CA1289899C

CA1289899C - Package opening system

Info

Publication number: CA1289899C
Application number: CA 543219
Authority: CA
Inventors: Andrew D. Fraser
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1986-08-25
Filing date: 1987-07-29
Publication date: 1991-10-01
Anticipated expiration: 2008-10-01
Also published as: US4720423A; EP0257913A3; EP0257913A2; JPS6368878A

Abstract

ABSTRACT OF THE DISCLOSURE
A multilayer strip having an adhesive between layers, the adhesive containing frangible microcapsules carrying a fragrant liquid therein, can be used as a tear strip for a package overwrap. Upon pulling the outward layer of said strip, the overwrap is opened and the fragrance is released.

Description

PACKAGE OPENING SYSTEM

sACKGRoUND OF THE INVENTION
1. Field of the Invention The present invention relates to overwraps for packages and to systems that can be used to remove or open 10 said overwraps and release a predetermined fragrance.

2. Background of the Art Many different types of overwrap systems are used in the packaging of goods and materials. The most common 15 overwrap is a polymeric film which conforms to the shape of the wrapped package. The film tends to prevent the flow of air and moisture between the environment and the package, thus helping to maintain the freshness or activity of the material or article within the package. Overwraps can also 20 serve decorative functions and can therefore be made of paper which will not provide significant protection from the environment unless coated or otherwise treated to decrease its gas permeability.
Some overwraps are intended to ~e opened by 25 tearing of the overwrap material, loosenin~ secured areas of the wrap, or breaking a precut area in the overwrap. One common form of overwrap has an exposed string or strip which extends from underneath the overwrap but above the enclosed package. As the string or strip (usually referred to as a 30 tear strip) is pulled, usually at an angle greater than 90 from the surface of the overwrap, the tear strip will cut through the overwrap. After the strip is manipulated in this manner around the entire surface of the overwrap, a complete section of the overwrap is loosened or removed, and 35 the package is exposed for use.
Multilayer sheet materials are known which when separated rupture microcapsules in intermediate adhesive ~ .

layers and release fragrances stored within the microcapsules.
Examples of such systems are shown in United States Patents 4,487,801 and 4,606,956.
SUMMARY OF THE INVENTION
The invention provides an article having a wrapping material over it, said wrapping material having a tear strip associated therewith which when pulled is capable of tearing through said wrapping, said tear strip comprising two layers secured by an adhesive containing frangible microcapsules, said microcapsules having average diameters of between 3 and 180 microns and releasing a fragrance when broken.
The invention also provides an article comprising an interior article, an overwrap, and a tear strip for opening said overwrap having said tear strip secured by an adhesive layer to said interior article, the adhesive layer containing frangible microcapsules having average diameters of 3 to 180 microns and containing fragrance therein.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a perspective of a package 6 with an o~erwrap 4.
Figure 2 shows a section on an overwrap 4 over a package 6 and shows a tear strip 8 between the package 6 and over-wrap 4.
Figure 3 shows a side view of a package 6 with overwrap 4 and a tear strip 8 which has been partially removed.

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- 2a - 60557-3280 DETAILED DESCRIPTION OF THE DRAWINGS
Figure 1 shows a combined article 2 comprising a package 6 and an overwrap 4. The article 2 has a tear strip 8 located above the package 6 and below the overwrap 4. The over-wrap 4 has a notch 10 therein to facilitate initial tearing and opening of the overwrap 4 by the tear strip 8.
Figure 2 shows a section of an article 2 having a package 6, overwrap 4 and tear strip 8. The tear strip 8 is shown to comprise two layers, an outer layer 12 in contact with lC or towards the overwrap 4, and an inner layer 14 in contact with or towards the package 6. There is an adhesive layer (not shown) between the two strips which bears frangible microcapsules con-taining fragrance therein.

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Figure 3 sho~s a partially opened article 2 com-prising a package 6, overwrap 4 and teae strip 8. A portion 22 of the tear strip ~ has been pulled away from the package 6, and the inner layer 24 of the tear strip 8. The portion 5 _ constitutes a section of the outer layer of the tear strip 8. ~y pulling that portion 22 at an angle 16 which is perpendicular or greater than perpendicular (with respect to the surface of the package), the leading edge 26 of the portion cuts through the overwrap 4 leaving an opened 10 portion 20 of the overwrap 4 in its wake.

DETAILED DESCRIPTION OF THE INVENTION
The use of overwraps on packages can improve the appearance and maintain the quality of the materials or 15 article within the package. The use of a tear strip having the ability to release fragrance at the time of opening of the package can add further henefit to overwrap. The release of a controlled fragrance can give the impression to the user that the ingredients of the package are very fresh 20 and provides a generally pleasing enhancement of the product. This is a very important marketing point with respect to consumables. The impression of the consumer that a product is fresh is enhanced by the release of fragrance at the time of first opening the overwrap to gain access to 25 the package. This has been strongly shown in market studies.
The package may be made of any material and con-tain any type of article. Consumables such as candy, gum, cigarettes, dried fruit, snacks, cookies and otner foods are 30 used with particular advantage in the practice of the present invention. The package may be made of paper, card-boards, polymeric materials, coated paper, foil, composite structures, metallized paper or polymer, or any other packaging material.
The overwrap may be any tearable film or sheet material such as paper or polymeric film. Polymeric film -- . , - -- ~ -such as polyvinylidene chloride, polyolefins, cellulose acetate (and its esters), polyamides, vinyl resins, poly-esters and the like are preferred. Transparent films are generally preferred.
The layers of the tear strip may be composed of many different materials. A most important consideration of the materials with respect to the upper layer is that it must have sufficient tensile strength to be able to be pulled at an angle with respect to the package surface and 10 tear through the overwrap without breaking. Vseful mate-rials for either or both layers of the tear strip include polymeric film, paper, foil, and fabric. The layers of the tear strip may be of the same or different material.
A wide variety of processes exist by which 15 microcapsules can be manufactured. These varied processes provide different techniques for producing capsules of varying sizes, alternative materials for the composition of the capsule shell and various different functional materials within the shell. Some of these various processes are shown 20 in U.S. Patent Nos. 3,516,846; 3,516,9~1 and British Patent Specification Nos. 1,156,725; 2,041,319 and 2,048,206. A
wide variety of different materials may also be used in makinq the capsule shells. A popular material for shell formation is the polymerization reaction product between 25 urea and formaldehyde or malamine and formaldehyde, or the polycondensation products of monomeric or low molecular weight polymers of dimethylolurea or methylolated urea with aldehydes. A variety of capsule forming materials are disclosed, for example, in U.S. Patent Nos. 3,516,846 and 30 4,087,376 and British Patent Specification Nos. 2,006,709 and 2,062,570.
The adhesive material for the capsules must form a bond to the coated surfaces of the sheets which is stronger than the cohesive strength of the adhesive with the capsules 35 dispersed therein. Although it is generally desirable to have an adhesive, the absolute cohesive strength of which is .

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less than its adhesive strength to the coated surface of the coated paper cover sheets, this is not essential. When the capsules are included within the adhesive composition, the effective cohesive strength of the adhesive tends to be S reduced. Adhesives, which by themselves would cause the sheets to be damaged during separation, can be used in combination with capsules in the practice of the present invention because of lowered effective cohesive strength.
The capsules in the present invention may comprise any rupturable capsule containing an active ingredient therein.
The tensile rupture strength of the capsules must be such that the cohesive failure of the adhesive results in capsule breakage. It has also been found that the size of the capsules plays a role in the usefulness of capsules within rupturable sheets according to the practice of the present invention. Generally the capsules should have an average diameter between 4 and 150 microns and preferably between 12 and 50 microns when the capsule payload is between 80 and 90% by weight of the total capsule weight. It is highly 20 preferred that the capsules have an average diameter between 14 and 26 microns and it is most preferred that the capsules have a diameter between 15 and 25 microns. These dimensions play a surprisingly important role in the ability to control the percentage of rupture of capsules in the practice of the 25 present in~ention. With lower payloads ~e.g., 7Q-80~), the capsules should be larger to provide the necessary rupture strength. The broadest range of capsule size under any conditions would be about 3 to 180 microns, with 8 micron capsules used with a 90-95~ by weight payload. Six to fifty 30 micron capsules are generally preferred.
Any adhesive capable of bonding the label to another surface may be used in the exterior surface of one of said sheets. Typically, acrylate and polyurethane pressure-sensitive adhesives are used to bond the article to 35 another surface. Thermally softenable adhesives, such as . .

polyolefins, polyamides, ~nd polyesters are also particu-larly useful. Solvent-activatable adhesives (including water-activa~able adhesives) such as poly~vinyl alcohol), natural gums, acrylates and polyesters are also very useful.
Thus pressure-sensitive, heat activatable, or solvent acti-vatable adhesive can be used, as well as permanent adhesives coated on the exterior surface immediately before applica-tion of the fragrance emitting device. The fragrance releasing strip may also be otherwise secured into the 10 package and wrapping. For example, a one- or two-side coated adhesive tape may be placed between the strip and the package. A one-sided tape would adhere the inward facing layer to the wrapping material so that when the upper part of the element is pulled, the lower layer is restrained by 1~ its securement to the wrapping. A two-sided adhesive tape would secure the lower layer to the package or to the package and wrapper depending upon its width.
It is preferred that the tear strip comprise:
1) at least two sheets bound by an adhesive composition layer, 2) said adhesive composition layer containing microcapsules with said liquid within the shell of said microcapsules, and 3) said microcapsules having an average diameter between 4 and 80 micrometers, the cohesive strength of the adhesive composition layer being less than the strength of the bond between said adhesive composition and a face of said sheets, the tensile rupture strength of said microcapsules being less than the 30 cohesive strength of the adhesive composition, and the rupture force of said adhesive composition layer containing microcapsules at 50~ relative humidity being between at least 1 ounce per linear five-and-one-half inches and less than 45 ounces per linear five-and-one-half inches (greater 35 than 2.0 g/cm and less than 90 g/cm), at least one exterior surface of a sheet having an adhesive thereon. It is preferred that the rupture strength between the sheets exceeds 8.0 g/cm and is less than 80 g/cm and most preferably exceeds 16 g/cm and is less than 75 g/cm. The minimum strength at this ambient condition (e.g., 20C and 50% R.H.) is necessary to keep the sheets from falling apart from forces incurred during handling. This problem has fre~uently occurred in magazine inserts where coated paper was used. The maximum limit on the rupture strength is necessary to keep the paper from tearing (termed fiber pull or fiber rupture) before the adhesive and capsules rupture.
This would prevent release of the liquid from the capsules.
The adhesive strength of the exterior adhesive to substrates (especially printed coated paper) is preferably greater than the cohesive strength of the adhesive layer containing 15 microcapsules. Preferably, it is at least 10% greater in adherence than the rupture strength between the sheets.
This type of article~is generally applied to paper surfaces (and especially coated paper surfaces) and so it is pre-ferred that the strength of adherence of the exterior adhe-20 sive to paper is at least 10% greater than the rupture strength between the sheets. A "liquid" according to the present invention includes liquids with materials dissolved or dispersed therein (e.g., pigments) and gels which are capable of flowing under moderate pressure.
It is also desirable to have the construction resist the effects of variable ambient conditions. It is therefore desirable that rupture strength exceed 4.0 g/cm after storage at 120C and less than 1% R.H. for seventy-two hours. This test would be performed by storaqe in an oven, 30 removal to a neutral environment (e.g., sealed bag or jar) until the article is at room temperature, and then measuring the rupture strength. It is preferred that the rupture strength is at least 8.0 g/cm and most preferred that the rupture strength is at least 16 q/cm under those conditions.
35 The article must still display a rupture strength between 2 and 90 g/cm at 20 and 50% R . H .

- ~ -A number of methods have been found which enable these conditions to be met according to the present inven-tion. The use of viscosity increasing agents in the binder provides a more even coating and one that ruptures before fiber pull begins. The use of additional coatings over the coated paper which contain polymers different from the binder of the adhesive layer and which do not form a solu-tion or chemically bond to the binder of the adhesive layer provides a useful article according to the present inven-tion. The use of larger size capsules tends to weaken thecohesive strength of the adhesive composite and prevent fiber pull. The use of capsules which are not moisture sensitive in combination with these large capsules (e.g., greater than 30 microns and up to 95 microns) provides a 15 useful adhesive layer. Higher capsule-to-binder ratios reduce the cohesive strength of the adhesive, as does the addition of non-viscosity enhancing particulate fillers.
According to the preferred practice of the present invention, if the method uses coated paper surfaces, the 20 binder between the sheets contains viscosity increasers (viscofiers) in addition to the microcapsules. The use of viscofiers reduced the criticality of proportions of materials and provided increased coating and manufacturing latitude. Viscosity enhancers or viscosity increasing 25 agents are well known in the art. ~ny material which when present in the coating solution in an amount not greater than 10% by weight increases the viscosity by at least 5% is a viscofier according to the present invention. Preferably viscosity is increased by at least 20%. They are either 30 inorganic particulate materials (e.g., silica, amorphous silica, bentonite clay, montmorillonite clay, etc.3 or organic particulate or soluble materials (e.g., water soft-enable acrylic particles, water swellable poly(methylmeth-acrylate), water soluble or organic solvent soluble poly-35 mers, etc.). The inorganic particles tend to be preferred.The viscofiers enhancers have been found to be necessary in - -- ' :
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dry weight proportions of the adhesive mix in amounts of from 0.25 to 12% by weight, preferably from 5 to 12~ by weight. In general, the weight proportions of materials in the dried adhesive layers according to the present invention S are generally as follows:
Microcapsules 21 - 80%
Adhesive 19.75 - 70%
Viscosity Enhancers 0.25 - 12%

Other optional ingredients such as surfactants, coating aids and the like may be present. Preferred proportions of these ingredients are:
Microcapsules 44.5 - 80%
Adhesive 19.5 - 55~
Viscosity Enhancers 0.5 - 10%

The ability to use coated paper in the manufacture of these articles is important because those materials are the standard printing medium of the trade. Both one-side 20 coated paper and two-side coated paper are useful. Those papers enable highest quality printings to be made in com-bination with the releasahle materials of the present invention.
The nature and composition of the adhesive binder 25 is not critical to the practice of the invention as long as the required adhesive and cohesive properties are met. The adhesive may be pressure sensitive, water or solvent soluble or thermally activatable. A single layer of a non-pressure-sensitive adhesive is preferred. There is no need 30 for rejoining the sheets after rupturing of the capsules and so the pressure sensitive function is not necessary.
The adhesive (with microcapsules) may be applied between two separate sheets in either continuous or discon-tinuous patterns. It is usually desirable to leave at least 35 some portion of at least one outer edge of the sheets unbonded so as to provide an area where separation can be easily started. A single sheet may be folded so as to form two facing sheets joined along one edge. The adhesive may be applied on the interior area adjacent the fold. This provides a folded article that can be readily opened, rup-S turing the capsules, yet leaves a single artifact ratherthan two sheets after us.
It is preferred that the capsule-bearing adhesive coated inside portion between the sheets constitute from 60 to 95~ of the surface area of the sheets. In two sheet constructions, 10 to 95 percent adhesive coverage can be used to leave an edge or corner that can be readily grasped to pull one sheet from another. Some uses may allow for only a single corner to be uncoated so as to provide a starting point for the separation of the sheets, but the 60 15 to 95~ range is preferred with 70 to 90% preferred in two sheet constructions.
The tear strip may be partially separated at the end extending from beneath the overwrap. The inner layer may be held down while the upper layer is peeled away. The 20 side of the inner layer adjacent the package may also be adhered to the surface of the package. The upper layer of the tear strip may then be more easily peeled away. The facilitate this removal, the adherence of the inner layer of the tape should be greater than the rupture strength of the 25 two layers of the tear strip. The adhesive securement to the package may be by pressure-sensitive adhesive, solvent based adhesive, or thermally softenable adhesive.
Any class of adhesives including but not limited to polyurethanes, polyacrylates, polyvinyl resins ~e.g., 30 polyvinyl alcohol, polyvinyl chloride), polyamides, polyesters, polyolefins, starches, gum arabic, gelatin and the like may be readily used in the practice of the present invention. Washing of the capsules before mixing them with the adhesive often tends to provide more consistency in 35 their properties by removing low molecular weight, unreacted materials.

9~1 Any fragrance may be chosen to be included within the capsules. The fragrance should be chosen to enhance or blend with the fragrance of the package ingredients. For example, mint aroma could be used with a package of choco-late mints, menthol with menthol cigarettes, cinnamon withcinnamon toast, sandalwood with soap, and the like.

Example 1 Two sheets of 7.6 x 10 5 m polyester film were adhered together by an adhesive composition comprising 6q%
by weight of microcapsules, 24.5% by weight of polyvinyl alcohol (GelvatolR 40-10), 10.5% by weight polyvinyl alcohol (GelvatolR 2~-60), and 1% glycerin in water. The capsules were prepared from menthol oil in urea-aldehyde micro-capsules according to Example 10 of U.S. Patent 3,516,941.The adhesive was coated at a weight of 1.6 kg per 110 m2.
After drying, strips of 2 mm widths were cut from the sheet.
These strips were used in place of single sheet tear strips on packages of mentholated cigarettes. A coating of 20 pressure-sensitive adhesive was placed on the cigarette box in the region where the tear strip was to be applied, prior to packaging with a cellophane overwrap.
After wrapping with cellophane, the upper layer of the tear strip was pulled. The tear strip cut through the 25 overwrap and a strong aroma of menthol was released.

Example 2 A square segment of the material of Example 1 (2 x 2 cm) was cut from the adhered sheets. A small slice was 30 made between one edge to enable a single sheet to be grasped and a pressure-sensitive adhesive coated on one side of the sheet. A foil overwrapped box of dishwashing detergent was obtained and a small slit made in the foil over the pour spout. ~he square segment was inserted part way into the 35 slit, the adhesive coated face towards the spout. The upper sheet was grasped and pulled. The upper sheet tore through -lZ-the foil unwrapped and a strong fragrance o~ menthol was produced.

Example 3 A sheet was prepared identically as described in Example l except that one edge of the upper sheet extended beyond an edge of the lower sheet. A segment of this sheet including the overlapping edge was cut out. A pressure-sensitive adhesive was placed on the exterior surface of the lower sheet and on that portion of the overlapping upper sheet facing in the same direction as that face of the lower sheet. The segment was placed over a commercially available cigarette pack so that the coated portion of the upper sheet was adhered to the existing tear strip. Upon pulling the upper sheet away from the lower sheet, the menthol fragrance was emitted. Upon continued pulling of the upper sheet, the tear strip was engaged and the overwrap breached.
An alternative method of accomplishing a similar result would be to use a single sheet tear strip and apply a microcapsule bearing adhesive between said tear strip and the outer face of the inner package. This would form a tear strip that would rupture capsules when lifted from the sur-face of the container in a manner similar to that described in U.S. Patent 4,487,801.

Claims

1. An article comprising an interior article, an overwrap, and a tear strip for opening said overwrap, said tear strip having two layers of material selected from the group consisting of polymeric film and paper secured by an adhesive layer associated with said tear strip, said two layers being in the form of 1) a tab to engage said tear strip or

2) the tear strip itself, the adhesive layer of said two layers of material containing frangible microcapsules having average diameters between 3 and 180 microns containing fragrance therein.

2. The article of claim 1 wherein the tear strip itself comprises two layers of material secured by an adhesive layer to said interior article.

3. An article having a wrapping material over it, said wrapping material having a tear strip associated therewith which when pulled is capable of tearing through said wrapping, said tear strip comprising two layers secured by an adhesive containing frangible microcapsules, said microcapsules having average diameters of between 3 and 180 microns and releasing a fragrance when broken.

4. The article with a wrapping material over it of claim 3 wherein at least one of said two layers is a polymeric film.

5. The article having a wrapping material of any one of claims 1 to 4 wherein said tear strip is adhered to said article by an adhesive tape.

6. The article having a wrapping material of any one of claims 1 to 4 wherein said article is a package of cigarettes.

7. The article having a wrapping material of claim 5 wherein said article is a package of cigarettes.

8. The article having a wrapping material of any one of claims 1 to 4 wherein said wrapping material is a transparent film.

9. The article having a wrapping material of any one of claims 1 to 4 wherein said tear strip is adhered to said article by an adhesive tape.

10. An article comprising an interior article, an overwrap, and a tear strip for opening said overwrap having said tear strip secured by an adhesive layer to said interior article, the adhesive layer containing frangible microcapsules having average diameters of 3 to 180 microns and containing fragrance therein.