is formed which incorporates the easy open feature of ears 23 and 24. This embodiment of tape provides a further advantage in reinforcing the facing members of the closure.

Use of the tape of FIG. 6 is shown in FIGS. 7 and 8. For the sake of clarity, the heat seal layers are omitted here, but it will be understood that sheets 101 and 102 are heat sealed to the end flaps 153 and 154 of the carton. The unadhered area between the sheet members is adjacent the exposed edge of the outer flap 153 so that fingers may be inserted there to start lifting that flap.

The sheet member 101 and conveniently the sheet member 102 as well is made of a relatively tear-resistant material. For example, it may be thin dense nonwoven fabric made of nylon or polyester fibers or a resin treated paper. Therefore, it reinforces the flap.

In a conventional carton in which the corresponding flaps are glued or heat sealed together, there is a tendency for the outer flap to tear when the carton is opened. Because of this, it has been necessary to make the flap of heavier or stronger cardboard. Since the carton usually is made from a single sheet of cardboard folded along score lines, the rest of the box is made of heavier cardboard than necessary. The tape embodiment of FIGS. 6-8 helps with this problem in two ways. First, it reinforces flap 153. Second, the finger space under the edge of flap 153 reduces the effort necessary to lift that flap by assuring a firm grip. Therefore, it eliminates a primary cause of tearing of ordinary boxes, i.e. the effort required to pry up the edge of the flap before starting to lift it.

It will be appreciated that the invention is applicable to closing many other kinds of packages. Therefore, while preferred embodiments have been described, it will be appreciated that changes may be made in details of construction and mode of operation without departing from the invention.

Claims

What is claimed is:

1. A package comprising a receptacle containing a commodity, and having a closure comprising a pair of facing members, a portion of each of said facing members being adhered to said portion of the other facing member by means of a tape,

said tape comprising a pair of sheet members facing each other,

pressure sensitive adhesive between said sheet members, bonding to each other the inner surfaces of said sheet members,

the outer surfaces of said sheet members being permanently bonded to the respective portions of said facing members with a bond strength greater than the bond strength between said sheet members,

whereby said package may be opened by separating said sheet members and reclosed with said pressure sensitive adhesive by pressing said sheet members together, without separating said sheet members from the respective facing members.

2. A package as set forth in claim 1 in which said permanent adhesive layers are activatable by heat.

3. A package as set forth in claim 1 in which one of said sheet members is a release paper from which said pressure-sensitive adhesive may be separated without delamination.

4. A package as set forth in claim 1 which is a pouch of flexible film, the said portions of said facing members being portions of said film.

5. A package as set forth in claim 4 in which said pouch is a tube of a single piece film, one pair of the edges of which are sealed together along a longitudinal seam, one end of said tube being permanently sealed and the other end being sealed with said tape.

6. A package as set forth in claim 5 in which the tape is sealed to said film a short space from the end of said tube, permitting insertion of fingers between the portions of said tube to which the tape is sealed to facilitate separation of said sheet members.

7. A package as set forth in claim 1 in which the package is a carton and said facing members are overlapping flaps.

8. A package comprising a receptacle containing a commodity, and having a closure comprising a pair of facing members, a portion of each of said facing members being adhered to said portion of the other facing member by means of a tape,

said tape comprising a pair of sheet members facing each other,

pressure-sensitive adhesive between a portion only of the inner surfaces of said sheet members, bonding to each other a portion only of the inner surfaces of said sheet members, and the portion of said inner surfaces adjacent an edge of one of said facing members being unadhered,

the outer surfaces of said sheet members being permanently bonded to the respective facing members with a bond strength greater than the bond strength between said sheet members,

whereby said package may be opened by separating said sheet members and reclosed with said pressure-sensitive adhesive by pressing said sheet members together, without separating said sheet members from the respective facing members, the unadhered area between said sheet members facilitating separating them and said sheet members reinforcing said facing members.

9. A package as set forth in claim 8 in which the package is a carton and said facing members are overlapping flaps.

10. A tape for sealing together facing members of package closure means,

said tape comprising a pair of sheet members facing each other,

pressure-sensitive adhesive between said sheet members, bonding to each other the inner surfaces of said sheet members,

and permanent adhesive layers on the outer surfaces of both of said sheet members, said permanent adhesive layers being permanently bondable to said facing members of said package closure means to form adhesive bonds stronger than the adhesive bond between said sheet members,

whereby said tape may be adhered permanently between the facing members of said package closure means without exposure of the pressure-sensitive adhesive to packaging machinery, and said package may be opened by separating said sheet members and reclosed with said pressure-sensitive adhesive by pressing them together, without breaking the bonds between said sheet members and the respective facing members.

11. A tape as set forth in claim 10 in which said permanent adhesive layers are activatable by heat.

12. A tape as set forth in claim 10 in which one of said sheet members is a release paper from which said pressure-sensitive adhesive may be separated without delamination.

13. A tape as set forth in claim 10 in which said pressure-sensitive adhesive is between a portion only of said sheet members, another portion thereof being unbonded.

14. A packaging material for manufacture of reclosable pouches, comprising a sheet material and, adhered to said sheet material at spaced points therealong a plurality of elongated tapes, said tape comprising a pair of sheet members facing each other, pressure-sensitive adhesive between said sheet members bonding to each other the inner surfaces of said sheet members, the outer surface of one of said sheet members being permanently bonded to said sheet material, the outer surface of the other of said sheet members being permanently bondable to said sheet material.

15. A packaging material as set forth in claim 14 in which the outer surface of said other sheet member is coated with a heat seal adhesive.